Two boosted protease inhibitor (PI) coformulations have just been approved by the FDA. These are:
Darunavir 800 mg + cobicistat 150 mg (Prezcobix), and
Atazanavir 300 mg + cobicistat 150 mg (Evotaz)
In these fixed-dose combinations, cobicistat is used as the pharmacokinetic booster of the PI (rather than ritonavir); they should not be used with ritonavir or with other PIs. These combinations previously have been available as separate pills, and FDA approval of the coformulations was based on studies showing pharmacokinetic bioequivalence of the fixed-dose combinations compared with the single agents.
Each should be dosed once daily with food, and in combination with other appropriate ARVs. It should be noted that the darunavir/cobicistat fixed-dose combination should be used only in patients without darunavir-associated mutations.
The coformulations will make it possible to treat patients with more compact PI-based regimens, (and single-pill combinations containing these boosted PIs + 2 NRTIs may be available in the future). Adverse effects to cobicistat appear to be very similar to those associated with ritonavir, and drug-drug interactions also are about the same.
The prescribing information for each agent is available at Drugs@FDA.