Side-by-side · Research reference
MT-1vsPE 22-28
Side-by-side comparison across mechanism, dosage, evidence, side effects, administration, and stack synergies. Citations on every claim where available.
AFDA-ApprovedHUMAN-REVIEWED9/51 cited
BAnimal-StrongHUMAN-REVIEWED16/47 cited
MT-1
α-MSH Analogue · FDA-Approved
SQ Implant · 60-Day Release
PE 22-28
TREK-1 Antagonist · Pre-Clinical
IP · SQ · Once Daily (animal models)Djillani 2017Pietri 2019
01Mechanism of Action
Parameter
MT-1
PE 22-28
Primary target
Melanocortin-1 receptor (MC1R) on melanocytesLangan 2010
TREK-1 two-pore-domain potassium channelDjillani 2017Ma 2020
Pathway
α-MSH analogue → MC1R activation → cAMP elevation → MITF transcription → eumelanin synthesis
TREK-1 channel blockade → Neuronal membrane depolarisation → Enhanced hippocampal excitability → Increased neuroplasticity
Downstream effect
Increased melanogenesis, photoprotection, reduced UV sensitivityLangan 2010
Antidepressant-like activity in forced swim test and tail suspension test; reduced A1-like reactive astrocyte activation; neuroprotection via NF-κB pathway modulationDjillani 2017Cong 2023Wu 2021
Feedback intact?
Yes — exogenous MC1R agonism does not suppress endogenous α-MSH production
N/A — direct ion channel blockade; not receptor-mediated endocrine axis
Origin
Synthetic 13-AA peptidomimetic with norleucine (position 4) and D-phenylalanine (position 7) substitutions for metabolic stabilityChawathe 2026
Synthetic truncation of spadin (PE 12-28), itself derived from the sortilin propeptide C-terminus. Residues 22-28: Val-Val-Arg-Gly-Trp-Leu-Arg.Djillani 2017Mazella 2018
Antibody development
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Not reported in animal studies
02Dosage Protocols
Parameter
MT-1
PE 22-28
Standard dose
16 mg subcutaneous implant
FDA-approved formulation (Scenesse).
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Frequency
Every 60 days
Sustained release implant — no daily administration required.
Once daily
Sustained antidepressant effect over 7+ days.
Evidence basis
Phase 3 RCT / FDA-approved orphan drug
Multiple rodent RCTs; behavioral + electrophysiology endpointsDjillani 2017Qi 2018Wu 2021
Indication
Erythropoietic protoporphyria (EPP)
Narrow FDA approval — not licensed for cosmetic tanning.
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Duration
Seasonal use (spring–autumn typical)
Aligned with peak UV exposure months.
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Route
Subcutaneous implant — upper arm or abdomen
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Stability
Norleucine/D-Phe substitutions enhance peptidase resistance
Modified structure vs endogenous α-MSH (Met⁴, L-Phe⁷).
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Animal dose (antidepressant)
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0.3–3 µg/kg IP
Effective in forced swim test, tail suspension test, CUMS models.
Animal dose (neuroprotection)
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0.03 µg/kg IPPietri 2019
Low-dose TREK-1 activation post-stroke for 7 days, then high-dose blockade.
Onset (animal)
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Within hours (acute); full effect 4–7 days
Comparison to fluoxetine
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PE 22-28 outperforms fluoxetine in CUMS-sensitive rats by day 7
Chronic administration shows superior long-term efficacy.
Human equivalent (extrapolated)
—
Not established — no clinical trials
Allometric scaling from rodent data unavailable.
04Side Effects & Safety
Parameter
MT-1
PE 22-28
Nausea
Common (>10%) — mild, transient
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Implant site reaction
Erythema, bruising, tenderness at insertion site
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Hyperpigmentation
Generalised tanning (therapeutic effect), darkening of freckles/neviLangan 2010Habbema 2017
Expected melanogenic response — complicates pigmented lesion surveillance.
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Melanocytic changes
Rapid pigmentation of existing nevi; new melanocytic lesions reported with unregulated useHabbema 2017
Requires dermatologic monitoring; theoretical melanoma concern with chronic stimulation.
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Headache
Occasional (MC1R-independent melanocortin effects)
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Photosensitivity (paradoxical)
Rare phototoxic reactions despite melanin increase
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Contamination risk (unregulated)
Impurity, infection, blood-borne virus transmission from illicit melanotan productsLangan 2010Habbema 2017
Applies to internet/gym-sourced 'melanotan' — not FDA-approved Scenesse.
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Toxicity (animal)
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No adverse effects reported at therapeutic doses
Cardiovascular (theoretical)
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TREK-1 expressed in cardiac tissue; arrhythmia risk unclear
Weight change
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Not reported in animal studies
Neurological
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No seizures or behavioral abnormalities noted
Long-term safety
—
Unknown — longest animal study 28 days
Absolute Contraindications
MT-1
- ·Hypersensitivity to afamelanotide or excipients
- ·Hepatic impairment (no safety data)
- ·Renal impairment (no safety data)
PE 22-28
- ·Human use — no clinical safety data available
Relative Contraindications
MT-1
- ·History of melanoma or atypical nevi (melanocortin receptor stimulation concern)Habbema 2017
- ·Pregnancy/lactation (insufficient data)
- ·Photosensitive dermatoses (other than EPP)
PE 22-28
- ·Cardiac arrhythmia or channelopathy (theoretical TREK-1 cardiac role)
05Administration Protocol
Parameter
MT-1
PE 22-28
1. Implant insertion
Performed by trained healthcare provider. Sterile technique. Small incision in upper arm (triceps) or lower abdomen using trocar. 16 mg rod (4 mm × 1.5 cm) inserted subcutaneously.
Dissolved in sterile saline or vehicle. Intraperitoneal injection, 0.3–3 µg/kg body weight. Once daily administration in rodent behavioral studies.
2. Site care
Pressure applied post-insertion. Sterile dressing × 24 hrs. Avoid strenuous activity for 24–48 hrs to prevent extrusion.
Shorter peptide length (7 AA) confers improved plasma stability vs 17-AA spadin. Exact storage conditions not detailed in published protocols.Djillani 2017
3. Release kinetics
Slow biodegradable polymer matrix releases afamelanotide over 60 days, maintaining therapeutic plasma levels without daily dosing.
Enhanced CNS bioavailability vs full spadin, likely due to smaller size. Mechanism (passive diffusion vs active transport) not fully characterized.
4. Repeat dosing
New implant every 60 days during high UV season (spring–autumn in temperate climates). Rotate implant sites to avoid scarring.
Not established — peptide synthesis methods for research use only. No pharmaceutical-grade formulation available.
5. Monitoring
Baseline and periodic dermatologic exams to document pigmented lesions. Patient education on self-examination for new/changing nevi.
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