X0306 4 2020-06-18 0 0001571498 Epizyme, Inc. EPZM 0001673802 Ros Matthew C/O EPIZYME, INC., 400 TECHNOLOGY SQUARE CAMBRIDGE MA 02139 0 1 0 0 See Remarks Common Stock, par value $0.0001 2020-06-18 4 M 0 41063 9.12 A 92861 D Common Stock, par value $0.0001 2020-06-18 4 S 0 41063 20.50 D 51798 D Common Stock, par value $0.0001 2020-06-18 4 M 0 2289 12.45 A 54087 D Common Stock, par value $0.0001 2020-06-18 4 S 0 2289 22.00 D 51798 D Common Stock, par value $0.0001 2020-06-18 4 M 0 68651 9.58 A 120449 D Common Stock, par value $0.0001 2020-06-18 4 S 0 68651 21.65 D 51798 D Stock Option (Right to Buy) 9.12 2020-06-18 4 M 0 41063 0.00 D 2029-01-23 Common Stock 41063 110557 D Stock Option (Right to Buy) 12.45 2020-06-18 4 M 0 2289 0.00 D 2027-02-07 Common Stock 2289 107577 D Stock Option (Right to Buy) 9.58 2020-06-18 4 M 0 68651 0.00 D 2026-05-15 Common Stock 68651 104787 D The exercises and sales reported on this Form 4 were effected pursuant to a Rule 10b5-1 trading plan adopted by the Reporting Person. The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $21.50 per share to $22.00 per share, inclusive. The Reporting Person undertakes to provide the Issuer, any security holder of the Issuer or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of shares sold at each separate price within the range set forth in this footnote. This option was granted on January 24, 2019 pursuant to the Company's 2013 Stock Incentive Plan with respect to 151,620 shares of Common Stock, with 25% vesting on January 24, 2020 and the remaining 75% vesting in 36 substantially equal monthly installments thereafter. This option was granted on February 8, 2017 pursuant to the Company's 2013 Stock Incentive Plan with respect to 109,866 shares of Common Stock, with 25% vesting on February 8, 2018 and the remaining 75% vesting in 36 substantially equal monthly installments thereafter. This option is fully vested. Chief Strategy & Business Officer /s/ John Weidenbruch, attorney-in-fact 2020-06-22