When and how to use maraviroc in HIV-infected patients

CCR5 antagonists have recently entered the HIV armamentarium. This novel class of drugs inhibit viral entry blocking host cellular receptors, and therefore display unique mechanisms of resistance, different from other antiretroviral drugs. Maraviroc only blocks replication of R5 viruses and accordingly patients with X4 or D/M viruses do not or only marginally benefit from maraviroc therapy. Viral tropism has to be tested before considering maraviroc prescription. Phenotypic and more recently genotypic tools have been demonstrated to reliably estimate HIV-1 tropism in most cases and predict viral response. Beyond the initial approval only for antiretroviral-experienced patients, the pharmacokinetic properties and safety profile of maraviroc may support an earlier use of the drug. Studies using maraviroc in drug-naive patients and as part of switch strategies are warranted.