Gathering the record
Relay is organizing the evidence and source boundaries.
Synthetic cyclic alpha-MSH analogue and nonselective melanocortin receptor agonist
MT-2 is an experimental peptide best known for producing darker skin pigment and, in small early studies, erections and increased sexual desire. Those effects are real research signals, but MT-2 is not FDA approved, long-term human safety is unknown, and products sold online may not contain what their labels claim.
60-Second Overview
Start with what it is, why it matters, what research has shown, and what remains unknown. The science follows after the orientation.
Start here. These four answers explain why the compound matters before the page introduces the deeper science.
Melanotan II, or MT-2, is an experimental peptide that activates several melanocortin signals involved in skin pigment, appetite, and sexual responses.
Early researchers studied whether those signals could increase pigmentation or trigger erectile responses. The same broad receptor activity makes nausea, spontaneous erections, appetite changes, pigment effects, and uncertain long-term safety central to the record.
Tiny controlled human studies found measurable pigmentation and erectile responses, but the largest relevant studies enrolled only ten men and monitored short-term effects. Later safety knowledge relies heavily on case reports, forensic product testing, and regulatory warnings.
Repeated-use safety, pigment-related risk, outcomes outside small male studies, long-term neurologic or cardiovascular effects, and commercial-product identity remain unresolved. MT-2 is not approved and darker skin is not proven protection from ultraviolet injury.
The research depth, routes, studies, and primary sources below explain how Relay knows—and where the evidence stops.
Research context
Published research has investigated this compound using the following study designs.
These records explain what researchers did. They are not instructions, recommendations, or a transferable protocol.
A small controlled crossover study investigated short-term erectile and adverse-effect responses in men with psychogenic erectile dysfunction.
Reported study administration—not a recommendation.
Research at a glance
Evidence depth, confidence, and route context explain how Relay knows—not what anyone should do.
Human administration evidence consists mainly of three tiny 1990s SubQ studies, while current development and safety information includes a registered trial, case reports, and product-quality findings.
Research depth describes how large and mature the overall record is. It does not tell you whether the results were positive.
No approved product, modern confirmatory program, established long-term safety dataset, or validated retail formulation exists.
Confidence describes how reliable and consistent the conclusions are. It can be high for one outcome and low for another.
The strongest evidence type shows what the best-supported conclusions are actually based on.
Human findings are more directly relevant than animal or laboratory results, but they still apply only to the populations and outcomes studied.
Route-specific record
These are exposures used in cited research for a specific route and population—not an instruction for an individual.
Half-life describes how long it takes the measured amount in the body to fall by half. It is not a dosing recommendation.
Evidence can change by administration method. Findings from one route should not automatically be applied to another.
Evidence boundary: Only ten men were studied, with six hours of monitoring per condition. The record does not establish long-term treatment, tanning safety, outcomes in broader populations, or equivalence to unregulated products. Amounts shown describe cited research exposure—not a dosage recommendation.
Detailed evidence
Start with the strongest supported conclusion and its main uncertainty. Claim-level records below show how the evidence changes by question, population, route, formulation, and study design.
Two ten-person placebo-controlled crossover erectile-response studies and one three-person pigmentation Phase 1 pilot.
This is the strongest supported conclusion in the current human evidence—not a summary of every claim made about the compound.
Long-term and repeated-use safety, actual risk of pigmentary or neurologic complications, outcomes outside small male studies, and whether unregulated products match the studied compound.
Keeping the main uncertainty visible prevents an early or promising finding from looking more settled than it is.
Questions people bring to the evidence
Research questions—not promises of benefit.
MT-2 is not receptor-selective like the practical shorthand often used for MT-1. Its melanocortin activity helps explain pigmentation, nausea, appetite effects, yawning, erections, and sexual-desire signals.
Two participants were visibly and instrumentally darker after the short Phase 1 experiment.
Each crossover study enrolled ten men and used short-term rigidity monitoring after MT-2 and placebo.
The organic-ED crossover study recorded increased desire alongside erectile responses.
These were observed pharmacologic effects—not community folklore—and severe nausea occurred during some controlled exposures.
MT-2 remains an unapproved drug in the United States; a substance identity record or a registered study does not mean approval.
FDA specifically points to aggregation or peptide-related impurities and reports involving melanoma, posterior reversible encephalopathy syndrome, sympathomimetic toxidrome, and priapism.
These reports are safety signals that matter even though they cannot tell us how often events occur.
A 2025 report described oral mucosal melanoma after nasal-spray use, and FDA cites melanoma among published serious-event reports.
Pigment production and proven sun protection are different claims. Regulators continue to advise standard sun protection.
Reduced appetite appeared as a short-term effect in early human experiments, while weight and fat-loss claims primarily come from animal research or anecdotes.
The sponsor-submitted ClinicalTrials.gov record plans to compare MT-2 plus narrowband UV-B with placebo plus narrowband UV-B.
A forensic report confirmed MT-II in one labeled vial but measured only 30% purity.
Published experiments describe research-protocol injections, but MT-2 has no approved U.S. product label that validates instructions for vials, nasal sprays, or other retail forms.
Mechanisms
Melanotan II is a cyclic heptapeptide alpha-MSH analogue with agonist activity across MC1R, MC3R, MC4R, and MC5R-related pathways. A three-person Phase 1 pilot recorded pigmentation, nausea, fatigue or somnolence, yawning, and spontaneous erections. Two ten-person placebo-controlled crossover studies found erectogenic and sexual-desire signals in men with erectile dysfunction. No modern pivotal efficacy or long-term safety program was located. FDA identifies immunogenicity, aggregation, peptide-related impurities, and serious published adverse-event reports as compounding concerns. Case reports describe rhabdomyolysis, renal injury or infarction, priapism, and temporally associated melanoma, without establishing incidence or certain causality.
