Immune Cell Decreases Halt Merck’s Dual-Agent Antiretroviral HIV Study

Citing declining lymphocyte and T-cell counts in some patients, Merck has stopped its phase 2 trial of a dual-agent HIV antiretroviral regimen and is probing similar studies for this concerning safety signal.

The IMAGINE-DR trial is looking at the combination of two experimental agents: MK-8591, a nonnucleoside reverse transcriptase inhibitor, and islatravir, a nucleoside reverse transcriptase translocation inhibitor. Islatravir was being tested as a once-weekly oral treatment in adults with HIV-1 who have been virologically suppressed for greater than or equal to six months.

Islatravir has just come off two positive pivotal phase 3 studies; it’s under evaluation in more than 10 clinical trials.

Decreases in populations of both immune cells appeared to be dose-related, with the greatest associated with the highest doses of MK-8591 (200 mg and 400 mg).  An independent Data Monitoring Committee said the combination of the two drugs was problematic and ordered the halt. The company paused the molecule’s developmental program and has stopped dosing patients.