Maraviroc (Celsentri or Selzentry; Pfizer Ltd., Sandwich, UK) belongs to a new class of anti-HIV drugs named CCR5 antagonists, which block HIV entry into cells. Viral entry is an attractive step for the development of new agents against HIV variants resistant to current antiretroviral drugs. HIV gains entry into CD4-expressing cells through a series of sequential interactions between the envelope glycoprotein gp120 and the CD4 receptor and one of two coreceptor molecules, chemokine (C-C motif) receptor 5 (CCR5) or chemokine (C-X-C motif) receptor 4 (CXCR4), which are expressed on the surface of target cells. Maraviroc specifically inhibits the replication of R5-tropic HIV variants by an allosteric mechanism after binding to the transmembrane CCR5 coreceptor cavity. Because of its exclusive activity against CCR5 tropic strains, viral tropism testing is mandatory before using CCR5 antagonists in the clinic.
Maraviroc is a substrate for the P-glycoprotein and the cytochrome P450 (3A4), both of which are involved in the metabolism of multiple other agents, including several antiretroviral drugs. Therefore, drug interactions using maraviroc should be kept in mind. Briefly, the standard 300 mg twice daily dose of maraviroc does not require changes when the drug is given concomitantly with methadone, statins, nevirapine, cotrimoxazole, etinilestradiol nor pegylated interferon and ribavirin. However, dose adjustments have to be made when maraviroc is used along with some potent inhibitors or inducers of CYP3A4.