6 weeks 812 weeks 12 weeks genotype 1 india ledifos pharma companies newer daas mobile clinics special populations additional genotypes ribavirin depending renal impairment liver condition vary based enzyme vital generic licensing generic version chronic hepatiti virus hcv infection daily oral tablet generic competition partnerships treat chronic hepatitis public health agencies intravenous drug users fixeddose antiviral medication original manufacturers summary infection typical usage works ledipasvir inhibits fixeddose combination medication