Study Medication Proves Promising for Hypothalamic Obesity
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IMPORTANT UPDATE
July 2026 – Since this post was originally published, the Phase 3 TRANSCEND trial results have been released, marking a major milestone for acquired hypothalamic obesity (aHO). This research led to the first-ever FDA approval therapy for aHO, moving treatment from "investigational hope" to standard of care.
A Milestone in aHO Research
Research published in the New England Journal of Medicine from Dr. Christian Roth and colleagues show promising results from a phase 3 clinical trial to treat acquired hypothalamic obesity (aHO).
The phase 3 TRANSCEND trial was the largest and longest controlled study ever conducted for this rare condition, involving 120 patients across the globe. Study results found that patients treated with setmelanotide experienced a 16.5% reduction in Body Mass Index (BMI) over 52 weeks, compared to a 3.3% increase in the placebo group. Participants also saw a significant reduction in hunger.
Targeting the Root Cause: Precision Medicine for aHO
Setmelanotide is used to treat aHO by targeting the hypothalamic melanocortin-4 receptor (MC4R) pathway that controls hunger and food intake. Instead of using standard weight loss methods like diets and surgery, which are not as effective in resulting sustained weight loss in patients with aHO, this research points to targeted therapy—treating the underlying biological cause. By restoring the MC4R pathway, this treatment has the potential to shift the standard of care for patients with aHO who previously had few effective options.
Original Summary
Published June 20, 2024
The following section contains the initial Phase 2 study data that led to the recent breakthrough.
Research from the Norcliffe Foundation Center for Integrative Brain Research’s Dr. Christian Roth and colleagues testing the medication setmelanotide in a first-of-its-kind multicenter clinical trial showed significant reductions in weight and hunger in patients with hypothalamic obesity, long considered resistant to treatment. The phase 2 findings were recently published in The Lancet Diabetes & Endocrinology.
Hypothalamic obesity is a rare form of severe obesity that most commonly occurs after surgery or radiation to tumors affecting the hypothalamus part of the brain. The hypothalamus regulates the balance between consuming and burning calories; damage to this area affects people in different ways. Symptoms of hypothalamic obesity include uncontrollable hunger, rapid weight gain even when restricting calories and slow metabolism, which makes physical activity more difficult. The disorder affects multiple regulatory pathways of energy intake and expenditure in the brain as well as the regulation of the nervous system and hormones. Many patients undergo traditional obesity management strategies, including lifestyle and behavioral interventions, pharmaceutical approaches approved for general obesity and bariatric surgery, with inconsistent benefit.
Currently, there are no FDA-approved treatments specifically for hypothalamic obesity, highlighting a substantial unmet need. The medication setmelanotide targets the hypothalamic melanocortin-4 receptor pathway to control hunger and food intake. It is already approved by the U.S. Food and Drug Administration and the European Medicines Agency for rare conditions of obesity associated with monogenic mutations in the leptin–melanocortin pathway.
In this phase 2, open-label study conducted at five U.S. sites (including Seattle Children’s), Roth and colleagues investigated the effects of setmelanotide treatment for 16 weeks in 18 patients with hypothalamic obesity, ranging in age from 6 to 40 years. Promisingly, 89% of study participants experienced at least a 5% reduction in body mass index (BMI), with an average decrease in BMI of 15%, and no major safety issues, with only mild side effects observed. Additionally, patients older than 12 years showed an average of 45% reduction in hunger.
Sixteen of the 18 study participants reaching at least 5% weight loss in this pilot study were included in a long-term extension study still in progress. It has already shown setmelanotide caused 26% weight loss from baseline in patients completing a 12-month follow-up.
“The strong responsiveness might indicate a new drug mechanism by supplementing a deficient neuropeptide,” said Roth, a pediatric endocrinologist and a principal investigator at Seattle Children’s Research Institute, as well as a professor in the Division of Endocrinology, UW Medicine Department of Pediatrics. “Considering that weight gain is frequently intractable in patients with hypothalamic obesity, these findings hold promise for the development of effective and well tolerated treatments for the management of this complex condition.”
A larger, double-blind phase 3 clinical trial — an international study testing setmelanotide and a placebo in 120 patients with hypothalamic obesity — is underway.
The phase 2 and phase 3 studies were funded by Rhythm Pharmaceuticals.
— Colleen Steelquist