Compounds / MK-677

MK-677

Also known as: Ibutamoren, Ibutamoren mesylate, MK-0677, L-163191

Established human clinical Not FDA-approved · not a peptide Category: Growth Hormone Secretagogues

The compounds described in this library are research-use-labeled chemicals and are not FDA-approved for human use. This content is factual scientific reference drawn from published literature. It is not medical, dosing, or purchasing advice. VialReport does not sell, supply, or distribute any compound.

Short summary

An orally active growth hormone secretagogue. Despite being sold alongside peptides and grouped with them in the market, it is not a peptide: it is a non-peptide small molecule. It went through substantial pharmaceutical development but was never approved.

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Origin and Development

Developed by Merck as an orally bioavailable growth hormone secretagogue. It was investigated across several indications, including growth hormone deficiency, frailty in older adults, and muscle wasting. Development was not carried through to approval.

Mechanism as Understood in the Literature

Ghrelin receptor (GHS-R1a) agonist. It mimics the action of ghrelin at the pituitary, producing sustained elevation of growth hormone and IGF-1, and is orally active, which distinguishes it sharply from the injectable peptides it is sold alongside.

Research Status

Better characterized in humans than most compounds in this library. Multiple randomized controlled trials were conducted during its development program, including studies in older adults examining effects on growth hormone, IGF-1, body composition, and functional outcomes. It nonetheless never received approval.

Regulatory status

Not FDA-approved for any indication. Prohibited in competitive sport under World Anti-Doping Agency rules. Note that as a non-peptide small molecule its regulatory treatment differs from that of the peptide compounds in this library. [VERIFY BEFORE PUBLICATION: FDA 503A/503B bulk drug substances status for ibutamoren mesylate, including any identified safety concerns.]

Commonly Confused With

Routinely listed and sold as a peptide. It is not. MK-677 is a spiropiperidine small molecule, orally active, structurally unrelated to the peptide secretagogues it shares shelf space with. It is functionally comparable to them in that it acts on the same receptor, which is why the categories get blurred.

How This Compound Is Marketed

Vendor marketing for this compound typically references growth hormone support, appetite, sleep, and body composition. VialReport does not evaluate or endorse these claims. See Research Status above for what the published literature actually establishes.

Analytical Profile

A non-peptide small molecule, and the salt form matters. Ibutamoren free base (CAS 159634-47-6) has a molecular weight of approximately 528.7 Da, formula C27H36N4O5S. Ibutamoren mesylate (CAS 159752-10-0) adds a methanesulfonate component and has a molecular weight of approximately 624.8 Da. Testing and label-claim calculations must specify which form is present, since a milligram figure means different things depending on which is in the vial. Because it is not a peptide, a generic peptide RP-HPLC method should not be assumed suitable. Small molecules are routinely analyzed by HPLC, but the method, wavelength, reference standard, and impurity panel must be validated for this molecule and this form.

Stability and Handling

Typically supplied as a powder or in solution. Small molecules of this type are generally more stable than peptides, both in storage and in solution.

Key Literature

  1. 01 Nass R, et al. Effects of an oral ghrelin mimetic on body composition and clinical outcomes in healthy older adults: a randomized trial. Ann Intern Med. 2008;149(9):601-611.
  2. 02 Murphy MG, et al. MK-677, an orally active growth hormone secretagogue, reverses diet-induced catabolism. J Clin Endocrinol Metab. 1998;83(2):320-325.

VialReport publishes factual reference information and independent test data. Nothing here is medical, dosing, or purchasing advice.

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