Description
MK-677 has several names. These include Ibutamoren and MK-0677. Its molecular formula is C27H36N4O5S. The molecular weight is 528.67 g/mol. The CAS number is 159752-10-0. Sigma-Aldrich sells it as a research powder. The purity is ≥98% (HPLC).
Mechanism of Action
MK-677 acts as a potent ghrelin receptor agonist. It is orally-active. The compound binds to the growth hormone secretagogue receptor (GHS-R1a). This binding mimics ghrelin’s natural action. Consequently, the pituitary gland releases more GH. This GH then travels to the liver. There, it stimulates IGF-1 synthesis. Importantly, IGF-1 mediates most of GH’s anabolic effects. These effects occur on muscle, bone, and adipose tissue.
Research and Clinical Applications
Potential Therapeutic Uses
Merck originally developed MK-677 as an investigational drug. Researchers studied it for various conditions. First, they explored it for growth hormone disorders in children. Second, they investigated it for frailty in older adults. Additionally, they studied it for hip fracture recovery. Finally, they examined it for reversing diet-induced catabolism.
Clinical Trial Findings
A 2-year trial examined healthy older adults. The MK-677 group gained 1.1 kg of fat-free mass. Conversely, the placebo group lost 0.5 kg (P < 0.001). Body weight increased 2.7 kg in the MK-677 group. However, the placebo group only gained 0.8 kg (P = 0.003). Importantly, fasting blood glucose increased by 0.3 mmol/L (P = 0.015). Insulin sensitivity also decreased.
A hip fracture trial (Phase IIb) showed promising results. IGF-1 increased by 51.4 ng/ml (P < 0.001). Gait speed improved significantly. Nevertheless, the trial ended early. A safety signal of congestive heart failure occurred. This affected a limited number of patients.
Safety and Side Effect Profile
Documented Adverse Effects
MK-677 carries significant side effect risks. Common side effects include insulin resistance. Increased appetite is also common. Weight gain occurs frequently. Swelling due to water retention is another concern. A 2025 case report documented hepatotoxicity. A healthy 30-year-old man experienced transaminitis. He used MK-677 for two months. Fortunately, liver function returned to normal. This occurred after he stopped using the supplement.
Long-Term Safety Concerns
Long-term use may increase type 2 diabetes risk. Elevated IGF-1 levels may contribute to tumor growth. Importantly, MK-677 remains an investigational drug. It is not FDA-approved for human consumption. Therefore, researchers should exercise caution.
Legal Status and Regulatory Actions
World Anti-Doping Agency (WADA)
WADA places MK-677 on its prohibited list. Consequently, professional athletes cannot use it. The ban applies during and outside competition.
Regulatory Status in China
China includes MK-677 in its doping control lists. This applies to both 2024 and 2026 lists. The government classifies it as a peptide hormone. Therefore, it falls under the same rules as WADA. Legal pharmaceutical channels do not offer it in China.
Internal and External Links
Internal Resources
Visit our Research Chemical Library for related compounds. Explore our Guide to Growth Hormone Secretagogues. Review our Safety Protocols and Regulatory Compliance FAQ.
External Resources
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[Get Smart About Drugs (.gov)]: Read the official health warning at Get Smart About Drugs.
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[PubMed]: Access clinical trials and research articles at PubMed.
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[ScienceDirect]: Read the Phase IIb hip fracture trial at ScienceDirect.
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[Sigma-Aldrich]: View chemical data for CAS 159752-10-0 at Sigma-Aldrich.
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[WADA]: Check the prohibited list at WADA.
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