EMEA基因毒性雜質(zhì)限度指南4

第頁20190628EMEA/CHMP/QWP/251344/2019基因毒性雜質(zhì)限度指南（中英文對(duì)照）London,28June2019CPMP/SWP/5199/02EMEA/CHMP/QWP/251344/2019TheEuropeanAgencyfortheEvaluationofMedicinalProducts歐洲共同體藥物評(píng)審委員會(huì)(EMEA)COMMITTEEFORMEDICINALPRODUCTSFORHUMANUSE人用藥品委員會(huì)(CHMP)GUIDLINEONTHELIMITSOFGENOTOXICIMPURITIES基因毒性雜質(zhì)限度指南DESCUSSIONINTHESAFETYWORKINGPARTY安全工作組之內(nèi)的討論June2019-October2019TRANSMISSIONTOCPMPCPMP傳遞December2019RELEASEFORCONSULTATION專家討論December2019DEADLINEFORCOMMENTS建議收集最后期限March2019DISCUSSIONINTHESAFETYWORKINGPARTYANDQUALITYWORKINGPARTY安全工作組和質(zhì)量工作組之間的討論June2019-February2019TRANSMISSIONTOCPMP轉(zhuǎn)移給CPMPMarch2019RE-RELEASEFORCONSULTATION再次放行給顧問團(tuán)June2019DEADLINEFORCOMMENTS收集意見的最后期限D(zhuǎn)ecember2019DISCUSSIONINTHESAFETYWORKINGPARTYANDQUALITYWORKINGPARTY安全工作組和質(zhì)量工作組之間的討論February2019-May2019ADOPTIONBYCHMP被CHMP采用28June2019DATEFORCOMINGINTOEFFECT生效日期01January2019KEYWORDS關(guān)鍵詞Impurities;Genotoxicity;Thresholdoftoxicologicalconcern(TTC);Structureactivityrelationship(SAR)GUIDLINEONTHELIMITSOFGENOTOXICIMPURITIES基因毒性雜質(zhì)限度指南TABLEOFCONTENTS目錄EXECUTIVESUMMARY內(nèi)容摘要31.INTRODUCTION介紹32.SCOPE范圍33.LEGALBASIS法律依據(jù)34.TOXICOLOGICALBACKGROUND毒理學(xué)背景45.RECOMMENDATIONS建議45.1GenotoxicCompoundsWithSufficientEvidenceforaThreshold-RelatedMechanism具有充分證據(jù)證明其閾值相關(guān)機(jī)理的基因毒性化合物45.2GenotoxicCompoundsWithoutSufficientEvidenceforaThreshold-RelatedMechanism不具備充分證據(jù)支持其閾值相關(guān)機(jī)理的基因毒性化合物55.2.1PharmaceuticalAssessment藥學(xué)評(píng)價(jià)55.2.2ToxicologicalAssessment毒理學(xué)評(píng)價(jià)55.2.3ApplicationofaThresholdofToxicologicalConcern毒理學(xué)擔(dān)憂閾值應(yīng)用55.3DecisionTreeforAssessmentofAcceptabilityofGenotoxicImpurities基因毒性雜質(zhì)可接受性評(píng)價(jià)決策樹7REFERENCES.參考文獻(xiàn)8EXECUTIVESUMMARY內(nèi)容摘要ThetoxicologicalassessmentofgenotoxicimpuritiesandthedeterminationofacceptablelimitsforsuchimpuritiesinactivesubstancesisadifficultissueandnotaddressedinsufficientdetailintheexistingICHQ3Xguidances.Thedatasetusuallyavailableforgenotoxicimpuritiesisquitevariableandisthemainfactorthatdictatestheprocessusedfortheassessmentofacceptablelimits.Intheabsenceofdatausuallyneededfortheapplicationofoneoftheestablishedriskassessmentmethods,i.e.datafromcarcinogenicitylong-termstudiesordataprovidingevidenceforathresholdmechanismofgenotoxicity,implementationofagenerallyapplicableapproachasdefinedbytheThresholdofToxicologicalConcern(TTC)isproposed.ATTCvalueof1.5μg/dayintakeofagenotoxicimpurityisconsideredtobeassociatedwithanacceptablerisk(excesscancerriskof<1in100,000overalifetime)formostpharmaceuticals.Fromthisthresholdvalue,apermittedlevelintheactivesubstancecanbecalculatedbasedontheexpecteddailydose.Higherlimitsmaybejustifiedundercertainconditionssuchasshort-termexposureperiods.基因毒性雜質(zhì)的毒理學(xué)評(píng)估和這些雜質(zhì)在活性藥物中的可接受標(biāo)準(zhǔn)的測(cè)定是一件困難的事情，并且在現(xiàn)有的ICHQ3X指南中也沒有詳細(xì)的規(guī)定。