基于体外数据模拟和预测体内PK

PKSimulation&Prediction

withIVIVE:

InVitroInVivoExtrapolationPharmoGo2014O

HowtoPredictPKwithGastroPlus

IVIVEapproachWhypredictpharmacokinetics?投入资金高研发周期长药物研发的成功率较低CombinedR&Dsurvivalbydevelopmentphasefor14largepharmaceuticalcompanies(Abbott,AstraZeneca,Bayer,Bristol-MyersSquibb,Boehringer-Ingelheim,EliLilly,GlaxoSmithKline,Johnson&Johnson,Merck,Novartis,Pfizer,Roche,Sanofi-AventisandSchering-Plough)MarkEBunnage.GettingpharmaceuticalR&Dbackontarget.NatureChemicalBiology.2011,7:335–339.MethodstopredictpharmacokineticsAnimalMethodsAllometricscalingInvitroMethodsIVIVEMechanisticalmodelsPBPK

InSilicoMethodsDiscoveryDevelopmentTime-consumingandcostlyendeavorPredictionHumanPKpropertiesAllometricscalingPK决定因素不同生理解剖体系代谢基因型和表型组织成分如蛋白种类直接放大，误差极大Toobtain“a”and“b”:plotthebodyweightofthespecies(atleast3species)vsparameterofinterestsuchasclearanceIVIVEvs.Allometric

scalingOldParadigm：Useinvivoanimalmodelasthepredictorofhumanbehavior(eg.allometricscaling)NewParadigmUsepredictive,relevantinvitrodatathatwillfeedthemodelforpredictinginvivobehaviorIVIVE:

体外体内转化（InVitroInVivoExtrapolation）Empiricalmethodvs.PBPK:ParametersdescribePKprofileVolumeofdistributionClearanceAbsorptionHalf-lifeBioavailabilityDosingregimen：Howoften？Dosingregimen：Howmuch？*ModifiedfromvandeWaterbeemd,H,andGifford,E.ADMETInSilicoModelling:TowardsPredictionParadise?Nat.Rev.DrugDisc.2003,2:192-204F

(notFa!)FaDPVFDp(notFa!)AbsorptionMetabolismMetabolismASCModern(FDA)DefinitionofAbsorptionWhatisFractionAbsorbed(Fa)?ACATModelBrainAdiposeMuscleSkinEachphysiologyincludesdefaultvaluesfor:pHineachcompartmentTransittimeforeachcompartmentLengths&radiiofeachcompartmentSEFsofeachcompartmentStomachvolumeBilesaltconcentrationineachcompartmentPoresizeineachcompartmentPorosity/PoreLength

ineachcompartmentHepaticbloodflowrateGutenzymeandtransporterdistributionsAbsorptiontermincompartmentnumberi:

ASFtrans,I

andASFpara,i=transcellularandparacellularabsorptionscalefactor

incompartmenti(nominalvalueissurface/volume,whichis2/Ri)Ri=radiusofcompartmenti

Ptrans,i

andPpara,i=transcellularandparacellularpermeability

incompartmenti*

Vlum,i=volumeoflumenforcompartmenti

C(t)lum,i=lumenconcentrationincompartmenti

C(t)entU,i

=unboundenterocyteconcentrationincompartmenti

C(t)pvU

=unboundportalveinconcentration

AbsorptionKa’Mdiss(i)RiLiAbsorptionscalefactors(ASF)accountforchangesinabsorptionduetoregionaldifferencesinradius,ionization,tightjunctiongap,andcarrier-mediatedtransport.Threeprimarypropertiesofadrug/dosageformcanlimitabsorptioninthegastrointestinaltract:SolubilityDissolutionrateIntestinalpermeabilityGastroPlus™simulation：Inputdatarequiredwouldbepreformulationinformation(solubility,permeability,pKa·····)Structure-propertypredictions(fromADMETPredictor™)provideestimatesfor:pKa,logP,solubility,permeability,etc.AccuratephysiologicalsituationsaretakenintoconsiderationSolubility,Dissolution,andPermeabilityTotalamountdissolvedTotalamountabsorbedTotalamountintosystemiccirculation(bioavailability)TotalamountintoportalveinAbsorptionStructure-propertypredictions(fromADMETPredictor™)provideestimatesfor: pKa,logP,solubility,permeability,plasmaproteinbinding,etc.Kp’sestimatedfromlogPorlogDandtissuepropertiesActivitylogPpKaSolubilityatreferencepHHumanjejunalpermeabilityVolumeofdistributionPlasmaproteinbinding,fupToxicities...etc.QSPRDistribution：KpPartitioningintotissues：Kpbindinglipidpartitioningtransportother??DistributionSteadystatevolumeofdistributionisestimatedusingthetissuevolumesandtissue:plasma

