Setmelanotide

Setmelanotide (brand name Imcivree) is a prescription medicine that reduces hunger and body weight in people whose brain is not getting the signal to stop eating. It works by switching on a receptor called MC4R that sits at the end of that signalling chain. It is FDA-approved for two groups whose signal fails in different ways: people born with a rare inherited fault in that chain, and people with hypothalamic obesity, where hunger begins after the appetite centre in the brain is damaged. It is not approved for common obesity and has not been shown to work there.

Setmelanotide has been studied in people born with rare gene faults that break the body's appetite-control pathway. In the two trials that led to approval, 8 of 10 people with POMC deficiency and 5 of 11 with LEPR deficiency lost at least 10% of their body weight over about a year, and reported large drops in hunger. A companion analysis found quality of life improved for most participants. The honest part: these were very small, mostly open-label studies in a rare population, run by the company that makes the drug, and nearly everyone got injection-site reactions and skin darkening. Nothing here says anything about how it would work in ordinary obesity, which it was not tested for.

FDA-approved prescription drug (Imcivree, Rhythm Pharmaceuticals). Approved to reduce excess body weight and maintain the reduction long term in two populations: obesity from specific, genetically confirmed faults in the leptin–melanocortin pathway (from age 2), and acquired hypothalamic obesity — which is not genetic at all — from age 4. Not approved for general or common obesity. This is a genuine prescription medicine dispensed through a pharmacy, distinct from the research-supply peptides elsewhere in this library. Approved indications, eligible genotypes and minimum ages verified against current FDA labeling (SPL v14, published 2026-04-02) on 2026-09-08 — see the Regulatory status section for the full table.[⁵] WADA status: setmelanotide is not named on the 2026 WADA Prohibited List, and no melanocortin drug class appears on that list (verified directly against the 2026 list text, 2026-08-04). Because setmelanotide holds regulatory approval for human therapeutic use, S0 (Non-Approved Substances) does not capture it — the opposite of the unapproved melanocortins elsewhere in this library, which are captured by S0 precisely because they lack approval. Athletes should still verify current status with their anti-doping organization. Not DEA-scheduled (prescription, non-controlled).

Setmelanotide is a prescription drug and should only be used under the care of a clinician who has confirmed an eligible diagnosis under one of its approved indications — a qualifying inherited gene variant, or acquired hypothalamic obesity. In the published trials, every single participant had injection-site reactions, and skin darkening occurred in every treated patient in a dedicated dermatology study — including darkening of moles and, in red-haired participants, a change in hair color. Because of that, regular skin examinations before and during treatment are recommended in the published literature. It is not named on the WADA Prohibited List and, being an approved medicine, is not captured by the S0 non-approved-substances category — but athletes should verify with their anti-doping organization. VialWise is a research and educational reference, not medical advice — consult a licensed professional.

⚠️ This is an approved prescription medicine, not a research peptide. Setmelanotide is dispensed by a pharmacy under a prescription and is used under clinical supervision. The reconstitution and self-dosing workflows used elsewhere in this library do not apply to it. Information here is informational, not medical advice.

⚠️ Approved only for genetically confirmed disease — not for general obesity. This is the single most important thing to understand about setmelanotide. Its approval rests on trials in people born with specific, rare, genetically confirmed faults in the leptin–melanocortin pathway. It has not been shown to produce meaningful weight loss in people without those variants, and it is not an alternative to the GLP-1 medicines covered elsewhere in this library. Seeing "MC4R agonist for obesity" and reading that as a general weight-loss drug is a misreading of the evidence.

⚠️ Note on evidence quality. The two registration trials were single-arm and open-label, enrolling ten and eleven participants respectively, with only a short blinded placebo-withdrawal window inside a mostly unblinded year.[¹] They were funded by Rhythm Pharmaceuticals, and company employees are co-authors.[¹] This is normal and largely unavoidable in a disease this rare — you cannot run a large blinded trial in a population of a few dozen people worldwide — but it means the evidence base is small and less robust than the trial phase number alone suggests.

Setmelanotide is a synthetic cyclic octapeptide agonist of the melanocortin-4 receptor (MC4R), developed by Rhythm Pharmaceuticals and marketed as Imcivree.

