Midway into a study in which all participants are offered use of a monthly vaginal ring containing an antiretroviral (ARV) drug called dapivirine, researchers have seen women's risk of acquiring HIV reduced by more than half.
Preliminary results of the HOPE open-label study of the dapivirine ring also suggest that women are using the ring more than they did in the parent ASPIRE Phase III trial, the researchers from the National Institutes of Health-funded Microbicide Trials Network (MTN) reported today at the Conference on Retroviruses and Opportunistic Infections (CROI).
The findings are based on a planned interim review of study data that took place in October 2017, one month after the study had closed enrollment. HOPE (HIV Open-label Prevention Extension, or MTN-025) began August 2016. At the time of the review, 1,407 former ASPIRE participants had been enrolled.
The interim review found the rate of new HIV infections was 1.9, considerably lower than what was seen in ASPIRE. HIV incidence, which represents the number of women who are newly infected for every 100 participants in a given year, was 3.3 in the group of ASPIRE participants assigned to use the dapivirine ring and 4.5 among those in the placebo group. Using statistical modeling based on the placebo group in ASPIRE, the researchers determined the rate of new infections would have been 4.1 had women otherwise not been able to take part in HOPE and be offered the ring. The difference in incidence rates represents a 54 percent reduction in HIV risk. While encouraged by these findings, the researchers say they should be viewed with degree of caution given that HOPE has no placebo group and that the results themselves are interim -- not the study's final results.
"Access to the dapivirine ring is making a difference in the lives of women in the HOPE study. While the kind of analysis we used has inherent limitations, the results indicate that HIV incidence among women in HOPE has been reduced by half," said Jared Baeten, MD, PhD, Professor of Global Health, Medicine, and Epidemiology at the University of Washington in Seattle, who reported the interim study results. Dr. Baeten, who is also Co-principal Investigator of the MTN, is leading the HOPE study with Thesla Palanee-Phillips, MMed Sci, PhD, MSc., of the Wits Reproductive Health and HIV Institute, Johannesburg, South Africa, and Nyaradzo Mgodi, MBChB, MMed, of the University of Zimbabwe College of Health Sciences in Harare.