Exhibit 99.1 PRESS RELEASE Prothena Reports First Quarter 2025 Financial Results and Business Highlights DUBLIN, Ireland, May 8, 2025 -- Prothena Corporation plc (NASDAQ:PRTA), a late-stage clinical biotechnology company with a robust pipeline of investigational therapeutics built on protein dysregulation expertise, today reported financial results for the first quarter of 2025 and provided business highlights. "We continue to meaningfully advance our wholly-owned and partnered programs across our protein d ...