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Home > Treatment > HIV Meds Quarterly > Spring 2009 > New Pharmacokinetic
New Pharmacokinetic Booster on the Horizon

Many protease inhibitors require the pharmacokinetic boosting effects of ritonavir to achieve adequate serum levels. But because of issues such as tolerability, cost, and lack of coformulated preparations, many clinicians have yearned for alternatives to ritonavir. Researchers at the 16th Conference on Retroviruses and Opportunistic Infections in Montreal in February presented data on two alternative pharmacokinetic enhancers that are now in clinical development. The more promising of these two at present is GS-9350. This compound, which is in phase III studies, is a potent and specific CYP 3A4 inhibitor, but is devoid of any anti-HIV activity. Studies in humans have demonstrated that the compound is well tolerated. GS-9350 is intended to be a pharmacoenhancer for elvitegravir, an investigational integrase inhibitor, so that once-daily dosing of elvitegravir is possible. Current development plans are to combine GS-9350 with elvitegravir, tenofovir, and emtricitabine in a 4-drug fixed-dose combination tablet. However, GS-9350 also will be studied as a booster for protease inhibitors.


  1. Mathias A, Lee M, Callebaut C, et al. GS-9350: a pharmaco-enhancer without anti-HIV activity. In: Program and abstracts of the 16th Conference on Retroviruses and Opportunistic Infections; February 8-11, 2009; Montreal. Abstract 40.