Melanotan 2
Also known as: Melanotan II, MT-II, MT2
3 notable studies · 4 references
TLDR
Melanotan II is an unapproved synthetic melanocortin receptor agonist with controlled human evidence showing increased pigmentation, penile erection, and sexual desire, but its long-term safety is poorly characterized and unregulated use has been associated with significant adverse-event reports.
Research Supports
- Studied for effects on skin pigmentation and melanogenesis
- Investigated for centrally mediated erectile function in men with erectile dysfunction
- Studied for effects on sexual desire and motivation
- Investigated for appetite and energy-balance regulation, largely in preclinical models
- Used as an experimental tool to study melanocortin receptor biology
Observations Reported in Research
- 8 of 10 men developed clinically apparent erections after MT-II vs placebo in an early crossover study (Wessells et al., 1998)
- Mean high-tip penile rigidity duration: about 38 minutes with MT-II vs 3 minutes with placebo
- In a larger study, 17 of 20 men with ED developed erections following MT-II (Wessells et al., 2000)
- Increased sexual desire reported after 68% of MT-II administrations vs 19% with placebo
- Phase I study found pigmentation increases plus unexpected erections, yawning, and nausea (Dorr et al., 1996)
These are brief summaries of what the referenced research examined or reported — not conclusions about safety or effectiveness, and not medical advice. See Notable Studies and Sources & References below for the full context and citations.
At a Glance
Classification: Synthetic cyclic α-melanocyte-stimulating hormone analogue; nonselective melanocortin receptor agonist
Melanotan II is a synthetic cyclic analogue of α-melanocyte-stimulating hormone (α-MSH). Researchers originally developed it primarily to investigate melanogenesis and skin pigmentation. Then something unexpected happened during early human testing: Participants experienced spontaneous erections. That observation opened an entirely different branch of melanocortin research involving sexual function and eventually contributed to development of the related compound bremelanotide (PT-141). MT-II has been studied for: • Melanogenesis • Skin pigmentation • Melanocortin receptor signaling • Erectile function • Sexual motivation • Appetite • Energy balance Small controlled human studies clearly demonstrate biological activity. In an early erectile-dysfunction study, 8 of 10 men developed clinically apparent erections after MT-II versus placebo. But MT-II itself remains unapproved, and modern unregulated use has generated significant safety concerns.
What Is Melanotan 2?
MT-II is a cyclic synthetic analogue derived from α-MSH. Its structure was engineered to increase potency and biological stability compared with the endogenous hormone. The peptide interacts with multiple members of the melanocortin receptor family. This matters because melanocortin receptors regulate much more than pigmentation. Different receptors participate in: • Skin pigmentation • Appetite • Energy homeostasis • Sexual behavior • Autonomic function • Inflammatory signaling MT-II's relative lack of receptor selectivity helps explain why one molecule can affect both skin pigmentation and sexual function.
What Are Researchers Studying?
Skin pigmentation and melanogenesis
MT-II activates melanocortin pathways associated with melanin production. In an early Phase I study, repeated exposure produced measurable increases in pigmentation in healthy volunteers. This established that synthetic melanocortin agonism could alter human pigmentation. But that does not establish unregulated MT-II as a safe tanning product.
Erectile function
One of MT-II's most striking effects is centrally mediated erectile activity. A double-blind crossover study involving 10 men with psychogenic erectile dysfunction found clinically apparent erections in 8 of 10 men following MT-II. Mean duration of high tip rigidity was approximately 38 minutes after MT-II versus 3 minutes with placebo. A later study involving men with psychogenic and organic ED found erections in 17 of 20 participants following MT-II. This is real human pharmacology—not an internet anecdote.
Sexual motivation
The same human studies found effects extending beyond penile vascular function. In one study, increased sexual desire was reported following: 68% of MT-II administrations versus 19% of placebo administrations. That suggested melanocortin signaling participates in central sexual motivation as well as erectile physiology. This ultimately became important to development of bremelanotide, a related melanocortin agonist.
Appetite and energy balance
Melanocortin signaling—particularly MC4R—is deeply involved in central regulation of appetite and energy homeostasis. MT-II has therefore been extensively used experimentally to investigate: • Food intake • Satiety • Energy expenditure • Body-weight regulation Much of this work is preclinical. MT-II should not be described as an established human weight-loss drug.
