MICROBICIDE TRIAL HALTED AFTER INCREASED HIV RISK SEEN

Polydex Pharmaceuticals and Conrad, a reproductive health research organization, have halted a Phase III clinical trial of Ushercell -- a cellulose sulfate topical microbicide gel being tested for HIV prevention in women -- because preliminary results at some trial sites indicated that cellulose sulfate could lead to potential increased risk of HIV infection in women who use the compound. The trial was being conducted at several sites in Africa, including South Africa, Benin and Uganda.

Additionally, Family Health International has halted a second Phase III cellulose sulfate trial in Nigeria. Although investigators did not detect an increased HIV risk associated with cellulose sulfate, the decision was made as a precautionary measure. Ushercell is one of four microbicides being tested in effectiveness trials for prevention of HIV and other sexually transmitted infections.

The Conrad study began in July 2005. Half of the participating women were given Ushercell, and half a placebo gel, in a double-blind, randomized trial. All participants received HIV prevention counseling and free condoms. Participants received regular testing and treatment for sexually transmitted infections.

"At present there is no explanation for this higher rate of transmission of HIV," the World Health Organization said in a statement. "This is a disappointing and unexpected setback in the search for a safe and effective microbicide that can be used by women to protect themselves against HIV infection."

"The closure of this trial is a stark reminder that drug development in general is a difficult and unpredictable process, and we must constantly bear in mind that the majority of drugs that enter the clinical trial process fail. This is especially true for first-in-class drugs like microbicides," the International Partnership for Microbicides said in a statement.