Biogen Inc. 225 Binney Street Cambridge, Massachusetts 02142, U.S.A

Biogen Inc. 225 Binney Street Cambridge, Massachusetts 02142, U.S.A.

Prospectus for the public offer

of up to 6,200,000 shares of Biogen Inc. common stock each with a par value of USD 0.0005 under the Biogen Inc. 2015 Employee Stock Purchase Plan

to the employees of the European Economic Area subsidiaries of Biogen Inc.

March 24, 2016

International Securities Identification Number (ISIN) US09062X1037 German Securities Code Number (Wertpapier-Kenn-Nummer) 789617 CUSIP Number: 09062X103

250065_1

TABLE OF CONTENTS

Prospektzusammenfassung 4

Abschnitt A – Einleitung und Warnhinweise ...... 4 Abschnitt B – Emittent ...... 4 Abschnitt C – Wertpapiere ...... 11 Abschnitt D – Risiken ...... 13 Abschnitt E – Das Angebot ...... 16 Prospectus Summary 22

Section A – Introduction and Warnings ...... 22 Section B – Issuer ...... 22 Section C – Securities ...... 28 Section D – Risks ...... 30 Section E – Offer ...... 32 Risk Factors 38

General Information 53

Responsibility for Contents of the Prospectus ...... 53 Subject Matter of the Offering ...... 53 Forward-Looking Statements ...... 53 Currency References ...... 53 Trademarks ...... 53 Documents Available for Inspection ...... 53 The Offering 55

Information Concerning the Shares to be Offered ...... 55 The Offering under the ESPP ...... 55 Reasons for the Offering and Use of Proceeds 60

Purpose of the ESPP ...... 60 Proceeds and Use of Proceeds ...... 60 Dilution 61

Dividend Policy 62

Capitalization 63

Capitalization and Indebtedness ...... 63 Working Capital Statement ...... 67 Selected Consolidated Financial Data 68

Legal and Arbitration Proceedings 70

Shareholdings and Stock Options of members of the administrative, management and supervisory bodies 73

General Information on Biogen 75

Company Name ...... 75 General Information on Biogen - and its Business ...... 75 Auditors ...... 77 Description of the securities 78

Type and the Class of the Securities being offered, including the Security Identification Code ...... 78 Stock Repurchase Programs ...... 78 Legislation under which the Securities have been Created / Regulation of the Shares ...... 78 Form of Securities, Name and Address of the Entity in Charge of Keeping the Records...... 79 Commission ...... 79 Currency of the Securities Issue ...... 79 Rights attached to the Securities ...... 79 Change of Shareholders’ Rights ...... 80 Transferability ...... 80 Applicable Squeeze-out and Sell-out Rules ...... 80 Share Based Compensation Plans ...... 80 Information on the Governing Bodies of Biogen 82

The Company’s Directors as of the date of this prospectus ...... 82 The Company’s Executive Officers as of the date of this prospectus ...... 84 Good Standing of Directors and Executive Officers ...... 86 Potential conflicts between any duties to the issuer of directors or executive officers of the Company and their private interests and/or other duties ...... 86 Disposal restrictions agreed by directors and executive officers of the Company...... 87 Taxation in the Federal Republic of Germany 88

Taxation in the United Kingdom 90

Taxation in France 93

Taxation in Denmark 96

Taxes on the Income from the Securities withheld at Source under US Federal Tax Laws 97

Recent Developments and Trend Information 98

Recent Developments since December 31, 2015 ...... 98 Trend Information ...... 98 Glossary/List of Defined Terms 102

Signature Page...... S-1

PROSPEKTZUSAMMENFASSUNG spe ktz Hinweis an den Leser usa Zusmmammenfassungen bestehen aus verschiedenen Offenlegungselementen, die als „Angaben“ bezeichnet werden.enf Diese Angaben sind unten in den Abschnitten A – E enthalten (A.1 – E.7). as- Diesesun Zusammenfassung enthält alle Angaben, die in einer Zusammenfassung für die angebotene Art von Wertpapiereng und diesen Emittenten erforderlich sind. Da bestimmte Angaben in der Zusammenfassung nicht enthalten sein müssen, können in der Nummerierung der Angaben Lücken auftreten. Hin Eswei kann vorkommen, dass im Hinblick auf eine bestimmte Angabe keine relevanten Informationen zur Verfügungs an gestellt werden können, obwohl die entsprechenden Informationen aufgrund der Art der ange- botenenden Wertpapiere und des Emittenten eigentlich zwingend in die Zusammenfassung aufzunehmen sind. InLe- einem solchen Fall wird die entsprechende Angabe in der Zusammenfassung mit der Bezeichnung „ent- fällt“ser und einer kurzen Begründung versehen.

AbschnittZu- A – Einleitung und Warnhinweise sam A.1men Einleitung und Warnhin- Diese Zusammenfassung sollte als Einführung zum Prospekt fas- weise verstanden werden. Der Anleger sollte jede Entscheidung zur sun Anlage in die Aktien auf die Prüfung des gesamten Prospektes gen stützen. Für den Fall, dass vor einem Gericht Ansprüche auf be- Grund der in diesem Prospekt enthaltenen Informationen gel- ste- tend gemacht werden, könnte der als Kläger auftretende Anle- hen ger in Anwendung der einzelstaatlichen Rechtsvorschriften der aus Staaten des Europäischen Wirtschaftsraums die Kosten für die ver- Übersetzung des Prospekts vor Prozessbeginn zu tragen haben. schi Diejenigen Personen, die die Verantwortung für die Zusam- ede- menfassung einschließlich etwaiger Übersetzungen übernom- de- men haben oder von denen der Erlass der Zusammenfassung nen ausgeht, können zivilrechtlich für den Inhalt der Zusammen- Of- fassung haftbar gemacht werden, jedoch nur für den Fall, dass fen- die Zusammenfassung irreführend, unrichtig oder wider- le- sprüchlich ist, wenn sie zusammen mit den anderen Teilen des gun Prospekts gelesen wird, oder sie, wenn sie zusammen mit den gsel anderen Teilen des Prospekts gelesen wird, nicht alle erforder- e- lichen Schlüsselinformationen vermittelt. men A.2ten, Verwendung des Prospekts Entfällt. Der Emittent hat der Verwendung des Prospekts für die für die spätere Weiterveräu- die spätere Weiterveräußerung oder endgültige Platzierung von als ßerung oder endgültige Plat- Wertpapieren nicht zugestimmt. „An zierung von Wertpapieren ga- durch Finanzintermediäre. ben “ Abschnittbe- B – Emittent zeic B.1hnet Juristische und kommerziel- Die juristische und kommerzielle Bezeichnung des Emittenten wer le Bezeichnung des Emitten- lautet Biogen Inc. In dieser Zusammenfassung beziehen sich den. ten Verweise auf „Biogen“ oder die „Gesellschaft“ auf die Biogen Die Inc. und ihre in den Konzernabschluss einbezogenen Tochterge- se sellschaften, sofern sich aus dem Zusammenhang nichts anderes An- ergibt. ga- benB.2 Sitz und Rechtsform des Biogen ist eine Kapitalgesellschaft. Der Hauptsitz der Biogen sind unten in 4 den Ab- sch

Emittenten, das für den befindet sich in 225 Binney Street, Cambridge, Massachusetts Emittenten geltende Recht 02142, USA. Die Gesellschaft wurde im Jahr 1985 nach dem und Land der Gründung der Recht des Staates Kalifornien gegründet und wurde im Jahr Gesellschaft 1997 zu einer Gesellschaft nach dem Recht des Staates Dela- ware. Im Jahr 2003 erwarb die Gesellschaft Biogen Inc. und änderte ihren Firmennamen von IDEC Pharmaceuticals Corpora- tion in Biogen Idec Inc. Mit Wirkung zum 23. März 2015 änder- te die Gesellschaft ihren Namen von Biogen Idec Inc. in Biogen Inc.

B.3 Art der derzeitigen Ge- Biogen ist ein weltweit im Bereich Biopharmazie tätiges Unter- schäftstätigkeit und Haupt- nehmen mit Fokus auf der Entdeckung, Entwicklung, Herstel- aktivitäten des Emittenten lung und Bereitstellung von Therapien an Patienten für die Be- sowie die Hauptmärkte, auf handlung von neurodegenerativen Erkrankungen, hämatologi- denen der Emittent tätig ist schen Krankheiten und Autoimmunerkrankungen. Ihre derzeit vermarkteten Produkte sind u.a. TECFIDERA, AVONEX, PLEGRIDY, TYSABRI und FAMPYRA gegen multiple Skle- rose („MS“), ELOCTATE gegen Hämophilie A, ALPROLIX gegen Hämophilie B und FUMADERM für die Behandlung von schwerer Plaque-Psoriasis. Die Gesellschaft hat auch eine Ko- operationsvereinbarung mit Genentech Inc:, eine hunderprozen- tige Tochtergesellschaft der Roche-Gruppe, die Biogen bestimmte geschäftliche und finanzielle Rechte bezüglich RITU- XAN zur Behandlung von Non-Hodgkin-Lymphomen, chronisch-lymphatischer Leukämie („CLL“) und anderen Erkran- kungen und GAZYVA, welches zur Behandlung von CLL und anderen potenziellen Anti-CD20 Therapien (Therapien gegen das Protein CD20, das auf der Oberfläche von Immunzellen vorkommt) eingesetzt wird, einräumt. Im Folgenden eine Zu- sammenfassung der vom Unternehmen vertriebenen Produkte: • TECFIDERA (Dimethylfumarat), Arzneimittel zur oralen Einnahme, in den Vereinigten Staaten von Amerika („USA“) angezeigt zur Behandlung von Patienten mit schubweise verlaufender MS und in der Europäischen Union („EU“) für Patienten mit schubweise-remittierender MS („RRMS“).

• AVONEX (Interferon beta-1a), ein intramuskulär injizierbares Arzneimittel, angezeigt zur Behandlung von Patienten mit schubweise verlaufender MS.

• PLEGRIDY (PegInterferon beta-1a), subkutan injizierbares Arzneimittel, in den USA angezeigt zur Behandlung von Patien- ten mit schubweise verlaufender MS und in der EU zur Behand- lung von Patienten mit RRMS.

• TYSABRI (Natalizumab), ein monoklonaler Antikörper, der in zahlreichen Ländern als Monotherapie zur Behandlung von Pa- tienten mit schubweise verlaufender MS zugelassen ist. TY- SABRI ist in den USA zudem zur Behandlung von Morbus Crohn, einer entzündlichen Erkrankung des Darms, zugelassen.

• FAMPYRA (retardiert freigesetzte Fampridintabletten) ist zur Verbesserung der Gehfähigkeit bei erwachsenen MS-Patienten angezeigt. Die Gesellschaft verfügt über eine Lizenz von A- corda Therapeutics, Inc. zur Entwicklung und wirtschaftlichen Verwertung von FAMPYRA auf allen Märkten außerhalb der

USA.

• ELOCTATE (Blutgerinnungsfaktor (gentechnisch hergestellt) Fc-Fusionsprotein), ein rekombinant hergestellter Gerinnungs- faktor, in den USA angezeigt zur Behandlung von Hämophilie A bei Erwachsenen und Kindern zur Kontrolle und Bekämpfung von Blutungen.

• ALPROLIX (Gerinnungsfaktor IX (gentechnisch hergestellt) Fc- Fusionsprotein), ein rekombinant hergestelltes Konzentrat des Gerinnungsfaktors IX, in den USA angezeigt zur Behandlung von Hämophilie B bei Erwachsenen und Kindern zur Kontrolle und Bekämpfung von Blutungen.

• RITUXAN (Rituximab), ein häufig verordneter monoklonaler Antikörper zur Behandlung von Non-Hodgkin-Lymphomen, rheumatoider Arthritis, CLL und zweier Formen anti- neutrophiler cytoplasmatischer Antikörper (antineutrophil cytoplasmatic antibodies; -ANCA)-assozierter Vaskulitis. • GAZYVA (Obinutuzumab) ist eine Kombination mit dem Wirkstoff Chlorambucil (Leukeran) und angezeigt für die Be- handlung von Patienten mit vormals unbehandelter CLL. Die Hauptmärkte für das Geschäft von Biogen sind die Verei- nigten Staaten von Amerika, Europa (ohne Deutschland), Deutschland, Asien und sonstige mit Umsatzanteilen von jeweils ca. 71 %, 16 %, 7 %, 2 % und 4 % der Verkaufserlöse des Jahres 2015 zum 31. Dezember 2015. Die Gesellschaft unterstützt ihre Medikamentenforschung und - entwicklung durch die Abstellung wesentlicher Ressourcen für Forschungs- und Entwicklungsprogramme sowie für Gelegen- heiten zur Geschäftsentwicklung, insbesondere in den Berei- chen, in denen die Gesellschaft über wissenschaftliche, ferti- gungstechnische und technische Expertise verfügt sowie be- nachbarten wissenschaftlichen Fachgebieten. Zusätzlich zu ihren Bemühungen im Rahmen der innovativen Medikamentenentwicklung beabsichtigt die Gesellschaft, ihre Produktionskapazitäten und wissenschaftliche Expertise aus- zuweiten, um ihre Mission, das Leben von Patienten mit schwe- ren Erkrankungen zu verbessern, durch die Entwicklung, Her- stellung und Vermarktung von Biosimilarprodukten durch Samsung Bioepis, ihr Joint Venture mit Samsung BioLogics Co. Ltd. („Samsung Biologics“) voranzubringen. Im Januar 2016 hat die Europäische Kommission (die „Kommission“) die Marktzulassung für die Vermarktung in der EU von BENEPA- LI, ein etanerceptisches Biosimilar-Produkt mit Referenzierung zu ENBREL, erteilt. Auf Basis der Vereinbarung der Gesell- schaft mit Samsung Bioepis wird Biogen BENEPALI in bestimmten EU-Ländern herstellen und vermarkten. Im Rahmen ihrer Geschäftsstrategie hat Biogen verschiedene Kooperationsverträge geschlossen, durch die sie über Rechte zur Entwicklung, Herstellung und Vermarktung von Produkten verfügt, für die Know-How, Technologien und Patentrechte eingesetzt werden, die von ihren Kooperationspartnern gehalten werden. Die Bestimmungen der verschiedenen Kooperations-

verträge können vorsehen, dass die Gesellschaft bei Erreichen bestimmter Produktforschungs- und -entwicklungsziele Ab- schlagszahlungen leisten und ggf. auf zukünftige Umsätze von kommerziellen Produkten in Zusammenhang mit der Koopera- tion Lizenzgebühren zahlen muss. Patente sind für den Erhalt und Schutz exklusiver Rechte an den Produkten und Produktkandidaten der Gesellschaft von großer Bedeutung. Zudem können regulatorische Exklusivität, wie etwa regulatorischer Datenschutz und Marktschutz für die Pro- dukte der Gesellschaft bedeutende Schutzmechanismen darstel- len. Die Gesellschaft beansprucht für Erfindungen, die aus ihrer Forschungs- und Entwicklungstätigkeit stammen, regelmäßig Patent- und regulatorischen Schutz in den USA und in ausge- wählten Ländern außerhalb der USA. Die Marken der Gesellschaft sind wichtig für das Unternehmen und in der Regel beim Patentamt der Vereinigten Staaten (Uni- ted States Patent and Trademark Office, „USPTO“) sowie bei den Patent- oder Markenämtern anderer Länder zur Registrie- rung angemeldet bzw. dort registriert. Die derzeitigen und die ins Auge gefassten Aktivitäten der Ge- sellschaft sowie die aus diesen Aktivitäten resultierenden Pro- dukte, Technologien und Verfahren sowie Umsatz, Marketing, Preisgestaltung und Erstattungen unterliegen in erheblichem Maß der staatlichen Regulierung.

B.4a Wichtigste jüngste Trends Die aktuellen Erlöse der Gesellschaft hängen vom weiteren mit Auswirkung auf den Verkauf ihrer Hauptprodukte ab. Die Gesellschaft ist möglich- Emittenten und seine Bran- erweise für viele Jahre wesentlich vom Verkauf ihrer Hauptpro- che dukte abhängig; insbesondere zu erwarten ist dies im Hinblick auf den Verkauf von TECFIDERA, für das die Gesellschaft weiter in neue Märkte expandiert. Der Absatz von Produkten von Biogen ist zu einem wesentlichen Teil von ausreichender Versicherungsdeckung, den Preisfestlegungsverfahren sowie der Erstattung durch Dritte abhängig, die ihrerseits immer stärker hartem Druck seitens der Politik, der Gesellschaft, ihrer Wett- bewerber und sonstiger Stellen ausgesetzt sind. Die Biopharmaindustrie und die Märkte, in denen die Gesell- schaft tätig ist, sind einem starken Wettbewerb ausgesetzt. Viele Wettbewerber der Gesellschaft arbeiten an der Entwicklung von Produkten oder haben Produkte auf den Markt gebracht, die den bestehenden Produkten der Gesellschaft ähneln oder an deren Entwicklung sie derzeit arbeiten. Darüber hinaus kann die Ver- marktung bestimmter eigener zugelassener MS-Produkte, die MS Produkte von Kooperationspartnern der Gesellschaft und Produktkandidaten aus der Pipeline negative Auswirkungen auf den zukünftigen Umsatz mit ihren bestehenden MS-Produkten haben. Zudem können die Produkte der Gesellschaft durch das Aufkommen generischer Versionen, Prodrug-Produkten von anderen Therapeutika oder Biosimilars von bestehenden Pro- dukten und andere Technologien, wie etwa Gentherapien, zu- nehmend unter Wettbewerbsdruck geraten. Längerfristig betrachtet ist das Einnahmenwachstum der Gesell- schaft abhängig von der erfolgreichen klinischen Entwicklung, der Zulassung und der Einführung neuer kommerzieller Produk-

te sowie zusätzlichen Indikationen für die bestehenden Produkte der Gesellschaft, der Fähigkeit der Gesellschaft, Patente und andere mit ihren vermarkteten Produkten verbundene Rechte sowie durch ihre Forschungs- und Entwicklungsarbeiten ent- standene Vermögenswerte zu erlangen und aufrechtzuerhalten sowie von der erfolgreichen Durchführung von unternehmens- externen geschäftlichen Entwicklungsmöglichkeiten. Im Rah- men ihrer laufenden Forschungs- und Entwicklungstätigkeit beabsichtigt die Gesellschaft, weiterhin in erheblichem Umfang gezielt Mittel in Forschung- und Entwicklungsmöglichkeiten bereitzustellen soweit es einen wichtigen noch nicht gedeckten Bedarf gibt und der potenzielle Wirkstoff das Potential hat, hoch differenziert zu sein. Insbesondere beabsichtigt die Gesll- schaft, weiterhin in ihre MS Pipeline, ihre Programme zur Be- handlung der Alzheimer Erkrankung (aducanumab, BAN2401 und E2609), das Nusinersen Programm zur Behandlung von Spinaler Muskelatrophie, das Amiselimod Programm zur Ent- wicklung von Produktkandidaten für multiple Autoimmuner- krankungen und ihr Raxatrigine Programm zur Entwicklung von Produktkandidaten gegen neuropathische Schmerzen zu investieren.

B.5 Beschreibung der Gruppe Entfällt, da bezüglich der Organisationsstruktur von Biogen und Stellung des Emittenten keine Informationen in diesem Prospekt enthalten sein müssen. innerhalb der Gruppe B.6 Darstellung der Beteiligun- Entfällt, da bezüglich der Beteiligungen am Kapital von Biogen gen am Kapital der Gesell- keine Informationen in diesem Prospekt enthalten sein müssen. schaft B.7 Ausgewählte Finanzinfor- Die nachfolgend dargestellten ausgewählten Finanzdaten sind mationen bezüglich Biogen aus den geprüften Konzernabschlüssen der Gesellschaft für die und erhebliche nachfolgende zum 31. Dezember 2015, 31. Dezember 2014 und 31. Dezember Veränderungen 2013 endenden Geschäftsjahre, wie diese im Jahresbericht (An- nual Report) der Gesellschaft auf Formular 10-K für das zum 31. Dezember 2015 endende Geschäftsjahr veröffentlicht wurden, entnommen. Diese Dokumente können wie im Abschnitt „Verfügbare Unterlagen“ („Documents Available for Inspec- tion“) dieses Prospekts beschrieben, eingesehen werden. Die geprüften Konzernabschlüsse der Gesellschaft wurden in Über- einstimmung mit den in den Vereinigten Staaten von Amerika allgemein anerkannten Grundsätzen ordnungsgemäßer Buchfüh- rung („U.S.-GAAP“) erstellt.

AUSGEWÄHLTE KONZERNFINANZDATEN FÜR EI- NEN ZEITRAUM VON DREI JAHREN (in Millionen, außer für Werte, die „pro Aktie“ angegeben werden)

Für die zum 31. Dezember endenden Geschäftsjahre

2015(3) (4) 2014 2013(1) (2) Betriebsergebnisse Verkaufserlöse $ 9.188,5 $ 8.203,4 $ 5.542,3

Erlöse aus nicht konsolidier- ten Gemeinschaftsunterneh- 1.339,2 1.195,4 1.126,0 men Andere Erlöse 236,1 304,5 263,9 Gesamterlöse 10.763,8 9.703,3 6.932,2 Gesamtsumme Kosten und 5.872,8 5.747,7 4.441,6 Aufwendungen Gewinn aus Verkauf von — 16,8 24,9 Rechten Betriebsgewinn 4.891,0 3.972,4 2.515,5 Andere Einnahmen (123,7 ) (25,8 ) (34,9 ) (Aufwendungen) Einnahmen vor Einkom- menssteueraufwand und An- teil an Fehlbetrag einer Be- teiligung vor Steuern 4.767,3 3.946,6 2.480,6

Aufwand Einkommenssteuer 1.161,6 989,9 601,0

Anteil an Fehlbetrag einer 12,5 15,1 17,2 Beteiligung nach Steuern Nettoeinnahmen 3.593,2 2.941,6 1.862,3 Nettoeinnahmen (Nettover- 46,2 6,8 — luste), die auf Minderheits- beteiligungen entfallen, nach Steuern

Auf Biogen Inc. entfallende $ 3.547,0 $ 2.934,8 $ 1.862,3 Nettoeinnahmen

Verwässertes Ergebnis pro Aktie Auf Biogen Inc. entfallendes verwässertes Ergebnis pro Aktie 15,34 12,37 7,81

Auf Biogen Inc. entfallende gewichtete Durchschnittszahl bei der Berechnung des ve- wässerten Ergebnisses pro Aktie 231,2 237,2 238,3

Zum 31. Dezember

2015(5) (6) 2014 2013 Konzernbilanzdaten Zahlungsmittel, Zahlungs- mitteläquivalente und bör- senfähige Wertpapiere $ 6.188,9 $ 3.316,0 $ 1.848,5

Bilanzsumme $19 .504,8 $ 14.314,7 $ 11,863.3 7 Verbindlichkeiten aus Schuldverschreibungen, Kreditlinie und sonstige Fi- $ 6.521,5 $ 580,3 $ 592,4 nanzierungsvereinbarungen, abzüglich kurzfristiger Ver- bindlichkeiten Gesamteigenkapital Biogen $ 9.372,8 $ 10.809,0 $ 8.620,2 Inc.

(1) Der Anteil der Gesellschaft aus dem Erlös aus nicht konsolidier- ten Gemeinschaftsunternehmen berücksichtigt Kosten von USD 49,7 Mio. im Jahr 2013 für Entschädigungszahlungen ein- schließlich Zinsen, die Hoechst im Zusammenhang mit dem Schiedsverfahren gegen Genentech wegen RITUXAN zugespro- chen wurden.

(2) Mit Beginn des zweiten Quartals 2013 enthalten die Arzneimit- telerlöse und die Gesamterlöse zu hundert Prozent die Nettoerlö- se aus dem Verkauf von TYSABRI aufgrund des Erwerbs aller verbleibenden TYSABRI-Rechte von Elan Pharma International, Ltd., ein verbundenes Unternehmen der Elan Corporation plc. Zum Closing wurde der Kooperationsvertrag der Gesellschaft beendet, so dass die Gesellschaft keine Gewinnbeteiligung aus der Kooperation mehr berücksichtigt. Die Gesellschaft hat einen Aufwand aus Kooperations-Gewinnbeteiligung in Höhe von $85,4 Millionen während des zum 31. Dezember 2013 endenden Jahres verbucht. Zusätzlich beinhalten Produkt- und Gesamterlö- se Nettoerlöse aus Verkäufen des Produkts TECFIDERA.

(3) Andere Erlöse spiegeln einen Rückgang von Lizenzerlösen aufgrund des Auslaufens von US Patenten im Dezember 2014 die für Lizenzerlöse bezüglich des Produkts ANGIOMAX gesorgt hatten, wider.

(4) In Gesamtsumme Kosten und Aufwendungen enthalten sind Restrukturierungsaufwendungen in Höhe von $93,4 Millionen, die im Zusammenhang mit der Restrukturierung der Gesell- schaft, die am 21. Oktober 2015 bekanntgegeben wurde, entstan- den sind; die Restrukturierung umfasste unter anderem die Been- digung von bestimmten Entwicklungsprogrammen und eine Re- duzierung der Belegschaft um 11%.

(5) Verbindlichkeiten aus Schuldverschreibungen, Kreditlinie und sonstige Finanzierungsvereinbarungen, abzüglich kurzfristiger Verbindlichkeiten spiegeln die Begebung der unbesicherten An- leihe der Gesellschaft mit einem Gesamtnennbetrag von $6 Mrd. am 15. September 2015 wider.

(6) Das Gesamteigenkapital Biogen Inc. spiegelt eine Verringerung des zusätzlichen eingezahlten Kapitals und der Gewinnrücklagen

um insgesant $ 5 Mrd. wider, die aus dem Rückkauf eigener Ak- tien unter dem 2015 Aktienrückkaufprogramm der Gesellschaft resultieren.

Seit dem 31. Dezember 2015 haben sich Finanzlage und Han- delsposition der Gesellschaft nicht wesentlich geändert.

B.8 Pro Forma Finanzinforma- Entfällt, da keine historischen Finanzinformationen in diesem tionen Prospekt enthalten sein müssen. B.9 Gewinnprognose Entfällt. Dieser Prospekt enthält keine Gewinnprognose.

B.10 Beschränkungen im Bestäti- Entfällt. Es gibt keine entsprechenden Beschränkungen im Be- gungsvermerk zu den histo- stätigungsvermerk. rischen Finanzinformatio- nen

B.11 Erklärung zum Geschäfts- Biogen geht davon aus, dass ihr Geschäftskapital (d.h., ihre Fä- kapital higkeit, auf Barmittel und andere verfügbare Liquiditätsquellen zuzugreifen) ihren derzeitigen Bedarf für mindestens 12 Monate ab dem Datum dieses Prospekts deckt.

Abschnitt C – Wertpapiere

C.1 Beschreibung von Art und Bei den im Rahmen des Mitarbeiteraktienkaufplans 2015 der Gattung der angebotenen Biogen Inc. (Biogen Inc. Employee Stock Purchase Plan Wertpapiere, einschließlich („ESPP“)) angebotenen Aktien handelt es sich um Stammaktien der Wertpapieridentifikati- von Biogen im Nennwert von jeweils USD 0,0005 pro Aktie. onsnummer Die Stammaktien der Gesellschaft sind am NASDAQ Global Select Market („NASDAQ“) unter dem Kürzel „BIIB“ zum Handel zugelassen. Die US-Wertpapieridentifikationsnummer („CUSIP“) der Aktien lautet 09062X103. Die internationale Wertpapieridentifikationsnummer (International Securities Iden- tification Number (ISIN)) für die Gesellschaft lautet US09062X1037. Die deutsche Wertpapier-Kenn-Nummer lautet 789617. C.2 Währung der Wertpa- Die Wertpapiere werden in US-Dollar ausgegeben. pieremission C.3 Anzahl der ausgegebenen In Umlauf befindliche und ausgegebene Stammaktien zum Aktien 31. Dezember 2015: 218.667.750, jeweils im Nennwert von USD 0,0005.

C.4. Beschreibung der mit den Ein Teilnahmeberechtigter Mitarbeiter (Definition siehe unten Wertpapieren verbundenen in Abschnitt E.3) der am ESPP teilnimmt, hat so lange keine Rechte Stimm-, Dividenden- oder anderen Aktionärsrechte im Hinblick auf ein Angebot nach Maßgabe des ESPP, bis die Aktien im Rahmen des ESPP im Auftrag des Teilnehmers (Definition siehe unten in Abschnitt E.3) gekauft wurden und der Teilnehmer Aktionär der gekauften Aktien ist. Nach dem Kauf ist der am ESPP teilnehmende Teilnahmeberechtigte Mitarbeiter befugt, die mit den Aktien verbundenen Rechte wie nachfolgend beschrieben auszuüben: Dividendenrechte. Der Verwaltungsrat kann auf jeder ordentli-

chen oder außerordentlichen Sitzung eine Dividende aus den gesetzlich dazu zur Verfügung stehenden Mitteln beschließen. Der Verwaltungsrat bestimmt das Nachweisdatum (Record Date) und das Auszahlungsdatum für Dividendenzahlungen. Dividenden können als Bar- oder Sachdividende oder in Aktien der Gesellschaft ausbezahlt werden. Ein zum Stichtag für die Dividendenerklärung eingetragener Aktionär hat zu diesem Stichtag ein geltendes Anwartschaftsrecht auf die Dividende, darf aber bis zum Auszahlungsdatum nicht versuchen, dieses Recht durchzusetzen. Nicht innerhalb von drei Jahren durchge- setzte Ansprüche auf Dividendenzahlung fallen grundsätzlich dem Staat von Delaware zu. Bislang hat Biogen jedoch keine Bardividenden gezahlt und beabsichtigt dies gegenwärtig auch nicht. Für in der EU und im Europäischen Wirtschaftsraum wohnhafte Aktionäre bestehen keine Dividendenbeschränkungen und keine besonderen Ver- fahren. Stimmrechte. Stammaktionäre haben pro Aktie eine Stimme und können über alle die Aktionäre betreffenden Angelegenheiten abstimmen. Alle Maßnahmen, die von Aktionären vorgenom- men werden müssen oder für die die Zustimmung der Aktionäre angefordert wird, können in der ordnungsgemäß einberufenen ordentlichen (jährlichen) Hauptversammlung, in einer ord- nungsgemäß einberufenen außerordentlichen Hauptversamm- lung oder im schriftlichen Verfahren von den Aktionären vor- genommen werden. Außerordentliche Versammlungen der Ak- tionäre der Gesellschaft können aufgrund einer Einberufung durch den Verwaltungsratsvorsitzenden, den Chief Executive Officer, durch den Verwaltungsrat der Gesellschaft, oder in Übereinstimmung mit der Satzung (bylaws) der Gesellschaft durch Inhaber von mindesten 25% der Aktien der Gesellschaft abgehalten werden. Recht auf Liquidationserlöse. Im Fall der Liquidation, Auflö- sung oder Abwicklung der Gesellschaft, sind die Stammaktionä- re berechtigt, nach Abzug aller Zahlungen auf Verbindlichkei- ten oder Rückstellungen, vorbehaltlich vorrangiger Rechte oder Vorzugsaktien, soweit ausgegeben, anteilig an den Vermögens- gegenständen der Gesellschaft beteiligt zu werden. Keine Bezugs-, Einziehungs-, Gewinnbeteiligungs- oder Wand- lungsrechte. Die Stammaktionäre der Gesellschaft haben keine Bezugsrechte im Hinblick auf den Erwerb von Aktien der Ge- sellschaft oder von in Aktien der Gesellschaft wandelbaren In- strumenten. Die Stammaktien der Gesellschaft unterliegen nicht der Einziehung, gewähren kein Recht auf Beteiligung am Ge- winn der Gesellschaft und keine Wandlungsrechte.

