30 January 2008Posted to the web 30 January 2008Science &...

30 January 2008
Posted to the web 30 January 2008


Science & Medicine

Pfizer To License Antiretroviral To IPM for Reformulation as Microbicide


[Jan 30, 2008]

Pfizer on Wednesday is expected to announce plans to license its new antiretroviral drug Selzentry to the International Partnership for Microbicides in an effort to prevent sexual transmission of HIV among women worldwide, the Wall Street Journal reports (Johnson, Wall Street Journal, 1/30). Microbicides include a range of products -- such as gels, films and sponges -- that could help prevent the sexual transmission of HIV and other infections (Kaiser Daily HIV/AIDS Report, 12/20/07).

Selzentry, known generically as maraviroc, belongs to a new class of antiretrovirals that could provide an alternative to HIV-positive people who have developed resistance to multiple drugs. The treatment 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. FDA approved Selzentry in August 2007 on the condition that the drug's label include a black box warning about an increased risk of heart attack. FDA also is requiring Pfizer to conduct further research into the drug's long-term side effects (Kaiser Daily HIV/AIDS Report, 9/25/07).

Jack Watters, Pfizer's vice president of external medical affairs, said he is optimistic about Selzentry's prospects as a preventive treatment but added that researchers are "a long way from proving that." Zeda Rosenberg, IPM's chief executive, said a topical formulation of the drug is preferred to daily pills because a lower dose of medicine gets into the bloodstream with topical application, increasing the safety for long-term use. The topical form also can be applied directly where HIV enters the body, she added.

According to the Journal, IPM "offers a low-risk way for Pfizer to find out if" Selzentry could "become a frequently taken drug, while potentially offering an empowering concept to women in the developing world." In addition, because the drug already has FDA approval, it could be easier to conduct tests of Selzentry in modified forms, the Journal reports. Selzentry also might be more appropriate for use as a microbicide than other antiretrovirals that block HIV-infected cells from replicating because it prevents the virus from infecting healthy cells (Wall Street Journal, 1/30).

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