# MK-677 > An orally active, non-peptide ghrelin-receptor agonist and growth-hormone secretagogue — a small molecule catalogued alongside the GH peptides. - Also known as: Ibutamoren, Ibutamoren mesylate, MK-0677, L-163,191 - Class: Growth Hormone - FDA approved: No - Canonical page: https://americanpeptide.com/catalog/mk-677 ## Overview MK-677 (ibutamoren) is a small molecule — not a peptide — that mimics ghrelin at the GHS-R1a receptor to raise growth hormone and IGF-1. Its defining feature is that it works by mouth and lasts about a day, where the peptide GH secretagogues must be injected — which is why it is almost always catalogued alongside them despite belonging to a different chemical class. MK-677 is the odd one out among growth-hormone secretagogues: chemically it is a non-peptide small molecule (a spiroindoline built for oral activity), yet functionally it does the same job as the GHRP peptides — it activates the ghrelin receptor to release growth hormone. It was developed by Merck in the 1990s in the search for an orally available GH secretagogue, and it succeeded where peptides could not: a single oral dose raises GH and IGF-1 for roughly 24 hours. That practicality is exactly why it sits in this catalog next to the peptide secretagogues — researchers treat them as interchangeable tools even though MK-677 is not a peptide. It has been studied in humans for body composition, bone density, and sleep, and reached late-stage trials (for example in older adults and for hip-fracture recovery) without gaining approval. It is a research compound, not FDA-approved, and prohibited in sport. ## Mechanism Oral GHS-R1a (ghrelin receptor) agonism → sustained increase in GH and IGF-1. ## Chemistry | Property | Value | | --- | --- | | Molecular formula | C27H36N4O5S | | Molecular weight | 528.67 Da | | CAS number | 159634-47-6 | | PubChem CID | [178024](https://pubchem.ncbi.nlm.nih.gov/compound/178024) | ## Research areas Studied in: GH/IGF-1 axis, Body composition, Bone density, Sleep. Guides on this site: - [Sleep & Circadian Rhythm](https://americanpeptide.com/research-areas/sleep-circadian): Peptides studied for sleep architecture and circadian regulation. - [Growth Hormone & Body Composition](https://americanpeptide.com/research-areas/growth-hormone-axis): Secretagogues studied for GH release, IGF-1, and body composition. ## Key research - Oral GH secretagogue — a non-peptide ghrelin-receptor agonist active by mouth, raising GH and IGF-1 for about 24 hours per dose. - Body composition — studied in humans for lean-mass and metabolic effects via sustained GH / IGF-1 elevation. - Bone & sleep — examined for bone-density and slow-wave-sleep effects in clinical research. - Not a peptide — a small molecule catalogued alongside the peptide secretagogues (ipamorelin, GHRP-2 / GHRP-6) for its shared mechanism. - Preclinical / prohibited in sport — reached late-stage trials without approval; WADA-banned; not FDA-approved. ## Storage, handling & synthesis **Synthesis.** MK-677 (ibutamoren) is a non-peptide small molecule made by conventional organic synthesis, not solid-phase peptide chemistry, and usually supplied as the mesylate salt. Its quality control is small-molecule-style — identity, related substances, residual solvents — rather than a peptide purity number. ## FAQs ### What is MK-677? MK-677 (ibutamoren) is an orally active, non-peptide ghrelin-receptor agonist that raises growth hormone and IGF-1 — a small molecule that does the same job as the injectable GHRP peptides. ### Is MK-677 a peptide? No. It is a small molecule, not a peptide, but it is catalogued alongside the peptide GH secretagogues because it shares their ghrelin-receptor mechanism and is used the same way. ### How is it different from GHRP-2 or ipamorelin? It hits the same receptor, but it is orally active and long-lasting (about 24 hours), whereas the GHRP peptides are injected and act in short pulses. ### Is MK-677 approved? No — it reached late-stage trials but was never approved, and it is prohibited in sport. This page is a research and educational reference. ## Latest research Recent trials and publications mentioning MK-677, pulled automatically from ClinicalTrials.gov and PubMed (unfiltered search results, refreshed daily). ### Recent trials - [Phase 3 Study of LUM-201 in Children With Growth Hormone Deficiency](https://clinicaltrials.gov/study/NCT06948214) — RECRUITING · PHASE3 · NCT06948214 - [The Impact of Ibutamoren on Nonalcoholic Fatty Liver Disease](https://clinicaltrials.gov/study/NCT05364684) — COMPLETED · PHASE2 · NCT05364684 - [Growth Hormone Secretagogue MK-0677's Effect on Lean Body Mass in Chronic Kidney Disease Stage 4/5 Subjects](https://clinicaltrials.gov/study/NCT01343641) — WITHDRAWN · PHASE2 · NCT01343641 - [Growth Hormone Secretagogue MK-0677 Effect on IGF-1 Levels in ESRD Patients](https://clinicaltrials.gov/study/NCT00395291) — COMPLETED · NA · NCT00395291 - [Treatment of Sarcopenia in Post-Hip Fracture Patients (0677-032)](https://clinicaltrials.gov/study/NCT00128115) — TERMINATED · PHASE2 · NCT00128115 - [Study of MK0677 for the Treatment of Alzheimer's Disease (0677-030)(COMPLETED)](https://clinicaltrials.gov/study/NCT00074529) — COMPLETED · PHASE2 · NCT00074529 --- Source: AmericanPeptide.com — https://americanpeptide.com/catalog/mk-677 Data license: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Attribution: AmericanPeptide.com. Research reference only — computational and educational content, not medical advice.