MT-1 is selective for the pigmentation receptor, MC1R. MT-2 is not selective and also activates MC3R and MC4R, which is why it has effects beyond pigmentation and a longer list of reported adverse effects. MT-1, as afamelanotide, completed development as a registered medicine; MT-2 never did, and products containing it carry well-documented safety concerns.
| MT-1 from $50 | MT-2 from $70 | |
|---|---|---|
| Receptors | MC1R (selective) | MC1R, MC3R, MC4R |
| Structure | Linear | Cyclic, shorter |
| Research focus | Photoprotection, pigmentation | Pigmentation, melanocortin pharmacology |
| Reached registration | Yes, as afamelanotide | No |
| Regulatory standing | Registered product in some markets | No approval anywhere; known safety concerns |
| Developed by | Clinuvel Pharmaceuticals, Melbourne | University of Arizona research |
| Strengths stocked | 10MG | 10MG |
Both are analogues of alpha-MSH built for stability, and the pigmentation part of their activity is the same pathway. Where they part company is what else they touch.
MT-1 was developed by Clinuvel in Melbourne and registered in several markets as afamelanotide for erythropoietic protoporphyria — a rare condition in which sunlight causes severe pain. MT-2 was never developed to registration; PT-141 exists because one of its non-pigmentation effects proved interesting enough to pursue separately.
MC1R activation on melanocytes drives melanogenesis toward eumelanin, the pigment associated with photoprotection. That is the intended effect of both compounds. MC3R and MC4R sit elsewhere and are involved in appetite and arousal pathways, so a non-selective agonist produces effects that have nothing to do with pigment.
For research that is a confound: an observed effect with MT-2 could originate at any of three receptors. MT-1's selectivity is precisely what makes it the cleaner tool.
Unapproved injectable tanning products containing melanotan peptides raise safety concerns, including the risk of changes to skin lesions going unnoticed. Case reports in the dermatology literature include melanoma diagnosed in users, where causation is not established but the pattern prompted attention.
Native alpha-MSH is a 13-residue hormone cleared within minutes. Both compounds fix that, differently. MT-1 stays linear and substitutes two residues — norleucine at position 4 and D-phenylalanine at 7 — which resists degradation while leaving the molecule's shape close to the original. That similarity is why its receptor preference stays close to the hormone's: MC1R above the rest.
MT-2 goes further. It is shortened and cyclised, locking the peptide into a rigid conformation that resists breakdown and raises potency. The cost of that rigidity is selectivity: the constrained shape fits MC3R and MC4R as well as MC1R. Potency and promiscuity arrived together, which is the trade-off at the centre of any comparison between the two.
PT-141 exists because of that promiscuity. Researchers investigating MT-2 observed effects on sexual arousal that had nothing to do with pigment, traced them to a metabolite acting at MC4R, and developed that separately as bremelanotide — now an approved medicine in the United States.
MT-1 became afamelanotide, developed by Clinuvel Pharmaceuticals in Melbourne and registered in several markets for erythropoietic protoporphyria, a rare inherited condition in which sunlight causes severe pain. The registration trials measured pain-free light exposure, and the product is a controlled-release implant administered by a trained clinician. It is a genuinely Australian piece of peptide science and a rare example of a compound in this space completing the regulatory path.
MT-2 never entered formal development. What it has instead is a long history of unregulated use, and a case-report literature that comes from dermatology clinics rather than trials: reported adverse effects include nausea, flushing, and changes to existing naevi. Melanoma diagnosed in users appears in that literature, with causation unestablished, and it is the pattern that prompted regulatory attention.
Injectable tanning products containing melanotan peptides carry two distinct concerns: the products themselves are unapproved and unassessed, and changes to skin lesions can go unnoticed in people using a compound that alters pigmentation. Neither MT-1 nor MT-2 is registered in Australia as a research product.
Afamelanotide being registered in other markets does not change that. The registered product is a specific formulation for a diagnosed rare condition, prescribed and implanted by a clinician — a long way from a lyophilised research vial, and not interchangeable with one.