A plausible mechanism can explain why a study was attempted. It does not prove that the compound improves a human outcome.
Studies
Study arms are reported for transparency. They describe what researchers did in a defined record and do not transfer across identities, routes, formulations, or populations.
A later trial phase can ask a more mature question, but it does not guarantee a positive result, regulatory approval, or relevance outside the studied population.
Double-blind, placebo-controlled crossover study
Ten men with erectile dysfunction and organic risk factors
Erections and sexual-desire ratings occurred more often after MT-II than placebo. Nausea and yawning were frequent, and four of nineteen MT-II exposures caused severe nausea.
Study administration: Two protocol-defined 0.025 mg/kg subcutaneous MT-II exposures and two vehicle exposures per participant
Limitations: Only ten men were enrolled. Monitoring lasted six hours, repeated-use safety was not established, and the findings do not validate recreational products or establish an approved sexual-function treatment.
Double-blind, placebo-controlled crossover study
Ten men with psychogenic erectile dysfunction
Eight of ten men developed clinically apparent erections after MT-II. Mean time with high tip rigidity was longer than with placebo.
Study administration: A protocol-defined 0.025 mg/kg subcutaneous MT-II exposure and vehicle placebo on separate study occasions
Limitations: This was a small, short crossover experiment from 1998—not an approval trial, not long-term treatment evidence, and not a dosing recommendation. Nausea, yawning, stretching, and reduced appetite occurred more often with MT-II.
Single-blind, alternating-day, saline-controlled dose-escalation pilot
Three healthy male volunteers
Two of three participants showed increased pigmentation after the study. Nausea was common, one participant developed grade II somnolence and fatigue at the highest studied level, and spontaneous erections occurred.
Study administration: Subcutaneous MT-II or saline on alternating weekdays; MT-II was escalated from 0.01 mg/kg to 0.025 or 0.03 mg/kg under the study protocol
Limitations: This was a three-person 1996 pilot in men, far too small and short to establish a safe or effective tanning regimen, long-term safety, outcomes in women, or equivalence to products currently sold as MT-2.
Case report with literature review
One 22-year-old woman with oral mucosal malignant melanoma after reported MT-II nasal-spray use
The report documents temporal exposure before diagnosis and discusses MT-II as a possible risk factor.
Study administration: Reported unlicensed nasal-spray exposure
Limitations: A single case cannot establish that MT-II caused melanoma. Route, product identity, dose, other risk factors, and the natural occurrence of disease prevent causal inference.
Laboratory identification and purity analysis of submitted material
One analyzed vial labeled Melanotan II
Reference-standard mass spectrometry confirmed MT-II in the vial, but measured purity was only 30%.
Study administration: No clinical intervention
Limitations: One forensic sample does not describe every vendor or product. It demonstrates why a label alone cannot establish identity, concentration, purity, sterility, or safety.
Case report
One man with prolonged ischemic priapism after a tanning injection
The report described prolonged ischemic priapism that did not resolve with initial treatment and required surgical decompression.
Study administration: Reported Melanotan II tanning-product exposure
Limitations: This rare case cannot estimate incidence or confirm the composition of the product, but it is consistent with the erectogenic pharmacology observed in controlled human studies.
Case report with literature review
One person with renal infarction after reported MT-II use
The authors reported a renal infarction they considered most likely related to MT-II exposure.
Study administration: Reported Melanotan II exposure
Limitations: This is a single observational case. It raises a safety signal but cannot prove causality, estimate frequency, or separate peptide effects from product-quality and patient-specific factors.
Emergency-department case report
One 39-year-old man after self-injecting Internet-purchased material labeled Melanotan II
The report described anxiety, sweating, diffuse pain, sympathomimetic toxicity, rhabdomyolysis, and renal dysfunction after exposure.
Study administration: Unregulated self-administered product exposure
Limitations: A single case cannot establish incidence or prove that chemically verified MT-II alone caused the event. The product was Internet-purchased, so identity, purity, contamination, and actual dose were uncertain.
Sponsor-submitted randomized, quadruple-masked, placebo-controlled parallel trial
Planned enrollment of adults with stable nonsegmental vitiligo
No results were posted by the July 25, 2026 evidence cutoff.
Study administration: Investigational MT-II or placebo as an adjunct to standardized narrowband UV-B phototherapy
Limitations: ClinicalTrials.gov displays information submitted by the sponsor. Registration does not show that the trial will finish, that its product is equivalent to retail MT-2, that the treatment works, or that any regulator has endorsed it.
Safety snapshot
FDA identifies potential significant safety concerns for compounded MT-2, including immunogenicity and published serious adverse-event reports.
Other human evidenceFDA's risk entry is not an incidence estimate and does not prove causality for every reported event.
Open sourceThe current record does not support a reliable common-versus-uncommon frequency split.
Evidence boundaryUnder-detected or under-reported events must not be described as rare.
FDA identifies potential significant safety concerns for compounded MT-2, including immunogenicity and published serious adverse-event reports.
Other human evidenceFDA's risk entry is not an incidence estimate and does not prove causality for every reported event.
Open sourceThe current record does not identify a reliable compound-specific pattern of events that caused study discontinuation.
Evidence boundaryThis is an evidence gap, not proof that discontinuations did not occur.
No compound-specific patient-facing urgent-action threshold is established in the current Relay record.
Evidence boundaryRelay does not infer emergency guidance from study discontinuations, mechanism, or incomplete adverse-event reporting.
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