stressing

92JournalofValidationtechnology[SPring2012]

[Formoreauthor

information,

goto

/bios

ScientificConsiderationsof

ForceddegradationStudiesin

aNdaSubmissions

aBStraCt

awell-designedstressstudycanprovideinsightinchoos-

ingtheappropriateformulationforapropodproduct

canpreventre-developmentorre-validationofastabil-

peroutlines

thescientificaspectsofforceddegradationstudiesthat

shouldbeconsideredinrelationtoaNdasubmissions.

iNtroduCtioN

Forceddegradationissynonymouswithstresstest-

efuldegra-

dationcanbeaufultooltopredictthestabilityof

adrugsubstanceoradrugproductwitheffectson

purity,potency,perativetoknow

theimpurityprofileandbehaviorofadrugsubstance

degradation

alsoplaysanimportantroleinthedevelopmentof

analyticalmethods,ttingspecifications,anddesign

offormulationsunderthequality-by-design(Qbd)

ureofthestresstestingdependson

theindividualdrugsubstanceandthetypeofdrug

product(e.g.,solidoraldosage,lyophilizedpowders,

andliquidformulations)involved(1).

theinternationalConferenceonHarmonisation

(iCH)Q1Bguidelineprovidesguidanceforperform-

ingphotostabilitystresstesting;however,thereareno

additionalstressstudyrecommendationsintheiCHsta-

bilityorvalidationguidelines(2).thereisalsolimited

informationonthedetailsaboutthestudyofoxidation

gsubstancemonographsof

analyticalProfilesofdrugSubstancesandexcipients

providesomeinformationwithrespecttodifferent

stressconditionsofvariousdrugsubstances(3).

theforceddegradationinformationprovidedinthe

abbreviatednewdrugapplication(aNda)submissions

isoftenincompleteandinthocasdeficienciesare

viewofcommondeficienciescitedthrough-

outthechemistry,manufacturing,andcontrols(CMC)

ctionoftheaNdashasbeenpublished(4-6).Some

examplesofcommonlyciteddeficienciesrelatedtoforced

degradationstudiesincludethefollowing:

•yourdrugsubstancedoesnotshowanydegrada-

repeatstressstudiestoobtainadequatedegra-

adationisnotachievable,plea

provideyourrationale.

•Pleanotethattheconditionmployedfor

stressstudyaretooharshandthatmostofyour

repeatyour

stressstudiesusingmilderconditionsorshorter

exposuretimetogeneraterelevantdegradation

products.

•itisnotedthatyouhaveanalyzedyourstresd

samplesaspertheassaymethodconditions.

Fortherelatedsubstancesmethodtobesta-

bilityindicating,thestresdsamplesshould

beanalyzedusingrelatedsubstancesmethod

conditions.

•Pleastatetheattemptsyouhavemadeto

ensurethatalltheimpuritiesincludingthe

degradationproductsoftheunstresdandthe

stresdsamplesarecapturedbyyouranalyti-

calmethod.

ragineMaheswaran

aBouttHeautHor

ragineMaheswaran,Ph.d.,isaCMCreviewerattheofficeofgenericdrugswithintheofficeof

PharmaceuticalScience,undertheuSFoodanddrugadministration’sCenterfordrugevaluationand

aran@.

rnalofValidationtechnology[SPring2012]93

•Pleaprovidealistsummarizingtheamount

ofdegradationproducts(knownandunknown)

inyourstresdsamples.

•Pleaverifythepeakheightrequirementof

yoursoftwareforthepeakpuritydetermination.

•Pleaexplainthemassimbalanceofthestresd

samples.

•Pleaidentifythedegradationproductsthat

areformedduetodrug-excipientinteractions.

•yourphotostabilitystudyshowsthatthedrug

explain

howthisisreflectedintheanalyticalmethod,

manufacturingprocess,producthandling,etc.

inanattempttominimizedeficienciesintheaNda

submissions,somegeneralrecommendationstoconduct

forceddegradationstudies,toreportrelevantinformation

inthesubmission,andtoutilizetheknowledgeofforced

degradationindevelopingstabilityindicatinganalytical

methods,manufacturingprocess,producthandling,and

storageareprovidedinthisarticle.

