Gossamer Bio is trading 7.27% up in after-hours trading at $11.51 after closing September 18, 2026, at $10.73, with no new company-specific announcement dated September 18 explaining the rebound.
- The latest investor-relations release was the September 16 appointment of Greg Ciongoli to the board.
- The recent 1-for-80 reverse split and sharp preceding volatility may be contributing to unusual trading activity.