Xenon Pharmaceuticals said it is voluntarily pausing enrollment in Phase 3 trials evaluating azetukalner (a KV7 potassium channel opener) in major depressive disorder and bipolar disorder after reports of neuropsychiatric adverse events. The company said patients already enrolled will continue through the remainder of the randomized studies and associated open-label extensions. The pause came as investors also tracked an FDA review for azetukalner in focal onset seizures, where Xenon has reported strong efficacy and safety across more than 1,500 patient-years. Xenon attributed the events to its known safety profile and mechanism, and said events were mostly mild to moderate, short in duration, and reversible, while exploring potential dosing modifications to mitigate them. Shares fell sharply following the announcement as the market recalibrated expectations for depression-related development. Xenon said it expects to produce data in early 2027, indicating the trial pause may delay timeline communication for that indication. The incident underscores how neuropsychiatric signals can force rapid operational changes even when a drug’s epilepsy profile remains intact, potentially affecting how regulators and payers interpret benefit-risk across indications.