Studies examine ability of antiretroviral Maraviroc to control HIV viral loads

According to two studies sponsored by drugmaker Pfizer and published in the New England Journal of Medicine on Wednesday, the antiretroviral drug maraviroc, which is sold as Selzentry by Pfizer, might help control viral loads among HIV-positive people who have shown resistance to other treatments, Reuters reports.

The studies were conducted among 1,049 people in Australia, Europe and North America, and all the participants were resistant to three of the six classes of HIV/AIDS drugs that are available. At the study's 48-week mark, at least 42% of the people who took maraviroc once or twice daily with a standard HIV/AIDS drug combination therapy reported viral loads below levels that cause visible damage to the immune system, compared with 18% of the participants who received a placebo along with a standard combination therapy.

Maraviroc belongs to a new class of HIV drugs called HIV entry inhibitors, or CCR5 receptor antagonists, which are being developed to address drug resistance to available therapies. All of the study participants tested positive for the strain of the virus that uses CCR5, according to Reuters. During the study, participants also were given antiretrovirals that target the virus' ability to replicate, Reuters reports. Researchers said that maraviroc did not produce any unusual side effects in the participants. Although the drug's label currently warns against possible liver problems, Roy Gulick of the Weill Cornell Medical Center in New York who led the study said that "our study simply didn't see liver toxicity, so that's reassuring." According to Gulick, results from the study's 96-week mark are being examined and might be presented at a meeting in November (Emery, Reuters, 10/1).

The first study is available online. The second study and a related editorial also are available online.