X0306 4 2021-02-04 0 0001571498 Epizyme, Inc. EPZM 0001620152 Bazemore Robert B C/O EPIZYME, INC. 400 TECHNOLOGY SQUARE CAMBRIDGE MA 02139 1 1 0 0 President & CEO Common Stock, par value $0.0001 2021-02-04 4 S 0 3890 11.21 D 331977 D Represents shares automatically sold by the reporting person to satisfy tax withholding obligations in connection with the vesting of the restricted stock units granted under the issuer's 2013 Stock Incentive Plan on February 3, 2020. The automatic sale of the reporting person's shares is provided for in a restricted stock unit agreement constituting a "binding contract" consistent with the affirmative defense to liability under Rule 10b5-1 and the sale does not represent a discretionary trade by the reporting person. /s/ John Weidenbruch, attorney-in-fact 2021-02-05