Rapport Therapeutics (NASDAQ:RAPP) shares advanced more than 50% in premarket trading on Tuesday after the biotechnology company reported that its investigational treatment RAP-219 met the primary and secondary endpoints in a Phase 2 clinical trial involving patients with bipolar I disorder experiencing acute manic episodes.
The study enrolled 253 adults and evaluated the efficacy and safety of RAP-219 over a three-week treatment period.
According to the company, RAP-219 achieved a statistically significant 3.1-point improvement compared with placebo on the Young Mania Rating Scale (YMRS) at week three. The scale is used to assess the severity of manic symptoms.
Patients receiving RAP-219 recorded an average reduction of 15.4 points from baseline in their YMRS total score, compared with a 12.3-point reduction among participants receiving placebo.
The company reported numerical improvements relative to placebo across all 11 components of the YMRS assessment at week three. Improvements in irritability, thought content, disruptive-aggressive behaviour and sexual interest reached nominal statistical significance.
RAP-219 also demonstrated a statistically significant 0.4-point improvement compared with placebo on the Clinical Global Impression–Bipolar Version mania severity scale at week three.
Regarding safety, Rapport reported that all treatment-emergent adverse events during the three-week study were classified as mild or moderate. No severe or serious adverse events were recorded.
The incidence of treatment-emergent adverse events was 51.6% among patients receiving RAP-219, compared with 52.8% in the placebo group.
Following the Phase 2 results, Rapport plans to meet with the US Food and Drug Administration (FDA) in the first quarter of 2027 to review the clinical findings and discuss the design of future registrational studies.
The company expects to initiate two Phase 3 clinical trials evaluating RAP-219 in acute bipolar mania during the second half of 2027.
The reported Phase 2 findings provide clinical efficacy and safety data for RAP-219, with further development dependent on subsequent clinical studies and regulatory discussions.