Colleen Kelley

Currently, the only available product for PrEP is daily or on-demand TDF/FTC, but those days are limited. Fortunately, there are numerous HIV prevention products in development that will provide additional options. In this late breaker session, a glimpse into the future of biomedical prevention was revealed with 4 oral abstracts.

Islatravir is a novel antiretroviral that is formulated in a long-acting implant. A dose-ranging study conducted among 16 participants where the insert was implanted for 12 weeks showed maintenance of drug levels above the PK antiviral target threshold with potential for maintenance through 52 weeks. Janssen is currently implementing 2 global efficacy trials for their novel vaccine regimen, an Ad26 vector with mosaic HIV inserts +gp140 boost. The vaccine regimens tested in phase 1/2a were immunogenic demonstrating HIV specific humoral and cellular responses. Gilead reported updated data from the TAF/FTC vs. TDF/FTC trial for PrEP that showed non-inferiority of TAF/FTC. They reported that TAF/FTC reached higher drug levels and the EC90 quicker (4h vs. 3 days) and levels persisted (16 vs. 10 days) longer than TDF/FTC suggesting a possibility of improved efficacy. Finally, same day PrEP initiation was effective in a large cohort of MSM and TGW in Latin America.

A once yearly PrEP option and an effective preventive vaccine will be true game changers for the HIV prevention field, and efficacy results for these products will be anxiously awaited. In addition, large scale implementation of same-day PrEP services as done in Latin American MSM and TGW should be applauded and replicated. With respect to TAF/FTC use in PrEP, additional, more robust data are needed before one can conclude that TAF/FTC is safer or more effective than TDF/FTC. For now, efforts should be focused on expanding global access to low-cost TDF/FTC or TDF/3TC to all at-risk populations.

Ana Cristina Garcia Ferreira

New technologies, included implants, vaccine studies looking for better formulations of broad coverage HIV vaccines, and new data from the DISCOVER trial comparing TAF and TDF for PrEP were presented. The first multi-country trial of same-day PrEP initiation in Latin America demonstrated it is feasible.

Matthews presented clinical data about the potential of the Islatravir implant as a once-yearly PrEP option. Stieh evaluated the benefits of moving from monovalent to bivalent HIV vaccine in a phase-3 trial (MOSAICO), with similar safety and tolerability and broader immune response induction. Spinner presented DISCOVER results, a non-inferiority trial comparing F/TAF and F/TDF for PrEP, in which noninferiority was confirmed by sensitivity analysis excluding the individuals suspected to be infected at baseline. Both arms had no differences in HIV risk, STIs, or adherence. TAF reached PBMC levels faster than TDF. The authors tried to extrapolate these findings, interpreting TAF as more effective but were criticized, highlighting that the trial showed non-inferiority. Veloso presented the same day PrEP initiation as a feasible and safe strategy in ImPREP, with a good level of adherence, although with significant differences between countries. She outlined the asymptomatic STI burden observed.

This very interesting session did a broad highlight of new HIV prevention strategies and technologies, coming from pre-clinical to real-life studies in different contexts and populations, providing a diverse framework of new possible prevention tools. Careful evaluation of study design structure and objectives should always be considered when presenting results. The cost will be a key factor to consider when planning the implementation of these technologies.