MT-2 (Melanotan II): what the studies say and the risks

What it is

Melanotan II, written MT-2 or MT-II, is a synthetic peptide built to copy alpha-melanocyte-stimulating hormone, or alpha-MSH. Alpha-MSH is the natural hormone that tells melanocytes, the pigment cells of the skin, to make more melanin. MT-2 is a cyclic heptapeptide: a ring of seven amino acids, closed by a chemical bridge that makes it far more stable than the natural hormone (Dorr 1996). It was designed at the University of Arizona by the team of Victor Hruby and Mac Hadley, alongside a longer straight-chain cousin called Melanotan I (Hadley and Dorr 2006).

The two molecules took different paths. Melanotan I went through formal development, was renamed afamelanotide, and was authorised in the EU in December 2014 as Scenesse, for a rare light-sensitivity disease (EMA). A modified version of MT-2, bremelanotide, was approved in the United States in June 2019 as Vyleesi, for low sexual desire in premenopausal women (FDA 2019). MT-2 itself was never approved anywhere. What exists on the market is a research compound, sold as a vial of powder or, more recently, as a nasal spray. This page describes what the published research found, and what it did not.

What the studies found

Only three human trials of MT-2 have been published, all from the same Arizona group, all in men.

The pilot phase 1 study (1996). Three healthy men received MT-2 under the skin on alternating days with saline, Monday to Friday, for two weeks. The starting amount was 0.01 mg per kg of body weight, raised in two men to 0.03 mg per kg and in one to 0.025 mg per kg. Two of the three men showed measurably darker skin on the face, upper body and buttocks one week after the last injection, measured by light reflectance. Mild nausea occurred at most amounts. At 0.03 mg per kg, one of two men had grade II sleepiness and fatigue. All three noticed stretching, yawning and spontaneous erections lasting one to five hours after each injection (Dorr 1996).

Erectile dysfunction, psychogenic (1998). Ten men whose erectile dysfunction had no known physical cause took part in a double-blind, placebo-controlled crossover study. Double-blind means neither the men nor the doctors knew which injection was which, and crossover means each man received both MT-2 and placebo at different visits. With MT-2 at 0.025 mg per kg, 8 of the 10 men developed a visible erection. The mean time with tip rigidity above 80 % was 38.0 minutes with MT-2 and 3.0 minutes with placebo. Nausea, stretching, yawning and lower appetite were more common after MT-2 (Wessells 1998).

Erectile dysfunction with organic risk factors (2000). Ten more men, this time with physical risk factors for erectile dysfunction, received MT-2 and placebo twice each. MT-2 produced an erection after 12 of 19 injections, placebo after 1 of 21. Mean rigid time was 45.3 minutes against 1.9. Reported sexual desire was higher after MT-2. Four of the 19 MT-2 injections caused severe nausea (Wessells 2000).

That is the whole trial record: 23 men, observed for hours or days. No trial measured long-term safety, included women or tested a nasal spray. Everything else known about MT-2 in humans comes from case reports of single patients.

What the case reports describe

A case report cannot prove that a substance caused an event. It records that the two happened together. With MT-2 these reports are the only safety data that exist.

Moles and melanoma. In 2009 dermatologists in Miami described a 40-year-old man with a history of melanoma who injected a synthetic alpha-MSH peptide and developed crops of new pigmented moles, many with atypical features under the microscope. Existing moles grew darker. After he stopped, the moles lightened and stopped growing (Cardones 2009). A 2019 review of 179 published patients with sudden outbreaks of new moles found that drugs, including melanotan, or immune-suppressing treatments were the suspected trigger in 41 % of cases, and that 16 % of patients had at least one mole confirmed as dysplastic, meaning abnormal (Burian 2019).

Melanoma itself has been reported several times. A 2011 report in the British Journal of Dermatology described a melanotan-associated melanoma (Paurobally 2011). In Denmark a 20-year-old woman with fair skin completed a three to four week course of MT-2 injections to boost sunbed tanning; three months later a black lesion on her buttock was removed and confirmed as melanoma (Hjuler 2014). A 2017 review from the Netherlands counted four published melanomas that arose from existing moles during or shortly after melanotan use, and concluded that conclusive evidence of a causal link was lacking (Habbema 2017). In 2025 surgeons in the UK reported a 22-year-old woman who had used an MT-2 nasal spray for tanning and developed a malignant melanoma of the mouth lining, treated by surgery and immunotherapy (Yassin Alsabbagh 2025).

Whole-body reactions. In Chicago a 39-year-old man injected an amount of 6 mg of MT-2 bought online. Two hours later his heart rate reached 146 beats per minute, he was sweating, shaking and anxious, and his muscle enzyme CPK climbed to 17,773 units per litre, a sign of muscle breakdown called rhabdomyolysis. He spent three days in intensive care. Mass spectrometry confirmed the substance was MT-2 (Nelson 2012). Swedish nephrologists reported a renal infarction, a blocked blood supply to part of a kidney, that they attributed to MT-2 (Peters 2020). In Glasgow a man arrived with priapism, an erection that would not end, after injecting melanotan into the abdomen. It was drained and treated with medication, and his erectile function had not recovered four weeks later (Dreyer 2019).

Where regulators stand

The Danish Medicines Agency first warned against Melanotan in 2008 and has repeated the warning since. Its page states that the product is not authorised in Denmark, Europe or the United States, that its effect is undocumented and that no studies of its side effects exist (Danish Medicines Agency). The 2025 UK case report describes MT-2 as unlicensed and its sale as illegal in the United Kingdom (Yassin Alsabbagh 2025). The 2017 review noted that multiple national health organisations had issued safety warnings (Habbema 2017).

In practice this means MT-2 is sold in Europe only as a research compound, for laboratory use. How to tell a serious research supplier from the rest is covered in How to choose a peptide supplier, and how to check a laboratory report is explained in How to read a Janoshik report. Readers interested in a skin peptide with a published human trial record may prefer our guide to GHK-Cu.

What the researchers flagged

• The trial record is tiny. 23 men, three studies, no follow-up beyond days. The authors of the 1996 study called it a pilot (Dorr 1996).
• Nausea was the most consistent effect, severe after 4 of 19 injections in the 2000 study (Wessells 2000).
• Moles changed. New and darkening moles are the most repeated finding in the case literature, and melanomas have been reported alongside use. Causation is unproven in either direction (Habbema 2017).
• Products bought online are untested. Several case reports concern people who did not know what amount they had taken. In the Chicago case the amount was six times what the patient believed to be a starting amount (Nelson 2012).