Sec Form 4 Filing - MPM BioVentures IV QP LP @ Epizyme, Inc. - 2014-02-10

FORM 4 Check this box if no longer subject to Section 16. Form 4 or Form 5 obligations may continue. See Instruction 1(b).

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 STATEMENT OF CHANGES IN BENEFICIAL OWNERSHIP Filed pursuant to Section 16(a) of the Securities Exchange Act of 1934, Section 17(a) of the Public Utility Holding Company Act of 1935 or Section 30(h) of the Investment Company Act of 1940

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1. Name and Address of Reporting Person MPM BioVentures IV QP LP 2. Issuer Name and Ticker or Trading Symbol Epizyme, Inc. [ EPZM] 5. Relationship of Reporting Person(s) to Issuer (Check all applicable) _____ Director X __ 10% Owner _____ Officer (give title below) _____ Other (specify below) (Last) (First) (Middle) C/O MPM ASSET MANAGEMENT, 200 CLAREDON STREET, 54TH FLOOR 3. Date of Earliest Transaction (MM/DD/YY) 02/10/2014 (Street) BOSTON, MA02116 4. If Amendment, Date Original Filed (MM/DD/YY) 6. Individual or Joint/Group Filing (Check Applicable Line) _____ Form filed by One Reporting Person __ X __ Form filed by More than One Reporting Person (City) (State) (Zip)

Table I - Non-Derivative Securities Acquired, Disposed of, or Beneficially Owned 1.Title of Security (Instr. 3) 2. Transaction Date (MM/DD/YY) 2A. Deemed Execution Date, if any (MM/DD/YY) 3. Transaction Code (Instr. 8) 4. Securities Acquired (A) or Disposed of (D) (Instr. 3, 4 and 5) 5. Amount of Securities Beneficially Owned Following Reported Transaction(s) (Instr. 3 and 4) 6. Ownership Form: Direct (D) or Indirect (I) (Instr. 4) 7. Nature of Indirect Beneficial Ownership (Instr. 4) Code V Amount (A) or (D) Price Common Stock 02/10/2014 S 466,666 ( 1 ) D $ 29.25 2,413,819 I See footnote ( 2 )

Table II - Derivative Securities Acquired, Disposed of, or Beneficially Owned ( e.g. , puts, calls, warrants, options, convertible securities) 1. Title of Derivative Security (Instr. 3) 2. Conversion or Exercise Price of Derivative Security 3. Transaction Date (MM/DD/YY) 3A. Deemed Execution Date, if any (MM/DD/YY) 4. Transaction Code (Instr. 8) 5. Number of Derivative Securities Acquired (A) or Disposed of (D) (Instr. 3, 4, and 5) 6. Date Exercisable and Expiration Date (MM/DD/YY) 7. Title and Amount of Underlying Securities (Instr. 3 and 4) 8. Price of Derivative Security (Instr. 5) 9. Number of Derivative Securities Beneficially Owned Following Reported Transaction(s) (Instr. 4) 10. Ownership Form of Derivative Security: Direct (D) or Indirect (I) (Instr. 4) 11. Nature of Indirect Beneficial Ownership (Instr. 4) Code V (A) (D) Date Exercisable Expiration Date Title Amount or Number of Shares

