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The IPERGAY study showed that on-demand preexposure prophylaxis (PrEP) with TDF/FTC (2 pills 2–24 hours before sex, one 24 hours later, and one 24 hours after that) was effective in reducing HIV acquisition among men who have sex with men (MSM). However, the median sexual intercourse episodes per month was 10 and median pill use per month was 15, a dosing thought to provide protection equivalent to daily PrEP. In this subanalysis of the study, the investigators sought to determine whether MSM who took fewer than 15 pills per month because they had less frequent sex but still had high PrEP adherence were also protected.
Two hundred seventy participants (134 placebo and 136 TDF/FTC recipients) contributed 134 person-years of less-frequent sexual intercourse (median, 5 episodes per month) and high PrEP adherence (median, 9.5 pills per month). This subgroup had a higher educational level and fewer sexual partners than the other study participants. Six HIV infections occurred during periods of less-frequent intercourse, all with placebo, giving an HIV incidence of 9.2 per 100 person-years vs 0.0 per 100 person-year with TDF/FTC (risk reduction ratio, 100%).
Antoni G et al. On-demand pre-exposure prophylaxis with tenofovir disoproxil fumarate plus emtricitabine among men who have sex with men with less frequent sexual intercourse: A post-hoc analysis of the ANRS IPERGAY trial. Lancet HIV 2019 Nov 26; [e-pub]. (https://doi.org/10.1016/S2352-3018(19)30341-8)
Comment
These findings suggest that the use of sex-driven PrEP is an alternative to daily PrEP for MSM who have five episodes of sexual intercourse per month or more. Whether sex-driven PrEP is protective for persons with fewer than five episodes of intercourse per month is unknown. To my knowledge, Gilead has not asked for FDA approval to make sex-driven PrEP an indication, and I think it is unlikely that it will. Nevertheless, the European AIDS Clinical Society has endorsed sex-driven PrEP as a feasible approach for HIV prevention among MSM (https://www.eacsociety.org/files/2019_guidelines-10.0_final.pdf) as have the IAS-USA guidelines (https://www.iasusa.org/wp-content/uploads/guidelines/arv/arv_2018.pdf). While this is not yet the case for the CDC, we can hope that this and other studies will provide the necessary evidence to modify the CDC PrEP guidelines, which would benefit public health.