C.5 Übertragbarkeit Das Angebot zum Bezug von Aktien im Rahmen des ESPP wurde in den Vereinigten Staaten per Registrierungserklärung auf Formblatt S-8 bei der Securities and Exchange Commission der Vereinigten Staaten von Amerika („SEC“) registriert. Die ausgegebenen und im Umlauf befindlichen Stammaktien sind grundsätzlich frei übertragbar. Der Zweck des ESPP ist es, Aktien als Investitionsobjekt aus- zugeben. Es ist jedoch nicht die Absicht der Gesellschaft, in die

Angelegenheiten ihrer Mitarbeiter einzugreifen oder diese ein- zuschränken. Daher bleibt es den Teilnehmern überlassen, in Übereinstimmung mit den anwendbaren Wertpapiergesetzen, Richtlinien zum Insiderhandel sowie den anwendbaren Han- delssperrzeiten und den Bestimmungen des ESPP Aktien, die im Rahmen des ESPP gekauft wurden, jederzeit wieder zu ver- kaufen. Der Teilnehmer trägt die Risiken von Marktschwan- kungen, die sich im Preis der Aktien abbilden können.

C.6 Zulassung zum Handel an Entfällt. Die Stammaktien der Gesellschaft sind am NASDAQ einem geregelten Markt unter dem Kürzel „BIIB“ zum Handel zugelassen. Die Aktie wird am NASDAQ in US-Dollar gehandelt. In Deutschland werden die Aktien im Freiverkehr an den Börsen Frankfurt, Stuttgart, Berlin, Düsseldorf, Hamburg und München sowie auf Tradegate unter dem Kürzel „IDP“ gehandelt.

C.7 Dividendenpolitik Seit Gründung von Biogen wurden keine Dividenden beschlos- sen oder gezahlt und die Gesellschaft hat derzeit auch nicht die Absicht, Dividenden zu beschließen oder zu zahlen.

Abschnitt D – Risiken

Mitarbeiter sollten vor ihrer Anlageentscheidung die nachfolgend beschriebenen Risiken, die im Abschnitt „Risikofaktoren“ (Risk Factors) näher beschrieben sind, und die übrigen in diesem Prospekt enthaltenen Informationen sorgfältig lesen und bei ihrer Anlageentscheidung berücksichtigen. Der Eintritt dieser Risi- ken kann, einzeln oder zusammen mit anderen Umständen, die Geschäftstätigkeit und die Finanzlage der Gesellschaft wesentlich beeinträchtigen und dazu führen, dass der Börsenkurs der Aktien der Gesellschaft fällt. In diesem Fall könnten Mitarbeiter ihr eingesetztes Kapital ganz oder teilweise verlieren. Der Pros- pekt enthält alle Risiken, die die Gesellschaft für wesentlich erachtet. Allerdings könnten sich die nachfolgend aufgeführten Risiken rückwirkend betrachtet als nicht abschließend herausstellen und daher nicht die einzigen Risiken sein, denen die Gesellschaft ausgesetzt ist. Weitere Risiken könnten die Geschäftstätig- keit und die Finanzlage der Gesellschaft beeinträchtigen. Die gewählte Reihenfolge der Risikofaktoren enthält weder eine Aussage über die Eintrittswahrscheinlichkeit noch über das Ausmaß bzw. die Bedeu- tung der einzelnen Risiken.

D.1 Risiken im Hinblick auf Bi-  Der Erfolg der Biogen hängt maßgeblich von den Erlösen ogen oder ihr Branchenum- ab, die mit den Hauptprodukten des Unternehmens erzielt feld werden.  Gelingt es Biogen nicht, sich im Markt gegen Wettbewer- ber durchzusetzen, werden ihre Geschäftstätigkeit und Marktposition in Mitleidenschaft gezogen.  Der Absatz von Produkten von Biogen ist zu einem wesentlichen Teil von ausreichender Versicherungsdeckung, den Preisfestlegungsverfahren sowie der Erstattung durch Dritte abhängig, die ihrerseits immer stärker hartem Druck seitens der Politik, der Gesellschaft, ihrer Wettbewerber und sonstiger Stellen ausgesetzt sind. Gelingt es der Gesellschaft nicht, ausreichende Versicherungsdeckung durchzusetzen oder sinken die Preise bzw. die Erstattungen, könnte dies negative Auswirkungen auf das Geschäft, die Umsätze und das Betriebsergebnis haben und dazu führen, dass der Akti- enkurs der Gesellschaft an der Börse an Wert verliert.  Biogens Betriebsergebnis kann nachteilig durch gegenwär- tige oder mögliche zukünftige Gesundheitsreformen beein-

flusst werden.  Nachteilige sicherheitsrelevante Ereignisse, Auflagen im Hinblick auf Verwendung sowie Sicherheitswarnungen in Bezug auf die Produkte von Biogen können negative Aus- wirkungen auf das Geschäft, den Absatz und den Aktien- kurs von Biogen haben.  Gelingt es Biogen nicht, einen angemessenen Schutz für ihre Rechte an Informationen, Geistigem Eigentum und sonstigen Eigentumsrechte zu erwirken und aufrechtzuerhalten, könnte ihr Geschäft Schaden nehmen.  Der langfristige Erfolg von Biogen hängt von der erfolgreichen Entwicklung neuer Produkte und zusätzlichen Indika- tionen für bestehende Produkte ab.  Bei klinischen Studien und der Entwicklung biopharmazeu- tischer Produkte handelt es sich um langwierige und kom- plizierte Verfahren. Gelingt es Biogen nicht, ihre klinischen Aktivitäten angemessen zu steuern, könnten ihre klinische Studien verzögert bzw. ggf. erforderliche aufsichtsbehördli- che Zulassungen verweigert werden.  Erfolgreiche präklinische Arbeiten bzw. erste klinische Studien garantieren nicht den Erfolg in einer klinischen Studie der späteren Phase oder die aufsichtsrechtliche Zu- lassung bzw. kommerzielle Rentabilität eines Produkts.  Bei der Herstellung auftretende Probleme könnten die Aufwendungen der Gesellschaft beträchtlich erhöhen und dazu führen, dass ihre Produkte nur eingeschränkt zur Ver- fügung stehen und die Umsatzerlöse zurückgehen.  Biogen ist im Rahmen der Erzielung von Erlösen und bei der Entwicklung, der Vermarktung und dem Vertrieb bestimmter Produkte auf Geschäftsbeziehungen mit Partnern und anderen Dritten angewiesen, die die Gesellschaft nicht vollständig kontrolliert.  Die Gesellschaft könnte die mit ihrer Restrukturierung verfolgten finanziellen und operativen Ziele nicht erreichen und die Restrukturierung könnte sich negativ auf ihr Ge- schäft und ihr finanzielles Ergebnis auswirken.  Wenn es Biogen nicht gelingt, ihr derzeitiges Wachstum zu steuern und ihre Wachstumsinitiativen erfolgreich durchzu- führen, könnte sich dies nachteilig auf ihr Geschäft auswirken.  Durch einen Ausfall oder eine Verletzung der Technologie- systeme von Biogen könnte die Gesellschaft einer Haftung ausgesetzt sein oder ihren Geschäftsbetrieb unterbrechen müssen.  Versäumt es Biogen, die für die Gesundheitsbranche gel- tenden umfangreichen aufsichtsrechtlichen Anforderungen zu erfüllen, könnten der Gesellschaft zusätzliche Kosten entstehen. Es könnte ferner zur Zahlung von Bußgeldern und zu Geschäftsausfällen kommen.  Der Verschuldungsgrad der Gesellschaft könnte sich nachteilig auf das Geschäft der Gesellschaft auswirken und die Möglichkeiten der Gesellschaft beschränken, Änderungen

in der Geschäftstätigkeit der Gesellschaft zu planen oder auf solche Änderungen zu reagieren.  Die Umsätze und der Geschäftsbetrieb der Gesellschaft unterliegen den mit einer internationalen Geschäftstätigkeit einhergehenden Risiken.  Die effektive Steuerquote von Biogen kann erheblich schwanken und es könnten für die Gesellschaft Steuerver- bindlichkeiten anfallen, die über die gebildeten Steuerrück- stellungen hinausgehen.  Die operativen Ergebnisse von Biogen unterliegen erheblichen Schwankungen.  Biogen verfolgt Möglichkeiten der Ausweitung der Produk- tionskapazität für den zukünftigen klinischen und kommerziellen Bedarf von Produktkandidaten, was zu erheblichen Investitionen führen wird, ohne dass garantiert ist, dass die Investitionen sich amortisieren.  Das Investment der Gesellschaft in Samsung Bioepis und ihr Erfolg bei der Vermarktung von Biosimilar-Produkten, die von Samsung Bioepis entwickelt werden, unterliegen Risiken und Unsicherheiten, die der Entwicklung, Herstel- lung und Vermarktung von Biosimilar-Produkten inhärent sind.  Biogens Investitionen in Anlagegüter könnten sich nicht auszahlen.  Biogen hält ein Portfolio von marktgängigen Wertpapieren, und dessen Wert unterliegt Markt-, Zins- und Kreditrisiken, die seinen Wert verringern könnten.  Biogen könnte nicht in der Lage sein, Zugang zu den Kapi- tal- und Kreditmärkten zu für die Gesellschaft günstigen Bedingungen zu erhalten.  Biogens Geschäftsbetrieb beinhaltet das Risiko, dass es zu Umweltverschmutzungen kommt oder dass Personen Scha- den nehmen. Dies beinhaltet auch die Kosten für Einhal- tung von Umweltschutzvorschriften.  Der illegale Vertrieb und Verkauf gefälschter oder gestoh- lener Biogen -Produkten durch Dritte könnte sich auf den Ruf der Gesellschaft und ihr Geschäft nachteilig auswirken.  Die zunehmende Nutzung sozialer Medienplattformen (social media) birgt neue Risiken und Herausforderungen. Social media Praktiken in der biopharmazeutischen Indust- rie entwickeln sich weiter und die Vorschriften, die sich auf die Nutzung beziehen, sind nicht immer eindeutig. Diese Entwicklung schafft Unsicherheit und birgt das Risiko, dass Vorschriften, die auf das Geschäft der Gesellschaft an- wendbar sind, nicht eingehalten werden.

D.3 Wertpapierbezogene Risiken  Der Marktpreis von Biogen-Stammaktien könnte Schwan- kungen unterliegen und unter den Kaufpreis der im Rahmen des ESPP erworbenen Aktien fallen.  Biogen kann nicht zusichern, dass sie weiterhin Aktien zurückkaufen wird oder dass sie Aktien zu günstigen Prei- sen zurückkaufen wird.

 Die Ausgabe weiterer Biogen-Aktien könnte zu einer Ver- wässerung der Beteiligung, der Stimmrechte und der Er- gebnisse je Stammaktie führen.  Bestimmungen zum Kontrollwechsel in einigen Kooperati- onsverträgen von Biogen könnten Dritte von dem Versuch einer Übernahme der Gesellschaft abhalten.  Biogen kann den Mitarbeitern, die am ESPP teilnehmen, Dividendenzahlungen für die Zukunft nicht zusichern.

Abschnitt E – Das Angebot

E.1 Nettoemissionserlöse und Zum Datum dieses Prospekts werden die Aktien im Rahmen geschätzte Gesamtkosten des ESPP ca. 7.300 Teilnahmeberechtigten Mitarbeitern der Emission weltweit angeboten. Der Höchstbetrag, den Mitarbeiter pro Kalenderjahr, in dem das Recht ausstehend ist, für den Erwerb von Aktien ausgeben dürfen, darf USD 25.000 nicht über- schreiten. Der Höchstbetrag von USD 25.000 beinhaltet den von Biogen gewährten Unternehmensrabatt, so dass die jährli- che Obergrenze für den Kauf bei USD 21.250 liegt. Unter der Annahme, dass jeder der ca. 7.300 Teilnahmeberechtigten Mitarbeiter innerhalb von zwölf Monaten nach dem Datum des Prospekts die jährliche maximale Anzahl an von im Rah- men des ESPP angebotenen Aktien erwirbt, d. h. jeweils Ak- tien im Gesamtwert von USD 25.000 zum Preis von USD 21.250, so würde nach Abzug der geschätzten Kosten des Angebots im Rahmen des ESPP in Höhe von USD 50.000 der Nettoemissionserlös von Biogen in Zusammenhang mit dem Angebot im Rahmen des ESPP gemäß diesem Prospekt USD 155.075.000 betragen.

E.2a Gründe für das Angebot Zweck des ESPP ist es, Teilnahmeberechtigten Mitarbeitern und Verwendung des Emis- die Möglichkeit zu bieten, im Wege von Gehaltseinbehalten sionserlöses Stammaktien der Gesellschaft zu einem ermäßigten Bezugs- preis zu erwerben. Die Gesellschaft kann die Erlöse aus der Ausgabe und Aus- übung von Erwerbsrechten (Definition siehe unten in Ab- schnitt E.3) im Rahmen des ESPP für alle Geschäftszwecke nutzen.

E.3 Beschreibung der Angebots- Die Gesellschaft bietet drei aktienbasierte Vergütungspläne bedingungen an, im Rahmen derer derzeit Prämienzuteilungen erfolgen: den Biogen Inc. (vormals Biogen Idec Inc.) Eigenkapitalplan für nicht angestellte Verwaltungsratsmitglieder von 2006 (Bi- ogen Inc. 2006 Non-Employee Directors Equitiy Plan), der Biogen Inc. (vormals Biogen Idec Inc.) Omnibus Eigenkapi- talplan von 2008 (Biogen Inc. 2008 Omnibus Equity Plan) und der ESPP. Gegenstand dieses Prospekts sind die Angebote von Stamm- aktien der Biogen im Rahmen des ESPP. Der ESSP sieht die Gewährung von Erwerbsrechten für teilnahmeberechtigte Mit- arbeiter der Gesellschaft oder ihrer Tochtergesellschaften vor, die die Teilnehmer am ESPP zum Erwerb von Stammaktien der Gesellschaft zu einem festgelegten Kaufpreis berechtigen.

Mit Ausnahme des ESPP lösen die aktienbasierten Vergü- tungspläne der Gesellschaft keine Pflicht zur Veröffentlichung eines Prospektes gemäß der EU-Prospektrichtlinie aus. Daher sind weder die entsprechenden Prämien, noch die zugrunde liegenden Aktien Gegenstand dieses Prospektes. Diese Prä- mien werden in diesem Prospekt nicht behandelt. Angebotene Aktien Bei den im Rahmen des ESPP angebotenen Aktien handelt es sich um Stammaktien der Gesellschaft im Nennwert von jeweils USD 0,0005 pro Aktie. Insgesamt stehen im Rahmen des ESPP 6.200.000 Aktien zum Erwerb zur Verfügung. Verwaltung des ESPP Der ESPP wird vom Vergütungs- und Managemententwick- lungsausschuss (Compensation and Management Develop- ment Committee; „Vergütungsausschuss“) des Verwaltungs- rats (der „Planverwalter“), verwaltet. Teilnahmeberechtigte Mitarbeiter Jeder Mitarbeiter von Biogen oder einer ihrer ausgewählten Tochtergesellschaften, der (i) regulär mehr als fünf Monate pro Kalenderjahr beschäftigt ist, (ii) regulär mindestens 20 Wochenstunden arbeitet, und (iii) die Bedingungen des ESPP erfüllt, insbesondere die Registierungsunterlagen (ein- schließlich des Formulars zur Ermächtigung von Gehaltsein- behalten) rechtzeitig ausfüllt und einreicht, ist zur Teilnahme am ESPP berechtigt („Teilnahmeberechtigter Mitarbeiter“). Der Planverwalter kann zusätzliche Teilnahmevoraussetzun- gen für Angebotszeiträume festlegen, die noch nicht begonnen haben. Angebotszeitraum Die Stammaktien der Gesellschaft werden im Rahmen des ESPP durch eine Reihe von aufeinander folgenden dreimona- tigen Angebotszeiträumen (offering periods) zum Erwerb angeboten, die jeweils am ersten Geschäftstag eines Kalender- quartals beginnen und am letzten Geschäftstag eines Kalen- derquartals enden („Angebotszeitraum“), es sei denn der Planverwalter legt etwas anderes fest,. Während der Gültigkeit dieses Prospekts bestehen die folgenden Angebotszeiträume: 1. April 2016 bis 30. Juni 2016, 1. Juli 2016 bis 30. September 2016, 1. Oktober 2016 bis 31. Dezember 2016 und 1. Januar 2017 bis 31. März 2017. Erwerbsrechte und Kaufpreis Am ersten Tag eines Angebotszeitraums erhält jeder teilnehmende Teilnahmeberechtigte Mitarbeiter („Teilnehmer“) automatisch das Recht, am letzten Geschäftstag des betreffenden Angebotszeitraums (jeweils ein „Kauftag“) Stammaktien zu erwerben („Erwerbsrecht“). Ein Mitarbeiter erhält jedoch kein Erwerbsrecht im Rahmen des ESPP, wenn dieser unmittelbar nach Gewährung des Erwerbsrechts im Besitz von Aktien wäre, die dann 5 % oder mehr der gesamten Stimmrechte oder des gesamten Wertes aller Aktiengattungen der Gesellschaft

bzw. einer ihrer Tochtergesellschaften entsprechen (oder ge- mäß anwendbarem Recht entsprechend gestellt würde). Der Kaufpreis von Stammaktien, die bei der Ausübung eines Erwerbsrechts am Kauftag des betreffenden Angebotszeit- raums ausgegeben werden, beträgt fünfundachtzig Prozent (85 %) des jeweils niedrigeren der folgenden Beträge: (a) des Marktwerts einer Stammaktie am ersten Geschäftstag des An- gebotszeitraums oder (b) des Marktwerts einer Stammaktie am Kauftag („Kaufpreis“). Der Marktwert entspricht dem am jeweiligen Tag am NASDAQ notierten Schlusskurs der Biogen- Stammaktien. Handelt es sich bei diesem Tag nicht um einen Handelstag, gilt als Marktwert der notierte Schlusskurs am Handelstag unmittelbar vor diesem Tag. Ausübung des Erwerbsrechts Jedes Erwerbsrecht wird automatisch am Kauftag ausgeübt. Für jeden Teilnehmer werden dann am jeweiligen Kauftag entsprechend Stammaktien der Gesellschaft gekauft. Die Kauftage während der Gültigkeit des Prospekts sind der 30. Juni 2016, der 30. September 2016, der 31. Dezember 2016 und der 31. März 2017. Kaufpreiszahlung - Gehaltseinbehalte In der Regel wird der Kaufpreis durch automatisch vom Ge- halt des Teilnehmers einbehaltene Beträge gezahlt und zum Erwerb von Stammaktien der Gesellschaft am Ende eines jeden Angebotszeitraumes verwendet. Der Teilnehmer ermäch- tigt die Gesellschaft zu Gehaltseinbehalten in Höhe von ma- ximal 10 % des versteuerten Einkommens pro Zahlungszeit- raum in 1 % Schritten. Das versteuerte Einkommen umfasst das reguläre Grundgehalt, Überstunden, Schichtzulagen, jähr- liche Boni, Provisionen und sonstige Verkaufsanreize. Die von einem Teilnehmer erteilte Ermächtigung zur Durch- führung von Gehaltseinbehalten bleibt so lange für die darauf- folgenden Angebotszeiträume in Kraft, bis der Teilnehmer nicht mehr am ESPP teilnimmt oder seine Ermächtigung zu- rücknimmt bzw. ein neues Formular mit der Ermächtigung zur Durchführung geänderter Gehaltseinbehalte übermittelt. Ein Teilnehmer kann im Laufe eines Angebotszeitraums den Be- trag des von ihm gestatteten Gehaltseinbehalts einmalig verringern, jedoch nicht erhöhen. Soweit ein Teilnehmer im Lau- fe eines Angebotszeitraums den von ihm gestatteten Gehalts- einbehalt auf null Prozent (0 %) reduziert, werden die zuvor während dieses Angebotszeitraums aufgelaufenen Gehaltsein- behalte am Kauftag des betreffenden Angebotszeitraums zum Kauf von Stammaktien eingesetzt. Daraufhin endet die Teil- nahme des Teilnehmers am ESPP. Beträge, die vom Gehalt einbehalten, jedoch nicht zum Er- werb von Stammaktien verwendet wurden, sei es, weil der Teilnehmer von seiner Teilnahme an einem Angebotszeitraum zurückgetreten ist oder aus sonstigen Gründen, werden dem Teilnehmer so schnell wie verwaltungstechnisch nach einem solchen Rücktritt bzw. Ereignis möglich, zinslos erstattet. Der Teilnehmer kann sein persönliches Konto bzw. eine de-

taillierte Aufstellung seiner bisherigen Käufe einsehen, indem er sich mit Fidelity Investments ("Fidelity"), dem von Biogen bestimmten Dienstleistungsanbieter für die Aktienpläne unter +1 800-544-0275 bzw. online über www.netbenefits.fidelity.com in Verbindung setzt. Kaufobergrenzen Pro Kalenderjahr kann ein Teilnehmer im Rahmen des ESPP Stammaktien der Gesellschaft im Marktwert von bis zu – jedoch nicht mehr als – USD 25.000 kaufen. Zusätzlich zu der Obergrenze von USD 25.000 pro Kalenderjahr darf ein Teilnehmer an einem Kauftag nicht mehr als 2.500 Aktien kaufen. Lieferung Jedes Erwerbsrecht wird automatisch am Kauftag ausgeübt. Der Kauf erfolgt durch Verwendung des Betrags, der vom Gehalt des Teilnehmers für den an diesem Kauftag endenden Angebotszeitraum einbehalten wurde, zum Kauf von Stamm- aktien der Gesellschaft. Die Lieferung der gekauften Aktien erfolgt so bald wie möglich, regelmäßig innerhalb von 7 bis 10 Tagen, nach dem jeweiligen Kauftag. An innerhalb oder außerhalb der USA ansässige Mitarbeiter aufgrund der Ausübung von Erwerbsrechten auszugebende Aktien werden auf einem dafür vorgesehenen, bei Fidelity für den Teilnehmer geführten Brokerkonto hinterlegt und auf Fi- delity registriert, es sei denn dies wird vom Planverwalter an- derweitig festgelegt. Beendigung der Teilnahme Der Teilnehmer kann seine Teilnahme am Plan durch Über- mittlung einer entsprechenden Erklärung an den Planverwalter unter Einhaltung der hierfür von dem Planverwalter festgelegten Verfahren sowie in einer für diesen akzeptablen Form, widerrufen. Damit diese Widerrufserklärung im Hinblick auf den nachfolgenden Kauftag wirksam ist, muss sie spätestens fünf (5) Tage vor diesem Kauftag (oder einem anderen, von dem Planverwalter vorgegebenen Datum) übermittelt werden. Im Falle der Beendigung werden die aufgelaufenen, vom Ge- halt des Teilnehmers einbehaltenen Beträge so schnell wie verwaltungstechnisch möglich, zinslos an diesen erstattet. Soweit ein Teilnehmer den Prozentsatz des in Zukunft von seinem Gehalt einzubehaltenden Betrags auf null Prozent (0 %) absenkt, gilt dies als Beendigung der Teilnahme an zu- künftigen Angebotszeiträumen. Beendigung der Teilnahmeberechtigung Bei Beendigung des Beschäftigungsverhältnisses des Teil- nehmers während eines Angebotszeitraums gleich aus wel- chem Grund (einschließlich Tod) oder wenn dieser nicht mehr zum Kreis der Teilnahmeberechtigten Mitarbeiter zählt, hört er auf, ein Teilnehmer zu sein, werden alle Erwerbsrechte storniert, werden die aufgelaufenen Gehaltseinbehalte so schnell wie dann verwaltungstechnisch möglich an den Teil- nehmer (oder im Falle seines Todes an seinen Nachlass oder

an den von ihm Begünstigten) zinslos erstattet und stehen dem Teilnehmer im Rahmen des Plans keine weiteren Rechte zu. Laufzeit, Beendigung und Änderung Der Verwaltungsrat der Gesellschaft kann den ESPP jederzeit aussetzen oder beenden. Der Verwaltungsrat kann den ESPP jederzeit in dem Umfang und in der Weise ändern, wie er es für angebracht hält. Übertragbarkeit von Erwerbsrechten Im Rahmen des ESPP gewährte Erwerbsrechte können von den Teilnehmern weder abgetreten noch übertragen werden, ausgenommen durch Testament oder im Wege der gesetzli- chen Erbfolge oder durch Nachlassverteilung nach dem Tod des Teilnehmers; zu Lebzeiten des Teilnehmers kann nur der Teilnehmer selbst das Erwerbsrecht ausüben. Registrierung Die Teilnahme am ESPP erfolgt auf freiwilliger Basis. Jeder Teilnahmeberechtigte Mitarbeiter muss sich für die Teilnahme registrieren. Die Teilnahmeberechtigten Mitarbeiter werden vor jedem Angebotszeitraum intern, durch entsprechende Mit- teilungen im Intranet der Gesellschaft, über die Registrie- rungsfristen informiert. Provision Beim Verkauf von Aktien, die nach Ausübung eines Erwerbs- rechts erworben wurden, wird von Fidelity und der SEC eine Provision berechnet.

E.4 Beschreibung aller für das Entfällt. Es gibt keine derartigen Interessen. Angebot wesentlichen Inte- ressen, einschließlich von Interessenskonflikten

E.5 Name des Unternehmens, Biogen Inc. das die Wertpapiere zum Verkauf anbietet

E.6 Maximale Verwässerung Der Buchwert des Eigenkapitals der Gesellschaft (definiert als gesamtes Vermögen minus gesamte Verbindlichkeiten) gemäß den ungeprüften verkürzten Konzernabschlüssen betrug zum 31. Dezember 2015 etwa USD 9.374.900.000. Dies entspricht ungefähr USD 42,87 pro Aktie (errechnet auf Basis von 218.667.750 ausgegebenen Aktien per 31. Dezember 2015). Wenn die Gesellschaft zum 31. Dezember 2015 einen Netto- emissionserlös in Höhe von USD 155.075.000 erhalten hätte, hätte der Buchwert des Eigenkapitals zu diesem Zeitpunkt ungefähr USD 9.529.975.000 oder USD 43,45 pro Aktie betragen (auf Basis der erhöhten Anzahl ausgegebener Aktien nach dem Kauf von 673.680 Aktien und eines angenommenen Kaufpreises von USD 230,27, wobei der Rabatt berücksichtigt wird, was 85 % des Schlusskurses der Aktien am 1. März 2016 entspricht). Auf Basis der oben beschriebenen Annah- men würde die Durchführung des Angebots daher zu einer unmittelbaren Erhöhung des Buchwertes des Eigenkapitals

von ungefähr USD 155.075.000 oder USD 0,58 pro Aktie, entsprechend ungefähr 1,34 % für die bestehenden Aktionäre und zu einer durchschnittlichen Verwässerung von ungefähr USD 186,83 pro Aktie für den teilnahmeberechtigten Mitar- beiter, der Aktien erworben hat, führen. Investoren, die Aktien zu einem Kaufpreis von USD 230,27 erwerben, unterliegen daher einer Verwässerung von ungefähr 81,13%.

E.7 Schätzung der dem Anleger Entfällt. Es gibt keine derartigen Ausgaben. vom Emittenten in Rech- nung gestellten Ausgaben

PROSPECTUS SUMMARY

Note to the reader

Summaries are made up of disclosure requirements known as “Elements.” These elements are numbered in Sections A – E (A.1 – E.7).

This summary contains all the Elements required to be included in a summary for this type of securities and issuer. Because some Elements are not required to be addressed, there may be gaps in the numbering sequence of the Elements.

Even though an Element may be required to be inserted in the summary because of the type of securities and issuer, it is possible that no relevant information can be given regarding the Element. In this case a short description of the Element is included in the summary with the mention of “not applicable” together with a short explanatory statement.

Section A – Introduction and Warnings

A.1 Introduction and Warnings This summary should be read as an introduction to the prospectus. Any decision to invest in the securities should be based on consideration of the prospectus as a whole by the investor. Where a claim relating to the information contained in the prospectus is brought before a court, the plaintiff investor might, under the national legislation of the member states of the European Economic Area, have to bear the costs of translating the prospectus before the legal proceedings are ini- tiated. Civil liability attaches to those persons who have assumed responsibility for the contents of the summary or presented the summary including any translation thereof, but only if the summary is misleading, inaccurate or inconsistent when read together with the other parts of the prospectus or it does not provide, when read together with the other parts of the prospectus, the required key information.

A.2 Use of the prospectus for Not applicable. The issuer has not consented to the use of the subsequent resale or final prospectus for subsequent resale or final placement of securi- placement of securities by ties. financial intermediaries.

Section B – Issuer

B.1 Legal and Commercial The legal and commercial name of the issuer is Biogen Inc. Name of the Issuer References in this summary to “Biogen” or the “Company” shall mean Biogen Inc. and its consolidated subsidiaries, unless the context indicates otherwise.

B.2 Domicile and Legal Form of Biogen is a corporation. Biogen’s principal offices are located Biogen, the Legislation un- at 225 Binney Street, Cambridge, Massachusetts 02142, der which the Issuer oper- U.S.A. The Company was formed as a California corporation ates and its Country of In- in 1985 and became a Delaware corporation in 1997. In 2003, corporation the Company acquired Biogen, Inc. and changed its corporate name from IDEC Pharmaceuticals Corporation to Biogen Idec Inc. Effective March 23, 2015, the Company changed its name from Biogen Idec Inc. to Biogen Inc.

B.3 Description of the Nature of Biogen is a global biopharmaceutical company focused on Biogen’s current Operations discovering, developing, manufacturing and delivering thera- and its principal Activities pies to patients for the treatment of neurodegenerative diseas- and identification of the es, hematologic conditions and autoimmune disorders. Its principal markets in which marketed products include TECFIDERA, AVONEX, PLE- the Issuer competes GRIDY, TYSABRI and FAMPYRA for multiple sclerosis (“MS”), ELOCTATE for hemophilia A and ALPROLIX for hemophilia B, and FUMADERM for the treatment of severe plaque psoriasis. Biogen also has a collaboration agreement with Genentech, Inc. (“Genentech”), a wholly-owned member of the Roche Group (“Roche Group”), which entitles Biogen to certain business and financial rights with respect to RITUXAN for the treatment of non-Hodgkin's lymphoma, chronic lymphocytic leukemia (“CLL”) and other conditions, GAZYVA indicated for the treatment of CLL, and other potential anti-CD20 therapies (therapies against the protein CD20 which is found on the surface of immune cells). Sum- mary information about the Company’s marketed products is as follows:

• TECFIDERA (dimethyl fumarate), an oral therapy indicated in the United States (“U.S.”) for the treatment of patients with relapsing forms of MS and in the European Un- ion (“E.U.”) for people with relapsing-remitting MS (“RRMS”).

• AVONEX (interferon beta-1a), an intramuscular injectable therapy, indicated for the treatment of patients with relapsing forms of MS.

• PLEGRIDY (peginterferon beta-1a), a subcutaneous injectable therapy, indicated in the U.S for the treatment of patients with relapsing forms of MS and in the E.U. for RRMS.

• TYSABRI (natalizumab), a monoclonal antibody approved in numerous countries as a monotherapy for the treatment of patients with relapsing forms of MS. TYSABRI is also approved in the U.S. to treat Crohn’s disease, an inflam- matory disease of the intestines.

 FAMPYRA (prolonged-release fampridine tablets), is indicated for the improvement of walking ability in adult patients with MS. The Company has a license from Acorda Therapeutics, Inc. to develop and commercialize FAMPYRA in all markets outside the U.S.

