After the external data monitoring committee's recommendation, Merck & Co Inc MRK has paused in enrollment for the IMPOWER 22 (MK-8591-022) and IMPOWER 24 (MK-8591-024) Phase 3 studies evaluating islatravir (ISL) for pre-exposure prophylaxis (PrEP) in people at high risk of HIV-1 infection.

• Merck will conduct further analyses of these and other ongoing studies. 
• Participants already enrolled in the trials will continue to receive the study medicine. 
• Informed by the committee's recommendations, Merck is implementing additional monitoring measures for study participants, including increasing the frequency of total lymphocyte and CD4+ T-cell assessments. 
• Islatravir (MK-8591) is a once-monthly investigational nucleoside reverse transcriptase translocation inhibitor under evaluation for the treatment and prevention of HIV-1.
• Related Link: Gilead, Merck Stop Enrollment In Mid-Stage HIV Combination Therapy Trial.
• Price Action: MRK shares are down 0.50% at $73.05 during the premarket session on the last check Tuesday.