Xenon shares tumble up to 30% after pausing depression trial over neuropsychiatric events

Xenon Pharmaceuticals announced it is pausing enrollment in its depression trial for the drug azetukalner after neuropsychiatric adverse events emerged that were not observed in earlier testing.

Azetukalner is currently under FDA review for a type of seizure disorder, and the company said the new safety signals were consistent with the drug's known profile.

The news sent the stock down as much as 30% on the day, eroding a valuation that had topped $5 billion and prompting analysts to question the drug's prospects in depression, though some note the FDA may view the epilepsy indication differently.

Xenon will continue the trial with participants already enrolled, with read‑out data expected in early 2027.