Rhythm Pharmaceuticals Inc. (NASDAQ:RYTM) stock is trading higher on Monday after the company reported preliminary results from an ongoing Phase 2 study evaluating setmelanotide in patients with Prader-Willi syndrome (PWS).
The six-month data shared on Saturday showed improvements in body mass index, body composition, hyperphagia, and behavioral measures.
The company presented the findings at the Endocrine Society’s Annual Meeting, ENDO 2026.
The trial enrolled 18 patients between the ages of 6 and 23 who met obesity-related eligibility criteria. As of June 12, 2026, 17 participants remained on active treatment in the 52-week study.
BMI And Body Composition Trends Show Improvement
According to the six-month analysis, patients receiving setmelanotide recorded a mean BMI reduction of 3.06% across 17 evaluable participants.
Adult patients experienced a mean BMI decline of 3.11%, while pediatric patients saw a mean reduction of 3.00%.
Among pediatric participants, the mean BMI z-score decreased by 0.35 from baseline.
Five of seven pediatric patients achieved a BMI z-score reduction greater than 0.2, which the company described as clinically meaningful.
DEXA scan data from 16 patients also showed favorable changes in body composition. Participants recorded an average 0.74% increase in lean mass and a 4.19% decrease in fat mass. Six of nine adults achieved more than a 5% reduction in fat mass, while five of seven pediatric patients gained at least 2.95% lean mass.
Hyperphagia And Behavioral Measures Improve
The study also showed improvements in hyperphagia, a hallmark symptom of PWS characterized by excessive hunger.
Of the 10 patients who entered the study with moderate-to-severe hyperphagia, eight achieved at least a seven-point reduction on the Hyperphagia Questionnaire for Clinical Trials score, meeting the threshold for clinically meaningful improvement.
Researchers also reported positive changes on the PWS Anxiousness and Distress Behaviors Questionnaire.
Safety Profile Remains Consistent
Rhythm said the safety and tolerability findings observed in the trial were consistent with the established profile of setmelanotide.
The Phase 2 study remains ongoing, with additional data expected as patients continue treatment through the 52-week evaluation period.
RYTM Price Action: Rhythm Pharmaceuticals shares were up 5.47% at $93.01 at the time of publication on Monday, according to Benzinga Pro data.
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