X0306 4 2022-05-17 0 0001571498 Epizyme, Inc. EPZM 0001579300 BEVERIDGE, ROY A C/O EPIZYME, INC., 400 TECHNOLOGY SQUARE, 4TH FLOOR CAMBRIDGE MA 02139 1 0 0 0 Common Stock, par value $0.0001 2022-05-17 4 A 0 8994 0.00 A 37109 D Stock Option (Right to Buy) 0.56 2022-05-17 4 A 0 41006 0.00 A 2032-05-16 Common Stock 41006 41006 D Consists of shares of Common Stock issuable under 8,994 restricted stock units ("RSUs") granted on May 17, 2022, which RSUs are scheduled to vest with respect to all shares on the first anniversary of the grant date or, if earlier, immediately prior to the first annual meeting of stockholders occurring after the grant date, subject to continued service as a director. Each RSU represents the right to receive one share of Common Stock upon vesting. In the event of a change in control of the Issuer, the RSUs will vest in full. This option was granted on May 17, 2022 and is scheduled to vest with respect to all shares on the first anniversary of the grant date or, if earlier, immediately prior to the first annual meeting of stockholders occurring after the grant date, subject to continued service as a director. In the event of a change in control of the Issuer, the option will become exercisable in full. /s/John Weidenbruch, attorney-in-fact 2022-05-19