• ELOCTATE (Antihemophilic Factor (Recombinant), Fc Fusion Protein), a recombinant DNA-derived, antihemophilic factor indicated in the U.S. for treatment in adults and children with hemophilia A for control of bleeding episodes. • ALPROLIX (Coagulation Factor IX (Recombinant), Fc Fusion Protein), a recombinant DNA-derived, coagulation Factor IX concentrate indicated in the U.S. for treatment in adults and children with hemophilia B for control of bleed-

ing episodes. • RITUXAN (rituximab), a widely prescribed monoclonal antibody used to treat non-Hodgkin’s lymphoma, rheumatoid arthritis, CLL and two forms of antineutrophil cytoplasmic antibodies (ANCA)-associated vasculitis. • GAZYVA (obinutuzumab), in combination with chlorambucil, is indicated for the treatment of patients with previously untreated CLL. The major markets for Biogen’s business are the U.S., Europe (excluding Germany), Germany, Asia and other which represented approximately 71%, 16%, 7%, 2% and 4% of its 2015 product revenues, respectively, as of December 31, 2015. The Company supports its drug discovery and development efforts through the commitment of significant resources to discovery, research and development programs and business development opportunities, particularly within areas of the Company’s scientific, manufacturing and technical expertise and scientific adjacencies. In addition to its innovative drug development efforts, the Company aims to leverage its manufacturing capabilities and scientific expertise to extend its mission to improve the lives of patients living with serious diseases through the development, manufacture and marketing of biosimilars through Sam- sung Bioepis, its joint venture with Samsung BioLogics Co. Ltd. (“Samsung Biologics”). In January 2016, the European Commission (“EC”) approved the marketing authorization application (“MAA”) for BENEPALI, an etanercept biosimilar referencing ENBREL, for marketing in the E.U. Under the Company’s agreement with Samsung Bioepis, Biogen will manufacture and commercialize BENEPALI in specified E.U. countries.

In connection with its business strategy, Biogen has entered into various collaboration agreements which provide it with rights to develop, produce and market products using certain know-how, technology and patent rights maintained by its collaborative partners. Terms of the various collaboration agreements may require the Company to make milestone payments upon the achievement of certain product research and development objectives and pay royalties on future sales, if any, of commercial products resulting from the collaboration.

Patents are important to obtaining and protecting exclusive rights in the Company’s products and product candidates. Regulatory exclusivity, which may consist of regulatory data protection and market protection, also can provide meaningful protection for the Company’s products. The Company regularly seeks patent and regulatory protection in the U.S. and in selected countries outside the U.S.

The Company’s trademarks are important to it and are generally covered by trademark applications or registrations in the U.S. Patent and Trademark Office (“USPTO”) and the patent

or trademark offices of other countries.

The Company’s current and contemplated activities and the products, technologies and processes that will result from such activities as well as sales, marketing, product pricing and reimbursement are subject to substantial government regulation.

B.4a Most significant recent The Company’s current revenues depend upon continued sales Trends affecting the Issuer of its principal products. The Company may be substantially and its Industry dependent on sales from its principal products for many years, including an increasing reliance on sales of TECFIDERA as the Company further expands into additional markets. Sales of the Company’s products depend, to a significant extent, on adequate coverage, pricing and reimbursement from third party payors, which are subject to increasing and intense pressure from political, social, competitive and other sources. The biopharmaceutical industry and the markets in which the Company operates are intensely competitive. Many of the Company’s competitors are working to develop or have commercialized products similar to those the Company markets or is developing. In addition, the commercialization of certain of the Company’s own approved MS products, MS products of the Company’s collaborators and pipeline product candidates may negatively impact future sales of its existing MS products. The Company’s products may also face increased competitive pressures from the introduction of generic versions, prodrugs of existing therapeutics or biosimilars of existing products and other technologies, such as gene therapies. In the longer term, the Company’s revenue growth will be dependent upon the successful clinical development, regulatory approval and launch of new commercial products as well as additional indications for the Company’s existing products, its ability to obtain and maintain patents and other rights related to its marketed products and assets originating from its research and development efforts, and successful execution of external business development opportunities. As part of its ongoing research and development efforts, the Company intends to continue committing significant resources to targeted research and development opportunities where there is a significant unmet need and where the drug candidate has the potential to be highly differentiated. Specifically, the Company intends to continue to invest in its MS pipeline, its programs for Alzheimer’s disease (aducanumab, BAN2401 and E2609), the nusinersen program for the treatment of spinal muscular atrophy, the amiselimod program for development of product candidates for multiple autoimmune indications and its Rax- atrigine program for development of product candidates for neuropathic pain.

B.5 Description of the Group Not applicable, because information regarding the organiza- and Issuer’s Position within tional structure of Biogen is not required to be provided else- the Group where in the prospectus.

B.6 Interests in Biogen’s Capital Not applicable, because information regarding Biogen’s capital structure is not required to be provided elsewhere in the

prospectus.

B.7 Financial Information re- The following selected financial data are derived from the garding Biogen and subse- Company’s audited consolidated financial statements for the quent material changes fiscal years ended December 31, 2015, December 31, 2014 and December 31, 2013, as published in the Company’s An- nual Report on Form 10-K for the fiscal year ended December 31, 2015 which can be accessed as described in the section “Documents Available for Inspection” of this prospectus. The Company’s audited consolidated financial statements were prepared in accordance with accounting principles generally accepted in the United States of America (“U.S. GAAP”). SELECTED THREE-YEAR FINANCIAL DATA (In millions, except per share amounts) For the Years Ended Decem- ber 31,

2015(3) (4) 2014 2013(1) (2) Results of Operations Product revenues, net $ 9,188.5 $ 8,203.4 $ 5,542.3 Revenues from unconsoli- 1,339.2 1,195.4 1,126.0 dated joint business Other revenues 236.1 304.5 263.9 Total revenues 10,763.8 9,703.3 6,932.2 Total cost and expenses 5,872.8 5,747.7 4,441.6 Gain on sale of rights — 16.8 24.9 Income from operations 4,891.0 3,972.4 2,515.5 Other income (expense), net (123.7 ) (25.8 ) (34.9 ) Income before income tax expense and equity in loss of investee, net of tax 4,767.3 3,946.6 2,480.6

Income tax expense 1,161.6 989.9 601.0 Equity in loss of investee, 12.5 15.1 17.2 net of tax Net income 3,593.2 2,941.6 1,862.3 Net income (loss) attributa- 46.2 6.8 — ble to non-controlling interests, net of tax Net income attributable to $ 3,547.0 $ 2,934.8 $ 1,862.3 Biogen Inc.

Diluted Earnings Per Share Diluted earnings per share attributable to Biogen Inc. 15.34 12.37 7.81

Weighted-average shares used in calculating diluted earnings per share attributa- 231.2 237.2 238.3 ble to Biogen Inc.

As of December 31,

2015(5) (6) 2014 2013 Financial Condition Cash, cash equivalents and marketable securities $ 6,188.9 $ 3,316.0 $ 1,848.5

Total assets $ 19,504.8 $14,314.7 $ 11,863.3

Notes payable, line of credit and other financing ar- $ 6,521.5 $ 580.3 $ 592.4 rangements, less current portion Total Biogen Inc. share- $ 9,372.8 $10,809.0 $ 8,620.2 holders’ equity

(1) The Company’s share of revenues from unconsolidated joint business reflects a charge of $49.7 million in 2013 for damages and interest awarded to Hoechst in Genentech’s arbitration with Hoechst for RITUXAN.

(2) Commencing in the second quarter of 2013, product and total revenues include 100% of net revenues related to sales of TYSABRI as a result of the Company’s acquisition of all remaining rights to TYSABRI from Elan Pharma International, Ltd (“Elan”), an affiliate of Elan Corporation, plc. Upon the closing, the Company’s collaboration agreement was terminated, and the Company no longer records collaboration profit sharing expense. The Company recognized collaboration profit sharing expense of $85.4 million during the year ended December 31, 2013. In addition, product and total revenues includes net revenues related to sales of TECFIDERA. (3) Other revenues reflects a decrease in royalty revenues due to the December 2014 expiration of U.S. patent rights that gave rise to royalty payments related to ANGIOMAX.

(4) Included in total cost and expenses is a restructuring charge of $93.4 million incurred in connection with the Company’s corporate restructuring announced on October 21, 2015, which included the termination of certain pipeline programs and an 11% reduction in workforce.

(5) Notes payable, line of credit and other financing arrangements, less current portion reflects the issuance of the Company’s senior unsecured notes for an aggregate principal amount of $6.0 billion on September 15, 2015.

(6) Biogen Inc.'s shareholders' equity reflects a reduction in additional paid in capital and retained earnings totaling $5.0 billion resulting from the repurchase and retirement of the Company’s common stock under the Company’s 2015 Share Repurchase Program.

There has been no significant change in the Company’s financial or trading position since December 31, 2015.

B.8 Pro Forma Financial Infor- Not applicable, because no historical financial information is mation required to be provided in the prospectus.

B.9 Profit Forecast Not applicable. This prospectus does not contain any profit forecast.

B.10 Qualifications in the Audit Not applicable. There are no such qualifications in the audi- Report on the historical Fi- tors’ report. nancial Information

B.11 Working Capital Statement Biogen believes that its working capital (i.e., its ability to access cash and other available liquid resources) is sufficient to meet its present requirements for at least the next 12 months from the date of this prospectus.

Section C – Securities

C.1 Type and Class of the Securi- The securities offered under the Biogen Inc. 2015 Employee ties being offered, including Stock Purchase Plan (“ESPP”) are Biogen’s common stock the Security Identification with a par value of USD 0.0005 per share. Code The Company’s common stock is listed on the NASDAQ Global Select Market (“NASDAQ”) under the symbol “BIIB”. The U.S. security identification (“CUSIP”) number of the shares is 09062X103. The International Securities Identifica- tion Number (“ISIN”) for the Company’s common stock is US09062X1037. The German Securities Code Number (Wertpapier-Kenn-Nummer) is 789617.

C.2 Currency of the Securities The U.S. Dollar is the currency of the securities issue. Issue

C.3 Number of Shares Issued Common shares issued and outstanding: 218,667,750 as of December 31, 2015 with a par value of USD 0.0005 each.

C.4 Rights attached to the Securi- No Eligible Employee (as defined in Section E.3 below) parties ticipating in the ESPP shall have any voting, dividend or other shareholder rights with respect to any offering under the ESPP until the shares are purchased pursuant to the ESPP on behalf of the Participant (as defined in Section E.3 below) and the Participant has become a holder of the purchased shares. Fol- lowing the purchase, the Eligible Employee participating in the ESPP shall be entitled to the rights attached to the shares, as further described below: Dividend Rights. The Board of Directors may declare a dividend at any regular or special meeting out of funds legally available for dividends. The Board of Directors sets the record date and the payment date for dividend payments. Such dividends may be paid in cash, property or shares of stock. A holder of shares as of the record date for a dividend declaration has an inchoate property right to the dividend as of that

record date, but may not actually attempt to enforce that right until the payment date. In general, dividends that are unclaimed for three years escheat to the State of Delaware. However, Biogen has never paid any cash dividends and has no current intention to do so. There are no dividend restrictions and no special dividend procedures for shareholders resident in the E.U. and the European Economic Area. Voting Rights. The holders of common stock are entitled to one vote for each share held on all matters as to which shareholders are entitled to vote. Any action required or permitted to be taken by the shareholders for the Company may be effected by a duly called annual or special meeting of such holders or may be effected by consent in writing by such shareholders. Special meetings of the shareholders of the Company may be held upon call of the Chairman of the Board of Directors, the Chief Executive Officer, by the Board of Directors of the Company or, in accordance with the Compa- ny’s Bylaws, holders of at least 25% of the Company’s common stock. Rights to Receive Liquidation Distributions. In the event of liquidation, dissolution or winding up of the Company, the holders of common stock are entitled to share ratably in all assets remaining after payment of or provisions for the Com- pany’s liabilities, subject to prior rights or preferred stock, if any, then outstanding. No Preemptive, Redemptive, Profit or Conversions Provisions. The holders of the Company’s common stock do not have preemptive rights to acquire shares of the Company’s stock or securities convertible into the Company’s stock. The Compa- ny’s common stock is not subject to redemption and does not have any right to share in the Company’s profits or any conversion rights.

C.5 Transferability The offering of shares under the ESPP has been registered in the U.S. with the U.S. Securities and Exchange Commission (“SEC”) on a registration statement on Form S-8 and the issued and outstanding shares of common stock are generally freely transferable. The ESPP is intended to provide shares for investment. The Company does not, however, intend to restrict or influence any employee in the conduct of his or her own affairs. A Par- ticipant, therefore, may sell shares purchased under the ESPP at any time he or she chooses, subject to compliance with any applicable securities laws, insider trading policies and applicable blackout periods, and the terms of the ESPP. The Partic- ipant assumes the risk of any market fluctuations in the price of the shares.

C.6 Admission to Trading on a Not applicable. The Company’s common stock is listed on the NASDAQ under the symbol “BIIB”. The stock is quoted on Regulated Market NASDAQ in U.S. dollars. In Germany, the shares are traded on the Open Market (Freiverkehr) on the exchanges in Frank- furt, Stuttgart, Berlin, Düsseldorf, Hamburg and Munich as

well as on Tradegate under the symbol “IDP”.

C.7 Dividend Policy No cash dividends have been declared or paid since Biogen was founded and the Company has no current intention to declare or pay cash dividends.

Section D – Risks

Employees should carefully consider the risks described below, which are described in more detail under the caption “Risk Factors”, and other information contained in this prospectus, and take these factors into account in making their investment decision. The occurrence of one or more of these risks alone or in combination with other circumstances may have a material adverse effect on the business and financial condition of the Company and cause the market price of the Company’s shares to decline. In such case, employees could lose all or part of their investment. The prospectus contains all risks which the Company deems material. However, the risks described below may turn out to be incomplete and therefore may not be the only risks to which the Company is exposed. Additional risks and uncertainties could have a material adverse effect on the business and financial condition of the Company. The order of presentation of the risk factors below does not indicate the likelihood of their occurrence or the extent or the significance of the individual risks.

D.1 Risks related to Biogen or its  Biogen is substantially dependent on revenues from its Industry principal products.

 If Biogen fails to compete effectively, its business and market position would suffer.

 Sales of Biogen’s products depend, to a significant extent, on adequate coverage, pricing and reimbursement from third party payors, which are subject to increasing and intense pressure from political, social, competitive and other sources. The Company’s inability to maintain adequate coverage, or a reduction in pricing or reimbursement, could have an adverse effect on its business, revenues and results of operations, and could cause a decline in the Company’s stock price.

 Biogen’s results of operations may be adversely affected by current and potential future healthcare reforms.

 Adverse safety events or restrictions on use and safety warnings for Biogen’s products can negatively affect its business, product sales and stock price.

 If Biogen is unable to obtain and maintain adequate protection for its data, intellectual property and other proprietary rights, its business may be harmed.

 Biogen's long-term success depends upon the successful development of new products and additional indications for existing products.

 Clinical trials and the development of biopharmaceutical products is a lengthy and complex process. If Biogen fails

to adequately manage its clinical activities, its clinical trials or potential regulatory approvals may be delayed or denied.

 Successful preclinical work or early stage clinical trials does not ensure success in later stage trials, regulatory approval or commercial viability of a product.

 Manufacturing issues could substantially increase Biogen’s costs, limit supply of its products and reduce its revenues.

 Biogen depends on relationships with collaborators and other third-parties for revenue, and the development, regulatory approval, commercialization and marketing of certain products, which are outside of its full control.

 The Company may fail to achieve the expected financial and operating benefits of its corporate restructuring and the restructuring may harm its business and financial results.

 Biogen’s business may be adversely affected if the Compa- ny does not manage its current growth and does not successfully execute its growth initiatives.

 A breakdown or breach of Biogen’s technology systems could subject it to liability or interrupt the operation of its business.

 If Biogen fails to comply with the extensive legal and regulatory requirements affecting the health care industry, it could face increased costs, penalties and a loss of business.

 The Company’s indebtedness could adversely affect its business and limit its ability to plan for or respond to changes in its business.

 Biogen’s sales and operations are subject to the risks of doing business internationally.

 Biogen’s effective tax rate may fluctuate and it may incur obligations in tax jurisdictions in excess of accrued amounts.

 Biogen’s operating results are subject to significant fluctuations.

 Biogen is pursuing opportunities to expand its manufacturing capacity for future clinical and commercial requirements for product candidates, which will result in the incurrence of significant investment with no assurance that such investment will be recouped.

 The Company’s investment in Samsung Bioepis and its success in commercializing biosimilars developed by Sam- sung Bioepis, are subject to risks and uncertainties inherent in the development, manufacture and commercialization of

biosimilars.

 Biogen’s investments in properties may not be fully realized.

 Biogen’s portfolio of marketable securities is subject to market, interest and credit risk that may reduce its value.

 Biogen may not be able to access the capital and credit markets on terms that are favorable to it.

 Biogen’s business involves environmental risks, which include the cost of compliance and the risk of contamination or injury.

 The illegal distribution and sale by third parties of counterfeit versions of Biogen’s products or stolen products could have a negative impact on its reputation and business.  The increasing use of social media platforms presents new risks and challenges. Social media practices in the biopharmaceutical industry continue to evolve and regulations relating to such use are not always clear. This evolution creates uncertainty and risk of noncompliance with regulations applicable to the Company’s business.

D.3 Key Risks related to the  The marketability of Biogen’s shares of common stock may Shares fluctuate and may decline below the purchase price of the shares acquired under the ESPP.

 Biogen can provide no assurance that it will continue to repurchase stock or that it will repurchase stock at favorable prices.

 The shareholding, voting rights and the earnings per ordinary share may be diluted as a result of an issuance of additional shares of Biogen.

 Some of Biogen’s collaboration agreements contain change in control provisions that may discourage a third party from attempting to acquire it.  Biogen cannot assure employees participating in the ESPP that it will pay any dividends in the future.

Section E – Offer

E.1 Net Proceeds and Estimate of As of the date of this prospectus, the shares under the ESPP total Expenses are offered to approximately 7,300 Eligible Employees worldwide. The maximum rate at which employees may purchase shares may not exceed USD 25,000 worth of stock per calendar year in which the right is outstanding. The USD 25,000 limit includes Biogen’s company contribution via the discount, so each employee’s maximum annual purchase price is USD 21,250. Assuming that each of the approximately

7,300 Eligible Employees purchased the maximum annual amount of shares offered under the ESPP in the twelve months following the date of the prospectus, that is, shares worth a total of USD 25,000 each upon payment of USD 21,250, and after the deduction of the estimated cost of offering under the ESPP of USD 50,000 then the net proceeds to Biogen in connection with the offer under the ESPP pursuant to this prospectus would be USD 155,075,000.

E.2a Reasons for the Offer and The ESPP is intended to enable Eligible Employees to use Use of Proceeds payroll deductions to acquire common stock in the Company at a discount to current market trading prices. The Company may use the proceeds from the issuance and exercise of Purchase Rights (as defined in Section E.3 below) under the ESPP for any corporate purpose.

E.3 Description of the Terms and The Company has three share-based compensation plans pur- Conditions of the Offer suant to which awards are currently being made: the Biogen Inc. (formerly Biogen Idec Inc.) 2006 Non-Employee Direc-

tors Equity Plan; the Biogen Inc. (formerly Biogen Idec Inc.) 2008 Omnibus Equity Plan; and the ESPP. The subject matter of this prospectus is offerings of shares of Biogen’s common stock under the ESPP. The ESPP permits the grant of Purchase Rights (please refer to the subheading Purchase Rights and Purchase Price below for the definition) to Eligible Employees the Company or its subsidiaries, which entitle the Participants in the ESPP to purchase shares of the Company’s common stock at a specified purchase price. With the exception of the ESPP, the Company’s share-based compensation plans do not trigger a prospectus requirement under the European Prospectus Directive. Therefore neither those awards nor the underlying shares for such awards form the subject matter of this prospectus. Such awards are not discussed in this prospectus. Offered Shares The shares offered under the ESPP are shares of the Compa- ny’s common stock with a par value of USD 0.0005 per share. The total number of shares made available for purchase under the ESPP is 6,200,000. Administration of the ESPP The ESPP is administered by the Compensation and Manage- ment Development Committee of the Company’s Board of Directors (referred to as the “Plan Administrator”). Eligible Employee An employee of Biogen or any of its designated subsidiaries who (i) customarily works more than five months per calendar year, (ii) customarily works 20 hours or more per week and (iii) satisfies the requirements in the ESPP, including the requirement to timely complete and submit the enrollment forms (including a payroll deduction authorization form), is eligible to participate in the ESPP (“Eligible Employee”). The Plan

Administrator may establish additional eligibility requirements for offering periods that have not yet commenced. Offering Period Unless otherwise determined by the Plan Administrator, shares of the Company’s common stock are offered for purchase under the ESPP through a series of successive three- month offering periods commencing on the first business day of each calendar quarter and ending on the last business day of each calendar quarter (“Offering Period”). The Offering Peri- ods during the validity of this prospectus are April 1, 2016 to June 30, 2016, July 1, 2016 to September 30, 2016, October 1, 2016 to December 31, 2016 and January 1, 2017 to March 31, 2017. Purchase Rights and Purchase Price On the first day of an Offering Period, each participating Eli- gible Employee (“Participant”) automatically will be granted a right to purchase common stock (“Purchase Right”) on the last business day of each Offering Period (each, a “Purchase Date”). However, no employee may be granted a Purchase Right under the ESPP if, immediately after the Purchase Right is granted, the employee would own (or, under applicable statutory attribution rules, would be deemed to own) stock possessing 5% or more of the total combined voting power or value of all classes of stock of the Company or any of its subsidiaries. The purchase price of shares of common stock issued pursuant to the exercise of a Purchase Right on the Purchase Date of an applicable Offering Period will be eighty-five percent (85%) of the lesser of (a) the Fair Market Value of a share of common stock on the first business day of the Offering Period and (b) the Fair Market Value of a share of common stock on the Purchase Date (“Purchase Price”). The Fair Market Value is the closing price of Biogen common stock as reported on the NASDAQ on the applicable date. If such day is not a trading day, the Fair Market Value will be the reported closing price for the immediately preceding day that is a trading day. Exercise of Purchase Right Each Purchase Right is automatically exercised on the Pur- chase Date and shares of the Company’s common stock are accordingly purchased on behalf of each Participant on each such Purchase Date. The Purchase Dates during the validity of the prospectus are June 30, 2016, September 30, 2016, De- cember 31, 2016 and March 31, 2017. Purchase Price Payment – Payroll Deduction In general, the Purchase Price is paid by way of automatic deduction from the Participant’s’ payroll and used to purchase shares of the Company’s common stock at the end of each Offering Period. The Participant authorizes the Company to make a payroll deduction up to a maximum of 10%, in 1% increments, of after-tax income per pay period. After-tax income includes regular base salary, overtime, shift differen-

tials, annual bonuses, commissions and other sales incentives. A Participant’s payroll deduction authorization will remain in effect for subsequent Offering Periods unless the Participant’s participation in the ESPP terminates or the Participant cancels the authorization or submits a new payroll deduction authorization form. During an Offering Period, a Participant may reduce the amount of his or her payroll deduction authorization one time, but may not increase it. If, during an Offering Period, a Participant reduces his or her payroll deduction authorization to zero percent (0%), payroll deductions previously accumulated during that Offering Period will be applied to purchase shares of common stock on the Purchase Date for that Offering Period and the Participant’s participation in the ESPP will then terminate. Any amount of payroll deductions that are not used for the purchase of shares of common stock, whether because of the Participant’s withdrawal from participation in an Offering Period or for any other reason will be returned to the Partici- pant, without interest, as soon as administratively practicable after such withdrawal or other event, as applicable. A Participant may view an individual account balance and a detailed purchase history by contacting Fidelity Investments® (“Fidelity”), Biogen’s dedicated stock plan service provider, at (+1) 800-544-0275 or by going online to www.netbenefits.fidelity.com. Purchase Limitations A Participant may purchase up to – but not more than – USD 25,000 in Fair Market Value of the Company’s common stock per calendar year under the ESPP. In addition to the USD 25,000 per calendar year purchase limit, each Participant is limited to purchasing no more than 2,500 shares on any Pur- chase Date. Delivery Each Purchase Right is automatically exercised on the Pur- chase Date. The purchase shall be effected by applying the Participant's payroll deductions for the Offering Period, ending on such Purchase Date to the purchase of shares of the Company’s common stock. As soon as practicable after each Purchase Date, which is generally within 7 to 10 days after the Purchase Date, the purchased shares will be delivered. Shares issuable to employees within and outside the U.S. upon exercise of Purchase Rights are deposited into a designated brokerage account with Fidelity maintained on behalf of the Participant and held in “street name”, unless otherwise designated by the Plan Administrator. Termination of Participation The Participant may terminate his or her participation in Plan, by delivering a notice to the Plan Administrator in accordance with the procedures established by, and in a form acceptable to, the Plan Administrator. To be effective with respect to an upcoming Purchase Date, the cancellation notice must be

submitted no later than five (5) business days before such Pur- chase Date (or such other time specified by the Plan Adminis- trator). Upon a termination, the Participant’s accumulated payroll deductions will be returned to the Participant, without interest, as soon as administratively practicable. A Participant who reduces his or her withholding rate for future payroll periods to zero percent (0%) will be deemed to have terminated his or her participation in future Offering Pe- riods. Termination of Eligibility Upon the termination of the Participant’s employment for any reason (including death) during an Offering Period, or in the event he or she ceases to qualify as an Eligible Employee, the Participant ceases to be a Participant, any Purchase Right will be canceled, the accumulated payroll deductions are returned to the Participant (or to his or her estate or designated beneficiary in the event of death) without interest, as soon as administratively practicable thereafter, and the Participant will have no further rights under the Plan. Duration, Termination and Amendment The Board of Directors of the Company may, at any time or times, suspend or terminate the ESPP. The Board of Directors may at any time amend the ESPP to any extent and in any manner as it may deem advisable. Transferability of Purchase Rights Purchase Rights granted under the ESPP are not assignable or transferable by the Participant other than by will or by the laws of descent and distribution following the Participant’s death, and during the Participant’s lifetime the Purchase Right shall be exercisable only by the Participant. Enrollment The ESPP is a voluntary plan and requires Eligible Employees to enroll in order to participate. Prior to each Offering Period, Eligible Employees are notified of the enrollment deadlines by internal postings on the Company’s intranet. Commission On sales of shares obtained upon exercise of the Purchase Rights a commission is charged by Fidelity and the SEC.

E.4 Description of material Inter- Not applicable. There are no such interests. est to the Offer including Conflict or Interests

E.5 Name of the Entity offering Biogen Inc. to sell the Security

E.6 Maximum Dilution The book value of the shareholders’ equity of the Company (defined as total assets less total liabilities) as reflected in the audited condensed consolidated financial statements amounted to approximately USD 9,374,900,000 as of December 31, 2015. This is equivalent to approximately USD 42.87 per

share (calculated on the basis of 218,667,750 issued and outstanding shares as of December 31, 2015). If the Company had obtained net proceeds in the amount of USD 155,075,000 as of December 31, 2015, the book value of the shareholders’ equity at that time would have been about USD 9,529,975,000 or USD 43.45 per share (based on the increased number of shares after the purchase of 673,680 shares assuming a purchase price of USD 230.27 which takes into account the discount and is 85% of the stock’s closing price as of March 1, 2016). Consequently, under the above- mentioned assumptions, the implementation of the offering would lead to a direct increase in the book value of shareholders’ equity of approximately USD 155,075,000 or USD 0.58 per share corresponding to approximately 1.34% per share for the existing shareholders and an average dilution of approximately USD 186.82 per share for the Eligible Employee who purchased the shares and, thus, investors who acquire shares at the purchase price of USD 230.27 are diluted by about 81.13%.

E.7 Estimated Expenses charged Not applicable. There are no such expenses. to the Investor by the Issuer

RISK FACTORS

Before enrollment in the Biogen Inc. 2015 Employee Stock Purchase Plan (“ESPP”), employees should carefully consider the risks described below and other information contained in this prospectus, and take these factors into account in making their investment decision. The occurrence of one or more of these risks alone or in combination with other circumstances may have a material adverse effect on the business and financial condition of the Company and cause the market price of the Company’s shares to decline. In such case, employees could lose all or part of their investment. The prospectus contains all risks which the Company deems material. However, the risks described below may turn out to be incomplete and therefore may not be the only risks to which the Company is exposed. Additional risks and uncertainties could have a material adverse effect on the business and financial condition of the Company. The order of presentation of the risk factors below does not indicate the likelihood of their occurrence or the extent or the significance of the individual risks.

References in this section to “Biogen” or the “Company” shall mean Biogen Inc. and its consolidated subsidiaries, unless the context indicates otherwise.

Risks associated with Biogen’s business

Biogen is substantially dependent on revenues from its principal products.

The Company’s current revenues depend upon continued sales of its principal products. The Company may be substantially dependent on sales from its principal products for many years, including an increasing reliance on sales and growth of TECFIDERA as the Company continues to further expand into additional markets. Any of the following negative developments relating to any of the Company’s principal products may adversely affect the Company’s revenues and results of operations or could cause a decline in its stock price:

• safety or efficacy issues;

• the introduction or greater acceptance of competing products;

• constraints and additional pressures on product pricing or price increases, due to a number of factors, including governmental or regulatory requirements, increased competition, or changes in reimbursement policies and practices of payors and other third parties; or

• adverse legal, administrative, regulatory or legislative developments.

If Biogen fails to compete effectively, its business and market position would suffer.

The biopharmaceutical industry and the markets in which the Company operates are intensely competitive. The Company competes in the marketing and sale of its products, the development of new products and processes, the acquisition of rights to new products with commercial potential and the hiring and retention of personnel. The Company competes with biotechnology and pharmaceutical companies that have a greater number of products on the market and in the product pipeline, greater financial and other resources and other technological or competitive advantages. One or more of the Company’s competitors may benefit from significantly greater sales and marketing capabilities, may develop products that are accepted more widely than the Company’s or may receive patent protection that dominates, blocks or adversely affects the Company’s product development or business.

The Company’s products are also susceptible to competition from generics and biosimilars in many markets. Generic versions of drugs and biosimilars are likely to be sold at substantially lower prices than branded products. Accordingly, the introduction of generic or biosimilar versions of the Company’s marketed products likely would significantly reduce both the price that it receives for such marketed products and the volume of products that it sells, which may have an adverse impact on the Company’s results of operations.

In the multiple sclerosis (“MS”) market, the Company faces intense competition as the number of products

and competitors continues to expand. Due to the Company’s significant reliance on sales of its MS products, its business may be harmed if the Company is unable to successfully compete in the MS market. More specifically, the Company’s ability to compete, maintain and grow its share in the MS market may be adversely affected due to a number of factors, including:

• the introduction of more efficacious, safer, less expensive or more convenient alternatives to the Com- pany’s MS products, including its own products and products of its collaborators;

• the introduction of lower-cost biosimilars, follow-on products or generic versions of branded MS products sold by the Company’s competitors, and the possibility of future competition from generic versions or prodrugs of existing therapeutics or from off-label use by physicians of therapies indicated for other conditions to treat MS patients;

• patient dynamics, including the size of the patient population and the Company’s ability to attract new patients to its therapies;

• damage to physician and patient confidence in any of the Company’s MS products or to its sales and reputation as a result of label changes or adverse experiences or events that may occur with patients treated with its MS products;

• inability to obtain appropriate pricing and reimbursement for the Company’s MS products compared to its competitors in key international markets; or

• the Company’s ability to obtain and maintain patent, data or market exclusivity for its MS products.

Similarly, the hemophilia treatment market is highly competitive, with current treatments marketed by companies that have substantially greater financial resources and marketing expertise. The Company’s ability to successfully compete in the hemophilia market and gain share in this market may be adversely affected due to a number of reasons, including:

• difficulty in penetrating this market if the Company’s therapies are not regarded as offering substantial benefits over current treatments;

• the introduction by other companies of longer-lasting or more efficacious, safer, less expensive or more convenient treatments than the Company’s therapies;

• the Company’s limited marketing experience within the hemophilia treatment market, which may impact its ability to develop well-established relationships with the associated medical and scientific community; or

• if one of several companies that are working to develop additional treatments for hemophilia obtains marketing approval of its treatment in the European Union (“E.U.”) before the Company does, its applications with the European Medicines Agency (“EMA”) could be barred under operation of the EMA’s Orphan Medicines Regulation.

