Key Takeaways Merck has begun Phase III trials of MK-8527, a once-monthly pill for HIV pre-exposure prevention. The studies will enroll nearly 9,000 participants and compare MK-8527 to Gilead's daily Truvada pill. MK-8527 follows positive Phase II data and is part of Merck's broader push into HIV prevention and treatment.Merck (MRK) recently launched two late-stage clinical studies to evaluate MK-8527, its investigational once-monthly oral pill for HIV pre-exposure prophylaxis (PrEP).The EXPrESSIVE-11 stu ...