Rhythm Pharma Announces Preliminary Results From Exploratory Phase 2 Trial Of Setmelanotide In Patients With Prader-Willi Syndrome

-- BMI and hyperphagia reductions have been observed in patients with PWS treated with setmelanotide at Month 3 (n=8) and Month 6 (n=5); 17 of 18 enrolled patients remain on therapy --

-- Promising results supportive of Phase 3, registrational trial of setmelanotide in PWS --

-- Company initiated Phase 1, Part D study to evaluate weekly MC4R agonist RM-718 in patients with PWS --

-- Company to hold conference call on Thursday, December 11 at 8:00 a.m. --

BOSTON, Dec. 11, 2025 (GLOBE NEWSWIRE) -- Rhythm Pharmaceuticals, Inc. (NASDAQ:RYTM), a global commercial-stage biopharmaceutical company focused on transforming the lives of patients living with rare neuroendocrine diseases, today announced positive preliminary results from its exploratory Phase 2 trial of setmelanotide in patients with Prader-Willi syndrome (PWS).

The Company also announced plans to advance setmelanotide into a Phase 3 registrational trial in PWS, pending successful completion of this Phase 2 trial. Rhythm also announced that it has initiated a Part D arm in the Phase 1 trial of MC4R agonist RM-718 that will enroll up to 20 patients with PWS. Rhythm anticipates screening the first patient for this 26-week open-label trial of RM-718 in December 2025.

Rhythm enrolled 18 patients with PWS aged 6-65 years old with a BMI ≥30 kg/m2 for patients ≥18 years of age or BMI ≥95th percentile for age and sex for patients younger than 18. The 52-week trial remains ongoing.

Setmelanotide therapy demonstrated potential therapeutic benefit with BMI and hyperphagia reductions in patients with PWS at Month 3 (n=8) and Month 6 (n=5); Highlights from preliminary results, as of a cut-off date of Nov. 14, include:

• Six (6) of 8 patients who reached Month 3 of setmelanotide therapy achieved BMI reductions from baseline;
• Three (3) of 5 patients who reached Month 6 of setmelanotide therapy achieved reductions in BMI, with two seeing deeper reductions versus Month 3 and one unchanged;
• Six (6) of 7 evaluable patients who reached Month 3 of setmelanotide therapy achieved meaningful reduction in Hyperphagia Questionnaire for Clinical Trials1 (HQ-CT) scores; one patient's baseline and Month 3 HQ-CT score was 0, therefore not evaluable;
• Seventeen (17) of the 18 patients enrolled remain on active setmelanotide therapy; and
• Safety and tolerability results have been consistent with setmelanotide's well-established clinical profile.