Sales of Biogen’s products depend, to a significant extent, on adequate coverage, pricing and reimbursement from third party payors, which are subject to increasing and intense pressure from political, social, competitive and other sources. The Company’s inability to maintain adequate coverage, or a reduction in pricing or reimbursement, could have an adverse effect on its business, revenues and results of operations, and could cause a decline in the Company’s stock price.

Sales of the Company’s products are dependent, in large part, on the availability and extent of coverage, pricing and reimbursement from government health administration authorities, private health insurers and other organizations. When a new pharmaceutical product is approved, the availability of government and private reimbursement for that product may be uncertain, as is the pricing and amount for which that product will be reimbursed.

Pricing and reimbursement for the Company’s products may be adversely affected by a number of factors, including:

• changes in federal, state or foreign government regulations or private third-party payors' reimbursement policies;

• pressure by employers on private health insurance plans to reduce costs; and

• consolidation and increasing assertiveness of payors, including managed care organizations, health insurers, pharmacy benefit managers, government health administration authorities, private health insurers and other organizations, seeking price discounts or rebates in connection with the placement of the Company’s products on their formularies and, in some cases, the imposition of restrictions on access or coverage of particular drugs or pricing determined based on perceived value.

The Company’s ability to set the price for its products can vary significantly from country to country and as a result so can the price of its products. Certain countries set prices by reference to the prices in other countries where the Company’s products are marketed. Thus, the Company’s inability to secure adequate prices in a particular country may not only limit the marketing of its products within that country, but may also adversely affect its ability to obtain acceptable prices in other markets. This may create the opportunity for third party cross-border trade or influence the Company’s decision to sell or not to sell a product, thus adversely affecting its geographic expansion plans and revenues.

The Company’s failure to maintain adequate coverage, pricing, or reimbursement for its products would have an adverse effect on its business, revenues and results of operation, could curtail or eliminate its ability to adequately fund research and development programs for the discovery and commercialization of new products, and could cause a decline in the Company’s stock price.

Drug prices are under significant scrutiny in the markets in which the Company’s products are prescribed. Drug pricing and other health care costs continue to be subject to intense political and societal pressures which the Company anticipates will continue and escalate on a global basis. As a result, Biogen’s business and reputation may be harmed, the Company’s stock price may be adversely impacted and experience periods of volatility, and the Company’s results of operations may be adversely impacted.

Biogen’s results of operations may be adversely affected by current and potential future healthcare reforms.

In the United States (“U.S.”), federal and state legislatures, health agencies and third-party payors continue to focus on containing the cost of health care. Legislative and regulatory proposals and enactments to reform health care insurance programs could significantly influence the manner in which the Company’s products are prescribed and purchased. For example, provisions of the Patient Protection and Affordable Care Act (“PPACA”) have resulted in changes in the way health care is paid for by both governmental and private insurers, including increased rebates owed by manufacturers under the Medicaid Drug Rebate Pro- gram, annual fees and taxes on manufacturers of certain branded prescription drugs, the requirement that manufacturers participate in a discount program for certain outpatient drugs under Medicare Part D and the expansion of the number of hospitals eligible for discounts under Section 340B of the Public Health Ser- vice Act. These changes have had and are expected to continue to have a significant impact on the Compa- ny’s business.

There is also significant economic pressure on state budgets that may result in states increasingly seeking to achieve budget savings through mechanisms that limit coverage or payment for the Company’s drugs. In recent years, some states have considered legislation and ballot initiatives that would control the prices of drugs, including laws to allow importation of pharmaceutical products from lower cost jurisdictions outside the U.S. and laws intended to impose price controls on state drug purchases. State Medicaid programs are increasingly requesting manufacturers to pay supplemental rebates and requiring prior authorization by the state program for use of any drug for which supplemental rebates are not being paid. Government efforts to reduce Medicaid expenses may lead to increased use of managed care organizations by Medicaid programs. This may result in managed care organizations influencing prescription decisions for a larger segment of the population and a corresponding constraint on prices and reimbursement for the Company’s products. In addition, under the PPACA, as states implement their health care marketplaces or operate under the federal exchange, the impact on drug manufacturers, including the Company, will depend in part on the formulary and benefit design decisions made by insurance sponsors or plans participating in these pro-

grams. It is possible that the Company may need to provide discounts or rebates to such plans in order to maintain favorable formulary access for its products for this patient population, which could have an adverse impact on the Company’s sales and results of operations.

In the E.U. and some other international markets, the government provides health care at low cost to con- sumers and regulates pharmaceutical prices, patient eligibility or reimbursement levels to control costs for the government-sponsored health care system. Many countries have announced or implemented measures to reduce health care costs to constrain their overall level of government expenditures. These measures vary by country and may include, among other things, patient access restrictions, suspensions on price increases, prospective and possibly retroactive price reductions and other recoupments and increased mandatory discounts or rebates, recoveries of past price increases, and greater importation of drugs from lower- cost countries to higher-cost countries. These measures have negatively impacted the Company’s revenues, and may continue to adversely affect its revenues and results of operations in the future.

Adverse safety events or restrictions on use and safety warnings for Biogen’s products can negatively affect its business, product sales and stock price.

Adverse safety events involving the Company’s marketed products may have a negative impact on its business. Discovery of safety issues with its products could create product liability and could cause additional regulatory scrutiny and requirements for additional labeling or safety monitoring, withdrawal of products from the market, and the imposition of fines or criminal penalties. Adverse safety events may also damage physician and patient confidence in the Company’s products and its reputation. Any of these could result in liabilities, loss of revenue, material write-offs of inventory, material impairments of intangible assets, goodwill and fixed assets, material restructuring charges and other adverse impacts on the Compa- ny’s results of operations.

Regulatory authorities are making greater amounts of stand-alone safety information directly available to the public through periodic safety update reports, patient registries and other reporting requirements. The reporting of adverse safety events involving the Company’s products or products similar to the Company’s and public rumors about such events may increase claims against the Company and may also cause its product sales or stock price to decline or experience periods of volatility.

Restrictions on use or significant safety warnings that may be required to be included in the label of the Company’s products, such as the risk of developing progressive multifocal leukoencephalopathy (“PML”), a serious brain infection, in the label for certain of the Company’s products, may significantly reduce expected revenues for those products and require significant expense and management time.

If Biogen is unable to obtain and maintain adequate protection for its data, intellectual property and other proprietary rights, its business may be harmed.

The Company’s success depends in part on its ability to obtain and defend patent and other intellectual property rights that are important to the commercialization of its products and product candidates. The degree of patent protection that will be afforded to the Company’s products and processes in the U.S. and in other important markets remains uncertain and is dependent upon the scope of protection decided upon by the patent offices, courts and lawmakers in these countries. The Company can provide no assurance that it will successfully obtain or preserve patent protection for the technologies incorporated into its products and processes, or that the protection obtained will be of sufficient breadth and degree to protect the Com- pany’s commercial interests in all countries where it conduct business. If the Company cannot prevent others from exploiting its inventions, the Company will not derive the benefit from them that it currently expects. Furthermore, the Company can provide no assurance that its products will not infringe patents or other intellectual property rights held by third parties.

The Company also relies on regulatory exclusivity for protection of its products. Implementation and enforcement of regulatory exclusivity, which may consist of regulatory data protection and market protection, varies widely from country to country. Failure to qualify for regulatory exclusivity, or failure to obtain or maintain the extent or duration of such protections that the Company expects in each of the markets for its products, due to challenges, changes or interpretations in the law or otherwise, could affect the

Company’s revenue for its products or its decision on whether to market its products in a particular country or countries or could otherwise have an adverse impact on the Company’s results of operations.

Litigation, interferences, oppositions, inter partes reviews or other proceedings are, have been and may in the future be necessary in some instances to determine the validity and scope of certain of the Company’s proprietary rights, and in other instances to determine the validity, scope or non-infringement of certain patent rights claimed by third parties to be pertinent to the manufacture, use or sale of its products. The Company may also face challenges to its patent and regulatory protections covering its products by manufacturers of generics and biosimilars that may choose to launch or attempt to launch their products before the expiration of the Company’s patent or regulatory exclusivity. Litigation, interference, oppositions, inter partes reviews or other similar types of proceedings are unpredictable and may be protracted, expensive and distracting to management. The outcome of such proceedings could adversely affect the validity and scope of the Company’s patent or other proprietary rights, hinder its ability to manufacture and market its products, require the Company to seek a license for the infringed product or technology or result in the assessment of significant monetary damages against it that may exceed amounts, if any, accrued in the Company’s financial statements. An adverse determination in a judicial or administrative proceeding or a failure to obtain necessary licenses could prevent the Company from manufacturing or selling its products. Furthermore, payments under any licenses that the Company is able to obtain would reduce its profits derived from the covered products and services.

Biogen's long-term success depends upon the successful development of new products and additional indications for existing products.

The Company’s long-term viability and growth will depend upon successful development of additional indications for its existing products as well as successful development of new products and technologies from its research and development activities, the Company’s biosimilars joint venture with Samsung Bio- logics or licenses or acquisitions from third parties.

Product development is very expensive and involves a high degree of risk. Only a small number of research and development programs result in the commercialization of a product. Clinical trials may indicate that the Company’s product candidates lack efficacy, have harmful side effects, result in unexpected adverse events, or raise other concerns that may significantly reduce the likelihood of regulatory approval. This may result in significant restrictions on use and safety warnings in an approved label, adverse placement within the treatment paradigm, or significant reduction in the commercial potential of the product candidate.

Clinical trials and the development of biopharmaceutical products is a lengthy and complex process. If Biogen fails to adequately manage its clinical activities, its clinical trials or potential regulatory approvals may be delayed or denied.

Conducting clinical trials is a complex, time-consuming and expensive process. The Company's ability to complete clinical trials in a timely fashion depends in large part on a number of key factors. These factors include protocol design, regulatory and institutional review board approval, patient enrollment rates, and compliance with extensive current Good Clinical Practices. If the Company or its third party clinical trial providers or third party contract research organizations, or CROs, do not successfully carry out these clinical activities, the Company's clinical trials or the potential regulatory approval of a product candidate may be delayed or be unsuccessful.

The Company has opened clinical sites and is enrolling patients in a number of countries where its experience is more limited. In most cases, the Company uses the services of third parties to carry out its clinical trial related activities and rely on such parties to accurately report their results. The Company's reliance on third parties for these activities may impact its ability to control the timing, conduct, expense and quality of the Company's clinical trials. One CRO has responsibility for substantially all of the Company's clinical trial related activities and reporting. If this CRO does not adequately perform, many of the Company's trials may be affected. The Company may need to replace its CROs. Although the Company believes there are a number of other CROs the Company could engage to continue these activities, the replacement of an

existing CRO may result in the delay of the affected trials or otherwise adversely affect its efforts to obtain regulatory approvals and commercialize its product candidates.

Successful preclinical work or early stage clinical trials does not ensure success in later stage trials, regulatory approval or commercial viability of a product.

Positive results in a trial may not be replicated in subsequent or confirmatory trials. Additionally, success in preclinical work or early stage clinical trials does not ensure that later stage or larger scale clinical trials will be successful or that regulatory approval will be obtained. In addition, even if later stage clinical trials are successful, regulatory authorities may delay or decline approval of the Company’s product candidates. Regulatory authorities may disagree with its view of the data, require additional studies or disagree with the Company’s trial design or endpoints. Regulatory authorities may also fail to approve the facilities or the processes used to manufacture a product candidate, the Company’s dosing or delivery methods or companion devices. Regulatory authorities may grant marketing approval that is more restricted than anticipated. These restrictions may include limiting indications to narrow patient populations and the imposition of safety monitoring, educational requirements and risk evaluation and mitigation strategies. The occurrence of any of these events could result in significant costs and expenses, have an adverse effect on the Company’s business, financial condition and results of operations and could cause its stock price to decline or experience periods of volatility.

Even if the Company is able to successfully develop new products or indications, sales of new products or products with additional indications may not meet investor expectations. The Company may also make a strategic decision to discontinue development of a product or indication if, for example, the Company believes commercialization will be difficult relative to the standard of care or other opportunities in its pipeline.

Manufacturing issues could substantially increase Biogen’s costs, limit supply of its products and reduce its revenues.

The process of manufacturing the Company’s products is complex, highly regulated and subject to numerous risks, including:

• Risk of Product Loss. The manufacturing process for the Company’s products is extremely susceptible to product loss due to contamination, oxidation, equipment failure or improper installation or operation of equipment, or vendor or operator error. Even minor deviations from normal manufacturing processes could result in reduced production yields, product defects and other supply disruptions. If microbial, viral or other contaminations are discovered in the Company’s products or manufacturing facilities, it may need to close its manufacturing facilities for an extended period of time to investigate and remedi- ate the contaminant.

• Risks of Reliance on Third Parties and Single Source Providers. The Company relies on third-party suppliers and manufacturers for many aspects of its manufacturing process, for its products and product candidates. In some cases, due to the unique manner in which the Company’s products are manufac- tured, the Company relies on single source providers of several raw materials and manufacturing sup- plies. These third parties are independent entities subject to their own unique operational and financial risks that are outside of the Company’s control. These third parties may not perform their obligations in a timely and cost-effective manner or in compliance with applicable regulations, and they may be unable or unwilling to increase production capacity commensurate with demand for the Company’s existing or future products. Finding alternative providers could take a significant amount of time and involve significant expense due to the specialized nature of the services and the need to obtain regulatory approval of any significant changes to the Company’s suppliers or manufacturing methods. Biogen cannot be certain that it could reach agreement with alternative providers or that the U.S. Food and Drug Administration (“FDA”) or other regulatory authorities would approve the Company’s use of such alternatives.

• Global Bulk Supply Risks. The Company relies on its manufacturing facilities in Cambridge, Massa- chusetts, Research Triangle Park, North Carolina and Hillerød, Denmark for the production of drug substance for its large molecule products and product candidates. The Company’s global bulk supply of

these products and product candidates depends on the uninterrupted and efficient operation of these facilities, which could be adversely affected by equipment failures, labor shortages, natural disasters, power failures and numerous other factors.

• Risks Relating to Compliance with Current Good Manufacturing Practices (“cGMP”). The Company and its third-party providers are generally required to maintain compliance with cGMP and other strin- gent requirements and are subject to inspections by the FDA and comparable agencies in other jurisdictions to confirm such compliance. Any delay, interruption or other issues that arise in the manufacture, fill-finish, packaging, or storage of the Company’s products as a result of a failure of the Company’s facilities or the facilities or operations of third parties to pass any regulatory agency inspection could significantly impair the Company’s ability to develop and commercialize its products. Significant noncompliance could also result in the imposition of monetary penalties or other civil or criminal sanctions and damage the Company’s reputation.

Any adverse developments affecting the Company’s manufacturing operations or the operations of its third-party suppliers and manufacturers may result in shipment delays, inventory shortages, lot failures, product withdrawals or recalls, or other interruptions in the commercial supply of its products. The Com- pany may also have to take inventory write-offs and incur other charges and expenses for products that fail to meet specifications, undertake costly remediation efforts or seek more costly manufacturing alternatives. Such developments could increase the Company’s manufacturing costs, cause it to lose revenue or market share as patients and physicians turn to competing therapeutics, diminish its profitability or damage its reputation.

Biogen depends on relationships with collaborators and other third-parties for revenue, and the development, regulatory approval, commercialization and marketing of certain products, which are outside of its full control.

The Company relies on a number of significant collaborative relationships for revenue, and the development, regulatory approval, commercialization, and marketing of certain of its products and product candidates. Reliance on collaborative relationships subjects it to a number of risks, including:

• the Company may be unable to control the resources its collaborator devotes to its programs or products;

• disputes may arise with respect to ownership of rights to technology developed with its collaborator, and the underlying contract with its collaborator may fail to provide significant protection or may fail to be effectively enforced if the collaborator fails to perform;

• the Company’s collaborator’s interests may not always be aligned with the Company’s interests and a collaborator may not pursue regulatory approvals or market a product in the same manner or to the same extent that the Company would, which could adversely affect the Company’s revenues;

• collaborations often require the parties to cooperate, and failure to do so effectively could adversely affect product sales by the Company’s collaborator or the clinical development or regulatory approvals of products under joint control or could result in termination of the research, development or commercialization of product candidates or result in litigation or arbitration; and

• any failure on the part of the Company’s collaborator to comply with applicable laws and regulatory requirements in the marketing, sale and maintenance of the market authorization of the Company’s products or to fulfill any responsibilities the Company’s collaborator may have to protect and enforce any intellectual property rights underlying the Company’s products could have an adverse effect on the Company’s revenues as well as involve the Company in possible legal proceedings.

Given these risks, there is considerable uncertainty regarding the success of the Company’s current and future collaborative efforts. If these efforts fail, the Company’s product development or commercialization of new products could be delayed or revenues from products could decline.

The Company may fail to achieve the expected financial and operating benefits of its corporate restructuring and the restructuring may harm its business and financial results.

The Company faces significant risks associated with its corporate restructuring actions that may impair its ability to achieve anticipated savings and operational efficiencies or that may otherwise harm its business. These risks include loss of workforce capabilities, loss of continuity, decreases in employee focus and mo- rale, attrition of necessary or key employees, higher than anticipated separation expenses, litigation and the failure to meet financial and operational targets. In addition, the calculation of the anticipated cost savings and other benefits resulting from the Company’s corporate restructuring actions are subject to many estimates and assumptions. These estimates and assumptions are subject to significant business, economic, competitive and other uncertainties and contingencies, many of which are beyond the Company’s control. If these estimates and assumptions are incorrect or if the Company experiences delays or unforeseen events, the Company’s business and financial results could be adversely affected.

Biogen’s business may be adversely affected if the Company does not manage its current growth and does not successfully execute its growth initiatives.

The Company anticipates growth through internal development projects, commercial initiatives and external opportunities, which may include the acquisition, partnering and in-licensing of products, technologies and companies or the entry into strategic alliances and collaborations. The availability of high quality development opportunities is limited and competitive, and it is not certain that the Company will be able to identify candidates that the Company and its shareholders consider suitable or complete transactions on terms that are acceptable to it and its shareholders. The Company may fail to complete transactions for other reasons, including if the Company is unable to obtain desired financing on favorable terms, if at all. Even if the Company is able to successfully identify and complete acquisitions and other strategic alliances and collaborations, it may face unanticipated costs or liabilities in connection with the transaction or it may not be able to integrate them or take full advantage of them or otherwise realize the benefits that it expects.

To manage the Company’s current and future potential growth effectively, the Company needs to continue to enhance its operational, financial and management processes and to expand, train and manage its employee base. The Company’s growth is also dependent upon its ability to attract and retain qualified scientific, information technology, manufacturing, sales and marketing and executive personnel and to develop and maintain relationships with qualified clinical researchers and key distributors in a highly competitive environment. The Company may face difficulty in attracting and retaining key talent for a number of reasons, such as the underperformance or discontinuation of one or more late stage programs or recruitment by competitors.

Supporting the Company’s growth initiatives and the further development of its existing products and potential new products in its pipeline will require significant capital expenditures and management resources, including investments in research and development, sales and marketing, manufacturing capabilities and other areas of its business. If the Company does not successfully manage its current growth and does not successfully execute its growth initiatives, then the Company’s business and financial results may be adversely affected and it may incur asset impairment or restructuring charges.

A breakdown or breach of Biogen’s technology systems could subject it to liability or interrupt the operation of its business.

The Company is increasingly dependent upon technology systems and data. The Company’s computer systems continue to increase in multitude and complexity due to the growth in its business, making them potentially vulnerable to breakdown, malicious intrusion and random attack. Likewise, data privacy or security breaches by individuals authorized to access its technology systems or others may pose a risk that sensitive data, including intellectual property, trade secrets or personal information belonging to the Com- pany, its patients, customers or other business partners, may be exposed to unauthorized persons or to the public. Cyber-attacks are increasing in their frequency, sophistication and intensity. While the Company continues to build and improve its systems and infrastructure and believes it has taken appropriate security measures to reduce these risks to its data and technology systems, there can be no assurance that its efforts will prevent breakdowns or breaches in its systems that could adversely affect the Company’s business or

operations.

If Biogen fails to comply with the extensive legal and regulatory requirements affecting the health care industry, it could face increased costs, penalties and a loss of business.

The Company’s activities, and the activities of its collaborators, distributors and other third party providers, are subject to extensive government regulation and oversight both in the U.S. and in foreign jurisdictions. The FDA and comparable agencies in other jurisdictions directly regulate many of the Company’s most critical business activities, including the conduct of preclinical and clinical studies, product manufacturing, advertising and promotion, product distribution, adverse event reporting and product risk management. The Company’s interactions in the U.S. or abroad with physicians and other health care providers that prescribe or purchase its products are also subject to government regulation designed to prevent fraud and abuse in the sale and use of the products and place greater restrictions on the marketing practices of health care companies. Health care companies such as the Company are facing heightened scrutiny of their relationships with health care providers from anti-corruption enforcement officials. In addition, the Com- pany along with many other pharmaceutical and biotechnology companies has been the target of lawsuits and investigations alleging violations of government regulation, including claims asserting submission of incorrect pricing information, impermissible off-label promotion of pharmaceutical products, payments intended to influence the referral of health care business, submission of false claims for government reimbursement, antitrust violations, or violations related to environmental matters. These risks may be heightened as the Company continues to expand its global operations enter new therapeutic areas with different patient populations, which may have product distribution methods differing from those the Company currently utilizes.

Regulations governing the health care industry are subject to change, with possibly retroactive effect, including:

• new laws, regulations or judicial decisions, or new interpretations of existing laws, regulations or decisions, related to health care availability, pricing or marketing practices, compliance with wage and hour laws and other employment practices, method of delivery, payment for health care products and services, compliance with health information and data privacy and security laws and regulations, tracking and reporting payments and other transfers of value made to physicians and teaching hospitals, extensive anti-bribery and anti-corruption prohibitions, product serialization and labeling requirements, and used product take-back requirements;

• changes in the FDA and foreign regulatory approval processes that may delay or prevent the approval of new products and result in lost market opportunity;

• requirements that provide for increased transparency of clinical trial results and quality data, such as the EMA’s clinical transparency policy, which could impact the Company’s ability to protect trade secrets and competitively-sensitive information contained in approval applications or could be misinter- preted leading to reputational damage, misperception or legal action which could harm the Company’s business; and

• changes in FDA and foreign regulations that may require additional safety monitoring, labeling changes, restrictions on product distribution or use, or other measures after the introduction of the Company’s products to market, which could increase the Company’s costs of doing business, adversely affect the future permitted uses of approved products, or otherwise adversely affect the market for the Company’s products.

Violations of governmental regulation may be punishable by criminal and civil sanctions against the Com- pany, including fines and civil monetary penalties and exclusion from participation in government programs, including Medicare and Medicaid, as well as against executives overseeing the Company’s business. In addition to penalties for violation of laws and regulations, the Company could be required to repay amounts it received from government payors, or pay additional rebates and interest if the Company is found to have miscalculated the pricing information it has submitted to the government. Whether or not the Company has complied with the law, an investigation into alleged unlawful conduct could increase its expenses, damage its reputation, divert management time and attention and adversely affect its business.

The Company’s indebtedness could adversely affect its business and limit its ability to plan for or respond to changes in its business.

The Company’s indebtedness, together with its significant contingent liabilities, including milestone and royalty payment obligations, could have important consequences to its business; for example, such obligations could:

• increase the Company’s vulnerability to general adverse economic and industry conditions;

• limit the Company’s ability to access capital markets and incur additional debt in the future;

• require the Company to dedicate a substantial portion of its cash flow from operations to payments on its indebtedness, thereby reducing the availability of its cash flow for other purposes, including business development efforts, research and development and mergers and acquisitions; and

• limit the Company’s flexibility in planning for, or reacting to, changes in its business and the industry in which the Company operates, thereby placing the Company at a competitive disadvantage compared to its competitors that have less debt.

Biogen’s sales and operations are subject to the risks of doing business internationally.

The Company is increasing its presence in international markets, particularly emerging markets, subjecting it to many risks that could adversely affect its business and revenues, such as:

• the inability to obtain necessary foreign regulatory or pricing approvals of products in a timely manner;

• collectability of accounts receivable;

• fluctuations in foreign currency exchange rates, in particular the recent strength of the U.S. dollar ver- sus foreign currencies which has adversely impacted the Company's revenues and net income;

• difficulties in staffing and managing international operations;

• the imposition of governmental controls;

• less favorable intellectual property or other applicable laws;

• increasingly complex standards for complying with foreign laws and regulations that may differ substantially from country to country and may conflict with corresponding U.S. laws and regulations;

• the far-reaching anti-bribery and anti-corruption legislation in the U.K., including the U.K. Bribery Act 2010, and elsewhere and escalation of investigations and prosecutions pursuant to such laws;

• compliance with complex import and export control laws;

• restrictions on direct investments by foreign entities and trade restrictions;

• greater political or economic instability; and

• changes in tax laws and tariffs.

In addition, the Company’s international operations are subject to regulation under U.S. law. For example, the Foreign Corrupt Practices Act prohibits U.S. companies and their representatives from offering, prom- ising, authorizing or making payments to foreign officials for the purpose of obtaining or retaining business abroad. In many countries, the health care professionals the Company regularly interacts with may meet the definition of a foreign government official for purposes of the Foreign Corrupt Practices Act. Failure to comply with domestic or foreign laws could result in various adverse consequences, including: possible delay in approval or refusal to approve a product; recalls, seizures or withdrawal of an approved product from the market; disruption in the supply or availability of the Company’s products or suspension of export or import privileges; the imposition of civil or criminal sanctions; the prosecution of executives

overseeing the Company’s international operations; and damage to its reputation. Any significant impairment of the Company’s ability to sell products outside of the U.S. could adversely impact the Company’s business and financial results.

Biogen’s effective tax rate may fluctuate and it may incur obligations in tax jurisdictions in excess of accrued amounts.

As a global biopharmaceutical company, the Company is subject to taxation in numerous countries, states and other jurisdictions. As a result, the Company’s effective tax rate is derived from a combination of applicable tax rates in the various places that it operates. In preparing its financial statements, the Company estimates the amount of tax that will become payable in each of such places. The Company’s effective tax rate, however, may be different than experienced in the past due to numerous factors, including changes in the mix of its profitability from country to country, the results of examinations and audits of its tax filings, adjustments to the value of the Company’s uncertain tax positions, changes in accounting for income taxes and changes in tax laws. Any of these factors could cause it to experience an effective tax rate significantly different from previous periods or the Company’s current expectations.

In addition, the Company’s inability to secure or sustain acceptable arrangements with tax authorities and future changes in the tax laws, among other things, may result in tax obligations in excess of amounts accrued in its financial statements.

In the U.S., there are several proposals under consideration to reform tax law, including proposals that may reduce or eliminate the deferral of U.S. income tax on the Company’s unrepatriated earnings, penalize certain transfer pricing structures, and reduce or eliminate certain foreign or domestic tax credits or deductions. The Company’s future reported financial results may be adversely affected by tax law changes which restrict or eliminate certain foreign tax credits or its ability to deduct expenses attributable to foreign earnings, or otherwise affect the treatment of its unrepatriated earnings.

In addition to U.S. tax reform proposals, the adoption of some or all of the recommendations set forth in the Organization for Economic Co-operation and Development’s project on Base Erosion and Profit Shift- ing (“BEPS”) by tax authorities in the countries in which the Company operates, could negatively impact its effective tax rate. These recommendations focus on payments from affiliates in high tax jurisdictions to affiliates in lower tax jurisdictions and the activities that give rise to a taxable presence in a particular country.

Biogen’s operating results are subject to significant fluctuations.

The Company’s quarterly revenues, expenses and net income (loss) have fluctuated in the past and are likely to fluctuate significantly in the future due to the risks described in these “Risk Factors” as well as the timing of charges and expenses that the Company may take. The Company has recorded, or may be required to record, charges that include:

• the cost of restructurings;

• impairments with respect to investments, fixed assets and long-lived assets, including in-process research and development and other intangible assets;

• inventory write-downs for failed quality specifications, charges for excess or obsolete inventory and charges for inventory write downs relating to product suspensions, expirations or recalls;

• changes in the fair value of contingent consideration;

• bad debt expenses and increased bad debt reserves;

• outcomes of litigation and other legal or administrative proceedings, regulatory matters and tax matters;

• milestone payments under license and collaboration agreements; and

• payments in connection with acquisitions and other business development activities.

The Company’s revenues are also subject to foreign exchange rate fluctuations due to the global nature of its operations. Although the Company has foreign currency forward contracts to hedge specific forecasted transactions denominated in foreign currencies, its efforts to mitigate the impact of fluctuating currency exchange rates may not be successful. As a result, currency fluctuations among the Company’s reporting currency, the U.S. dollar, and the currencies in which it does business will affect its operating results, often in unpredictable ways. The Company’s net income may also fluctuate due to the impact of charges it may be required to take with respect to foreign currency hedge transactions. In particular, the Company may incur higher than expected charges from hedge ineffectiveness or from the termination of a hedge relation- ship.

The Company’s operating results during any one period do not necessarily suggest the anticipated results of future periods.

Biogen is pursuing opportunities to expand its manufacturing capacity for future clinical and commercial requirements for product candidates, which will result in the incurrence of significant investment with no assurance that such investment will be recouped.

While the Company believes it currently has sufficient manufacturing capacity to meet its near-term manufacturing requirements, it is probable that it would need additional manufacturing capacity to support future clinical and commercial manufacturing requirements for product candidates in the Company’s pipeline, if such candidates are successful and approved. The Company recently announced its intent to build a biologics manufacturing facility in Solothurn, Switzerland and the acquisition of an additional manufacturing facility in Research Triangle Park, North Carolina. Due to the long lead times necessary for the expansion of manufacturing capacity, the Company expects to incur significant investment to build or expand its facilities or obtain third-party contract manufacturers with no assurance that such investment will be recouped. If the Company is unable to adequately and timely manufacture and supply its products and product candidates or if it does not fully utilize its manufacturing facilities, the Company’s business may be harmed.

The Company’s investment in Samsung Bioepis and its success in commercializing biosimilars developed by Samsung Bioepis are subject to risks and uncertainties inherent in the development, manufacture and commercialization of biosimilars.

The Company’s investment in Samsung Bioepis and its success in commercializing biosimilars developed by Samsung Bioepis are subject to a number of risks, including:

• Reliance on Third Parties. The Company is dependent on the efforts of Samsung Bioepis and other third parties over whom it has limited or no control in the development and manufacturing of biosimilars products. If Samsung Bioepis or such other third parties fail to perform successfully, the Company may not realize the anticipated benefits of its investment in Samsung Bioepis;

• Regulatory Compliance. Biosimilar products may face regulatory hurdles or delays due to the evolving and uncertain regulatory and commercial pathway of biosimilars products in certain jurisdictions;

• Intellectual Property and Regulatory Challenges. Biosimilar products may face extensive patent clear- ances, patent infringement litigation, injunctions, or regulatory challenges, which could prevent the commercial launch of a product or delay it for many years;

• Failure to Gain Market and Patient Acceptance. Market success of biosimilar products will be adversely affected if patients, physicians and payers do not accept biosimilar products as safe and efficacious products offering a more competitive price or other benefit over existing therapies; and

• Competitive Challenges. Biosimilar products face significant competition, including from innovator products and from biosimilar products offered by other companies. In some jurisdictions, local tender- ing processes may restrict biosimilar products from being marketed and sold in those jurisdictions. The number of competitors in a jurisdiction, the timing of approval, and the ability to market biosimilar products successfully in a timely and cost-effective matter are additional factors that may impact the Company’s success and/or the success of Samsung Bioepis in this business area.

Biogen’s investments in properties may not be fully realized.

