NIAID supports research to develop microbicides, products that could be inserted into the vagina or rectum to safely block sexual transmission of HIV. A microbicide would deliver an anti-HIV agent to the mucus membranes lining the surface of the vagina or rectum through a substance such as a gel, intravaginal ring, film, tablet, suppository, enema, or foam. Importantly, a microbicide must be appealing to use and easily integrated into the lifestyles of people at risk for HIV infection regardless of age, sex, or gender.
The ideal microbicide would be inexpensive, desirable, long-acting, easy to use and store, protective against both HIV and other sexually transmitted infections, and available in contraceptive and non-contraceptive forms.
Since women and girls are at particularly high risk for HIV/AIDS in many parts of the world, it is especially important to have an effective, desirable vaginal microbicide as an HIV prevention tool that women control. AIDS is the leading cause of death for reproductive-age women in low- and middle-income countries.
NIAID supports all phases of microbicide research, from basic research to animal studies to clinical trials, many of which are conducted by the NIAID-funded Microbicide Trials Network (MTN). Also funding the MTN are the Eunice Kennedy Shriver National Institute of Child Health and Human Development and the National Institute of Mental Health, both part of NIH.
The most promising NIAID-funded microbicide clinical trial to-date is the ASPIRE trial, also known as MTN-020. This large, multinational study was designed to test the effectiveness and extended safety of a drug-infused vaginal ring for preventing HIV infection in women. The study aimed to determine whether the experimental antiretroviral drug dapivirine could safely and effectively prevent HIV infection when continuously released in the vagina from a silicone ring replaced once every 4 weeks. In February 2016, the ASPIRE investigators reported that the dapivirine ring safely reduced the risk of HIV infection by 27 percent in the study population overall and by 61 percent in women ages 25 and older, but provided no statistically significant protection in women younger than 25 years.
Subsequently, investigators performed exploratory, post-hoc analyses of data from the ASPIRE study to better understand the degree of protection the dapivirine ring could provide if used consistently. They found that adherence to the ring was associated with a reduction in risk of HIV infection of at least 56 percent, and high adherence was associated with a risk reduction of potentially 75 percent or more.
To build on the ASPIRE results, NIAID is funding an open-label extension study of the dapivirine ring in which all participants are invited to use the ring for HIV prevention. The new study, known as the HIV Open-Label Prevention Extension (HOPE) or MTN-025, will gather additional data on the safety and acceptability of the dapivirine ring and participants’ adherence to it. In addition, NIAID is funding a separate study to evaluate why the dapivirine ring did not protect the youngest women enrolled in ASPIRE. Known as MTN-034, the study will seek to determine whether the ring was ineffective for women ages 18 to 25 years due to behavioral issues or because there is something biologically different about these women that counteracts the ring’s protective properties.