What Is MK-677? Benefits, Research & Safety

MK-677 was developed by Merck Research Laboratories in the mid-1990s as part of an effort to create orally active growth hormone secretagogues. The compound emerged from structure-activity relationship studies on non-peptide ghrelin mimetics capable of stimulating GH release via the GHS-R1a receptor. The compound was initially designated L-163,191 before receiving the Merck code MK-677 and the International Nonproprietary Name (INN) ibutamoren. Early pharmacological studies demonstrated that MK-677 could produce dose-dependent increases in GH and IGF-1 when administered orally, which was a significant advancement over injectable peptide alternatives. Phase I and Phase II clinical trials were conducted throughout the late 1990s and 2000s, examining MK-677 in populations including elderly adults, obese individuals, children with GH deficiency, and patients with hip fractures. The compound consistently elevated GH and IGF-1 levels, with secondary benefits observed for body composition, sleep quality, and bone density. However, the HORIZON study in elderly patients with heart failure was terminated early due to a trend toward increased cardiac events, and consistent findings of insulin resistance across multiple trials raised safety concerns. These issues, combined with the availability of recombinant GH therapy, led Merck to discontinue clinical development. Despite never receiving regulatory approval, MK-677 became widely available in the research chemical market and gained popularity due to its oral convenience and potent GH-elevating effects.