X0306 4 2020-11-23 false 0001395937 Syndax Pharmaceuticals Inc SNDX 0001594274 Ordentlich Peter C/O SYNDAX PHARMACEUTICALS, INC. 35 GATEHOUSE DRIVE, BUILDING D, FLOOR 3 WALTHAM MA 02451 false true false false Chief Scientific Officer Common Stock 2020-11-23 4 M false 24288.00 3.08 A 24288.00 D Common Stock 2020-11-23 4 M false 5684.00 3.08 A 29972.00 D Common Stock 2020-11-23 4 S false 5684.00 23.3291 D 24288.00 D Common Stock 2020-11-23 4 S false 7954.00 23.5849 D 16334.00 D Common Stock 2020-11-23 4 S false 16334.00 22.8924 D 0.00 D Stock Option (Right to Buy) 3.08 2020-11-23 4 M false 24288.00 0.00 D 2023-05-09 Common Stock 24288.00 0.00 D Stock Option (Right to Buy) 3.08 2020-11-23 4 M false 5684.00 0.00 D 2023-05-09 Common Stock 5684.00 0.00 D The sales prices ranged from $22.94 to $23.73. The sales prices ranged from $23.35 to $23.94. The sales prices ranged from $22.34 to $23.32. This option is fully vested. /s/ Michael A. Metzger, Attorney-in-Fact 2020-11-25