PT-141 vs Melanotan II: Comparing Melanocortin Agonists in Research

Introduction

PT-141 (bremelanotide) and Melanotan II (MT-II) are both synthetic melanocortin receptor agonists derived from the α-MSH peptide family, but they differ significantly in their receptor selectivity profiles, structural characteristics, and research applications.

> Research Use Only: Both compounds are for laboratory research purposes only.

Quick Comparison

| Feature | PT-141 (Bremelanotide) | Melanotan II | |---|---|---| | Structure | Cyclic heptapeptide | Cyclic heptapeptide | | Molecular weight | ~1025 Da | ~1024 Da | | Primary receptors | MC3R, MC4R | MC1R, MC3R, MC4R, MC5R | | Tanning effect | Minimal | Significant (MC1R) | | Sexual function research | Primary application | Secondary application | | FDA approval | Yes (Vyleesi, HSDD) | No |

Structural Differences

Both peptides share a cyclic heptapeptide backbone derived from α-MSH, but differ in key positions: - MT-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

The primary structural difference is the C-terminal modification (amide in MT-II vs. free acid in PT-141), which significantly alters receptor binding kinetics and selectivity. PT-141's free acid C-terminus reduces its affinity for MC1R, substantially diminishing its pigmentation effects while preserving MC3R/MC4R activity [1].

Receptor Selectivity and Research Implications

MC1R (Pigmentation)

- MT-II: High MC1R affinity → significant melanogenesis and skin tanning in research models - PT-141: Low MC1R affinity → minimal pigmentation effect; useful when isolating sexual/CNS effects from pigmentation confounds

MC3R and MC4R (Sexual Function, Energy Homeostasis)

Both compounds show high affinity for MC3R and MC4R. However, PT-141's cleaner selectivity profile makes it preferable when MC1R-mediated effects would confound results [2].

Choosing Between PT-141 and MT-II for Research

- Use PT-141 when: Studying sexual arousal/function pathways without pigmentation confounds; conducting CNS melanocortin research - Use MT-II when: Studying the full melanocortin system including pigmentation; investigating MC1R-mediated effects

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This article is for scientific and educational reference only. All products are for research use only and not for human or animal consumption.

References

1. Hadley, M.E., & Dorr, R.T. (2006). Melanocortin peptide therapeutics: historical milestones, clinical studies and commercialization. Peptides, 27(4), 921–930.
2. Shadiack, A.M., et al. (2007). Melanocortins in the treatment of male and female sexual dysfunction. Current Topics in Medicinal Chemistry, 7(11), 1137–1144.

See Also: PT-141 Research Overview · Melanotan II Research · Melanocortin System Research Overview