September 25, 2014
A next-generation boosting agent and an integrase inhibitor joined the growing ranks of approved HIV medications on Sept. 24, when the U.S. Food and Drug Administration (FDA) stamped its seal of approval on Tybost (known generically as cobicistat) and Vitekta (elvitegravir).
With these approvals, each component of the single-tablet regimen Stribild (elvitegravir/cobicistat/emtricitabine/tenofovir) is now green-lighted for use separately in HIV treatment regimens in the U.S. Stribild itself was approved by the FDA in August 2012.
Tybost is indicated specifically for use as a booster drug. The approval notice released by the FDA restricts the indication for the drug's use, so it is recommended only to enhance the potency of two once-daily protease inhibitors: Reyataz (atazanavir) and Prezista (darunavir). (Tybost is specifically not intended for use with twice-daily dosing of these drugs.)
Vitekta, meanwhile, becomes the third integrase inhibitor approved by the FDA for individual use, alongside Isentress (raltegravir) and Tivicay (dolutegravir). The indication for Vitekta specifically calls for the drug to be used alongside a boosted protease inhibitor -- although the indicated booster is Norvir, not the newly approved Tybost. In fact, the FDA approval notice specifically warns that Vitekta should not be used alongside a Tybost-boosted protease inhibitor. (In Stribild, Vitekta and Tybost are combined with two NRTIs.)
A major clinical trial pitting Vitekta against Isentress in HIV treatment-experienced people found that the two drugs had similar efficacy and safety, although people taking Vitekta were more likely to experience diarrhea and less likely to experience an increase in liver enzymes.
This marked the second trip through the FDA approval process for both drugs; they were rejected in April 2013 on the basis of "deficiencies in documentation and validation of certain quality testing procedures and methods," according to Gilead Sciences, which markets the two medications.
Tybost was approved by the European Commission on Sept. 25, 2013. Vitekta has been approved for use in Europe since November 2013. Both drugs are also approved for use in Australia and Canada, according to Gilead.
Separately, Canada issued regulatory approval on Sept. 17 for a fixed-dose combination of cobicistat and the protease inhibitor darunavir that will be marketed as Prezcobix.
Myles Helfand is the editorial director of TheBody.com and TheBodyPRO.com.
Follow Myles on Twitter: @MylesatTheBody.
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