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Setmelanotide (Imcivree)

Imcivree · BIM-22493 · RM-493

Animal replicated

FDA-approvedMelanocortin Agonist MC4R Agonist Cyclic Peptide

RouteInjectableFDA-approved

Evidence grade: Animal replicated

Effect demonstrated in multiple animal studies; human data sparse or extrapolated. Grades summarize evidence quality, not whether a compound is appropriate, legal, or risk-free.

At a glance

What it is: Selective MC4R Agonist — FDA Approved 2020 — Rare Genetic Obesity — Cyclic Octapeptide — Melanocortin Agonist, MC4R Agonist, Cyclic Peptide.
Why people use it: Used primarily for weight loss.

If you only read one thing

Setmelanotide achieves 80% ≥10% weight loss rates in POMC-deficient patients — among the highest responder rates of any obesity pharmacotherapy in clinical development. It restores something literally absent from these patients' neurobiology: the hypothalamic satiety signal. This precision medicine story is compelling, clearly evidenced, and appropriately approved. The tension is the community: setmelanotide is being sold and used by Polaris customers and the broader peptide community for general obesity, without genetic testing, without pathway deficiency confirmation. For the vast majority of people with obesity — who have an intact MC4R pathway that is overwhelmed by caloric surplus rather than absent — the evidence for setmelanotide's efficacy is essentially zero. Using the right drug for the wrong indication is not a small error.

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Published literature

3human RCTs2human studies3animal2in vitro

Counts reflect FDA-supporting setmelanotide trials in rare MC4R-pathway obesity and acquired hypothalamic obesity; common/polygenic obesity without pathway deficiency is not supported by the same evidence.

Evidence reality check

Human evidence

5 human studies

3 randomized; 2 observational.

Preclinical base

5 lab signals

3 animal; 2 in-vitro/mechanistic.

Risk posture

No major flags listed

Review route-specific cautions before use.

Categories

Weight Loss & Metabolic

Properties

✓ FDA-approved✓ Human RCT

Evidence

CAnimal replicated

The Genetic Indication

Setmelanotide is designed for patients with broken MC4R pathway signaling. Normal pathway: leptin from fat cells → LEPR on hypothalamic POMC neurons → POMC protein cleaved by PCSK1 enzyme → α-MSH/β-MSH peptides → bind MC4R → satiety signal ('stop eating'). In POMC deficiency: no melanocortin peptides produced → MC4R never activated → no satiety signal. In LEPR deficiency: leptin cannot signal POMC neurons → same downstream failure. In PCSK1 deficiency: POMC not cleaved into active peptides → same result. Setmelanotide bypasses all three upstream failures by directly activating MC4R.

Key Trial Results

Phase 3 POMC trial (Clément 2020, Lancet Diab Endocrinol; n=10; 52 weeks): 80% achieved ≥10% weight loss; mean hunger score -27.1% (p=0.0005). Phase 3 LEPR trial (same paper; n=11; 52 weeks): 45% achieved ≥10% weight loss; mean hunger score -43.7% (p<0.0001). VENTURE trial (Lancet Diab Endocrinol 2024; n=12; ages 2-5): mean -18% BMI at 1 year; -26% in POMC/LEPR subgroup; maintained and deepened at 18 months (-23.3%). Pilot Phase II (2 POMC patients): one patient lost 51 kg at week 42; complete reversal of hyperphagia. These are transformative results for patients who have been severely obese since infancy.

The Off-Label Problem

All clinical evidence for setmelanotide is in patients with genetically confirmed POMC/PCSK1/LEPR deficiency or BBS — rare mutations affecting perhaps 0.1% of the obese population. No trial has evaluated setmelanotide in common/polygenic obesity without these specific genetic defects. The MC4R pathway in common obesity is generally intact but overwhelmed by caloric excess, not absent. Setmelanotide replaces a signal that is missing; it is unknown whether additional MC4R agonism beyond normal physiological range produces meaningful weight loss in those whose pathway is functional.

Skin Hyperpigmentation — MC1R Off-Target

78% of patients in clinical trials develop skin hyperpigmentation. Mechanism: despite selectivity for MC4R over MC1R (>20-fold), setmelanotide still activates MC1R on skin melanocytes at clinical doses, driving eumelanin synthesis. This produces skin tanning, lip darkening, nevi (mole) darkening, and occasional hair color change. This is pharmacologically similar to but less pronounced than Melanotan II's tanning effect. Key difference from MT-II: no malignant skin changes have been observed in setmelanotide trials; systematic dermatological monitoring is built into clinical protocols. The melanoma concern that applies to MT-II applies to setmelanotide with somewhat less intensity but is not zero.

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Melanotan II (MT-II)

Same class · Melanocortin Agonist

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Melanotan 1

Same class · Melanocortin Agonist

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