現(xiàn)有的關(guān)于基因毒性雜質(zhì)的相關(guān)數(shù)據(jù)是容易變化的，也是對(duì)雜質(zhì)可接受標(biāo)準(zhǔn)如何進(jìn)行評(píng)價(jià)的主要影響因素。如果缺少風(fēng)險(xiǎn)評(píng)估方法所需要的數(shù)據(jù)，比如，致癌作用的長(zhǎng)期研究數(shù)據(jù)，或?yàn)榛蚨拘缘拈y值提供證據(jù)的數(shù)據(jù)，一般建議使用一般通用的被定義為毒理學(xué)關(guān)注的閾值（TTC）的方法。一個(gè)“1.5μg/day”的TTC值，即相當(dāng)于每天攝入1.5μg的基因毒性雜質(zhì)，被認(rèn)為對(duì)于大多數(shù)藥品來說是可以接受的風(fēng)險(xiǎn)（一生中致癌的風(fēng)險(xiǎn)小于十萬分之1）。按照這個(gè)閥值，可以根據(jù)這個(gè)預(yù)期的每日攝入量計(jì)算出活性藥物中可接受的雜質(zhì)水平。較高的臨界值可以在特定的條件下，如短期暴露周期等，進(jìn)行推算。1.INTRODUCTION介紹Ageneralconceptofqualificationofimpuritiesisdescribedintheguidelinesforactivesubstances(Q3A,ImpuritiesinNewActiveSubstances)ormedicinalproducts(Q3B,ImpuritiesinNewMedicinalProducts),wherebyqualificationisdefinedastheprocessofacquiringandevaluatingdatathatestablishesthebiologicalsafetyofanindividualimpurityoragivenimpurityprothelevel(s)specified.Inthecaseofimpuritieswithagenotoxicpotential,determinationofacceptabledoselevelsisgenerallyconsideredasaparticularlycriticalissue,whichisnotspecificallycoveredbytheexistingguidelines.在原料藥（Q3A）和藥物制劑（Q3B）的雜質(zhì)指導(dǎo)原則中，雜質(zhì)限度確定的依據(jù)包括各個(gè)雜質(zhì)的生物安全性數(shù)據(jù)或雜質(zhì)在某特定含量水平的研究概況。而對(duì)于遺傳毒性雜質(zhì)限度的確定，通常都認(rèn)為是特別關(guān)鍵的問題，但目前尚無相關(guān)的指導(dǎo)原則。2.SCOPE范圍ThisGuidelinedescribesageneralframeworkandpracticalapproachesonhowtodealwithgenotoxicimpuritiesinnewactivesubstances.Italsorelatestonewapplicationsforexistingactivesubstances,whereassessmentoftherouteofsynthesis,processcontrolandimpuritypronotprovidereasonableassurancethatnoneworhigherlevelsofgenotoxicimpuritiesareintroducedascomparedtoproductscurrentlyauthorisedintheEUcontainingthesameactivesubstance.ThesamealsoappliestovariationstoexistingMarketingAuthorisationspertainingtothesynthesis.Theguidelinedoes,however,notneedtobeappliedretrospectivelytoauthorisedproductsunlessthereisaspecificcauseforconcern.本指導(dǎo)原則闡述了如何處理新原料藥中遺傳毒性雜質(zhì)的一般框架和實(shí)際方法。該指導(dǎo)原則也適用于已有原料藥的新申請(qǐng)，如果其合成路線、過程控制和雜質(zhì)研究尚無法確保不會(huì)產(chǎn)生新的或更高含量的遺傳毒性雜質(zhì)（及EU目前批準(zhǔn)的相同原料藥相比）。該指導(dǎo)原則同樣適用于已上市原料藥有關(guān)合成方面的補(bǔ)充申請(qǐng)。除非有特殊原因，本指導(dǎo)原則不適用于已上市的產(chǎn)品。Inthecurrentcontexttheclassificationofacompound(impurity)asgenotoxicingeneralmeansthattherearepositivefindingsinestablishedinvitroorinvivogenotoxicitytestswiththemainfocusonDNAreactivesubstancesthathaveapotentialfordirectDNAdamage.Isolatedinvitrofindingsmaybeassessedforinvivorelevanceinadequatefollow-uptesting.Intheabsenceofsuchinformationinvitrogenotoxicantsareusuallyconsideredaspresumptiveinvivomutagensandcarcinogens.目前對(duì)于基因毒性雜質(zhì)的分類主要是指：在以DNA反應(yīng)物質(zhì)為主要研究對(duì)象的體內(nèi)體外試驗(yàn)中，如果發(fā)現(xiàn)它們對(duì)DNA有潛在的破壞性，那可稱之為基因毒性。如果有足夠的后續(xù)試驗(yàn)，可由單獨(dú)的體外試驗(yàn)結(jié)果，對(duì)它的體內(nèi)關(guān)聯(lián)性進(jìn)行評(píng)估。在缺乏這樣的信息時(shí)，體外基因毒性物質(zhì)經(jīng)常被考慮為假定的體內(nèi)誘變劑和致癌劑。