StreSSCoNditioNS

typicalstresstestsincludefourmaindegradationmecha-

nisms:heat,hydrolytic,oxidative,andphotolyticdegrada-

ingsuitablereagentssuchastheconcentration

ofacid,ba,oroxidizingagentandvaryingtheconditions

(e.g.,temperature)andlengthofexposurecanachievethe

-stressingasample

mayleadtotheformationofcondarydegradantsthat

wouldnotbeeninformalshelf-lifestabilitystudiesand

under-stressingmaynotrvethepurpoofstresstest-

ore,itisnecessarytocontrolthedegradation

icapproachforstresstestinghas

beenpropodtoachievepurpofuldegradationthat

ispredictiveoflong-termandacceleratedstoragecondi-

tions(7).thegenerallyrecommendeddegradationvaries

between5-20%degradation(7-10).thisrangecoversthe

generallypermissible10%degradationforsmallmolecule

pharmaceuticaldrugproducts,forwhichthestabilitylimit

is90%-110%ghtherearerefer-

encesintheliteraturethatmentionawiderrecommended

range(e.g.,10-30%),themoreextremestressconditions

oftenprovidedatathatareconfoundedwithcondary

degradationproducts.

Photostability

Photostabilitytestingshouldbeanintegralpartofstress

testing,

recommendedconditionsforphotostabilitytestingare

describediniCHQ1BPhotostabilitytestingofNewdrug

SubstancesandProducts(2).Samplesofdrugsubstance,

andsolid/liquiddrugproduct,shouldbeexpodtoa

minimumof1.2millionluxhoursand200watthours

esamplesshouldbe

mizethe

effectoftemperaturechangesduringexposure,tempera-

ht-expodsamples

shouldbeanalyzedforanychangesinphysicalproper-

tiessuchasappearance,clarity,colorofsolution,andfor

isiontreeoutlinedinthe

iCHQ1Bcanbeudtodeterminethephotostability

ductlabel-

alsoimportanttonotethatthelabelingforgenericdrug

productsshouldbeconcordantwiththatofthereference

listeddrug(rld)andwithunitedStatesPharmacopeia

(uSP)monographrecommendations,asapplicable.

Heat

thermalstresstesting(e.g.,dryheatandwetheat)should

bemorestrenuousthanrecommendediCHQ1aaccel-

sofsolid-statedrug

substancesanddrugproductsshouldbeexpodto

dryandwetheat,whereasliquiddrugproductscanbe

commendedthattheeffectof

temperaturebestudiedin10ºCincrementsabovethat

forroutineacceleratedtesting,andhumidityat75%rela-

tivehumidityorgreater(1).Studiesmaybeconductedat

highertemperaturesforashorterperiod(10).testingat

multipletimepointscouldprovideinformationonthe

rateofdegradationandprimaryandcondarydegrada-

ventthatthestressconditionspro-

ducelittleornodegradationduetothestabilityofadrug

molecule,oneshouldensurethatthestressappliedisin

excessoftheenergyappliedbyacceleratedconditions

(40ºfor6months)beforeterminatingthestressstudy.

acidandBaHydrolysis

acidandbahydrolyticstresstestingcanbecarried

outfordrugsubstancesanddrugproductsinsolution

lectionofthetypeandconcentrationsofanacidor

abadependsonthestabilityofthedrugsubstance.

astrategyforgeneratingrelevantstresdsamplesfor

hydrolysisisstatedassubjectingthedrugsubstance

solutiontovariouspHs(e.g.,2,7,10-12)atroomtem-

peraturefortwoweeksoruptoamaximumof15%

degradation(7).Hydrochloricacidorsulfuricacid(0.1

Mto1M)foracidhydrolysisandsodiumhydroxideor

potassiumhydroxide(0.1Mto1M)forbahydrolysis

aresuggestedassuitablereagentsforhydrolysis(10).

Forlipophilicdrugs,inertco-solventsmaybeudto

94JournalofValidationtechnology[SPring2012]

ionshouldbegiven

tothefunctionalgroupsprentinthedrugmolecule

nowledgeofacom-

poundcanbeufulinlectingthestressconditions.

