Setmelanotide is a synthetic cyclic peptide API and a selective melanocortin-4 receptor (MC4R) agonist used in the development and manufacture of medicines for rare genetic and hypothalamic forms of obesity. It is an analogue of the endogenous α-melanocyte-stimulating hormone (α-MSH) pathway and is designed to restore MC4R signaling involved in appetite regulation and energy balance. FDA and EMA product information identify setmelanotide as an 8-amino-acid cyclic peptide.
Setmelanotide is identified by CAS No. 920014-72-8, with the development codes RM-493 and BIM-22493. Its active-moiety/free-base molecular formula is C49H68N18O9S2, with a molecular mass of approximately 1117.3 Da. FDA identifies the marketed drug substance as setmelanotide acetate, while noting that the acetate salt contains approximately 2–4 molar equivalents of acetate.
Setmelanotide is an eight-residue cyclic peptide containing a disulfide linkage between the two cysteine residues. Its sequence is represented as Ac-Arg-Cys-D-Ala-His-D-Phe-Arg-Trp-Cys-NH2, with the cysteine residues forming the cyclic disulfide structure. PubChem identifies the sequence as RCAHFRWC and confirms the cyclic peptide architecture.
The API is structurally characterized using peptide-specific analytical techniques. The EMA assessment report describes confirmation of the active substance using NMR spectroscopy, mass spectrometry, IR spectroscopy and UV spectroscopy, while amino-acid sequence confirmation was performed by MS/MS and stereochemical characterization by chiral GC-MS.
Because commercial pharmaceutical setmelanotide is supplied as an acetate salt with variable acetate stoichiometry, the free-base molecular formula and molecular mass should not be incorrectly presented as the fixed molecular weight of a single stoichiometric acetate salt.
Setmelanotide acts as an MC4 receptor agonist and is used for chronic weight management in specific rare genetic and syndromic obesity disorders. Current regulatory information includes genetically confirmed POMC, PCSK1 and LEPR pathway deficiencies, Bardet-Biedl syndrome, and acquired hypothalamic obesity in applicable patient populations. EMA identifies its therapeutic area as obesity and its ATC classification as A08AA.
The mechanism is associated with restoration or enhancement of melanocortin signaling involved in satiety and energy balance. In genetic disorders affecting the melanocortin pathway, impaired signaling can contribute to severe hunger and obesity; MC4R agonism by setmelanotide is intended to address this pathway.
For API manufacturers and pharmaceutical developers, high-quality setmelanotide requires control of peptide identity, sequence integrity, purity, related peptide species, aggregation, residual solvents and other process-related impurities.
Setmelanotide is a peptide API, so quality evaluation should use a peptide-specific analytical control strategy rather than automatically applying conventional small-molecule tests such as melting point or pH of a 1% solution.
Relevant characterization may include RP-HPLC/UPLC purity, peptide identity by LC-MS or MS/MS, molecular mass, peptide mapping, amino-acid composition or sequence confirmation, disulfide-bond integrity, residual solvents, water content, counter-ion/acetate determination and related peptide impurities.
The EMA assessment confirms that setmelanotide active-substance characterization included NMR, MS, IR, UV, MS/MS and chiral GC-MS.
No universal public pharmacopoeial numerical release specification was identified for all of the conventional CMS fields below. Therefore, values such as assay, individual impurities, total impurities, loss on drying and residue on ignition should not be invented or represented as universal standards. Commercial API specifications may be established according to the manufacturer's validated analytical procedures and applicable regulatory requirements.
A reliable Setmelanotide API manufacturing program requires control throughout peptide synthesis, cyclization, purification and final processing. Particular attention is required for peptide sequence fidelity, stereochemical integrity, disulfide cyclization, removal of truncated sequences and process-related impurities.
Setmelanotide acetate is described by FDA as a white-to-off-white amorphous powder and is freely soluble in water. The marketed finished product is a sterile injectable formulation containing setmelanotide acetate at 10 mg/mL, but finished-product formulation characteristics should not be confused with the specifications of the bulk API.
Setmelanotide API should be packaged in suitable pharmaceutical-grade, well-closed containers that protect the peptide from moisture, contamination and conditions that could compromise its chemical or physical integrity. Storage conditions should follow the validated stability data and approved product/API specification.
The API should be handled under controlled pharmaceutical manufacturing conditions, with appropriate environmental controls and validated packaging systems. The exact storage temperature and retest period should be established from the manufacturer's stability program rather than inferred from the finished injectable formulation.
Commercial Setmelanotide API documentation may include a Certificate of Analysis (CoA), specification sheet, analytical method information, chromatographic data, identity documentation, residual-solvent results, water-content data, impurity profile, stability information, safety documentation and regulatory support documents, as applicable.
For peptide APIs, analytical documentation should clearly identify the molecular form, salt/counter-ion status, analytical basis and test method so that the reported purity and assay values are scientifically interpretable.
Setmelanotide is a specialized cyclic peptide API requiring peptide-specific synthesis, purification and analytical characterization. Its defined cyclic structure, MC4 receptor activity and application in rare obesity disorders make control of identity, purity, sequence integrity and molecular form particularly important.
A quality-focused Setmelanotide API manufacturing approach should combine validated peptide analytical methods, controlled manufacturing processes, appropriate packaging and comprehensive documentation to support pharmaceutical development and regulated applications.
| Parameter | Specification |
|---|---|
| Appearance | white to off-white crystalline powder |
| Identification | IR & HPLC compliant |
| Assay (HPLC) | 98.0% – 102.0% |
| pH (1% Solution) | 5–6 |