Rhythm Pharma posts Phase III data for setmelanotide in hypothalamic obesity before FDA decision

Edited by Robert McTiernan··3 min read

Boston-based Rhythm Pharmaceuticals announced additional data from the Phase III TRANSCEND trial evaluating setmelanotide in patients with acquired hypothalamic obesity, reporting a placebo-adjusted difference in BMI reduction of 18.8% across 142 patients at 52 weeks. The data arrive weeks before a US FDA decision on the company’s supplemental New Drug Application (sNDA) for the drug in this indication, with a PDUFA goal date of March 20, 2026. If approved, setmelanotide would become the first therapy specifically authorized for acquired hypothalamic obesity, a condition that currently lacks any approved pharmacological treatment.

Trial specifics

The TRANSCEND trial is a global, double-blind, randomized, placebo-controlled Phase III study in patients with acquired hypothalamic obesity. The dataset reported includes 142 patients: a pre-specified 120-patient pivotal cohort, 12 patients from a Japanese cohort, and 10 supplemental patients, randomized to receive either setmelanotide or placebo. The primary endpoint was mean percentage change in BMI from baseline at 52 weeks. Patients receiving setmelanotide (n=94) achieved a mean BMI reduction of 16.4%, compared with a mean BMI increase of 2.4% in the placebo group (n=48), yielding a placebo-adjusted difference of 18.8% (p<0.0001). In a secondary analysis of patients aged 12 and older (n=98), those on setmelanotide (n=66) showed an average weekly reduction of 2.5 points in the weekly most-hunger score, versus a 1.3-point reduction in the placebo group (n=32) (p=0.0015). Trial-specific adverse event data were not disclosed in this release, though the product label for setmelanotide lists skin hyperpigmentation, injection site reactions, nausea, headache, diarrhea, abdominal pain, vomiting, depression, and spontaneous penile erection as the most common adverse reactions (incidence ≥20%).

Rhythm first reported that the TRANSCEND trial met its primary and key secondary endpoints in April 2025 based on the 120-patient pivotal cohort. The additional data now incorporate the Japanese and supplemental patients. The company stated it would submit the final data package to the US FDA on March 2, 2026, ahead of the agreed-upon deadline. In parallel, the European Medicines Agency is reviewing a Type II variation submission for the same indication, with a Committee for Medicinal Products for Human Use (CHMP) opinion anticipated in Q2 2026 and potential marketing authorization in the second half of 2026. Rhythm also plans to submit a full data package to Japan’s Pharmaceuticals and Medical Devices Agency (PMDA) and seek marketing authorization there.

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Setmelanotide is already marketed under the brand name Imcivree, following 2020 US FDA approval for chronic weight management in adults and pediatric patients aged six years and older with obesity due to POMC, PCSK1, or LEPR deficiency confirmed by genetic testing. In June 2022, the FDA expanded the label to include obesity due to Bardet-Biedl syndrome (BBS). The European Commission authorized setmelanotide for genetically confirmed POMC/PCSK1 or LEPR deficiency in 2021, and subsequently for BBS in 2023. The UK’s MHRA has granted similar authorizations. Acquired hypothalamic obesity would represent a new and distinct indication for the drug.

Research context

Setmelanotide is a peptide agonist of the melanocortin-4 receptor (MC4R), a G-protein-coupled receptor expressed in hypothalamic neurons that functions as a central regulator of energy balance. Under normal physiology, alpha-melanocyte-stimulating hormone (α-MSH), derived from pro-opiomelanocortin (POMC), activates MC4R to promote satiety and increase energy expenditure. In acquired hypothalamic obesity, injury to the hypothalamus — most commonly from the growth or treatment of craniopharyngiomas, astrocytomas, or other hypothalamic-pituitary tumors, but also from traumatic brain injury, stroke, or inflammation — disrupts α-MSH production and impairs MC4R pathway signaling. The result is sustained weight gain, often accompanied by hyperphagia and reduced energy expenditure. By directly activating MC4R downstream of the site of injury, setmelanotide is designed to bypass the upstream defect and restore signaling through the pathway.

Rhythm estimates approximately 10,000 patients live with acquired hypothalamic obesity in the United States, roughly 10,000 in Europe, and between 5,000 and 8,000 in Japan. There is no approved pharmacotherapy for the condition. Current management relies on lifestyle interventions and, in some cases, bariatric surgery, which carries variable outcomes in this population due to the underlying hypothalamic dysfunction.