3.LEGALBASIS法規(guī)依據(jù)ThisguidelinehastobereadinconjunctionwithDirective2019/83/EC(asamended)andallrelevantCHMPGuidancedocumentswithspecialemphasison:在閱讀該指南時(shí)有必要參考“Directive2019/83/EC”以及相關(guān)的CHMP指南文件，特別是以下幾個(gè)指南：ImpuritiesTestingGuideline:ImpuritiesinNewDrugSubstances(CPMP/ICH/2737/99,ICHQ3A(R))NoteforGuidanceonImpuritiesinNewDrugProducts(CPMP/ICH/2738/99,ICHQ3B(R))NoteforGuidanceonImpurities:ResidualSolvents(CPMP/ICH/283/95)NoteforGuidanceonGenotoxicity:GuidanceonSpecificAspectsofRegulatoryGenotoxicityTestsforPharmaceuticals(CPMP/ICH/141/95,ICHS2A)NoteforGuidanceonGenotoxicity:AStandardBatteryforGenotoxicityTestingofPharmaceuticals(CPMP/ICH/174/95,ICHS2B)4.TOXICOLOGICALBACKGROUND毒理學(xué)背景Accordingtocurrentregulatorypracticeitisassumedthat(invivo)genotoxiccompoundshavethepotentialtodamageDNAatanylevelofexposureandthatsuchdamagemaylead/contributetotumourdevelopment.Thusforgenotoxiccarcinogensitisprudenttoassumethatthereisnodiscerniblethresholdandthatanylevelofexposurecarriesarisk.根據(jù)目前的研究實(shí)踐，具有（體內(nèi)）遺傳毒性的化合物在任何暴露量下都有可能對(duì)DNA產(chǎn)生損傷，而這種損傷可能會(huì)引發(fā)腫瘤。因此，對(duì)于遺傳毒性致癌物質(zhì)，應(yīng)謹(jǐn)慎認(rèn)為不存在明確的閾值，任何暴露量下都存在風(fēng)險(xiǎn)。However,theexistenceofmechanismsleadingtobiologicallymeaningfulthresholdeffectsisincreasinglyacknowledgedalsoforgenotoxicevents.Thisholdstrueinparticularforcompoundsinteractingwithnon-DNAtargetsandalsoforpotentialmutagens,whicharerapidlydetoxifiedbeforecomingintocontactwithcriticaltargets.Theregulatoryapproachtosuchchemicalscanbebasedontheidentificationofacriticalno-observed-effectlevel(NOEL)anduseofuncertaintyfactors.然而，對(duì)于一些遺傳毒性事件，其產(chǎn)生生物學(xué)意義的閾值效應(yīng)的機(jī)理正越來越為人所了解。對(duì)于非DNA靶點(diǎn)的化合物和潛在致突變劑更是如此，因?yàn)樗鼈冊(cè)诩瓣P(guān)鍵靶點(diǎn)接觸前就已經(jīng)去毒化了。對(duì)于這些化合物，研究的基礎(chǔ)可以是確定關(guān)鍵的未觀察到影響的劑量（NOEL）和采用不確定因子。EvenforcompoundswhichareabletoreactwiththeDNAmolecule,extrapolationinalinearmannerfromeffectsinhigh-dosestudiestoverylowlevel(human)exposuremaynotbejustifiedduetoseveralprotectivemechanismsoperatingeffectivelyatlowdoses.However,atpresentitisextremelydifficulttoexperimentallyprovetheexistenceofthresholdforthegenotoxicityofagivenmutagen.Thus,intheabsenceofappropriateevidencesupportingtheexistenceofathresholdforagenotoxiccompoundmakingitdifficulttodefineasafedoseitisnecessarytoadoptaconceptofalevelofexposurethatcarriesanacceptablerisk.即使對(duì)能及DNA分子發(fā)生反應(yīng)的化合物，由于低劑量時(shí)有多種有效的保護(hù)機(jī)制存在，而不能將高劑量下的影響以線性方式外推到很低的（人）暴露水平。不過，目前要用實(shí)驗(yàn)方法證明某誘變劑的遺傳毒性閾值仍然非常困難。所以，在缺乏恰當(dāng)?shù)淖C據(jù)支持遺傳毒性閾值存在的情況下，確定安全劑量很困難，因此非常有必要采用一個(gè)可接受風(fēng)險(xiǎn)的暴露水平概念。