Weight-BasedDosingBestforNewHCVDrugWhengivenindosesbasedonweight,aninvestigationalprodrugofribavirinhadefficacycomparabletoribavirininchronichepatitisCbutwithlesshemolyticanemia,researchersreported.InaphaseIIbtrial,thedrug--taribavirin--yieldedearlyresponseratesthatwerestatisticallyidenticalwiththoseachievedwithribavirinwhenbothdrugsweregivenwithpegylatedinterferonalfa-2b,accordingtoFredPoordad,MD,ofCedars-SinaiMedicalCenterinLosAngeles,andcolleagues.Atthesametime,twoofthetesteddosesofthedrugcausedsignificantlylessanemia(atP<0.05)thanribavirin,theyreportedonlineinHepatology.Taribavirin,formerlyknownasviramidine,isanucleosideanalogueandoralprodrugofribavirinthatisconvertedtoribavirininthebody.Butitsstructuraldifferencefromtheolderdrugmeansthatitislesslikelytoenteranddamageredbloodcells,theresearchersnoted.Indeed,inearlierstudiesusingafixeddoseoftaribavirin,thatbenefitwasdemonstrated,butefficacywasinferiortothatofribavirin,theysaid.Analysissuggestedthatthefixed-doseapproach,aswellasselectionofinadequatedoses,wasresponsibleforthelackofefficacy.Toclarifytheissue,Poordadandcolleaguestestedthreedosesoftaribavirin--20,25,or30mgperkilogramaday--againstribavirinat800to1,400mgadayin278treatment-naivepatientswithgenotype1hepatitisC.Theprimaryefficacyendpointwasearlyvirologicresponse,definedastheproportionofpatientswithatleastatwo-logdecreasefrombaselineinserumhepatitisCRNAlevelsaftertwoweeksoftherapy.Theresearchersalsolookedatsustainedvirologicresponseafter48weeksoftherapy.Themainsafetyendpointwastheproportionofpatientswithhemoglobinlessthan10gramsperdeciliteratanytimeduringthestudy.Theresearchersfoundthat:43patientsinthe20-mg/kg(64.2%)armhadanearlyvirologicresponse,asdid40(57.1%)and37(54.4%)inthe25-and30-mg/kgarms.Atthesametime,36ribavirinpatients(51.4%)hadanearlyvirologicresponse,notsignificantlydifferentfromanyofthetaribavirinarms.Fewerpatientsontaribavirinrequireddosereductions(13%to28%,dependingonthedose)comparedwith32%ofribavirin.Theanemiarateswere13.4%and15