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Medical News
FDA Approves Pfizer's Antiretroviral Maraviroc

August 7, 2007

FDA on Monday approved Pfizer antiretroviral drug maraviroc, which belongs to a new class of antiretrovirals that could provide an alternative to HIV-positive people who have developed resistance to multiple drugs, the Los Angeles Times reports (Chong, Los Angeles Times, 8/7). FDA gave expedited approval of maraviroc for use in combination with other antiretrovirals (CQ HealthBeat, 8/6).

Maraviroc works by blocking a protein, called CCR5, on human immune system cells that HIV uses as a portal to enter and infect the cell. Pfizer has proposed using the drug to treat people with advanced HIV or AIDS who have not responded to other medications. Pfizer last month also announced that maraviroc can reduce HIV viral loads among people who have never taken antiretrovirals. The company plans to offer the drug with a test developed by Monogram Biosciencesthat determines if people are likely to respond to the treatment (Kaiser Daily HIV/AIDS Report, 7/26). Pfizer will sell maraviroc under the brand name Selzentry (Wall Street Journal, 8/7).

FDA approved maraviroc on the condition that the drug's label include a black-box warning -- the "strongest possible advisory" -- according to the Times. The drug also will have a warning about an increased risk of heart attack (Los Angeles Times, 8/7).

According to Debra Birnkrant, director of FDA's division of antiviral drug products, the approval comes after the agency concluded that HIV-positive people who have become resistant to other treatments need a new option. She added that FDA is requiring Pfizer to conduct further research into the drug's long-term side effects. According to Birnkrant, maraviroc is aimed at HIV-positive people who are quickly developing resistance to other available antiretrovirals and not people newly diagnosed as HIV-positive. For those people who are developing drug resistance to other treatments, maraviroc's "benefits clearly outweigh the risks," Birnkrant said, adding, "That doesn't mean there aren't any risks." According to a Pfizer spokesperson, maraviroc will be available in September and the wholesale cost will be about $900 monthly, the AP/Washington Post reports (Neergaard, AP/Washington Post, 8/6).

Helmut Albrecht, director of the University of South Carolina's Division of Infectious Diseases who was not involved with any maraviroc trials, said he was "cautiously optimistic" about the drug. He added, "It's so completely new that it is sort of difficult to see how well this is going to do over time." The last new class of antiretrovirals was approved by FDA in 2003.

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