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[CAPE TOWN] A vaginal ring containing an antiviral drug is being tested in Africa and, if successful, could provide women with an easy-to-use alternative to vaginal microbicides to help reduce their risk of HIV infection.

The ring, which slowly releases the antiretroviral drug dapivirine over a period of time — removing the need for application each time a woman has sexual intercourse — has entered phase III efficacy trials in South Africa.

Pending regulatory and ethics approvals, the study will expand into additional sites in Malawi and Rwanda in the next few months, with the first safety and efficacy results expected in 2015.

The road to a successful vaginal microbicide gel has been paved with disappointments. In July 2010, South African researchers announced that a trial in KwaZulu-Natal, of the gel CAPRISA 004, had proved 39 per cent effective in reducing HIV transmission.

But in November 2011, a trial of the gel in South Africa, Uganda and Zimbabwe was stopped, when early data showed that it failed to reduce HIV infection.

However, effectiveness is not the only issue. "One of the greatest challenges with microbicide research to date has been adherence," said Mitzy Gafos, social scientist at the MRC Clinical Trials Unit in London, United Kingdom.

"A slow-release vaginal ring that women insert for a month at a time may overcome many of the adherence challenges that some women face with the use of vaginal gels, which need to be inserted before sex or on a daily basis," said Gafos.

Zeda Rosenberg, founder and chief executive officer of the International Partnership for Microbicides (IPM) programme, that developed the ring and is running the trials, said that IPM acquired dapivirine through a royalty-free licensing agreement from Janssen Pharmaceuticals. The agreement allows the development of dapivirine as a vaginal ring for HIV prevention and its distribution to women in developing countries, once proven safe and effective. 

Rosenberg said that IPM is working to produce dapivirine rings at the lowest possible cost. They are also "working on developing longer-acting options such as a 60- or 90-day ring, which could potentially lower the overall cost".

In a separate study, the Microbicide Trials Network (MTN) will soon begin testing the same ring in a sample of nearly 3,500 women in southern Africa.

Sharon Hillier, principal investigator of the MTN, has said in a media statement that "sustained delivery of antiretrovirals in a vaginal ring could be a game-changer for prevention of HIV in women".