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Research Catalog

parent and analog

Melanotan II vs PT-141 (Bremelanotide)

PT-141 is the C-terminal free-acid form of the Melanotan II scaffold. The recorded cyclic scaffold is shared, while the terminal group differs.

Published: 2026-10-03Library record comparison: 2026-10-03

01

Identity side by side

Recorded molecular identities of Melanotan II and PT-141 (Bremelanotide)
Recorded fieldMelanotan IIPT-141 (Bremelanotide)
Canonical nameMelanotan IIBremelanotide
AliasesMelanotan-II; MT-II; MT-2Bremelanotide; PT 141; PT-141 free base
Development codesnot recordedPT-141
CAS121062-08-6189691-06-3
UNIIUPF5CJ93X76Y24O4F92S
PubChem CID924329941379
Molecular formulaC50H69N15O9C50H68N14O10
Molecular weight (Da)1024.181025.17
Sequence length (residues)77
Terminal modificationsN-terminal acetylation; C-terminal amideN-terminal acetylation; C-terminal free acid
Structural modificationsSide-chain to side-chain lactam bridge, Asp to Lys; Norleucine substitution; D-phenylalanine substitutionSide-chain to side-chain lactam bridge, Asp to Lys; Norleucine substitution; D-phenylalanine substitution

Melanotan II: nomenclature notes

The unqualified word melanotan is not a usable identity field. Melanotan II is this cyclic lactam analog; Melanotan I is afamelanotide, a linear thirteen-residue peptide with a different formula and mass. They are distinct molecules and are never interchangeable as identities — but neither are they unrelated: both are analogs of alpha-melanocyte-stimulating hormone and both belong to the melanocortin family. What differs is the structure.

PT-141 (Bremelanotide): nomenclature notes

Bremelanotide is the canonical substance name; PT-141 is the development code and the name under which the compound is most often supplied. Both denote the same molecule. The compound is structurally the C-terminal free acid of the Melanotan II scaffold — the two share a carbon count and differ by one oxygen for one nitrogen and one hydrogen.

02

Recorded modification details

An aligned one-letter sequence is not recorded for this pair. The stored modification and sequence notes are shown below.

Melanotan II

Terminal modifications
N-terminal acetylation; C-terminal amide
Structural modifications
Side-chain to side-chain lactam bridge, Asp to Lys; Norleucine substitution; D-phenylalanine substitution
Stored three-letter notation
Ac · Nle · Asp · His · D-Phe · Arg · Trp · Lys · NH2
Sequence notes
A linear one-letter string cannot describe this molecule and none is published here. The peptide is seven residues, closed into a ring by a lactam bridge between the aspartate side-chain carboxyl and the lysine side-chain amine; the N-terminal norleucine sits OUTSIDE that ring, so the cyclized portion spans six residues. It also carries a D-phenylalanine. Written as a plain seven-residue sequence it would denote a different, linear compound.

PT-141 (Bremelanotide)

Terminal modifications
N-terminal acetylation; C-terminal free acid
Structural modifications
Side-chain to side-chain lactam bridge, Asp to Lys; Norleucine substitution; D-phenylalanine substitution
Stored three-letter notation
Ac · Nle · Asp · His · D-Phe · Arg · Trp · Lys · OH
Sequence notes
As with Melanotan II, no linear one-letter string is published here: the peptide is closed by a lactam bridge between the aspartate side-chain carboxyl and the lysine side-chain amine. The single structural difference from Melanotan II is at the C-terminus, which is a free acid rather than an amide.

03

Recorded mechanisms

These lists show the links recorded in each monograph. An unlisted link does not establish its absence from the molecule’s biology.

Shared recorded links

Recorded only for Melanotan II

not recorded

Recorded only for PT-141 (Bremelanotide)

not recorded

04

Recorded compound classes

Shared recorded links

Recorded only for Melanotan II

not recorded

Recorded only for PT-141 (Bremelanotide)

not recorded

05

References for the relationship

  1. Structural insights into ligand recognition and activation of the melanocortin-4 receptor.

    Zhang H, Chen LN, Yang D, Mao C, Shen Q, Feng W, Shen DD, Dai A, Xie S, Zhou Y, Qin J, Sun JP, Scharf DH, Hou T, Zhou T, Wang MW, Zhang Y

    Cell research · 2021-08-25 · Journal Article

    current
    PMID 34433901PMC8563965DOI 10.1038/s41422-021-00552-3PT-141 (Bremelanotide)Melanotan I (Afamelanotide)alpha-MSHTHIQSetmelanotideMC1R
  2. Structures of active melanocortin-4 receptor-Gs-protein complexes with NDP-α-MSH and setmelanotide.

    Heyder NA, Kleinau G, Speck D, Schmidt A, Zschunke S, Szczepek M, Bauer B, Koch A, Gallandi M, Kwiatkowski D, Bürger J, Mielke T, Beck-Sickinger AG, Hildebrand PW, Spahn CMT, Hilger D, Schacherl M, Biebermann H, Hilal T, Kühnen P, Kobilka BK, Scheerer P

    Cell research · 2021-09-24 · Journal Article

    current
    PMID 34561620PMC8563958DOI 10.1038/s41422-021-00569-8PT-141 (Bremelanotide)Melanotan I (Afamelanotide)SetmelanotideMC1R

06

Read the full monographs

Melanotan II →PT-141 (Bremelanotide) →