Mechanism. Body weight is regulated in part by the leptin–melanocortin pathway: leptin from fat tissue signals through the leptin receptor (LEPR), which drives production of pro-opiomelanocortin (POMC), which is cleaved by the enzyme PCSK1 into melanocortin peptides that activate MC4R and suppress hunger.[¹][⁴] Biallelic loss-of-function variants anywhere along that chain — in `POMC`, `PCSK1`, or `LEPR` — leave MC4R under-stimulated, producing relentless hunger (hyperphagia) and severe obesity from early childhood.[¹][⁴] Setmelanotide bypasses the broken upstream step by activating MC4R directly.

Evidence quality. The human evidence consists of two pivotal Phase 3 trials and their companion analyses:

- The registration trials were single-arm, open-label, multicenter studies run across ten hospitals in seven countries, enrolling 10 participants with POMC deficiency and 11 with LEPR deficiency.[¹] After 12 weeks of open-label treatment, participants who had lost at least 5 kg (or ≥5% if under 100 kg) entered an 8-week blinded withdrawal sequence alternating setmelanotide and placebo, then returned to open-label treatment for a further 32 weeks.[¹] At approximately 1 year, 8 of 10 (80%) POMC participants and 5 of 11 (45%) LEPR participants had achieved at least 10% weight loss.[¹] Mean change in the "most hunger" score was −27.1% in the POMC trial and −43.7% in the LEPR trial.[¹] - A quality-of-life analysis of the same 21 patients found moderate-to-severe baseline impairment, with improvement detectable by week 5; 5 of 6 adults with week-52 scores showed a clinically meaningful improvement.[²] Some patients did not improve, and the authors note that the psychological burden of a rare genetic disease may take longer than a year to shift.[²] - A natural-history analysis of 17 patients found that before setmelanotide these individuals sat above the 95th weight percentile throughout childhood and did not achieve durable weight loss from diet, exercise, or surgery.[⁴] This is the context that makes the trial results meaningful: the comparison is not against untried lifestyle change. - A dedicated dermatology study followed 5 patients for up to 46 months and found skin pigmentation increased in every treated patient, with darkening of lips and moles, and a change from red to brown hair in red-haired participants.[³] The authors attribute this to off-target activity at the closely related MC1R receptor and emphasize the need for regular skin examinations.[³] No malignant skin changes were seen in that small cohort — which is reassuring but far too small a sample to establish long-term skin-cancer safety.

Regulatory status (US). FDA-approved as Imcivree, to reduce excess body weight and maintain the reduction long term. Verified against current FDA labeling on DailyMed, 2026-09-08.[⁵] The approved population is broader than a purely genetic one, and the minimum age differs by indication:

Limitations of Use, from the label: Imcivree is not indicated where POMC/PCSK1/LEPR variants are classified benign or likely benign, nor for other obesity unrelated to acquired HO, BBS or those deficiencies — including obesity associated with other genetic syndromes and general (polygenic) obesity, "as IMCIVREE would not be expected to be effective."

Not DEA-scheduled.

Regulatory status (sport — WADA). Setmelanotide is not named on the 2026 WADA Prohibited List, and no melanocortin drug class appears anywhere on it (checked directly against the list text, 2026-08-04). Because S0 (Non-Approved Substances) applies only to substances with no current approval by any governmental regulatory health authority for human therapeutic use, and setmelanotide holds such approval, S0 does not capture it. This is a useful contrast with the unapproved melanocortin peptides elsewhere in this library, which fall under S0 for exactly that reason — the difference is regulatory approval, not chemistry. Athletes should verify current status with their National Anti-Doping Organization.

Common research interests. Setmelanotide appears in discussion mainly as (a) the first approved drug to treat obesity by targeting a specific genetic cause rather than the symptom, and (b) a clean demonstration that MC4R activation reduces hunger in humans. Neither of those makes it applicable to obesity without a confirmed pathway defect, which is the only setting it has been tested in.

Commonly reported

• Injection-site reactions — reported in every participant in both trials (10/10 POMC, 11/11 LEPR).[¹]
• Hyperpigmentation / skin darkening — reported in all ten POMC participants,[¹] and confirmed in every patient in the dedicated dermatology follow-up.[³]
• Nausea (5 participants) and vomiting (3 participants) in the POMC trial; nausea in 4 participants and skin disorders in 5 in the LEPR trial.[¹]
• No serious treatment-related adverse events occurred in either trial.[¹]

This is a prescription medicine. Use outside a prescribed, genetically confirmed, clinically supervised context is outside everything the evidence base covers.

