Pfizer announced today that it is offering the International Partnership for Microbicides (IPM) a royalty-free license to develop the antiretroviral drug Selzentry (maraviroc) as a microbicide to prevent HIV transmission.

Selzentry, an HIV entry inhibitor, is currently approved to treat HIV-positive people who have tried and failed other antiretroviral drugs.

For HIV to infect an immune system cell, it must first attach to collections of proteins, known as receptors, on the surface of the cell. One of the key receptors on CD4 cells is called CCR5, and Selzentry works by binding to the CCR5 receptors on a person’s CD4 cells and thus blocks entry of the virus.

Researchers hope that Selzentry may also work to stop transmission of HIV if used as a microbicide, which is typically a gel, film or slow-release device that can be put into the vagina or anus before sex.

Jack Watters, MD, a vice president at Pfizer says, “Given maraviroc's mechanism of action blocking entry of HIV into the CD4 cells, the possibility for use in a microbicide is exciting. In addition to developing new drugs to treat AIDS, we are committed to searching for ways our drugs can be used to slow down or stop this epidemic.”

IPM has similar licensing agreements with a number of other pharmaceutical companies, which would allow them to develop other promising compounds as microbicides