Comprehensive, up-to-date information on HIV/AIDS treatment, prevention, and policy from the University of California San Francisco

The FDA has approved the fixed-dose combination of elvitegravir/cobicistat/tenofovir/emtricitabine as a single-pill regimen for initial treatment of HIV-infected adults. Known as the "Quad" pill in casual parlance, this combination is branded as Stribild. The recommended dosage is 1 pill, once daily, taken with food.

The combination includes two new components, elvitegravir and cobicistat. Elvitegravir is an integrase inhibitor that is given once daily but requires pharmacokinetic boosting. Cobicistat is a pharmacokinetic enhancer of elvitegravir, and certain other drugs, but has no anti-HIV effect (unlike ritonavir). Interactions between the new agents and other drugs have not been well studied, but numerous interactions involving cobicistat in particular are possible, and the Stribild package insert contains a long list of cautions regarding potential interactions with numerous medications.

In Phase 3 studies, elvitegravir/cobicistat/tenofovir/emtricitabine generally was well tolerated. Cobicistat may increase serum creatinine (and decrease estimated GFR) via inhibition of tubular secretion of creatinine; it does not appear to affect actual GFR. This effect is small and stable over time. Having said that, the Quad coformulation also includes tenofovir, which has known nephrotoxicity and whose effects may be enhanced by cobicistat. The manufacturer cautions that this combination should not be initiated in persons with CrCl <70 mL/min, and should be discontinued in those with CrCl <50 mL/min. Other possible adverse effects of cobicistat include nausea and diarrhea.

The DHHS adult ARV treatment guidelines have been amended to include coformulated elvitegravir/cobicistat/tenofovir/emtricitabine as an "alternative" regimen for use in ART-naive persons with CrCl >70 mL/min.

Approval of elvitegravir and cobicistat as separate agents is under consideration. For further information, see the Stribild package label.

In recent months, the FDA has approved generic formulations of abacavir (300 mg tablets) and nevirapine (200 mg tablets and oral suspension) as well as a lamivudine/zidovudine combination tablet. Previously approved generic ARVs are medications that are no longer in common usage in the United States: didanosine, stavudine, and zidovudine. It is not yet clear what effect the new approvals, and the approvals of other generic ARV medications expected in the next 1-2 years, will have on ARV prescribing practice (and insurance coverage) in the United States.

The fixed-dose combination of tenofovir + emtricitabine (Truvada) has been approved by the FDA for use as preexposure prophylaxis (PrEP) for adults at high risk of HIV infection via sexual routes. PrEP is intended only for individuals who are tested and confirmed to be HIV uninfected, and as part of a comprehensive prevention strategy. Potential adverse effects of tenofovir in HIV-uninfected persons, including renal and bone toxicity, and possible risks to fetal development in women who become pregnant while taking PrEP, have not been studied fully.

The CDC has released an interim guidance on use of tenofovir/emtricitabine as PrEP in heterosexual adults; an earlier interim guidance addresses PrEP in MSM.[1,2] The new guidance includes much practical information on screening for, initiating, and monitoring tenofovir/emtricitabine PrEP (including information on issues involved in the use of PrEP during pregnancy), and it is a valuable resource on administration of PrEP for all adults regardless of their risk category.

References

1. Centers for Disease Control and Prevention. Interim Guidance for Clinicians Considering the Use of Preexposure Prophylaxis for the Prevention of HIV Infection in Heterosexually Active Adults. MMWR Morb Mortal Wkly Rep. 2012 Aug 10;61:586-9.

2. Centers for Disease Control and Prevention. Interim Guidance: Preexposure Prophylaxis for the Prevention of HIV Infection in Men Who Have Sex with Men. MMWR Morb Mortal Wkly Rep. 2011 Jan 28;60(3):65-8.