Millions of people around the world could soon protect themselves against HIV using a simple gel or cream.
Around 40m worldwide have HIV
Experts say around 60 microbicides are now in development with about 14 in clinical trials.
The gels or creams are applied internally and aim to stop the virus from entering the body.
Speaking ahead of a major conference on microbicides next week, experts said the gels could transform the fight against HIV.
An estimated 40m people around the world are HIV positive. Many of these may have contracted the virus because they were unable to protect themselves.
For instance, women in developing countries, in particular, are often unable to persuade their partner to wear a condom.
Experts believe a gel or cream could make it much easier for them to protect themselves.
They estimate that even if microbicides are only partially effective they could help to prevent millions of new infections.
The microbicides work in one of three ways - by killing the virus before it enters the body; by preventing it from taking hold once inside the body; or by creating a barrier to stop it from entering the body in the first place.
"Microbicides have the potential to give many women in developing countries the power, for the first time, to control their risk of contracting HIV and other sexually transmitted diseases," said Hilary Benn, the UK's international development secretary.
"The simple application of a microbicide in the form of a cream or gel could make a huge difference to the lives of millions of poor women around the world."
The UK's Medical Research Council and Imperial College London will shortly launch final trials of two potential microbicides.
A total of 12,000 women are expected to take part in the three-year trials to
be held in South Africa, Zambia, Tanzania, Uganda and Cameroon.
If the results are positive, the products could be on the market before the end of the decade.
Professor Janet Darbyshire, director of its clinical trials unit, said if proven to work they could save the lives of millions of people.
"There is an overwhelming need for new ways to tackle the global HIV pandemic and an effective microbicide would have the potential to greatly reduce the numbers of those who die from Aids, especially if used along with condoms."
Jonathan Weber, professor in genito-urinary medicine and communicable diseases at Imperial College London, backed that view.
"We desperately need new methods to prevent HIV transmission in the face of rising prevalence of infection globally.
"As we have still not been able to develop an effective HIV vaccine, vaginal microbicides are now the most promising bio-medical intervention for the prevention of HIV infection on the horizon."
Jo Robinson, a senior specialist in health promotion at the Terrence Higgins
Trust charity, said: "These products are still being trialled, but certainly if
they do come through they will have a large impact on the epidemic."
London hosts a major conference on microbicide from 28 to 31 March.