What Is PT-141? Bremelanotide Research Guide (UK)

En resumen

PT-141, also known as bremelanotide, is a synthetic cyclic heptapeptide melanocortin-receptor agonist derived structurally from Melanotan II. It is produced by modifying the C-terminus of the MT-II scaffold — replacing the terminal amide with a hydroxyl group — which yields a closely related cyclic peptide with a distinct receptor-selectivity profile while retaining the lactam-bridged, enzymatically stable architecture of its parent compound. In biochemical and cellular research systems PT-141 acts as an agonist at the centrally expressed melanocortin receptors MC3R and MC4R, with comparatively higher potency at MC4R and substantially reduced activity at MC1R relative to Melanotan II. That shift toward MC4R selectivity makes it a useful tool for isolating MC4R-mediated signalling — G-protein-coupled cAMP and phospholipase-C cascades, intracellular calcium flux, and ERK/MAPK pathway activation — within neuronal and receptor-expressing model systems. Observed responses vary with receptor subtype, concentration, exposure time and experimental model, so PT-141 is used to characterise melanocortin-receptor signalling rather than to infer defined biological outcomes. MY PEPTIDES supplies PT-141 as a pre-mixed solution with a batch-specific Certificate of Analysis, stored refrigerated at 2–8°C. It is supplied strictly for in-vitro laboratory research use only — not for human or veterinary use, and carries no therapeutic claims.

PT-141 — also known by its development name bremelanotide — is a synthetic cyclic heptapeptide used in laboratory research as a melanocortin-receptor agonist. It is one of the more precisely characterised tools in melanocortin pharmacology, largely because of how it was made: it is a deliberate single-point modification of an existing compound, which makes the two a controlled pair.

Research use only. PT-141 is supplied strictly for in-vitro laboratory research. This page does not describe dosing, administration, or use in humans or animals, and makes no therapeutic claims.

Structure and how it relates to Melanotan II

PT-141 is derived from the Melanotan II scaffold. The change is at the C-terminus: where Melanotan II is amidated (-NH₂), PT-141 carries a free acid (-OH).

Melanotan II — Ac-Nle-cyclo[Asp-His-D-Phe-Arg-Trp-Lys]-NH₂
PT-141 — Ac-Nle-cyclo[Asp-His-D-Phe-Arg-Trp-Lys]-OH

Everything else is shared: the norleucine substitution, the D-phenylalanine, and the lactam bridge that cyclises the molecule and gives it resistance to enzymatic degradation. That structural near-identity is the point — it means a difference in observed response between the two can reasonably be attributed to receptor selectivity rather than to unrelated structural variation.

Receptor selectivity

This is where the two diverge. In biochemical and cellular systems:

PT-141 is an agonist at MC3R and MC4R, with comparatively higher potency at MC4R and substantially reduced activity at MC1R relative to Melanotan II.
Melanotan II is a broad, non-selective agonist across MC1R, MC3R, MC4R and MC5R, with negligible activity at MC2R.

MC1R is the receptor most associated with pigmentation pathways in the literature, so a compound with markedly reduced MC1R activity lets investigators study the centrally expressed receptors more cleanly.

What researchers study

PT-141 appears in the literature primarily as a reference agonist for characterising melanocortin signalling:

MC3R and MC4R binding, activation and receptor selectivity
MC4R-mediated cAMP and phospholipase-C signalling, intracellular calcium flux, and ERK/MAPK pathway activation in neuronal and receptor-expressing models
Comparative pharmacology against non-selective melanocortin analogues
Structure–activity relationship (SAR) research on cyclic melanocortin peptides
Receptor-expression and signalling assay development

Reported observations vary with receptor subtype, concentration, exposure time and model system. The compound is best understood as a probe for these pathways rather than as having any fixed effect.

Regulatory status

Bremelanotide holds a marketing authorisation in some jurisdictions outside the UK as a prescription medicine. That is a fact about the licensed pharmaceutical product, not about research-grade material, and the two are not interchangeable. Material supplied here is not a licensed medicine in the UK, is not manufactured to pharmaceutical standards, and is sold strictly as a laboratory reference compound. See are peptides legal in the UK? for the general position.

Handling and verification

PT-141 ships as a pre-mixed solution — there is no reconstitution step — with a batch-specific Certificate of Analysis recording the HPLC-measured purity for that lot. Refrigerate at 2–8°C on arrival and do not freeze it; freeze–thaw cycling damages peptides already in solution. See how to store research peptides.

Browse PT-141 and Melanotan II, or read the Melanotan II guide for the broad-spectrum comparator.

Preguntas frecuentes

What is PT-141?

A synthetic cyclic heptapeptide melanocortin-receptor agonist, also called bremelanotide, derived structurally from Melanotan II. It is used in laboratory research as an MC3R/MC4R reference agonist. For in-vitro research use only.

What is the difference between PT-141 and Melanotan II?

They share the same cyclic scaffold and differ at the C-terminus: Melanotan II is amidated, PT-141 carries a free acid. That single change shifts PT-141 toward MC4R selectivity with substantially reduced MC1R activity, whereas Melanotan II acts broadly across MC1R, MC3R, MC4R and MC5R.

Which receptors does PT-141 act on?

MC3R and MC4R, with comparatively higher potency at MC4R. Its activity at MC1R is substantially reduced relative to Melanotan II, which is what makes it useful for isolating centrally expressed melanocortin signalling.

Is PT-141 a licensed medicine in the UK?

No. Bremelanotide is authorised as a prescription medicine in some jurisdictions outside the UK, but that applies to the licensed pharmaceutical product, not to research-grade material. PT-141 supplied here is not a licensed medicine and is sold strictly for in-vitro laboratory research.

How is PT-141 supplied and stored?

As a pre-mixed solution with a batch-specific Certificate of Analysis, so there is no reconstitution step. Refrigerate at 2–8°C on arrival, keep the vial sealed and away from light, and do not freeze it.