Also known as Ibutamoren · Ibutamoren mesylate · MK-0677 · L-163,191
An orally active, non-peptide ghrelin-receptor agonist and growth-hormone secretagogue — a small molecule catalogued alongside the GH peptides.
Research refreshed
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.
Oral GHS-R1a (ghrelin receptor) agonism → sustained increase in GH and IGF-1.
Behind every vial of MK-677 is the same exacting pipeline every research peptide runs — but the chemistry plays out differently for this molecule. Here is how MK-677, specifically, is brought into being.
On paper, MK-677 is C27H36N4O5S — about 528.67 daltons of precisely arranged atoms. Before a single bond is made, the target sequence, salt form, and purity threshold are written down as the contract the finished material must meet.
MK-677 is assembled by solid-phase peptide synthesis — the chain grows one protected residue at a time on resin, and what you fail to build cleanly here you pay to remove later.
The crude mixture — MK-677 plus its deletions and side products — is then separated on preparative HPLC, and where the cut is taken decides the difference between a genuinely pure peptide and a barely-passable one.
A real batch of MK-677 proves itself: identity confirmed by mass spectrometry against its ~528.67 Da, purity read directly off an analytical HPLC trace, water and counterion content measured. That batch-specific certificate of analysis is the only honest way to know what is actually in a vial of MK-677 — and a short, cold, accountable chain of custody is how that purity survives the trip to your bench.
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.
Don't judge a vial by its cake. A fluffy, good-looking lyophilized powder reflects bulking agents and freeze-drying parameters — not purity. Insist on a batch-specific certificate of analysis.
Recent clinical trials and publications mentioning MK-677, pulled automatically from ClinicalTrials.gov and PubMed and refreshed daily. Listings are unfiltered search results, not curated endorsements.
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.
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.
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.
No — it reached late-stage trials but was never approved, and it is prohibited in sport. This page is a research and educational reference.
Recombinant 191-amino-acid human growth hormone — a folded protein biologic identical in sequence to pituitary GH, not a synthetic research peptide.
ViewThe downstream effector of growth hormone — a 70-amino-acid recombinant protein, structurally a cousin of proinsulin, that carries out most of GH’s growth signal.
ViewA long-acting modified IGF-1 analog with reduced IGFBP binding and prolonged systemic activity.
ViewDosing protocols, mechanism, comparisons, and the latest trials — citation-backed answers grounded in PubMed, PubChem, and ClinicalTrials.gov.