For melanocortin receptor pharmacology, the pair is genuinely informative precisely because they differ in selectivity. MT-1 isolates MC1R-mediated effects; MT-2 does not, so an effect observed with MT-2 and absent with MT-1 points toward MC3R or MC4R involvement. Used together they are a crude but real selectivity probe.
For pigmentation biology specifically, MT-1 is the cleaner instrument. MC1R activation drives melanogenesis toward eumelanin, which absorbs ultraviolet light more effectively than pheomelanin — the basis of the photoprotection research rather than the cosmetic interest.
MT-2 is among the most counterfeited peptides sold online, because demand for it comes overwhelmingly from outside research. Its cyclic structure is also a synthesis step that can be skipped: a linear peptide of the same residues has a similar mass, different behaviour, and is cheaper to make. Mass spectrometry distinguishes them; appearance does not.
The two are routinely confused with each other in the grey market, which matters more than it sounds — they have different receptor profiles, so a mislabelled vial produces results that are not wrong so much as about a different compound. Every OzPeptides batch of both is made and tested here at ≥99% HPLC purity with 0 ppm heavy metals.
MC1R sits on melanocytes, and activating it shifts melanin synthesis toward eumelanin — the darker, brown-black pigment — and away from pheomelanin, the red-yellow one. That shift is the whole basis of the photoprotection research, because eumelanin absorbs ultraviolet light considerably more effectively.
Variants in the MC1R gene are the main reason some people tan and others burn: loss-of-function variants are strongly associated with red hair, fair skin and poor tanning response. A compound that activates the receptor directly is therefore a way of studying the pathway in cells where the natural signal is weak, which is the genuinely interesting scientific question underneath a compound with an unfortunate reputation.
It also explains why neither compound is a sunscreen. Increased eumelanin is not equivalent to blocking ultraviolet light, and the photoprotection literature is careful about that distinction in a way the grey market is not.
Both are supplied lyophilised and both are light-sensitive in solution, which is worth more attention here than with most peptides — a compound studied for its interaction with ultraviolet light is not one to leave sitting on a bench in daylight.
Dry and cold, both are stable for long periods. Reconstituted and refrigerated, the useful window is measured in weeks, and bacteriostatic water rather than sterile water is what makes that window possible: the benzyl alcohol in it inhibits bacterial growth.
We make MT-1 and MT-2 in 10MG vials in Blacktown, NSW, tested at ≥99% HPLC purity with 0 ppm heavy metals. Both are supplied for in-vitro and laboratory research only, to buyers aged 18 and over, and neither is registered in Australia.
No. Increased eumelanin is not equivalent to blocking ultraviolet light, and neither compound is a sun-protection product.
Largely MC1R gene variants. Loss-of-function variants are strongly associated with fair skin, red hair and poor tanning response, which is why the receptor is studied at all.
Yes, they are the same peptide. The registered product is a controlled-release implant for a rare light-sensitivity condition, which is not interchangeable with a research vial.
It came out of MT-2 research. Effects on arousal unrelated to pigment were traced to a metabolite acting at MC4R, developed separately as bremelanotide.
Cyclisation locks it into a rigid conformation that raises potency and also fits MC3R and MC4R, not just the MC1R pigmentation receptor.
Clinuvel Pharmaceuticals in Melbourne. It is registered in several markets for erythropoietic protoporphyria, a rare light-sensitivity condition.
Injectable tanning products containing melanotan peptides are unapproved and unassessed, and changes to skin lesions can go unnoticed in people using a compound that alters pigmentation.
By mass spectrometry. Skipping the cyclisation step produces a peptide of similar mass and different behaviour, and appearance will not reveal it.
MT-1 is selective for MC1R, the pigmentation receptor. MT-2 is cyclic, shorter and non-selective, also activating MC3R and MC4R.
No. Neither MT-1 nor MT-2 is registered in Australia, and injectable tanning products containing melanotan peptides carry real safety concerns.
The same molecule. Afamelanotide is a registered implant for a rare light-sensitivity disorder — a different product from a research vial.
PT-141 (bremelanotide) is a metabolite of MT-2, developed separately for its MC4R-mediated effects on arousal.
This comparison summarises published research for educational purposes. It is not medical advice. OzPeptides products are sold for research and laboratory use only, not for human consumption. 18+ only.