A Food and Drug Administration panel Thursday backed the use of Pfizer Inc.'s (PFE) HIV drug Selzentry as part of a first-line treatment regimen for newly diagnosed patients.

Selzentry is currently approved for use to treat HIV in patients who have failed other medications, but Pfizer is seeking FDA approval to use the product in people who haven't been previously treated with other drugs.

The FDA brought the issue to an outside panel of medical experts who serve on the agency's antiviral-drugs advisory committee for review. The panel voted 10 to 4 in favor of a question that asked if the safety, effectiveness and resistance data supported approval of Selzentry "treatment-naive" patients who have a specific type of HIV infection.

Selzentry was first approved in August 2007. The drug works by inhibiting a pathway that HIV uses to infect cells rather than treating the virus itself. Selzentry blocks a receptor known as CCR5 to prevent HIV infection. However, in some patients, HIV uses another receptor known as CXCR4 to enter cells, meaning Selzentry wouldn't work in those cases.

An FDA staff review of Selzentry said the drug "appeared to be well-tolerated, ... with relatively few patients discontinuing for adverse events." The agency also said no new safety signals were found during a post-marketing review of the drug, although the review noted there was a "relative increase" of resistance developing to Selzentry compared with patients taking another HIV drug, efavirenz.

Over time, most HIV viruses mutate and stop responding to the drugs. The Centers for Disease Control and Prevention estimates that about 1.1 million Americans have HIV. HIV is the virus that causes AIDS. Patients with HIV are typically treated with a "cocktail" of two or three types of drugs.

James Neaton, a biostatistics professor at the University of Minnesota, voted against earlier use of Selzentry over concerns that the drug didn't appear to be more effective than efavirenz at suppressing a patient's viral load or detectable HIV levels. Other panel members were concerned patients could develop resistance to that drug or other drugs sooner if used in a first-line setting.

The panel members who supported earlier use of Selzentry said it should be an option for doctors to consider, but not necessarily the first choice for newly diagnosed patients. They said the product appears to be better-tolerated than many other HIV treatments.

-By Jennifer Corbett Dooren, Dow Jones Newswires; 202-862-9294; jennifer.corbett@dowjones.com