Sulfonate Esters – How Real Is the Risk?

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Sulfonate Esters – How Real is the Risk? Summary of Key Findings from PQRI Studies of the Reaction Between Sulfonic acids and Alcohols A Teasdale   acids andalcohols. sulfonic from betweeninteractionimpurities resulting strong alcohols.andacids as a interactionsbetweenresult of genotoxic impurities regulatorsto inrelationthe of generationpotential This has centred primarily on sulfonate esters, esters, on sulfonatetheoreticalThis has centredprimarily by expressedconcerns Theregrowingbeen have Introduction R R'- alkyl - methyl ethyl / isopropyl / etc. R - alkyl aryl / O O S O H + – R Description of theissue ' O H R O O S O R ' + O H 2

Global Process R&D    Introduction build on these studies Clear challenge from this meeting going forward was for industry to house studies It was clear at the meeting that many companies had carried out in impurities Issue was discussed at length at the DIA meeting on genotoxic – – – – PQRI Initiativeborneoutof this need. To provideclearevidence of this understandingand topublish. Showingsome understandingof andlevelsformed howtocontrol them. counterions. FDA expressedsignificantconcerns overuse ofsulfonicacids as – November November 2005 – Description of theIssue

Global Process R&D    The ProductInstitute QualityResearch What is PQRI (www.pqri.org)? performance of drug products.” “…PQRI tackles projects to ensure the quality, safety and CDER.” scientific information that should be submitted in a regulatory filing to “The mission of PQRI is to conduct research to generate specific Evaluation and Research (CDER), Industry, and Academia.” “… (PQRI) is a collaborative process involving FDA’sCenter for Drug www.pqri.org

Global Process R&D    Study Model of data. Also required the right skillset Alsothe right required Resourcea keyfactor. also Keyverification aspectof the independent workwas – – – complex complex problems Proven track record on trace analysis and of solving Real issue for many PQRI activities. Specific challenge from FDA.

Global Process R&D    public public domain To place reputable, peer under process To understand the absolute levels of such impurities that can form decomposition of sulfonate esters, To provide a sound scientific understanding of the formation and – – – – – Aims Teaching regardprocesswithto designester obviate/minimise formation Methodologiesfor andanalyses kineticstudies Effective purgeprocesses. Optimal processconditions to minimizethe sulfonateester formation. under syntheticallyrelevantconditions. - related conditions - reviewed reviewed science . - based knowledge into the

Global Process R&D 3. 2. 1. Step 1: Experimental Protocol  Establishment ofarobust reactionstudyprotocol • • • StudyMethodology Validation of analytical methodology Establishment of actual technique Experimental Protocol Investigation / Establishment of Analytical Methodology requiredfor kineticmodelling. Definitionof the numbersofsamples andfrequency of sampling equipmentand sampling(+ derivatisation)procedures Wide dynamicrangeto required(lowseveralppm)thousand +

Global Process R&D Limit of Quantification: Limit of Detection: RSDfor EMS(asEt Precision: Linearity: KeyData: Validation Data for analytical procedure conversion. internal standard 2 (d5 >0.999). – 3 % at 5 μg level and better than 1 % at the μg 50 level. Linear over the 5 over the Linearrange 0.5μg/ml - TPFB derivative) TPFB derivative) measured relative to the - 1 μg/mL, corresponding to 0.001 % Et - TPFB) was: – 500 ug/ml EMS(R 500 2

Global Process R&D t 1 i F F m ) Derivatization PFTP upon Based Procedure Analytical S e a a m n F F p d l e t r s e a w F S t - i e t N h d d a C + w + r a H i t w h N 3 : n O O S a o O v H e O r H + ( 4 E F F i n ) t L t e O E e r n v t d w 2 H e a P F F 5 ) i l l s t F S C h s E T o H t a M s a B f 3 m m n O O S E S F S d p a C t : a l l e H P O l r s d a 2 F C C ) m s T D H p a B 2 o 3 n C i u k a a D e n l n 3 d y t d z o F F e f d d 5 d E 5 b E y t F F t P G P F C F T / T F S B M B C K. Jacq,et al Anal Biomed. C S D : H e d p t 3 H 2 i C m q e u ) e 3 D u r b s O O a S e i 3 i v l a d l i i s , a ( m b s 1 h t p r 2008 i 5 p e a z O a l a d t m e c i o t E s e i m i o n n t h p n e w a e r t counts d5Et PFTP area of Et PFTP to based uponratio valuestime vs Concentration a i h , 48(5), 1339 , t a i o t n o t h 1 r e + d d i 0 t n d ) o 5 i J.Pharm. n t t f a o h d o s s e u e r H e s r g p f a e 2 f e e C y 0 r c i o i t n d o f

