Why Is Rapport Therapeutics Stock Trading Higher Today?

Rapport Therapeutics Inc. (NASDAQ:RAPP) stock is trading higher on Tuesday with a premarket session volume of 1.439 million versus the average volume of 351.078 thousand, according to Benzinga Pro data.

The company shared positive topline results from its Phase 2 clinical trial evaluating RAP-219 in adult patients suffering from acute bipolar mania.

The clinical-stage biotechnology firm confirmed that the trial achieved its primary endpoint, validating clinical proof-of-concept for the candidate’s novel TARPγ8-selective mechanism and paving the way for late-stage development.

"RAP-219 has the potential to break that cycle with the first new mechanism of action for bipolar mania in decades. Together with our positive Phase 2 focal epilepsy data, these results strengthen RAP-219’s profile across each indication we are pursuing and show it delivering on its potential as a pipeline-in-a-product with two indications that both represent multibillion-dollar market opportunities. We look forward to engaging with the FDA on Phase 3 in bipolar mania, alongside our ongoing Phase 3 epilepsy programs," said Abraham Ceesay, CEO of Rapport.

Statistically Significant Efficacy in Manic Symptoms

The study enrolled 253 adults with bipolar I disorder undergoing an acute manic episode.

Participants received either a once-daily 0.75 mg dose of RAP-219 or a placebo in an inpatient setting over three weeks.

Patients receiving RAP-219 demonstrated a statistically significant 3.1-point placebo-adjusted improvement on the Young Mania Rating Scale (YMRS) at Week 3 (p=0.045).

The treatment cohort achieved a 15.4-point mean reduction from baseline compared to 12.3 points in the placebo arm. Placebo-adjusted score improvements expanded each week progressively, starting at 0.9 points at Week 1 and reaching 2.2 points at Week 2.

All 11 individual YMRS assessment items favored RAP-219 over placebo at Week 3, with nominal statistical significance observed in irritability, thought content, disruptive-aggressive behavior, and sexual interest. RAP-219 also met its key secondary endpoint, showing significant gains on the Clinical Global Impression—Bipolar Version mania severity scale (p=0.024).

Favorable Tolerability Profile and Regulatory Path

RAP-219 demonstrated favorable tolerability during the study, showing no severe treatment-emergent adverse events or serious adverse events. Overall adverse event rates remained balanced, with 51.6% in the RAP-219 cohort versus 52.8% on placebo.

Notably, patients did not report common bipolar treatment complications such as akathisia, extrapyramidal symptoms, or orthostatic hypotension.

Rapport plans to hold an end-of-Phase 2 meeting with the U.S. Food and Drug Administration in the first quarter of 2027.

The company expects to initiate two Phase 3 trials in acute bipolar mania during the second half of 2027, backed by $436.1 million in cash equivalents and investments as of June 30, 2026, which funds operations into the second half of 2029.

RAPP Price Action: Rapport Therapeutics shares were up 36.02% at $38.90 during premarket trading on Tuesday, according to Benzinga Pro data.

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