This Week in HIV Research: Taking Treatment 4 Days a Week Maintains Viral Suppression, and On-Demand PrEP Highly Effective

This week, a study finds that taking antiretroviral therapy from Monday toThursday, while taking weekends off, maintained undetectable viral loads for the majority of study participants. Another study provides updated analysis on how effective on-demand pre-exposure prophylaxis (PrEP) is at preventing HIV. To beat HIV, you have to follow the science!

Taking Antiretrovirals Only Monday ThroughThursday Works

The vast majority of study participants living with HIV who had undetectable viral loads while on stable antiretroviral therapy were able to maintain viral suppression while taking treatment only four days a week, according to a French study presented at AIDS 2016.

In this non-randomized, multicenter trial of 100 participants who took two nucleoside analog reverse transcriptase inhibitors plus a boosted protease inhibitor or a non-nucleoside reverse transcriptase inhibitor for 48 weeks, 96% continued to have viral loads of less than 50 copies/mL during the short-cycle regimen.

Adherence to the four-days-on, three-days-off therapy was 90%, as measured in a sub-section of trial participants via electronic pill boxes, drug levels in the blood and self-reported questionnaires. The majority (82%) of those in the study were men.

The next step is a 48-week randomized trial involving 640 participants, with half on a seven-day regimen and half on a four-day regimen. If the short-cycle regimen proves to be non-inferior to taking medications every day, all participants will continue on short-cycle therapy for another 48 weeks. That study is expected to start by the end of this year.

Read: This Week in HIV Research: Zero HIV Transmissions With Undetectable Viral Load in PARTNER Study, and Integrase Inhibitors vs. Protease Inhibitors

On-Demand PrEP Highly Effective in Preventing HIV

Taking PrEP only around the time of sexual intercourse was effective in preventing HIV infection among men who have sex with men (MSM), reported a study in France and Canada that was presented at AIDS 2016.

This open-label follow-up to the IPERGAY study found that only one of 362 study participants acquired HIV, despite significantly lower use of condoms during receptive anal intercourse than in the original study.

Low condom use was also evident from the almost 40% of study participants who were infected with a sexually transmitted disease during the study period. All participants took two tablets of tenofovir/emtricitabine (Truvada, TDF/FTC) between 2 and24 hours before intercourse, one on the day (or days) of intercourse, and one or two after having sex. With everyone able to take Truvada, HIV incidence dropped to 0.30 per 100 person-years from 6.60 in the placebo arm of the original study and 0.91 in the Truvada arm of the original IPERGAY trial.

Based on the results of this study, a large-scale PrEP research project is expected to start in late 2016 in Paris.

Vaginal Ring Very Effective in Preventing HIV, if Used Consistently

A vaginal ring containing the antiretroviral dapivirine (TMC120) reduces the risk of acquiring HIV by more than half when women use it consistently, an analysis of data from the ASPIRE study that was reported at AIDS 2016 showed.

The original study found only a 27% overall lower risk of acquiring HIV. However, not all study participants actually used the ring. The current analysis investigated the levels of dapivirine that remained in used vaginal rings and correlated these with known cases of HIV infection among more than 2,000 study participants.

Women who were medium to highly adherent to this prevention method as indicated by low residual drug levels (RDL ≤ 22 mg) in their vaginal rings were 65% less likely to HIV seroconvert than those in the placebo arm. This compared to a 31% lower risk of HIV acquisition compared to the placebo among those whose RDL was ≥23.5 mg, indicating non-adherence.

All ASPIRE participants who did not acquire HIV are eligible to join the next trial, called HOPE, which will study the acceptability and use of the vaginal ring now that its effectiveness has been established.