5.RECOMMENDATIONS建議AsstatedintheQ3Aguideline,actualandpotentialimpuritiesmostlikelytoariseduringsynthesis,purificationandstorageofthenewdrugsubstanceshouldbeidentified,basedonasoundscientificappraisalofthechemicalreactionsinvolvedinthesynthesis,impuritiesassociatedwithrawmaterialsthatcouldcontributetotheimpurityprothenewdrugsubstance,andpossibledegradationproducts.Thisdiscussioncanbelimitedtothoseimpuritiesthatmightreasonablybeexpectedbasedonknowledgeofthechemicalreactionsandconditionsinvolved.Guidedbyexistinggenotoxicitydataorthepresenceofstructuralalerts,potentialgenotoxicimpuritiesshouldbeidentified.Whenapotentialimpuritycontainsstructuralalerts,additionalgenotoxicitytestingoftheimpurity,typicallyinabacterialreversemutationassay,shouldbeconsidered(Doboetal.2019,Mülleretal.2019).WhileaccordingtotheQ3Aguidelinesuchstudiescanusuallybeconductedonthedrugsubstancecontainingtheimpuritytobecontrolled,studiesusingisolatedimpuritiesaremuchmoreappropriateforthispurposeandhighlyrecommended.正如Q3A指導(dǎo)原則所述，根據(jù)合理的化學(xué)反應(yīng)機(jī)理分析，在新的原料藥合成、純化和貯存過程中很有可能產(chǎn)生實(shí)際的和潛在的雜質(zhì)。依據(jù)現(xiàn)有的“可能引起遺傳毒性的結(jié)構(gòu)”數(shù)據(jù)庫(kù)，潛在的遺傳毒性雜質(zhì)應(yīng)能被確認(rèn)。如果潛在的雜質(zhì)含有可引起遺傳毒性的結(jié)構(gòu)單元，該雜質(zhì)應(yīng)考慮進(jìn)行遺傳毒性試驗(yàn)（一般是細(xì)菌回復(fù)突變?cè)囼?yàn)）（Dobo等，2019）。雖然Q3A指導(dǎo)原則認(rèn)為這些研究采用含有那些需控制雜質(zhì)的原料藥進(jìn)行是可行的，但用分離出來的雜質(zhì)進(jìn)行這些研究更恰當(dāng)，也是高度推薦的方法。Fordeterminationofacceptablelevelsofexposuretogenotoxiccarcinogensconsiderationsofpossiblemechanismsofactionandofthedose-responserelationshipareimportantcomponents.Basedontheaboveconsiderationsgenotoxicimpuritiesmaybedistinguishedintothefollowingtwoclasses:根據(jù)以上論述，遺傳毒性雜質(zhì)可以歸納成以下兩類：-Genotoxiccompoundswithsufficient(experimental)evidenceforathreshold-relatedmechanism有充分閾值相關(guān)機(jī)理證據(jù)（實(shí)驗(yàn)）的遺傳毒性化合物-Genotoxiccompoundswithoutsufficient(experimental)evidenceforathreshold-relatedmechanism無充分閾值相關(guān)機(jī)理證據(jù)（實(shí)驗(yàn)）的遺傳毒性化合物5.1GenotoxicCompoundsWithSufficientEvidenceforaThreshold-RelatedMechanism具有充分證據(jù)證明其閾值相關(guān)機(jī)理的基因毒性化合物Examplesofmechanismsofgenotoxicitythatmaybedemonstratedtoleadtonon-linearorthresholdeddose-responserelationshipsincludeinteractionwiththespindleapparatusofcelldivisionleadingtoaneuploidy,topoisomeraseinhibition,inhibitionofDNAsynthesis,overloadingofdefencemechanisms,metabolicoverloadandphysiologicalperturbations(e.g.inductionoferythropoeisis,hyper-orhypothermia).非線性或閾值明確的劑量效應(yīng)關(guān)系的遺傳毒性機(jī)理包括：及細(xì)胞分化過程中紡錘體相互作用；拓?fù)洚悩?gòu)酶抑制；DNA合成抑制；過度的防御機(jī)制；代謝過度和生理性干擾（如誘導(dǎo)紅血球生成，高體溫和低體溫）。For(classesof)compoundswithclearevidenceforathresholdedgenotoxicity,exposurelevelswhicharewithoutappreciableriskofgenotoxicitycanbeestablishedaccordingtotheprocedureasoutlinedforclass2solventsintheQ3CNoteforGuidanceonImpurities:ResidualSolvents.Thisapproachcalculatesa“PermittedDailyExposure”(PDE),whichisderivedfromtheNOEL,orthelowestobservedeffectlevel(LOEL)inthemostrelevant(animal)studyusing“uncertaintyfactors”(UF).有明確遺傳毒性閾值的化合物，不產(chǎn)生遺傳毒性風(fēng)險(xiǎn)的暴露水平可以被確定，方法可參照Q3C“雜質(zhì)指導(dǎo)原則”中二類溶劑的限度確定方法。該方法可計(jì)算“每日最大允許暴露量”（PDE），數(shù)據(jù)來源于“不確定因數(shù)”動(dòng)物研究中的NOEL（未觀察到效果的最低水平）或觀察到效果的最低水平（LOEL）。