Xenon Pharmaceuticals paused enrollment in trials evaluating azetukalner in major depressive disorder and bipolar disorder after neuropsychiatric adverse events emerged. The company said participants already enrolled will continue in randomized controlled psychiatry studies and associated open-label extension trials, while the voluntary pause is intended to address safety signals. The pause landed as the same drug continues to be reviewed by the FDA for focal onset seizures, where Xenon reported stronger efficacy and safety signals earlier. Management noted the events were “consistent” with azetukalner’s known mechanism and described them as mild to moderate, reversible, and short in duration. Investors appear to have repriced the depression program quickly, reflecting how a single adverse-event headline can swing valuation even when a company has parallel clinical and regulatory momentum in another indication.