Global Process R&D   Step 2: Reaction SpaceStudies Experimental Protocol salts 2 terms acidsmost of marketed in sulfoniccommon 1. Initiallystudy Ethanol 1 Commonly used – – The methyl, ethyl and isopropyl esters of Toluenesulfonic acid. The methyl, ethyl and isopropyl esters of Methanesulfonic acid Definition of Scope • Followed Followed by focused studies on other systems and 2 and – - Sulfonate Esters Methanesulfonic acid system acid Methanesulfonic alcohols in combination the combinationin alcohols

Global Process R&D     Step 2: Reaction SpaceStudies Acidity Time Temperature Presence / of absencewater 2. Scope driven bycommon conditions…process Experimental Protocol • • excesses excesses and deficiencies of added base ‘parent system’ (no added base) o Hunigs Hunigs Base & Pyridines as models for API • • • salts… protonated base is stronger acid than pharmaceutical weaker base than many pharmaceutical bases, therefore 2,6 - lutidine used, as sulfonate salts are highlysoluble

Global Process R&D Reaction mechanism mechanism Reaction     This This critical dependence proton underpins all the observedresults NB Solvolysisadditionalis asignificantmechanismconsumingester protonated alcohol Reactionthrough occursnucleophilic attack of the sulfonateaniontheon Reactions of(O – – to form the etherand regeneratesulfonicacid ester the in been found nucleophile alcohol is the the where Precludes mechanisms 18 ) labelledmethanolMSA withanalysedbywereCG – R2 O O O S 18 – labelappearsthein WATER. O - it was instead restricted entirely to waterto entirely instead restricted wasit H + R1 – Ester Formation Ester O 18 H R2 R2 O O S O O S O O - R - 1 + + - R1 H O18 label label would O18 have O 18 O H 18 + H H - MS.

Global Process R&D    in in solution All reactionscarried out ‘Mid andof rearcube’ ‘Front ofcube’  – – Initial system : Ethyl Methanesulfonate (Ethyl mesylate, EMS) Original Original Design Space systems… ‘salt understanding system… acidic (strongly) understanding the - like’ like’ 40C 70C Temp 0% Stoicheometryof addedbase: 1:1 Concentrationof acid: Water (v/v) 5% No Baseadded Lutidine >0.25M i Pr 2 NEt

Global Process R&D   Presentation of Results Conversion means Conversion form: graphicalin Resultsbe presented will – – – – – Does Not Yields Molar conversion of conversion • And hence necessary purge efficiency for salt isolation levels of ester in isolated yields of salts… give teaching on upper limits which may be formed in solution vs time sulfonate sulfonate (anion) to ester

Global Process R&D Temperature EMS Formation

 % conversion Conversion Conversion to EMS depends on temperature and time. 0.05 0.15 0.25 0.35 0.45 0.1 0.2 0.3 0.4 – 0 1M MSA1M water EtOH, in added no As oneexpect… would 0 70C 5 – Effect of Time (hr) 10 15 20

Global Process R&D EMS Formation  % conversion Conversion Conversion to EMS depends on temperature and time. 0.05 0.15 0.25 0.35 0.45 0.3 0.4 0.1 0.2 – 0 1M MSA1M EtOH, water in added no As oneexpect… would 0 40C 50C 60C 70C – 5 Effect ofTemperature Time (hr) 10 15 20

Global Process R&D    EMS Formation conversion conversion to <75ppm 25%w/w water reduces significant impact… Even 5%w/w water has reduced in presence of water Conversion to EMS is – after 15at hours 70C – Effect ofWater

% conversion % conversion 0.0025 0.0075 0.05 0.15 0.25 0.005 0.1 0.2 0.01 0 0 0 Effect of Water (1M MSA, Water of (1M Effect 70C) Effect of Water (1M MSA, Water of (1M Effect 70C) 0 66%w/w 25%w/w 5%w/w water no 5 5 Time (hr) Time (hr) 10 10 15 15 20 20

Global Process R&D  2,6 EMS Formation Excess Excess lutidine (green trace): Ester Undetectable over background… - Lutidine

% conversion 0.1 0.2 0.3 0 0 Effect of Added of Effect Base (70C) 9% excess lutidine 9% deficit 2% lutidine 1M MSA, 70degC 2 4 – Time (hr) Presence of 6 8 10 12 N