5.2GenotoxicCompoundsWithoutSufficientEvidenceforaThreshold-RelatedMechanism不具備充分證據(jù)支持其閾值相關(guān)機(jī)理的基因毒性化合物Theassessmentofacceptabilityofgenotoxicimpuritiesforwhichnothresholdmechanismsareidentifiedshouldincludebothpharmaceuticalandtoxicologicalevaluations.Ingeneral,pharmaceuticalmeasurementsshouldbeguidedbyapolicyofcontrollinglevelsto“aslowasreasonablypracticable”(ALARPprinciple),whereavoidingisnotpossible.LevelsconsideredbeingconsistentwiththeALARPprinciplefollowingpharmaceuticalassessmentshouldbeassessedforacceptabilityfromatoxicologicalpointofview(seedecisiontree&followingsections).對(duì)于此類遺傳毒性雜質(zhì)，研究應(yīng)包括藥學(xué)和毒理學(xué)評(píng)估?？傊?，如果雜質(zhì)無法避免，藥學(xué)方面的控制應(yīng)遵循“合理可行的最低限量”原則（ALARP原則）。符合ALARP原則的雜質(zhì)水平再經(jīng)毒理學(xué)方面的進(jìn)一步評(píng)估，以驗(yàn)證其合理性（見決策樹和以下章節(jié)）。5.2.1PharmaceuticalAssessment藥學(xué)評(píng)價(jià)Aspecificdiscussion–aspartoftheoveralldiscussiononimpurities(seeQ3A(R))–shouldbeprovidedintheapplicationwithregardtoimpuritieswithpotentialgenotoxicity.申請(qǐng)材料應(yīng)提供關(guān)于潛在遺傳毒性雜質(zhì)的特別討論資料（見Q3A（R））。Arationaleoftheproposedformulation/manufacturingstrategyshouldbeprovidedbasedonavailableformulationoptionsandtechnologies.Theapplicantshouldhighlight,withinthechemicalprocessandimpurityproactivesubstance,allchemicalsubstances,usedasreagentsorpresentasintermediates,orside-products,knownasgenotoxicand/orcarcinogenic(e.g.alkylatingagents).需要根據(jù)現(xiàn)在的配方選擇和技術(shù)，提供證明所選的配方/生產(chǎn)策略合理性的證據(jù)。申請(qǐng)人應(yīng)在合成工藝和雜質(zhì)研究部分重點(diǎn)指出所有的化學(xué)物質(zhì)，包括用到的試劑、中間體、副產(chǎn)物，哪些是已知遺傳毒性和/或致癌性物質(zhì)（如烷化劑）。Moregenerally,reactingsubstancesandsubstanceswhichshow“alertingstructure”intermsofgenotoxicitywhicharenotsharedwiththeactivesubstanceshouldbeconsidered(seee.g.Doboetal.2019).Potentialalternativeswhichdonotleadtogenotoxicresiduesinthefinalproduct,shouldbeusedifavailable.值得關(guān)注的是，雖然有些含有“可能引起遺傳毒性的結(jié)構(gòu)”（alertingstructure）的反應(yīng)試劑及最終活性物質(zhì)并沒有共同結(jié)構(gòu)，但也要考慮它們的遺傳毒性(seee.g.Doboetal.2019).。如果有可能，應(yīng)該對(duì)它們進(jìn)行一些替代研究，以使最終產(chǎn)品中不會(huì)引入基因毒性殘留。Ajustificationneedstobeprovidedthatnoviablealternativeexists,includingalternativeroutesofsynthesisorformulations,differentstartingmaterials.Thismightforinstanceincludecaseswherethestructure,whichisresponsibleforthegenotoxicand/orcarcinogenicpotentialisequivalenttothatneededinchemicalsynthesis(e.g.alkylationreactions).需要提供充分的論證來說明沒有可行的替代方法存在，包括可替代的合成路線或配方，不同的起始物料等。比如，應(yīng)證明具有遺傳毒性和/或致癌性的結(jié)構(gòu)在化學(xué)合成中（如烷化反應(yīng)）是必需的。Ifagenotoxicimpurityisconsideredtobeunavoidableinadrugsubstance,technicalefforts(e.g.purificationsteps)shouldbeundertakentoreducethecontentofthegenotoxicresiduesinthefinalproductincompliancewithsafetyneedsortoalevelaslowasreasonablypracticable(seesafetyassessment).Dataonchemicalstabilityofreactiveintermediates,reactants,andothercomponentsshouldbeincludedinthisassessment.