Background: On-demand PrEP with TDF/FTC has been recommended as an alternative to daily PrEP for MSM by EACS and IAS-USA guidelines, but has not been endorsed yet by WHO due to limited real-world experience.
Methods: The ANRS Prevenir study is an ongoing prospective cohort study enrolling individuals at high risk for HIV infection on PrEP in Paris area. Both daily and on-demand PrEP were offered to MSM. At baseline, month 1 and every 3 months thereafter, subjects were tested for HIV using a 4th generation combined ELISA assay and other STIs and creatinine plasma levels were monitored. At each visit participants provided information regarding sexual behaviour, dosing regimen and adherence using computer assisted self-interviews. HIV and HCV incidence were assessed as well as safety and study retention.
Results: From May 3rd 2017 to October 31st 2018, 2143 subjects were enrolled across 22 sites in the Paris region, 56% already being PrEP user (median duration 10 months). Median age was 36 years (IQR: 30-44), 98.7% were MSM. At enrolment, PrEP was used daily in 46.7% and on demand in 53.3% of participants. Median number of partners in the last 3 months was 15 (IQR: 7-25) in the daily group and 10 (5-15) in the on-demand group (P< 0.001). Median number of condomless sex events in the prior 4 weeks was 2 (0-8) and 2 (0-4), respectively, (P=0.04). Current follow-up lasted 744 and 830 person-years (PY) in the daily and on-demand groups, respectively. HIV-1 incidence was 0 (95% CI: 0-0.5) and 0 (95% CI: 0-0.4) per 100 PY in the daily and on-demand groups, respectively; and HCV incidence was 0.67 and 0.60 per 100 PY, respectively (P= 0.865). Ninety-two subjects discontinued the study during follow-up (4.3%) and 49 (2.2%) discontinued PrEP, but only one for drug-related adverse events (nausea/headache/dizziness).
Conclusions: In this ongoing PrEP cohort in Paris area, enrolling mainly MSM at high risk of HIV-acquisition, no breakthrough HIV-infection was reported so far in participants choosing either daily or on-demand PrEP, supporting continuing use of both dosing regimens in this population.