Epizyme, Inc. Added to Russell 2000® Index

Epizyme, Inc.,

a clinical stage biopharmaceutical company creating innovative personalized therapeutics for patients with genetically defined cancers, announced today that the Company has been added to the Russell 2000®, Russell 3000® and Russell Global® Indexes as part of Russell Investments' second-quarter IPO additions that took place after market close on June 28, 2013. The Russell 2000® Index measures the performance of the small-cap segment of the U.S. equity market and is a subset of the Russell 3000®, representing approximately 10 percent of the total market capitalization of that index. Membership in the Russell 2000® Index includes automatic inclusion in the appropriate growth and style indexes. Russell Investments determines membership for each index based on objective market capitalization rankings and style attributes. More than $3.9 trillion in assets are currently benchmarked to the Russell family of indexes.