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MK-677 (Ibutamoren)

MK-677 (ibutamoren mesylate, CAS 159752-10-0) is a non-peptide, orally bioavailable small-molecule agonist of the ghrelin receptor (GHS-R1a) with a molecular weight of approximately 624.8 Da and formula C₂₇H₃₆N₄O₅S (mesylate salt). As a spiroindoline sulfonamide compound, MK-677 was developed as a peptidomimetic alternative to injectable GH secretagogue peptides. It is a widely used research tool for studying sustained ghrelin receptor activation, continuous GH/IGF-1 elevation, and metabolic effects of prolonged GHS-R1a agonism.

Technical Specifications

Property Value
CAS Number 159752-10-0
Molecular Formula C₂₇H₃₆N₄O₅S (mesylate salt)
Molecular Weight ~624.8 Da
Purity ≥98% (HPLC-verified)
Appearance Lyophilized white powder
Solubility Soluble in DMSO, ethanol; limited aqueous solubility
Storage -20°C (lyophilized), 2–8°C (reconstituted)

Mechanism of Action

MK-677 binds as a high-affinity agonist to the growth hormone secretagogue receptor type 1a (GHS-R1a), mimicking the actions of the endogenous ligand ghrelin. Upon GHS-R1a activation, Gαq-mediated PLC signaling generates IP₃ and DAG, mobilizing intracellular calcium stores and activating PKC in hypothalamic arcuate nucleus neurons and pituitary somatotrophs. This calcium-dependent pathway stimulates pulsatile GH secretion while simultaneously inhibiting somatostatinergic tone. Additionally, MK-677 activates hypothalamic NPY/AgRP neurons, contributing to appetite stimulation. Unlike injectable peptide ghrelin mimetics (GHRP-2, GHRP-6), MK-677's oral bioavailability and extended half-life (~4–6 hours) produce sustained GHS-R1a occupancy and prolonged GH and IGF-1 elevation over 24-hour periods. The compound also demonstrates functional selectivity at GHS-R1a, with a biased signaling profile that favors Gαq over β-arrestin recruitment, which may influence the pattern of GH secretion relative to peptide agonists. Importantly, MK-677 does not suppress endogenous GH pulsatility completely, preserving some degree of physiological GH secretory dynamics.

Research Applications

  • Primary: Oral ghrelin receptor pharmacology — sustained GHS-R1a activation, continuous GH/IGF-1 elevation
  • Secondary: Body composition and metabolism research, appetite and feeding behavior studies, bone turnover and nitrogen balance models
  • Model Systems: In vitro (GHS-R1a-transfected cell lines, radioligand binding), in vivo (oral administration pharmacokinetic/pharmacodynamic models, GH/IGF-1 axis studies)

Quality Control & Analytical Methods

  • HPLC: ≥98% purity verification at 214/220 nm (C18 reversed-phase column)
  • Mass Spectrometry: ESI-MS for molecular weight confirmation (~624.8 Da)
  • Peptide Content: AAA not applicable (non-peptide small molecule); HPLC purity by area %
  • Endotoxin: <1 EU/mg (LAL assay)
  • TFA Content: Not applicable (non-peptide)

Stability & Storage

Condition Stability
-20°C (lyophilized) 24 months
4°C (lyophilized) 6 months
25°C (lyophilized) 1 month
Reconstituted (4°C) 7 days
Reconstituted (-20°C) 30 days

Key Research References

  • Murphy et al. (1998) — Long-term treatment with the oral GH secretagogue MK-677 increases pulsatile GH secretion and IGF-I. J Clin Endocrinol Metab. PMID: 9626137
  • Chapman et al. (1997) — Stimulation of the growth hormone and insulin-like growth factor I by MK-677 in healthy adults. J Clin Endocrinol Metab. PMID: 8989277
  • Patchett et al. (1995) — Design and biological activities of L-163,191 (MK-0677), a potent orally active ghrelin receptor agonist. Proc Natl Acad Sci USA. PMID: 7602044

Source & Purchase

For researchers requiring research-grade MK 677 with full analytical documentation including HPLC, LC-MS, and Certificate of Analysis, visit the HK Peptides product page for specifications, bulk pricing, and ordering.

View MK 677 Product →

FAQ

Q: What purity level is standard for MK-677? A: HK Peptides supplies MK-677 at ≥98% purity by HPLC with full COA documentation.

Q: How should MK-677 be stored for research use? A: Lyophilized MK-677 should be stored at -20°C. Reconstituted solutions at 4°C for short-term use (up to 7 days).