Description
Ibutamoren (also catalogued as MK-677) is a non-peptide, orally active small molecule that functions as a selective agonist of the ghrelin receptor (growth hormone secretagogue receptor, GHSR) [7]. With a free-base molecular weight of approximately 528.68 Da and a mesylate salt form reaching roughly 624.78 Da, the compound occupies a structurally distinct niche among growth hormone secretagogues (GHSs) — one that does not share the peptide backbone common to agents such as GHRP-2 or GHRP-6 [5][6]. Its chemical architecture enables it to mimic the GH-stimulating action of the endogenous ligand ghrelin [7].
A defining pharmacological characteristic of ibutamoren is its capacity to promote pulsatile growth hormone release while preserving the negative-feedback mechanisms that normally regulate GH physiology [1]. Preclinical and early clinical research has also linked GHSR activation to elevated circulating levels of insulin-like growth factor 1 (IGF-1), making the compound a useful tool for investigators studying the GH/IGF-1 signaling axis [7][2].
Researchers have employed ibutamoren as a molecular probe across several investigative contexts, including studies of body composition parameters, bone metabolism, appetite-related signaling, and anabolic biomarkers in preclinical and early-stage human research models [2][3]. Beyond the endocrine axis, a separate line of inquiry has explored the compound's interactions with G protein-coupled receptor pathways in the context of viral replication models — an antiviral screening study identified ibutamoren as a hit compound against Ebola virus-like particles in cell-based assays, attributing activity to its GHSR agonism [4]. Together, these research threads illustrate the breadth of mechanistic questions that investigators have pursued using ibutamoren as a chemical tool.
References
[1] The Safety and Efficacy of Growth Hormone Secretagogues. Sexual Medicine Reviews, 2018. https://pubmed.ncbi.nlm.nih.gov/28400207/
[2] Beyond the androgen receptor: the role of growth hormone secretagogues in the modern management of body composition in hypogonadal males. Translational Andrology and Urology, 2020. https://pubmed.ncbi.nlm.nih.gov/32257855/
[3] LGD-4033 and MK-677 use impacts body composition, circulating biomarkers, and skeletal muscle androgenic hormone and receptor content: A case report. Experimental Physiology, 2022. https://pubmed.ncbi.nlm.nih.gov/36303408/
[4] Antiviral activity of sertindole, raloxifene and ibutamoren against transcription and replication-competent Ebola virus-like particles. BMB Reports, 2020. https://pubmed.ncbi.nlm.nih.gov/31964466/
[5] IBUTAMOREN MESYLATE (ChEMBL CHEMBL2105872). ChEMBL, European Bioinformatics Institute. https://www.ebi.ac.uk/chembl/compound_report_card/CHEMBL2105872/
[6] IBUTAMOREN (ChEMBL CHEMBL13817). ChEMBL, European Bioinformatics Institute. https://www.ebi.ac.uk/chembl/compound_report_card/CHEMBL13817/
[7] Ibutamoren. Wikipedia. https://en.wikipedia.org/wiki/Ibutamoren
