Researchers studying injectable PrEP implant administered twice a year

The emergence of injectable PrEP has already opened up new possibilities for HIV prevention medication — and new research conducted by the Centers for Disease Control and Prevention and the University of North Carolina is looking to build on those developments with an injectable PrEP implant that could last six months.

Rahima Benhabbour, an associate professor at UNC/NCSU Joint Department of Biomedical Engineering, has spent more than five years working with the Centers for Disease Control and Prevention (CDC) to create an injectable implant that would release PrEP medication over time for up to six months. According to the University of North Carolina, experts have been refining the injection material. Cabotegravir, an integrase inhibitor, was the drug used in the study, which was published at nature.com, and researchers have been focusing on developing the drug so it is able to release slowly. Previous attempts to develop such a drug release system were unsuccessful because too much of the drug was released at once, researchers said.

“The burst release was the lowest we’ve ever seen with any drug that was formulated in this injectable,” Benhabbour said in a written statement. “It is important to maintain a low burst release upon injection to mitigate safety concerns due to exposure to high drug levels if the burst is too high. The low burst also allows the drug to last longer in the body, provided that initial drug levels are enough to achieve protection.”

The implant is also removable, which would allow anyone to make the necessary adjustments if they experience adverse reactions. 

Researchers tested the implant on macaques, a monkey species with immune systems that are apparently similar to humans. Out of the six macaques who received the injections, none contracted HIV. 

“This is the first time we showed 100% protection against multiple virus challenges in a macaque model of PrEP over an extended period of time,” Benhabbour said. “Our goal with this technology is a once or twice-yearly injection that could be self-administered.”

The researchers said they will now work to secure funding for human trials. 

The latest developments build on other efforts to explore injectable PrEP as an alternative to the pill, which must be taken daily and is associated with uptake issues — particularly in communities with less access to healthcare. The US Food and Drug Administration (FDA) approved a bi-monthly injectable form of PrEP to prevent HIV in late 2021. Multiple trials in recent years have indicated that injectable PrEP is more effective at preventing HIV than the daily pill.