Forinstance,ifacompoundcontainsterfunctionality

andisverylabiletobahydrolysis,lowconcentrations

isofsamplesatvarious

intervalscanprovideinformationontheprogressof

degradationandhelptodistinguishprimarydegradants

fromcondarydegradants.

oxidation

ghhydro-

genperoxideisudpredominantlybecauitmimics

possibleprenceofperoxidesinexcipients,otheroxi-

dizingagentssuchasmetalions,oxygen,andradical

initiators(e.g.,azobisisobutyronitrile,aiBN)canalsobe

ionofanoxidizingagent,itsconcentration,

ons

ofdrugsubstancesandsolid/liquiddrugproductscan

portedthat

subjectingthesolutionsto0.1%-3%hydrogenperoxide

atneutralpHandroomtemperatureforvendaysor

uptoamaximum20%degradationcouldpotentially

generaterelevantdegradationproducts(10).Samplescan

beanalyzedatdifferenttimeintervalstodeterminethe

desiredlevelofdegradation.

differentstressconditionsmaygeneratethesameor

eandextentofdegradation

dependonthefunctionalgroupsofthedrugmolecule

andthestressconditions.

aNalySiSMetHod

thepreferredmethodofanalysisforastabilityindicating

assayisrever-phahigh-performanceliquidchroma-

tography(HPlC).rever-phaHPlCispreferredfor

veralreasons,suchasitscompatibilitywithaqueous

andorganicsolutions,highprecision,nsitivity,and

tionofpeaks

canbecarriedoutbylectingappropriatecolumntype,

columntemperature,andmakingadjustmenttomobile

-retained,highlypolarimpuritiesshould

ofmethod

development,agradientelutionmethodwithvarying

mobilephacomposition(veryloworganiccomposi-

tiontohighorganiccomposition)maybecarriedoutto

captureearlyelutinghighlypolarcompoundsandhighly

edsamplescanalso

bescreenedwiththegradientmethodtoassspoten-

solventandmobilepha

shouldbelectedtoaffordcompatibilitywiththedrug

substance,potentialimpurities,

samplepreparationshouldmimicthesamplepreparation

outlinedintheanalyticalprocedureasclolyaspossible.

Neutralizationordilutionofsamplesmaybenecessary

tographic

profilesofstresdsamplesshouldbecomparedtotho

ofrelevantblanks(containingnoactive)andunstresd

nk

unt

ofimpurities(knownandunknown)obtainedunder

eachstressconditionshouldbeprovidedalongwiththe

chromatograms(fullscaleandexpandedscaleshow-

ingallthepeaks)ofblanks,unstresd,andstresd

onally,chiraldrugsshouldbeanalyzed

withchiralmethodstoestablishstereochemicalpurity

andstability(11,12).

theanalyticalmethodofchoiceshouldbensitive

enoughtodetectimpuritiesatlowlevels(i.e.,0.05%ofthe

analyteofinterestorlower),andthepeakresponsshould

fallwithintherangeofdetector’lytical

methodshouldbecapableofcapturingalltheimpurities

formedduringaformalstabilitystudyatorbelowiCH

thresholdlimits(13,14).degradationproductidentifica-

tionandcharacterizationaretobeperformedbadonfor-

malstabilityresultsinaccordancewithiCHrequirements.

Conventionalmethods(e.g.,columnchromatography)

orhyphenatedtechniques(e.g.,lC-MS,lC-NMr)can

beudintheidentificationandcharacterizationofthe

hetechniquescanprovide

betterinsightintothestructureoftheimpuritiesthatcould

addtotheknowledgespaceofpotentialstructuralalerts

forgenotoxicityandthecontrolofsuchimpuritieswith

tighterlimits(12-17).itshouldbenotedthatstructural

characterizationofdegradationproductsisnecessaryfor

thoimpuritiesthatareformedduringformalshelf-life

stabilitystudiesandareabovethequalificationthreshold

limit(13).

variousdetectiontypescanbeudtoanalyzestresd

ec-

torshouldcontain3ddatacapabilitiessuchasdiode

arraydetectorsormassspectrometerstobeabletodetect

rraydetectionalso

offersthepossibilityofcheckingpeakprofileformultiple

itationofdiodearrayariswhen

theuvprofilesaresimilarforanalytepeakandimpurity

ordegradantpeakandthenoilevelofthesystemis

hightomasktheco-elutingimpuritiesordegradants.

