Rhythm Pharmaceuticals has shared early results from a Phase 2 study of a drug called setmelanotide in people with Prader-Willi syndrome (PWS). This is an exciting development because it directly targets hunger and weight regulation — two of the most challenging aspects of living with PWS.
The study was conducted by Dr Jennifer Miller, a physician who knows her patients with PWS very well. On 11th December, Dr Miller joined Rhythm Pharmaceuticals on a webcast and spoke with real excitement about the early results. You can listen to that in full at https://ir.rhythmtx.com/events/event-details/rhythm-preliminary-data-exploratory-phase-2-pws-trial
What the Study Showed
The study investigated setmelanotide, also known as Imcivree, which is already approved in countries such as the USA and UK for other conditions — but not yet for PWS.
Although the study was fairly small, the early results are promising:
- Many participants experienced lower BMI and improved body composition.
- Patients reported choosing to exercise more, feeling happier, and showing less irritability.
- The drug is given as a daily injection, but it was generally well tolerated. For many people with PWS, daily injections are already familiar through growth hormone treatment, so this was not a major barrier.
Why This Matters
Weight management and constant hunger are extremely difficult parts of PWS to manage. Families often ask whether weight loss drugs could help, and whilst some individuals with PWS do take weight loss medications under very careful medical supervision, the effects of weight loss drugs with PWS needs more research and studies such as this are very important and highly welcomed.
What’s happening now?
More data from this study is being collected and is expected in the first half of 2026. Rhythm Pharmaceuticals hopes to move forward with a larger Phase 3 trial, which would collect more data and — if results continue to be positive — could lead to applications for making this a treatment option for PWS.
This research is a hopeful step forward. It shows not only improvements in weight, BMI and body composition but also in wellbeing and daily life. For families living with PWS, it’s a reminder that progress is happening — and that the future of treatment is changing. We will be following this closely, and you can read more at https://ir.rhythmtx.com/news-releases/news-release-details/rhythm-pharmaceuticals-announces-preliminary-data-exploratory