Rhythm Pharmaceuticals reports phase 2 PWS trial results

Rhythm Pharmaceuticals Inc. reported preliminary Phase 2 trial data showing setmelanotide reduced mean BMI by 3.06% in patients with Prader-Willi syndrome, according to a company press release presented at the Endocrine Society’s Annual Meeting in Chicago. The trial included 18 patients aged 6 to 23.

What were the trial results for setmelanotide?

A six-month analysis with a data cutoff of May 7, 2026, showed a mean BMI reduction of 3.06% across 17 patients who remained on active therapy. Adult patients saw a mean BMI reduction of 3.11%, while pediatric patients showed a mean reduction of 3.00% and a mean BMI z-score reduction of 0.35 from baseline.

Body composition data from 16 patients indicated a mean gain in lean mass of 0.74% and a mean loss in fat mass of 4.19%. Six of nine adults achieved a fat mass reduction greater than 5%, and five of seven pediatric patients gained at least 2.95% in lean mass.

The company reported behavioral improvements in several participants. Eight of 10 patients with moderate to severe hyperphagia saw a reduction of at least seven points on the Hyperphagia Questionnaire for Clinical Trials. Additionally, 10 of 15 patients with a baseline score above 11 on the PWS Anxiousness and Distress Behaviors Questionnaire showed an improvement of at least 11 points.

Did You Know? Prader-Willi syndrome is estimated to affect approximately 400,000 people worldwide.

How does this treatment fit into current medical approvals?

Setmelanotide is already approved by the FDA for specific obesity-related conditions. It is also authorized in the United Kingdom and the European Union for specific genetic obesity disorders, according to the company.

Safety and tolerability results for the PWS trial were consistent with the drug’s established profile, Rhythm Pharmaceuticals stated. The current trial data expands the potential application of the drug to the PWS population.

Expert Insight: Samantha Carter notes that the simultaneous reduction in fat mass and increase in lean mass, paired with behavioral improvements in hyperphagia, suggests the treatment may address both the physical and psychological drivers of weight gain in PWS patients.

What is the financial outlook for Rhythm Pharmaceuticals?

Rhythm Pharmaceuticals reported first-quarter 2026 net revenue of $60.1 million, exceeding the anticipated $55.62 million. The company has seen revenue growth of 59% over the last 12 months, though it reported a net loss of $0.83 per share.

PWS Clinical Trial Update Setmelanotide

InvestingPro analysis suggests the stock may be overvalued relative to its Fair Value. However, Stifel maintains a Buy rating with a price target of $133, and Citizens maintains a Market Outperform rating with a target of $155.

What may happen next?

The expansion of setmelanotide into Prader-Willi Syndrome could influence the company’s market presence. Analysts from Citizens indicated that this expansion may be a factor in their Market Outperform rating.

The company may continue to grow its reach following the early launch in acquired hypothalamic obesity. Rhythm Pharmaceuticals noted over 150 start forms from approximately 110 unique prescribers within the first six weeks of that launch.

Frequently Asked Questions

What was the mean BMI reduction for pediatric patients in the trial?
Pediatric patients demonstrated a mean BMI reduction of 3.00% and a mean BMI z-score reduction of 0.35 from baseline.

How did the drug affect fat mass in adult patients?
Six of nine adult patients achieved a reduction in fat mass of greater than 5%.

What was the company’s net revenue for the first quarter of 2026?
Rhythm Pharmaceuticals achieved a net revenue of $60.1 million.

How could these trial results change the management of Prader-Willi syndrome for patients and caregivers?