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Women who used the gel were 30 percent less likely to become infected with the virus than those using no gel or an unmedicated product, said Salim Abdool Karim, a Columbia University researcher who presented the study today at an AIDS meeting in Montreal. While the finding didn’t pass a test for statistical significance, it should spur further examination of Lexington, Massachusetts-based Indevus’s product, he said.

After years of frustration, prevention researchers said they’re making headway reducing 2.7 million annual new infections with the AIDS virus. Other studies presented today at the AIDS conference suggested that gels or pills containing Gilead Sciences Inc.’s drugs, now used to treat people already infected, might also protect against the virus.

“It’s very exciting that PRO 2000 might have a positive effect,” said Karim, referring to the Indevus gel, in an interview at the Conference on Retroviruses and Opportunistic Infections. “Now we need a trial that’s big enough to show whether this is a statistically significant effect.”

Another study of PRO 2000 is being conducted by the London- based Medical Research Council. The study includes about 9,500 women, three times the size of Karim’s study.

High Drama

“A positive signal from this trial increases the anticipation of those from the next,” said Mitchell Warren, executive director of the AIDS Vaccine Advocacy Coalition in New York. “There’s a lot riding on it.”

Sexual gels, called microbicides, are key to preventing the human immunodeficiency virus, or HIV, in African women, Karim said. The women are often infected by their husbands or steady sexual partners, said Karim, who is also pro vice-chancellor of the University of KwaZulu Natal in South Africa.

“I have nothing to offer a woman who asks me how to prevent HIV,” he said. “I can’t tell her to be faithful, because she is. I can’t tell her to be abstinent or use condoms, because she wants to have her husband’s children.”

Most new cases of HIV are spread through sexual intercourse or contact with infected blood or tissue, according to UNAIDS, the New York-based agency that coordinates the United Nations’ response to the disease. While condoms can block contact with infected semen and blood, many couples and sex workers don’t use them consistently, Warren said. Microbicides in gels have an advantage because they can be applied discreetly and allow intimate contact, Warren said.

Dashed Hopes

Previous failures of gels, pills and other products have hurt hopes for preventing the spread of HIV in Africa. Karim, who has been working with microbicides for 15 years, was part of a team of researchers testing a spermicide called nonoxynol-9 in women. He was shocked when the trial was stopped early in 2000 because the gel raised women’s risk of infection.

Indevus’s product contains a negatively charged molecule. Researchers believe the charge attracts positively charged portions of HIV, preventing the virus from infecting cells, Karim said.

Another vaginal product, BufferGel from ReProtect Inc. in Baltimore, was tested in the same study. It had no effect on HIV transmission, Karim said at a press conference today.

U.S. government research presented at the conference also suggested that Gilead’s Viread and Truvada, used in gels or in oral pills, might prevent the spread of HIV, said scientists studying a monkey equivalent of the disease.

Monkey AIDS

In one test, animals treated with a gel containing Viread were completely protected from SHIV, an animal version of the AIDS virus, U.S. Centers for Disease Control and Prevention scientists said today at the conference in Montreal. The single- drug gel was just as protective as a gel containing two-drug Truvada, said Walid Heneine, laboratory chief of CDC’s division of HIV/AIDS prevention, who led the study.

“This is very promising, although we’re waiting for the results of human trials to see if they correlate with animal studies,” Heneine said in an interview.

The second trial measured how oral doses of Truvada, a combination of two Gilead drugs, would affect monkeys exposed to HIV through the rectum.

Almost all untreated monkeys were quickly infected after being exposed to the virus twice. Two doses of Truvada, one before and another after rectal exposure, protected most monkeys from infection, said Gerardo Garcia-Lerma, a CDC senior scientist in the HIV/AIDS prevention division.

Pre-Sex Drug

The study also suggests that people might be able to use the drugs when they know they’re going to have sex, rather than daily. A gel or pill containing Gilead’s drugs that people could use before sex might slow the spread of the disease, which now infects about 32 million people, most of them in Africa, AVAC’s Warren said.

“It’s very exciting,” he said in an interview. “Like any animal research we need to see if it correlates with human experimentation. We’ve certainly seen in the vaccine field that we mustn’t be too optimistic that we’ll see the same results in people.”

At least seven human studies are now looking at whether giving high-risk people oral doses of Gilead’s Viread or Truvada can safely prevent transmission.

“It’s important to support the ongoing and planned prevention studies, particularly given the impact of HIV in developing countries,” said Amy Flood, a Gilead spokeswoman, in an e-mail. Gilead is providing its drugs free of charge for these trials, she said.