The Company owns or leases real estate primarily consisting of buildings that contain research laborato- ries, office space, and manufacturing operations. For strategic or other operational reasons, the Company may decide to further consolidate or co-locate certain aspects of its business operations or dispose of one or more of its properties, some of which may be located in markets that are experiencing high vacancy rates and decreasing property values. If the Company determines that the fair value of any of its owned properties is lower than their book value it may not realize the full investment in these properties and incur significant impairment charges. If the Company decides to fully or partially vacate a leased property, it may incur significant cost, including lease termination fees, rent expense in excess of sublease income and impairment of leasehold improvements. Any of these events may have an adverse impact on the Compa- ny’s results of operations.

Biogen’s portfolio of marketable securities is subject to market, interest and credit risk that may reduce its value.

The Company maintains a portfolio of marketable securities for investment of its cash. Changes in the value of the Company’s portfolio of marketable securities could adversely affect its earnings. In particular, the value of the Company’s investments may decline due to increases in interest rates, downgrades of the bonds and other securities included in its portfolio, instability in the global financial markets that reduces the liquidity of securities included in its portfolio, declines in the value of collateral underlying the securities included in the Company’s portfolio, and other factors. Each of these events may cause the Company to record charges to reduce the carrying value of its investment portfolio or sell investments for less than its acquisition cost. Although the Company attempts to mitigate these risks through diversification of its investments and continuous monitoring of its portfolio’s overall risk profile, the value of the Company’s investments may nevertheless decline.

Biogen may not be able to access the capital and credit markets on terms that are favorable to it.

The Company may seek access to the capital markets to supplement its existing funds and cash generated from operations for working capital, capital expenditure and debt service requirements, and other business initiatives. The capital and credit markets have experienced extreme volatility and disruption which leads to uncertainty and liquidity issues for both borrowers and investors. In the event of adverse capital and credit market conditions, the Company may be unable to obtain capital market financing on favorable terms. Changes in credit ratings issued by nationally recognized credit rating agencies could also adversely affect its cost of financing and the market price of its securities.

Biogen’s business involves environmental risks, which include the cost of compliance and the risk of contamination or injury.

The Company’s business and the business of several of its strategic partners involve the controlled use of hazardous materials, chemicals, biologics and radioactive compounds. Although the Company believes that its safety procedures for handling and disposing of such materials comply with state, federal and foreign standards, there will always be the risk of accidental contamination or injury. If the Company were to become liable for an accident, or if it were to suffer an extended facility shutdown, the Company could incur significant costs, damages and penalties that could harm its business. Manufacturing of the Compa- ny’s products and product candidates also requires permits from government agencies for water supply and wastewater discharge. If the Company does not obtain appropriate permits, including permits for sufficient quantities of water and wastewater, it could incur significant costs and limits on its manufacturing volumes that could harm its business.

The illegal distribution and sale by third parties of counterfeit versions of Biogen’s products or stolen products could have a negative impact on its reputation and business.

Third parties might illegally distribute and sell counterfeit or unfit versions of the Company’s products, which do not meet its rigorous manufacturing, distribution and testing standards. A patient who receives a counterfeit or unfit drug may be at risk for a number of dangerous health consequences. Stolen inventory that is not properly stored or is sold through unauthorized channels could adversely impact the patient safe-

ty, the Company’s reputation and its business. The Company’s reputation and business could suffer harm as a result of counterfeit or unfit drugs sold under its brand name.

The increasing use of social media platforms presents new risks and challenges.

Social media is increasingly being used to communicate about the Company’s products and the diseases its therapies are designed to treat. Social media practices in the biopharmaceutical industry continue to evolve and regulations relating to such use are not always clear. This evolution creates uncertainty and risk of noncompliance with regulations applicable to its business. For example, patients may use social media channels to comment on the effectiveness of a product or to report an alleged adverse event. When such disclosures occur, there is a risk that the Company fails to monitor and comply with applicable adverse event reporting obligations or the Company may not be able to defend the Company or the public’s legiti- mate interests in the face of the political and market pressures generated by social media due to restrictions on what the Company may say about its products. There is also a risk of inappropriate disclosure of sensitive information or negative or inaccurate posts or comments about it on any social networking website. If any of these events were to occur or the Company otherwise fails to comply with applicable regulations, it could incur liability, face overly restrictive regulatory actions or incur other harm to its business.

Risks associated with Biogen’s shares of common stock

The marketability of Biogen’s shares of common stock may fluctuate and may decline below the purchase price of the shares acquired under the ESPP.

The Company cannot assure that the marketability of its common stock will remain consistent. The market price of the Company’s common stock may fluctuate widely, depending on many factors beyond the Com- pany’s control. These factors include, amongst other things, the factors stated above under “Risks associated with Biogen’s business”, in particular risks associated with its dependency on revenues from its principal products (p. 29), risks relating to obtaining and protecting data, intellectual property and other proprietary rights (pp. 30), risks related to its preclinical work or early stage clinical trials (p. 31), adverse safety events or restrictions on use and safety warnings for Biogen’s products (pp. 31) and risks in connection with the pricing or reimbursement of its products (pp. 32), actual or anticipated variations in operating results and earnings by the Company and/or its competitors, changes in financial estimates by securities ana- lysts, market conditions in the healthcare industry and, in general, the status of the securities market, governmental legislation and regulations, as well as general economic and market conditions, such as reces- sion. These may cause the market price and demand for the common stock to fluctuate substantially and any such development, if adverse, may have an adverse effect on the market price of the Company’s common stock which may decline disproportionately to its operating performance.

The market price of the Company’s common stock is also subject to fluctuation in response to any further issuance of shares by the Company, sales of shares of the Company by its major shareholders, the liquidity of trading in the Company’s common stock, capital reduction or purchases of shares by the Company and investor perception. As a result of these, the public trading price of the Company’s common stock may decline below the purchase price of shares acquired under the ESPP.

Biogen can provide no assurance that it will continue to repurchase stock or that its will repurchase stock at favorable prices.

The Company’s Board of Directors has approved stock repurchase programs and may approve additional repurchase programs in the future. The amount and timing of stock repurchases are subject to capital availability and our determination that stock repurchases are in the best interest of the Company’s stockholders and are in compliance with all respective laws and the Company’s agreements applicable to the repurchase of stock. The Company’s ability to repurchase stock will depend upon, among other factors, its cash bal- ances and potential future capital requirements for strategic transactions, results of operations, financial condition, and other factors beyond the Company’s control that it may deem relevant. A reduction in, or the completion or expiration of, the Company’s stock repurchase programs could have a negative effect on the Company’s stock price. The Company can provide no assurance that it will repurchase stock at favorable prices, if at all.

The shareholding, voting rights and the earnings per ordinary share may be diluted as a result of an issuance of additional shares of Biogen.

The shareholding and voting rights, and the earnings per share of the Company’s common stock may be diluted as a result of an issuance of additional shares of the Company.

Some of Biogen’s collaboration agreements contain change in control provisions that may discourage a third party from attempting to acquire it.

Some of the Company’s collaboration agreements include change in control provisions that could reduce the potential acquisition price an acquirer is willing to pay or discourage a takeover attempt that could be viewed as beneficial to shareholders. Upon a change in control, some of these provisions could trigger reduced milestone, profit or royalty payments to the Company or give its collaboration partner rights to terminate the Company’s collaboration agreement, acquire operational control or force the purchase or sale of the programs that are the subject of the collaboration.

Biogen cannot assure employees participating in the ESPP that it will pay any dividends in the future.

The Company has not paid cash dividends since its inception. The Company does not have any current intention of paying any cash dividends in the near term.

GENERAL INFORMATION

Responsibility for Contents of the Prospectus

Biogen Inc., whose principal executive offices are located at 225 Binney Street, Cambridge, Massachusetts 02142, U.S.A., assumes responsibility for the contents of this prospectus pursuant to section 5 paragraph 4 of the German Securities Prospectus Act (Wertpapierprospektgesetz) and declares the information contained in this prospectus is, to the best of its knowledge, in accordance with the facts and contains no omission likely to affect its import, and that Biogen Inc. has taken all reasonable care to ensure that the information contained in this prospectus is, to the best of its knowledge, in accordance with the facts and contains no omission likely to affect its import.

References in this prospectus to “Biogen” or the “Company” shall mean Biogen Inc. and its consolidated subsidiaries, unless the context indicates otherwise.

Subject Matter of the Offering

This prospectus relates to the offering of shares of Biogen’s common stock each with a par value of USD 0.0005 under the ESPP. The total number of shares made available for purchase under the ESPP is 6,200,000.

Forward-Looking Statements

This prospectus contains forward-looking statements that are based on the Company’s current beliefs and expectations. These forward-looking statements may be accompanied by such words as “anticipate,” “believe,” “could,” “estimate,” “expect,” “forecast,” “intend,” “may,” “plan,” “potential,” “project,” “target,” “will” and other words and terms of similar meaning. Reference is made in particular to forward-looking statements regarding: future financial performance, results of operations and working capital; the inci- dence, timing, outcome and impact of litigation; proceedings related to patents and other intellectual property and proprietary rights; tax assessments and other legal proceedings; the outcome and impact of healthcare reform efforts and cost reduction measures; the development and commercialization of the Company’s pipeline products; and the Company’s outlook relating to its marketed and pipeline products, regulatory filings and actions, research and development investments, and manufacturing operations. These forward-looking statements involve risks and uncertainties that could cause actual results to differ materi- ally from those reflected in such statements, including those risks and uncertainties that are described in the “Risk Factors” section of this prospectus. Forward-looking statements speak only as of the date of this prospectus. You should not place undue reliance on these statements. The Company does not undertake any obligation to publicly update any forward-looking statements.

Currency References

In this prospectus and any documents included herein, unless otherwise indicated, all dollar amounts and references to “USD”, “U.S.$” or “$” are to U.S. Dollars.

Trademarks

ALPROLIX®, AVONEX®, BENEPALI®, ELOCTATE®, FLIXABI®, PLEGRIDY®, RITUXAN®, TECFIDERA®, and TYSABRI® are registered trademarks of Biogen. FUMADERMTM and ZINBRYTATM are trademarks of Biogen. Other trademarks referenced herein are the property of their respective owners.

Documents Available for Inspection

The Company’s internet address is www.biogen.com. The following documents, along with all other reports and amendments filed with or furnished to the U.S. Securities and Exchange Commission (“SEC”), are publicly available free of charge during the entire validity period of this prospectus on the Investors section of Biogen’s website:

 the Company’s Annual Report on Form 10-K for the fiscal year ended December 31, 2015 including its audited consolidated financial statements;

 the Company’s Annual Report on Form 10-K for the fiscal year ended December 31, 2014 including its audited consolidated financial statements; and

 the Company’s Annual Report on Form 10-K for the fiscal year ended December 31, 2013 including its audited consolidated financial statements.

These documents are also available on the SEC website at www.sec.gov. This prospectus can be down- loaded on Biogen’s website at https://www.biogen.com/en_us/careers/disclaimer-disclosure.html.

The Company’s certificate of incorporation and bylaws are available on file at the Company’s headquarters in Cambridge, Massachusetts, U.S.A. Hard copies of the Company’s certificate of incorporation and bylaws will be furnished to investors without charge upon written request to: Investor Relations, Biogen Inc., 225 Binney Street, Cambridge, Massachusetts 02142, U.S.A. or via oral request to: Investor Relations, Biogen Inc. at (+1) (617) 679 2442. They are further available online at the Corporate Governance subsection of the Company’s website at www.biogen.com.

THE OFFERING

Eligible Employees (please refer to the subheading Eligible Employee below for the definition of Eligible Employee) have the opportunity to acquire shares of Biogen’s common stock under the ESPP.

Information Concerning the Shares to be Offered

The shares offered under the ESPP are shares of Biogen’s common stock. The shares offered under the ESPP are registered under the U.S. Securities Act of 1933, as amended. The Company’s common stock is listed on the NASDAQ Global Select Market (“NASDAQ”), under the symbol “BIIB.” The stock is quoted on NASDAQ in USD. The International Securities Identification Number (“ISIN”) for the Company’s common stock is US09062X1037. The U.S. security identification (“CUSIP”) number for the Company’s common stock is 09062X103. The German Securities Code Number (Wertpapier-Kenn-Nummer) is 789617. In Germany, the stock is traded in the Open Market (Freiverkehr) on the exchanges in Frankfurt, Stuttgart, Berlin, Düsseldorf, Hamburg and Munich as well as on Tradegate under the symbol “IDP”.

The par value of each share of the Company’s common stock is USD 0.0005. All issued and outstanding shares of Biogen’s common stock are fully paid and non-assessable. Substantially all of the outstanding shares of common stock are registered and freely transferable. Each issued and outstanding share of common stock entitles the holder to one vote on all matters presented to the shareholders in annual or special meetings of the Company.

Biogen is authorized to issue up to 1,000,000,000 shares of common stock. As of December 31, 2015, the Company had 218,667,750 shares of common stock issued and outstanding.

A Participant (please refer to the subheading Purchase Rights and Purchase Price below for the definition of Participant) shall have no interest or voting right in the shares covered by his or her Purchase Right until the shares are purchased on the Participant’s behalf and the Participant has become a holder of record of the purchased shares.

The Offering under the ESPP

General Information

The ESPP was adopted by the Board of Directors on December 10, 2014 and approved by the Company’s shareholders on June 10, 2015, at which time the ESPP became effective. The ESPP is intended to enable Eligible Employees to use payroll deductions to acquire common stock in the Company at a discount to current market trading prices. The ESPP fosters broad-based stock ownership among Biogen employees.

Administration of the ESPP

The ESPP is administered by the Compensation and Management Development Committee of the Board of Directors (referred to as the “Plan Administrator”). The Plan Administrator has full authority to interpret and determine eligibility under the ESPP, prescribe forms, rules and procedures relating to the ESPP, and otherwise do all things necessary or appropriate to carry out the purposes of the ESPP. Decisions of the Plan Administrator are final and binding on all parties having interest in the ESPP.

The Company has designated Fidelity Investments® (“Fidelity”), as the ESPP services provider. Fidelity assists the Company with the administration of the ESPP.

Eligible Employee

An employee of Biogen or any of its designated subsidiaries who (i) customarily works more than five months per calendar year, (ii) customarily works 20 hours or more per week and (iii) satisfies the requirements in the ESPP, including the requirement to timely complete and submit the enrollment forms (including a payroll deduction authorization form), is eligible to participate in the ESPP (“Eligible Employee”). The Plan Administrator may establish additional eligibility requirements for offering periods that have not yet commenced.

Shares Available for Award

The maximum aggregate number of shares of common stock that have been authorized for issuance and available for purchase under the ESPP is 6,200,000.

If any Purchase Right (please refer to the subheading Purchase Rights and Purchase Price below for the definition of Purchase Right) granted under the ESPP expires or terminates for any reason without having been exercised in full or ceases for any reason to be exercisable in whole or in part, the unpurchased shares of common stock will again be available for purchase pursuant to offerings under the ESPP.

In the event of any change in the Company’s outstanding common stock by reason of a stock dividend, stock split, reverse stock split, split-up, recapitalization, merger, consolidation, reorganization, or other capital change, the aggregate number and type of shares available for purchase under the ESPP, the number and type of shares granted or purchasable during an offering period, and the purchase price per share under an outstanding Purchase Right will be appropriately adjusted.

If the total number of shares for which Purchase Rights are to be exercised exceeds the number of shares at the time available for issuance under the ESPP, then the Plan Administrator will make a pro-rata allocation of the available shares on a uniform and non-discriminatory basis, and any payroll deductions not applied to the purchase of the available shares will be refunded to the Participant.

Terms and Conditions

Offering Period

Unless otherwise determined by the Plan Administrator, shares of the Company’s common stock are offered for purchase under the ESPP through a series of successive three-month offering periods commencing on the first business day of each calendar quarter and ending on the last business day of each calendar quarter (“Offering Period”). The Plan Administrator may change the commencement date, the ending date and the duration of the Offering Periods to the extent permitted by law. The Offering Periods during the validity of this prospectus are April 1, 2016 to June 30, 2016, July 1, 2016 to September 30, 2016, October 1, 2016 to December 31, 2016 and January 1, 2017 to March 31, 2017.

Purchase Rights and Purchase Price

On the first day of an Offering Period, each participating Eligible Employee (“Participant”) automatically will be granted a right to purchase common stock (“Purchase Right”) on the last business day of each Of- fering Period (each, a “Purchase Date”). However, no employee may be granted a Purchase Right under the ESPP if, immediately after the Purchase Right is granted, the employee would own (or, under applicable statutory attribution rules, would be deemed to own) stock possessing 5% or more of the total combined voting power or value of all classes of stock of the Company or any of its subsidiaries.

The purchase price of shares of common stock issued pursuant to the exercise of a Purchase Right on the Purchase Date of an applicable Offering Period will be eighty-five percent (85%) of the lesser of (a) the Fair Market Value of a share of common stock on the first business day of the Offering Period and (b) the Fair Market Value of a share of common stock on the Purchase Date (“Purchase Price”). The Fair Market Value is the closing price of Biogen common stock as reported on the NASDAQ Global Select Market on the applicable date. If such day is not a trading day, the Fair Market Value will be the reported closing price for the immediately preceding day that is a trading day.

Exercise of Purchase Right

Each Purchase Right is automatically exercised on the Purchase Date and shares of the Company’s common stock are accordingly purchased on behalf of each Participant on each such Purchase Date. The Pur- chase Dates during the validity of the prospectus are June 30, 2016, September 30, 2016, December 31, 2016 and March 31, 2017. The purchase shall be effected by applying the Participant’s payroll deductions for the Offering Period ending on such Purchase Date to the purchase the greatest number of shares of the

Company’s common stock, including fractional shares that can be purchased with the Participant’s accumulated payroll deductions (subject to the limitation on the maximum number of shares purchasable per Participant on any one Purchase Date), at the Purchase Price for that Purchase Date.

Purchase Price Payment – Payroll Deduction

In general, the Purchase Price is paid by way of automatic deduction from the Participant’s’ payroll and used to purchase shares of the Company’s common stock at the end of each Offering Period. The Partici- pant authorizes the Company to make a payroll deduction up to a maximum of 10%, in 1% increments, of after-tax income per pay period. After-tax income includes regular base salary, overtime, shift differentials, annual bonuses, commissions and other sales incentives.

A Participant’s payroll deduction authorization will remain in effect for subsequent Offering Periods unless the Participant’s participation in the ESPP terminates or the Participant cancels the authorization or submits a new payroll deduction authorization form within the time specified by the Plan Administrator prior to the start of the subsequent Offering Period. During an Offering Period, a Participant may reduce the amount of his or her payroll deduction authorization one time, but may not increase it. If, during an Offering Period, a Participant reduces his or her payroll deduction authorization to zero percent (0%), payroll deductions previously accumulated during that Offering Period will be applied to purchase shares of common stock on the Purchase Date for that Offering Period and the Participant’s participation in the ESPP will then terminate.

Any amount of payroll deductions that are not used for the purchase of shares of common stock, whether because of the Participant’s withdrawal from participation in an Offering Period or for any other reason will be returned to the Participant, without interest, as soon as administratively practicable after such withdrawal or other event, as applicable.

A Participant may view an individual account balance and a detailed purchase history by contacting Fideli- ty Investments® (“Fidelity”), Biogen’s dedicated stock plan service provider, at (+1) 800-544-0275 or by going online to www.netbenefits.fidelity.com.

Purchase Limitations

A Participant may purchase up to – but not more than – USD 25,000 in Fair Market Value of the Compa- ny’s common stock per calendar year under the ESPP. The USD 25,000 limit includes Biogen’s company contribution via the discount, so each Participant’s maximum annual contribution amount is USD 21,250. Should a Participant reach the calendar year purchase limit, any payroll deductions in excess of the limit not used to purchase shares will be returned to the Participant, without interest, as soon as administratively practicable and future contributions will be stopped until the next calendar year. In addition to the USD 25,000 per calendar year purchase limit, each Participant is limited to purchasing no more than 2,500 shares on any Purchase Date. Should a Participant reach the 2,500 shares limit on any Purchase Date, any payroll deductions in excess of the limit not used to purchase shares will be returned to the Participant, without interest, as soon as administratively practicable. Contributions will continue in the next Offering Period, if the USD 25,000 annual purchase limit has not yet been met.

Delivery

Each Purchase Right is automatically exercised on the Purchase Date. The purchase shall be effected by applying the Participant's payroll deductions for the Offering Period, ending on such Purchase Date to the purchase of shares of the Company’s common stock. Hence, in general, the Purchase Price is paid by way of automatic deduction from the participating Eligible Employees’ payroll. As soon as practicable after each Purchase Date, which is generally within 7 to 10 days of the Purchase Date, the purchased shares will be delivered.

Shares issuable to employees within and outside the U.S. upon exercise of Purchase Rights are deposited into a designated brokerage account with Fidelity maintained on behalf of the Participant and held in “street name”, unless otherwise designated by the Plan Administrator.

Corporate Transactions

In the event of a consolidation, merger or similar transaction, a sale or transfer of all or substantially all of the Company’s assets, or a dissolution or liquidation of the Company, the Plan Administrator may, in its discretion, provide that each outstanding Purchase Right will be assumed or substituted for a right granted by the acquiror or successor corporation or by a parent or subsidiary of such entity, or will be cancelled with accumulated payroll deductions returned to each Participant, or that the Offering Period will end before the date of the proposed sale, merger or similar transaction.

Termination of Participation

The Participant may terminate his or her participation in Plan, by delivering a notice to the Plan Adminis- trator in accordance with the procedures established by, and in a form acceptable to, the Plan Administra- tor. To be effective with respect to an upcoming Purchase Date, the cancellation notice must be submitted no later than five (5) business days before such Purchase Date (or such other time specified by the Plan Administrator). Upon a termination, the Participant’s accumulated payroll deductions will be returned to the Participant, without interest, as soon as administratively practicable.

The termination of such Purchase Right is irrevocable, and the Participant may not subsequently rejoin the Offering Period for which the terminated Purchase Right was granted. In order to resume participation in any subsequent Offering Period, such individual must re-enroll in the ESPP (by making a timely filing of the prescribed enrollment forms). A Participant who reduces his or her withholding rate for future payroll periods to zero percent (0%) will be deemed to have terminated his or her participation in future Offering Periods, unless the Participant re-enrolls in the ESPP.

Termination of Eligibility

Upon the termination of the Participant’s employment for any reason (including death) during an Offering Period, or in the event he or she ceases to qualify as an Eligible Employee, the Participant ceases to be a Participant, any Purchase Right will be canceled, the accumulated payroll deductions are returned to the Participant (or to his or her estate or designated beneficiary in the event of death) without interest, as soon as administratively practicable thereafter, and the Participant will have no further rights under the ESPP. Should the Participant cease to remain in active service by reason of an approved leave of absence, the effect of such leave on a Participant will be determined in accordance with applicable regulations under Section 423 of the U.S. Internal Revenue Code.

Duration, Termination and Amendment

The Board of Directors of the Company may, at any time or times, suspend or terminate the ESPP. If the ESPP is suspended or terminated, the Board of Directors may provide that outstanding Purchase Rights will be exercisable either on the Purchase Date of the applicable Offering Period or on such earlier date as the Board of Directors may specify, or that the Participant’s accumulated payroll deductions will be returned to the Participant without interest.

The ESPP will terminate and no Purchase Rights will be granted after the earliest to occur of the ESPP’s termination by the Company, the issuance of all shares of common stock available for issuance under the ESPP or June 9, 2025.

The Board of Directors may at any time amend the ESPP to any extent and in any manner as it may deem advisable. Shareholder approval may be required for certain amendments by the terms of the ESPP, the U.S. Internal Revenue Code, the rules of NASDAQ, or the rules of the SEC.

Transferability of Purchase Rights

Purchase Rights granted under the ESPP are not assignable or transferable by the Participant other than by will or by the laws of descent and distribution following the Participant’s death, and during the Partici- pant’s lifetime the Purchase Right shall be exercisable only by the Participant. Any transfer or attempt to

transfer the rights under the ESPP will result in the termination of the Purchase Rights and, upon the return the accumulated payroll deductions, without interest, all rights under the ESPP will terminate.

Enrollment

The ESPP is a voluntary plan and requires Eligible Employees to enroll in order to participate. Prior to each Offering Period, Eligible Employees are notified of the enrollment deadlines by internal postings on the Company’s intranet. Enrollments completed after the enrollment deadline will take effect in the next following Offering Period.

The plan document for the ESPP is available on the Company’s intranet in the Human Resources business area and in the enrollment area of Fidelity’s website at www.netbenefits.fidelity.com. To enroll in the ESPP, the Eligible Employee is required to access Fidelity’s website at www.netbenefits.fidelity.com.

REASONS FOR THE OFFERING AND USE OF PROCEEDS

Purpose of the ESPP

The ESPP is intended to enable Eligible Employees to use payroll deductions to acquire common stock in the Company at a discount to current market trading prices.

Proceeds and Use of Proceeds

As of the date of this prospectus, the shares under the ESPP are offered to approximately 7,300 Eligible Employees worldwide. The maximum rate at which employees may purchase shares may not exceed USD 25,000 worth of stock per calendar year in which the right is outstanding. The USD 25,000 limit includes Biogen’s company contribution via the discount, so each employee’s maximum annual purchase price is USD 21,250. Assuming that each of the approximately 7,300 Eligible Employees purchased the maximum annual amount of shares offered under the ESPP in the twelve months following the date of the prospectus, that is, shares worth a total of USD 25,000 each upon payment of USD 21,250, and after the deduction of the estimated cost of offering under the ESPP of USD 50,000 then the net proceeds to Biogen in connection with the offer under the ESPP pursuant to this prospectus would be USD 155,075,000. The Company may use the proceeds from the issuance and exercise of Purchase Rights under the ESPP for any corporate purpose.

DILUTION

The book value of the shareholders’ equity of the Company (defined as total assets less total liabilities) as reflected in the audited condensed consolidated financial statements amounted to approximately USD 9,374,900,000 as of December 31, 2015. This is equivalent to approximately USD 42.87 per share (calculated on the basis of 218,667,750 issued and outstanding shares as of December 31, 2015). If the Company had obtained net proceeds in the amount of USD 155,075,000 as of December 31, 2015, the book value of the shareholders’ equity at that time would have been about USD 9,529,975,000 or USD 43.45 per share (based on the increased number of shares after the purchase of 673,680 shares assuming a purchase price of USD 230.27 which takes into account the discount and is 85% of the stock’s closing price as of March 1, 2016). Consequently, under the above-mentioned assumptions, the implementation of the offering would lead to a direct increase in the book value of shareholders’ equity of approximately USD 155,075,000 or USD 0.58 per share corresponding to approximately 1.34% per share for the existing shareholders and an average dilution of approximately USD 186.82 per share for the Eligible Employee who purchased the shares and, thus, investors who acquire shares at the purchase price of USD 230.27 are diluted by about 81.13%.

DIVIDEND POLICY

Biogen has not historically paid cash dividends, and does not currently intend to pay dividends in the fore- seeable future.

CAPITALIZATION

Capitalization and Indebtedness

The following information is based on the Company’s audited consolidated financial statements for the fiscal year ended December 31, 2015 as published in the Company’s Annual Report on Form 10-K for the fiscal year ended December 31, 2015 which can be accessed as described in the section “Documents Available for Inspection” of this prospectus. The Company’s consolidated financial statements were prepared in accordance with accounting principles generally accepted in the United States of America (“U.S. GAAP”).

LIABILITIES AND SHAREHOLDERS’ EQUITY December 31, 2015

(in U.S.$)

(in millions, except per share amounts)

Total current liabilities 2,577.7

Guaranteed: -

Secured: -

Unguaranteed/Unsecured: Accounts payable 267.4 Taxes payable 208.7 Accrued expenses and other 2,096.8 Current portion of notes payable and other financing arrangements 4.8

Total non-current liabilities 7,552.2

Guaranteed: -

Secured: -

Unguaranteed/Unsecured: Notes payable and other financing arrangements 6,521.5 Long-term deferred tax liability 124.9 Other long-term liabilities 905.8

Total liabilities 10,129.9

Shareholders’ equity:

Common stock, par value $0.0005 per share 0.1 Additional paid-in capital - Accumulated other comprehensive loss (224.0) Retained Earnings 12,208.4 Treasury stock, at cost (2,611.7) Total Biogen Inc. shareholders’ equity 9,372.8

Non-controlling interests 2.1

Total shareholders’ equity 9,374.9

Total liabilities and shareholders’ equity 19,504.8

The following table shows the Company’s net financial indebtedness. Consequently, the table does not include non-financial debt from normal operations such as accounts payable, taxes payable, deferred tax liability, accrued expenses and long term liabilities other than bank debt or notes payable.

NET FINANCIAL INDEBTEDNESS December 31, 2015 (in U.S.$ millions) A.+B. Cash and cash equivalents* 1,308.0 C. Trading securities - D. Liquidity (A)+(B)+(C) 1,308.0 E. Current Financial Receivable - F. Current Bank debt - G. Current portion of non-current debt and lines of credit 4.8 H. Other current financial debt - I. Current Financial Debt (F)+(G)+(H) 4.8 J. Net Current Financial Indebtedness (I)-(E)-(D) (1,303.2) K. Non current Bank loans - L. Notes payable and other financing arrangements 6,521.5 M. Other non current loans - N. Non current Financial Indebtedness (K)+(L)+(M) 6,521.5 O. Net Financial Indebtedness (J)+(N) 5,218.3 ______

* In its financial statements, the Company makes no distinctions between cash and cash equivalents. The Company considers those investments which are highly liquid, readily convertible to cash and that mature within three months from date of purchase to be cash equivalents.

Commitments and Contingencies

Leases

The Company rents laboratory and office space and certain equipment under non-cancelable operating leases. These lease agreements contain various clauses for renewal at the Company’s option and, in certain cases, escalation clauses typically linked to rates of inflation. Rental expense under these leases, net of amounts recognized in relation to exiting the Company’s Weston, Massachusetts facility, which terminate at various dates through 2028, amounted to $68.8 million and $62.4 million in 2015 and 2014, respectively. Rent expense was $56.1 million in 2013. In addition to rent, the leases may require the Company to pay additional amounts for taxes, insurance, maintenance and other operating expenses.

As of December 31, 2015, minimum rental commitments under non-cancelable leases, net of income from subleases, for each of the next five years and total thereafter were as follows:

(In millions) 2016 2017 2018 2019 2020 Thereafter Total

Minimum lease payments(1) $ 75.9 $ 75.7 $ 67.9 $ 66.7 $ 63.2 $ 382.7 $ 732.1

Less: income from subleases (6.0 ) (6.0) (6. 3) (6.3 ) (6.3) (28.9 ) (59.8 ) Net minimum lease payments $ 69.9 $ 69.7 $ 61.6 $ 60.4 $ 56.9 $ 353.8 $ 672.3

(1) As a result of the Company’s decision to relocate its corporate headquarters to Cambridge, Massachu- setts, Biogen vacated part of its Weston, Massachusetts facility in the fourth quarter of 2013. The Compa- ny incurred a charge of $27.2 million in connection with this move. This charge represented its remaining lease obligation for the vacated portion of its Weston, Massachusetts facility, net of sublease income expected to be received. The term of its sublease to the vacated portion of its Weston, Massachusetts facility started in January 2014 and will continue through the remaining term of its lease agreement.

Under certain of the Company’s lease agreements, it is contractually obligated to return leased space to its original condition upon termination of the lease agreement. At the inception of a lease with such conditions, the Company records an asset retirement obligation liability and a corresponding capital asset in an amount equal to the estimated fair value of the obligation. In subsequent periods, for each such lease, the Company records interest expense to accrete the asset retirement obligation liability to full value and de- preciate each capitalized asset retirement obligation asset, both over the term of the associated lease agreement. The Company’s asset retirement obligations were not significant as of December 31, 2015.

