MK-677 (ibutamoren; code names MK-0677, LUM-201) is a synthetic low-molecular-weight compound used in scientific research as an oral growth-hormone secretagogue. Unlike peptide analogues of ghrelin or injectable forms of growth hormone, ibutamoren is a non-peptide molecule of the spiropiperidine class, resistant to digestive enzymes and therefore active when taken orally [1].

The compound draws researchers' attention because it mimics the action of endogenous ghrelin, the "hunger hormone," but with a much longer duration of action. This makes MK-677 a convenient tool for studying the growth-hormone and insulin-like growth factor-1 (GH-IGF-1) axis under controlled conditions.

What it is and its class

Chemically, MK-677 is not a peptide but a small organic molecule (empirical formula of the free base C27H36N4O5S, molar mass about 528.66 g/mol; CAS (Chemical Abstracts Service) registration number 159752-10-0). Research often uses the salt form, ibutamoren mesylate. Pharmacologically the compound is classified as an agonist of the ghrelin receptor (the growth-hormone secretagogue receptor, GHSR-1a) and a growth-hormone secretagogue. The key difference from ghrelin itself and from short secretagogue peptides is oral bioavailability and a half-life of about 24 hours, which allows once-daily dosing in research protocols [1][2].

Mechanism of action

MK-677 binds and activates the GHSR-1a receptor, located mainly in the hypothalamus and pituitary, the same receptor that natural ghrelin acts on. Activation of this receptor enhances the release of growth hormone from pituitary somatotrophs. An important feature that researchers note: the compound enhances the pulsatile, physiological pattern of growth-hormone secretion rather than creating a constantly elevated "flat" level, as happens with exogenous administration of growth hormone itself [2].

The rise in growth hormone in turn stimulates the production of insulin-like growth factor-1 (IGF-1), mainly in the liver. Because the mechanism works through the body's own regulatory loops (in particular negative feedback involving somatostatin), the secretion keeps elements of natural regulation. Through its affinity for the ghrelin receptor, the compound also affects appetite signals.

What the research shows

MK-677 has been studied in several clinical trials, mostly as a way to restore the age-related decline in growth-hormone secretion and to assess effects on body composition and functional measures.

  • Age-associated decline in GH/IGF-1. In early work, daily oral MK-677 in healthy older people over several weeks enhanced pulsatile growth-hormone secretion and raised serum GH and IGF-1 concentrations; at an appropriate dose, IGF-1 levels approached those of young adults [1].
  • Body composition in healthy older adults. A two-year randomised, double-blind, placebo-controlled study in healthy older participants examined the effect of daily ibutamoren on muscle mass, body composition, and functional outcomes [2].
  • Neurodegenerative disease. In a multicentre randomised trial in patients with Alzheimer's disease, MK-677 confirmed "target engagement" (a sustained rise in serum IGF-1) but did not slow disease progression compared with placebo [3].

Together these studies outline the compound's profile: a reliable rise in GH and IGF-1 (the biological target is confirmed), while clinical benefit for specific indications remains a research question. The data also point to the need to monitor metabolic parameters (in particular insulin sensitivity and glucose levels) in future studies.

Form and handling (research-use)

Longeva supplies MK-677 strictly as a research substance (reagent) with an accompanying certificate of analysis (COA) confirming the identity and purity of the batch. It is a reagent for laboratory and preclinical research, not a medicine; the compound is not intended to diagnose, treat, or prevent any disease in humans or animals.

Ibutamoren is a solid substance sensitive to moisture; it is usually stored in a tightly closed container, protected from light, at low temperature per the recommendations in the COA. Working solutions are prepared with proper concentration control. Handling the substance requires standard laboratory safety practices: use of PPE, work in a suitably equipped space, and documentation of batches by their origin and analytical data.