Alimatravir: HIV prevention pill licensed to 129 countries

Merck, known as MSD outside of the United States and Canada, today announced early components of a multi-faceted strategy to provide rapid, broad and sustainable access in low- and middle-income countries (LMICs) to alimatravir , an investigational, novel, once-monthly oral pill as pre-exposure prophylaxis (PrEP) for the prevention of HIV.

The drug, also called MK-8527, is being tested in two large trials. EXPrESSIVE-10 is running with the Gates Foundation to study safety and efficacy in women and adolescent girls in sub-Saharan Africa. EXPrESSIVE-11 is enrolling people likely to be exposed to HIV across 16 countries. Both studies are now underway and focus on a simple idea: one pill a month instead of daily medication.

Early research suggests alimatravir starts working within an hour of dosing and provides a month of protection. Researchers note it may offer a “cushion of forgiveness” with drug levels staying high enough to prevent HIV for about a week even if a dose is taken late.

In a rare move, Merck has already signed royalty-free licensing agreements with seven generic manufacturers to make and sell the drug in 129 low and lower-middle income countries. The partners include three companies in sub-Saharan Africa and four in India, regions that account for most new HIV diagnoses worldwide. Merck says this is the first time African manufacturers have been included from the start.

With an estimated 40.9 million people living with HIV globally in 2025 and more than half in sub-Saharan Africa, a once-monthly oral option could help with adherence and access. Trial results are expected in the second half of next year, but Merck is already scaling production so generics can move quickly if the drug is approved.

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Alimatravir (MK-8527) is being evaluated as a potential once-monthly oral prevention option for HIV-1. Alimatravir inhibits reverse transcriptase through multiple mechanisms, including:

inhibition of reverse transcriptase translocation, resulting in immediate chain termination, and
induction of structural changes in the viral DNA (delayed chain termination).