Non-Peptide GH Secretagogue / Ghrelin Receptor Agonist
MK-677 (Ibutamoren) Research Compound
MK-677, also known as Ibutamoren (INN) or MK-0677, is an orally active, non-peptide growth hormone secretagogue (GHS) that acts as a potent, selective agonist of the ghrelin receptor (GHS-R1a). Unlike peptide GHS compounds such as GHRP-2, GHRP-6, and Ipamorelin, MK-677 is not subject to proteolytic degradation, enabling extended receptor occupancy in research settings.
Compound identity
- Name
- MK-677 (Ibutamoren)
- Class
- Non-Peptide GH Secretagogue / Ghrelin Receptor Agonist
- CAS number
- 159752-10-0
- Molecular formula
- C₂₇H₃₆N₄O₅S
- Also known as
- Ibutamoren, MK-0677, L-163,191, Oratrope
Research context
MK-677 (CAS 159752-10-0, MW 624.77 Da, C₂₇H₃₆N₄O₅S free base) belongs to the spiroindoline class of GHS-R1a agonists, developed by Merck Research Laboratories in the 1990s. It binds the ghrelin receptor with nanomolar affinity and mimics the action of ghrelin — an endogenous peptide hormone produced primarily in the stomach — to stimulate the secretion of growth hormone (GH) from the pituitary gland. Unlike endogenous ghrelin, MK-677 is resistant to enzymatic degradation and has an oral bioavailability profile that makes it valuable as a research probe for the GH/IGF-1 axis.
Pharmacological research on MK-677 has examined its capacity to increase both pulse amplitude of endogenous GH secretion and circulating IGF-1 concentrations. Smith et al. (Science, 1998) characterized the compound's receptor pharmacology and demonstrated GH-releasing activity in animal models. Subsequent clinical research — including Nass et al. (Journal of Clinical Endocrinology & Metabolism, 2008) — investigated MK-677 in older adults over extended periods, reporting sustained increases in serum IGF-1. Research by Copinschi et al. (Sleep, 1997) examined effects on sleep architecture in a research cohort, finding changes in slow-wave sleep patterns. Svensson et al. (1998) and others studied nitrogen balance effects under caloric restriction. These properties make MK-677 a widely used pharmacological tool for investigating GHS-R1a receptor biology and GH/IGF-1 axis modulation.
As a research reagent, MK-677 is used in studies of GHS-R1a receptor pharmacology, GH pulse physiology, IGF-1-axis regulation, and metabolic signaling. DMV Research supplies MK-677 as a lyophilized compound with per-batch third-party Certificate of Analysis confirming identity by HPLC-MS and purity ≥99% by HPLC.
Frequently asked questions
What is MK-677 (Ibutamoren)?+
MK-677 (Ibutamoren, CAS 159752-10-0) is a non-peptide, orally active agonist of the ghrelin receptor (GHS-R1a). It stimulates endogenous GH secretion from the pituitary and elevates circulating IGF-1 in preclinical and clinical research models. Unlike peptide GH secretagogues (GHRP-2, Ipamorelin), MK-677 is a small molecule belonging to the spiroindoline chemical class and is resistant to proteolysis.
How does MK-677 differ from GHRP-2, GHRP-6, and Ipamorelin?+
All four compounds act on the GHS-R1a (ghrelin receptor), but via different structural classes. GHRP-2, GHRP-6, and Ipamorelin are peptide GHS compounds — short amino-acid sequences — that are subject to proteolytic degradation and are typically administered by injection in research contexts. MK-677 is a non-peptide small molecule (spiroindoline class) with oral bioavailability and a longer half-life (~24 hours in human research subjects), enabling once-daily dosing protocols in studies. The receptor target and downstream signaling (GH and IGF-1 elevation) are mechanistically analogous across all four.
Is MK-677 a SARM?+
No. MK-677 is frequently and erroneously miscategorized as a selective androgen receptor modulator (SARM), but it has no affinity for the androgen receptor. MK-677 is a GH secretagogue — its mechanism involves the ghrelin receptor (GHS-R1a). It is structurally and mechanistically distinct from SARMs such as LGD-4033, RAD-140, or Ostarine, which exert their effects via androgen receptor binding.
Is MK-677 approved for human use?+
No. MK-677 is not FDA-approved for any indication. It was investigated in clinical trials for conditions including muscle wasting, growth hormone deficiency, and osteoporosis but was not brought to market. As supplied by DMV Research, it is for in-vitro and pre-clinical laboratory research purposes only, not for human consumption.
Research use only
All products are intended for laboratory and research use only (RUO) and are not for human consumption, ingestion, or any in-vivo use.
The statements on this page have not been evaluated by the FDA. MK-677 (Ibutamoren) is not intended to diagnose, treat, cure, or prevent any disease. Content is provided for laboratory research reference only.