MT-2 Research Guide — Melanocortin Agonist Explained
A comprehensive guide to MT-2 — melanocortin receptor agonism, melanogenesis research and comparison with PT-141.
MT-2 is a synthetic analogue of alpha-melanocyte stimulating hormone (α-MSH) and one of the most studied melanocortin peptides in research. Its broad receptor affinity profile — spanning MC1R through MC5R — makes it a versatile tool for studying pigmentation pathways, UV protective mechanisms, and central nervous system signalling. This guide covers what MT-2 is, how it works and what distinguishes it from related compounds like PT-141.
What is MT-2?
MT-2 is a cyclic heptapeptide — a 7 amino acid cyclic analogue of the endogenous hormone alpha-MSH. It was originally developed as part of research into UV-protective mechanisms, with the hypothesis that stimulating the body’s natural melanogenesis research response could reduce UV-induced damage in melanogenesis research models.
MT-2 binds with high affinity to melanocortin receptors MC1R, MC3R, MC4R and MC5R, producing a broader receptor activation profile than native alpha-MSH. This broad affinity is both what makes it scientifically interesting and what distinguishes it from the more selective PT-141 (Bremelanotide).
Melanocortin Receptors — What Are They?
The melanocortin receptor family consists of five G-protein coupled receptors (MC1R–MC5R), each with distinct tissue distribution and physiological roles:
| Receptor | Primary Location | Research Association |
|---|---|---|
| MC1R | Melanocytes (skin) | Melanogenesis, pigmentation |
| MC2R | Adrenal glands | ACTH signalling (not activated by MT-2) |
| MC3R | Brain, gut | Energy homeostasis, inflammation |
| MC4R | Brain (hypothalamus) | Appetite, arousal, CNS signalling |
| MC5R | Exocrine glands | Secretory function, immune modulation |
MT-2 Research Vectors
Melanogenesis and UV Research
MT-2’s primary research interest is its activation of MC1R on melanocytes, stimulating the production of eumelanin — the dark pigment responsible for UV-protective melanogenesis research in skin. This makes it a key compound in research into photoprotection mechanisms and melanogenesis signalling pathways.
MC4R and CNS Pathway Research
MT-2’s affinity for MC4R in the hypothalamus has made it a subject of research into central appetite regulation and arousal signalling pathways. This receptor overlap with PT-141 makes comparative studies between the two compounds scientifically useful.
Anti-inflammatory Research
MC3R and MC5R activation by MT-2 has been associated with anti-inflammatory signalling in some research models, adding a potential immunomodulatory dimension to its research profile.
MT-2 vs PT-141 — What’s the Difference?
PT-141 (Bremelanotide) is a closely related compound derived from MT-2 through a structural modification that reduces its melanogenic activity while retaining CNS receptor affinity. The key difference is selectivity:
| Property | MT-2 | PT-141 |
|---|---|---|
| Receptor Profile | MC1R, MC3R, MC4R, MC5R | MC3R, MC4R (selective) |
| Melanogenic Activity | High | Minimal |
| CNS Activity | Present | Primary focus |
| Research Focus | Broad melanocortin | Selective CNS/MC4R |
| Structure | Cyclic heptapeptide | MT-2 derivative (modified) |
For researchers specifically interested in MC4R pathway studies without melanogenic confounders, PT-141 is the more appropriate reagent. For broad melanocortin system research including MC1R-mediated pigmentation, MT-2 is the standard.
Compound Profile
| Property | Detail |
|---|---|
| Sequence | Ac-Nle-cyclo[Asp-His-D-Phe-Arg-Trp-Lys]-NH2 |
| Molecular formula | C50H69N15O9 |
| Molecular weight | 1024.2 g/mol |
| CAS number | 121062-08-6 |
| Other names | MT-II; melanotan II |
| Origin | Developed at the University of Arizona in the late 1980s and 1990s |
| Related approved medicines | Afamelanotide (a linear α-MSH analogue) for erythropoietic protoporphyria; bremelanotide (PT-141) for hypoactive sexual desire disorder |
| Regulatory status | Not approved anywhere. The UK MHRA has repeatedly warned against unlicensed MT-2 products |
Key Published Research
- Pilot phase 1 study (1996): MT-2 increased skin pigmentation in healthy men; reported side effects included nausea, flushing and spontaneous penile erections.1
- Erectile response (1998): In a double-blind crossover study in men with psychogenic erectile dysfunction, MT-2 initiated erections — research that led to the development of bremelanotide (PT-141).2
- Use in the general population (2009): A BMJ report described widespread unlicensed internet sales and self-administration of MT-1 and MT-2 products of uncertain quality.3
- Dermatology reviews (2010, 2017): Reviews of melanotropic peptide use documented new or changing moles, case reports of melanoma, and other adverse events associated with unregulated use.4,5
Regulatory & Research Status (2026)
- US FDA: MT-2 was among twelve peptides removed from the FDA’s Category 2 compounding list in April 2026. It was not reviewed by the advisory committee in July 2026 and remains unapproved.
- UK: No MT-2 product is licensed. The MHRA continues to act against unlicensed injectable and nasal products sold for human use.
- A note on PT-141: Although PT-141 is described above as CNS-focused, bremelanotide is itself a non-selective melanocortin agonist, and focal hyperpigmentation is listed as an adverse effect in its prescribing information.
Evidence Quality & Limitations
Controlled human data on MT-2 are limited to small studies from the 1990s. Most safety information comes from case reports and surveys of unregulated users, which cannot establish incidence or causation but consistently raise concerns about changes in melanocytic lesions. Because MT-2 acts on several melanocortin receptors (MC1R, MC3R, MC4R and MC5R), effects in any model may reflect more than one receptor pathway.
References
- Dorr RT, et al. Evaluation of melanotan-II, a superpotent cyclic melanotropic peptide in a pilot phase-I clinical study. Life Sci. 1996;58:1777–84. PubMed
- Wessells H, et al. Synthetic melanotropic peptide initiates erections in men with psychogenic erectile dysfunction: double-blind, placebo controlled crossover study. J Urol. 1998;160:389–93. PubMed
- Evans-Brown M, et al. Use of melanotan I and II in the general population. BMJ. 2009;338:b566. PubMed
- Langan EA, et al. Melanotropic peptides: more than just “Barbie drugs” and “sun-tan jabs”? Br J Dermatol. 2010;163:451–5. PubMed
- Habbema L, et al. Risks of unregulated use of alpha-melanocyte-stimulating hormone analogues: a review. Int J Dermatol. 2017;56:975–80. PubMed