Compoundsofsimilarmolecularweightsandfunctional

groupssuchasdiastereoisomersmayexhibitsimilaruv

cas,attemptsmustbemadetomodify

thechromatographicparameterstoachievenecessary

rnalofValidationtechnology[SPring2012]95

malwavelengthshouldbelected

todetectandquantitateallthepotentialimpuritiesand

orethanonewavelengthmaybe

necessary,ifthereisnooverlapintheuvprofileofan

ble

toolinmethoddevelopmentistheoverlayofparation

signalsatdifferentwavelengthstodiscoverdissimilarities

inpeakprofiles.

PeakPurityanalysis

Peakpurityisudasanaidinstabilityindicatingmeth-

ctraluniquenessofacompound

isudtoestablishpeakpuritywhenco-elutingcom-

poundsareprent.

Peakpurityorpeakhomogeneityofthepeaksof

interestofunstresdandstresdsamplesshouldbe

establishedusingspectralinformationfromadiode

strumentsoftwareisudfor

thedeterminationofspectralpurityofapeak,relevant

parametersshouldbetupinaccordancewiththeman-

ufacturer’ionshouldbegiventothe

peakheightrequirementforestablishingspectralpurity.

uvdetectionbecomesnonlinearathigherabsorbance

oldsshouldbetsuchthatco-eluting

mlocationofreference

lityofthesoft-

waretoautomaticallycorrectspectraforcontinuously

changingsolventbackgroundingradientparations

shouldbeascertained.

establishingpeakpurityisnotanabsoluteproofthat

thepeakispureandthatthereisnoco-elutionwiththe

tionstopeakpurityariwhen

co-elutingpeaksarespectrallysimilar,orbelowthedetec-

tionlimit,orapeakhasnochromophore,orwhenthey

arenotresolvedatall.

MassBalance

Massbalanceestablishesadequacyofastabilityindicat-

ingmethodthoughitisnotachievableinallcircum-

rformedbyaddingtheassayvalueand

theamountsofimpuritiesanddegradantstoevaluate

theclonessto100%oftheinitialvalue(unstresd

assayvalue)withdueconsiderationofthemarginof

analyticalerror(1).

Someattemptshouldbemadetoestablishamass

balanceshould

beexploredandanexplanationshouldbeprovided.

varyingresponsofanalyteandimpuritypeaksdueto

differencesinuvabsorptionshouldalsobeexamined

iallossofvolatile

impurities,formationofnon-uvabsorbingcompounds,

formationofearlyeluants,andpotentialretentionof

ate

detectiontechniquessuchasrilC/MSmaybeemployed

toaccountfornon-uvabsorbingdegradants.

terMiNatioNoFStudy

Stresstestingcouldbeterminatedafterensuringadequate

lactivationenergy

ofdrugsubstancemoleculesvariesfrom12-24kcal/mol

(18).acompoundmaynotnecessarilydegradeunder

everysinglestresscondition,andgeneralguidelineon

exposurelimitiscitedinareviewarticle(10).incir-

cumstanceswheresomestabledrugsdonotshowany

degradationunderanyofthestressconditions,specificity

ofananalyticalmethodcanbeestablishedbyspiking

thedrugsubstanceorplacebowithknownimpurities

andestablishingadequateparation.

otHerCoNSideratioNS

Stresstestingmaynotbenecessaryfordrugsubstances

anddrugproductsthathavepharmacopeialmethods

andareudwithinthelimitationsoutlinedinuSP

<621>.inthecawhereagenericdrugproductus

adifferentpolymorphicformfromtherld,thedrug

substanceshouldbesubjectedtostresstestingtoevaluate

thephysiochemicalchangesofthepolymorphicform

becaudifferentpolymorphicformsmayexhibitdif-

ferentstabilitycharacteristics.