如果遺傳毒性雜質(zhì)在原料中不可避免，則應(yīng)該采取適當(dāng)?shù)募夹g(shù)（如純化步驟）降低該雜質(zhì)的含量，以滿足安全性要求，或符合“合理可行的最低限量”原則（見安全評(píng)估）。藥學(xué)評(píng)估還應(yīng)包括反應(yīng)中間體、反應(yīng)物和其它組件等的化學(xué)穩(wěn)定性研究。Detectionand/orquantificationoftheseresiduesshouldbedonebystate-of-the-artanalyticaltechniques.應(yīng)該使用比較先進(jìn)的分析檢測(cè)技術(shù)來檢測(cè)和量化這些殘留的雜質(zhì)。5.2.2ToxicologicalAssessment毒理學(xué)評(píng)價(jià)Theimpossibilityofdefiningasafeexposurelevel(zeroriskconcept)forgenotoxiccarcinogenswithoutathresholdandtherealizationthatcompleteeliminationofgenotoxicimpuritiesfromdrugsubstancesisoftenunachievable,requiresimplementationofaconceptofanacceptablerisklevel,i.e.anestimateofdailyhumanexposureatandbelowwhichthereisanegligiblerisktohumanhealth.鑒于在沒有明確閾值的前提下定義安全暴露水平（零風(fēng)險(xiǎn)）是不可能的，且從原料藥中完全除去遺傳毒性雜質(zhì)經(jīng)常是很難做到的，所以有必要提出一個(gè)“可接受風(fēng)險(xiǎn)水平”（acceptablerisklevel）的概念，比如估算一個(gè)“每日最大暴露量”值，低于該暴露量時(shí)就可以忽略其對(duì)人體健康的風(fēng)險(xiǎn)。ProceduresforthederivationofacceptablerisklevelsareconsideredintheAppendix3oftheQ3CNoteforGuidanceonImpurities:ResidualSolventsforClass1solvents.However,theseapproachesrequireavailabilityofadequatedatafromlong-termcarcinogenicitystudies.對(duì)于可接受風(fēng)險(xiǎn)水平的推導(dǎo)過程請(qǐng)參見Q3C（雜質(zhì)指南注釋:一類溶液殘留）中的附件三。然而，應(yīng)用這些方法必須有足夠多的長(zhǎng)期致癌性研究數(shù)據(jù)。Inmostcasesoftoxicologicalassessmentofgenotoxicimpuritiesonlylimiteddatafrominvitrostudieswiththeimpurity(e.g.Amestest,chromosomalaberrationtest)areavailableandthusestablishedapproachestodetermineacceptableintakelevelscannotbeapplied.Calculationof“safetymultiples”frominvitrodata(e.g.Amestest)areconsideredinappropriateforjustificationofacceptablelimits.Moreover,negativecarcinogenicityandgenotoxicitydatawiththedrugsubstancecontainingtheimpurityatlowppmlevelsdonotprovidesufficientassuranceforsettingacceptablelimitsfortheimpurityduetothelackofsensitivityofthistestingapproach.Evenpotentmutagensandcarcinogensaremostlikelytoremainundetectedwhentestedaspartofthedrugsubstance,i.e.atverylowexposurelevels.Apragmaticapproachisthereforeneededwhichrecognisesthatthepresenceofverylowlevelsofgenotoxicimpuritiesisnotassociatedwithanunacceptablerisk.大多數(shù)情況下，遺傳毒性雜質(zhì)的毒理學(xué)評(píng)估只是局限于雜質(zhì)的體外研究（如Ames試驗(yàn)，染色體畸變?cè)囼?yàn)），但這些方法并不適用于確定雜質(zhì)可接受的攝入水平。也就是說，根據(jù)體外數(shù)據(jù)（如Ames試驗(yàn)）計(jì)算雜質(zhì)的“安全倍數(shù)（safetymultiples）”、進(jìn)而確定可接受的限度，是不合適的。此外，用含有較低（ppm級(jí)）雜質(zhì)水平的原料藥研究其致癌性和遺傳毒性，即使得出陰性結(jié)果也不足以確保該雜質(zhì)限度的合理性，因?yàn)檫@種試驗(yàn)方法缺少必要的靈敏度。有些具有很強(qiáng)致突變性和致癌性物質(zhì)及原料藥一起進(jìn)行試驗(yàn)時(shí)，因?yàn)樵诜浅５偷谋┞端角闆r下，很有可能因?yàn)榈陀跈z測(cè)限而無法檢出。所以，如果認(rèn)識(shí)到含量非常低的遺傳毒性雜質(zhì)不存在“不可接受的風(fēng)險(xiǎn)”（unacceptablerisk），那么可以采取實(shí)用的方法來控制該雜質(zhì)。