Non-peptide / not FDA-approved

MK677

NOT A PEPTIDE — oral GHSR agonist ibutamoren (CID 178024 / mesylate 6450830); ≠ GHRPs.

Editorial review:

What evidence says

Evidence snapshot

This drawer marks papers. It is not a plan, a dose, or a source. A paper is a bounded report. It is not a protocol. Grades name the object. They are not a safety rating.

Identity lock — NOT A PEPTIDE. MK-677 / MK-0677 (ibutamoren) is an orally active non-peptide ghrelin-receptor (GHSR) agonist / growth-hormone secretagogue. Free-base PubChem CID 178024; formula C27H36N4O5S / MW 528.7; CAS 159634-47-6. Clinical material is often the mesylate salt (PubChem CID 6450830; formula C28H40N4O8S2 / MW 624.8). ≠ GHRP-2/6, ≠ hexarelin, ≠ ipamorelin, ≠ ghrelin peptide. Included in this peptide-site evidence wave only as an evidence-drawer neighbor because secretagogue conversations conflate it with peptides — framing must say small molecule. No approved adult body-composition indication assumed in this pack. This drawer marks papers. It is not use advice.

Bottom line

Multiple 1990s–2000s clinical studies show oral ibutamoren stimulates the GH/IGF-I axis in elderly, obese, and selected GH-deficient adults; Nass 2008 is a notable randomized older-adult body-composition/clinical-outcomes trial; Adunsky 2011 Phase IIb hip-fracture recovery was a late clinical attempt with important limitations. Axis stimulation ≠ approved physique drug. Refuse “oral peptide” mislabeling.

Papers

Foundational human GH/IGF-I axis studies

PMID 8954023 — Chapman 1996

Tested: daily oral MK-677 stimulation of the GH/IGF-I axis in healthy elderly subjects.

Does not show: an approved sarcopenia drug label or peptide identity.

PMID 9329386 — Chapman 1997

Tested: oral MK-677 stimulating GH/IGF-I in selected GH-deficient adults.

Does not show: replacement equivalence to injectable GH for all GH-deficiency indications.

PMID 9467534 — Murphy 1998

Tested: MK-677 reversing diet-induced catabolism (human metabolic ward-style secretagogue study).

Does not show: athletic performance approval.

PMID 9467542 — Svensson 1998

Tested: two-month oral MK-677 in obese subjects — GH secretion, fat-free mass, energy expenditure endpoints.

Does not show: a modern obesity indication or fat-loss guarantee; read endpoints as reported.

PMID 10404019 — Murphy 1999

Tested: oral MK-677 on bone-turnover markers in healthy and functionally impaired elderly adults.

Does not show: fracture-prevention approval by itself.

PMID 11238495 — Murphy 2001

Tested: alendronate and MK-677, alone and combined, on bone-turnover markers and BMD.

Does not show: that MK-677 replaces bisphosphonate therapy.

Later randomized / late-phase clinical

PMID 18981485 — Nass 2008

Tested: randomized trial of an oral ghrelin mimetic (ibutamoren) on body composition and clinical outcomes in healthy older adults.

Does not show: FDA approval for aging or sarcopenia; still a key human evidence anchor.

PMID 21067829 — Adunsky 2011

Tested: multicenter randomized placebo-controlled Phase IIb of MK-0677 (ibutamoren mesylate) in patients recovering from hip fracture.

Does not show: a registered hip-fracture recovery indication from this program’s public narrative; grade limitations honestly in Status.

PMID 11452249 — Codner 2001

Tested: oral ibutamoren mesylate effects on the GH/IGF-I axis in children with GH deficiency framing (pediatric clinical pharmacology).

Does not show: adult physique use; pediatric endocrine context only.

Mechanism / class context

PMID 15814848 — Smith 2005

Tested: Endocrine Reviews development history of growth-hormone secretagogues (places ibutamoren among non-peptide GHS).

Does not show: peptide identity for MK-677.

PMID 34737341 — Liu 2021

Tested: structural basis of human ghrelin receptor signaling by ghrelin and the synthetic agonist ibutamoren.

Does not show: clinical outcomes; confirms non-peptide agonist chemistry.

What is not established

That MK-677 is a peptide. Approved adult bodybuilding, anti-aging, or fat-loss indication. Equivalence to injectable GH or to GHRP/GHRH peptides. Long-term safety of unregulated internet ibutamoren. Product identity for gray-market “MK677.” This drawer does not provide use advice, schedules, or sourcing.

Selected sources

8954023 9329386 9467534 9467542 10404019 11238495 18981485 21067829 11452249 15814848 34737341

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