Setmelanotide (MC4R Agonist)
Also Known AsRM-493 · BIM-22493 · Imcivree
Developed by Rhythm Pharmaceuticals (originally identified at Ipsen). Setmelanotide is a cyclic octapeptide that selectively agonizes the melanocortin-4 receptor (MC4R). It was FDA-approved in 2020 (as Imcivree) for chronic weight management in patients 6 years and older with obesity due to POMC, PCSK1, or LEPR deficiency confirmed by genetic testing.
Ac-Arg-Cys(1)-D-Ala-His-D-Phe-Arg-Trp-Cys(1)-NH2How Setmelanotide Works
MC4R Agonism
Selectively binds and activates the melanocortin-4 receptor in the paraventricular nucleus of the hypothalamus. MC4R activation stimulates anorexigenic signaling through the secondary messenger cAMP, reducing food intake and increasing energy expenditure via sympathetic outflow.
Leptin-Melanocortin Pathway Restoration
In patients with POMC, PCSK1, or LEPR deficiency, the endogenous leptin signal fails to reach MC4R. Setmelanotide bypasses the upstream defect by directly activating MC4R, restoring the satiety signal that was functionally absent due to genetic pathway disruption.
Energy Expenditure Regulation
MC4R signaling increases sympathetic tone to brown and beige adipose tissue, enhancing uncoupling protein 1 (UCP1) expression and adaptive thermogenesis. This contributes to the weight loss observed beyond caloric restriction alone.
Published Research
Genetic Obesity (POMC/PCSK1/LEPR Deficiency)
StrongPhase III pivotal trials demonstrated mean body weight reductions of 25.6% in POMC-deficient patients and 12.5% in LEPR-deficient patients over 52 weeks. The responder rate (>10% weight loss) was approximately 80% in POMC deficiency. These results led to FDA approval in November 2020.
Bardet-Biedl Syndrome (BBS)
StrongA phase III trial in BBS patients demonstrated statistically significant weight loss compared to placebo, leading to an expanded FDA indication in June 2022. BBS involves ciliopathy-mediated disruption of melanocortin signaling, positioning MC4R agonism as a mechanistically targeted intervention.
Hypothalamic Obesity
EmergingEmerging data from phase II studies in patients with hypothalamic obesity (post-craniopharyngioma or other hypothalamic lesions) suggest setmelanotide may reduce hyperphagia scores and stabilize weight. The mechanism targets the intact MC4R downstream of the damaged hypothalamic circuitry.
Common Polygenic Obesity
EmergingPhase II data in common (non-monogenic) obesity showed modest weight loss effects. The MC4R pathway is one of many redundant satiety pathways in polygenic obesity, suggesting that single-target MC4R agonism may be insufficient as monotherapy in the general obese population.
Sexual Function & Melanocortin Signaling
PreclinicalMC4R activation modulates sexual arousal pathways. Clinical trial patients reported improved sexual function metrics as a secondary finding. The melanocortin system's role in sexual function is shared with bremelanotide (PT-141), which targets MC3R/MC4R for hypoactive sexual desire disorder.
Safety Profile
The most common adverse events in clinical trials were injection-site reactions (45%), hyperpigmentation (45%), and skin darkening due to melanocortin activation of MC1R in melanocytes. Spontaneous penile erections were reported in male patients. No serious cardiovascular events were attributed to setmelanotide. The FDA label includes a warning regarding the risk of depression and suicidal ideation, requiring monitoring.
Handling & Storage
Reconstitute with bacteriostatic water. Direct gentle stream along vial wall — do not shake. Store reconstituted solution at 2-8°C and use within 30 days. Lyophilized powder stable at -20°C for 24+ months. Protect from light — setmelanotide is photosensitive.
Peer-Reviewed Literature
- 1
MC4R agonism promotes durable weight loss in patients with leptin receptor deficiency
Clément K, Biebermann H, Farooqi IS, et al.
- 2
Efficacy and safety of setmelanotide, an MC4R agonist, in individuals with severe obesity due to LEPR or POMC deficiency: single-arm, open-label, multicentre, phase 3 trials
Clément K, van den Akker E, Argente J, et al.
- 3
Effect of setmelanotide, a melanocortin-4 receptor agonist, on obesity in Bardet-Biedl syndrome
Haws R, Brady S, Davis E, et al.
- 4
Proopiomelanocortin deficiency treated with a melanocortin-4 receptor agonist
Kühnen P, Clément K, Wiegand S, et al.
Setmelanotide FAQ
What is setmelanotide?
Setmelanotide is a cyclic octapeptide that selectively agonizes the melanocortin-4 receptor (MC4R) in the hypothalamus. It is FDA-approved (as Imcivree) for chronic weight management in patients with genetically confirmed POMC, PCSK1, LEPR deficiency, or Bardet-Biedl syndrome. It directly restores the downstream satiety signaling that is disrupted in these monogenic obesity disorders.
How does setmelanotide differ from other weight-loss peptides?
Unlike GLP-1 agonists (semaglutide) which work through incretin pathways, or tesofensine which modulates monoamine reuptake, setmelanotide directly targets the melanocortin-4 receptor — the final common signaling node in the hypothalamic leptin-melanocortin satiety pathway. It is uniquely effective in patients with upstream genetic defects in this pathway.
Why does setmelanotide cause skin darkening?
MC4R shares structural similarity with MC1R (the melanocortin-1 receptor on melanocytes). While setmelanotide is selective for MC4R, some cross-activation of MC1R occurs, stimulating melanin production. This results in skin and hair darkening in approximately 45% of treated patients. The effect is generally reversible upon discontinuation.
What is the purity of G26x Peptides setmelanotide?
Our setmelanotide is 99%+ purity, independently verified by Janoshik Analytical with a full Certificate of Analysis (COA) available for each batch. It is supplied as a lyophilized powder manufactured under GMP-adjacent conditions.
How should setmelanotide be stored?
Lyophilized setmelanotide should be stored at -20°C for long-term storage (stable for 24+ months). Once reconstituted with bacteriostatic water, store at 2-8°C protected from light and use within 30 days. Setmelanotide is photosensitive — avoid prolonged light exposure.
Setmelanotide Products
All compounds 99%+ purity, verified by Janoshik Analytical. GMP-manufactured lyophilized powder.
Setmelanotide
15mgMelanocortin appetite control — targets the brain's MC4R hunger circuits (the same system PT-141 uses for arousal), reducing food obsession while potentially boosting libido.
- FDA-approved for genetic obesity (MC4R pathway)
- Reduces hunger in leptin-resistant individuals
Explore Related Research
PT-141
10mgThe sex drive peptide — works directly in your brain to ignite genuine sexual desire and arousal in both men and women. FDA-approved mechanism. This is the one everyone's talking about.
- Directly increases sexual desire and arousal in both men AND women
- Works through the brain — not blood flow — for genuine desire, not just mechanics
AOD 9604
5mgThe fat-burning fragment of growth hormone — targets and destroys stubborn body fat (especially belly fat) without touching muscle, blood sugar, or hormone levels.
- Burns fat without affecting blood sugar or growth hormone levels
- Targets stubborn belly fat specifically
Disclaimer: This monograph is provided for educational and research purposes only. G26x Peptides products are sold exclusively as research chemicals. They are not intended for human consumption, therapeutic use, or as dietary supplements. All research should be conducted in compliance with applicable laws and institutional review board protocols. Information presented here is sourced from published peer-reviewed literature and does not constitute medical advice.