5.2.3ApplicationofaThresholdofToxicologicalConcern毒理學(xué)相關(guān)的閾值應(yīng)用Athresholdoftoxicologicalconcern(TTC)hasbeendevelopedtodefineacommonexposurelevelforanyunstudiedchemicalthatwillnotposeariskofsignificantcarcinogenicityorothertoxiceffects(Munroetal.2019,KroesandKozianowski2019).ThisTTCvaluewasestimatedtobe1.5μg/person/day.TheTTC,originallydevelopedasa“thresholdofregulation”attheFDAforfoodcontactmaterials(Rulis1989,FDA1995)wasestablishedbasedontheanalysisof343carcinogensfromacarcinogenicpotencydatabase(Goldetal.1984)andwasrepeatedlyconfirmedbyevaluationsexpandingthedatabasetomorethan700carcinogens(Munro1990,Cheesemanetal.2019,Kroesetal.2019).Theprobabilitydistributionofcarcinogenicpotencieshasbeenusedtoderiveanestimateofadailyexposurelevel(μg/person)ofmostcarcinogenswhichwouldgiverisetolessthanaoneinamillion(1x10-6)upperboundlifetimeriskofcancer(“virtuallysafedose”).Furtheranalysisofsubsetsofhighpotencycarcinogensledtothesuggestionofa10-foldlowerTTC(0.15μg/day)forchemicalswithstructuralalertsthatraiseconcernforpotentialgenotoxicity(Kroesetal.2019).“毒理學(xué)關(guān)注的閾值”用于定義那些不會(huì)產(chǎn)生顯著致癌性或其他毒性作用、但又未明確研究的化合物的“常見暴露量”（commonexposurelevel）(Munroetal.2019,KroesandKozianowski2019)。該TTC估計(jì)值是1.5μg/人/日。TTC概念最早來源于FDA關(guān)于食品接觸材料的“規(guī)定閾值”（athresholdofregulation）（Rulis1989,FDA1995），該閾值根據(jù)對(duì)致癌能力數(shù)據(jù)庫(kù)(Goldetal.1984)中343種致癌物質(zhì)的分析結(jié)果得出。隨后該數(shù)據(jù)庫(kù)擴(kuò)大到700多個(gè)致癌性物質(zhì)(Munro1990,Cheesemanetal.2019,Kroesetal.2019)，這種分析結(jié)果不斷得到重復(fù)驗(yàn)證。通過對(duì)致癌能力的概率分布進(jìn)行評(píng)價(jià)，可以得到一個(gè)對(duì)大多數(shù)致癌物質(zhì)適用的“日常攝入水平(μg/person)”，此水平造成的一生中患癌癥的風(fēng)險(xiǎn)小于正常風(fēng)險(xiǎn)水平的上限1x10-6（真實(shí)的安全劑量）。對(duì)于含有“可能引起遺傳毒性結(jié)構(gòu)”的化合物，其TTC應(yīng)嚴(yán)格10倍（0.15μg/日）（Kroesetal.2019）。However,forapplicationofaTTCintheassessmentofacceptablelimitsofgenotoxicimpuritiesindrugsubstancesavalueof1.5μg/day,correspondingtoa10-5lifetimeriskofcancercanbejustifiedasforpharmaceuticalsabenefitexists.ItshouldberecognizedinthiscontextthatthemethodsonwhichtheTTCvalueisbased,aregenerallyconsideredveryconservativesincetheyinvolvedasimplelinearextrapolationfromthedosegivinga50%tumourincidence(TD50)toa1in106incidence,usingTD50dataforthemostsensitivespeciesandmostsensitivesite(several“worstcase”assumptions)(Munroetal.2019).然而，用TTC評(píng)估原料藥中的遺傳毒性雜質(zhì)限度，1.5μg/日（相當(dāng)于10萬分之一的患癌風(fēng)險(xiǎn)）是可以接受的。應(yīng)該承認(rèn)，基于TTC值控制遺傳毒性雜質(zhì)是非常保守的，因?yàn)檫@只是根據(jù)從產(chǎn)生50%腫瘤發(fā)生率（TD50）到百萬分之一致癌率的劑量線性推導(dǎo)得到的，而且TD50數(shù)據(jù)是用最敏感的動(dòng)物和最敏感的部位研究得到的（幾個(gè)“最壞條件”假設(shè)）（Munroetal.2019）。SomestructuralgroupswereidentifiedtobeofsuchhighpotencythatintakesevenbelowtheTTCwouldbeassociatedwithahighprobabilityofasignificantcarcinogenicrisk(Cheesemanetal.2019,Kroesetal.2019).Thisgroupofhighpotencygenotoxiccarcinogenscomprisesaflatoxin-like-,nitroso-,andazoxy-compoundsthathavetobeexcludedfromtheTTCapproach.Riskassessmentofmembersofsuchgroupsrequirescompound-specifictoxicitydata.有幾個(gè)結(jié)構(gòu)基團(tuán)被認(rèn)定為具有非常高的基因毒性，它們即使被攝入低于TTC值的量也會(huì)面臨非常高的基因毒性風(fēng)險(xiǎn)(Cheesemanetal.2019,Kroesetal.2019)。