Rhythm Pharmaceuticals Inc. (RYTM) shares climbed Thursday after the company released preliminary results from an exploratory Phase 2 trial testing setmelanotide in patients with Prader-Willi syndrome, a rare genetic disorder that makes life incredibly difficult for those affected.
Prader-Willi syndrome is one of those conditions that hits from multiple angles. It starts with muscle weakness and feeding difficulties in infancy, then shifts gears entirely in childhood when patients develop insatiable hunger and a tendency toward severe obesity. Add in delayed development, intellectual disability, behavioral challenges, and physical traits like short stature, and you have a disorder that desperately needs effective treatments.
Rhythm enrolled 18 patients in this ongoing 52-week trial, and while the study hasn't wrapped up yet, the early signals look encouraging. Setmelanotide therapy showed potential therapeutic benefit by reducing both BMI and hyperphagia, which is the medical term for extreme, uncontrollable hunger that defines much of the PWS experience.
What the Numbers Show
The preliminary results, based on a data cutoff from mid-November, paint a picture worth paying attention to. Six of eight patients who reached the three-month mark saw their BMI drop from baseline. By Month 6, three of five patients achieved BMI reductions, with two of them showing even deeper improvements compared to Month 3, while one held steady.
Perhaps more importantly for quality of life, six of seven evaluable patients at Month 3 achieved meaningful reductions on the Hyperphagia Questionnaire, suggesting the treatment might actually help manage that relentless hunger that dominates daily life for PWS patients.
The retention numbers tell their own story: 17 of the 18 enrolled patients remain on active setmelanotide therapy. Safety and tolerability results have been consistent with setmelanotide's well-established clinical profile, which matters when you're talking about chronic treatment.
Looking Ahead
Based on these early results, Rhythm announced plans to advance setmelanotide into a Phase 3 registrational trial for PWS, though that depends on successfully completing the current Phase 2 study. The company is also expanding its PWS pipeline by initiating a Part D arm in the Phase 1 trial of MC4R agonist RM-718, which will enroll up to 20 patients with PWS. Rhythm expects to screen the first patient for this 26-week open-label trial in December 2025.
The PWS treatment landscape already has one approved option. Back in March, the FDA approved Soleno Therapeutics Inc.'s (SLNO) Vykat XR (diazoxide choline) extended-release tablets for hyperphagia in adults and children with PWS, giving families at least one tool to work with.
Price Action: RYTM stock closed up 14.24% at $119.69 on Thursday.
