No New HIV in MSM/Transgenders Using 4 or More PrEP Tablets Weekly
Trans MSM
Taking four or more tenofovir/emtricitabine (TDF/FTC) tablets weekly for preexposure prophylaxis (PrEP) prevented HIV acquisition in a cohort study of 1603 men who have sex with men (MSM) and transgender women. Three quarters of study participants invited to take PrEP did so in this open-label extension of three clinical trials.
Researchers who conducted this analysis observed that PrEP efficacy depends on uptake, adherence, and sexual practices. The study involved people enrolled in three PrEP trials: ATN 082, iPrEx, and the US Safety Study. All participants were invited to receive PrEP, and those who declined received all supportive services offered to PrEP takers. The investigators measured drug concentrations in plasma and dried blood spots of people who became infected with HIV and in a random sampled of people who remained HIV-negative.
This 72-week prospective study enrolled 1603 HIV-negative men and transgender women who have sex with men, 1225 (76%) of whom opted to use PrEP. Participants who started PrEP were more likely to report condomless receptive anal intercourse (81% versus 75%, P = 0.003) and to have serologic evidence of herpes (77% versus 75%, P = 0.03).
Among people using PrEP, HIV incidence was 1.8 per 100 person-years, compared with 2.6 per 100 person-years in people who did not use PrEP. Those rates translated into a 49% lower HIV risk in PrEP takers in an analysis adjusted for sexual behavior (hazard ratio [HR] 0.51, 95% confidence interval [CI] 0.26 to 1.01). Compared with the placebo group of the randomized trial phase, HIV risk was 51% lower in PrEP takers during the open-label extension (HR 0.49, 95% CI 0.31 to 0.77).
Among PrEP takers, HIV incidence was highest in people with no detectable drug in dried blood spots (4.7 per 100 person-years) and lower in those in whom drug concentrations suggested taking fewer than 2 tablets per week (2.3 per 100 person-years) or 2 to 3 tablets per week (0.6 per 100 person-years). Among participants whose drug levels indicated use of 4 or more tablets per week, HIV incidence was 0.0 per 100 person-years.
PrEP drug concentrations were higher in older participants, those with more schooling, those who reported receptive anal intercourse without condoms, those with more sexual partners, and those with a history of syphilis or herpes.
"PrEP uptake was high when made available free of charge by experienced providers," the researcher conclude, adding that "the effect of PrEP is increased by greater uptake and adherence during periods of higher risk." They noted that PrEP drug levels in dried blood spots correlate strongly with protection from HIV.
Source: Robert M. Grant, Peter L. Anderson, Vanessa McMahan, Albert Liu, K. Rivet Amico, Megha Mehrotra, Sybil Hosek, Carlos Mosquera, Martin Casapia, Orlando Montoya, Susan Buchbinder, Valdilea G. Veloso, Kenneth Mayer, Suwat Chariyalertsak, Linda-Gail Bekker, Esper G. Kallas, Mauro Schechter, Juan Guanira, Lane Bushman, David N. Burns, James F. Rooney, David V. Glidden, for the iPrEx study team. Uptake of pre-exposure prophylaxis, sexual practices, and HIV incidence in men and transgender women who have sex with men: a cohort study. Lancet Infectious Diseases. 2014; 14: 820-829.
Written by Mark Mascolini on behalf of the International AIDS Society