Darunavir: A Review of its Use in the Management of HIV Infection in Adults

Authors: McKeage, Kate; Perry, Caroline M.; Keam, Susan J.

Source: Drugs, Volume 69, Number 4, 2009 , pp. 477-503(27)

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Abstract:

Abstract Darunavir is an oral nonpeptidic HIV-1 protease inhibitor (PI) that is used, together with a low boosting dose of ritonavir, as part of an antiretroviral therapy (ART) regimen in treatment-experienced and -naive patients with HIV-1 infection.

Compared with early-generation PIs, boosted darunavir has a high genetic barrier to resistance and is active against multidrug-resistant HIV isolates. In clinical trials in treatment-experienced patients with HIV-1 infection receiving an optimized background regimen (OBR), twice-daily boosted darunavir was more effective than investigator-selected ritonavir-boosted control PIs (CPIs) or ritonavir-boosted lopinavir. In clinical trials in treatment-naive patients with HIV-1 infection receiving a fixed background regimen, once-daily boosted darunavir was noninferior to boosted lopinavir at 48 weeks and more effective than boosted lopinavir at 96weeks. Boosted darunavir was generally well tolerated in patients with HIV-1 infection in clinical trials. It was associated with a lower incidence of diarrhoea than CPIs or lopinavir in treatment-experienced or -naive patients, and fewer lipid abnormalities than lopinavir in treatment-naive patients. Thus, for the management of treatment-experienced or -naive patients with HIV-1 infection, a ritonavir-boosted darunavir-based ART regimen is a valuable treatment option.

Pharmacological Properties Darunavir is an oral nonpeptidic HIV-1 PI that selectively inhibits the cleavage of HIV gag and gag-pol polyproteins, thereby preventing viral maturation. Darunavir is highly potent against laboratory strains and clinical isolates of wild-type and multidrug-resistant HIV and has limited cytotoxicity. In an in vitro study in MT-2 cells, the potency of darunavir was greater than that of saquinavir, amprenavir, nelfinavir, indinavir, lopinavir and ritonavir. Darunavir binds with high affinity to HIV-1 protease, including multidrug-resistant proteases, and retains potency against multidrug-resistant HIV-1 strains. Although some potential may exist for cross-resistance with amprenavir, darunavir did not display cross-resistance with other PIs in vitro.

In a 24-week analysis of pooled data from the POWER 1 and 2 studies in treatment-experienced patients, 11 protease mutations associated with a reduced response to boosted darunavir were identified (V11I, V32I, L33F, I47V, I50V, I54L/M, G73S, L76V, I84V and L89V). The presence of at least three darunavir resistance-associated mutations (prevalent in ≈7-9% of treatment-experienced patients) together with a high number of protease resistance-associated mutations were required to confer darunavir resistance. In the 48-week analysis of treatment-experienced patients with virological failure in the the TITAN study, fewer in the boosted darunavir group than in the boosted lopinavir group developed additional mutations or lost susceptibility to PIs compared with baseline. In treatment-naive patients, no primary PI-resistance-associated mutations developed in patients with an available genotype at baseline and endpoint during 96 weeks of treatment with boosted darunavir or boosted lopinavir.

Oral darunavir, boosted with low-dose ritonavir, is rapidly absorbed, generally reaching peak plasma concentrations within 2.5-4 hours. The bioavailability of oral darunavir is increased by about 30% when taken with food. Darunavir is primarily metabolized by the hepatic cytochrome P450 (CYP) enzymes, primarily CYP3A. The `boosting' dose of ritonavir acts an an inhibitor of CYP3A, thereby increasing darunavir bioavailability. Drug interactions can result when darunavir is coadministered with other drugs that are inducers or inhibitors of, or act as substrates for, CYP3A. The mean elimination half-life of boosted darunavir is ≈15 hours.

Therapeutic Efficacy In treatment-experienced patients with HIV-1 infection, the therapeutic efficacy of oral twice-daily darunavir 600 mg, boosted with ritonavir 100 mg, versus that of investigator selected boosted CPIs (POWER studies) or versus twice-daily boosted lopinavir (administered as a fixed dose combination of lopinavir/ritonavir 400/100 mg) [TITAN study] has been evaluated in phase IIb and III studies. All patients received concurrent treatment with an OBR.

Document Type: Research article

Affiliations: 1: Wolters Kluwer Health ∣ Adis, Auckland, New Zealand, an editorial office of Wolters Kluwer Health, Philadelphia, Pennsylvania, USA

Publication date: 2009-01-01

Darunavir: A Review of its Use in the Management of HIV Infection in Adults

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