Why Xenon Pharmaceuticals (XENE) Is Down 32.2% After Pausing Psychiatry Trials Despite Positive NDA Data

September 20, 2026 - 02:49

Xenon Pharmaceuticals saw its stock drop 32.2 percent after the company paused new enrollment in its Phase 3 trials for major depressive disorder and bipolar depression. The decision came on the same day the company submitted a New Drug Application to the US Food and Drug Administration for azetukalner in focal seizures.

The seizure application is backed by two randomized, double-blind, placebo-controlled trials. Those studies showed statistically significant reductions in seizure frequency and a safety profile that was generally consistent across more than 1,500 patient-years of exposure.

The psychiatry trials were placed on hold after neuropsychiatric side effects appeared in participants. The company said the pause affects only new enrollment and that existing participants will continue to be monitored. Xenon has not announced a timeline for when the depression studies might resume.

The sharp stock decline reflects investor concern that the psychiatry program, once seen as a major growth driver, now faces delays and added uncertainty. The focal seizure submission remains on track while the company reviews the safety data from the mood disorder studies.