MK-677

Ibutamoren

Grade B: Human evidence, not approved for this use

TL;DR: MK-677 (ibutamoren) is a non-peptide small molecule that mimics ghrelin at the GH secretagogue receptor; it is orally bioavailable, which distinguishes it from peptide secretagogues. Multiple human RCTs have been conducted, including studies in older adults examining bone turnover, sleep quality, and GH-axis stimulation, and a randomized trial in Alzheimer's disease that found no clinical benefit on cognitive progression. The evidence base is broader than most compounds in the wellness peptide category, but no positive phase III RCT leading to regulatory approval has been completed, and the compound's development was not submitted for FDA approval. The evidence is insufficient to support therapeutic claims.

Key Takeaways

Grade B: Human evidence, not approved for this use
Not FDA approved: Not FDA-approved for any indication; FDA has specifically cited a congestive heart failure safety signal from a stopped clinical trial.
Compounding: The FDA placed MK-677 in Category 2 of its interim 503A/503B bulk-substances policy, the list of substances it has identified as presenting potential significant safety risks, so it is not eligible for routine pharmacy compounding.

MK-677 chemical structure — Structure via PubChem CID 6450830

Mechanism

MK-677 acts as a non-peptide agonist at the ghrelin receptor (GHSR-1a), stimulating pulsatile GH release from the pituitary and subsequently elevating circulating IGF-1.

Evidence

MK-677 (ibutamoren) is a non-peptide small molecule that mimics ghrelin at the GH secretagogue receptor; it is orally bioavailable, which distinguishes it from peptide secretagogues. Multiple human RCTs have been conducted, including studies in older adults examining bone turnover, sleep quality, and GH-axis stimulation, and a randomized trial in Alzheimer's disease that found no clinical benefit on cognitive progression. The evidence base is broader than most compounds in the wellness peptide category, but no positive phase III RCT leading to regulatory approval has been completed, and the compound's development was not submitted for FDA approval. The evidence is insufficient to support therapeutic claims.

Safety and risks

MK-677 carries a documented serious safety signal that must be prominently disclosed: a phase IIb clinical trial was stopped early after a higher rate of congestive heart failure was observed in the treated group compared to placebo. The FDA has cited this signal in compounding safety communications. Additional concerns include insulin resistance and blood glucose elevation from sustained IGF-1 and GH elevation, fluid retention, and potential effects on undiagnosed malignancies due to IGF-1's growth-promoting properties. Long-term safety is not established. As a non-peptide small molecule, MK-677 does not fit neatly into the FDA's peptide compounding framework; it is not FDA-approved and has no established legal compounding pathway under 503A or 503B. This compound should not be used without awareness of the congestive heart failure signal.

Interactions

IGF-1 elevation may worsen insulin resistance; concurrent use with insulin or antidiabetic medications warrants caution. Potential for interaction with other GH-axis agents. No formal drug interaction studies have been published.

Federal compounding status

503A/503B Category 2: significant safety risk as of 2023.

The FDA placed this substance (503A) in Category 2 of its interim bulk-substances policy, the list it has identified as presenting potential significant safety risks, so it is not eligible for routine pharmacy compounding. FDA source

Federal status only, from public FDA records. State pharmacy-board rules vary and are not covered here. This is regulatory reporting, not legal advice. All compounds.

Compounding legality

The FDA placed MK-677 in Category 2 of its interim 503A/503B bulk-substances policy, the list of substances it has identified as presenting potential significant safety risks, so it is not eligible for routine pharmacy compounding.

Sources

MK-677 is Not FDA approved. PeptideGrids presents evidence and regulatory status for informational purposes only. We do not sell, supply, source, or help anyone obtain this compound, and we provide no dosing or administration guidance. This is not medical advice; consult a licensed clinician. Full disclaimer.

Last reviewed June 1, 2026 by PeptideGrids editorial team (independently audited).