The future of HIV prevention might fit in a single monthly pill, and it's already in clinical trials

Review written by: Roshni Kadam

What if protecting yourself from HIV took one pill a month instead of one every day? The data suggests we're getting closer. Since the start of the HIV epidemic, an estimated 92 million people have acquired the virus, and 44.2 million have died from HIV-related causes. Treatment has come a long way since then. Combination antiretroviral therapy has turned HIV from a fatal diagnosis into a manageable chronic condition. But maintaining suppression still means staying on long-term regimens, and drug resistance remains an ongoing concern. There's still no vaccine for HIV, which means prevention leans heavily on prophylactic options with most commonly, daily oral therapy. It works, and it has meaningfully reduced new infections. But daily adherence is hard to sustain in the real world, shaped by HIV-related stigma and concerns about side effects. The FDA-approved injectable capsid inhibitor lenacapavir offered a long-acting alternative, administered every 8 weeks via intramuscular injection by a healthcare provider. Effective, but not without friction, what that means is frequent clinic visits, and the possibility of injection-site reactions. What's missing is a convenient option people can manage entirely on their own. That's where MK-8527 comes in, a Merck compound designed for once-monthly oral dosing, currently advancing through clinical trials for HIV pre-exposure prophylaxis (PrEP). What makes it mechanistically interesting is its drug class: nucleoside reverse transcriptase translocation inhibitors (NRTTIs), a newer approach that goes beyond older NRTIs. Instead of a single way to block the virus, MK-8527 can stop viral DNA synthesis two different ways that is the immediate and delayed chain termination that works by interfering with a step in viral replication called translocation.

The pharmacokinetics behind it are what make once-monthly dosing plausible. When given to rhesus monkeys, a single oral dose, they tracked two things firstly, how quickly the drug cleared from the bloodstream, and second how long its active form persisted inside the immune cells HIV targets. The parent drug cleared from plasma within hours. But its active form, once inside white blood cells, had a half-life of roughly 48 hours, nearly a week's worth of durability from a single dose. Oral bioavailability was strong too, reaching 100% in monkeys. In other words, the drug doesn't need to stay in the bloodstream to keep working. Once it's inside the cells that matter, it stays active long after it's left the blood.

Based on this data, MK-8527 could support once-weekly, or even once-monthly, dosing in humans which is a potential shift for HIV PrEP, where daily pill adherence remains one of the biggest real-world barriers to prevention. The compound is now moving through further clinical evaluation. So could a once-monthly pill be the next major shift in HIV prevention? The data suggests we're getting closer.

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Raheem IT, Girijavallabhan V, Fillgrove KL, Goh SL, Bahnck-Teets C, Huang Q, et al. (2025) MK-8527 is a novel inhibitor of HIV-1 reverse transcriptase translocation with potential for extended-duration dosing. PLoS Biol 23(8): e3003308. https://doi.org/10.1371/journal.pbio.3003308