In March 2015, the Company signed a lease for additional laboratory space in Cambridge, Massachusetts through June 2025. The Company is subject to future minimum rental commitments related to this lease in the amount of approximately $55.5 million over the term of the lease. There have been no other material changes in the Company’s lease obligations since December 31, 2014.

Eisai Financing Arrangement

During 2015 the Company amended its existing lease related to the oral solid dose products manufacturing facility of Eisai Inc. (“Eisai”) in Research Triangle Park, North Carolina where the Company manufactures its and Eisai's oral solid dose products. As of December 31, 2015, the net present value of the future minimum lease payments were as follows:

(In millions) As of December 31, 2015 2016 $ 2.0 2017 2.0 2018 16.7 2019 — 2020 — Thereafter —

Total 20.7

Less: interest (0.9 ) Net present value of the future minimum lease payments $ 19.8

Tax Related Obligations

The Company excludes liabilities pertaining to uncertain tax positions from its summary of contractual obligations as it cannot make a reliable estimate of the period of cash settlement with the respective taxing authorities. As of December 31, 2015, the Company has approximately $45.4 million of net liabilities associated with uncertain tax positions.

Other Funding Commitments

As of December 31, 2015, the Company has several on-going clinical studies in various clinical trial stag- es. The Company’s most significant clinical trial expenditures are to contract research organizations (“CROs”). The contracts with CROs are generally cancellable, with notice, at the Company’s option. The Company has recorded accrued expenses of approximately $25.0 million on its condensed consolidated balance sheet for expenditures incurred by CROs as of December 31, 2015. The Company has approximately $559.0 million in cancellable future commitments based on existing CRO contracts as of Decem- ber 31, 2015.

Contingent Development, Regulatory and Commercial Milestone Payments

Based on the Company’s development plans as of December 31, 2015, the Company could make potential future milestone payments to third parties of up to approximately $2.8 billion as part of its various collaborations, including licensing and development programs. Payments under these agreements generally become due and payable upon achievement of certain development, regulatory or commercial milestones. Because the achievement of these milestones had not occurred as of December 31, 2015, such contingencies have not been recorded in the Company’s financial statements. Amounts related to contingent milestone payments are not considered contractual obligations as they are contingent on the successful achievement of certain development, regulatory approval and commercial milestones.

Manufacturing Commitments

On December 1, 2015, the Company purchased land in Solothurn, Switzerland where it plans to build a biologics manufacturing facility over the next several years. As of December 31, 2015, the Company had contractual commitments of $126.4 million for the construction of this facility.

TYSABRI Contingent Payments

In 2013, the Company acquired from Elan Pharma International, Ltd. (“Elan”) full ownership of all remaining rights to TYSABRI that the Company did not already own or control. Under the terms of the acquisition agreement, the Company is obligated to make contingent payments to Elan of 18% on annual worldwide net sales up to $2.0 billion and 25% on annual worldwide net sales that exceed $2.0 billion. Royalty payments to Elan and other third parties are recognized as cost of sales in the Company’s consolidated statements of income. Elan was acquired by Perrigo in December 2013. Following that acquisition, the Company began making these royalty payments to Perrigo.

Contingent Consideration related to Business Combinations

In connection with the Company’s acquisitions of Convergence Pharmaceuticals Limited (“Conver- gence”), Stromedix, Inc. (“Stromedix”), Biogen International Neuroscience GmbH (formerly Biogen Idec International Neuroscience GmbH) (“BIN”), Biogen Hemophilia Inc. (formerly Biogen Idec Hemophilia Inc.) (“BIH”) and Fumapharm AG, the Company agreed to make additional payments based upon the achievement of certain milestone events.

As the acquisitions of Convergence, Stromedix and BIN, formerly Panima Pharmaceuticals AG, occurred after January 1, 2009, the Company records contingent consideration liabilities at their fair value on the acquisition date and revalue these obligations each reporting period. The Company may pay up to approximately $1.3 billion in remaining milestones related to these acquisitions.

BIH

In connection with the Company’s acquisition of BIH, formerly Syntonix, in 2007, the Company agreed to pay up to an additional $80.0 million if certain milestone events associated with the development of BIH’s lead product, ALPROLIX are achieved. The first $40.0 million contingent payment was achieved in 2010. The Company paid an additional $20.0 million during the second quarter of 2014 as ALPROLIX was approved for the treatment of hemophilia B. A second $20.0 million contingent payment will occur if, prior

to the tenth anniversary of the closing date, a marketing authorization is granted by the EMA for ALPRO- LIX. This payment will be accounted for as an increase to intangible assets if achieved.

Fumapharm AG

In 2006, the Company acquired Fumapharm AG. As part of this acquisition Biogen acquired FUMA- DERM and TECFIDERA (together, “Fumapharm Products”). The Company paid $220.0 million upon closing of the transaction and agreed to pay an additional $15.0 million if a Fumapharm Product was approved for MS in the U.S. or E.U. In the second quarter of 2013, the Company paid this $15.0 million contingent payment as TECFIDERA was approved in the U.S. for MS by the FDA. The Company is also required to make additional contingent payments to former shareholders of Fumapharm AG or holders of their rights based on the attainment of certain cumulative sales levels of Fumapharm Products and the level of total net sales of Fumapharm Products in the prior twelve month period, as defined in the acquisition agreement.

During 2015, the Company paid $850.0 million in contingent payments as it reached the $4.0 billion, $5.0 billion and $6.0 billion cumulative sales levels related to the Fumapharm Products in the fourth quarter of 2014, second quarter of 2015 and third quarter of 2015, respectively, and accrued $300.0 million upon reaching $7.0 billion in total cumulative sales of Fumapharm Products in the fourth quarter of 2015.

The Company will owe an additional $300.0 million contingent payment for every additional $1.0 billion in cumulative sales level of Fumapharm Products reached if the prior 12 months sales of the Fumapharm Products exceed $3.0 billion, until such time as the cumulative sales level reaches $20.0 billion, at which time no further contingent payments shall be due. These payments will be accounted for as an increase to goodwill as incurred, in accordance with the accounting standard applicable to business combinations when the Company acquired Fumapharm. Any portion of the payment which is tax deductible will be recorded as a reduction to goodwill. Payments are due within 60 days following the end of the quarter in which the applicable cumulative sales level has been reached.

Guarantees

As of December 31, 2015 and 2014, the Company did not have significant liabilities recorded for guarantees.

The Company enters into indemnification provisions under its agreements with other companies in the ordinary course of business, typically with business partners, contractors, clinical sites and customers. Un- der these provisions, the Company generally indemnifies and holds harmless the indemnified party for losses suffered or incurred by the indemnified party as a result of its activities. These indemnification provisions generally survive termination of the underlying agreement. The maximum potential amount of future payments the Company could be required to make under these indemnification provisions is unlim- ited. However, to date the Company has not incurred material costs to defend lawsuits or settle claims related to these indemnification provisions. As a result, the estimated fair value of these agreements is mini- mal. Accordingly, the Company has no liabilities recorded for these agreements as of December 31, 2015 and 2014.

Litigation Commitments and Contingencies

Regarding commitments and contingencies in relation to legal and arbitration proceedings please refer to “Legal and Arbitration Proceedings”.

Working Capital Statement

Biogen believes that its working capital (i.e., its ability to access cash and other available liquid resources) is sufficient to meet its present requirements for at least the next 12 months from the date of this prospectus.

SELECTED CONSOLIDATED FINANCIAL DATA

The following selected financial data are derived from the Company’s audited consolidated financial statements for the fiscal years ended December 31, 2015, December 31, 2014 and December 31, 2013, as published in the Company’s Annual Report on Form 10-K for the fiscal year ended December 31, 2015 which can be accessed as described in the section “Documents Available for Inspection” of this prospectus. The Company’s audited consolidated financial statements were prepared in accordance with U.S. GAAP.

SELECTED THREE-YEAR FINANCIAL DATA (In millions, except per share amounts)

For the Years Ended December 31,

2015(3) (4) 2014 2013(1) (2) Results of Operations Product revenues, net $ 9,188.5 $ 8,203.4 $ 5,542.3 Revenues from unconsolidated joint business 1,339.2 1,195.4 1,126.0

Other revenues 236.1 304.5 263.9 Total revenues 10,763.8 9,703.3 6,932.2 Total cost and expenses 5,872.8 5,747.7 4,441.6 Gain on sale of rights — 16.8 24.9 Income from operations 4,891.0 3,972.4 2,515.5 Other income (expense), net (123.7 ) (25.8 ) (34.9 ) Income before income tax expense and equity in 4,767.3 3,946.6 2,480.6 loss of investee, net of tax Income tax expense 1,161.6 989.9 601.0 Equity in loss of investee, net of tax 12.5 15.1 17.2

Net income 3,593.2 2,941.6 1,862.3 Net income (loss) attributable to non-controlling 46.2 6.8 — interests, net of tax Net income attributable to Biogen Inc. $ 3,547.0 $ 2,934.8 $ 1,862.3

Diluted Earnings Per Share

Diluted earnings per share attributable to Biogen Inc. $15.34 $12.37 $7.81

Weighted-average shares used in calculating diluted earnings per share attributable to Biogen Inc. 231.2 237.2 238.3

As of December 31,

2015(5) (6) 2014 2013 Financial Condition Cash, cash equivalents and marketable securities $ 6,188.9 $ 3,316.0 $ 1,848.5

Total assets $ 19,504.8 $ 14,314.7 $ 11,863.3

Notes payable, line of credit and other financing arrangements, less current portion $ 6,521.5 580.3 592.4

Total Biogen Inc. shareholders’ equity $ 9,372.8 10,809.0 8,620.2

(2) Commencing in the second quarter of 2013, product and total revenues include 100% of net revenues related to sales of TYSABRI as a result of the Company’s acquisition of all remaining rights to TYSABRI from Elan Phar- ma International, Ltd (“Elan”), an affiliate of Elan Corporation, plc. Upon the closing, the Company’s collaboration agreement was terminated, and the Company no longer records collaboration profit sharing expense. The Company recognized collaboration profit sharing expense of $85.4 million during the year ended December 31, 2013. In addition, product and total revenues includes net revenues related to sales of TECFIDERA. (3) Other revenues reflects a decrease in royalty revenues due to the December 2014 expiration of U.S. patent rights that gave rise to royalty payments related to ANGIOMAX.

(4) Included in total cost and expenses is a restructuring charge of $93.4 million incurred in connection with the Com- pany’s corporate restructuring announced on October 21, 2015, which included the termination of certain pipeline programs and an 11% reduction in workforce.

(6) Biogen Inc.'s shareholders' equity reflects a reduction in additional paid in capital and retained earnings totaling $5.0 billion resulting from the repurchase and retirement of the Company’s common stock under the Company’s 2015 Share Repurchase Program.

There has been no significant change in the Company’s financial or trading position since December 31, 2015.

LEGAL AND ARBITRATION PROCEEDINGS

The Company is currently involved in various claims and legal proceedings, including the matters described below.

Patent Matters

Forward Pharma German Patent Litigation

On November 18, 2014 Forward Pharma A/S (“Forward Pharma”) filed suit against Biogen in the Region- al Court of Dusseldorf, Germany alleging that TECFIDERA infringes German Utility Model DE 20 2005 022 112 U1, which was issued in April 2014 and expired in October 2015. Forward Pharma subsequently extended its allegations to assert that TECFIDERA infringes Forward Pharma's European Patent No. 2,801,355, which was issued in May 2015 and expires in October 2025. Forward Pharma seeks declara- tions of infringement and damages for the Company’s sales of TECFIDERA in Germany. Under German law, disgorgement of profits on infringing sales is a measure of damages. A hearing has been scheduled for early 2016. Interference Proceeding with Forward Pharma

In April 2015, the U.S. Patent and Trademark Office (“USPTO”) declared an interference between For- ward Pharma’s pending U.S. Patent Application No. 11/576,871 and the Company’s U.S. Patent No. 8,399,514 (the “'514 patent”). The '514 patent includes claims covering the treatment of multiple sclerosis with 480 mg of dimethyl fumarate as provided for in the Company’s TECFIDERA label. A hearing has been scheduled for early 2017. Inter Partes Review Proceeding

On September 28, 2015, the Coalition for Affordable Drugs V LLC, an entity associated with a hedge fund, filed a petition with the USPTO for inter partes review of the '514 patent, which the Company op- posed. The USPTO has not yet decided whether to institute review. European Patent Office Oppositions

Several parties have filed oppositions in the European Patent Office requesting revocation of the Compa- ny’s European patent number 2 137 537 (the “'537 patent”), which includes claims covering the treatment of multiple sclerosis with 480 mg of dimethyl fumarate as provided for in the Company’s TECFIDERA label. The '537 patent expires in 2028. A hearing has been scheduled for early 2016. Patent Licensing Matter

The Company is in discussions with Pfizer regarding its proposal that the Company takes a license to its U.S. Patent No. 8,603,777 (Expression of Factor VII and IX Activities in Mammalian Cells) and pay royalties on sales of ALPROLIX. An estimate of the possible loss or range of loss cannot be made at this time.

Patent Revocation Matter

In December 2015, Swiss Pharma International AG brought an action in the Patents Court of the United Kingdom to revoke the UK counterpart of the Company’s European Patent Number 1 485 127 (“Administration of agents to treat inflammation”) (the “'127 patent”), which was issued in June 2011 and concerns administration of natalizumab (“TYSABRI”) to treat multiple sclerosis. The patent expires in February 2023. On January 11, 2016 the same entity brought an action in the District Court of The Hague seeking to revoke the Dutch counterpart of the '127 patent. A hearing has been scheduled in the Dutch action for early 2017. No hearing has yet been scheduled in the UK action.

'755 Patent Litigation

On May 28, 2010, Biogen MA Inc. (formerly Biogen Idec MA Inc.) filed a complaint in the U.S. District Court for the District of New Jersey alleging infringement by Bayer Healthcare Pharmaceuticals Inc. (“Bayer”) (manufacturer, marketer and seller of BETASERON and manufacturer of EXTAVIA), EMD Serono, Inc. (manufacturer, marketer and seller of REBIF), Pfizer Inc. (co-marketer of REBIF), and No- vartis Pharmaceuticals Corp. (marketer and seller of EXTAVIA) of the Company’s U.S. Patent No. 7,588,755 (“'755 Patent”), which claims the use of interferon beta for immunomodulation or treating a viral condition, viral disease, cancers or tumors. The complaint seeks monetary damages, including lost profits and royalties. Bayer had previously filed a complaint against the Company in the same court, on May 27, 2010, seeking a declaratory judgment that it does not infringe the '755 Patent and that the patent is invalid, and seeking monetary relief in the form of attorneys' fees, costs and expenses. The court has consolidated the two lawsuits, and the Company refers to the two actions as the “Consolidated '755 Patent Actions.” Bayer, Pfizer, Novartis and EMD Serono have all filed counterclaims in the Consolidated '755 Patent Ac- tions seeking declaratory judgments of patent invalidity and non-infringement, and seeking monetary relief in the form of costs and attorneys' fees, and EMD Serono and Bayer have each filed a counterclaim seeking a declaratory judgment that the '755 Patent is unenforceable based on alleged inequitable conduct. Bayer has also amended its complaint to seek such a declaration. No trial date has been set.

Italian National Medicines Agency

In the fourth quarter of 2011, Biogen Italia SRL received notice from the Italian National Medicines Agen- cy (Agenzia Italiana del Farmaco or “AIFA”) that sales of TYSABRI after mid-February 2009 exceeded a reimbursement limit established pursuant to a Price Determination Resolution (“Price Resolution”) granted by AIFA in December 2006. On December 23, 2011, the Company filed an appeal in the Regional Admin- istrative Tribunal of Lazio (Il Tribunale Amministrativo Regionale per il Lazio) in Rome, Italy seeking a ruling that the reimbursement limit in the Price Resolution should apply as written to only “the first 24 months” of TYSABRI sales, which ended in mid-February 2009. The appeal is still pending. In June 2014, AIFA approved a resolution affirming that there is no reimbursement limit from and after February 2013. AIFA and Biogen Italia SRL are discussing a possible resolution for the period from February 2009 through January 2013.

Government Matters

The Company has learned that U.S. state and federal governmental authorities are investigating its sales and promotional practices and have received related subpoenas. The Company is cooperating with the government in this matter. The Company also received a subpoena from the federal government for documents relating to its relation- ship with certain pharmacy benefit managers, with which the Company cooperated. The Company does not anticipate any further involvement.

Qui Tam Litigation

On July 6, 2015, four qui tam actions filed against the Company by relators suing on behalf of the United States and certain states were unsealed by the U.S. District Court for the District of Massachusetts. The actions, which have been administratively consolidated, allege sales and promotional activities in violation of the federal False Claims Act and state law counterparts, and seek single and treble damages, civil penalties, interest, attorneys’ fees and costs. The United States declined to intervene in two of the actions, both of which have since been voluntarily dismissed, and has not made an intervention decision in the other two actions, which the Company has moved to dismiss. An estimate of the possible loss or range of loss cannot be made at this time.

Securities Litigation

Biogen and certain current and former officers are defendants in In re Biogen Inc. Securities Litigation, filed by a shareholder on August 18, 2015 in the U.S. District Court for the District of Massachusetts. The amended complaint alleges violations of federal securities laws under 15 U.S.C. §78j(b) and §78t(a) and 17 C.F.R. §240.10b-5. The lead plaintiff seeks a declaration of the action as a class action, certification as a representative of the class and its counsel as class counsel, and an award of damages, interest, and attorneys' fees. An estimate of the possible loss or range of loss cannot be made at this time.

Product Liability and Other Legal Proceedings

The Company is also involved in product liability claims and other legal proceedings generally incidental to its normal business activities. While the outcome of any of these proceedings cannot be accurately pre- dicted, the Company does not believe the ultimate resolution of any of these existing matters would have a material adverse effect on the Company’s business or financial condition.

SHAREHOLDINGS AND STOCK OPTIONS OF MEMBERS OF THE ADMINISTRATIVE, MANAGEMENT AND SUPERVISORY BODIES

The following table and notes provide information about the beneficial ownership of the Company’s issued and outstanding, common stock as of March 7, 2016 (“Ownership Date”), by (i) each of the Company’s current executive officers; (ii) each of the Company’s current directors; (iii) all of the Company’s current directors and executive officers as a group.

Except as otherwise noted, the persons identified have sole voting and investment power with respect to the shares of the Company’s common stock beneficially owned. Beneficial ownership is determined in accordance with the rules of the SEC and includes voting and investment power with respect to the shares.

Common Stock Beneficially Owned(1) Shares Subject Percentage to of Exercisable Issued and Name of Beneficial Owner Shares Options and Outstanding Owned RSUs (1) Shares (2)

Susan H. Alexander 31,840 6,250 * Spyros Artavanis-Tsakonas (3) 2,549 650 * Paul J. Clancy 26,870 0 * Gregory F. Covino (3) 2,204 348 * John G. Cox 30,516 10,480 * Alexander J. Denner (4) 317,195 0 * Kenneth DiPietro 3,937 0 * Caroline D. Dorsa 15,338 27,570 * Adriana (Andi) Karaboutis 2,455 0 * Adam Koppel, M.D., Ph.D. 1,865 0 * Nancy L. Leaming 7,229 0 * Richard C. Mulligan 7,195 0 * Robert W. Pangia 14,873 17,125 * Stelios Papadopoulos (5) 25,540 0 * Brian S. Posner 4,580 0 * Eric K. Rowinsky 11,310 0 * Alfred Sandrock 2,185 0 * George A. Scangos (6) 71,677 0 * Lynn Schenk (7) 7,295 0 * Stephen A. Sherwin 4,150 12,000 * Executive officers and directors as a group (20 persons) (8) 590,804 74,423 * ______* Represents beneficial ownership of less than 1% of the Company’s issued and outstanding shares of common stock. (1) Includes options that will become exercisable and restricted stock units (“RSUs”) that will vest within 60 days of the Ownership Date. (2) The calculation of percentages is based upon 218,982,181 shares issued and outstanding on the Ownership Date, plus shares subject to options and RSUs held by the respective person that are currently exercisable or become exercisable within 60 days of the Ownership Date.

(3) Includes shares underlying RSUs that vest within 60 days of the Ownership Date, assuming the maximum possible number of shares that are eligible for vesting on that date. The actual number of shares that will vest will be determined by comparing (x) the average market price of Biogen’s common stock during the sixty days prior to the vesting date with (y) the average market price of Biogen’s common stock during the sixty days prior to the grant date.

(4) Includes (i) 190,142 shares of common stock directly beneficially owned by Sarissa Capital Do- mestic Fund LP, a Delaware limited partnership ("Sarissa Domestic”); and (ii) 119,858 shares of common stock directly beneficially owned by Sarissa Capital Offshore Master Fund LP, a Cay- man Islands limited partnership ("Sarissa Offshore" and, together with Sarissa Domestic, the “Sarissa Funds”). Sarissa Capital Management GP LLC, a Delaware limited liability company ("Sarissa Capital GP"), is the general partner of Sarissa Capital Management LP, a Delaware limited partnership ("Sarissa Capital"), the investment advisor to the Sarissa Funds. Alexander Den- ner is the Chief Investment Officer of Sarissa Capital and the managing member of Sarissa Capital GP. By virtue of the foregoing, Dr. Denner may be deemed to indirectly beneficially own (as that term is defined in Rule 13d-3 of the Securities Exchange Act of 1934, as amended) the shares that the Sarissa Funds directly beneficially own. Dr. Denner disclaims beneficial ownership of such shares of Common Stock owned by the Sarissa Funds. (5) Includes 10,000 shares held in limited liability companies of which Dr. Papadopoulos is the sole manager. (6) Includes 10,756 shares held in trusts of which Dr. Scangos is the trustee. (7) Includes 3,100 shares held in a trust of which Ms. Schenk is the trustee. (8) Includes 23,856 shares held indirectly (by spouse or through trust, partnership or otherwise).

GENERAL INFORMATION ON BIOGEN

Company Name

The Company’s legal and commercial name is Biogen Inc.

General Information on Biogen - and its Business

The Company was formed as a corporation in the State of California in 1985 under the name IDEC Phar- maceuticals Corporation and reincorporated as a Delaware corporation in 1997. In 2003, the Company acquired Biogen, Inc. and changed its corporate name to Biogen Idec Inc. Effective March 23, 2015, the Company changed its name from Biogen Idec Inc. to Biogen Inc.

Biogen is a global biopharmaceutical company focused on discovering, developing, manufacturing and delivering therapies to patients for the treatment of neurodegenerative diseases, hematologic conditions and autoimmune disorders. Its marketed products include TECFIDERA, AVONEX, PLEGRIDY, TYSA- BRI and FAMPYRA for MS, ELOCTATE for hemophilia A and ALPROLIX for hemophilia B, and FUMADERM for the treatment of severe plaque psoriasis. Biogen also has a collaboration agreement with Genentech, Inc. (“Genentech”), a wholly-owned member of the Roche Group (the “Roche Group”), which entitles Biogen to certain business and financial rights with respect to RITUXAN for the treatment of non- Hodgkin's lymphoma, chronic lymphocytic leukemia (“CLL”) and other conditions, GAZYVA indicated for the treatment of CLL, and other potential anti-CD20 therapies (therapies against the protein CD20 which is found on the surface of immune cells). Summary information about the Company’s marketed products is as follows:

• TECFIDERA (dimethyl fumarate), an oral therapy indicated in the U.S. for the treatment of patients with relapsing forms of MS and in the E.U. for people with relapsing-remitting MS (“RRMS”).

• AVONEX (interferon beta-1a), an intramuscular injectable therapy, indicated for the treatment of patients with relapsing forms of MS.

• PLEGRIDY (peginterferon beta-1a), a subcutaneous injectable therapy, indicated in the U.S for the treatment of patients with relapsing forms of MS and in the E.U. for RRMS.

 FAMPYRA (prolonged-release fampridine tablets), is indicated for the improvement of walking ability in adult patients with MS. The Company has a license from Acorda Therapeutics, Inc. to develop and commercialize FAMPYRA in all markets outside the U.S.

• ELOCTATE (Antihemophilic Factor (Recombinant), Fc Fusion Protein), a recombinant DNA-derived, antihemophilic factor indicated in the U.S. for treatment in adults and children with hemophilia A for control and prevention of bleeding episodes, perioperative management and routine prophylaxis to prevent or reduce the frequency of bleeding episodes. ELOCTATE was approved by the FDA in June 2014 and in Japan in December 2014. In November 2015, the European Commission (“EC”) approved ELOCTA, the approved trade name for ELOCTATE in the E.U., for the treatment of hemophilia A. The Company’s collaborator, Swedish Orphan Biovitrum AB has assumed final development and commercialization of ELOCTA in their territory, which essentially includes Europe, North Africa, Rus- sia, and certain markets in the Middle East. • ALPROLIX (Coagulation Factor IX (Recombinant), Fc Fusion Protein), a recombinant DNA-derived, coagulation Factor IX concentrate indicated in the U.S. for treatment in adults and children with hemophilia B for control and prevention of bleeding episodes, perioperative management and routine prophylaxis to prevent or reduce the frequency of bleeding episodes. In June 2015, the EMA validated the Company’s marketing authorization application for ALPROLIX for the treatment of hemophilia B.In July 2015, Swedish Orphan Biovitrum AB exercised its option to assume final development and

commercialization of ALPROLIX in t in their territory, which essentially includes Europe, North Afri- ca, Russia, and certain markets in the Middle East. • RITUXAN (rituximab), a widely prescribed monoclonal antibody used to treat non-Hodgkin’s lymphoma, rheumatoid arthritis, CLL and two forms of antineutrophil cytoplasmic antibodies (ANCA)- associated vasculitis. • GAZYVA (obinutuzumab), in combination with chlorambucil, is indicated for the treatment of patients with previously untreated CLL.

Product revenues for the years ended December 31, 2015, 2014 and 2013 are summarized as follows1:

For the Years Ended % Change December 31, 2015 com- 2014 com- (In millions, except percent- 2015 2014 2013 pared to pared to Multipleages) Sclerosis (MS): 2014 2013 TECFIDERA $ 3,638.4 $ 2,909.2 $ 876.1 25.1 % 232.1 %

Interferon* 2,968.7 3,057.6 3,005.5 (2.9)% 1.7%

TYSABRI 1,886.1 1,959.5 1,526.5 (3.7) % 28.4 %

FAMPYRA 89.7 80.2 74.0 11.8 % 8.4 % Hemophilia: ELOCTATE 319.7 58.4 — 447.4 ** ALPROLIX 234.5 76.0 — 208.6 ** Other product revenues: FUMADERM 51.4 62.5 60.2 (17.8) % 3.8 % Total product revenues $ 9,188.5 8,203.4 5,542.3 12.0 % 48.0 % * Interferon includes AVONEX and PLEGRIDY ** Percentage not meaningful The major markets for Biogen’s business are the U.S., Europe (excluding Germany), Germany, Asia and other which represented approximately 71%, 16%, 7%, 2% and 4% of its 2015 product revenues, respectively, as of December 31, 2015.

The Company supports its drug discovery and development efforts through the commitment of significant resources to discovery, research and development programs and business development opportunities, particularly within areas of the Company’s scientific, manufacturing and technical expertise and scientific adjacencies. In addition to its innovative drug development efforts, the Company aims to leverage Bio- gen’s manufacturing capabilities and scientific expertise to extend its mission to improve the lives of patients living with serious diseases through the development, manufacture and marketing of biosimilars through Samsung Bioepis, its joint venture with Samsung BioLogics Co. Ltd. (“Samsung Biologics”). In January 2016, the EC approved the marketing authorization application (“MAA”) for BENEPALI, an etanercept biosimilar referencing ENBREL, for marketing in the E.U. Under the Company’s agreement with Samsung Bioepis, Biogen will manufacture and commercialize BENEPALI in specified E.U. countries.

1 Source: Notes to the audited consolidated financial statements of the Company’s Form 10-K filed with the SEC on February 3rd 2016.

Patents are important to obtaining and protecting exclusive rights in the Company’s products and product candidates. Regulatory exclusivity, which may consist of regulatory data protection and market protection, also can provide meaningful protection for the Company’s products. The Company regularly seeks patent and regulatory protection in the U.S. and in selected countries outside the U.S.

The Company’s trademarks are important to it and are generally covered by trademark applications or registrations in the U.S. Patent and Trademark Office (“USPTO”) and the patent or trademark offices of other countries.

The Company’s current and contemplated activities and the products, technologies and processes that will result from such activities as well as sales, marketing, product pricing and reimbursement are subject to substantial government regulation.

Biogen’s principal executive offices are located at 225 Binney Street, Cambridge, Massachusetts 02142, U.S.A. and its telephone number is (+1) (617) 679-2000.

Auditors

The Company’s independent registered public accounting firm is PricewaterhouseCoopers LLP (“PwC”), 101 Seaport Boulevard, Boston, MA 02210, U.S.A.

PwC is an independent registered public accounting firm with the U.S. Public Company Accounting Over- sight Board. PwC has been the Company’s independent auditor since 2003. PwC audited the Company’s consolidated financial statements for the fiscal years ended December 31, 2015, December 31, 2014 and December 31, 2013.

DESCRIPTION OF THE SECURITIES

Type and the Class of the Securities being offered, including the Security Identification Code

The securities offered under the ESPP are Biogen’s common stock with a par value of USD 0.0005 per share.

As of December 31, 2015 the Company’s authorized common stock consisted of 1,000,000,000 shares of common stock with a par value of USD 0.0005 per share.

The Company’s common stock is listed on the NASDAQ under the symbol “BIIB”. The U.S. security identification (“CUSIP”) number of the shares is 09062X103. The CUSIP number is the U.S. equivalent of the international security identification number (“ISIN”).

Stock Repurchase Programs

In May 2015, the Company’s Board of Directors authorized a program to repurchase up to $5.0 billion of the Company’s common stock (“2015 Share Repurchase Program”).

The following table summarizes the Company’s common stock repurchase activity under its 2015 Share Repurchase Program during the fourth quarter of 2015:

Maximum Total Number of Approximate Dollar Value Shares Purchased of Shares That May Yet as Part of Publicly Be Total Number of Average Price Announced Pro- Purchased Under Shares Purchased Paid per Share grams The Company’s Programs Period (#) ($) (#) ($ in millions) October 2015 4,976,270 275.87 4,976,270 $ 629.0

November 2015 2,131,417 295.12 2,131,417 $ —

December 2015 — — — $ —

Total 7,107,687 281.64

As of December 31, 2015, the 2015 Share Repurchase Program was completed and the Company repur- chased and retired approximately 16.8 million shares of common stock at a cost of $5.0 billion during the year ended December 31, 2015.

In February 2011, the Company’s Board of Directors authorized a program to repurchase up to 20.0 million shares of the Company’s common stock (“2011 Share Repurchase Program”), which has been used princi- pally to offset common stock issuances under the Company’s share-based compensation plans. The 2011 Share Repurchase Program does not have an expiration date. The Company did not repurchase any shares of common stock under the 2011 Share Repurchase Program during the year ended December 31, 2015 and has approximately 1.3 million shares remaining available for repurchase under this authorization.

Legislation under which the Securities have been Created / Regulation of the Shares

The Shares were created under the General Corporation Law of the State of Delaware (U.S.). Except as otherwise expressly required under the laws of a country, the ESPP and all rights thereunder shall be gov- erned by and construed in accordance with the laws of the State of Delaware, U.S.

Biogen’s common stock is regulated by the U.S. Securities Exchange Act of 1934, as amended.

Form of Securities, Name and Address of the Entity in Charge of Keeping the Records

The Company’s common stock is in registered form. In general, shareholders may hold shares of the Com- pany’s common stock, at their choosing, either in certificated form or in book-entry form. The records are kept by the Company’s transfer agent, Computershare, Inc., who serves as the depository agent for the purpose of this offer if the shareholders decide to register as record holder and hold physical certificates. The address and telephone number of the depository agent is Computershare Trust Company NA, 250 Royall Street, Canton, Massachusetts 02021-1011, U.S.A., phone no: (+1) 781 575-2879.