partitioncoefficientsaccordingtoPoulin:

whereVpisvolumeofplasma,Veiserythrocytevolume,E:Piserythrocytetoplasmaconcenctrationratio(calculatedfromblood/plasmaconcentrationratioandhematocrit),Vtistissuevolume,Kptisthetissue:plasmapartitioncoefficient,andERtistheextractionratioforagiventissue.Where,

Clearance

InGastroPlus,thetotalclearance,CL,isthesumofclearancefromeveryeliminatingorgan;Butmainlyhepatic(CLH),renal(CLR),andbiliary(CLB):

Step1.Invitroincubationofdrugwithmicrosomes/hepatocytes/liverslicestoobtainenzymekineticconstantsVmaxandKmandtheinvitrointrinsicclearanceStep2.Scaleinvitroenzymekineticconstantstoinvivoconditionsbasedonspecies-specificphysiologicalscalefactors.CLint

invitroCLint(wholeorgan)invivoCLh(wholeorgan)invivoStep3.Basedonahepaticbloodflowmodel(e.g.Venousequilibriummodel),determineinvivohepaticclearance.Rateofdrugelimination=CLh×ConcentrationClearance：hepaticLiverMetabolismRate=CLh*CliverCLh=Eh*Qh*RBEh=CLinth*fu,plasma/[CLinth*fu,plasma+Qh*RB]whereCLinth=ΣVmax(j)*Cu,hepat/(Km(j)+Cu,hepat)

Eh=totalhepaticextraction Qh=hepaticbloodflowrate RB=blood-to-plasmaconcentrationratio CLinth=totalhepaticintrinsicclearance Vmax(j)=maximummetabolicrateforenzymej

Km(j)=Michaelis-Mentenconstantforenzymej Cu,hepat=unboundconcentrationinhepatocytesClearance：hepaticGMR(i)=GEDF(j,i)*Vmax(j)*Cu,ent(i)/(Km(j)+Cu,ent(i)) GMR(i)=gutmetabolismrateincompartmenti GEDF(j,i)=gutenzymedistributionfactorforenzymejinenterocytecompartmentirelativetoamountinwholeliver Vmax(j)=maximummetabolicrateforenzymejinwhole

liver Km(j)=Michaelis-Mentenconstantforenzymej Cu,ent(i)=unbounddrugconcentrationinenterocyte compartmenti

Clearance：GUTPredictmetabolicclearanceinvivofrominvitromeasurements(microsomes,hepatocytes,recombinantsystems)ConvertVmaxmeasuredinrateofmetabolismper‘unitamountofenzyme’torateofmetabolismintheentiretissue(liver,gut,etc.)invitro‘unitamountofenzyme’isgivenbytheinvitroassay:

mgofmicrosomalprotein(microsomalassay)1millioncells(hepatocyteassay)pmolofenzyme(recombinantenzymes)IVIVEToobtaininvivo

Vmaxintheentiretissue:microsomeshepatocytesrCYPMetabolicrateisnotsimplyafunctionoftheCYPenzyme,theenvironmentplaysasignificantrole(concentrationsofaccessoryproteins,lipidenvironment,etc.)MicrosomesandhepatocytesareextractedfromgiventissuesotheassumptionisthattheenvironmentissimilartothatinvivoRecombinantenzymesarehumanenzymesexpressedindifferentbiologicalsystems(bacteria,yeasts,etc.)andactivityoftheenzymemaydifferfromtheactivityofthesameenzymeinvivo.Onemethodforscalingoftheactivitieshasbeenproposed:ISEFIVIVEProctorNJ,Xenobiotica2004,34:151-178DeterminedfrommetabolicratesofastandardsubstrateinrCYPandinvivosystem(HLM)Standardsubstrateisacompoundmetabolizedonly(orpredominantly)bygivenenzymeISEFwillvarybetweensystemsandbetweenlabs–needstobedeterminedforeachspecificlabsetup(synthesisofrecombinantenzymes)RequiresabundanceofgivenenzymeintheinvivosystemusedtodeterminetheISEFIVIVERelationshipbetweenCLintandt1/2

