MK-677 (Ibutamoren)

1 Identity

Free-base CAS 159634-47-6 and mesylate CAS 159752-10-0 noted as commonly published but not independently verified. Class descriptors include growth hormone secretagogue and ghrelin receptor agonist.

Sequence

No defined sequence - not a peptide. The structural statement that replaces a sequence: a spiro[indoline-3,4'-piperidine] core bearing a METHANESULFONAMIDE on the indoline nitrogen, acylated at the piperidine nitrogen by a 2-amino-2-methylpropanamido-substituted 3-(indol-3-yl)propanoyl group, i.e. A primary alpha,alpha-dimethyl amino-amide at the end of a tryptophan-derived fragment. One defined stereocenter, (2R), on the tryptophan-derived carbon; the spiro carbon is not a stereocenter because the piperidine ring is symmetric about it. Although built in part from a tryptophan-derived building block, this is not a peptide and no peptide test has meaning for it: no amino acid numbering, no end-caps, no net peptide content assay, no amino acid analysis and no peptide counterion assay applies, and any of them appearing on a certificate shows the document was written from the wrong template.

Molecular formula

C27H36N4O5S (free base). C28H40N4O8S2 (methanesulfonate salt, 1:1), equivalently written C27H36N4O5S . CH3SO3H.

Average mass

528.67 Da free base (C27H36N4O5S); the formula on IUPAC 2021 abridged conventional atomic weights gives 528.668. Mesylate C28H40N4O8S2 = 624.77, and the formula gives 624.768, which matches the 624.77 printed on an institutional catalog listing to 0.002 Da. The arithmetic that matters commercially: the free base is 84.62 percent of the mesylate by weight, so one gram of mesylate is 846 mg base-equivalent and one gram of base-equivalent requires 1.182 g of mesylate. A certificate reporting 'MW 528.67' for material that is in fact the mesylate overstates content by 18.2 percent.

Monoisotopic mass

528.24064 Da neutral free base (C27H36N4O5S); [M+H]+ 529.24792. Mesylate formula unit 624.22876. The single most useful line on this record: mass spectrometry cannot settle the salt question. Electrospray of either form gives the protonated free base at m/z 529.248, because the methanesulfonate counterion is not in that ion. 'Mass confirms 529' is equally true of the free base and of the mesylate, and only ion chromatography for mesylate content with a declared stoichiometry closes it. All values follow from the stated formulas.

Salt / variant note

(1) the salt basis is the two-molecule split, and it is usually undeclared rather than fraudulent. Free base C27H36N4O5S, 528.67, CAS 159634-47-6; mesylate C28H40N4O8S2, 624.77, CAS 159752-10-0. One institutional supplier sells them as two distinct catalog items under the single name 'ibutamoren'. The base is 84.62 percent of the salt by weight; a certificate quoting 528.67 for mesylate material overstates content by 18.2 percent. (2) mass spectrometry cannot settle it: electrospray of either form gives m/z 529.248 for the protonated base, the counterion is not in that ion, and only ion chromatography with a declared stoichiometry closes the question. (3) the (2S) enantiomer: identical formula, identical average and monoisotopic mass to every decimal place, identical NMR in an achiral solvent, identical achiral HPLC retention. Nothing on an ordinary certificate distinguishes it, and the tryptophan-derived center is the one that epimerizes. (4) alkyl mesylate process impurities - methyl, ethyl and isopropyl methanesulfonate - formed when a mesylate salt meets a residual alcohol during isolation, and mutagenic-class impurities under ICH M7. These are the impurities a peptide-template certificate will not even look for. (5) presentation variants that are not the same article: one price index lists 327 sellers offering powder, capsule and liquid forms, and a capsule or a dosing solution is a formulated product with excipients, not a bulk substance releasable against a substance specification. (6) Polymorph and hydrate forms of the mesylate, which are not enumerated here because no supplier's form was qualified and which are made a supplier-qualification item rather than a stated variant.

2 Class & testing panel

Form

Single article

Testing panel

P6 — panel definition

3 Primary sources & evidence

The index reports the design and provenance of the literature, not a conclusion about effect.

Published literature exists and is unusually deep for a compound in this catalog, and almost all of it belongs to a sponsor rather than to the research channel. What exists, by study type and identifier. A Merck program through the 1990s produced multiple short-duration randomized endocrine studies in healthy and older adults. A two-year randomized placebo-controlled trial followed: Nass R et al., Annals of Internal Medicine 2008;149:601-611. A pediatric growth-hormone-deficiency program under the designation LUM-201 has run more recently under an active investigational new drug application with registered trials. Outcomes are deliberately not summarized: what the citation index records is that controlled human trials exist, are registered and are retrievable, with their identifiers. What does not exist is any controlled data on the oral research-channel presentations, and there is a substantial safety-signal and analytical-survey literature attached to those - the analytical surveys being the most directly relevant published work for a catalog record. Statements about which documents exist and their study type; no statement is made about what the compound does in a person.

4 Storage & specification

Storage

Off-white to pale solid, supplied as the mesylate salt, in a screw-cap amber borosilicate or HDPE container with a PTFE-lined closure, non-sterile, with no sterility claim. Store at 2 to 8 degrees C, desiccated over silica, protected from light, tightly closed. The mesylate is hygroscopic and water uptake shifts the assay directly, so the container closure is a specified item on the purchase order rather than a warehouse choice, a desiccant sachet travels in the secondary pack, and the container is equilibrated to ambient temperature before opening and closed immediately after weighing. Karl Fischer water is re-measured on any container opened more than three times. Solutions are prepared fresh; a dosing solution is not a storage form and is not prepared, held or shipped by this company in any presentation.

Shelf life

Provisional 36-month retest interval at 2 to 8 degrees C, desiccated and protected from light, stated as provisional pending the company's own stability data. Small molecules of this class are considerably more robust than the peptides in this catalog and the 36-month figure is an estimate that a 6-month accelerated ICH Q1A(R2)-style arm at 40 degrees C / 75 percent relative humidity plus a 24-month real-time arm replaces. The stability-indicating attributes are Karl Fischer water, assay on a declared basis, chiral purity, and the ICH M7 alkyl mesylates - chiral purity is included in the stability panel and not only at release, because epimerization would make the article a different compound without changing its mass or its achiral chromatogram.