Tests of drug to block HIV infection are halted over safety

By LAWRENCE K. ALTMAN, The New York Times

Efforts to develop a topical microbicide to prevent H.I.V. infection during sex suffered a surprising setback yesterday when researchers announced that they had stopped two full-scale trials for safety reasons.

The trials, in Africa and India, involved a chemical, cellulose sulfate or Ushercell, and were the second failure of a potential microbicide in a full-scale trial in recent years. In one of the latest trials, a standard check by an independent scientific committee found an increased risk of H.I.V. infection among women who used cellulose sulfate compared with those who used a placebo gel.

In 2000, a large full-scale trial showed that the only other microbicide candidate, nonoxynol-9, was unsafe when it had been expected to be effective. Subjects in that trial developed a higher incidence of H.I.V. infection, presumably through ulcers caused by chemical irritation.

Yesterday, AIDS researchers at the World Health Organization, the United Nations AIDS program and other organizations expressed hope that at least one of three other potential microbicides undergoing full-scale testing would prove to be safe and effective. The others are Pro 2000 by Indevus Pharmaceuticals, BufferGel by ReProtect and Carraguard, whose trademark is held by the Population Council.

“While the closing of these trials is a profound disappointment for the microbicide field, we cannot let it paralyze us,” said Dr. Zeda Rosenberg, chief executive of the nonprofit International Partnership for Microbicides in Silver Spring, Md.

In the absence of an AIDS vaccine, specialists say development of a microbicide is a public health priority, mainly to protect the many women in poor countries whose partners refuse to use condoms. Such protection could take the form of a gel, cream, film, tablet or sponge that could be inserted into the vagina or rectum.

The study that led to stopping the trials involved 1,333 participants in Benin, South Africa and Uganda. Conrad, a health research organization in Arlington, Va., conducted the study.

Conrad said the independent committee found more new H.I.V. infections among those who used cellulose sulfate than among those who used an inactive gel, but did not report any numbers. Final numbers are expected in March, a spokeswoman for Conrad said.

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http://www.nytimes.com/2007/02/01/health/01aids.html?ref=world