The U.S. Food and Drug Administration (FDA) approved two new combination tablets that each include an existing protease inhibitor that is boosted by Tybost (cobicistat). The two new drugs, Prezcobix (darunavir/cobicistat) and Evotaz (atazanavir/cobicistat), are to be used in combination with other antiretrovirals (ARVs) to treat HIV. As single drugs, darunavir is marketed as Prezista while atazanavir’s brand name is Reyataz.

“The approval of Prezcobix and Evotaz makes taking protease inhibitor–based regimens easier for patients,” says Joel Gallant, MD, MPH, medical director of specialty services at Southwest CARE Center in Santa Fe, New Mexico. Fewer pills may also mean lower co-pay costs, he adds.

Like Norvir (ritonavir), Tybost operates by raising the drug levels of other ARVs. Tybost is already a component of the single-pill regimen Stribild (elvitegravir/cobicistat/tenofovir/emtricitabine), which was approved in 2012.

Research on Evotaz found that using Tybost as a booster led to essentially the same rates of viral suppression as an equivalent regimen that was boosted with Norvir instead.

Prezcobix’s success rate is based on research showing the efficacy of Norvir–boosted Prezista, as well as a study showing that boosting Prezista with Tybost instead (in other words, taking Prezcobix) leads to similar levels of Prezista in the body.