Exhibit 99.1 Gossamer Bio Announces First Quarter 2025 Financial Results and Provides Business Update, Including Closure of New Patient Screening in Phase 3 PROSERA Study - Enrollment Completion for Ongoing Registrational PROSERA Phase 3 Study in PAH Expected in Early June; New Patient Screening Closed - - Topline Results Announcement from PROSERA Phase 3 Expected in February 2026 - - To Date, Blinded Baseline Characteristics Align with Intended Study Population - - First Site Activations for Planned Regist ...