Rapport Therapeutics' experimental drug RAP-219, originally developed for epilepsy, has surprised analysts by narrowly hitting the primary endpoint in a Phase 2 trial for bipolar mania. In the study of about 250 adults, patients taking the drug improved by an average of 15.4 points on a 60-point mania severity scale after three weeks, versus 12.3 points for placebo—a 3.1-point difference that just reached statistical significance. The company also reported improvements across all 11 components of the scale and on a secondary mania measure, with mild-to-moderate side effects and similar incidence to placebo.
Analysts had low expectations for the trial, and the outcome was described as a "clear positive" that validates the drug's mechanism. However, Stifel's Paul Matteis noted the efficacy data were close to missing significance and at the lower end of the range considered competitive with existing bipolar medications. Jefferies' Andrew Tsai said the safety profile looked clean and that continued success could add more than $1 billion to peak sales estimates, potentially emboldening the company to explore other CNS indications like bipolar depression.
Rapport plans to meet with the FDA in the first quarter of next year to discuss the results and design of registration trials. Two late-stage studies in acute bipolar mania are expected to start in the second half of 2027. The company's CEO emphasized that tolerability is a major challenge in bipolar disorder, and RAP-219 could offer a new mechanism of action that patients can stay on. Analysts at Raymond James echoed that a better-tolerated treatment could become commercially relevant, especially for patients who struggle with sedation or movement symptoms on existing therapies.