News Feature | September 25, 2014

Gilead's HIV Regimen Pulls Weight In Phase 3 Studies

By Cyndi Root

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Gilead Sciences plans U.S. and EU regulatory filings in Q4 2014 for HIV drug tenofovir alafenamide (TAF) following good news from two Phase 3 studies. The announcement in a press release revealed that TAF showed non-inferiority to the company’s other treatment for HIV, Stribild, and demonstrated more favorable renal and bone safety.

Norbert Bischofberger, PhD, EVP at Gilead Sciences, said, “As individuals with HIV are living longer, there is a need for treatments that are not only highly effective, but also offer an improved safety profile.”

Tenofovir Alafenamide

Tenofovir alafenamide (TAF) is a prodrug of tenofovir, the active agent in Viread (tenofovir disoproxil fumarate). A nucleotide reverse transcriptase inhibitor (NtRTI), TAF is effective at a 10 times lower dose than Viread, enabling a single tablet regime and new fixed-dose combinations. The newly reported studies utilized a combination of TAF, elvitegravir, cobicistat, and emtricitabine.

  • Elvitegravir is in the integrase inhibitor class, which blocks viral entry to the human cell genetic material. The agent is licensed from Japan Tobacco and under review by the Food and Drug Administration (FDA).
  • Cobicistat is a cytochrome P450 3A (CYP3A) inhibitor that suppresses CYP3A, acting only as a pharmacokinetic enhancer with no antiviral activity. It is approved in Europe, Australia, and Canada, and is being reviewed by the FDA.
  • Emtricitabine is also a NRTI, like TAF, that works to prevent HIV replication and lower HIV presence in the blood.  

Bischofberger stated that based on the Phase 3 results, Gilead believes that the E/C/F/TAF single tablet regimen has potential for treatment-naïve patients and for optimizing HIV therapy. The favorable safety results are also noteworthy, as HIV patients are living longer and have an increased chance at quality of life.

Gilead’s HIV Studies

Gilead is conducting several studies evaluating the TAF combination regime. The Phase 3 studies are being conducted among multiple HIV patient populations. The studies include women switched from a multi-pill regimen; patients who have switched from a multi-pill Truvada combination; patients with renal impairment; patients with a history of antiviral drug resistance; and treatment-naïve adolescents.  

Gilead announced in April that the FDA had accepted the company’s two New Drug Applications (NDAs) for cobicistat and elvitegravir in HIV. According to the Prescription Drug User Fee Act (PDUFA), the federal agency must act on the applications by October 3, 2014 for cobicistat and October 4, 2014 for elvitegravir.