Merck Enters HIV PrEP Arena with New Phase 3 Trials, Challenging Gilead's Dominance

Merck & Co. is making a bold move into the HIV pre-exposure prophylaxis (PrEP) market with the launch of two phase 3 trials for its once-monthly oral medication, MK-8527. This development comes as Gilead Sciences' twice-yearly injectable, Yeztugo (lenacapavir), has recently gained approval and is set to dominate the HIV prevention landscape.

Merck's Strategic Push into HIV Prevention

Merck, in collaboration with the Gates Foundation, is initiating two large-scale phase 3 trials:

1. EXPrESSIVE-10: Targeting women and girls across 31 sites in Kenya, South Africa, and Uganda.
2. EXPrESSIVE-11: Focusing on sexually active individuals from 16 countries.

Both trials aim to enroll approximately 4,400 participants and will compare MK-8527's efficacy in reducing HIV incidence against Gilead's daily PrEP pill, Truvada (emtricitabine/tenofovir).

The Gates Foundation is providing significant support, including grant funding to the International Clinical Research Center (ICRC) at the University of Washington and the University of Alabama at Birmingham. This funding will facilitate community advisory groups, patient recruitment, and retention efforts for both trials.

Scientific Advancements and Market Dynamics

MK-8527 operates by inhibiting the reverse transcriptase enzyme crucial for HIV replication. Merck recently concluded a phase 2 trial of the drug, reporting similar adverse event rates between treatment and placebo arms. More comprehensive data from this study is scheduled for presentation at the AIDS Society Conference on HIV Science in Rwanda on July 16.

While Gilead's Yeztugo has been hailed as a scientific breakthrough with projected peak sales of $8 billion annually, Merck is banking on a segment of the population that may prefer oral medication over injections. Trevor Mundel, Ph.D., president of global health at the Gates Foundation, emphasized the urgent need for diverse PrEP options, stating, "With only 18% of global PrEP need currently met, there is a clear and urgent need for options like MK-8527 that may offer the ability to prevent infection."

Shifting Landscape in HIV Prevention

The HIV prevention field is experiencing rapid evolution. On July 14, the World Health Organization updated its HIV prevention guidelines to recommend Yeztugo, with Director-General Tedros Adhanom Ghebreyesus, Ph.D., referring to lenacapavir as the "next best thing" in the absence of an HIV vaccine.

As Merck wades deeper into these waters, the pharmaceutical industry watches closely to see how this competition will shape the future of HIV prevention and potentially expand access to critical medications globally.