Gilead Sciences announced results from Study 109, a Phase 3 study evaluating once daily single tablet regimen (STR) of elvitegravir 150mg, cobicistat 150mg, emtricitabine 200mg, and tenofovir alafenamide 10mg (E/C/F/TAF) in adults switching from tenofovir disoproxil fumarate (TDF) containing regimens.

Study 109 is a randomized, open-label, multi-national, active-controlled study designed to evaluate the non-inferiority of switching to a TAF-containing combination single tablet regimen relative to maintaining TDF-containing combination regimens in virologically-suppressed HIV-1 positive adult subjects (HIV-1 RNA <50 copies/mL at Week 48) following the switch. The study was also designed to test for statistical superiority between the two study arms once non-inferiority was achieved. In the open-label study, virologically suppressed adults with normal renal function taking one of four different TDF-based regimens for at least 96 weeks were randomized 2:1 to receive E/C/F/TAF or to maintain their TDF-based regimen. The four TDF-based treatments evaluated in the study included the following single tablet and multi-pill regimens: Stribild (elvitegravir/cobicistat/emtricitabine/TDF); Atripla (efavirenz/emtricitabine/TDF); atazanavir/ritonavir + Truvada (emtricitabine/TDF) or atazanavir/cobicistat + Truvada.

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The study met its primary endpoint by demonstrating non-inferiority of E/C/F/TAF to the TDF-based regimens at Week 48. The study also demonstrated statistical superiority among patients with HIV-1 RNA levels <50 copies/mL at Week 48. Among the 1,436 patients who were randomized in the study (E/C/F/TAF, 959 patients; TDF-based regimen, 477 patients), virologic success rates at Week 48 were higher in patients taking E/C/F/TAF (97% vs. 93% for all TDF-based regimens; 95% CI: 1.6–6.7%). The rates of virologic failure were similar between the two arms (E/C/F/TAF, 1%; TDF-based regimen, 1.3%).

In November 2014, Gilead filed a New Drug Application (NDA) with the Food and Drug Administration (FDA) for E/C/F/TAF.

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