A vaginal ring that continuously releases dapivirine, an experimental antiretroviral drug, provided a “modest” level of protection against HIV infection in a multisite clinical trial that involved more than 2,600 African women.
The ASPIRE study, also known as MTN-020, funded in part by the National Institute of Allergy and Infectious Diseases, began in 2012. Women received either the ring containing dapivirine or a placebo ring. The rings were replaced every 4 weeks.
The antiretroviral ring reduced the risk of HIV infection by 27% overall and by 61% among those who used the ring most consistently, women aged ≥ 25 years. When the researchers excluded data from 2 sites where many women did not return for study visits or use the ring consistently, the dapivirine ring reduced risk by 37%.
When the researchers performed further analyses, they found that the ring reduced the risk of infection by 56% in women older than 21 years but provided no significant protection for women aged 18 to 21. Younger women appeared to use the ring less consistently, based on the blood levels of dapivirine measured during study visits.
The rate of adverse events was similar among women in both groups, as was the frequency of antiretroviral resistance in women who acquired HIV.
In another ongoing large trial, which tested the dapivirine ring for safety and efficacy, researchers found an overall effectiveness of 31%, with a slightly greater reduction of risk in women older than 21.
The ASPIRE study is the first to demonstrate that a product that slowly releases the antiretroviral over time can offer partial protection from HIV.