Abstract Body

On-demand PrEP with TDF/FTC has been recommended as an alternative to daily PrEP for MSM by EACS, WHO and IAS-USA guidelines, but has not been endorsed yet by CDC due to limited real-world experience.

The ANRS Prevenir study is an ongoing prospective cohort study enrolling individuals at high risk for HIV infection on PrEP. MSM could opt for either daily or on-demand PrEP with TDF/FTC. 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 drug adherence. Our main objective was to assess the overall HIV incidence in the study and per dosing regimen, as well as incidence of bacterial STIs (including syphilis, gonorrhoea, chlamydia and Mycoplasma genitalium) and viral hepatitis. Safety and study retention were also assessed. This analysis uses data accumulated up to September 30, 2020.

From May 3rd 2017 to March 2nd 2019, 3067 subjects were enrolled across 22 sites in the Paris region, 44% being PrEP naive. Median age was 36 years (IQR: 29-43), 98.5% were MSM. At enrolment, PrEP was used daily and on demand by 50.5% and 49.5% of participants, respectively. Median number of partners in the last 3 months was 10 (5-20) and median number of condomless sex events in the prior 4 weeks was 2 (0-5). Median follow-up lasted 22 months and accumulated 5633 person-years (PY) with an overall HIV incidence in the cohort of 0.11 (95% CI: 0.04-0.23) per 100 PY. Six participants (3 daily, 3 on demand) acquired HIV-infection during the study period (P=0.99). Condom use at last sexual intercourse was 19.6%. Overall STIs incidence was 73 (95% CI: 70.7-75.5) per 100 PY which remained stable during follow-up except during the COVID-19 lockdown when it dropped to 32.4 per 100 PY (P<10-4). HCV incidence was 0.69 per 100 PY. Incidence of participants lost to follow-up was 10.3/100 PY and 19 subjects (0.6%) discontinued PrEP for drug-related adverse events (gastrointestinal: 12, e-GFR < 70 ml/mn: 4, other: 3).

In this PrEP cohort, enrolling mainly MSM at high risk of HIV-acquisition in Paris, HIV incidence was low whether participants used daily or on demand PrEP. There was a high incidence of bacterial STIs and HCV infection despite a drop in STIs incidence during the COVID-19 lockdown.