A scientific review board has closed down the oral tenofovir arm of the Vaginal and Oral Interventions to Control the Epidemic (VOICE) study looking at pre-exposure prophylaxis (PrEP) HIV prevention interventions among women in Africa.
The Microbicides Trial Network, responsible for the study, made the announcement Wednesday. VOICE is the first study to compare the safety and efficacy of oral versus topical PrEP interventions in the prevention of sexually transmitted HIV among 5,000 women at various study sites in Africa.
The Data Safety Monitoring Board “determined that the trial will not be able to demonstrate that tenofovir tablets (TDF) are effective in preventing HIV in the women enrolled in the trial,” according to a press release from the HIV Prevention Trials Network (HPTN). Although the use of oral tenofovir will be discontinued in the study, Truvada (a combination therapy containing tenofovir and emtricitabine) and the tenofovir-containing vaginal gel arms will continue on.
FHI announced in April that its FEM-PrEP trial – which looked at once-daily oral Truvada versus a placebo among high-risk heterosexual, HIV-negative women – was halted as well because safety investigators found that new HIV infections among participants in the Truvada arm equaled the number of infections in those assigned to the placebo arm.
“It’s a total mystery why two big studies have zero percent and two others show 62 to 73 percent efficacy – it’s unheard of,” said Sten Vermund, MD, PhD, a member of the Center for Global Health Policy’s Scientific Advisory Board and head of the HIV Prevention Trials Network. “The implications of this for oral tenofovir use for prevention among men who have sex with men is minimal, but PrEP for women is very dubious until we sort this out.”
During a timely discussion on women and antiretrovirals (ARVs) for HIV prevention held Thursday morning by FHI, the Executive Director of the Structural Drivers of HIV Research Consortium (STRIVE) Lori Heise urged members of the audience to keep the development of topical gels and other vaginal products for the prevention of HIV on the development and advocacy agenda, including non ARV-based products. Heise listed her five key arguments in favor of vaginal gels:
- They are liked by women and couples
- some say it improves the sexual experience
- You get more of the drug where you need it
- vaginal microbicides absorb more drug into the tissue (at the site of potential infection) and less into the blood stream
- less likely to develop drug resistance
- A lot of people want to use something only when they need it
- Studies have yet to show whether oral PrEP can be taken on an intermittent basis
- Vaginal microbicides are not transferable to treatment
- For instance, users will not be tempted to give oral medication to an HIV-infected family member for treatment
- It is something women can use and control.