X0306 4 2014-06-23 0 0001571498 Epizyme, Inc. EPZM 0001577021 Copeland Robert A C/O EPIZYME, INC. 400 TECHNOLOGY SQUARE CAMBRIDGE MA 02139 0 1 0 0 EVP and CSO Common Stock, par value $0.0001 per share 2014-06-23 4 M 0 6550 0.51 A 11855 D Common Stock, par value $0.0001 per share 2014-06-23 4 M 0 13450 0.60 A 25305 D Common Stock, par value $0.0001 per share 2014-06-23 4 S 0 14816 28.2598 D 10489 D Common Stock, par value $0.0001 per share 2014-06-23 4 S 0 5184 28.8802 D 5305 D Common Stock, par value $0.0001 per share 5525 I By Wife Stock Option (Right to Buy) 0.51 2014-06-23 4 M 0 6550 0.00 D 2020-03-17 Common Stock 6550 1250 D Stock Option (Right to Buy) 0.60 2014-06-23 4 M 0 13450 0.00 D 2021-03-10 Common Stock 13450 96314 D The exercise and sale 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 $27.65 per share to $28.59 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. The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $28.70 per share to $29.115 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 March 18, 2010 with respect to 60,000 shares of Common Stock, with 25% vesting on March 18, 2011 and the remaining 75% vesting in 36 substantially equal monthly installments thereafter. This option was granted on March 11, 2011 with respect to 109,764 shares of Common Stock, with 25% vesting on March 11, 2012 and the remaining 75% vesting in 36 substantially equal monthly installments thereafter. /s/ Nicole Heifner, attorney-in-fact 2014-06-25