PT-141, known by its non-proprietary name bremelanotide, is a synthetic melanocortin-receptor agonist built on a cyclic heptapeptide scaffold. It originated as a structural relative of Melanotan-2 (MT-2) — specifically, the metabolite that arises when MT-2 loses its C-terminal amide group, a small change that meaningfully reshapes the molecule's receptor preference. In research settings, PT-141 has been characterised most prominently for its activity at the MC4 receptor (MC4R), a melanocortin subtype concentrated in the central nervous system. This article examines bremelanotide strictly as a pharmacological tool compound: its chemistry, its relationship to MT-2, the melanocortin receptor family, the mechanistic basis of MC4R agonism, and the practical realities of handling a lyophilised peptide in the laboratory.
> Research use only. Everything below concerns receptor biology and laboratory practice. PT-141 is supplied for in vitro and laboratory research; it is not a drug, supplement, or article for human or animal consumption.
PT-141 is the laboratory and trade designation for bremelanotide, a synthetic peptide belonging to the melanocortin agonist class. Chemically, it is a cyclic heptapeptide — seven amino-acid residues constrained into a ring through a lactam bridge. That cyclisation is not incidental: melanocortin peptides depend on a conserved His-Phe-Arg-Trp core for receptor recognition, and ring closure locks this pharmacophore into a conformation that the melanocortin receptors read efficiently. The constrained backbone also confers greater metabolic stability than a comparable linear sequence, which is part of why cyclic melanocortin analogues became attractive as tool compounds for probing the receptor family.
The name "bremelanotide" signals the lineage directly: the -melanotide stem marks it as a melanocortin-system peptide. Within pharmacology, it is studied as a non-selective melanocortin agonist that nonetheless shows a characterised preference within the receptor family, with MC4R activity featuring heavily in the literature that has examined the central melanocortin system.
It helps to separate three things that newcomers often conflate. First, the molecule — a defined heptapeptide with a known sequence and molecular weight. Second, the receptor target — the melanocortin receptors, especially MC4R, that the molecule engages. Third, the research questions — what investigators have asked about melanocortin signalling using compounds like this one. This guide stays in the first two lanes and only touches the third at the level of receptor pharmacology, never human or animal outcomes.
| Property | Detail (research context) |
|---|---|
| Common lab name | PT-141 |
| Non-proprietary name | Bremelanotide |
| Class | Synthetic melanocortin-receptor agonist |
| Peptide type | Cyclic heptapeptide (lactam-bridged) |
| Core pharmacophore | Conserved His-Phe-Arg-Trp melanocortin motif |
| Structural origin | Metabolite/analogue of Melanotan-2 (lacks the C-terminal amide) |
| Primary characterised target | MC4 receptor (MC4R); activity also reported across the melanocortin family |
| Receptor emphasis | Central melanocortin axis (MC3R/MC4R) rather than MC1R pigmentation |
| Typical supplied form | Lyophilised powder |
| Verification | HPLC purity profile + per-batch Certificate of Analysis (COA) |
| Status | Research use only — not for human or animal consumption |
To understand PT-141, it pays to start one molecule upstream with Melanotan-2. MT-2 is itself a synthetic, cyclic melanocortin analogue, designed as a more stable, conformationally constrained mimic of the body's endogenous melanocortin peptides. Its sequence carries a C-terminal amide — a capped carboxyl end that contributes to how the molecule sits in certain receptor binding pockets and how it resists exopeptidase trimming.
Bremelanotide is, in essence, MT-2 minus that C-terminal amide. Biologically, it can be viewed as a metabolite of Melanotan-2: when MT-2 is acted upon and the terminal amide group is removed, the resulting peptide is bremelanotide. This single structural edit — replacing the C-terminal carboxamide with a free acid — looks minor on paper but has a measurable effect on the molecule's behaviour at the melanocortin receptors. Small changes near a peptide's termini routinely re-weight its affinity and efficacy across receptor subtypes, because each subtype's binding pocket makes slightly different contacts with the ligand's ends.
