New research in monkeys suggests a combination of AIDS drugs applied as a vaginal gel might prevent infection with HIV, and two major drug companies said Monday they would license promising compounds at no charge so that such a product can be created.

A paper due for publication this week in the journal Nature found that a combination of three drugs applied topically in monkeys prevented infection with a virus similar to the human immunodeficiency virus, which causes AIDS. The results are among the most promising to date in tests of this approach and point toward a prevention strategy that could save many lives.

The International Partnership for Microbicides, a Silver Spring group working to bring a preventive gel to women at risk of AIDS in poor countries, said Monday it had struck deals with Merck & Co. and with Bristol-Myers Squibb Co. The contracts give the group, funded by foundations, the right to create a combination gel using drugs from a promising new category known as HIV entry inhibitors. They block the entry of the virus into human cells, and such compounds are already under development as pills for infected people.

The initial deal, announced on the eve of a global-health summit here, involves three drugs created by Merck and one created by Bristol-Myers Squibb. Both companies said they might offer the partnership additional compounds in the future. The partnership had previously struck an arrangement with a subsidiary of Johnson & Johnson for a different type of AIDS drug, and it is pursuing deals with still more companies.

"These three companies really are, I think, setting a trend," said Mark Mitchnick, chief scientific officer with the Silver Spring partnership. "There's a real momentum building."

The deals put the group in a position to pick and choose from a promising menu of drugs. Scientists at the partnership hope to create a safe but powerful combination product that a woman could apply as long as several hours before sex, with or without the knowledge of her partner.

Human tests of several vaginal gels are underway, but they generally involve a single active ingredient, usually a general-purpose microbicide not specifically designed to target HIV. Recent research suggests combination gels, using HIV-specific drugs, may offer greater promise. But large tests will be needed, so the earliest such a gel might be available is 2010.

The focus is on poor countries, in part because the virus is still spreading there despite programs emphasizing abstinence, marital fidelity or condom use. The International Partnership for Microbicides said in a statement that women are "often powerless to abstain from sex or to insist on condom use." A successful gel may well be marketed in rich countries, too.

The partnership is one of many entities, many based in the Washington area, that seek to solve health problems in poor countries by promoting creative deals between public health groups and private businesses. The International Partnership for Microbicides was created three years ago and is funded by the Rockefeller Foundation, the Bill and Melinda Gates Foundation, the World Bank and several governments, including that of the United States. (Melinda Gates is a Washington Post Co. board member.)

The plan announced Monday builds on recent scientific work aimed at creating new preventive tools.

In a paper due for publication in Nature on Thursday, Cornell University researcher John P. Moore and his colleagues tested three anti-HIV drugs as vaginal gels. The drugs worked as single agents, protecting 21 of 28 monkeys from infection with a virus that closely resembles HIV. But they appeared to work better in combination: A three-drug gel completely blocked infection in three monkeys.

It is unlikely that the exact combination used in Moore's research, which included drugs from Merck and Bristol, will go into human trials. Scientists intend to tweak the regimen to improve its effectiveness and keep the cost low, and they are seeking arrangements with additional drug companies to find the ideal mix of ingredients.

In the past, many drugs have moved to poor countries only after many years on the market in rich countries. The compounds Merck and Bristol licensed Monday are still in the early stages of scientific study. The deals show an increasing willingness on the part of major drug companies to see their research applied quickly to help AIDS victims in the poorest countries.

The pharmaceutical industry came under heavy criticism in the late 1990s for doing so little to fight AIDS deaths in Africa. In recent years the companies have been going out of their way to be helpful. Helene Gayle, a senior officer at the Gates Foundation overseeing programs on AIDS, tuberculosis and malaria, praised Merck and Bristol on Monday.

"I really hope that other pharmaceutical companies will follow their lead," she said in a conference call.