MRK Alimatravir: Once-Monthly HIV PrEP Pill Access Plans

Merck (MRK) announced on July 24, 2026 early access plans for alimatravir (MK-8527), an investigational once-monthly oral pill for HIV pre-exposure prophylaxis currently in Phase 3 development. The strategy includes voluntary licensing agreements with seven generic manufacturers covering 129 low- and middle-income countries, regional manufacturing in Africa and Latin America, and early investment in product manufacturing.

MRK closed at $131.07 on July 24.

What alimatravir is

Alimatravir is a nucleotide reverse transcriptase inhibitor, the same drug class as the backbone of most HIV treatment regimens. It is being evaluated as a once-monthly oral prevention option. Merck says a single pill is predicted to provide one month of protection from HIV-1, with protection starting within one hour of dosing based on pharmacokinetic data from the Phase 2 trial (MK-8527-007).

The drug enters Phase 3 through two trials. EXPrESSIVE-10 (NCT07071623) is enrolling adolescent girls and young women in Kenya, South Africa, and Uganda. EXPrESSIVE-11 (NCT07044297) is evaluating safety and efficacy across 16 countries. Both are enrolling now, with Gates Foundation financial support.

The PrEP convenience ladder

HIV PrEP has been moving toward longer-acting options. The current standard is a daily oral pill, which works well for patients who take it but suffers from adherence gaps. Gilead’s lenacapavir (Yeztugo), FDA-approved in June 2025, is a twice-yearly injection that eliminates the daily pill burden entirely. Merck and Gilead are also developing a once-weekly oral combination (islatravir plus lenacapavir) with a February 2027 PDUFA, covered in our analysis of the GILD-MRK once-weekly HIV pill.

Alimatravir sits between daily oral and twice-yearly injectable. A monthly pill could appeal to patients who want oral dosing without daily adherence, but who dislike injections. The competitive question is whether monthly oral beats twice-yearly injectable for real-world adherence.

Why license before approval

Merck’s decision to sign generic licenses while Phase 3 trials are still enrolling is unusual. The company is signaling confidence in the program and addressing global health equity proactively. HIV PrEP access in low- and middle-income countries has historically lagged behind high-income markets. The 129-country licensing scope and African manufacturing investment are designed to close that gap if the drug is approved.

For Merck, the commercial opportunity is concentrated in high-income markets. The LMIC access strategy is a reputational and public health play, not a near-term revenue driver.

What to watch

The EXPrESSIVE Phase 3 data readouts are the catalyst. If alimatravir shows efficacy and safety comparable to existing PrEP options, Merck will file for approval. Watch the competitive dynamic with Gilead’s lenacapavir franchise, which has a multi-year head start and is moving toward an oral weekly option.