Pre-exposure prophylaxis (PrEP) can be taken ONLY as needed instead of every day, a new study suggests.
In “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”, which was published in The Lancet HIV, Jean-Michel Molonaet al found that taking four doses of PrEP around the time of sexual activity cut the risk of being diagnosed with HIV by 97% percent.
PrEP is marketed by Gilead as Truvada, which contains a combination of the two anti-HIV drugs emtricitabine and tenofovir disoproxil fumarate. In 2012, Truvada was approved by the US Food and Drug Administration for PrEP. It is typically taken daily, similar to ARVs (antiretroviral medicines) taken by people living with HIV (PLHIVs).
For this study, the researchers invited men and transgender women who have sex with men, previously enrolled in the randomized placebo-controlled ANRS IPERGAY trial at seven sites (six in France and one in Canada), to participate in an open-label extension with on-demand tenofovir disoproxil fumarate (300 mg) and emtricitabine (200 mg) to be taken before and after sexual intercourse. The 361 participants were told to take two doses of Truvada between two and 24 hours before sex, another dose 24 hours later and a fourth dose 24 hours after that.
The researchers then assessed the incidence of HIV and other sexually transmitted infections (STIs), PrEP adherence, safety, and sexual behaviour. Statistical analyses included comparisons of proportions and incidence between the randomized phase of the ANRS IPERGAY trial and the open-label phase, and all participants were included in safety analyses.
The overall rate of HIV among those in the study was 0.19 cases per 100 people per year, compared to 6.60 cases per 100 people per year among men who were assigned to take a dummy pill at a larger trial. This indicated a “relative reduction of 97% in the incidence of HIV with on-demand PrEP”, according to the researchers.
Participants used a median of 18 pills of study drugs per month (IQR 11–25), and at the six-month visit, 240 (71%) of 336 participants had tenofovir detected in plasma.
Drug-related gastrointestinal events were reported in 49 participants (14%) but were self-limited.
Four participants (1%) discontinued PrEP, three because of an increase in plasma creatinine.
The proportion of participants reporting condomless sex at their last receptive anal intercourse significantly increased from 77% (136 of 176 participants) at baseline to 86% (66 of 77 participants) at 18 months’ follow-up.
The incidence of a first bacterial STI during this open-label phase did not change significantly compared with the randomized phase. But according to the researchers, “high rates of STIs resulting from low condom use did not undermine PrEP efficacy, but warrant frequent testing.”
On-demand oral PrEP is “highly effective at preventing HIV infection among high-risk men who have sex with men and therefore represents an alternative to daily PrEP, expanding choices for HIV prevention,” the researchers ended.