Maraviroc 376348-65-1

Mechanism of action

Maraviroc is an entry inhibitor. Specifically, maraviroc blocks the chemokine receptor CCR5 which HIV uses as a coreceptor to bind and enter a human macrophage. Because HIV can also use another coreceptor, CXCR4, an HIV tropism test such as a trofile assay must be performed to determine if the drug will be effective.

Development and approval

Maraviroc, originally designated UK-427857, was developed by the drug company Pfizer in its UK labs located in Sandwich. On April 24, 2007 the U. S. Food and Drug Administration advisory panel reviewing maraviroc's New Drug Application unanimously recommended approval for the new drug, and the drug received full FDA approval on August 6, 2007 for use in treatment experienced patients. On September 24, 2007, Pfizer announced that the European Commission approved Maraviroc. Industry experts forecast annual Maraviroc sales of $500 million by 2011.

Efficacy

Two randomized, placebo-controlled clinical trials, known as MOTIVATE 1 & 2, compared 209 patients receiving optimized therapy plus a placebo to 426 patients receiving optimized therapy plus 150 mg maraviroc once daily and 414 patients receiving optimized therapy plus 150 mg maraviroc twice daily. At 48 weeks, 55% of participants receiving maraviroc once daily and 60% of participants receiving the drug twice daily achieved a viral load of less than 400 copies/mL compared with 26% of those taking placebo; about 44% of the once-daily and 45% of the twice-daily maraviroc group had a viral load of less than 50 copies/mL compared with about 23% of those who received placebo. In addition, those who received the entry inhibitor had a mean increase in CD4 cells of 110 cells/µL in the once-daily group, 106 cells/µL in the twice-daily group, and 56 cells/µL in the placebo group.

Safety

The MOTIVATE trials showed no clinically relevant differences in safety between the maraviroc and placebo groups. However, researchers question the long-term safety of blocking CCR5, a receptor whose function in the healthy individual is not fully understood.