Microbicides progressing well in fight against HIV

The development of new microbicides to protect against HIV infection is progressing steadily with promising options in the pipeline, researchers reported today at the M2010 Microbicides conference in Pittsburgh, in the US.

Microbicides are substances, like gels or creams, designed to stop HIV or other sexually-transmitted infections when applied topically inside the vagina or rectum.

Advances in this field since the last conference in India two years ago include:

• the completion of a human clinical trial testing the first microbicide using an antiretroviral agent (tenofovir) in South Africa, with the results to be released in July;

• the testing of products combining two antiretroviral drugs in the laboratory;

• new classes of antiretroviral drugs being tested in the lab and animals; and

• new ways of delivering the drug into the vagina including a flexible ring, tablet or thin film.

“We have moved beyond gels in a big and meaningful way,” said Dr Joseph Romano from the International Partnership for Microbicides. “This is a big, big difference from a few years ago when we were focused primarily on gels.

“We need to give women options and we know from the contraceptive field that not every dosage form is acceptable.”

“Laboratory testing on small, intravaginal rings combining two antiretroviral drugs (dapivirine and maraviroc) has shown that they can deliver protection for as long as a month after insertion, said Dr Mark Mitchnick from Particle Sciences.

He indicated this was in the last round of pre-clinical testing and would be ready for human trials in about a year.

Forty percent of drug products sold are in tablet form said Dr Sanjay Gorg from the University of Auckland, explaining why tablet microbicides could be a useful.

He said testing of microbicides in tablet form - which look like an almond and containing the two drugs dapivirine and DS003 - found they were stable and could deliver the drugs for a period of time.

Dr Anthony Ham from ImQuest BioSciences spoke about a quick dissolving film – like a piece of cellotape that disintegrates and leaves behind a gel-like mask – that is being developed.

“You can load various amounts of microbicide agents onto film,” he said, reporting they were quickly released – about 40% of the drug in eight hours.

“Film development is a unique challenge. The size, shape, colour and texture (need to be acceptable).”