Researchers Test Quick-Dissolving Rectal PrEP for HIV Prevention

Pre-exposure prophylaxis (PrEP) has been beneficial in the fight against the spread of HIV. What started with the pills Truvada and Descovy transitioned into a PreP ring and a recent long-acting injectable to help people avoid the day-to-day doses.

Outside of the medically prescribed daily dose of PrEP, however, some people take the PrEP pills only before and after sex instead of all the time, and the Centers for Disease Control and Prevention (CDC) has noted that some off-label, “on-demand” PrEP is protective for men having anal sex with no condom.

With all that in mind, a group of researchers under the Contraceptive Research and Development (CONRAD) program are studying whether a quick-dissolving pill inserted into the rectum or vagina would be an effective form of on-demand PrEP.

According to Managed Healthcare Executive, the experimental rectal pill contains 20 milligrams of tenofovir alafenamide (Descovy) and 16 milligrams of elvitegravir (Vitekta).

“In nonhuman primates, the insert provided protection from infection when used in the vagina and the rectum,” said Sharon A. Riddler, M.D., professor of infectious diseases at the University of Pittsburgh School of Medicine.

Riddler presented the findings alongside her colleague at the Conference on Retroviruses and Opportunistic Infection in Seattle in February.

Twenty-three HIV-negative participants at the Universities of Pittsburgh and Alabama at Birmingham were chosen, six of whom were assigned female at birth. Each volunteer received a single dose of the insert in the clinic and blood, rectal fluid, and rectal tissue are collected. They repeated the process seven weeks later.

The tests showed positive results but indicated that two inserts are more likely to provide better protection than one. At that, the study showed limited side effects — only one mild case of anal erythema — which led Riddler and her colleagues to believe insertion would be another important choice for HIV prevention.

“Although the currently available products for prevention (oral, injectable, ring) have all been proven to be effective, there remain many barriers to these being used by people with the greatest need for prevention,” said Riddler. “Additionally, even people who can access PrEP often do not because of cost, side effects, inconvenience, etc., so the continued development of a safe, discreet, on-demand, flexible option would be a great outcome of this small Phase 1 clinical trial.”