Xenon Pharmaceuticals voluntarily paused enrollment in its major depressive disorder and bipolar disorder trials of azetukalner after reports of neuropsychiatric adverse events emerged in the studies. The company said the pause affects new patient recruitment, while participants already enrolled in the randomized trials and open-label extension studies will continue. The development also coincides with an FDA review of azetukalner for focal onset seizures, a program for which Xenon reported encouraging results that had helped drive investor optimism. Separately, the company has submitted an NDA for focal onset seizures, creating a dual storyline: regulatory momentum in epilepsy paired with clinical uncertainty in psychiatry. Xenon’s next steps will likely focus on characterizing the event patterns, reassessing risk–benefit assumptions across indications, and determining whether dosing modifications can mitigate the adverse events described.