Long-Acting PrEP promises to reduce the number of new HIV cases by 44%

A team of scientists from Brown University and Yale University proposed a model for assessing the use of an injectable version of pre-exposure HIV prevention (PrEP), which is not taken on a daily basis as it now, but every other month. Experts have established that an injection version of a prophylactic agent can be more effective than a tablet form. The results of the work were published last month in the Lancet journal.

Currently LAI-PrEP, intended for prophylaxis of prolonged-duration HIV, undergoes phase 3 of clinical trials. It has already demonstrated high results in animal testing.

One of the co-authors of the study Will Goedel from the University of Brown in an interview with MD Magazine said:

“Remembering to take a pill every day can be a challenge for some people for a variety of reasons (i.e., daily routines changing, traveling, simply forgetting) […] It might be challenging for some people if they're in a situation where they need to take their pill in front of other people and don't want to be perceived as promiscuous or HIV-positive.”

According to MD Magazine, the study was based on the modeling of HIV transmission in the group of men who have sex with men (MSM). The work included data on 11.2 thousand Americans.

Using data on LAI-PrEP from the results of macaque models, the researchers modeled HIV transmission rates under a scenario in which 35% of patients were using PrEP.

LAI-PrEP was evaluated both in comparison with tableted PrEP, and separately. The modeling horizon was 10 years: from 2015 to 2024.

According to the received data, the injectable version of PrEP resulted in a 44% reduction in HIV transmission, while oral PrEP cut transmission by only 33%.

According to Goedel, if LAI-PrEP does work on humans as well as it worked on macaques, a long-acting injectable drug can become as effective as oral PrEP. In addition, he believes, LAI-PrEP will provide a new version of HIV prevention besides the tablet form and condoms. The injection of the drug every other month also promises to increase adherence.

Despite such promising results, the study’s lead author, Professor Brandon D. L. Marshall at Brown University, noted that it is not yet clear how the injection version would perform in humans, both physically and in terms of adherence.

“Unfortunately, it’s too early to tell how LAI-PrEP could be administered in real-world settings,” he said. “Results from the phase 3 trial likely won’t be available until 2021.”

Goedel supported his colleague, noting that the results of modeling do not remove a number of important issues related to injections.

So, according to him, it is unclear clear how long the drug can remain in someone's body. This directly relates to the “long tail” problem of waning drug concentrations, and the subsequent potential for drug resistance.