Gossamer Bio is trading 5.3% down at $10.36 after-hours as investors reassess seralutinib after the PROSERA trial missed its prespecified statistical threshold. - The regular-session close was $10.94; the company submitted the seralutinib application on September 23. - The FDA has not accepted it for filing; a decision could come later this year, company materials say. - Major market indices rose on September 25, so broad-market weakness does not explain the decline.