Rhythm Pharmaceuticals Soars 10.07% on Positive Trial Results

Rhythm Pharmaceuticals' stock surged by 10.07% in pre-market trading on July 9, 2025, driven by the release of positive Phase 2 trial results for their oral MC4R agonist, bivamelagon, in treating acquired hypothalamic obesity.

Rhythm Pharmaceuticals announced that their Phase 2 trial for bivamelagon demonstrated statistically significant BMI reductions of -9.3% and -7.7% in the 600mg and 400mg cohorts, respectively, at 14 weeks. These results were compared to a 2.2% increase in the placebo group, highlighting the drug's efficacy in reducing body mass index. The trial also showed that bivamelagon achieved meaningful reductions in hunger scores, with both higher-dose cohorts reporting a mean reduction of -2.8 points. The safety profile of the drug was manageable, with primarily gastrointestinal adverse events and limited instances of localized hyperpigmentation.

The company plans to pursue regulatory discussions with the FDA and EMA for Phase 3 trial design, indicating confidence in the results and the potential for bivamelagon to advance to pivotal studies for this rare disease indication. The high retention rate of patients continuing into the extension study further supports the drug's tolerability and perceived benefit. Rhythm Pharmaceuticals is also refining the formulation of bivamelagon to improve tolerability ahead of initiating a Phase 3 trial.