Mechanism of Action
MT-II activates the full spectrum of alpha-msh/" class="wiki-internal-link">melanocortin receptors, producing multi-system effects simultaneously.
MC1R: Melanogenesis and Tanning
MC1R on melanocytes drives eumelanin (brown/black pigment) synthesis via cAMP-mediated upregulation of tyrosinase and MITF transcription factor. MT-II produces a full-body tan without UV exposure, though UV light during MT-II use dramatically accelerates and darkens the tan. Tanning begins 3-5 days into loading protocol.[1]MC3R and MC4R: Sexual Arousal
Central MC3R and MC4R activation in the hypothalamus and limbic system drives sexual arousal, the same pathway as PT-141. MT-II produces spontaneous erections in men without physical stimulation and significantly increases female arousal. This effect is more pronounced with MT-II than PT-141 due to additional MC3R/MC5R engagement.[2]MC4R: Appetite Suppression and Fat Metabolism
MC4R in the arcuate nucleus and PVN regulates energy homeostasis. MT-II activates these receptors to suppress appetite and increase energy expenditure. Chronic MC4R agonism produces significant fat loss in animal models, a pathway exploited in aod-9604/" class="wiki-internal-link">AOD-9604 and anti-obesity research.[3]Research Overview
Tanning and Photoprotection
Phase II ClinicalPhase II trials confirmed MT-II produces significant skin darkening via eumelanin synthesis without UV exposure. UV combined with MT-II dramatically amplifies tanning. Proposed photoprotective benefit for skin cancer prevention via increased melanin density has been explored but not clinically validated.[1]
Erectile Dysfunction
Phase II ClinicalPhase II trials in men with erectile dysfunction showed 80%+ response rate with MT-II, including cases unresponsive to PDE5 inhibitors. Central mechanism addresses neurogenic and psychogenic ED components. Spontaneous erections (without stimulation) are a characteristic effect.[2]
Weight and Metabolic Effects
Moderate EvidenceMC4R agonism from MT-II reduces food intake and increases resting energy expenditure in animal studies. Human observational data shows appetite suppression and modest weight reduction during tanning protocols. These effects are secondary to the primary melanogenic application.[3]
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Research Protocols
| Goal | Dose | Frequency | Route |
|---|---|---|---|
| Tanning, loading | 0.5–1 mg | Daily × 7-14 days (with UV) | Subcutaneous |
| Tanning, maintenance | 0.5 mg | 2–3× weekly | Subcutaneous |
| Sexual / ED protocol | 0.5–1 mg | As needed, 45-60 min before | Subcutaneous |
| Sensitivity start | 0.25 mg | Once daily | Subcutaneous |
For tanning: combine with moderate UV exposure (15-30 min) during loading for optimal results. Evening dosing reduces nausea interference with daily activities. For sexual function: dose 45-60 min before desired effect. Yawning and spontaneous erection are common onset signals. Nausea management: antihistamines (cetirizine or similar) taken 30 min before significantly reduce nausea.
Research protocols only. Not medical advice.
Interactions
Safety Profile
MT-II has significant side effects that distinguish it from the more selective PT-141.
Nausea and flushing: The most common and prominent side effects, occurring in 70-80% of subjects at doses above 0.5 mg. More intense than PT-141. Antihistamine pretreatment reduces significantly.
Spontaneous erections: MC4R-driven spontaneous erections can be prolonged and unwanted. Titrate dose carefully.
Hyperpigmentation: Existing moles and freckles can darken significantly. New nevi have been reported. Dermatological monitoring recommended during extended protocols.
Melanoma risk: UV exposure during MT-II use dramatically accelerates tanning but also increases UV damage to melanocytes. Risk of activating pre-malignant nevi is a theoretical concern. Dermatological surveillance is recommended.
No FDA approval: Research compound only. Not approved for any indication.
References
- [1]Hadley ME, Dorr RT. "Melanocortin peptide therapeutics: historical milestones, clinical studies and commercialization." Peptides. 2006;27(4):921-930.
- [2]Wessells H, et al. "Synthetic melanotropic peptide initiates erections in men with psychogenic erectile dysfunction: double-blind, placebo controlled crossover study." J Urol. 1998;160(2):389-393.
- [3]Murphy B, et al. "Melanocortin receptor agonists for the treatment of obesity." J Neuroendocrinol. 2000;12(10):1021-1028.