Global Process R&D Excess phosphoric acid affordedExcessacid phosphoric DETECTABLE NO EMS Acidity as aDriver of Forward Rate (lutidine:MSA:H

% conversion 0.1 0.2 0.3 0 0 Effect of Added of Effect Base (70C) 1M MSA, 70degC 2 12% excess nitroaniline 9% excess lutidine 2% deficit lutidine 3 PO 4 4 1:1:0.66) Time (hr) 6 8 10 12 Cl N N O H 2 2 Cl

Global Process R&D Other Systems

% conversion 0.3 0.4 0.1 0.2 0 0 Methyl Methanesulphonate Formation Methanesulphonate Methyl 10 20 Time (hr) 30 - Methyl Mesylate 40 50 60 40C 50C 50C 60C

Global Process R&D Other Systems  of lutidine As with EMS, no observable reaction seen inAs seen presence withreaction EMS, no observable % conversion 0.3 0.4 0.1 0.2 0 0 Methyl Methanesulphonate Formation Methanesulphonate Methyl 10 20 Time (hr) 30 – Org. Process Res. Dev. 2009, 13,429 et al,Delaney Jacq, Teasdale, Eyley, Methyl Mesylate 40 50 60 40C, 40C, 6.87%w/w water 50C, 6.62%w/w water 60C, 7.25%w/w water 40C 50C 50C 60C

Global Process R&D Solvolysis of Methyl Mesylate – –

Little influence of acid or base under these conditions Strong influence of water on sulfonate ester stability % conversion 100 10 20 30 40 50 60 70 80 90 0 0 5 0.07Molar MMS at 60C at MMS 0.07Molar Time (hr) 10 15 20 0.23M MSA, 45.66%w/w water 0.22M MSA, 23.88%w/w water 0.05M lutidine, 0.11%w/w water 0.23M MSA, 0.11%w/w water

Global Process R&D 2  - formed are higher under anhydrous conditions. anhydrousformed under are higher Profileto similarthat of EMS, of levelsalthoughIMS Propyl Mesylate Formation % conversion 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.1 0 1 0 5 1M MSA1M Propan-2-ol in Time (hr) 10 15 20 40C, 40C, 0.14%w/w water 50C, 0.14%w/w water 60C, 0.03%w/w water 70C, 0.11%w/w water

Global Process R&D 2 -  Propyl Mesylate Formation reaction seen in presence of lutidinepresence reaction seenin As mesylate,nomethyl with observableethyl and % conversion 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.1 0 1 0 5 1M MSA1M Propan-2-ol in Time (hr) 10 15 20 40C, 40C, 4.3%w/w water 50C, 4.3%w/w water 60C, 4.3%w/w water 70C, 5.6%w/w water 40C, 0.14%w/w water 50C, 0.14%w/w water 60C, 0.03% water 70C, 0.11%w/w water

Global Process R&D Ethyl Tosylate Formation NB TsOHcommercially as the available monohydrate

% conversion 0.00 0.05 0.10 0.15 0.20 0 5 1M TsOH.H2O1M Ethanol in Time (hr) 10 15 20 40C, 40C, 2.2%w/w water 50C, 2.2%w/w water 60C, 2.2%w/w water 70C, 2.2%w/w water

Global Process R&D Ethyl Tosylate Formation  

Excess 2,6 Water ester formation reduces % conversion 0.00 0.05 0.10 0.15 0.20 0 - lutidine eliminates ester formation eliminateslutidine 5 1M TsOH.H2O1M Ethanol in Time (hr) 10 15 20 40C, 40C, 11.4%w/w water 50C, 7.8% water 60C, 7.8%w/w water 70C, 8.2%w/w water 40C, 2.2%w/w water 50C, 2.2%w/w water 60C, 2.2%w/w water 70C, 2.2%w/w water

Global Process R&D Ethyl Tosylate vs Ethyl Mesylate  monohydrate NB TsOH.H2Oas the commerciallyavailable

% conversion 0.1 0.2 0.3 0.4 0.0 0 1M Sulphonic Acid Sulphonic 1M EtOH in 5 Time (hr) 10 15 20 EMS, 40C EMS, 50C EMS, 60C EMS, 70C ETS, 40C ETS, 50C ETS, 60C ETS, 70C

Global Process R&D  2 Again, no observable reaction seen in presence of lutidineinseen presence reaction Again,no observable - Propyl Esters: Tosylate vs Mesylate % conversion 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 1.1 0.0 0 5 1M pTsOH.H2O1M EtOH in Time (hr) 10 15 20 IMS, 50C IMS, 60C IMS, 70C ITS, 50C ITS, 60C ITS, 70C

Global Process R&D    sulfonate formation by ester (avoid) Minimise Learning for Process Design… procedures where possibleprocedures where steps atisolationtemperature. the practicallowest the andandsaltformation excess conduct possible to an exactstoichiometery. Include waterinthesalt formation andisolation If use theminimum an excessisneeded,of sulfonicacid Use excessanof the API base,or as near aspossible • • Competition for proton. Rapid Rapid hydrolysis rates relative to rates of ester formation.

