Imcivree (setmelanotide) approved for rare genetic obesity

The U.S. Food and Drug Administration approved Imcivree (setmelanotide), a melanocortin-4 (MC4) receptor agonist from Rhythm Pharmaceuticals, for chronic weight management in adults and children 6 years and older with obesity caused by proopiomelanocortin (POMC), proprotein convertase subtilisin/kexin type 1 (PCSK1) or leptin receptor (LEPR) deficiency confirmed by genetic testing ^[3]. Rhythm announced the approval on November 27, 2020, calling it the first FDA-approved therapy for these rare genetic diseases of obesity ^[3].

The drug is a once-daily injection given under the skin, supplied as a 10 mg/mL solution in a 1 mL multiple-dose vial ^[1][2]. It is sold under application number NDA 213793, and openFDA lists a marketing start date of December 14, 2020 ^[1]. At the time of approval, Rhythm said it expected Imcivree to be commercially available in the U.S. in the first quarter of 2021 ^[3].

What the trials showed

The approval rested on two 52-week open-label trials ^[3]. After one year of treatment, 80% of patients with obesity due to POMC or PCSK1 deficiency lost more than 10% of their body weight, as did 45.5% of patients with LEPR deficiency ^[3].

These conditions are ultra-rare. Variants in the POMC, PCSK1 or LEPR genes impair the MC4 receptor pathway in the hypothalamus, which helps regulate hunger, energy use and body weight ^[3]. People with these conditions describe extreme, insatiable hunger starting at a young age, leading to early-onset severe obesity ^[3]. Setmelanotide is designed to restore activity in that pathway ^[3].

The label is explicit about who the drug is not for. It is not indicated for obesity linked to POMC, PCSK1 or LEPR variants classified as benign or likely benign, or for other types of obesity, including obesity tied to other genetic syndromes and general (polygenic) obesity ^[2][3].

Safety warnings at approval included disturbance in sexual arousal, with instructions that males with an erection lasting longer than 4 hours seek emergency care; depression and suicidal ideation; and increased skin pigmentation and darkening of existing moles, with a full-body skin exam before starting and periodically during treatment ^[3]. The most common adverse reactions (incidence 23% or higher) were injection site reactions, skin hyperpigmentation, nausea, headache, diarrhea, abdominal pain, back pain, fatigue, vomiting, depression, upper respiratory tract infection and spontaneous penile erection ^[3]. Imcivree is not approved for use in neonates or infants ^[3].

With the approval, FDA issued Rhythm a Rare Pediatric Disease Priority Review Voucher, which can be redeemed for priority review of a future application or sold to another company ^[3]. Setmelanotide had previously received Breakthrough Therapy designation and orphan drug designation ^[3].

Why it matters for patients

Imcivree is a different kind of obesity drug from GLP-1 medicines such as semaglutide (Ozempic, Wegovy, Rybelsus) or tirzepatide (Mounjaro, Zepbound). It targets a defined genetic defect, and the label says it would not be expected to work in common polygenic obesity ^[2][3]. That means eligibility depends on a diagnosis, not on BMI alone.

It also puts genetic testing at the center of care. For POMC, PCSK1 or LEPR deficiency, the label directs selection of patients with genetically determined or suspected deficiency, and treatment of variants interpreted as pathogenic, likely pathogenic, or of uncertain significance in the patient's clinical context ^[2]. The label notes that an FDA-approved test to detect these variants is not available ^[2].

Monitoring requirements are also different from GLP-1 drugs: skin exams for pigment changes and moles, and watching for new or worsening depression or suicidal thoughts ^[2][3][4].

What happens next

FDA later approved a supplemental indication for chronic weight management in adults and children 6 and older with obesity due to Bardet-Biedl syndrome (BBS), making Imcivree the first drug approved specifically for weight management in BBS ^[4]. That decision was based on a 66-week trial in 44 patients ages 6 and older with a clinical BBS diagnosis and obesity, with a 14-week randomized, double-blind, placebo-controlled period followed by 52 weeks open-label ^[4]. After 52 weeks, patients lost an average of 7.9% of their BMI; 61% lost 5% or more of BMI and 39% lost 10% or more ^[4].

The current prescribing information, with sections revised in 03/2026, lists indications for acquired hypothalamic obesity in patients 4 and older, and BBS or POMC, PCSK1 or LEPR deficiency in patients 2 and older ^[2]. Warnings now also cover hypersensitivity reactions, acute adrenal insufficiency in acquired hypothalamic obesity, and sodium imbalance in patients with central diabetes insipidus ^[2].