Xenon Pharmaceuticals said adverse events in trials of azetukalner to treat depression and bipolar disorder led it to pause enrollment voluntarily. Shares tumbled 26%, to $42.35, after Thursday's bell.

Ultragenyx Pharmaceutical's Fayuvi drug received Food and Drug Administration approval to treat children with Sanfilippo syndrome type A. The stock closed up 13%, at $14.50, and gained another 1.7% after the bell.

BRT Apartments said its board approved a $10 million replenishment for its stock-buyback program. Shares rose 2.9%, to $14.22, after-hours.