Changes in sexual behaviors in men who have sex with men : a comparison between the double-blind and open-label extension phases of the ANRS-IPERGAY trial Di Ciaccio, M. /Sagaon Teyssier, Luis Mimi, M. Suzan-Monti, M. Protiere, C. Castro, D. R. Meyer, L. Tremblay, C. Chidiac, C. Capitant, C. Preau, M. Molina, J. M. Spire, B. ANRS IPERGAY Study Group, HIV risk management PrEP Behaviors MSM ANRS-IPERGAY trial 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. 2020 text https://www.documentation.ird.fr/hor/fdi:010078987 fdi:010078987 Di Ciaccio M., Sagaon Teyssier Luis, Mimi M., Suzan-Monti M., Protiere C., Castro D. R., Meyer L., Tremblay C., Chidiac C., Capitant C., Preau M., Molina J. M., Spire B., ANRS IPERGAY Study Group. Changes in sexual behaviors in men who have sex with men : a comparison between the double-blind and open-label extension phases of the ANRS-IPERGAY trial. 2020, 24 (11), 3093-3106 EN FRANCE CANADA