PT-141, also known by its systematic name Bremelanotide, is a synthetic cyclic heptapeptide derived from Melanotan II, itself an analogue of the endogenous hormone alpha-melanocyte-stimulating hormone (α-MSH). Classified as a melanocortin receptor agonist, PT-141 is produced through solid-phase peptide synthesis and carries a distinct cyclic backbone that differentiates it structurally from its linear predecessors. The compound draws consistent research interest because of its selective activity at centrally expressed melanocortin receptor subtypes — a property that makes it a useful tool for mapping receptor pharmacology and downstream signaling in preclinical models.
Molecular Structure and Key Properties
PT-141 has the molecular formula C₅₀H₆₈N₁₄O₁₀ and a molecular weight of approximately 1025.2 g/mol. Its defining structural feature is a cyclic arrangement formed by a lactam bridge — a bond between an amine and a carboxyl group within the peptide chain — which constrains the molecule into a relatively rigid conformation. This rigidity is significant for laboratory work because it reduces the conformational flexibility that often complicates receptor binding studies with linear peptides, allowing researchers to observe more consistent and reproducible receptor interactions. The peptide contains a D-phenylalanine residue at position 7, a modification that increases metabolic resistance compared to the native α-MSH sequence. In solution, PT-141 is typically soluble in water and common aqueous buffers at research-relevant concentrations, and lyophilized preparations are the standard format for long-term storage. The compound is assigned CAS number 189691-06-3, and analytical-grade material should present as a white to off-white powder.
Research Applications
The primary research application for PT-141 involves its activity at melanocortin receptor subtypes MC3R and MC4R, both of which are expressed in the central nervous system. Researchers use the compound to probe how these receptors mediate signaling cascades — particularly the cyclic AMP (cAMP) pathway, where receptor activation leads to measurable increases in intracellular cAMP concentrations. In vitro binding assays using cell lines transfected with MC3R or MC4R constructs allow investigators to quantify receptor affinity and compare PT-141’s potency against other melanocortin ligands under controlled conditions. Preclinical studies in rodent models have examined how MC3R and MC4R activation influences neuroendocrine signaling and behavioral endpoints, generating data that informs broader melanocortin system mapping. Because the compound exhibits selectivity for central receptor subtypes over the peripheral MC1R, which governs pigmentation, it serves as a comparator tool in studies designed to distinguish tissue-specific melanocortin activity. Researchers also incorporate PT-141 into structure-activity relationship (SAR) analyses, using its cyclic scaffold as a reference point when synthesizing and evaluating novel melanocortin analogues.
Analytical Use and Sourcing Considerations
In the laboratory, PT-141 is most commonly handled as a reconstituted solution prepared from lyophilized powder, with sterile water or dilute acetic acid used as the reconstitution vehicle depending on the assay protocol. Researchers working with melanocortin receptor binding or cAMP accumulation assays typically require material with a purity of 98% or greater, as lower-purity preparations introduce competing peptide fragments that distort dose-response measurements. Characterization of research-grade PT-141 should include high-performance liquid chromatography (HPLC) for purity confirmation and mass spectrometry to verify the molecular weight and confirm the correct cyclic structure. Certificates of Analysis from reputable suppliers should document both purity percentage and identity confirmation from these methods. Storage at −20°C in lyophilized form under desiccated conditions is standard, and repeated freeze-thaw cycles of reconstituted stock solutions should be avoided to preserve peptide integrity. Procurement staff sourcing PT-141 for institutional use should confirm that suppliers operate under quality management frameworks appropriate for analytical reagent production and that batch-specific documentation is available on request.
PT-141 remains a consistently relevant research tool because its well-characterized receptor selectivity and stable cyclic structure make it a reliable reference compound for ongoing investigations into melanocortin system pharmacology and the development of next-generation receptor-targeted ligands.
For Research Use Only. Not for human consumption. All compounds described in this article are supplied as analytical-grade reagents for institutional in vitro laboratory research only. Not intended to diagnose, treat, cure, or prevent any disease. These statements have not been evaluated by the Food and Drug Administration.