ForCeddegradatioN

iNQBdParadigM

asystematicprocessofmanufacturingqualitydrugprod-

uctsthatmeetthepredefinedtargetsforthecriticalquality

attributes(CQa)necessitatestheuofknowledgeobtained

inforceddegradationstudies.

awell-designed,forceddegradationstudyisindis-

pensableforanalyticalmethoddevelopmentinaQbd

stoestablishthespecificityofastability

indicatingmethodandtopredictpotentialdegradation

productsthatcouldformduringformalstabilitystudies.

incorporatingallpotentialimpuritiesintheanalytical

methodandestablishingthepeakpurityofthepeaksof

interesthelpstoavoidunnecessarymethodre-development

andrevalidation.

Knowledgeofchemicalbehaviorofdrugsubstances

undervariousstressconditionscanalsoprovideuful

informationregardingthelectionofexcipientsforformu-

entcompatibilityisanintegral

partofunderstandingpotentialformulationinteractions

duringproductdevelopmentandisakeypartofproduct

ationproductsduetodrug-excipi-

96JournalofValidationtechnology[SPring2012]

entinteractionordrug-druginteractionincombina-

tionproductscanbeexaminedbystressingsamplesof

drugsubstance,drugproduct,andplaceboparately

ation

obtainedregardingdrug-relatedpeaksandnon-drug-

relatedpeakscanbeudinthelectionanddevel-

tance,if

adrugsubstanceislabiletooxidation,additionofan

antioxidantmaybeconsideredfortheformulation.

Fordrugsubstancesthatarelabiletoacidorundergo

stereochemicalconversioninacidicmedium,delayed-

/ba

hydrolysistestingcanalsoprovideufulinsightin

theformulationofdrugproductsthatareliquidsor

suspensions.

Knowledgegainedinforceddegradationstudiescan

facilitateimprovementsinthemanufacturingprocess.

ifaphotostabilitystudyshowsadrugsubstanceto

bephotolabile,cautionshouldbetakenduringthe

informationregardingprocessdevelopment(e.g.,wet

versusdryprocessing,temperaturelection)canbe

obtainedfromthermalstresstestingofdrugsubstance

anddrugproduct.

additionally,increadscientificunderstandingof

degradationproductsandmechanismsmayhelpto

determinethefactorsthatcouldcontributetostability

failuressuchasambienttemperature,humidity,and

riatelectionofpackagingmaterials

canbemadetoprotectagainstsuchfactors.

CoNCluSioN

anappropriately-designedstressstudymesheswell

withtheQbdapproachescurrentlybeingpromoted

-designedstress

studycanprovideinsightinchoosingtheappropriate

formulationforapropodproductpriortointen-

ugh

knowledgeofdegradation,includingmechanistic

understandingofpotentialdegradationpathways,is

thebasisofaQbdapproachforanalyticalmethod

developmentandiscrucialinttingacceptance

testingcan

provideufulinsightintothelectionofphysical

form,stereochemicalstabilityofadrugsubstance,

packaging,portant

toperformstresstestingforgenericdrugsdueto

allowablequalitativeandquantitativedifferences

informulationwithrespecttotherld,lectionof

manufacturingprocess,processingparameters,and

packagingmaterials.

reFereNCeS

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riaforNewdrugSubstancesandNewdrugProducts:Chemical

Substances,geneva,october1999.

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october2006.

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2006.

,guidanceforindustryaNdas:impuritiesindrugSub-

stances(draft),rockville,Md,august2005.

,guidanceforindustryaNdas:impuritiesindrugProducts

(draft),rockville,Md,November2010.

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mitteeforMedicalProductsforHumanu(CHMP)(

eMea/CHMP/QwP/251344/2006),Jan.1,2007.

tal.,ChemicalStabilityofPharmaceuticals,

wileyandSons,Newyork,Newyork,2nded.,1986)p.19.

Jvt

aCKNowledgMeNtSaNddiSClaiMer

theauthorwouldliketothankBobir,Naiqiya,dave

Skanchy,Bingwu,andashleyJungfortheirscientific

inputandsupport.

disclaimer:theviewsandopinionsinthisarticle

areonlythooftheauthoranddonotnecessarily

reflecttheviewsorpoliciesoftheuSFoodanddrug

administration.