X0306 4 2020-06-26 0 0001571498 Epizyme, Inc. EPZM 0001219871 MOTT DAVID M YELLOWSTONE CLUB 405 ANDESITE RIDGE ROAD BIG SKY MT 59716-1000 1 0 0 0 Common Stock, par value $0.0001 2020-06-26 4 P 0 62019 16.03 A 82601 D Common Stock, par value $0.0001 106959 I See Footnote The price reported in Column 4 is a weighted average price. These shares were purchased in multiple transactions at prices ranging from $15.87 per share to $16.25 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 purchased at each separate price within the range set forth in this footnote. The shares are directly held by David Mott Declaration of Trust dated May 31, 2001 as amended (the "Mott Trust"). The Reporting Person disclaims beneficial ownership within the meaning of Section 16 of the Securities Exchange Act of 1934, as amended, or otherwise of such portion of the Mott Trust shares in which the Reporting Person has no pecuniary interest. /s/ John Weidenbruch, attorney-in-fact 2020-06-26