Horizon 1 1 17 ACL : Articles dans des revues avec comité de lecture répertoriées par l'AERES AIDS and Behavior 3093-3106 HIV risk management PrEP Behaviors MSM ANRS-IPERGAY trial FRANCE CANADA 2020 fdi:010078987 ENG AIDS and Behavior 1090-7165 ISI:000527516000001 11 10.1007/s10461-020-02864-8 https://www.documentation.ird.fr/hor/fdi:010078987 https://www.documentation.ird.fr/intranet/publi/depot/2021-04-20/010078987.pdf 24 Horizon (IRD) Pre-Exposure Prophylaxis (PrEP) is changing the landscape of HIV prevention, and may bring changes in sexual behaviors. The double-blind phase (DBP) and open-label extension (OLE) study of the ANRS-IPERGAY trial allowed us to assess changes in sexual behavior of men who have sex with men (MSM) taking sexual activity-based (i.e., on-demand) PrEP. Generalized Estimating Equation (GEE) models found a significant decrease in the number of sexual partners (Coefficient [CI95%], p value; - 0.37[- 0.70 to - 0.04], p = 0.03) between the DBP and OLE as well as in the number of sexual relations (- 0.25 [- 0.49 to 0.00], 0.04). GEE estimates also showed that respondents' most recent sexual relation was less likely to have been with an unknown casual partner during the OLE than during the DBP (Odds Ratio [CI95%], p value: 0.75[0.62-0.92], 0.005). Furthermore, they showed an increase in the proportion of condomless anal sex in the OLE (1.32[1.04-1.67], 0.02), a decrease in the proportion of 'suboptimal PrEP adherence' over time (0.75[0.58-0.97], p = 0.03), a decrease in PrEP only use (0.73[0.55-0.96], 0.03) and in both PrEP and condom use over time (0.70[0.51-0.95], 0.02) and finally, a decrease in alcohol consumption between the DBP and OLE (0.74[0.61-0.90], 0.002). We observed both protective and risky behaviors in terms of HIV and STI risk after on-demand PrEP uptake in the OLE phase. Our findings are consistent with results from previous PrEP trials. 056 ; 052 UR259