WASHINGTON, Jan 30 (Reuters) - Researchers dedicated to finding a gel or cream that could work invisibly to protect women from AIDS the way a condom does said on Wednesday they got permission from Pfizer Inc. <PFE.N> to use its newest HIV drug.

The International Partnership for Microbicides said Pfizer gave it a royalty-free license to try to develop maraviroc in a cream or gel for the prevention of HIV infection.

Maraviroc, a pill sold under the brand names of Selzentry and Celsentri, is one of a new class of HIV drugs called CCR5 blockers, which prevents the virus from getting into the cells it infects.

"This agreement adds a promising new compound to IPM's pipeline, allowing us to explore new ways to prevent HIV infection," Dr. Zeda Rosenberg, chief executive officer of the group, said in a statement.

Microbicides are products, such as gels or creams, that could be applied vaginally or anally to prevent transmission of the human immunodeficiency virus that causes AIDS.

So far, attempts to create a microbicide have failed.

Under this agreement, IPM may develop, manufacture and distribute a maraviroc-based microbicide in developing countries without paying a royalty.

"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," said Pfizer Vice President Dr. Jack Watters.

The AIDS virus infects 33 million people globally, according to the World Health Organization. It has killed 25 million, and there is no vaccine to prevent the fatal and incurable virus.

Condoms can protect men and women, but health experts note that many men refuse to use them. In many countries, a women who demands that her husband or partner use a condom can face refusal or even a beating.

According to the United Nations, in sub-Saharan Africa almost 61 percent of adults infected with HIV are women.

"Women in the developing world are especially vulnerable to HIV, and urgently need new ways to protect themselves," said Dr. Tachi Yamada, president of the Bill & Melinda Gates Foundation's Global Health Program.

"For Pfizer to offer one of its most important new drugs to benefit the poorest of the poor shows a special act of commitment. I hope their example will point the way for other companies to consider how they can address major global health challenges as well."

The microbicides group also has an agreements with Johnson & Johnson <JNJ.N> subsidiary Tibotec Pharmaceuticals Ltd., Merck & Co. <MRK.N>, Bristol-Myers Squibb <BMY.N> and Gilead Sciences Inc. <GILD.O> to develop some of their HIV drugs.

(Reporting by Maggie Fox, editing by Will Dunham and Cynthia Osterman)

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