X0206 3 2016-03-02 0 0001395937 Syndax Pharmaceuticals Inc SNDX 0001601351 Sledge George W. Jr. C/O SYNDAX PHARMACEUTICALS, INC. 400 TOTTEN POND ROAD, SUITE 110 WALTHAM MA 02451 1 0 0 0 Stock Option (right to buy) 6.32 2024-09-15 Common Stock 9321 D Stock Option (right to buy) 6.35 2024-12-18 Common Stock 845 D Stock Option (right to buy) 7.20 2025-08-18 Common Stock 16800 D Twenty-five percent (25%) of the total number of shares underlying the option vested on September 15, 2014, and one forty-eighth (1/48th) of the total number of shares underlying the option vest monthly thereafter on the last day of each month, subject to the reporting person's continuous service on the relevant vesting dates. Twenty-five percent (25%) of the total number of shares underlying the option vested on December 18, 2014, and one forty-eighth (1/48th) of the total number of shares underlying the option vest monthly thereafter on the last day of each month, subject to the reporting person's continuous service on the relevant vesting dates. Twenty-five percent (25%) of the total number of shares underlying the option vested on August 18, 2015, and one forty-eighth (1/48th) of the total number of shares underlying the option vest monthly thereafter on the last day of each month, subject to the reporting person's continuous service on the relevant vesting dates. /s/ Michael A. Metzger, Attorney-in-Fact 2016-03-02