Pre-exposure prophylaxis with daily oral emtricitabine and tenofovir disoproxil fumarate was safe and effective at preventing HIV acquisition in men who have sex with men and transgender women, according to findings presented at the 6th IAS Conference on HIV Pathogenesis, Treatment and Prevention in Rome.
However, efficacy may vary as time passes or in subgroups due to differences in adherence, drug interactions or drug penetration into tissues, said Robert Grant, MD, MPH, of the University of California, San Francisco.
"Oral emtricitabine and tenofovir disoproxil fumarate (FTC/TDF) use among MSM provided durable protective benefit,” Grant and colleagues wrote in the abstract. “Among seroconverters, the lack of drug resistance or suppressed viral load indicates low pre-exposure prophylaxis (PReP) exposure. Differences in PrEP efficacy in transgender women may be due to chance, patterns of PrEP use, sexual practices or hormonal effects on drug transport in the mucosa.”
MSM were randomly assigned to daily oral FTC/TDF or placebo, and they were blinded to the study drug for 4 months after the cutoff for the primary analysis, as previously reported in Infectious Disease News.
Overall, PrEP efficacy was 45% (95% CI, 23-61) in the intention-to-treat analysis and 42% (95% CI, 18-60) in the modified intention-to-treat analysis.
No drug resistance was observed among emergent infections and viral loads were similar between the two arms after discontinuation of the study drug. No differences in efficacy were observed (P>.20) in subgroups defined by ethnicity, alcohol use, education or age.
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