The FDA approved Stribild (elvitegravir, cobicistat, emtricitabine, tenofovir disproxil fumarate), a new once-a-day combination pull to treat HIV-1 infection in adults who have never received prior treatment for HIV infection.
The Stribild formulation contains two previously approved HIV drugs in addition to two new drugs, elvitegravir and cobicistat. Elvitegravir is an HIV integrase strand transfer inhibitor, a drug that interferes with one of the enzymes that HIV needs to multiply. Covicistat, a pharmacokinetic enhancer, inhibits an enzyme that metabolizes certain HIV drugs and is used to prolong the effect of elvitegravir. The combination of emtricitabine and tenofovir disoproxil fumarate, approved in 2004 and marketed as Truvada, blocks the action of another enzyme that HIV needs to replicate in the body. Combined, these drugs provide a complete treatment regimen for HIV infection.
The safety and effectiveness of Stribild was evaluated in 1,408 patients not previously treated for HIV in two double-blind clinical trials. Patients were randomly assigned to receive Stribild or Atripla, an HIV drug that contains Truvada and efavirenz, once daily in the first trial; and Stribild or Truvada plus atazanavir and ritonavir once daily in the second trial. The studies were designed to measure the percentage of patients who had an undetectable amount of HIV in their blood at 48 weeks.
Results showed that between 88% and 90% of patients treated with Stribild had an undetectable amount of HIV in their blood, compared with 84% treated with Atripla and 87% treated with Truvada and atazanavir and ritonavir.
Similar to the labels of many other drugs used to treat HIV, Stribild’s label carries a Boxed Warning alerting patients and healthcare professionals that the drug can cause a build-up of lactic acid in the blood and severe liver problems, both of which can be fatal. The Boxed Warning also states that Stribild is not approved to treat chronic hepatitis B virus infections.
Common side effects observed in clinical trials include nausea and diarrhea. Serious side effects include new or worsening kidney problems, decreased bone mineral density, fat distribution and changes in the immune system (immune reconstitution syndrome). Stribild’s label gives advice to healthcare providers on how to monitor patients for kidney or bone side effects.
Stribild’s approval is the latest HIV/AIDS-related action taken by the FDA this year. Other actions include approval of the first over-the-counter home-use rapid HIV test; approval of the first drug for pre-exposure prophylaxis in combination with safer sex practices to reduce the risk of sexually acquired HIV infection in adults at high risk; and commemoration of the full or tentative approvals of more than 150 antiretroviral products for the President’s Emergency Plan for AIDS Relief (PEPFAR) to treat those in countries most affected by the HIV/AIDS epidemic.
Additional studies are required to be conducted by Gilead Sciences, Stribilid’s manufacturer, in order to help further characterize the drug’s safety in women and children, how resistance develops to Stribild, and the possibility of interactions between Stribild and other drugs.
Gilead Sciences is based in Foster City, Calif.