Setmelanotide for the Treatment of Acquired Hypothalamic Obesity

BACKGROUND: A phase 2 trial of setmelanotide, a melanocortin-4 receptor agonist, showed substantial weight loss in patients with acquired hypothalamic obesity, but additional data are needed. METHODS: We conducted a phase 3 trial in which participants were randomly assigned in a 2:1 ratio to receive setmelanotide (at a dose of 1.5 to 3.0 mg) or placebo administered subcutaneously once daily for 52 weeks after a dose-escalation period. Persons at least 4 years of age were potentially eligible for the trial if they had acquired hypothalamic obesity, which was defined by a body-mass index (BMI; the weight in kilograms divided by the square of the height in meters) that was at or above the 95th percentile for age and sex (for participants <18 years of age) or at least 30 (for participants ≥18 years of age) and a history of a hypothalamic tumor, lesion, or injury. The primary end point was the mean percent change in BMI from baseline to 52 weeks after the end of the dose-escalation period. Secondary end points included the mean change in the weekly average of the maximal daily hunger score (range, 0 to 10, with higher scores indicating more severe hunger), assessed in participants at least 12 years of age. RESULTS: From April 26, 2023, to March 18, 2025, a total of 120 participants were assigned to receive setmelanotide (81 participants) or placebo (39 participants). The mean (±SD) age was 19.9±13.8 years (range, 4 to 66). Among participants 18 years of age or older, the mean BMI was 41.2±9.7; the mean BMI z score among those younger than 18 years of age was 3.61±1.66. The least-squares mean (LSM) change in BMI at 52 weeks was -16.5% (95% confidence interval [CI], -19.3 to -13.8) with setmelanotide and 3.3% (95% CI, -0.6 to 7.2) with placebo (P<0.001), and the LSM change in the weekly average of maximal daily hunger scores was -2.73 (95% CI, -3.28 to -2.18) in the setmelanotide group and -1.45 (95% CI, -2.23 to -0.67) in the placebo group (P = 0.009). Adverse events were reported in 100% of the participants in the setmelanotide group and in 90% of those in the placebo group, and serious adverse events were reported in 28% and 8%, respectively. The most common adverse events with setmelanotide were skin hyperpigmentation, nausea, vomiting, and headache. CONCLUSIONS: Setmelanotide led to significantly greater reductions in BMI and hunger than placebo at 52 weeks among participants 4 to 66 years of age with acquired hypothalamic obesity. (Funded by Rhythm Pharmaceuticals; TRANSCEND ClincialTrials.gov number, NCT05774756.).