Sofosbuvir 400 mg, Velpatasvir 100 mg Tablets

Sofosbuvir and velpatasvir tablets (400 mg/100 mg) are a fixed-dose combination of sofosbuvir and velpatasvir, which are direct-acting antiviral agents against the hepatitis C virus [see Microbiology (12.4)].

The pharmacokinetic properties of sofosbuvir and velpatasvir are provided in Table 5. The multiple dose pharmacokinetic parameters of sofosbuvir and its metabolite, GS-331007, and velpatasvir are provided in Table 6.

Sofosbuvir and GS-331007 AUC0–24 and Cmax were similar in healthy adult subjects and subjects with HCV infection. Relative to healthy subjects (N=331), velpatasvir AUC0–24 and Cmax were 37% lower and 42% lower, respectively, in HCV-infected subjects.

Velpatasvir AUC increases in a greater than proportional manner from 5 to 50 mg and in a less than proportional manner from 50 to 450 mg in healthy volunteers. However, velpatasvir exhibited more than or near dose-proportional increase in exposures 25 mg to 150 mg in HCV-infected patients when coadministered with sofosbuvir. Sofosbuvir and GS-331007 AUCs are near dose-proportional over the dose range of 200 mg to 1200 mg.

Drug Interaction Studies — After oral administration of sofosbuvir and velpatasvir, sofosbuvir is rapidly absorbed and subject to extensive first-pass hepatic extraction (hydrolysis followed by sequential phosphorylation) to form the pharmacologically active triphosphate. In clinical pharmacology studies, both sofosbuvir and the primary circulating metabolite GS-331007 (dephosphorylated nucleotide metabolite) were monitored for purposes of pharmacokinetic analyses.

Sofosbuvir and velpatasvir are substrates of drug transporters P-gp and BCRP while GS-331007 is not. Velpatasvir is also transported by OATP1B1 and OATP1B3. In vitro, slow metabolic turnover of velpatasvir by CYP2B6, CYP2C8, and CYP3A4 was observed. Inducers of P-gp and/or moderate to strong inducers of CYP2B6, CYP2C8, or CYP3A4 (e.g., rifampin, St. John's wort, carbamazepine) may decrease plasma concentrations of sofosbuvir and/or velpatasvir, leading to reduced therapeutic effect of sofosbuvir and velpatasvir [see Warnings and Precautions (5.3) and Drug Interactions (7.3)]. Coadministration with drugs that inhibit P-gp and/or BCRP may increase sofosbuvir and/or velpatasvir plasma concentrations without increasing GS-331007 plasma concentration. Drugs that inhibit CYP2B6, CYP2C8, or CYP3A4 may increase plasma concentration of velpatasvir.

Velpatasvir is an inhibitor of drug transporter P-gp, BCRP, OATP1B1, OATP1B3, and OATP2B1, and its involvement in drug interactions with these transporters is primarily limited to the process of absorption. At clinically relevant concentration, velpatasvir is not an inhibitor of hepatic transporters OATP1A2 or OCT1, renal transporters OCT2, OAT1, OAT3, or MATE1, or CYP or UGT1A1 enzymes.

Sofosbuvir and GS-331007 are not inhibitors of drug transporters P-gp, BCRP, OATP1B1, OATP1B3, and OCT1 and GS-331007 is not an inhibitor of OAT1, OAT3, OCT2, and MATE1. Sofosbuvir and GS-331007 are not inhibitors or inducers of CYP or UGT1A1 enzymes.

The effects of coadministered drugs on the exposure of sofosbuvir, GS-331007, and velpatasvir are shown in Table 8. The effects of sofosbuvir, velpatasvir, or sofosbuvir and velpatasvir on the exposure of coadministered drugs are shown in Table 9 [see Drug Interactions (7)].

No effect on the pharmacokinetic parameters of sofosbuvir, GS-331007, or velpatasvir was observed with dolutegravir; the combination of emtricitabine, rilpivirine, and tenofovir DF; emtricitabine; raltegravir; or tenofovir DF.

No effect on the pharmacokinetic parameters of the following coadministered drugs was observed or is expected with sofosbuvir and velpatasvir (buprenorphine/naloxone, dolutegravir, lopinavir/ritonavir, or methadone) or its components sofosbuvir (cyclosporine) or velpatasvir (cyclosporine).