Prevenir – from the French, meaning to prevent. On-demand PrEP, also called intermittent or pericoital PrEP uses a "2-1-1" dosing schedule. The user takes two Truvada pills 2-24 hours prior to sexual intercourse, with one pill daily until 24 hours after their most recent intercourse. People who took HIV pre-exposure prophylaxis (PrEP) "on demand" - that is, before and after sex - were just as likely to prevent HIV infection as people who took PrEP once a day, according to the results of the ongoing Prevenir study. The findings are especially important for men who have sex with men (MSM), who comprised nearly 99% of study enrollees. Currently, the U.S. Food & Drug Administration (FDA) has only approved PrEP as a once-daily pill.
The interim data were presented by the study's lead author, Dr. JM Molina. Study participants were given the option of utilizing either the daily or the "on-demand" dosing method for PrEP, with the opportunity to change strategies at any time. The study ultimately aims to enroll 3,000 people in the Paris metropolitan region; these interim results included roughly 1,600 people. Approximately 55% of the participants chose the on-demand option. At this point in the three-year observational trial stage (May 2017-May 2020), there have been no new HIV infections in either arm of the trial. From May 3rd 2017 to May 1st 2018, 1435 subjects were enrolled across 22 sites, 59% being PrEP-experienced for a median of 10 months. Median age was 37 years, 98.7% were MSM. At enrolment, PrEP was used Daily in 44% and On-demand in 53% of participants. Median number of partners in the 3 months before enrolment was 15 in the Daily group and 10 in the On-demand group (P< 0.001). Median number of condomless sexual en the prior 4 weeks was 3 (range,1-8) and 2 (range,0-4), respectively, P< 0.001. The current follow-up lasted 302 and 361 person-years (PY) in the Daily and On-demand groups, respectively. The incidence of HIV-1 infection was 0 per 100 PY and 0 in the Daily and On-demand groups respectively (P=1.00) and the incidence of study discontinuation was 3.0 and 3.6 per 100 PY (P=0.674) respectively, including 1.3 and 1.1 per 100 PY drop out of PrEP because participants no longer feel at risk. No participant discontinued PrEP for drug-related adverse events. "The study shows that the incidence of HIV in this cohort is zero; averting 85 new infections," according to Molina. Other observations include no differences between the study arms with very low rates of volunteers who were lost to follow up or who discontinued participation, or the number of adverse events. Data on sexually transmitted infection acquisition were not presented; however, 20% of participants reported consistent condom use.
Full results will not be available until 2020. However, Prevenir's interm results, along with prior research, have already had an impact on guidelines for PrEP use. Several health organizations, including the French government, now support on-demand PrEP as a viable option for HIV prevention. During AIDS 2018, the International Antiviral Society-USA (IAS-USA) officially endorsed this regimen as an "alternative to daily PrEP for MSM with infrequent sexual exposures" in its updated Treatment Guidelines released during the conference. The IAS-USA endorsement may impact PrEP uptake and PrEP usage in the U.S. if the FDA and Centers for Disease Control and Prevention (CDC) also update their PrEP guidance.
Conclusions: In this ongoing PrEP cohort in Paris region, enrolling mainly MSM at high risk of HIV-acquisition, no breakthrough HIV-infection was reported so far with either daily or on-demand PrEP, supporting continuing use of both dosing regimens in this population.
Reference: Molina J et al. Incidence of HIV-infection in the ANRS Prevenir study in Paris region with daily or on-demand PrEP with TDF/FTC. 22nd International AIDS Conference, Amsterdam, abstract WEAE0406LB
07/30/2018
PrEP On Demand: Infections Averted
Source: Reporting from Amsterdam for PRN News: Bill Valenti, MD