Exhibit 99.1 Syndax Pharmaceuticals Reports Fourth Quarter and Full Year 2023 Financial Results and Provides Clinical and Business Update – BLA filing for axatilimab in chronic GVHD granted Priority Review; PDUFA action date set for August 28, 2024 – – NDA for revumenib in R/R KMT2Ar acute leukemia submitted under FDA’s RTOR program; PDUFA date assignment expected in 1Q24 – – Enrollment in AUGMENT-101 mNPM1 patient cohort expected to complete in late 1Q/early 2Q; topline data in 4Q24 – – Initiated revumenib ...