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. 2013 Dec 18;8(12):e81997.
doi: 10.1371/journal.pone.0081997. eCollection 2013.

No evidence of sexual risk compensation in the iPrEx trial of daily oral HIV preexposure prophylaxis

Julia L Marcus  1 , David V Glidden  2 , Kenneth H Mayer  3 , Albert Y Liu  4 , Susan P Buchbinder  4 , K Rivet Amico  5 , Vanessa McMahan  6 , Esper Georges Kallas  7 , Orlando Montoya-Herrera  8 , Jose Pilotto  9 , Robert M Grant  10
Affiliations

No evidence of sexual risk compensation in the iPrEx trial of daily oral HIV preexposure prophylaxis

Julia L Marcus et al. PLoS One. .

Abstract

Objective: Preexposure prophylaxis (PrEP) with emtricitabine/tenofovir disoproxil fumarate (FTC/TDF) reduced HIV acquisition in the iPrEx trial among men who have sex with men and transgender women. Self-reported sexual risk behavior decreased overall, but may be affected by reporting bias. We evaluated potential risk compensation using biomarkers of sexual risk behavior.

Design and methods: Sexual practices were assessed at baseline and quarterly thereafter; perceived treatment assignment and PrEP efficacy beliefs were assessed at 12 weeks. Among participants with ≥1 follow-up behavioral assessment, sexual behavior, syphilis, and HIV infection were compared by perceived treatment assignment, actual treatment assignment, and perceived PrEP efficacy.

Results: Overall, acute HIV infection and syphilis decreased during follow-up. Compared with participants believing they were receiving placebo, participants believing they were receiving FTC/TDF reported more receptive anal intercourse partners prior to initiating drug (12.8 vs. 7.7, P = 0.04). Belief in receiving FTC/TDF was not associated with an increase in receptive anal intercourse with no condom (ncRAI) from baseline through follow-up (risk ratio [RR] 0.9, 95% confidence interval [CI]: 0.6-1.4; P = 0.75), nor with a decrease after stopping study drug (RR 0.8, 95% CI: 0.5-1.3; P = 0.46). In the placebo arm, there were trends toward lower HIV incidence among participants believing they were receiving FTC/TDF (incidence rate ratio [IRR] 0.8, 95% CI: 0.4-1.8; P = 0.26) and also believing it was highly effective (IRR 0.5, 95% CI: 0.1-1.7; P = 0.12).

Conclusions: There was no evidence of sexual risk compensation in iPrEx. Participants believing they were receiving FTC/TDF had more partners prior to initiating drug, suggesting that risk behavior was not a consequence of PrEP use.

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Conflict of interest statement

Competing Interests: Co-author Kenneth Mayer has received an unrestricted research grant from Gilead Sciences. Co-author Esper Kallas is a PLOS ONE Editorial Board member. This does not alter the authors' adherence to all the PLOS ONE policies on sharing data and materials. For the remaining authors, no conflicts of interest were declared.

Figures

Figure 1
Figure 1. Sexual behavior by perceived treatment group.
Figure 1a shows the mean number of receptive anal intercourse (RAI) partners in the past 3 months by perceived treatment group at 12 weeks. Figure 1b shows the percent of those partners using a condom by perceived treatment group at 12 weeks. Asterisks indicate P<0.05 by t-test.
See this image and copyright information in PMC

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