Merck Launches Phase 3 Trials for Once-Monthly Oral HIV PrEP Candidate MK-8527

▎WuXiKant

MSD announced the launch of the EXPrESSIVE Phase 3 clinical program today to evaluate the safety and efficacy of its investigational once-monthly oral small molecule therapy, MK-8527, for HIV pre-exposure prophylaxis (PrEP).

Among them, the EXPrESSIVE-11 (MK-8527-011) trial is expected to begin recruiting participants in August 2025. This trial aims to evaluate the safety and efficacy of MK-8527 in populations with a higher risk of HIV-1 exposure. Meanwhile, the EXPrESSIVE-10 (MK-8527-010) trial, conducted in collaboration with the Gates Foundation, will assess the safety and efficacy of MK-8527 in women and adolescent girls in sub-Saharan Africa and is anticipated to initiate participant recruitment within the next few months.

MSD decided to initiate a Phase 3 clinical trial program based on the results of a double-blind, multicenter Phase 2 clinical trial (MK-8527-007). This study evaluated the safety and pharmacokinetics of MK-8527, enrolling 350 subjects aged 18 to 65 with a lower risk of HIV-1 exposure. These subjects were randomly assigned in a 2:2:2:1 ratio to receive once-monthly oral MK-8527 (3 mg, 6 mg, or 12 mg) or a placebo for six months. During the trial,The incidence of adverse events in each dose group of MK-8527 was similar to that in the placebo group.And laboratory tests (including total lymphocyte count and CD4 positive T-cell count) showed no clinically significant changes.The pharmacokinetic data of MK-8527 and its active form MK-8527-TP support the continued development of its use as a once-monthly oral PrEP option.

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MK-8527 is a nucleoside reverse transcriptase translocation inhibitor (NRTTI) being evaluated as a potential once-monthly oral HIV-1 prevention regimen. MK-8527 inhibits reverse transcriptase activity through multiple mechanisms of action, including translocation inhibition and delayed chain termination.

According to the industry media Endpoints News, MK-8527, an oral medication taken once a month, has entered the late-stage clinical development phase and may become a significant advancement in the field of HIV pre-exposure prophylaxis.This formulation is expected to reduce the medication burden on patients, improve adherence, and thereby promote the global普及 of PrEP therapy.Currently approved PrEP regimens mainly include two forms: daily oral administration and long-acting injections.

References:

[1] Merck to Initiate Phase 3 Trials for Investigational Once-Monthly HIV Prevention Pill. Retrieved July 14, 2025 from https://www.merck.com/news/merck-to-initiate-phase-3-trials-for-investigational-once-monthly-hiv-prevention-pill/

[2] Merck sends new monthly oral PrEP to Phase 3 after earlier islatravir setback. Retrieved July 14, 2025 from https://endpoints.news/ias25-merck-sends-new-monthly-oral-prep-to-phase-3-after-earlier-islatravir-setback/

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