Numberofdifferentapproachesforinvitro-invivoextrapolationoftransportereffectswerepublishedoverpastfewyears.Generalconsensusbetweenpublishedapproachesisthattheextrapolationrequiresadditionalempiricalscalingfactor.Commonfeatureofthepublishedapproachesisthefocusonthetransportereffectingutand/orliver.Theydonotconsiderhowthelowpassivepermeabilitymayaffectthedistributiontoothertissuesandsubsequentlyplasmaconcentration.Wearesuggestingtoaccountforpermeabilitylimitationinalltissuesandintroductionof“SpecificPStc”parameter(PStcpermLofcellvolume)makesthisextrapolationeasyandstraightforward.ThemethodrequiresestimateofpassivediffusionratefrominvitroassayalongwithestimatesfortransporterKmandVmaxvalues.TransporterIVIVEDatalistanyinvitrodatathatisavailable:dissolution/releaseprofiles@pH;metabolismdata(KmandVmaxinHLM,hepatocytes,rCYP);etc.listinvivodatathatisavailable:Cp-timeprofiles–specifyspecies,dose(ordoserangeofmultipleprofilesavailable),dosageform(ivorpo),averageorindividual(#ofsubjects),etc生物药剂学性质(logP，pKa，溶解度，通透性，Fup，Rbp等)由化学结构预测(ADMETPredictorTM)体外实验或文献数据建立相应种属的ACATandPBPK模型录入清除率数据体外代谢实验(微粒体、肝细胞或重组酶)由动物静注数据外推(异速放大等)模拟并验证(动物数据)外推至其它动物或人体PK模型的建立和预测PredictingPKWhatisGastroPlus?GastroPlusin

Pre-Clinical&Clinical药物的发现临床前研究临床研究ParrottN,

LaveT.(2008),

MolPharm.5(5):760-775.

(IF:4.565)预测药物的吸收探讨限制吸收的因素候选药物筛选指导剂型的开发动物毒理学的研究指导决策人体研究食物效应设定制剂的释放体内外相关性群体体内过程研究预测人体的PK行为制定临床给药方案吸收模型ACAT模型()(肝肠循环)肾、胆汁排泄胆囊肝代谢随粪排出肠代谢脑肾肺心骨髓肝脾处置模型(经典房室模型或PBPK模型)OurSolutionsCATModel(1996)AmidonLawrenceXYu模型中大多数参数代表生物体及药物的自身特性，不受药时数据影响可模拟或预测药物在某器官或组织内的转运过程，以及种属间外推考虑机体解剖学、生理学、生物化学及药物理化的性质PhysiologicallyBasedPharmacokineticModel(PBPK)OurSolutions含“PBPK”的文章

整合多种体外信息，体内真实的动态行为解释体内行为的机制指导药物的研发权威的吸收模型(ACAT模型)准确的生理药代动力学模型(PBPK模型)FDA、CFDA、EMA、日本厚生省、TOP50制药企业最受欢迎的PBPK/PD模拟软件，被誉为同类软件的“黄金标准”。GastroPlusOverviewWhoareusing

SimulationsPlusproducts?仿制药注册司（OfficeofGenericDrugs）食品安全与营养中心（CenterforFoodSafetyandAppliedNutrition）

兽药中心（CenterforVeterinaryMedicine）2013年，临床药理部（OCP)：研究群体变化（健康者与病人同时开展），药物药物相互作用（DDI)等方面WhyGastroPlus?WhyGastroPlus?Hosea,N.(2009),AAPSAnnualMeetingandExposition,LosAngeles,CA,USA.十二指肠空肠回肠结肠案例：GastroPlus模拟以豁免FDA要求增加的额外临床试验FDA怀疑可能存在DDI，要求Pfizer增加临床试验测定药物在人肠中的浓度Pfizer用GastroPlus模拟药物在人体各个肠段浓度验证：FDA用GastroPlus建模，用pfizer提交的data搭建模型，FDA认可模拟结果，不再要求辉瑞增加临床试验Ki预测结果：肠浓度远低于Ki值无DDI的危险WhyGastroPlus?GastroPlus最准确预测了药物iv.和po.后人体的药代动力学过程！ColeS.,et.al.(2008),ISSXAnnualConference,Shanghai,PRC.JonesHM.,et.al.(2011),ClinPharmacokinet.50(5):331-347.(IF:4.56)现在，pfizer所有化合物的首次人体(First-In-Human)PK预测均用GastroPlus完成!WhyGastroPlus?GastroPlususedinregulatorysubmissionsClientshavesubmittedseveralGastroPluss