Coadministration of sofosbuvir/velpatasvir/voxilaprevir (400/100/100 mg once daily plus 100 mg voxilaprevir to approximate systemic voxilaprevir exposure in HCV-infected subjects), emtricitabine (200 mg once daily) and tenofovir alafenamide (10 mg once daily) was studied using the elvitegravir/cobicistat/emtricitabine/tenofovir alafenamide fixed-dose combination tablet. There was no effect on the AUC, Cmax or Cmin of emtricitabine; tenofovir alafenamide AUC was unchanged but Cmax decreased by 21%. Sofosbuvir AUC was unchanged but Cmax increased by 27% The AUC of GS-331007 (sofosbuvir metabolite) increased by 43%, but there was no change in Cmax. There was no change in velpatasvir AUC and Cmax, but Cmin increased by 46%. Voxilaprevir AUC, Cmin and Cmax increased by 171%, 350% and 92%, respectively. Coadministration of sofosbuvir/velpatasvir/voxilaprevir (400/100/100 mg once daily plus 100 mg voxilaprevir to approximate systemic voxilaprevir exposure in HCV-infected subjects), emtricitabine (200 mg once daily) and tenofovir alafenamide (10 mg once daily) was studied using the emtricitabine/rilpivirine/tenofovir alafenamide fixed-dose combination tablet. There was no effect on the AUC, Cmax or Cmin of emtricitabine. Tenofovir alafenamide AUC and Cmax increased by 52% and 32%. There was no effect on the AUC and Cmax of sofosbuvir or GS-331007 (sofosbuvir metabolite), nor on the AUC, Cmax and Cmin of velpatasvir or voxilaprevir. No dose adjustment of sofosbuvir, velpatasvir or voxilaprevir is required. For HIV-1 treatment, dose Descovy according to the concomitant antiretroviral.

Coadministration of emtricitabine/tenofovir alafenamide (200/25 mg once daily with bictegravir or rilpivirine) and sofosbuvir/velpatasvir/voxilaprevir (400/100/100 once daily, plus 100 mg voxilaprevir to approximate systemic voxilaprevir exposure in HCV-infected subjects) was studied in healthy volunteers (n=30). Bictegravir and emtricitabine AUCs were unaltered by coadministration, but AUC of tenofovir alafenamide increased by 52-58% and AUC of tenofovir increased by 67-79%. There was no effect of coadministration on AUCs of sofosbuvir, GS-331007 (the major circulating metabolite of sofosbuvir), velpatasvir or voxilaprevir. Coadministration of emtricitabine/tenofovir alafenamide (200/10 mg once daily with elvitegravir/cobicistat) and sofosbuvir/velpatasvir/voxilaprevir (400/100/100 once daily, plus 100 mg voxilaprevir) had no significant effect on the AUCs of emtricitabine, tenofovir, tenofovir alafenamide, sofosbuvir and velpatasvir, but increased GS-331007 AUC by 43% and increased voxilaprevir AUC by 171%