Microbicides preventing HIV infection could be available by 2010
First generation topical microbicides aimed at preventing HIV infection in women could be available as early as 2010, researchers told participants at the Microbicides Conference 2004 held in London on 2831 March.
About 60 of these drugs in the form of creams, gels, sponges or pessaries, designed to prevent the sexual spread of HIV, are currently under development. Of those, 18 are at clinical trial stage including six that are due to enter large-scale phase III trials in the second half of this year. Topical microbicides work by forming a protective coating around mucosal cells that either kills or inactivates HIV reducing the risk of vaginal or anal transmission.
"Even if the products are as low as 40% effective which means they would bring about a reduction of 40% in the HIV transmission rate they could still have a major impact on public health," said Professor Janet Darbyshire of the UK's Medical Research Council and co-chair at the conference. "However we hope that they will be considerably more effective certainly some of the 'second generation' products in the pipeline look very promising."
Research from the London School of Hygiene and Tropical Medicine showed recently that some 2.5 million new cases of HIV infection globally could be prevented in just three years even if the microbicide only brought about a reduction of 60% in the HIV transmission rate (BMJ 2004;328:305).
In the absence of an effective vaccine, increasing attention is being paid to the development of microbicides. According to a recent commentary in the UK-based medical journal, the Lancet (2004;363:1002-3), in many developing countries, AIDS is taking a disproportionate toll on women. Biologically, women may be up to four times more vulnerable to HIV infection. The need for a discreet female-controlled method for the prevention of HIV-infection is further affirmed by the lack of economic and social power preventing many women from negotiating safe sex.
"The development of a safe, effective microbicide would be the biggest innovation in women's reproductive health since the introduction of the [contraceptive] pill," said Lore Heise, Director of the Global Campaign for Microbicides.
Stephen Lewis, the United Nations envoy on AIDS, told the conference that the numbers of infected women had grown exponentially, so that virtually half the infections in the world were amongst women. In Africa the rate was 58%, rising to 67% between the ages of 15 and 24, he said.
"This is a cataclysm, plain and simple. We are depopulating parts of the continent of its women," Lewis said.
Like vaccines which are also at clinical trial stage, microbicides may succeed where safe sex campaigns promoting condom use and abstinence have failed to change sexual behaviour, with devastating consequences.
One of the first microbicide products likely to come on the market in the next 5 to 10 years is TMC-120 produced by US pharmaceuticals giant, Johnson & Johnson. The US company told the conference it would grant royalty-free rights to this promising new drug to the US-based non-profit organization, the International Partnership for Microbicides.
The drug, originally developed as an antiretroviral by Johnson & Johnson's Belgian subsidiary, Tibotec Pharmaceuticals, has since been developed into a gel for use particularly in resource-poor countries and has already undergone early stage clinical trials. Under the agreement, the International Partnership for Microbicides will conduct the remaining trials necessary for regulatory approval, which could cost between US$ 50 million and US$ 100 million.
Other products entering phase III trials include dextrin sulfate, from the UK firm, ML Laboratories; PRO-2000 gel, a synthetic naphthalene sulfonate polymer from the US company Indevus Pharmaceuticals; cellulose sulfate from CONRAD, a partnership between the Eastern Virginia Medical School in the US and the US Agency for International Aid (USAID); Carraguard from the Population Council, an international non-profit organization; BufferGel from the HIV Prevention Trials Network (HPTN), a worldwide collaborative clinical trials network, and a vaginal gel known as C31G, developed by US pharmaceuticals company, Biosyn Inc.