Melanotan 2

Primary Uses and Effects

Skin Tanning and UV Protection

Melanotan II is best known for its ability to promote skin pigmentation by mimicking the effects of the body’s natural α-melanocyte-stimulating hormone (α-MSH). It binds to melanocortin 1 receptors (MC1R) on melanocytes — the cells that produce melanin — triggering increased synthesis of eumelanin, the dark pigment responsible for tanning. This makes the skin appear darker and more sun-kissed, even without substantial exposure to ultraviolet (UV) light.

What makes this effect particularly valuable from a research standpoint is the potential for photoprotection. Higher melanin levels can help protect skin from sunburn and UV-induced cellular damage, offering promise for those with fair skin or conditions like erythropoietic protoporphyria (EPP) where sunlight causes severe pain and damage. While MT-II is not approved for therapeutic use, a related analog, afamelanotide (Scenesse®), has already been approved for these conditions, validating the potential of melanin-stimulating peptides.

Sexual Function Enhancement

Another striking effect of Melanotan II is its influence on sexual arousal and erectile function. MT-II activates melanocortin receptors MC3R and MC4R in the brain, which are involved in regulating sexual behavior and desire. In human studies, men who received MT-II often reported spontaneous erections, even in the absence of direct sexual stimulation.

The peptide appears to enhance both the physical and psychological aspects of sexual arousal, making it a research candidate for erectile dysfunction (ED), particularly cases that do not respond well to traditional medications like phosphodiesterase-5 inhibitors (e.g., Viagra). MT-II was also found to increase libido and sexual thoughts, further demonstrating its potential utility in addressing sexual desire disorders.

Appetite Suppression and Metabolic Impact

Research subjects frequently report reduced appetite following MT-II administration. This effect is believed to be mediated by MC4R activation in the hypothalamus, an area of the brain responsible for energy homeostasis and hunger regulation.

In rodent models, MT-II administration has consistently resulted in lower food intake and significant weight loss, suggesting potential for future anti-obesity treatments. While no clinical studies have yet validated its use in human weight loss, its effects on the appetite-regulating pathways continue to attract attention from metabolic researchers.

Notable Scientific Studies

Dorr et al., 1996 – Pilot Human Tanning Study¹

This first-in-human Phase I trial tested MT-II’s ability to induce tanning in fair-skinned men with minimal sun exposure. Subjects received subcutaneous injections of MT-II over 10 days. Two of the three participants developed noticeably darker skin by the end of the trial, even without deliberate UV exposure. Importantly, this demonstrated that the peptide could activate the body’s pigmentation system independently, supporting its use as a “sunless tanning” agent. Mild nausea and spontaneous erections were noted as consistent side effects.

Wessells et al., 1998 – Erectile Dysfunction (Psychogenic) Study²

In a double-blind, placebo-controlled crossover study involving 10 men with psychogenic erectile dysfunction (ED), MT-II was administered via subcutaneous injection. 80% of the men experienced rigid erections with MT-II, while none responded to placebo. Not only did MT-II improve erection quality, but the average duration of rigidity exceeded 30 minutes, with no stimulation required. This validated MT-II’s unique mechanism — acting centrally via melanocortin pathways, rather than peripherally like most ED medications.

Wessells et al., 2000 – Erectile Dysfunction (Organic) and Libido Study³

Building on prior results, this study focused on men with organic ED caused by conditions like diabetes and vascular disease. MT-II again induced significant erectile responses — in over 60% of injections, participants achieved full or partial erections. Additionally, researchers reported notable increases in sexual desire, as measured by self-reporting questionnaires. These effects occurred even in cases where erectile nerves were compromised, showing MT-II’s central neural action to be distinct and promising.

Minakova et al., 2019 – Social Behavior in Autism Mouse Model⁴

In a groundbreaking study, researchers administered MT-II to mice with autism-like behaviors caused by maternal immune activation (MIA), a model for developmental disorders. After 7 days of treatment, the mice showed dramatic improvements in social behaviors, including increased interaction and communication. Researchers believe this is linked to MT-II’s ability to stimulate oxytocin release, a hormone strongly tied to bonding and emotional recognition. Though in early stages, this opens a potential avenue for MT-II research in neurodevelopmental and mood disorders.

Emerging and Future Research Directions

Selective Analogs for Safety and Precision

One of the current challenges with MT-II is its lack of receptor selectivity — it stimulates multiple melanocortin receptors, resulting in multiple effects (tanning, appetite loss, sexual arousal, nausea). Researchers are now creating modified analogs of MT-II that selectively activate individual receptors. For example, by isolating MC1R activation, scientists hope to develop tanning peptides with fewer systemic side effects. Likewise, MC4R-selective peptides may provide targeted treatments for sexual dysfunction or obesity without impacting skin pigmentation or causing nausea.

Melanocortin Drugs in Sexual Health

The success of bremelanotide (Vyleesi®), an FDA-approved drug for female sexual dysfunction derived from MT-II, has reignited interest in this class of compounds. Future clinical trials may revisit MT-II or next-gen analogs for use in male sexual dysfunction, low libido in women, and sexual side effects from antidepressants. These applications could offer alternatives for patients who don’t respond to or cannot tolerate existing treatments.

Neuropsychiatric and Oxytocin-Based Therapies

MT-II’s ability to stimulate the release of oxytocin through MC4R activation is being explored as a novel way to improve social cognition and emotional bonding, particularly in conditions like autism spectrum disorder, social anxiety, and depression. While human trials are still in early planning, this line of research could one day position MT-II analogs as therapeutic tools in mental health and social dysfunction.

Weight Regulation and Metabolic Disease

Though not currently in clinical use for weight management, the appetite-suppressing effects of MT-II make it a strong research candidate for addressing obesity, binge-eating disorder, and metabolic syndrome. Because the melanocortin system plays a critical role in energy balance, and MT-II potently activates this system, future studies may lead to safer, receptor-specific variants tailored for long-term metabolic use.

Sources

1. Dorr RT, et al. (1996). Evaluation of melanotan-II, a superpotent cyclic melanotropic peptide in a pilot phase-I clinical study. Life Sciences, 58(20), 1777-1784.
2. Wessells H, et al. (1998). Synthetic melanotropic peptide initiates erections in men with psychogenic erectile dysfunction. Journal of Urology, 160(2), 389-393.
3. Wessells H, et al. (2000). Effect of an α-MSH analog on penile erection and sexual desire in men with organic erectile dysfunction. Urology, 56(4), 641-646.
4. Minakova E, et al. (2019). Melanotan-II reverses autistic features in a mouse model of autism. Scientific Reports, 9, 1-10.

Note: Melanotan II is offered strictly for research purposes. It is not approved by the FDA or other regulatory bodies for human or veterinary use.