Reporting Owners Reporting Owner Name / Address Relationships Director 10% Owner Officer Other MPM BioVentures IV QP LP C/O MPM ASSET MANAGEMENT 200 CLAREDON STREET, 54TH FLOOR BOSTON, MA02116 X Scopa James Paul C/O MPM ASSET MANAGEMENT 601 GATEWAY BLVD., SUITE 350 SOUTH SAN FRANCISCO, CA94080 X MPM Asset Management Investors BV4 LLC C/O MPM ASSET MANAGEMENT 200 CLARENDON STREET, 54TH FLOOR BOSTON, MA02116 X MPM BioVentures IV GmbH & Co. Beteiligungs KG C/O MPM ASSET MANAGEMENT 200 CLARENDON STREET, 54TH FLOOR BOSTON, MA02116 X MPM BioVentures IV GP LLC C/O MPM ASSET MANAGEMENT 200 CLARENDON STREET, 54TH FLOOR BOSTON, MA02116 X MPM BioVentures IV LLC C/O MPM ASSET MANAGEMENT 200 CLARENDON STREET, 54TH FLOOR BOSTON, MA02116 X MPM BioVentures IV Strategic Fund, L.P. C/O MPM ASSET MANAGEMENT 200 CLARENDON STREET, 54TH FLOOR BOSTON, MA02116 X Foley Todd C/O MPM ASSET MANAGEMENT 200 CLARENDON STREET, 54TH FLOOR BOSTON, MA02116 X KAILIAN VAUGHN M C/O MPM ASSET MANAGEMENT 200 CLARENDON STREET, 54TH FLOOR BOSTON, MA02116 X Signatures By Luke Evnin, member of MPM BioVentures IV LLC, the managing member of MPM BioVenturesIV GP LLC, the general partner of MPM BioVentures IV-QP, L.P. /s/ Luke Evnin 02/11/2014 Signature of Reporting Person Date /s/ James Scopa 02/11/2014 Signature of Reporting Person Date By Luke Evnin, member of MPM BioVentures IV LLC, the manager of MPM Asset Management Investors BV4 LLC /s/ Luke Evnin 02/11/2014 Signature of Reporting Person Date By Luke Evnin, member of MPM BioVentures IV LLC, the managing member of MPM BioVentures IV GP LLC, the managing limited partner of MPM BioVentures IV GmbH & Co. KG /s/ Luke Evnin 02/11/2014 Signature of Reporting Person Date By Luke Evnin, member of MPM BioVentures IV LLC, the managing member of MPM BioVentures IV GP LLC /s/ Luke Evnin 02/11/2014 Signature of Reporting Person Date By Luke Evnin, member of MPM BioVentures IV LLC /s/ Luke Evnin 02/11/2014 Signature of Reporting Person Date By Luke Evnin, member of MPM BioVentures IV LLC, the managing member of MPM BioVentures IV GP LLC, the general partner of MPM BioVentures IV Strategic Fund, L.P. /s/ Luke Evnin 02/11/2014 Signature of Reporting Person Date /s/ Todd Foley 02/11/2014 Signature of Reporting Person Date /s/ Vaughn Kailian 02/11/2014 Signature of Reporting Person Date

Explanation of Responses:

( 1 )The shares were sold as follows: 377,313 by MPM BioVentures IV-QP, L.P. ("BV IV QP"), 14,536 by MPM BioVentures IV GmbH & Co. Beteiligungs KG ("BV IV KG"), 10,729 by MPM Asset Management Investors BV4 LLC ("AM BV4") and 64,088 shares by MPM BioVentures IV Strategic Fund, L.P. ("BV IV SF"). MPM BioVentures IV GP LLC and MPM BioVentures IV LLC ("BV LLC") are the direct and indirect general partners of BV IV QP, BV IV KG and BV IV SF and BV LLC is the manager of AM BV4. Ansbert Gadicke, Luke Evnin, Vaughn M. Kailian,James Paul Scopa and Todd Foley are the members of BV LLC. ( 2 )The shares are held as follows: 1,951,645 by BV IV QP, 75,188 by BV IV KG, 55,495 by AM BV4 and 331,491 shares by BV IV SF. Each Reporting Person disclaims beneficial ownership of the securities except to the extent of his or its respective pecuniary interest therein.

Remarks: See Form 4 for Luke Evnin for additional members of this joint filing.

Reminder: Report on a separate line for each class of securities beneficially owned directly or indirectly.

* If the form is filed by more than one reporting person, see Instruction 4(b)(v).

** Intentional misstatements or omissions of facts constitute Federal Criminal Violations. See 18 U.S.C. 1001 and 15 U.S.C. 78ff(a).

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