First Amendment to the Companion Diagnostics Agreement dated October 23, 2013 between the Registrant and Eisai Co. Ltd. on the one side and Roche Molecular Systems, Inc. on the other side

1.

The definition of Assay in Section 2.5 of the Agreement is hereby amended and restated in its entirety to read as follows:

2.

The current Project Plan under the Agreement is hereby replaced in its entirety with the amended and restated Project Plan set forth in Attachment 1 to this Amendment.

3.

In consideration for the additional activities required from RMS for the changes to the Project Plan, as updated in Attachment 1, the Pharmaceutical Partners agree to compensate RMS Five Hundred Thousand Dollars ($500,000.00) in addition to the payments previously set forth in the Payment Plan. This additional compensation shall become payable upon the execution of this Amendment and shall be paid following receipt of an invoice therefor from RMS in accordance with Section 7.2 of the Agreement.

a.

The second to last sentence in Section 15.7(b) shall be amended as follows:

b.

The last sentence in Exhibit B, Payment Plan, shall be replaced in its entirety with the following:

4.

Exhibits B and E of the Agreement are hereby further amended by replacing each reference to [**] therein with [**].

5.

Exhibit C of the Agreement is hereby replaced in its entirety with the amended and restated Exhibit C set forth in Attachment 2 to this Amendment.

6.

The Parties acknowledge that additional licenses or other rights to access and/or use Third Party technology or intellectual property rights may be necessary for the development, manufacture, use or commercialization of the RMS Product, due to the development of the Assay to include detection of the Additional Mutations, and that such Third Party technology or intellectual property rights may or may not be also needed for Pharmaceutical Partners Product. Section 5.12(a) of the Agreement is hereby amended such that Pharmaceutical Partners shall be solely responsible for obtaining and maintaining any Third Party intellectual property rights necessary for the development, manufacture, use or commercialization of the RMS Product, to the extent such Third Party intellectual property right would not have been needed for the RMS Product but for the inclusion of the Additional Mutations. Pharmaceutical Partners agree to provide reasonable opportunity for RMS to review and comment on any proposed terms of the Third Party agreement pursuant to which Pharmaceutical Partners obtain such rights that, in Pharmaceutical Partners’ reasonable determination, would impose additional obligations or restrictions on RMS (beyond what is contemplated under the Agreement (as amended) for similar intellectual property rights) with respect to the RMS Product, including a final right of approval over any terms of such agreement that would impose such additional obligations or restrictions on RMS prior to execution, such approval not to be unreasonably withheld, delayed or conditioned. In addition, Pharmaceutical Partners agree to provide a draft of any such Third Party agreement to RMS at least [**] business days prior to execution and to reasonably consider any objections as to

obligations or restrictions that such Third Party agreement would impose on RMS with respect to the RMS Product that RMS may timely raise. Any disputes over compliance with this paragraph shall be first resolved by the Senior Officers of the Parties pursuant to Section 4.3, and if still unresolved, then pursuant to the arbitration provisions set forth in Section 16. Once such Third Party intellectual property agreement is finalized and executed, Pharmaceutical Partners agree to be solely responsible for any and all costs thereof to the extent relating to Third Party intellectual property rights that would not have been needed for the RMS Product but for the inclusion of the Additional Mutations.

7.

The provision on “Disclosure of Funding Pursuant to State Laws” in Section 10.6 of the Agreement is hereby amended such that the heading is restated in its entirety to read “Disclosure of Funding Pursuant to State/Federal Laws” and that two additional sentences shall be included at the end of such section as follows:

8.

This Amendment is effective and shall become part of the Agreement as of the Amendment Effective Date.

9.

Except as provided herein, all other terms and conditions of the Agreement remain unchanged and in full force and effect.

10.

This Amendment may be signed in any number of counterparts (facsimile and electronic transmission included), each of which shall be deemed an original, but all of which shall constitute one and the same instrument. After facsimile or electronic transmission, the Parties agree to execute and exchange documents with original signature.

ROCHE MOLECULAR SYSTEMS, INC.

EPIZYME, INC.

By:

/s/ Paul Brown

By:

/s/ Jason Rhodes

Name:

Paul A. Brown

Name:

Jason Rhodes

Title:

President and CEO

Title:

President and CFO

Date:

2013.10.13

Date:

10-4-13

EISAI CO., LTD.

By:

/s/ Kenichi Nomoto

Name:

Kenichi Nomoto

Title:

President, Oncology PCU

Date:

10-23-2013