3/30/2019 Investors - News Release - Portola Pharmaceuticals, Inc.

News Release

Portola Pharmaceuticals Expands Clinical Collaboration Agreement with Daiichi Sank Worth Up to $25 Million to Develop AndexXa™ () in Germany

SOUTH SAN FRANCISCO, Calif., Nov. 01, 2016 (GLOBE NEWSWIRE) -- Portola Pharmaceuticals Inc.® (Nasdaq:PTLA) tod announced that it has expanded its existing clinical collaboration agreement with to develop AndexXa (andexanet alfa) as an antidote for edoxaban, Daiichi Sankyo’s Factor Xa inhibitor. AndexXa is currently under EMA re reversal of Factor Xa inhibition in patients experiencing a life-threatening or uncontrolled bleed and for patients requ urgent or emergency surgery. As part of the updated agreement, Portola will expand the ongoing ANNEXA-4 study in patients in Germany.

“As an industry, we need to address the signicant unmet medical need for managing Factor Xa inhibitor-related ma bleeding by bringing to market an antidote that specically reverses anti-Factor Xa activity, the mechan these agents. With this support from Daiichi Sankyo, we will be able to improve our ability to gather data on AndexXa reversal agent for edoxaban. Germany is the second largest market for Factor Xa inhibitors and one where edoxaba experienced signicant growth,” said Tao Fu, chief commercial and business ocer of Portola. “Our long-standing collaboration with Daiichi Sankyo, as well as all of the other manufacturers of Factor Xa inhibitors, demonstrates the condence these companies have in the AndexXa program.”

Under the terms of the non-exclusive agreement with Daiichi Sankyo, Portola will receive a $15 million upfront paym is eligible to receive up to an additional $10 million upon meeting site initiation and enrollment targets. Upon Andex approval, Daiichi Sankyo will be eligible to receive a low single-digit royalty on AndexXa sales up to a total of $8 millio

Portola previously entered into nine separate non-exclusive clinical collaboration agreements with Daiichi Sankyo, B Pzer, and Janssen to support Phase 2 and registrational studies of AndexXa in the United States, Europe and Portola retains all rights, including full commercial and nancial rights, for AndexXa outside of Japan.

The Urgent Need for a Factor Xa Inhibitor Antidote Annually, 1 to 4 percent of patients treated with Factor Xa inhibitors may experience major bleeding, and an addition percent may require emergency surgery. Commensurate with the increase in the use of Factor Xa inhibitors -- for str prevention in atrial brillation; treatment and prevention of deep vein thrombosis (DVT) and pulmonary embolism; a prevention of DVT following knee or hip replacement surgery -- the number of hospital admissions due to bleeding associated with these agents continues to grow. In large randomized trials of Factor Xa inhibitors in patients with atr brillation, the 30-day mortality rate in patients with intracranial hemorrhage (ICH) exceeded 40 percent. Based on t current adoption of all three Factor Xa inhibitors in the United States, this results in an estimated 300 deaths per mo to ICH related bleeding.

According to IMS Health, worldwide sales of oral Factor Xa inhibitors were $9.5 billion in the 12 months ending June 2 52 percent growth over the same period of last year. In the EU5, an estimated 73,000 oral Factor Xa inhibitor-treated will be hospitalized this year due to major bleeding or will require urgent surgery, with half of those patients in Germ

ANNEXA-4 Study Design ANNEXA-4 is a global, single-arm, open-label clinical trial designed to evaluate AndexXa (andexanet alfa), a U.S. Food Administration (FDA)-designated Breakthrough Therapy, in patients who present with an acute major bleed while rec , edoxaban, enoxaparin or . For ethical reasons, this multi-center, prospective cohort study is n randomized and all participants receive AndexXa given as a bolus dose over 30 minutes followed by a two-hour infus Patients receive a low or high dose depending on which Factor Xa inhibitor they have received and the time they rec Patients are evaluated for 30 days following AndexXa administration. The co-primary ecacy endpoints are the perc change in anti-Factor Xa activity at two hours and assessment of hemostasis over 12 hours following the infusion. He ecacy is assessed by an independent endpoint adjudication committee as either excellent, good or poor/none. To ANNEXA-4 has enrolled more than 150 patients with life-threatening bleeds.

About AndexXa AndexXa (andexanet alfa), an investigational drug, is a modied human Factor Xa molecule that acts as a decoy to ta sequester with high specicity both oral and injectable Factor Xa inhibitors in the blood. Once bound, the Factor Xa i are unable to bind to and inhibit native Factor Xa, thus potentially allowing for the restoration of normal hemostatic processes. AndexXa is the rst compound being studied as an antidote for Factor Xa inhibitors that directly and spec reverses anti-Factor Xa activity – the anticoagulant mechanism of these agents. The European Medicines Agency (EM completed the validation period of Portola’s Marketing Authorization Application (MAA) in August 2016 and a decisio expected in 2017.

About Portola Pharmaceuticals, Inc. Portola Pharmaceuticals is a biopharmaceutical company developing product candidates that could signicantly adv elds of thrombosis and other hematologic diseases. The Company is advancing three programs, including betrixaba oral, once-daily Factor Xa inhibitor; AndexXa™ (andexanet alfa), a recombinant protein designed to reverse the antico eect in patients treated with an oral or injectable Factor Xa inhibitor; and , a Syk/JAK inhibitor in develop http://investors.portola.com/phoenix.zhtml?c=198136&p=irol-newsroomArticle&ID=2217864 1/2 3/30/2019 Investors - News Release - Portola Pharmaceuticals, Inc.

treat hematologic cancers. Portola's partnered program is focused on developing selective Syk inhibitors for inamm conditions. For more information, visit www.portola.com and follow the Company on Twitter @Portola_Pharma.

Forward-looking Statements Statements contained in this press release regarding matters that are not historical facts are "forward-looking statem within the meaning of the Private Securities Litigation Reform Act of 1995. Because such statements are subject to ri uncertainties, actual results may dier materially from those expressed or implied by such forward-looking statemen statements include, but are not limited to, statements regarding the timing of our development eorts for andexane the projected need for a Factor Xa inhibitor antidote. Risks that contribute to the uncertain nature of the forward-loo statements include the risk that our data fail to demonstrate safety and ecacy of andexanet alfa to the satisfaction FDA or similar regulatory authorities outside the United States, such as the EMA, and the risks that we will not succes manufacture andexanet alfa on a commercial scale or be able to obtain the capital needed to fund our operations. T other risks and uncertainties are described more fully in our most recent lings with the Securities and Exchange Commission, including our most recent quarterly report on Form 10-Q, which was led on August 9, 2016. All forwar statements contained in this press release speak only as of the date on which they were made. We undertake no ob update such statements to reect events that occur or circumstances that exist after the date on which they were m

i Portola estimate based on IMS reported oral Factor Xa inhibitor sales in the EU5

Investor Contact: Ana Kapor Portola Pharmaceuticals [email protected] Media Contact: Julie Normart W2O Grou [email protected] 415.946.1087

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