The Company’s designated ESPP service provider is Fidelity. The shares issuable under the ESPP to Eligi- ble Employees participating in the ESPP are deposited into a designated brokerage account at Fidelity. Par- ticipants may obtain information about their accounts online at www.netbenefits.fidelity.com or by calling a Fidelity representative at (+1) 800-544-0275.

Biogen serves as the paying agent for the purpose of this offer.

Commission

On sales of shares obtained upon exercise of the Purchase Rights a commission is charged by Fidelity and the SEC. Upon selling any shares, Fidelity charges Participants a fee equal to USD 15 for the sale of up to 250 shares and USD 0.06 for each additional share sold. In addition, the SEC currently charges $18.40 per $1,000,000 of aggregate sale proceeds (e.g., sale proceeds x $0.00001840 = SEC regulatory fee).

Currency of the Securities Issue

The U.S. Dollar is the currency of the security issue.

Rights attached to the Securities

No Eligible Employee participating in the ESPP shall have any voting, dividend or other shareholder rights with respect to any offering under the ESPP until the shares are purchased pursuant to the ESPP on behalf of the Participant and the Participant has become a holder of the purchased shares. Following the purchase, the Eligible Employee participating in the ESPP shall be entitled to the rights attached to the shares, as further described below:

Dividend Rights. The Board of Directors may declare a dividend at any regular or special meeting out of funds legally available for dividends. The Board of Directors sets the record date and the payment date for dividend payments. Such dividends may be paid in cash, property or shares of stock. A holder of shares as of the record date for a dividend declaration has an inchoate property right to the dividend as of that record date, but may not actually attempt to enforce that right until the payment date. In general, dividends that are unclaimed for three years escheat to the State of Delaware.

However, Biogen has never paid any cash dividends and has no current intention to do so. There are no dividend restrictions and no special dividend procedures for shareholders resident in the E.U. and the Euro- pean Economic Area.

Voting Rights. The holders of common stock are entitled to one vote for each share held on all matters as to which shareholders are entitled to vote. Any action required or permitted to be taken by the shareholders for the Company may be effected by a duly called annual or special meeting of such holders or may be effected by consent in writing by such shareholders. Special meetings of the shareholders of the Company may be held upon call of the Chairman of the Board of Directors, the Chief Executive Officer, by the Board of Di- rectors of the Company or, in accordance with the Company’s Bylaws, holders of at least 25% of the Com- pany’s common stock.

Rights to Receive Liquidation Distributions. In the event of liquidation, dissolution or winding up of the Company, the holders of common stock are entitled to share ratably in all assets remaining after payment of or provisions for the Company’s liabilities, subject to prior rights or preferred stock, if any, then outstanding.

No Preemptive, Redemptive, Profit or Conversions Provisions. The holders of the Company’s common stock do not have preemptive rights to acquire shares of the Company’s stock or securities convertible into the Company’s stock. The Company’s common stock is not subject to redemption and does not have any right to share in the Company’s profits or any conversion rights.

Change of Shareholders’ Rights

The rights of holders of the Company’s common stock may be changed only by a formal amendment of the Company’s certificate of incorporation or bylaws, except that the Company’s Board of Directors may issue preferred stock from time to time in one or more series and may fix the rights, preferences, privileges and restrictions of each series of preferred stock. Any or all of the rights and preferences selected by the Com- pany’s Board of Directors for any series of preferred stock may be greater than the rights of the common stock. Some of the rights and preferences that the Board of Directors may designate include dividend rights, conversion rights, voting rights, terms of redemption, liquidation preferences and sinking fund terms.

Transferability

The offering of shares under the ESPP has been registered in the U.S. with the SEC on a registration statement on Form S-8 and the issued and outstanding shares of common stock are generally freely transferable.

The ESPP is intended to provide shares for investment. The Company does not, however, intend to restrict or influence any employee in the conduct of his or her own affairs. A Participant, therefore, may sell shares purchased under the ESPP at any time he or she chooses, subject to compliance with any applicable securities laws, insider trading policies and applicable blackout periods, and the terms of the ESPP. The Partici- pant assumes the risk of any market fluctuations in the price of the shares.

Applicable Squeeze-out and Sell-out Rules

Under Section 253 of the General Corporation Law of the State of Delaware (US) (the “DGCL”), a corporation owning at least 90% of the outstanding shares of each class of the stock of a subsidiary corporation may effect a “short form” merger in which the shares of the subsidiary held by minority stockholders are converted into cash, stock or other property and the subsidiary is merged with the parent corporation. A short form merger pursuant to Section 253 may be authorized by the board of directors of the parent corporation without a vote of the stockholders of the subsidiary corporation. The minority stockholders of the subsidiary corporation are, however, entitled to seek judicial appraisal of their shares in connection with short form merger transactions in accordance with Section 262 of the DGCL.

Share Based Compensation Plans

Biogen has three share-based compensation plans pursuant to which awards are currently being made: (i) the Biogen Inc. 2006 Non-Employee Directors Equity Plan (“2006 Directors Plan”); (ii) the Biogen Inc. 2008 Amended and Restated Omnibus Equity Plan (“2008 Omnibus Plan”); and (iii) the Biogen Inc. 2015 Employee Stock Purchase Plan (“ESPP”).

Directors Plan

In May 2006, the Company’s stockholders approved the 2006 Directors Plan for share-based awards to the Company’s directors. Awards granted from the 2006 Directors Plan may include stock options, shares of restricted stock, restricted stock units, stock appreciation rights and other awards in such amounts and with such terms and conditions as may be determined by a committee of the Company’s Board of Directors, subject to the provisions of the plan. Biogen has reserved a total of 1.6 million shares of common stock for issuance under the 2006 Directors Plan. The 2006 Directors Plan provides that awards other than stock op-

tions and stock appreciation rights will be counted against the total number of shares reserved under the plan in a 1.5-to-1 ratio. In June 2015, the Company’s stockholders approved an amendment to extend the term of the 2006 Directors Plan until June 10, 2025.

Omnibus Plans

In June 2008, the Company’s stockholders approved the 2008 Omnibus Plan for share-based awards to the Company’s employees. Awards granted from the 2008 Omnibus Plan may include stock options, shares of restricted stock, restricted stock units, performance shares, shares of phantom stock, stock appreciation rights and other awards in such amounts and with such terms and conditions as may be determined by a committee of the Company’s Board of Directors, subject to the provisions of the plan. Shares of common stock available for issuance under the 2008 Omnibus Plan consist of 15.0 million shares reserved for this purpose, plus shares of common stock that remained available for issuance under the Company’s 2005 Omnibus Equity Plan on the date that the Company’s stockholders approved the 2008 Omnibus Plan, plus shares that were subject to awards under the 2005 Omnibus Equity Plan which remain unissued upon the cancellation, surrender, exchange or termination of such awards. The 2008 Omnibus Equity Plan provides that awards other than stock options and stock appreciation rights will be counted against the total number of shares available under the plan in a 1.5-to-1 ratio.

INFORMATION ON THE GOVERNING BODIES OF BIOGEN

The Company’s Directors as of the date of this prospectus

The Company’s Board of Directors currently consists of the following directors, each serving a one-year term:

Alexander J. Denner Caroline D. Dorsa Nancy L. Leaming Richard C. Mulligan Robert W. Pangia Stelios Papadopoulos Brian S. Posner Eric K. Rowinsky George A. Scangos Lynn Schenk Stephen A. Sherwin

As described in detail below, the Company’s directors have considerable professional and business expertise.

Alexander J. Denner, 46, has served as one of the Company’s directors since 2009. Dr. Denner is a founding partner and Chief Investment Officer of Sarissa Capital Management LP. Sarissa Capital focuses on improving the strategies of companies to better provide shareholder value. From 2006 to 2011, Dr. Denner served as a Senior Managing Director at Icahn Capital. Prior to that, he served as a portfolio manager at Viking Global Investors and Morgan Stanley Investment Management. Dr. Denner is also a director of AR- IAD Pharmaceuticals, Inc. and The Medicines Company. During the past five years, Dr. Denner has also served as a director of the following companies: Amylin Pharmaceuticals, Inc., Enzon Pharmaceuticals, Inc. and Vivus, Inc.

Caroline D. Dorsa, 56, has served as one of the Company’s directors since 2010. Ms. Dorsa served as the Executive Vice President and Chief Financial Officer of Public Service Enterprise Group Incorporated, a diversified energy company, from April 2009 until her retirement in October, 2015, and served on its board of directors from 2003 to April 2009. From February 2008 to April 2009, she served as Senior Vice Presi- dent, Global Human Health, Strategy and Integration at Merck & Co., Inc., a pharmaceutical company. From November 2007 to January 2008, Ms. Dorsa served as Senior Vice President and Chief Financial Officer of Gilead Sciences, Inc., a life sciences company. From February 2007 to November 2007, she served as Senior Vice President and Chief Financial Officer of Avaya, Inc., a telecommunications company. From 1987 to January 2007, Ms. Dorsa held various financial and operational positions at Merck & Co., Inc., including Vice President and Treasurer, Executive Director of U.S. Customer Marketing and Execu- tive Director of U.S. Pricing and Strategic Planning.

Nancy L. Leaming, 68, has served as one of the Company’s directors since 2008. Ms. Leaming has been an independent consultant since 2005. From 2003 to 2005, she served as the Chief Executive Officer and Pres- ident of Tufts Health Plan, a provider of healthcare insurance. From 1986 to 2003, Ms. Leaming served in several executive positions at Tufts Health Plan, including President, Chief Operating Officer and Chief Financial Officer. Ms. Leaming is also a director of Hologic, Inc. and Edgewater Technology, Inc.

Richard C. Mulligan, 61, Dr. Mulligan has served as one of the Company’s directors since 2009. Dr. Mul- ligan is a founding partner of Sarissa Capital Management LP. Sarissa Capital focuses on improving the strategies of companies to better provide shareholder value. In 2013, Dr. Mulligan became the Mallinckrodt Professor of Genetics, Emeritus, at Harvard Medical School, after serving as the Mallinckrodt Professor of Genetics and Director of the Harvard Gene Therapy Initiative since 1996. Prior to that, he was Professor of Molecular Biology at the Massachusetts Institute of Technology, a member of the Whitehead Institute for Biomedical Research, and the Chief Scientific Officer of Somatix Therapy Corporation, a drug discovery and development company that he founded. Dr. Mulligan was named a MacArthur Foundation Fellow in 1981. During the past five years, Dr. Mulligan has also served as a director of the following companies: Cellectis SA and Enzon Pharmaceuticals, Inc.

Robert W. Pangia, 64, Mr. Pangia served as a director of the Company from 1997 to 2003 during the period the Company was operated as IDEC Pharmaceuticals, and has served as a director since 2003 following IDEC’s merger with Biogen Inc. Mr. Pangia has been the Chief Executive Officer of Ivy Sports Medicine, LLC, a medical device company, since 2011. He has also been a partner in Ivy Capital Partners, LLC, the

general partner of Ivy Healthcare Capital, L.P., a private equity fund specializing in healthcare investments, since 2003. From October 2007 to October 2009, he served as the Chief Executive Officer of Highlands Acquisition Corp., a special purpose acquisition company. From 1996 to 2003, Mr. Pangia was self- employed as an investment banker. From 1987 to 1996, he held various senior management positions at PaineWebber, a financial services company, including Executive Vice President and Director of Investment Banking for PaineWebber Incorporated of New York, member of the board of directors of PaineWebber, Inc., Chairman of PaineWebber Properties, Inc., and member of several of PaineWebber’s executive and operating committees.

Stelios Papadopoulos, 67, has served as one of the Company’s directors since 2008 and as its independent Chairman since June 2014. Dr. Papadopoulos also serves as the Chairman of Exelixis, Inc., a drug discovery and development company that he co-founded in 1994. Previously, he was an investment banker with Cowen & Co., LLC, a financial services company, focusing on the biotechnology and pharmaceutical sec- tors, from 2000 until his retirement as Vice Chairman in August 2006. Prior to joining Cowen & Co., Dr. Papadopoulos served for 13 years as an investment banker at PaineWebber, Inc., a financial services company, where he was most recently Chairman of PaineWebber Development Corp., a PaineWebber subsidiary focusing on biotechnology. Dr. Papadopoulos is also a director of BG Medicine, Inc: Exelixis, Inc. and Regulus Therapeutics, Inc. During the past five years, Dr. Papadopoulos has also served as a director of Anadys Pharmaceuticals, Inc.

Brian S. Posner, 54, has served as one of the Company’s directors since 2008. Mr. Posner has been a private investor since March 2008 and is the President of Point Rider Group LLC, a consulting and advisory services firm within the financial services industry. From 2005 to March 2008, Mr. Posner served as the President, Chief Executive Officer and co-Chief Investment Officer of ClearBridge Advisors LLC, an asset management company and a wholly-owned subsidiary of Legg Mason. Prior to that, Mr. Posner co-founded Hygrove Partners LLC, a private investment fund, in 2000 and served as its Managing Partner for five years. He served as a portfolio manager and an analyst at Fidelity Investments, a financial services company, from 1987 to 1996 and, from 1997 to 1999, at Warburg Pincus Asset Management/Credit Suisse Asset Management where he also served as co-Chief Investment Officer and Director of Research. Mr. Posner is also a director of Arch Capital Group Ltd. and a trustee of AQR Funds. During the past five years, Mr. Posner has also served as a director of the following companies: Anadys Pharmaceuticals, Inc., BG Medi- cine, Inc. and RiverPark Funds.

Eric K. Rowinsky, 59, has served as one of the Company’s directors since 2010. He has served as President of RGenix, Inc., a privately-held life sciences company, since November 2015 and as its Executive Chair- man since December 2015. From January 2012 to November 2015, Dr. Rowinsky was the Head of Re- search and Development and Chief Medical Officer of Stemline Therapeutics, Inc., a biotechnology company focusing on the discovery and development of therapeutics targeting cancer stem cells. Dr. Rowinsky is an Adjunct Professor of Medicine at New York University and has been an independent consultant since January 2010. Prior to that, he was the Chief Medical Officer of Primrose Therapeutics, Inc., a start-up biotechnology company focusing on the development of therapeutics for polycystic kidney disease, from Au- gust 2010 until its acquisition in September 2011. From 2005 to December 2009, he served as the Chief Medical Officer and Executive Vice President of ImClone Systems Incorporated, a life sciences company. From 1996 to 2004, Dr. Rowinsky held several positions at the Cancer Therapy & Research Center’s Insti- tute for Drug Development, including Director of the Institute and Director of Clinical Research. During that time, he held the SBC Endowed Chair for Early Drug Development and Clinical Professor of Medicine at the University of Texas Health Science Center at San Antonio. From 1988 to 1996, Dr. Rowinsky was an Associate Professor of Oncology at the Johns Hopkins School of Medicine and on the staff of the Johns Hopkins Hospital. Dr. Rowinsky is also a director of BIND Therapeutics, Inc., Fortress Biotech Inc. and Navidea Biopharmaceuticals, Inc. During the past five years, Dr. Rowinsky has also served as a director of Mast Therapeutics, Inc. (formerly Adventrx Pharmaceuticals, Inc.).

George A. Scangos, 67, has served as the Company’s Chief Executive Officer and one of its directors since July 2010. Prior to that, he served as the President and Chief Executive Officer of Exelixis, Inc., a drug discovery and development company, from 1996 to July 2010. From 1993 to 1996, Dr. Scangos served as President of Bayer Biotechnology, where he was responsible for research, business development, process

development, manufacturing, engineering and quality assurance of Bayer’s biological products. Before joining Bayer in 1987, Dr. Scangos was a professor of biology at Johns Hopkins University for six years, where he is still an adjunct professor. Dr. Scangos served as non-executive Chairman of Anadys Pharma- ceuticals, Inc., a biopharmaceutical company, from 2005 to July 2010 and was a director of the company from 2003 to July 2010. He also served as the Chair of the California Healthcare Institute in 2010 and was a member of the board of the Global Alliance for TB Drug Development until 2010. Dr. Scangos is also a director of Agilent Technologies, Inc. and Exelixis, Inc.

Lynn Schenk, 71, has served as a director of the Company from 1995 to 2003 during the period the Compa- ny was operated as IDEC Pharmaceuticals, and has served as a director since 2003 following IDEC’s merger with Biogen Inc. Ms. Schenk is an attorney and consultant in private practice with extensive public policy and business experience. She is also a trustee of the Scripps Research Institute, a director of the Califor- nia High Speed Rail Authority Board and a trustee of the University of California, San Diego Foundation. From 1999 to 2003, she served as Chief of Staff to the Governor of California, during which time she led the effort to create the Institutes for Science and Innovation at the University of California. She headed the State’s Executive Branch risk management team post 9/11 and during the California energy crisis. From 1993 to 1995, Ms. Schenk was a Member of the United States House of Representatives, representing San Diego, California and served on the House Energy & Commerce Committee with a special emphasis on biotechnology. From 1980 to 1983, she was the California Secretary of Business, Transportation and Hous- ing during which she formed the California Commission on Industrial Innovation. Ms. Schenk is also a director of Sempra Energy.

Stephen A. Sherwin, 67, has served as one of the Company’s directors since 2010. Dr. Sherwin currently divides his time between advisory work in the life sciences industry and patient care and teaching in his specialty of medical oncology. He is a Clinical Professor of Medicine at the University of California, San Francisco, and a volunteer Attending Physician in Hematology-Oncology at San Francisco General Hospi- tal. Dr. Sherwin previously served as the Chairman of Ceregene, Inc., a life sciences company that he co- founded, from 2001 until its acquisition by Sangamo Biosciences, Inc. in 2013. He was also a co-founder and chairman of Abgenix, Inc., an antibody company which was acquired by Amgen Inc. in 2006. From 1990 to October 2009, he served as the Chief Executive Officer of Cell Genesys, Inc., a life sciences company, and was its Chairman from 1994 until the company’s merger with BioSante Pharmaceuticals, Inc. in October 2009. Prior to that, he held various positions at Genentech, Inc., a life sciences company, most recently as Vice President, Clinical Research. Dr. Sherwin is board certified in internal medicine and medical oncology. He is also a director of Aduro Biotech, Inc., Neurocrine Biosciences, Inc., Rigel Pharmaceu- ticals, Inc. and Verastem, Inc. During the past five years, he has also served as a director of the following companies: Biosante Pharmaceuticals, Inc. and Vical, Inc.

The Company’s Executive Officers as of the date of this prospectus

As of the date of this prospectus the executive officers of the Company and their principal positions are as follows:

Name Current Position Age George A. Scangos, Ph.D. Chief Executive Officer 67 Susan H. Alexander Executive Vice President, Chief Legal Officer and Corporate Sec- 59 retary Spyros Artavanis-Tsakonas, Ph.D. Senior Vice President, Chief Scientific Officer 69 Paul J. Clancy Executive Vice President, Finance and Chief Financial Officer 54 Gregory F. Covino Vice President, Finance and Chief Accounting Officer 50 John G. Cox Executive Vice President, Pharmaceutical Operations and Tech- 53 nology and Interim Global Therapeutic Operations Kenneth DiPietro Executive Vice President, Human Resources 57

Adriana (Andi) Karaboutis Executive Vice President, Technology, Business Solutions and 53 Corporate Affairs Adam Koppel, M.D., Ph.D. Executive Vice President, Strategy and Business Development 46 Alfred W. Sandrock, Jr., M.D., Chief Medical Officer and Executive Vice President of Neurology 58 Ph.D. Discovery and Development

Please see above for Dr. George A. Scangos’ biography.

Susan H. Alexander, 59, has served as the Company’s Executive Vice President, Chief Legal Officer and Corporate Secretary since December 2011. Prior to that, from 2006 to December 2011, Ms. Alexander served as the Company’s Executive Vice President, General Counsel and Corporate Secretary. From 2003 to January 2006, Ms. Alexander served as the Senior Vice President, General Counsel and Corporate Secre- tary of PAREXEL International Corporation, a biopharmaceutical services company. From 2001 to 2003, Ms. Alexander served as General Counsel of IONA Technologies, a software company. From 1995 to 2001, Ms. Alexander served as Counsel at Cabot Corporation, a specialty chemicals and performance materials company. Prior to that, Ms. Alexander was a partner at the law firms of Hinckley, Allen & Snyder and Fine & Ambrogne.

Spyros Artavanis-Tsakonas, PhD, 69, has served as the Company’s Senior Vice President, Chief Scientific Officer since May 2013. Prior to that, Dr. Artavanis-Tsakonas served as the Company’s interim Chief Sci- entific Officer while on sabbatical from Harvard Medical School from March 2012 to May 2013. Dr. Arta- vanis-Tsakonas has been a Professor of Cell Biology at the Harvard Medical School since 1999. From 1999 through 2012, he was Professor, Collège de France, serving as Chair of Biology and Genetics of Develop- ment, and from 1999 to 2007, he was also the K.J. Isselbacher- P. Schwartz Professor at the Massachusetts General Hospital Cancer Center and Director of Developmental Biology and Cancer at the Harvard Medi- cal School. Dr. Artavanis-Tsakonas is the scientific co-founder of Exelixis Pharmaceuticals, Inc., a drug discovery and development company, Cellzome, a drug discovery and development company, and Anadys Pharmaceuticals, Inc., a biopharmaceutical company.

Paul J. Clancy, 54, has served as the Company’s Executive Vice President, Finance and Chief Financial Officer since August 2007. Mr. Clancy joined Biogen, Inc. in 2001 and has held several senior executive positions with the Company, including Vice President of Business Planning, Portfolio Management and U.S. Marketing, and Senior Vice President of Finance with responsibilities for leading the Treasury, Tax, Investor Relations and Business Planning groups. Prior to that, he spent 13 years at PepsiCo, a food and beverage company, serving in a range of financial and general management positions. He is also a director of Agios Pharmaceuticals, Inc. and Incyte Corporation.

Gregory F. Covino, 50, Mr. Covino has served as the Company’s Vice President, Finance and Chief Ac- counting Officer since April 2012. Prior to that, Mr. Covino served at Boston Scientific Corporation, a medical device company, as Vice President, Corporate Analysis and Control since March 2010, having responsibility for the company's internal audit function, and as Vice President, Finance, International from February 2008 to March 2010, having responsibility for the financial activities of the company's international division. Prior to that, Mr. Covino held several finance positions at Hubbell Incorporated, an electri- cal products company, including Vice President, Chief Accounting Officer and Controller from 2002 to January 2008, Interim Chief Financial Officer from 2004 to 2005, and Director, Corporate Accounting from 1999 to 2002.

John G. Cox, 53, Mr. Cox has served as the Company’s Executive Vice President, Pharmaceutical Opera- tions and Technology since June 2010 and has been leading the Company’s Global Therapeutic Operations since October 2015. Mr. Cox joined Biogen, Inc. in 2003 and has held several senior executive positions with the Company, including Senior Vice President of Technical Operations, Senior Vice President of Global Manufacturing, and Vice President of Manufacturing and General Manager of Biogen’s operations in RTP. Prior to that, Mr. Cox held a number of senior operational roles at Diosynth Inc., a life sciences manufacturing and services company, where he worked in technology transfer, validation and purification.

Prior to that, Mr. Cox focused on the same areas at Wyeth Corporation, a life sciences company, from 1993 to 2000. He is also a director of Repligen Corporation.

Kenneth Di Pietro, 57, has served as the Company’s Executive Vice President, Human Resources since January 2012. Mr. DiPietro joined Biogen from Lenovo Group, a technology company, where he served as Senior Vice President, Human Resources from 2005 to June 2011. From 2003 to 2005, he served as Corpo- rate Vice President, Human Resources at Microsoft Corporation, a technology company. From 1999 to 2002, Mr. DiPietro worked as Vice President, Human Resources at Dell Inc., a technology company. Prior to that, he spent 17 years at PepsiCo, a food and beverage company, serving in a range of human resource and general management positions. He is also a director of InVivo Therapeutics Corporation.

Adriana (Andi) Karaboutis, 53, has served as the Company’s Executive Vice President, Technology, Busi- ness Solutions and Corporate Affairs since December 2015 and prior to that served as our Executive Vice President, Technology and Business Solutions since joining Biogen in September 2014. Prior to that, Ms. Karaboutis was Vice President and Global Chief Information Officer of Dell, Inc., where she was responsible for leading a global IT organization focused on powering Dell as an end-to-end technology solutions provider. Prior to joining Dell in 2010, Ms. Karaboutis spent over 20 years at General Motors and Ford Motor Company in various international leadership positions including computer-integrated manufacturing, supply chain operations, and information technology. He is also a director of Advance Auto Parts.

Adam Koppel, M.D., Ph.D., 46, has served as the Company’s Executive Vice President, Strategy and Busi- ness Development since November 2015. Prior to that, Dr. Koppel served as the Company’s Senior Vice President and Chief Strategy Officer from May 2014 to October 2015, responsible for leading corporate strategy and portfolio management. Prior to joining the Company, Dr. Koppel served as a Managing Direc- tor of Brookside Capital, the public-equity affiliate of Bain Capital, since November 2003. Prior to Brookside Capital, he served as Associate Principal with McKinsey & Company, where he consulted to companies in the pharmaceutical and biotechnology industries. Dr. Koppel is also a director of PTC Thera- peutics, Inc. and Trevena, Inc.

Alfred W. Sandrock, Jr., M.D., Ph.D., 58, Dr. Sandrock has served as the Company’s Chief Medical Officer and Executive Vice President of Neurology Discovery and Development since November 2015. Prior to that, Dr. Sandrock served as the Company’s Chief Medical Officer and Group Senior Vice President from May 2013 to October 2015, and as the Company’s Chief Medical Officer and Senior Vice President of De- velopment Sciences from February 2012 to April 2013. Prior to that, Dr. Sandrock held several senior executive positions since joining Biogen in 1998, including Senior Vice President of Neurology Research and Development and Vice President of Clinical Development, Neurology. He is also a director of Neurocrine Biosciences, Inc.

Good Standing of Directors and Executive Officers

For at least the previous five years none of the directors or executive officers of Biogen has been associated with any bankruptcy, receivership or liquidation of a company when acting in their capacity as members of the administrative, management or supervisory board or senior manager of this company or has been subject to any official public incrimination and/or sanctions by statutory or regulatory authorities (including designated professional bodies). None of the directors or executive officers of the Company has ever been disqualified by a court from acting as a member of the administrative, management or supervisory bodies of an issuer or from acting in the management or conduct of the affairs of any issuer or has been convicted in relation to fraudulent offences.

The Company’s directors and executive officers may be contacted at the Company’s business address, 225 Binney Street, Cambridge, Massachusetts 02142, U.S.A.

Potential conflicts between any duties to the issuer of directors or executive officers of the Company and their private interests and/or other duties

The Company’s Code of Business Conduct (Values in Action) and Corporate Governance Principles, both of which are posted on the Company’s corporate website, www.biogen.com under the “Corporate Govern-

ance” subsection of the site, together with the Company’s Conflict of Interest Policy and Related Person Transactions Policy set forth the Company’s policies and procedures for the review and approval of transactions with related persons, including transactions that would be required to be disclosed in a Proxy Statement for an Annual Meeting in accordance with SEC rules. In circumstances where one of the Com- pany’s directors or officers, or a family member, has a direct or indirect material interest in a transaction involving the Company, the Corporate Governance Committee must review and approve all such proposed transactions or courses of dealing. There are no such relationships or transactions that are required to be disclosed in a Proxy Statement for an Annual Meeting under SEC rules. Further, there are no conflicts of interest between duties to the issuer and the private interests of the Company’s directors and executives that require disclosure under the European Prospectus Directive, the German Securities Prospectus Act (Wertpapierprospektgesetz)) and this prospectus. Indeed, the Company’s Code of Business Conduct, which sets forth legal and ethical guidelines for all of the Company’s directors and employees, states that directors, executive officers and employees must avoid relationships or activities that might impair that person’s ability to make objective and fair decisions while acting in their Company roles, and the Company’s Corpo- rate Governance Principles state that the Company’s Board of Directors must approve any waivers of any ethics policy for any director or officer.

There are no family relationships between any of the Company’s directors and/or executive officers.

Disposal restrictions agreed by directors and executive officers of the Company

Directors and executive officers may only sell Company stock pursuant to predetermined written trading plans. Furthermore, these trading plans may only be entered into during trading windows that open after public announcements of quarterly or year-end earnings when the director or executive officer is not aware of any material, non-public information about the Company. The Company also has share ownership guidelines that specifies certain levels of ownership of Company stock to be maintained by directors and executive officers.

TAXATION IN THE FEDERAL REPUBLIC OF GERMANY

The following is a general summary description of the tax consequences of your participation in the ESPP.

This description is based on the tax and other laws concerning equity awards in effect in Germany as of the date of this prospectus. Such laws are often complex and change frequently. As a result, the information contained in this supplement may be out of date at the time you are granted an award, acquire shares or sell shares you acquire under the ESPP.

In addition, this description does not discuss all of the various laws, rules and regulations that may apply. It may not apply to your particular tax or financial situation, and Biogen is not in a position to assure you of any particular tax result. Accordingly, you are strongly advised to seek appropriate professional advice as to how the tax or other laws in your country apply to your specific situation. You are also advised to seek advice with respect to U.S. inheritance and/or estate taxes as you may be subject to those with respect to shares acquired under the ESPP.

If you are a citizen or resident of a country other than Germany, the information contained in this description may not be applicable to you.

Note: The particular terms of any awards granted to you under the ESPP are set forth in the applicable plan and award agreement (“Plan Documents”). If there is an inconsistency between the description below and your Plan Documents, the Plan Documents will take precedence. As stated in your Plan Documents, the ability to participate in the ESPP is neither a contract nor a guarantee of continued employment; employment is and always will be on the basis as provided for in your employment agreement. The ESPP is not part of your salary and will not be included in calculations of any severance payments that may be payable upon termination of employment.

Enrollment in the ESPP

You are not subject to tax when a Purchase Right is granted to you under the ESPP (i.e., when you enroll in the ESPP or are offered participation in the ESPP).

Purchase of Shares

When shares are purchased, you will be subject to income tax (plus solidarity surcharge and church tax, if applicable). According to the official position of German tax authorities, the taxable amount is the difference (or discount) between the fair market value of the shares on the date of purchase and the purchase price. You also will be subject to social insurance contributions on the discount to the extent you have not already exceeded your applicable contribution ceiling.

A tax free amount of €360 might be available if the ESPP meets certain requirements. The availability of the tax free amount, in principle, requires that the participation in the ESPP is offered to all employees of the German subsidiary, who have been employed for one year or more at the time when the participation in the ESPP is offered. Whether or not the tax free amount of €360 is available in the case at hand requires a more detailed analysis of the ESPP and its implementation. Under certain circumstances and provided the aforementioned tax free amount is not available, you might still be able to deduct the lesser of €135 per year, or 50% of the value of the shares on the date on which such shares are debited from the Company’s books, from the income realized at exercise. The Company recommends that you confirm the availability of this deduction or of the tax-free amount, respectively, with your personal tax advisor.

Sale of Shares

When you subsequently sell the shares that you purchased under the ESPP, any capital gain, (i.e., the difference between the sale price and the fair market value of the shares at the time of purchase, less costs directly related to the sale) will in principle be subject to a withholding tax on income from capital investments at a flat rate of 25% (plus solidarity surcharge and church tax, if applicable). The withholding at source, however, only applies if the shares were held in a deposit of securities at a German bank or other

German financial institution. Biogen does not assume any responsibility to withhold German income tax, etc. on the capital gain. An annual tax-free amount for the entire investment income, including inter alia dividends and capital gains from the sale of shares, of €801 applies for single taxpayers or €1,602 for married taxpayers and for partners within the meaning of the registered partnership law (Gesetz über die Eingetragene Lebenspartnerschaft) filing jointly, respectively. If the flat tax rate exceeds your personal income tax rate, you may elect a personal assessment to apply your personal income tax rate. If the capital gain is not subject to the flat rate withholding tax on investment income, e.g. because the shares are not held in a deposit of securities at a German bank or other German financial institution, you have to declare the capital gain in your personal income tax return as taxable income and pay the arising tax yourself. The capital gain is, however, subject to the same tax rates as if the flat rate withholding taxation had applied. If you hold the shares which you purchased under the ESPP as business assets or if you own 1% or more of the Company’s stated capital (or have owned 1% or more at any time in the last five years), 60% of the capital gain is subject to taxes at your personal income tax rate.

