Taking an important step toward the development of a product to prevent HIV infections associated with unprotected anal sex, researchers today announced the launch of a global Phase II clinical trial of a potential rectal microbicide. The trial, led by the U.S. National Institutes of Health (NIH)-funded Microbicide Trials Network (MTN), is testing the rectal use of a reduced glycerin gel formulation of the antiretroviral drug tenofovir.
"As the HIV epidemic continues to impact people worldwide, we urgently need new ways to prevent sexual transmission of the virus, especially from unprotected anal sex - the highest risk sexual behavior for HIV acquisition," said Ross D. Cranston, M.D., of the University of Pittsburgh School of Medicine, who is leading the study with Javier R. Lama, M.D., M.P.H., of IMPACTA in Lima, Peru. "Rectal microbicides, gel-based antiretroviral products applied into the rectum, are being developed for use by both men and women to help reduce this risk."
Known as MTN-017, the Phase II study will enroll 186 HIV-negative men who have sex with men (MSM) and transgender women in Peru, South Africa, Thailand and the United States, including Puerto Rico, to assess the safety of a reduced glycerin gel formulation of tenofovir, its acceptability to participants, and how much of the drug is absorbed into the body. It is a follow-up trial to an earlier study, MTN-007, which found that the reduced glycerin gel was safe and acceptable to both men and women who used it in the rectum daily for a one-week period.
During MTN-017, study participants will cycle through three study regimens, each lasting eight weeks: reduced glycerin tenofovir gel used daily, reduced glycerin tenofovir gel used before and after anal sex, and daily use of the antiretroviral tablet Truvada- (emtricitabine/tenofovir disoproxil fumarate), developed by Gilead Sciences, Inc. This design will allow researchers to collect information about the gel's safety and acceptability in the rectum, and compare it to the use of oral Truvada, which was approved for use as HIV prevention by the U.S. Food and Drug Administration in 2012. Truvada was approved for the treatment of HIV infection in combination with other antiretrovirals in 2004.
"The results of MTN-017 will be vitally important to the biomedical HIV prevention field," explained Dr. Lama. "They will determine whether we can move ahead with further testing of the gel's effectiveness in preventing the transmission of HIV from unprotected anal sex. We know that rectal microbicides will never replace condoms, but if found safe and effective, they could provide an additional tool to help reduce HIV risk."
Throughout the study, researchers will regularly test participants' blood to assess the presence of drug - a determinant of whether they are using their assigned study products. Testing will be conducted every four weeks and results will then be shared with participants as part of their counseling sessions on product use.
"By monitoring product use as the study is underway, we will have a much better sense of whether participants are adhering to the assigned study regimens," said Ian McGowan, M.D., Ph.D., co-principal investigator of the MTN and professor of medicine, University of Pittsburgh School of Medicine. "The unique design of our study, which does not include a placebo, allows us to address any concerns or issues with adherence in a more real-time fashion, rather than waiting until after the study has concluded."