Some scientists consider this a setback because microbicidal gels, creams or suppositories are seen as a cheap way to prevent the spread of AIDS in poor countries, especially in women whose partners refuse to use condoms.

Cellulose sulphate was developed as an anti-HIV microbicide by Polydex Pharmaceuticals of Toronto and its trials were being conducted across the world by Conrad, a health-research group based in Virginia.

According to Conrad, the independent committee had found, in a small study of its own, that more women using cellulose sulphate developed HIV than those using a placebo, or inactive gel.

In India, the Conrad trials were being implemented by YRG Care, Chennai, and St John’s Medical College, Bangalore.

“We were told to stop the trial on January 27,” said Dr Reynold Washington, a professor at St John’s who is the principal investigator for the trial in Bagalkot district of Karnataka. “Yes, it’s a great setback as microbicides are being perceived as a new tool to prevent HIV.”

Dr Washington said it took a long time to find and enrol participants and counsel them.

“We had enrolled 20-25 women who were HIV negative and the trial had only begun as the government had given clearance only last year,” he said. “We have not had any sero-conversions, which means those who are HIV negative have not turned positive.”

However, he said his team had learnt valuable lessons in setting up trials, managing data, building confidence among participants, and adhering to good clinical practices.

For Dr Suniti Solomon, Director of YRG Care, Chennai, too the halt is a “huge disappointment.” YRG Care had enrolled 250 women, including sex workers who were not HIV positive.

“They (Conrad) had found problems at a site in Africa last year itself and had immediately told us to stop the trial here, in October last year,” Solomon said.

Like in the Bagalkot study, none of the participants in Chennai had contracted the HIV virus, said Solomon.

Scientists are particularly surprised at the calling-off of the trial for cellulose sulphate, because it had already reached Phase-III, after clearing multiple safety trials. In 2000, another microbicide on trial, nonoxynol-9, had been declared unsafe.

Trials continue, however, on two other microbicides, Pro 2000 of Indevus Pharma, and BufferGel of ReProtect and Carreguard, whose trademark is held by the Population Council.