Weekly Antiretroviral Drug Acts as Both HIV Treatment & PrEP

Research presented at the Ninth International AIDS Society Conference on HIV Science last week in Paris showed that a single oral dose of MK-8591, a long-acting antiretroviral, suppressed HIV for seven days in a clinical trial. The drug also appeared to protect monkeys from rectal and vaginal HIV transmission. 

The findings were presented by Randolph Matthews from Merck, who pointed out that while adherence is crucial for both antiretroviral therapy and PrEP, some people might find it difficult to take a daily pill.

This particular drug would be taken in single doses every 7 to 10 days, and could prove to be a better alternative for these people. 

MK-8591 (also known as EFdA) works by binding to the polymerase active site of HIV reverse transcriptase. As AIDS Map points out, previous research showed MK-8591 to be highly potent in animal and human studies, and performed an even distribution throughout the body in monkey trials — including the rectum and vagina — for a week. And when the drug was injected, it lasted up to six months! 

Researchers described the effects of MK-8591 as leading to “rapid and robust” suppressions in viral loads. And while there were some symptoms related to treatment, they weren’t serious (typically a moderate headache or skin rash that later disappeared). 

When it came to using MK-8591 as an HIV preventative, a separated study led by Martin Markowitz of the Aaron Diamond AIDS Research Center involved giving eight male monkeys an oral dose of MK-8519 at the start of the study. They were then given weekly doses afterward, and on day 6, were exposed to SHIV (a simian-human hybrid virus similar to human HIV).

By the end of the trial, none of the monkeys showed to have caught the virus.