The practical consequence reported in the research literature is a shift in receptor emphasis. MT-2's pharmacology is often discussed in connection with MC1R, the melanocortin subtype expressed in skin melanocytes and tied to pigmentation biology. Bremelanotide, by contrast, is characterised with notable weight on the central receptors, particularly MC4R. The two compounds share the melanocortin agonist family and the conserved core motif, but the loss of the C-terminal amide is the structural hinge that distinguishes their profiles.
| Feature | Melanotan-2 (MT-2) | PT-141 (Bremelanotide) |
|---|---|---|
| Molecule type | Cyclic melanocortin peptide analogue | Cyclic melanocortin peptide (metabolite of MT-2) |
| Key structural difference | Carries the C-terminal amide | Lacks the C-terminal amide (free acid) |
| Relationship | Parent analogue | Des-amide metabolite/analogue of MT-2 |
| Receptor emphasis (research) | Discussed alongside MC1R (pigment-associated) | Characterised with emphasis on MC4R (central) |
| Receptor family | Melanocortin agonist | Melanocortin agonist |
| Supplied form | Lyophilised powder | Lyophilised powder |
| Use | Research use only | Research use only |
The takeaway for a researcher selecting a tool compound is that the two are not interchangeable. If a study design hinges on central MC4R pharmacology, bremelanotide is the molecule whose characterised profile aligns with that target; the parent MT-2 sits closer to the MC1R-weighted end of the family.
The melanocortin receptors (MCRs) are a family of five class-A (rhodopsin-like) G-protein-coupled receptors, designated MC1R through MC5R. All five are canonically coupled to the Gs / adenylyl cyclase / cyclic AMP (cAMP) pathway: agonist binding activates the receptor, which activates Gs, which stimulates adenylyl cyclase to raise intracellular cAMP, the second messenger that propagates the signal downstream. The receptors share this signalling backbone but differ sharply in where they are expressed and what endogenous ligands dominate at each.
Their natural agonists are the melanocortins — peptides cleaved from the proopiomelanocortin (POMC) precursor, including the α-, β-, and γ-melanocyte-stimulating hormones (MSH) and ACTH. Two endogenous antagonists/inverse agonists, agouti and agouti-related peptide (AgRP), also act on specific subtypes, giving the system a genuine push-pull architecture rather than agonist-only control. This bidirectional tone is part of why the melanocortin system is such a rich target for pharmacological probing.
A quick orientation to the five subtypes:
MC4R is the receptor most relevant to bremelanotide's characterised profile. It is a G-protein-coupled receptor concentrated in the central nervous system, and it sits at the heart of what researchers call the central melanocortin system — a network in which POMC-derived agonists and AgRP-derived antagonist tone converge on MC4R-bearing neurons. Because MC4R integrates these opposing signals through cAMP, it has become a focal point for investigators studying how the central melanocortin pathway is wired and regulated. A synthetic agonist with characterised MC4R activity, such as bremelanotide, is therefore valued as a pharmacological probe of that receptor in cell-based and animal-model research.
At the molecular level, the mechanism is the textbook GPCR agonist cascade, read through the melanocortin lens. When bremelanotide engages MC4R, the conserved His-Phe-Arg-Trp core makes contact with the receptor's binding pocket, and the constrained cyclic backbone holds that pharmacophore in a receptor-competent geometry. Agonist binding stabilises an active receptor conformation, which catalyses GDP-to-GTP exchange on the associated Gαs subunit. Activated Gαs then stimulates adenylyl cyclase, raising intracellular cAMP, and the elevated cAMP drives downstream effectors — classically protein kinase A (PKA) and cAMP-responsive transcriptional machinery. In cell-based assays, this cascade is exactly what researchers quantify: agonist-evoked cAMP accumulation is the standard readout used to measure potency (EC50) and efficacy at each melanocortin subtype.
Two mechanistic features deserve emphasis, both framed strictly at the receptor level:
Subtype profile. Bremelanotide is a non-selective melanocortin agonist in the sense that it can engage multiple MCRs, but its characterised activity is weighted toward the central MC3R/MC4R axis rather than the MC1R-dominated pigmentation pathway. In pharmacological terms, researchers describe such a compound by its relative EC50 and efficacy across the five receptors — the panel of values that defines where in the family the molecule "lives." For MC4R specifically, bremelanotide is studied as an agonist that activates the canonical Gs/cAMP route.
Central signalling context. Because MC4R is concentrated in the central nervous system, agonism at this receptor is investigated in the context of central melanocortin signalling — the integration of POMC-derived agonist input and AgRP-derived antagonist tone at MC4R-expressing neurons. Studies that use bremelanotide as a tool typically ask how the receptor and its signalling cascade behave when a defined synthetic agonist is applied, measured through molecular and cellular endpoints such as cAMP, receptor occupancy, and signalling kinetics. The mechanism is described as receptor activation and second-messenger generation, full stop.
It is worth stating plainly what this section does not cover: nothing here concerns any downstream physiological, behavioural, or organism-level outcome. The mechanistic account begins at ligand-receptor binding and ends at second-messenger generation, because that is the level at which bremelanotide functions as a research probe of melanocortin pharmacology.