Obesity without a confirmed pathway defect — setmelanotide has not been shown to work here and this is not an approved use.

Pre-existing skin lesions, many moles, or personal/family history of skin cancer — caution; documented MC1R-mediated pigmentation changes including darkening of nevi, with baseline and ongoing skin examination recommended in the published literature.[³]

Other melanocortin-active compounds — caution; setmelanotide already has documented off-target MC1R activity producing skin and hair pigmentation,[³] so combining it with other melanocortin agonists would compound that off-target effect. No data characterize any such combination.

Pregnancy and lactation — refer to current labeling; not addressed by the trials cited here.

Pediatric use — the registration trials enrolled participants aged 6 and older; minimum approved age is set by current labeling.

Regulatory note (sport): not named on the 2026 WADA Prohibited List and not captured by S0 because it holds regulatory approval. Verify with your anti-doping organization.

Not DEA-scheduled.

Peptide

A short chain of amino acids, the building blocks of proteins. Many compounds in this library are peptides.

MC4R (melanocortin-4 receptor)

A receptor in the brain that helps set how hungry you feel. When the signals reaching it are too weak, appetite can become very hard to control.

POMC / LEPR deficiency

Rare inherited conditions in which a gene in the appetite-control pathway does not work, causing severe obesity starting in early childhood. Diagnosis requires genetic testing.

Hyperphagia

Persistent, extreme hunger that does not settle after eating. It is the core symptom setmelanotide was designed to address.

Open-label

A study where everyone knows who is getting the drug. It is easier to run than a blinded study but more open to bias, so results carry less weight than a fully blinded trial.

1. Clément K, van den Akker E, Argente J, Bahm A, Chung WK, Connors H, De Waele K, Farooqi IS, Gonneau-Lejeune J, Gordon G, Kohlsdorf K, Poitou C, Puder L, Swain J, Stewart M, Yuan G, Wabitsch M, Kühnen P. (2020). 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. The Lancet Diabetes & Endocrinology, 8(12):960–970.(PMID 33137293 · NCT02896192)
2. Kühnen P, Wabitsch M, von Schnurbein J, Chirila C, Mallya UG, Callahan P, Gnanasakthy A, Poitou C, Krabusch PM, Stewart M, Clément K. (2022). Quality of life outcomes in two phase 3 trials of setmelanotide in patients with obesity due to LEPR or POMC deficiency. Orphanet Journal of Rare Diseases, 17(1):38.(PMID 35123544)
3. Kanti V, Puder L, Jahnke I, Krabusch PM, Kottner J, Vogt A, Richter C, Andruck A, Lechner L, Poitou C, Krude H, Gottesdiener K, Clément K, Farooqi IS, Wiegand S, Kühnen P, Blume-Peytavi U. (2021). A Melanocortin-4 Receptor Agonist Induces Skin and Hair Pigmentation in Patients with Monogenic Mutations in the Leptin-Melanocortin Pathway. Skin Pharmacology and Physiology, 34(6):307–316.(PMID 34058738)
4. Wabitsch M, Farooqi S, Flück CE, Bratina N, Mallya UG, Stewart M, Garrison J, van den Akker E, Kühnen P. (2022). Natural History of Obesity Due to POMC, PCSK1, and LEPR Deficiency and the Impact of Setmelanotide. Journal of the Endocrine Society, 6(6):bvac057.(PMID 35528826)
5. U.S. Food and Drug Administration, current prescribing information for IMCIVREE (setmelanotide) injection, Rhythm Pharmaceuticals, via DailyMed (NLM). SPL version 14, published 2026-04-02, setid `70c3ccf7-4df0-4c75-ba07-fede9970c8d9`; retrieved 2026-09-08. Cited for the indications and usage and Limitations of Use sections quoted above, including the acquired-hypothalamic-obesity indication and the per-indication minimum ages. dailymed.nlm.nih.gov

• Afamelanotide — same mechanism class
• Melanotan II — same mechanism class
• PT-141 (Bremelanotide) — same mechanism class
• Adipotide — shared research area
• Amycretin — shared research area
• AOD-9604 — shared research area