Exhibit 99.1 Spyre Therapeutics Reports First Quarter 2025 Financial Results and Provides Corporate Update On track for mid-year initiations of planned Phase 2 studies in ulcerative colitis ("UC") and rheumatoid arthritis ("RA"), providing for 7+ proof-of-concept readouts in 2026 & 2027 Reported extended follow-up Phase 1 data for SPY001, supporting that the molecule is well tolerated, has a pharmacokinetic ("PK") profile enabling quarterly or biannual dosing, and provides complete target engagement at expe ...