Melanocortin receptor biology
MT-II has become an important experimental tool for understanding melanocortin receptors. The family includes: MC1R → strongly associated with pigmentation MC2R → ACTH/adrenal signaling MC3R / MC4R → central energy and behavioral regulation MC5R → diverse peripheral functions MT-II's effects arise because it interacts with several melanocortin receptors rather than acting exclusively on one.
How Does It Work?
MC1R Activation of melanocortin-1 receptors on melanocytes stimulates production of eumelanin, increasing pigmentation. MC3R / MC4R Central melanocortin signaling influences: • Sexual behavior • Appetite • Energy balance • Autonomic physiology MC4R signaling is particularly important in the sexual and metabolic effects associated with melanocortin agonists. Central sexual pathways Unlike PDE5 inhibitors, which primarily facilitate peripheral erectile physiology, melanocortin agonists can act through central neural pathways associated with sexual arousal. That's why MT-II's erectile effects were scientifically interesting.
What Does the Research Show?
Human research
Human evidence clearly demonstrates that MT-II is biologically active. Controlled studies have demonstrated: • Increased pigmentation • Spontaneous erections • Increased penile rigidity • Changes in sexual desire • Nausea • Yawning/stretching • Reduced appetite The evidence is therefore considerably stronger than for many research-market compounds. But: Biological activity ≠ established therapeutic safety. MT-II never became an approved medication.
Animal research
Animal research has investigated MT-II extensively in: • Melanogenesis • Sexual behavior • Feeding • Obesity • Energy expenditure • Melanocortin receptor pharmacology This work helped establish MC4R as a major regulator of energy balance and sexual behavior.
In-vitro research
Laboratory research has characterized MT-II interactions with melanocortin receptors and helped map receptor-specific effects. These experiments were particularly useful in the development of more selective melanocortin drugs.
Notable Studies
Evaluation of Melanotan-II, a Superpotent Cyclic Melanotropic Peptide in a Pilot Phase-I Clinical Study
humanResearchers administered MT-II to healthy male volunteers. Increased pigmentation occurred, demonstrating melanotropic activity in humans. Unexpected effects included spontaneous erections, yawning, stretching, nausea, fatigue and somnolence.
Limitations: Only three volunteers participated, making the study useful for proof of biological activity but inadequate for establishing broad safety or efficacy.
View publication →Synthetic Melanotropic Peptide Initiates Erections in Men With Psychogenic Erectile Dysfunction: Double-Blind, Placebo Controlled Crossover Study
humanTen men with psychogenic ED received MT-II and placebo. Eight of ten developed clinically apparent erections after MT-II, and objective penile rigidity was substantially greater than with placebo.
Limitations: Extremely small sample and short-term exposure.
View publication →Melanocortin Receptor Agonists, Penile Erection, and Sexual Motivation: Human Studies With Melanotan II
humanIn 20 men with psychogenic or organic ED, MT-II produced erections in 17 participants and significantly increased reported sexual desire compared with placebo. Nausea and yawning were frequent.
Limitations: Small trial, acute exposure, and no long-term safety assessment.
View publication →What We Still Don't Know
• Long-term safety • Cancer-related consequences of chronic melanocortin stimulation • Long-term effects on melanocytic nevi • Reliable safety of research-market products • Long-term cardiovascular effects • Human metabolic efficacy • Effects of chronic repeated exposure • Product purity and identity in unregulated preparations • How different administration routes affect exposure • Whether adverse-event reports reflect MT-II itself, contaminants, exposure level, or combinations of factors There are published reports of serious toxicity—including rhabdomyolysis and renal dysfunction—following unregulated MT-II exposure. There are also case reports associating MT-II exposure with melanoma, including a 2025 report involving oral mucosal melanoma after nasal-spray use. Such reports cannot prove that MT-II caused the cancer, but they reinforce the need for caution rather than allowing the evidence to be summarized as “MT-II causes melanoma.”
Related Compounds
Recent publications
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Sources & References
- Evaluation of Melanotan-II, a Superpotent Cyclic Melanotropic Peptide in a Pilot Phase-I Clinical Study.
- Synthetic Melanotropic Peptide Initiates Erections in Men With Psychogenic Erectile Dysfunction.
- Wessells H, Levine N, Hadley ME, Dorr R, Hruby V. Melanocortin Receptor Agonists, Penile Erection, and Sexual Motivation: Human Studies With Melanotan II.
- Habbema L, Halk AB, Neumann M, Bergman W. Risks of Unregulated Use of Alpha-Melanocyte-Stimulating Hormone Analogues: A Review.
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