Dividends

Any dividend payments that you receive are in principle subject to a flat rate tax of 25% on the full amount of the dividend payment (plus solidarity surcharge and church tax, if applicable). As a matter of principle, the flat tax is to be withheld at the source. Biogen does not assume any responsibility to withhold German income tax on dividends, etc. at source. The annual tax-free amount for investment income, including inter alia dividends and capital gains from the sale of shares, amounts to €801 for single taxpayers or €1,602 for married taxpayers and for partners within the meaning of the registered partnership law (Gesetz über die Eingetragene Lebenspartnerschaft) filing jointly, respectively. If the flat tax rate exceeds your personal income tax rate, you may elect a personal assessment to apply your personal income tax rate. The withholding at source, however, only applies if the dividend income is paid out by a German bank or other German financial institution, e.g. because the shares are held on a deposit of securities at a German bank or other German financial institution. If the dividend payment is not subject to the flat rate withholding tax on investment income, you have to declare the dividend income in your personal income tax return as taxable income and pay the arising tax yourself. The dividend income is, however, subject to the same tax rates as if the flat rate withholding taxation had applied. Dividends may also be subject to U.S. federal income tax withholding at source. U.S. federal tax withholding taxes on the dividends may be credited. The Company does not assume any responsibility to withhold taxes at source.

Withholding and Reporting

Your employer will withhold income tax, solidarity surcharge and church tax, if applicable on the discount upon the purchase of shares. However, you are responsible for paying any difference between the actual tax liability and the amount withheld. It is your responsibility to pay and report any taxes due when you sell shares acquired under the ESPP or when you receive dividends, unless the flat rate withholding tax on investment income does apply.

Social Security

Your employer will withhold social insurance contributions (to the extent that you have not exceeded your applicable ceiling for social insurance contributions) when shares are purchased for you under the ESPP.

TAXATION IN THE UNITED KINGDOM

The following is a general summary description of the tax consequences of your participation in the ESPP.

This description assumes that you are always resident and domiciled in the U.K. The tax implications may differ if you are not always resident and domiciled in the U.K.

This description is based on the tax and other laws concerning equity awards in effect in the U.K. as of the date of this prospectus. Such laws are often complex and change frequently. As a result, the information contained in this supplement may be out of date at the time you are granted an award, acquire shares or sell shares you acquire under the ESPP.

In addition, this description does not discuss all of the various laws, rules and regulations that may apply. It may not apply to your particular tax or financial situation, and Biogen is not in a position to assure you of any particular tax result and this description does not constitute tax advice. Accordingly, you are strongly advised to seek appropriate professional advice as to how the tax or other laws in your country apply to your specific situation. You are also advised to seek advice with respect to U.S. inheritance and/or estate taxes as you may be subject to those with respect to shares acquired under the ESPP.

If you are a citizen or resident of a country other than the U.K., the information contained in this description may not be applicable to you.

Note: The particular terms of any awards granted to you under the ESPP are set forth in the applicable plan and award agreement (the “Grant Documents”). If there is an inconsistency between the description below and your Grant Documents, the Grant Documents will take precedence. As stated in your Grant Docu- ments, the ability to participate in the ESPP is neither a contract nor a guarantee of continued employment; employment is and always will be on the basis as provided for in your employment agreement. The ESPP is not part of your salary and will not be included in calculations of any severance payments that may be payable upon termination of employment.

Enrollment in the ESPP

You are not subject to tax when an option is granted to you under the ESPP (i.e., when you enroll in the ESPP or are offered participation in the ESPP).

Purchase of Shares

You will be subject to income tax on the amount by which the market value of the shares on the purchase date exceeds the purchase price (the “spread”). Income tax will be due on the spread at your marginal income tax rate, depending on your cumulative annual earnings. In addition, you will be subject to employee’s national insurance contributions (“NICs”) on the spread. For the tax year 6 April 2016 to 5 April 2017, employee NICs are due at a rate of 12% to the extent that your earnings exceed £155 per week, up to the upper earnings limit of £827 per week. To the extent you have exceeded the upper earnings limit, you will be subject to employee's NICs at a rate of 2% for the tax year 2016/2017.

You are ultimately responsible for the payment of any income tax and employee's NICs due. Your employer will calculate the income tax and employee's NICs due when shares are purchased for you under the ESPP and will account for these amounts to HM Revenue & Customs (“HMRC”). You are required to reimburse your employer for the amounts accounted by it to HMRC. Your employer may withhold these amounts from your monthly salary. If the total amount of income tax and employee's NICs due when shares are purchased exceeds your salary, you will have to make up for the difference either through the sale of shares or use of other funds. Alternatively, the Company may sell or arrange for the sale of the shares that you acquire under the ESPP to cover these amounts. To the extent that there is no or insufficient withholding, you must reimburse your employer for the income tax due within 90 days after the end of the U.K. tax year in which the shares were purchased. If you fail to pay this amount to your employer within the time limit, you may be deemed to have received a benefit in kind equal to the amount of any income tax not re-

covered from you and you may have to pay further income tax and employee's NICs on this benefit in kind. The Company may refuse to deliver your shares until all such amounts have been repaid or recovered.

Sale of Shares

When you subsequently sell your shares acquired under the ESPP, you will be subject to capital gains tax on any increase in the value of the shares between the date of purchase of the shares and the date of sale, subject to your personal annual exemption.

Capital gains tax is payable on gains from all sources in excess of the personal annual exemption in any tax year. The personal annual exempt amount is £11,100 for the tax year 2015/2016.

A capital gains tax rate of 28% is payable on the amount of any gain (or any parts of gains) that exceeds the upper limit of the income tax basic rate band when aggregated with your cumulative taxable income and other chargeable gains in any tax year. For the 2016/2017 tax year, the upper limit of the income tax basic rate band is £32,000 (after the deduction of the annual income tax personal allowance). Below this limit, capital gains tax is payable at a rate of 18%.

If you have acquired shares in the Company at different times, whether pursuant to the ESPP or otherwise, all of the shares of the same class you have acquired will be treated as forming a single asset (a share pool). The base cost will then be calculated on a pro rata basis. One exception to this is that any shares acquired on the same day as you sell any shares and those acquired within the following 30 days will be treated as being disposed of first. Disposals are therefore taken to be made in the following order: (i) against acquisitions on the same day; (ii) against acquisitions within the 30 days following the disposal; and (iii) against shares in the share pool. The capital gains tax rules are complex and their impact will vary according to your own circumstances. We recommend that you obtain independent tax advice before selling your shares.

You will be responsible for reporting and paying any UK capital gains tax liability to HMRC through your annual self-assessment tax return.

Dividends

If you hold shares of Company stock and the Company declares a dividend on the shares, you will be subject to income tax on dividend payments that you receive. (No NICs are due on dividends.) Any dividends paid will be subject to U.S. federal tax withheld at source, although you may be able to arrange for dividends to be paid to you without U.S. federal tax being withheld. The Company will not withhold any U.K. income tax at source and you must account for U.K. income tax due through your annual U.K. self assessment tax return. You may be entitled to a tax credit against your U.K. income tax for any U.S. federal tax withheld, which you may apply to HMRC for through your annual self-assessment tax return.

From April 2016, the dividend tax credit will be abolished and replaced with a new £5,000 tax-free dividend allowance. The effects of this change will depend on your individual circumstances as dividend income in excess of £5,000 will be subject to income tax at rates of between 7.5% and 38.1%.

Withholding and Reporting

As mentioned above, your employer is required to account for and report income tax and employee’s NICs on the spread when shares are purchased under the ESPP. If the amount withheld is not sufficient to cover your actual liability, you will be responsible for paying the difference and should do so within 90 days after the end of the U.K. tax year in which the shares were purchased to avoid liability to additional income tax and employee's NICs (as discussed above).

In addition, you will be responsible for paying directly to HMRC any taxes owed as a result of any dividends received or the sale of the shares.

You will also be required to report any dividends received and any capital gains tax that arises on the subsequent disposal of your shares to HMRC on your annual self-assessment tax return. You may also have an obligation to report your capital gains in other circumstances.

TAXATION IN FRANCE

The following is a general summary description of the tax and social security consequences of your participation in ESPP.

This description is based on the tax and other laws concerning equity awards in effect in France as of the date of this prospectus. Such laws are often complex and change frequently. As a result, the information contained in this supplement may be out of date at the time you are granted an award, acquire shares or sell shares you acquire under the ESPP.

In addition, this description does not discuss all of the various laws, rules and regulations that may apply. It may not apply to your particular tax, social security contributions or financial situation, and Biogen is not in a position to assure you of any particular tax result. Accordingly, you are strongly advised to seek appropriate professional advice as to how the tax or other laws in your country apply to your specific situation. You are also advised to seek advice with respect to U.S. inheritance and/or estate taxes as you may be subject to those with respect to shares acquired under the ESPP.

If you are a citizen or resident of another country or transfer your tax residence out of France after your enrollment into the ESPP and/or if you are not subject to the French social security regime, the information contained in this description may not be applicable to you.

Enrollment in the ESPP

You are not subject to tax or to social security contributions when a Purchase Right is granted to you under the ESPP (i.e., when you enroll in the ESPP or are offered participation in the ESPP).

Purchase of Shares

When shares are purchased under the ESPP, you are subject to social security contributions (paid partly by the employer and partly the employee), including CSG (Contribution sociale généralisée) and CRDS (Con- tribution à la réduction de la dette sociale), on the difference (the “gain”) between the fair market value of the shares on the date of purchase and the purchase price. This gain is also subject to personal income tax at your marginal rate (up to 45% for 2015 income2), after deduction of the tax deductible social security contributions and if applicable, a surtax on high income of 3% and/or 4% (see below).

Dividends

You will be subject to progressive personal income tax (up to 45%), plus a surtax on high income of 3% and/or 4% (see below) on any dividends paid to you on the shares you acquire under the ESPP, after application of certain allowances. The gross amount of the dividends is also subject to the 15.5% additional social taxes.

At the time of the payment, you will be subject to a prepayment of French personal income tax at a rate of 21% on the gross amount of dividends received and to payment of the French additional social taxes at a global rate of 15.5% due by the 15th day of the month following payment of the dividend, unless you benefit from an exemption of the prepayment,. Until the shares are held in the books of a non-French broker, you are personally responsible for paying and reporting any tax liabilities in that respect. In any case, you will have to directly report the dividends in your annual tax return due the year following payment of the dividends and you may pay additional income tax (or be reimbursed in case of surplus of income tax pre- paid). Biogen has no obligation to withhold French taxes at source.

In addition, you will be subject to U.S. income tax withholding at source, and may be entitled to a foreign tax credit for these amounts, if the formalities required pursuant to the August 31, 1994 tax treaty to eliminate double taxation, entered into between France and the U.S., are fulfilled. Such tax credit can be offset

2 The scale of the French progressive income applicable to income realized in 2016 could be amended until the very end of 2016. As of today, the marginal rate is 45%.

against the personal income tax at progressive rates. Biogen does not assume any responsibility to withhold taxes at source.

Sale of Shares

When the shares you acquired pursuant to the ESPP are later sold, the positive difference between the net sale price and the fair market value of the shares on the date of purchase (the “capital gain”) is subject to progressive personal income tax (up to 45% for 2015).

You may benefit from a rebate for holding period for personal income tax purposes only (but not for social taxes):

 If the shares you acquired pursuant to the ESPP are held for at least two years and less than eight years, the capital gain tax basis will be reduced by a rebate of 50%;  If the shares you acquired pursuant to the ESPP are held at least for eight years, the capital gain tax basis will be reduced by a rebate of 65%.

You may realize a capital loss if the net sale price for the shares is lower than the fair market value on the date of purchase. This capital loss can be offset against capital gain of the same nature realized by you and your household during the same year or during the ten following years. A capital loss cannot be offset against other kind of income (such as salary or the gain you realized upon purchase of the shares under the ESPP).

On top of your personal income tax, the capital gains tax basis (before application of the above rebate for holding period) is also subject to the 15.5% additional social taxes. 5.1% of CSG (from the 15.5% additional social taxes) paid the year following the sale of the shares are tax deductible from the income realized the year of payment of the CSG.

You are invited to consult your personal tax advisor prior to selling your shares and filing the relevant personal income tax return to determine the taxable amount.

Specific surtax may apply - see below.

Surtax

A surtax (at rates of 3% and/or 4%, depending on your total income) applies to your annual income in excess of certain thresholds (€250,000 for single taxpayers and €500,000 for married taxpayers for the 3% and twice the amount for the 4%), including income realized upon the purchase or sale of shares. Please contact your personal tax advisor to determine if you will be subject to surtax and whether you qualify for any available surtax reductions.

Wealth Tax

Any shares you acquire under the ESPP will be included in your personal estate and must be declared to the French tax authorities if the net amount of your taxable personal estate (including you and your household) exceeds the exempt amount for the calendar year (€1.3 million for 2016), as valued on January 1 of each year. You may be able to claim a partial exemption for the value of the shares if you hold the shares for a certain number of years. Please consult your personal tax advisor to determine whether you can claim this exemption.

Withholding and Reporting

Your employer is not required to withhold personal income tax when shares are purchased under the ESPP or when you subsequently sell shares purchased under the ESPP, provided that you are a French resident for tax purposes from grant to sale.

However, because the income realized upon the purchase of shares qualifies as additional salary under French tax and social security law, your employer is required to report this income on your pay slip of the

month following the purchase of the shares (or the month after) and on its annual declaration of salaries which is filed with the social authorities at the latest on January 31 of the year following the purchase of the shares . Also, your employer will pay the employer’s portion of social security contributions and withhold your portion of social security contributions due at purchase from your pay.

You are responsible for paying any taxes and additional social taxes resulting from the purchase, the sale of shares and the receipt of dividends under the ESPP. You are also responsible for reporting the additional salary, any capital gains/losses and dividends realized under the ESPP on your personal income tax return to be filed with the French tax administration in the year following the year of purchase, sale or receipt of dividends, as applicable.

TAXATION IN DENMARK

The following is a general summary description of the tax consequences of your participation in the ESPP.

This description is based on the tax and other laws concerning equity awards in effect in Denmark as of the date of this prospectus. Such laws are often complex and change frequently. As a result, the information contained in this supplement may be out of date at the time you are granted an award, acquire shares or sell shares you acquire under the ESPP.

In addition, this description does not discuss all of the various laws, rules and regulations that may apply. It may not apply to your particular tax or financial situation, and Biogen Inc. is not in a position to assure you of any particular tax result. Accordingly, you are strongly advised to seek appropriate professional advice as to how the tax or other laws in your country apply to your specific situation. You are also advised to seek advice with respect to U.S. inheritance and/or estate taxes as you may be subject to those with respect to shares acquired under the ESPP.

If you are a citizen or resident of country other than Denmark, the information contained in this description may not be applicable to you.

Note: The particular terms of any awards granted to you under the ESPP are set forth in the applicable plan and award agreement (“Plan Documents”). If there is an inconsistency between the description below and your Plan Documents, the Plan Documents will take precedence. As stated in your Plan Documents, the ability to participate in the ESPP is neither a contract nor a guarantee of continued employment; employment is and always will be on the basis as provided for in your employment agreement. The ESPP are not part of your salary and will not be included in calculations of any severance payments that may be payable upon termination of employment.

Enrollment in the ESPP

You are not subject to tax when a Purchase Right is granted to you under the ESPP (i.e., when you enroll in the ESPP or are offered participation in the ESPP).

Purchase of Shares

When shares are purchased, you will be subject to personal income tax (of up to 51.95%) (2016) on the difference (or spread) between the fair market value of the shares on the date of purchase and the purchase price. You also will be subject to the Danish labor market contribution of 8%. The labor market contribution is deductible in your personal income, and the effective marginal tax rate is therefore 55.8 %.

Sale of Shares

Upon sale of shares, the gain is taxed as share income. Gains below DKK 50,600 (in 2016) are taxed at a rate of 27%, and gains above this amount are taxed at a rate of 42%. Married couples may use any unused threshold of the spouse.

Dividends

Dividends paid to individuals are taxed as share income at the rates listed above under “Sale of Shares”. Biogen Inc. does not assume any responsibility to withhold tax at source.

Withholding and Reporting

The Danish employer company must report the value of any Purchase Rights exercised under the ESPP. There is no withholding of tax in connection with the exercise. You are therefore required to pay the applicable taxes yourself (and these will be calculated by the tax authorities).

When you subsequently sell the shares purchased under the ESPP, you must inform the tax authorities of any gain (and pay the applicable tax) in connection with the sale of the shares.

TAXES ON THE INCOME FROM THE SECURITIES WITHHELD AT SOURCE UNDER US FEDERAL TAX LAWS

Fidelity requires all non-U.S. employees to certify their foreign status by completing a W8-BEN form at the time of account activation. The purpose of this form is to allow Fidelity to waive the U.S. Internal Revenue Service-required 30% backup tax withholding on the gross proceeds of any sale transaction. It also can lower the percent withheld on any cash dividends received to the specific tax treaty rate between the non- U.S. employee’s country and the U.S. The form expires every three years on 31 December, and while renewal is not mandatory, a recertification would need to be made prior to the expiration date of the form to allow Fidelity to waive the required backup tax withholding and to obtain the benefits of any applicable tax treaty. Participants can also update their certification status with Fidelity if their foreign status changes at any time.

The Company does not have any responsibility for the withholding of taxes at source.

RECENT DEVELOPMENTS AND TREND INFORMATION

Recent Developments since December 31, 2015

There has been no significant change in the Company’s financial or trading position which has occurred since December 31, 2015.

However, the following significant events have happened since December 31, 2015:

In January 2016, the EC approved the MAA for BENEPALI, an etanercept biosimilar referencing ENBREL, for marketing in the E.U. Under the Company’s agreement with Samsung Bioepis, Biogen will manufacture and commercialize BENEPALI in specified E.U. countries.

Trend Information

General Overview

The Company’s current revenues depend upon continued sales of its principal products. The Company may be substantially dependent on sales from its principal products for many years, including an increasing reliance on sales of TECFIDERA as the Company further expands into additional markets. Sales of the Com- pany’s products depend, to a significant extent, on adequate coverage, pricing and reimbursement from third party payors, which are subject to increasing and intense pressure from political, social, competitive and other sources.

The biopharmaceutical industry and the markets in which the Company operates are intensely competitive. Many of the Company’s competitors are working to develop or have commercialized products similar to those Biogen markets or are developing. In addition, the commercialization of certain of the Company’s own approved MS products, products of its collaborators and pipeline product candidates may negatively impact future sales of the Company’s existing MS products. The Company’s products may also face increased competitive pressures from the introduction of generic versions, prodrugs of existing therapeutics or biosimilars of existing products and other technologies, such as gene therapies.

In the longer term, the Company’s revenue growth will be dependent upon the successful clinical development, regulatory approval and launch of new commercial products as well as additional indications for the Company’s existing products, its ability to obtain and maintain patents and other rights related to its marketed products and assets originating from the Company’s research and development efforts, and successful execution of external business development opportunities. As part of its ongoing research and development efforts, the Company intends to continue committing significant resources to targeted research and development opportunities where there is a significant unmet need and where the drug candidate has the potential to be highly differentiated. Specifically, the Company intends to continue to invest in its MS pipeline, its programs for Alzheimer’s disease (aducanumab, BAN2401 and E2609), the nusinersen program for the treatment of spinal muscular atrophy, the amiselimod program for development of product candidates for multiple autoimmune indications and its Raxatrigine program for development of product candidates for neuropathic pain.

Healthcare Cost and Reform

In the U.S., federal and state legislatures, health agencies and third-party payors continue to focus on containing the cost of health care. Legislative and regulatory proposals, enactments to reform health care insurance programs and increasing pressure from social sources could significantly influence the manner in which the Company’s products are prescribed and purchased. It is possible that additional federal health care reform measures will be adopted in the future, which could result in increased pricing pressure and reduced reimbursement for the Company’s products and otherwise have an adverse impact on the Compa- ny’s financial position or results of operations.

Governments in some international markets in which the Company operates have implemented measures aimed at reducing healthcare costs to constrain the overall level of government expenditures. These imple-

mented measures vary by country and include, among other things, mandatory rebates and discounts, prospective and possible retroactive price reductions and suspensions on price increases of pharmaceuticals.

In addition, certain countries set prices by reference to the prices in other countries where the Company’s products are marketed. Thus, the Company’s inability to secure favorable prices in a particular country may impair its ability to obtain acceptable prices in existing and potential new markets and limit market growth. The continued implementation of pricing actions throughout Europe may also lead to higher levels of paral- lel trade.

There is also significant economic pressure on state budgets that may result in states increasingly seeking to achieve budget savings through mechanisms that limit coverage or payment for the Company’s drugs. Managed care organizations are also continuing to seek price discounts and, in some cases, to impose restrictions on the coverage of particular drugs.

Product Development

Additional information about the Company’s late stage product candidates, which includes programs in Phase 3 development or in registration stage, and certain other important programs, is set forth below.

Multiple Sclerosis

ZINBRYTA (daclizumab high yield process)

ZINBRYTA is a monoclonal antibody for the treatment of RRMS. In June 2014, the Company announced positive top-line results from the Phase 3 DECIDE clinical trial, which investigated ZINBRYTA as a potential once-monthly, subcutaneous treatment for RRMS. Results showed that ZINBRYTA was superior on the study's primary endpoint, demonstrating a statistically significant reduction in annualized relapse rates when compared to interferon beta-1a. The Company’s MAA for ZINBRYTA was validated by the EMA in March 2015, and the BLA was accepted by the FDA in April 2015.

TYSABRI (natalizumab)

In May 2013, the Company completed patient enrollment in a Phase 3 study of TYSABRI in secondary progressive MS, known as ASCEND. The study had a duration of approximately two years and involved approximately 875 patients. SPMS is characterized by a steady progression of nerve damage, symptoms and disability. In October 2015, the results of the Company’s Phase 3 ASCEND study did not achieve its primary and secondary endpoints, and the development of TYSABRI in secondary progressive MS was discontinued.

Hemophilia

ALPROLIX (Coagulation Factor IX (Recombinant), Fc Fusion Protein)

In March 2014, ALPROLIX was approved by the FDA for the treatment of hemophilia B. Pediatric data was required as part of the MAA for ALPROLIX that the Company submitted to the EMA. In February 2015, Biogen and SOBI announced positive top-line results of the Kids B-LONG Phase 3 clinical study that evaluated the safety, efficacy and pharmacokinetics of ALPROLIX in children under age 12 with severe hemophilia B. Following these results, Biogen filed a MAA in the E.U., which was validated by the EMA in June 2015. In March 2016, the Company and its collaboration partner, Swedish Orphan Biovitrum AB (publ), received a positive opinion from the Committee for Medicinal Products for Human Use of the EMA recommending that marketing authorisation be granted for ALPROLIX for the treatment of hemophilia B.

Neurodegeneration

Aducanumab (BIIB037)

In September 2015, the Company enrolled its first patient in its two global Phase 3 studies, ENGAGE and EMERGE. ENGAGE and EMERGE will assess the efficacy and safety of aducanumab in approximately 2,700 people with early Alzheimer's disease. The studies are identical in design and eligibility criteria. Each study will be conducted in more than 20 countries in North America, Europe and Asia. In October 2015, the Company announced that it received FDA agreement on a special protocol assessment on the Phase 3 study protocols.

Other programs

Nusinersen (IONIS-SMNRx)

In August 2014, Ionis Pharmaceuticals, a collaboration partner of the Company, announced the initiation of a pivotal Phase 3 study evaluating nusinersen in infants with “SMA”, the most common genetic cause of infant mortality. This Phase 3 study, known as ENDEAR, is a randomized, double-blind, sham-procedure controlled thirteen month study in approximately 110 infants diagnosed with SMA. The study is evaluating the efficacy and safety of a 12mg dose of nusinersen with a primary endpoint of survival or permanent ven- tilation.

In November 2014, Ionis Pharmaceuticals announced the initiation of a pivotal Phase 3 study evaluating the efficacy and safety of nusinersen in non-ambulatory children with SMA. This Phase 3 study, known as CHERISH, is a randomized, double-blind, sham-procedure controlled fifteen month study in approximately 120 children with SMA. The study is evaluating the efficacy and safety of a 12mg dose of nusinersen with a primary endpoint of a change in the Hammersmith Functional Motor Scale-Expanded, a validated method to measure changes in muscle function in patients with SMA.

Genentech Relationships

GAZYVA (obinutuzumab)

The Roche Group is managing the following Phase 3 studies of GAZYVA:

 GOYA: investigating the efficacy and safety of GAZYVA in combination with CHOP chemotherapy compared to RITUXAN with CHOP chemotherapy in previously untreated patients with CD20-positive diffuse large B-cell lymphoma.  GALLIUM: investigating the efficacy and safety of GAZYVA in combination with chemotherapy followed by maintenance with GAZYVA compared to RITUXAN in combination with chemotherapy followed by maintenance with RITUXAN in previously untreated patients with indolent non-Hodgkin's lymphoma.  GADOLIN: investigating the efficacy and safety of GAZYVA plus bendamustine compared with bendamustine alone in patients with RITUXAN-refractory, indolent non-Hodgkin's lymphoma. In February 2015, the Roche Group announced positive results from the Phase 3 GADOLIN study. At a pre-planned interim analysis, an independent data monitoring committee determined that the study met its primary endpoint early, showing that people lived significantly longer without disease worsening or death (progression-free survival) when treated with GAZYVA plus bendamustine followed by GAZYVA alone, compared to bendamustine alone. In February 2016, the Roche Group announced the FDA approved GAZYVA plus bendamustine chemotherapy followed by GAZYVA alone as a new treatment for people with follicular lymphoma who did not respond to a RITUXAN-containing regimen, or whose follicular lymphoma returned after such treatment.

Ocrelizumab

In June 2015, the Roche Group announced positive results from two Phase 3 studies evaluating ocrelizumab compared with interferon beta-1a in people with relapsing forms of MS. Treatment with ocrelizumab compared with interferon beta-1a significantly reduced the annualized relapse rate over a two-year period; significantly reduced the progression of clinical disability; and led to a significant reduction in the number of lesions in the brain as measured by MRI.

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In September 2015, the Roche Group announced positive results from a Phase 3 study evaluating ocrelizumab in people with PPMS. Treatment with ocrelizumab significantly reduced the progression of clinical disability compared with placebo, as measured by the Expanded Disability Status Scale.

Biosimilars (Samsung Bioepis - Biogen's Joint Venture with Samsung Biologics)

Samsung Bioepis' MAA for FLIXABI, an infliximab biosimilars candidate referencing REMICADE, was validated and accepted by the EMA in March 2015. If approved, under the Company’s agreement with Samsung Bioepis, Biogen has commercialization rights to FLIXABI in specified E.U. countries.

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GLOSSARY/LIST OF DEFINED TERMS

Abbreviation English term German term AIFA (Agenzia Ital- Italian National Medicines Agency iana del Farmaco) ANCA antineutrophil cytoplasmatic antibodies anti-neutrophile cytoplasmatische Antikörper Bayer Bayer Healthcare Pharmaceuticals Inc. BEPS Base Erosion and Profit Shifting BIH Biogen Hemophilia Inc. BIN Biogen International Neuroscience GmbH Biogen / Company / Biogen Inc. (formerly Biogen Idec Inc.) Biogen Inc. (vormals Biogen Idec Inc.) die Gesellschaft cGMP Current Good Manufacturing Practices CLL chronic lymphocytic leukemia chronisch-lymphatische Leukämie Convergence Convergence Pharmaceuticals CROs contract research organizations CUSIP U.S. security identification number US-Wertpapieridentifikationsnummer DGCL The General Corporation Law of the State of Delaware (US) 2006 Directors Plan Biogen Inc. 2006 Non-Employee Directors Equity Plan EC European Commission Europäische Kommission Eisai Eisai Inc. Elan Elan Pharma International, Ltd Eligible Employee Employees of Biogen or any of its designated Teilnahmeberechtigte Mitarbeiter subsidiaries who is eligible to participate in the ESPP. EMA European Medicines Agency ESPP Biogen Inc. 2015 Employee Stock Purchase Mitarbeiteraktienkaufplan der Biogen Inc. von Plan 2015 E.U. / EU European Union Europäischen Union FDA U.S. Food and Drug Administration US-amerikanischen Arzneimittelbehörde Fidelity Fidelity Investments® Fidelity Investments® Forward Pharma Forward Pharma A/S Fumapharm Products FUMADERM and TECFIDERA Genentech Genentech Inc. Grant Documents The applicable plan and award agreement of the ESPP. HMRC HM Revenue & Customs ISIN International Securities Identification Number internationale Wertpapieridentifikationsnummer Kommission European Commission Europäische Kommission MAA marketing authorization application MS multiple sclerosis Multiple Sklerose NASDAQ NASDAQ Global Select Market NASDAQ Global Select Market NICs national insurance contributions Offering Period Time periods during which the Company’s Angebotszeitraum common stock is offered for purchase under the ESPP. 2008 Omnibus Plan Biogen Inc. 2008 Omnibus Equity Plan Ownership Date February 18, 2016 Participant Each Eligible Employee participating in the Teilnehmer ESPP.

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Abbreviation English term German term ‘127 patent The Company’s European Patent Number 1 485 127 (“Administration of agents to treat inflammation”) '514 patent The Company’s U.S. Patent No. 8,399,514 ‘537 patent The Company’s European patent number 2 137 537 ‘755 patent The Company’s U.S. Patent No. 7,588,755 Plan Administrator The Compensation and Management Devel- Planverwalter opment Committee of the Company’s Board of Directors, which administers the ESPP. Plan Documents The applicable plan and award agreement of the ESPP. PML progressive multifocal leukoencephalopathy Purchase Date The last business day of each Offering Period. Kauftag Purchase Price The purchase price of shares of common stock Kaufpreis issued pursuant to the exercise of a Purchase Right on the Purchase Date under the ESPP. Purchase Right The participating Eligible Employees’ right to Erwerbsrecht purchase common stock under the ESPP. PPACA Patient Protection and Affordable Care Act Price Resolution A price determination resolution granted by AIFA in December 2006 PwC PricewaterhouseCoopers LLP Roche Group Roche Group Roche Gruppe RRMS relapsing-remitting multiple sclerosis schubweise-remittierende Multiple Sklerose RSUs restricted stock units RTP Research Triangle Park Samsung Biologics Samsung BioLogics Co. Ltd. SEC U.S. Securities and Exchange Commission 2011 Share Repur- The Company’s program to repurchase up to chase Program 20.0 million shares of the Company’s common stock authorized in February 2011 2015 Share Repur- The Company’s program to repurchase up to chase Program $5.0 billion of the Company’s common stock authorized in May 2015 SMA spinal muscular atrophy Stromedix Stromedix, Inc. Tysabri A monoclonal antibody approved in numerous countries as a monotherapy for the treatment of patients with relapsing forms of MS. U.S. / US / USA United States Vereinigten Staaten von Amerika USD / U.S.$ / $ U.S. Dollar US-Dollar U.S. GAAP accounting principles generally accepted in the Die in den Vereinigten Staaten von Amerika an- United States of America erkannten Grundsätzen ordnungsgemäßer Buch- führung USPTO United States Patent and Trademark Office Patentamt der Vereinigten Staaten von Amerika

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Cambridge, Massachusetts, USA

March 24, 2016

Biogen Inc. by signed

Steven N. Avruch Chief Corporation Counsel

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