Across the melanocortin literature, compounds like bremelanotide appear as pharmacological tools for interrogating the receptor family. The recurring themes are structural and mechanistic rather than applied:
The throughline is that bremelanotide's value in research is as a defined, reproducible melanocortin agonist with a known structure and a characterised MC4R-leaning profile. That makes it useful precisely because its pharmacology is understood at the receptor level, allowing it to serve as a benchmark or probe in experiments aimed at the biology of the melanocortin system.
Research-grade PT-141 is supplied as a lyophilised (freeze-dried) powder. Lyophilisation removes water under vacuum, leaving a dry peptide cake that is far more stable in storage than any solution — an important property for a peptide intended to retain identity and purity until the moment of use.
A few bench-level practices apply to lyophilised peptides generally, stated here at the level of laboratory technique:
These handling notes describe laboratory storage and preparation of a research reagent — they are not, and must not be read as, instructions for any use in or on a human or animal. Reconstitution here means preparing a defined solution for an in vitro or laboratory experiment.
For any research peptide, identity and purity are everything. A result obtained with poorly characterised material is uninterpretable, because contaminants, truncated sequences, or incorrect mass can all confound an assay. Two analytical pillars underpin confidence in research-grade bremelanotide:
High-performance liquid chromatography (HPLC). Reversed-phase HPLC separates the components of a peptide preparation and quantifies the main peak relative to impurities, yielding a purity percentage. A clean, dominant peak with minimal shoulders indicates that the synthesis and purification delivered a homogeneous product. HPLC is the workhorse purity assay for synthetic peptides and the figure most often cited on supplier documentation.
Mass verification. Identity is typically confirmed by mass spectrometry, which measures the molecular weight of the peptide and verifies it matches the expected value for the defined sequence. For bremelanotide, this confirms the molecule is the intended des-amide cyclic heptapeptide and not a mis-synthesised or mis-modified variant.
The Certificate of Analysis (COA). Reputable suppliers issue a COA with each batch, consolidating the analytical evidence: the HPLC purity figure, the mass-spectrometry confirmation of identity, and batch-specific details such as lot number and appearance. A per-batch COA is the practical mechanism by which a laboratory verifies that what arrived matches what was ordered — and it is a baseline expectation, not a premium feature, for serious research material.
When evaluating a source, the relevant questions are simple: Is there an HPLC purity profile? Is identity confirmed by mass? Is a COA provided for the specific batch in hand? Affirmative answers on all three are the floor for reproducible work.
Yes. PT-141 is the common laboratory and developmental designation, and bremelanotide is the non-proprietary (generic) name for the same synthetic cyclic heptapeptide. The two terms refer to one molecule.
Bremelanotide is essentially Melanotan-2 without its C-terminal amide — it can be regarded as a des-amide metabolite/analogue of MT-2. Both are cyclic melanocortin peptides sharing the conserved core motif, but removing the terminal amide group re-weights the molecule's activity across the melanocortin receptor subtypes.
Its characterised profile emphasises the MC4 receptor (MC4R), a melanocortin subtype concentrated in the central nervous system. Bremelanotide is also reported to engage other melanocortin receptors, but MC4R activity is the focus of most pharmacological characterisation.
MC4R is a Gs-coupled GPCR. An agonist stabilises the receptor's active state, which activates Gαs, stimulates adenylyl cyclase, and raises intracellular cAMP — the second messenger measured in cell-based potency (EC50) assays. The mechanism is described entirely as receptor activation and second-messenger generation.
Each batch should come with a Certificate of Analysis (COA) reporting HPLC purity and mass-spectrometry confirmation of identity, plus batch-specific details such as lot number. A per-batch COA is the standard way to verify identity and purity before use.
Alluvia Peptides supplies PT-141 (bremelanotide) for laboratory research, with verification built into every batch:
Browse the product page for specifications and batch documentation: PT-141 (Bremelanotide) 10mg. To explore the wider catalogue of characterised research compounds, visit the Research Peptides category.
Research use only — not for human consumption. PT-141 (bremelanotide) is supplied strictly for in vitro and laboratory research purposes. It is not a drug, dietary supplement, cosmetic, or any article intended for human or animal use, ingestion, injection, or application of any kind. Nothing in this article is medical advice, a therapeutic claim, or a description of use in or on the body; all content concerns melanocortin-receptor pharmacology and laboratory practice only. Handling, storage, and experimental use of research chemicals must comply with all applicable institutional safety protocols and local, state, and federal regulations. Always consult the Certificate of Analysis and appropriate safety data before working with any research compound.