Maraviroc: A CCR5-receptor antagonist for the treatment of HIV-1 infection

Background: The emergence of viral resistance is one of the greatest challenges in the treatment of HIV infection. Maraviroc is the first member of a new class of antiretroviral medications, the CCR5-receptor antagonists. It is approved by the US Food and Drug Administration (FDA) for use in combination with other antiretroviral agents in treatment-experienced patients infected with multidrug-resistant, CCR5-tropic HIV-1. Objective: This article provides an overview of the pharmacology, efficacy, and tolerability of maraviroc in the treatment of HIV-1 infection. Methods: Relevant information was identified through a search of MEDLINE (January 2000-May 2008) using the terms maraviroc, UK-427,8S7, and CCRS-receptor antagonist. Also consulted were abstracts from the International AIDS Society Conference, the Conference on Retroviruses and Opportunistic Infections, and other relevant scientific meetings. Additional publications were found by searching the reference lists of the identified articles and the FDA Web site. Results: Maraviroc is a selective, reversible, small-molecule CCR5-receptor antagonist. In vitro, it has potent anti-HIV-1 activity, with a mean 90% inhibitory concentration of 2.0 nmol/L. It is widely distributed, with a V-d of similar to 194 L. Maraviroc is moderately metabolized in the liver (65.3%), primarily via the cytochrome P450 3A4 isozyme. It has an elimination t(1/2) of 15.9 to 22.9 hours. Until more data are available, maraviroc should be avoided in patients with severe hepatic insufficiency; dose adjustment does not appear to be necessary on the basis of age, sex, or renal function. In 2 Phase IIb/III studies, maraviroc 300 mg PO QD or BID was found to be more efficacious than placebo in reducing the viral load at 48 weeks in treatment-experienced, CCR5-tropic HIV-1-infected patients receiving an optimized background regimen (difference vs placebo-QD arm: -0.89 log(10) copies/mL [97.5% CI, -1.17 to -0.62]; BID arm: -1.05 log(10) copies/mL [97.5% CI, -1.33 to -0.78]). The proportion of patients with a viral load < 50 copies/mL was 43.2% in the QD arm and 45.5% in the BID arm, compared with 16.7% in the placebo arm (P < 0.001, both treatment arms vs placebo). In treatment-naive patients infected with CCR5-tropic virus only, maraviroc 300 mg PO BID was not noninferior to oral efavirenz 600 mg QD (difference = -4.2%; lower bound of the 1-sided 97.5% CI, -10.9 [predefined statistical cutoff for noninferiority, -10]). Maraviroc was generally well tolerated in clinical trials. The most frequently reported (>= 5%) adverse events were upper respiratory tract infection (20.0%), cough (12.7%), pyrexia (12.0%), rash (9.6%), musculoskeletal complaints (8.7%,), gastrointestinal and abdominal pain (8.2%), dizziness (8.2%), appetite disorders (7.3%), insomnia (7.0%c), herpes infection (6.8%), sinusitis (6.3%), joint complaints (6.1%), bronchitis (5.9%), and constipation (5.4%). The recommended dose of maraviroc differs based on concomitant medications, ranging from 150 to 600 mg BID. Conclusion: When used in combination with other antiretroviral agents, maraviroc appears to be a promising agent for treatment-experienced patients infected with multidrug-resistant, CCR5-tropic HIV-1.