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  Conference on Retroviruses
and Opportunistic Infections
Will be Virtual
Boston USA
March 6-10, 2021
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Low New-HIV Rate With Both Daily
and On-Demand PrEP in Paris MSM
  CROI 2021, Conference on Retroviruses and Opportunistic Infections, March 6-10, 2021
Mark Mascolini
In a prospective cohort study of 3067 people, half taking daily preexposure prophylaxis (PrEP) with tenofovir/emtricitabine (TDF/FTC) and half using on-demand (as-needed) PrEP, only 3 people in each group became infected with HIV [1]. In a study population largely composed of men who have sex with men (MSM), all 6 people who acquired HIV had stopped PrEP before testing positive and all were MSM.
The ANRS IPERGAY trial established the effectiveness of on-demand PrEP, which requires taking TDF/FTC just before and after sex (86% relative reduction in HIV incidence with TDF/FTC versus placebo, P = 0.002) [2,3]. The European AIDS Clinical Society, World Health Organization, and IAS-USA endorse on-demand TDF/FTC PrEP as an alternative to daily PrEP, but the Centers for Disease Control and Prevention (CDC) continues to withhold judgment.
The ANRS Prevenir study enrolls HIV-negative people at high risk for HIV infection because of inconsistent condom use and multiple sex partners. The protocol lets participants choose daily or on-demand TDF/FTC PrEP. Participants get tested for HIV at entry, after 1 month, then every 3 months. At every visit they also get tested for other sexually transmitted infections (STIs) and answer questions about sex behavior and PrEP adherence.
Among the 3067 Paris-region participants, 98.5% were MSM, 85.6% were Caucasian, and 55.8% had used PrEP before. Median age stood at 36 (interquartile range [IQR] 29 to 43). Participants had a median of 10 sex partners (IQR 5 to 20) in the past 3 months and 2 condomless sex acts (IQR 0 to 5) in the past 4 weeks.
While 1544 participants (50.5%) opted for daily PrEP, 1515 (49.5%) picked on-demand PrEP. Daily PrEP users included a slightly but significantly lower proportion of MSM (97.9% vs 99.2%, P = 0.0002). The daily-PrEP group had a marginally higher median number of sex partners in the past 3 months (12 versus 10), but that difference was statistically significant because of the big sample size (P < 0.0001). Low proportions of both groups reported condom use (16.8% daily vs 19.6% on-demand).
Similar high proportions of the daily and on-demand groups used PrEP properly (97.9% and 97.0%). For this cohort study on-demand use meant at least one pill within the 24 hours before sex and one pill within 24 hours after sex. A higher proportion of on-demand users than daily users did not take PrEP during the study (18.4% vs 4.3%).
Through an average follow-up of 22.1 months, 6 people-3 in each group-picked up HIV infection. HIV incidence was identical in the daily and on-demand groups (0.12 cases per 100 person-years, 95% confidence interval [CI] 0.02 to 0.34) to yield an incidence rate ratio [IRR] of 0.99 (95% CI 0.13 to 7.38). Assuming an HIV incidence of 6.6 cases per 100 person-years for no PrEP, based on people taking placebo instead of TDF/FTC PrEP in the IPERGAY trial [2], the Prevenir team figured that PrEP prevented 361 HIV infections. All 6 people who acquired HIV infection were MSM with ages ranging from 24 to 52, and all had stopped PrEP before testing positive for HIV.
During the study period, clinicians diagnosed 43 cases of viral hepatitis-39 of them HCV-in 41 participants for an incidence of 0.76 cases per 100 person-years. Incidence of any STI fell from 75.5 per 100 person-years until 2 months before the COVID-19 lockdown, to 66.5 per 100 person-years at 2 months before the lockdown, to 32.4 per 100 person-years during the lockdown (P < 0.0001). Lockdown-related incidence declines were significant for chlamydia and gonorrhea (P < 0.0001 for both) but not for mycoplasma or syphilis, which had much lower incidence than chlamydia or gonorrhea to begin with.
Incidence of any drug-related adverse event was significantly lower with daily PrEP than on-demand PrEP (8.21 vs 11.98 per 100 person-years, IRR for daily vs on-demand 0.68, 95% CI 0.57 to 0.82). The serious adverse event rate was nonsignificantly higher with daily than on-demand PrEP (4.10 vs 3.64 per 100 person-years, IRR 1.13, 95% CI 0.84 to 1.50). Stopping drugs because of a drug-related adverse event was nonsignificantly less frequent with daily than on-demand PrEP (0.27 vs 0.35 per 100 person-years, IRR 0.77, 95% CI 0.24 to 2.32). Fourteen people in each group had a creatinine clearance measure below 50 mL/min during the study (0.54 per 100 person-years with daily PrEP and 0.55 per 100 person-years with on-demand PrEP, IRR 0.99, 95% CI 0.44 to 2.24).
The findings add to evidence that on-demand PrEP is an effective and relatively safe way for high-risk people to prevent HIV infection.
1. Molina JM, Ghosn J, Delaugerre C, et al. Incidence of HIV infection with daily or on-demand oral PrEP with TDF/FTC in France. CROI 2021, Conference on Retroviruses and Opportunistic Infections, March 6-10, 2021. Abstract 148.
2. Molina JM, Capitant C, Spire B, et al. On-demand preexposure prophylaxis in men at high risk for HIV-1 infection. N Engl J Med. 2015;373:2237-2246. doi: 10.1056/NEJMoa1506273.
3. Molina JM, Charreau I, Spire B, et al. Efficacy, safety, and effect on sexual behaviour of on-demand pre-exposure prophylaxis for HIV in men who have sex with men: an observational cohort study. Lancet HIV. 2017;4:e402-e410. doi: 10.1016/S2352-3018(17)30089-9.