Merck Stops Enrolling Participants in Islatravir HIV Trials

Merck’s islatravir-based HIV antiretroviral program has hit another bump in the road, with the company pausing enrollment in two phase 3 studies that are key to advancing the once-a-month oral regimen.

Details from the company were sketchy, but the change appears related to decreases in lymphocyte and CD4+ T-cell counts associated with islatravir, an investigational nucleoside reverse transcriptase translocation inhibitor.

An external data monitoring committee recommended the halt to enrollment in IMPOWER 22 and IMPOWER 24, according to the company. Those already enrolled will continue to receive treatment, but investigators will be looking at the cell counts more frequently.

Both IMPOWER studies are comparing once-monthly islatravir to once-daily emtricitabine/tenofovir disoproxil fumarate as pre-exposure prophylaxis in cisgender women at high risk for HIV-1 Infection.