Setmelanotide

What the evidence says

Setmelanotide activates the melanocortin-4 receptor downstream of specific disrupted hunger pathways. Current FDA approval is limited to acquired hypothalamic obesity and obesity from Bardet-Biedl syndrome or confirmed POMC, PCSK1, or LEPR deficiency at defined pediatric and adult ages; it is not indicated for ordinary polygenic obesity.^[1]

In small phase 3 studies of POMC or LEPR deficiency, 80% and 45% of participants respectively achieved at least 10% weight loss at about one year, alongside reduced hunger. These were open-label rare-disease trials with withdrawal periods, and the denominators were only 10 and 11 participants.^[2]

A randomized Bardet-Biedl trial found 32.3% of participants aged 12 or older achieved at least 10% loss after 52 weeks. In a 2026 randomized trial of 142 people with acquired hypothalamic obesity, the placebo-adjusted BMI difference after 52 weeks was about 18.4 percentage points, leading to the expanded indication.^[3][4][1]

Daily injection-site reactions and marked skin darkening are common. The label also warns about sexual adverse reactions, depression or suicidal ideation, and benzyl-alcohol toxicity in neonates and low-birth-weight infants. Diagnosis and treatment require specialist supervision, genetic or clinical confirmation, and ongoing response and mental-health monitoring.^[1][5]