According to a press release. in an open-label study of women in southern and eastern Africa, a vaginal ring that is inserted once a month and slowly releases an antiviral drug was estimated to reduce the risk of HIV by 39 percent, according to statistical modeling. In addition, the study found that participants appeared to use the ring more in the open-label study than in a previous clinical trial. These and other results of the HIV Open Label Extension (HOPE) study were presented at the 10th IAS Conference on HIV Science (IAS 2019) in Mexico City.
In 2017 alone, nearly 870,000 women and girls acquired HIV, according to UNAIDS. Currently available forms of HIV prevention for women are limited, and many women are unable to negotiate condom use with male sexual partners. The vaginal ring tested in the HOPE study, which continuously releases the anti-HIV drug dapivirine, was designed to be a discreet, long-acting HIV prevention option for women. The wearer replaces the product herself once every four weeks. The dapivirine vaginal ring is currently under regulatory review with the European Medicines Agency.
The Phase 3b HOPE study was a follow-on to the NIH-funded ASPIRE clinical trial. ASPIRE and a sister trial called The Ring Study demonstrated in 2016 that the dapivirine ring reduced the risk of HIV infection by roughly 30 percent in women ages 18 to 45 years and was well-tolerated. The goals of the HOPE study were to gather additional data on the safety of the dapivirine ring and new data on whether and how women used it knowing that the earlier trials had shown it was modestly effective.
The HOPE study began in 2016 and enrolled 1,456 former ASPIRE study participants at 14 sites in Malawi, South Africa, Uganda and Zimbabwe. The women were sexually active, HIV-negative and aged 20 to 49 years.
While the ASPIRE study participants did not know until the end of the trial whether they had received the dapivirine ring or a placebo ring, all women who enrolled in the HOPE study were offered the dapivirine ring. During their first three months in the HOPE study, participants attended monthly study visits where they could receive one new ring. Thereafter, they attended quarterly visits where they could receive three new rings, a schedule that more closely resembled how the ring might be distributed in a real-world setting.
Although it was not possible to precisely quantify how much of the time participants wore the dapivirine ring in either the HOPE study or the ASPIRE trial, adherence appeared to be higher in HOPE than in ASPIRE. Adherence was assessed by measuring how much dapivirine was left in returned rings, since the dapivirine level declines when the ring is worn. The amount of dapivirine left in 90 percent of the rings returned by HOPE study participants indicated that those rings had been used for at least some of the prior month. In contrast, the amount of dapivirine left in 77 percent of the rings returned by ASPIRE study participants indicated that those rings had been used for at least some of the prior month. The ring is designed to be worn continuously throughout the month to provide effective protection.
The HOPE study participants became infected with HIV at a rate of 2.7 percent over the year of follow-up. Because the study lacked a concurrent control group receiving a placebo ring, investigators used a mathematical approach based on the ASPIRE placebo group to estimate what the HIV incidence in HOPE would have been had the women lacked access to the dapivirine ring. In this modeling exercise, the average HIV incidence was 4.4 percent over the year of follow-up. Based on these incidence rates, investigators estimate that the ring reduced the risk of acquiring HIV by 39 percent in the HOPE study. The study was not designed to determine the effectiveness of the ring.
