BEIJING, April 23 (Xinhuanet) -- A new HIV drug by Pfizer faces safety concerns by U.S. government regulators at a meeting next week, and if approved, would be the first in a new class of drugs to treat the virus that causes AIDS.

    The Food and Drug Administration will ask a panel of outside experts whether risks of cancer and infection are serious enough to limit Pfizer's ability to market Maraviroc, a twice-a-day pill designed to fight HIV. The panel is scheduled to vote Tuesday on whether the drug should be approved.

    The FDA is not required to follow the experts' recommendation, but it often does.

    Maraviroc is in a class of drugs called CCR5 antagonists, which block HIV from entering white blood cells through a pathway present in the majority of patients who carry the virus.

    Pfizer did not uncover any cancerous side effects while testing its drug on patients, but similar studies by other companies have raised safety concerns.

    British drug maker GlaxoSmithKline plc decided to scrap its drug aplaviroc in 2005 after signs of liver damage appeared in some patients.

    (Agencies)