Imcivree becomes first obesity drug approved for a specific genetic cause

In late November 2020, the FDA approved Imcivree (setmelanotide) for chronic weight management in adults and children aged 6 and older with obesity due to POMC, PCSK1 or LEPR deficiency confirmed by genetic testing ^[3]. Rhythm Pharmaceuticals, which developed the drug, said it was the first FDA-approved therapy for these rare genetic diseases of obesity ^[3]. The prescribing information lists an initial U.S. approval in 2020 ^[2], and the drug's national drug code listing shows a marketing start date of December 14, 2020 ^[1].

A targeted drug, not a general weight-loss drug

Setmelanotide is a melanocortin-4 (MC4) receptor agonist given as a once-daily subcutaneous injection ^[2]. POMC, PCSK1 and LEPR deficiencies are caused by gene variants that impair the MC4 receptor pathway in the hypothalamus, which regulates hunger, energy expenditure and body weight, according to the company ^[3]. People with these conditions typically have extreme hunger starting at a young age and early-onset severe obesity ^[3].

The approval rested on two 52-week open-label studies. Among patients with POMC or PCSK1 deficiency, 80 percent lost more than 10 percent of their body weight; among patients with LEPR deficiency, 45.5 percent did ^[3]. The labeling states that Imcivree is not indicated for general (polygenic) obesity or for obesity associated with other genetic syndromes, and that it is not expected to work in people whose POMC, PCSK1 or LEPR variants are classified as benign or likely benign ^[2][3]. The label also notes that no FDA-approved test exists for detecting variants in those genes ^[2].

Bardet-Biedl syndrome and later label changes

The FDA later granted a supplemental indication for obesity due to Bardet-Biedl syndrome (BBS) in patients aged 6 and older, calling it the first drug approved specifically for chronic weight management in that condition ^[4]. That decision was based on a 66-week trial of 44 patients aged 6 and older with a clinical diagnosis of BBS and a body mass index of at least 30, or at least the 97th percentile for pediatric patients ^[4]. After 52 weeks of treatment, patients lost an average of 7.9 percent of their BMI; 61 percent lost at least 5 percent and 39 percent lost at least 10 percent ^[4].

The current prescribing information, revised in March 2026, lists three groups: patients aged 4 and older with acquired hypothalamic obesity, patients aged 2 and older with BBS, and patients aged 2 and older with POMC, PCSK1 or LEPR deficiency ^[2].

Safety information

The label lists warnings for disturbance in sexual arousal, including spontaneous penile erections, and instructs patients who have an erection lasting more than 4 hours to seek emergency care; depression and suicidal ideation; serious hypersensitivity reactions such as anaphylaxis; and skin hyperpigmentation, darkening of existing moles and new moles, which requires a full-body skin exam before and during treatment ^[2]. Additional warnings for patients with acquired hypothalamic obesity cover acute adrenal insufficiency and sodium imbalance ^[2]. The most common adverse reactions, each occurring in at least 20 percent of patients in at least one indication, include skin hyperpigmentation, injection site reactions, nausea, headache, diarrhea, abdominal pain, vomiting, depression and spontaneous penile erection ^[2]. The 2020 approval announcement listed a similar set and noted the drug is not approved for use in neonates or infants because of the benzyl alcohol preservative ^[3].

Why it matters for patients

Setmelanotide is not a GLP-1 medication. Semaglutide and tirzepatide act on gut-hormone and incretin pathways and are studied in broad populations; setmelanotide acts on the MC4 receptor pathway and is cleared only for obesity tied to a specific genetic or clinical diagnosis ^[2][3][4]. For someone with general obesity, the label explicitly states the drug is not expected to be effective ^[2][3].

That means diagnosis comes before treatment. For POMC, PCSK1 and LEPR deficiency, the label calls for genetic testing or a suspected deficiency; for BBS, a clinical diagnosis is used, with genetic confirmation to be considered in children under 6 ^[2]. Testing is not always straightforward, since the label says no FDA-approved test for those gene variants is available ^[2].

For patients who do qualify, the drug is a lifelong daily injection with a monitoring schedule that includes mood checks and skin exams ^[2]. It is also the reason the label has grown: three separate patient groups are now covered, and each expansion moved the eligible age lower ^[2].

What happens next

At the time of approval, Rhythm said it expected Imcivree to be commercially available in the United States in the first quarter of 2021 ^[3]. A marketing application was under review by the European Medicines Agency, which had granted the drug its PRIME designation ^[3]. A Phase 3 trial in people with Bardet-Biedl or Alström syndrome was enrolling, with topline data expected late in the fourth quarter of 2020 or early in the first quarter of 2021 ^[3]. The approval also came with a Rare Pediatric Disease Priority Review Voucher, which the company could use or sell ^[3]. Pricing for the U.S. launch was not disclosed in the approval announcement ^[3].