Global Process R&D    Learning for Process Design… of cake. hold keptto times a minimum. and aspossible prepared ataslowatemperature are stored before mixedand use. If efficientIf washingensure likelyformation levellow shouldbe If then anysolutions this is unavoidable andacid alcohol whichsulfonicAvoidin situations

Global Process R&D    Viracept contaminatedwithEMS Tablets ultimatelyfoundto be smelling+ nausea patientscomplaining of tablets Roche receivedreportsof Background findings?’ doesn’t this disproveyour is A common challengeto this work – – Up to 2300ppm ‘what about‘whatViracept – In Spring2007 . –     neithernor MSA the Root causeanalysisthatshowed mediated REMEMBER Tank thenneat filledwith MSA. dryingwasperformed. ethanolno but,crucially, tank MSA holdtank cleaned with EMS contamination. could becontributors majorto the manufacturingprocess itself – – MSA. levels leading significant in to months several over EMS formed environment acidic a highly This created mechanism H +

Global Process R&D   Conclusion risk used under the right conditions without fear of such as to lowlevelspresentrisk noappreciable that to esters canlevelsof sulfonate becontrolled straight forward through the PQRI it studiesis entirely betweenacidsanddeveloped sulfonic alcohols Ultimately this shows that sulfonic acids can be of the reaction Basedunderstanding onthe thorough to control process conditions such process conditionsto control possible and

Global Process R&D     Acknowledgements FDA RIC PQRI Team PQRI – – – – – – – – – Rick Rick Lostritto David FrankKarine / Jacq (Wyeth)Simon Golec BMS) Ed Delaney(formerly Rolf Schulte Plough) Van (Schering Reif (GSK) Elder Dave Kevin / Facchine (Pfizer). Worth Taylor Karen AndrewLipcynski / (AZ) AndrewTeasdale / Steve Eyley - Oestrich (Roche) Oestrich - employed as a consultant to the project project the to consultant a as employed - Team Leader. Team

Global Process R&D Back Up Slides – For Reference

Global Process R&D of Chromatography Research Institute     RIC Project Personnel how…” “…involvedin the development andpromotionof chromatographic know RIC is based in Kortrijk, Belgium Particular skills in trace analysis – – – – Analyst:KarineJacq R&D Manager:Dr Frank David employing existingmethodologydeveloped conjunctionbyRIC inwithPfizer, Director: ProfPatSandra. HS - GC - MS after derivatisation -

Global Process R&D Liquid syringe (sample Heatedtray (40 – 70 prep) MS ° C) InstrumentDesign Dual rail system ° incubator (105 Headspace (gas only) injection syringe for Headspace C) GC

Global Process R&D % conversion 0.05 0.15 0.25 0.35 0.45 0.1 0.2 0.3 0.4 0 1M MSA1M water EtOH, in added no 0 70C Each point is aseparate experiment to build the reaction profile. 5 • Shown to provide highly robust data… Time (hr) 10 15 20 (MSA solutions) Heatedsamples before incubation) (MSA, DS IS and addedthere SHS with 2 mLvials solvent

Global Process R&D Validation Validation Data foranalytical procedure  MSA withspikedEMS in ethanol Method validation was performed using 1 of M solutions usingwas Method performed validation – – made. The results are summarized in Table 1. Using spiked solutions, a 6 level (+blank) calibration curve was into EMS). (corresponds to a 0.005 to 0.5 % (potential) conversion of MSA concentration of the EMS was in the range of 5 to 500 μg/mL.

Global Process R&D Validation Data for analytical procedure linearity data are given. EMSand d5 (column 1). Relative standard deviations (RSDs) at all levels and at 5 and 50 μg/mL, and (column 6) in function of EMS concentration spiked in reaction mixture, at room temperature and EMS derivatives (columns 4 and 5) and the relative peak area (Et The table shows the rawpeak areas for IS1 (column 2), for MMS derivative (column3), for IS2 Table 1: Validation derivatisationof - EMS were not detected. - SHS - GC - MS method MS - TPFB versus IS2)

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