這些高致癌性物質(zhì)包括黃曲霉素類、N-亞硝基物和偶氮類化合物，不適用TTC方法。這類化合物的風(fēng)險(xiǎn)評(píng)估需采用專門的毒性數(shù)據(jù)。TheremaybereasonstodeviatefromtheTTCvaluebasedontheprogenotoxicityresults.根據(jù)基因雜質(zhì)概況，有些情況下會(huì)偏離TTC值。PositiveresultfrominvitrostudiesonlymayallowtoexemptanimpurityfromlimitationatTTCleveliflackofinvivorelevanceofthefindingsisconvincinglydemonstratedbasedonaweight-ofevidenceapproach(seeICHS2guidelines).Thisapproachwillusuallyneednegativeresultswiththeimpurityfromsomeadditionalinvitroand/orappropriateinvivotesting.假如按照證據(jù)權(quán)衡法能充分證明“結(jié)果缺乏體內(nèi)相關(guān)性”，體外試驗(yàn)的陽性結(jié)果也僅能在TTC水平上排除一個(gè)雜質(zhì)(參見ICH指南S2)。這種方法經(jīng)常需要在額外的體外試驗(yàn)和/或合理的體內(nèi)試驗(yàn)，并且得到雜質(zhì)的陰性結(jié)果。ATTCvaluehigherthan1.5μg/daymaybeacceptableundercertainconditions,e.g.short-termexposure,fortreatmentofalife-threateningcondition,whenlifeexpectancyislessthan5years,orwheretheimpurityisaknownsubstanceandhumanexposurewillbemuchgreaterfromothersources(e.g.food).Genotoxicimpuritiesthatarealsosignificantmetabolitesmaybeassessedbasedontheacceptabilityofthemetabolites.某些情況下TTC值高于1.5μg/日也是可以接受的，如短期用藥；用于治療威脅生命疾病的藥物；或人的存活期少于5年；或該雜質(zhì)是已知物質(zhì)，人體從其他途經(jīng)（如食物）獲得的暴露量遠(yuǎn)遠(yuǎn)高于藥物途經(jīng)。如果遺傳毒性雜質(zhì)本身就是重要的代謝物，那么該雜質(zhì)可以根據(jù)代謝物的可接受限度進(jìn)行控制。TheconcentrationlimitsinppmofgenotoxicimpurityindrugsubstancederivedfromtheTTCcanbecalculatedbasedontheexpecteddailydosetothepatientusingequation(1).采用下列公式，從TTC值和日服用劑量，可以計(jì)算出原料藥中的基因毒性雜質(zhì)的濃度限度。(1)Concentrationlimit(ppm)=TTC[μg/day]/dose(g/day]濃度限度（ppm）=TTC[μg/day]/劑量(g/day]TheTTCconceptshouldnotbeappliedtocarcinogenswhereadequatetoxicitydata(long-termstudies)areavailableandallowforacompound-specificriskassessment.對(duì)于有確切毒性數(shù)據(jù)（長(zhǎng)期毒性研究）的致癌性物質(zhì)不宜使用TTC概念，應(yīng)進(jìn)行特定化合物風(fēng)險(xiǎn)評(píng)估。IthastobeemphasizedthattheTTCisapragmaticriskmanagementtoolusingaprobabilisticmethodology,i.e.thereisahighprobabilitythata10-5lifetimecancerriskwillnotbeexceededifthedailyintakeofagenotoxicimpuritywithunknowncarcinogenicpotential/potencyisbelowtheTTCvalue.TheTTCconceptshouldnotbeinterpretedasprovidingabsolutecertaintyofnorisk.應(yīng)強(qiáng)調(diào)，TTC是一個(gè)實(shí)用性的風(fēng)險(xiǎn)管理方法，是按概率方法學(xué)估算的。比如按這一概念，如果某未知致癌性遺傳毒性雜質(zhì)的攝入量低于TTC值，那么就可以保證患癌風(fēng)險(xiǎn)控制在十萬分之一之內(nèi)。但TTC概念不能被理解為確保絕對(duì)無風(fēng)險(xiǎn)。5.3DecisionTreeforAssessmentofAcceptabilityofGenotoxicImpurities基因毒性可接受性評(píng)價(jià)決策樹(shadedboxes=pharmaceuticalassessment,whiteboxes=toxicologicalassessment)（陰影框=藥學(xué)評(píng)價(jià)，白框=毒理學(xué)評(píng)價(jià)）1)Impuritieswithstructuralrelationshiptohighpotencycarcinogens(seetext)aretobeexcludedfromtheTTCapproach1)結(jié)構(gòu)上及高致癌性物質(zhì)有關(guān)的雜質(zhì)（見正文）不能采用TTC法。2)Ifcarcinogenicitydataavailable:Doesintakeexceedcalculated10-5cancerlifetimerisk?2)如果有致癌性數(shù)據(jù)：攝入量超過10-5患癌風(fēng)險(xiǎn)嗎？3)Case-by-caseassessmentshouldin