Gossamer Bio is trading 6.86% higher at $11.69 on September 28, 2026, with no clear company-specific announcement identified to explain the gain. - Its latest company news page lists an earlier convertible-notes tender update, not a September 28 catalyst. - The PROSERA trial missed its prespecified statistical threshold, associated with an after-hours decline on September 25; it does not explain this session’s rise. - The broader market is lower and does not appear to explain the gain.