More evidence needed to determine the gel’s effectiveness 9th February 2009: A trial involving more than 3,000 women in Africa and the US has demonstrated for the first time the promise of a vaginal microbicide gel for preventing HIV infection in women.
The findings presented today at the Conference on Retroviruses and Opportunistic Infections (CROI), show that PRO 2000 gel (0.5 percent dose) was 30 percent effective.
While encouraged by the results, the researchers who conducted the study, known as HPTN 035, say that additional evidence is needed to determine more definitively the effectiveness of PRO 2000.
“These findings provide the first signal that a microbicide gel may be able to prevent women from HIV infection. Indeed, for the millions women at risk for HIV, especially young women in Africa, there is now a glimmer of hope. But these findings also indicate that more research is needed; we can’t yet say that we have an effective microbicide,” said Dr. Salim Abdool Karim of the Center for the AIDS Program of Research in South Africa.
Dr. Abdool Karim led the multi-center study for the U.S.-based Microbicide Trials Network (MTN).
Microbicides are substances intended to reduce or prevent the sexual transmission of HIV and other sexually transmitted infections when applied topically inside of the vagina or rectum. A microbicide can be formulated in many ways, such as a gel or cream or in a vaginal ring. Several candidate microbicides are being tested in clinical trials, although none is yet approved or available for use. Earlier trials have yielded disappointing results or were stopped prematurely.
Currently, women comprise half of all people worldwide living with HIV. In sub-Saharan Africa, women represent nearly 60 percent of adults living with HIV, and in several southern African countries young women are at least three times more likely to be HIV-positive than young men. In most cases, women become infected with HIV through sexual intercourse with an infected male partner. Although correct and consistent use of male condoms has been shown to prevent HIV infection, women often cannot negotiate condom use with their male partners. An effective microbicide could provide women with an HIV prevention method they initiate.
The study was conducted between February 2005 and September 2008 and involved 3,099 women at six sites in Africa and one in the United States. In Africa, the sites were located in Durban and Hlabisa, KwaZulu-Natal, South Africa; Harare, Zimbabwe; Lusaka, Zambia; Blantyre, Malawi; and Lilongwe, Malawi. The U.S. site was in Philadelphia.
Women in the study were randomly assigned in approximately equal numbers to one of four groups: those who used BufferGel prior to engaging in sexual intercourse; those who used PRO 2000 before each sex act; those who used placebo gel (with no active ingredient) prior to sexual activity; and those who used no gel. Women took part in the study for an average of 20 months and were evaluated monthly.
All participants received detailed information about the possible risks and benefits of trial participation prior to enrollment and were monitored closely throughout the study. In addition, all participants were counseled on safe sex practices, provided with condoms, and tested and treated for sexually transmitted infections throughout the study.
During the course of the study, 194 women acquired HIV. Of this total, 36 HIV infections occurred among participants who used PRO 2000, while 54 infections occurred among participants who used BufferGel, 51 infections occurred among participants who used placebo gel, and 53 infections occurred among participants who used no gel.
Using these data as a basis for determining the effectiveness of the two candidate microbicides, the researchers found that BufferGel had no effect on HIV infection and that PRO 2000 had a 30 percent level of effectiveness in preventing HIV infection. Both gels were found to be safe.
Past microbicides trials raised the possibility that the placebo gel may also have some effect on HIV.
The finding in the HPTN 035 trial that the number of HIV infections in the two control arms – placebo gel and no gel – was similar provides useful evidence that the placebo gel has no impact on HIV infection, reported Dr. Abdool Karim.
“I am humbled by the dedication and commitment of the women who participate in microbicide studies, but I am particularly impressed by and grateful to the women who took part in HPTN 035. We have reached an important milestone in HIV prevention research, and these women deserve credit for the success of the study,” commented Sharon Hillier, Ph.D., vice chairman and professor, department of obstetrics and gynecology and reproductive sciences at the University of Pittsburgh School of Medicine, and MTN principal investigator.