Sec Form 4 Filing - George Jean @ ACCELERON PHARMA INC - 2014-06-20

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 George Jean 2. Issuer Name and Ticker or Trading Symbol ACCELERON PHARMA INC [ XLRN] 5. Relationship of Reporting Person(s) to Issuer (Check all applicable) X __ Director _____ 10% Owner _____ Officer (give title below) _____ Other (specify below) (Last) (First) (Middle) C/O ADVANCED TECHNOLOGY VENTURE, 500 BOYLSTON STREET, SUITE 1380 3. Date of Earliest Transaction (MM/DD/YY) 06/20/2014 (Street) BOSTON, MA02116 4. If Amendment, Date Original Filed (MM/DD/YY) 6. Individual or Joint/Group Filing (Check Applicable Line) __ X __ Form filed by One Reporting Person _____ 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 06/20/2014 S( 1 ) 1,457( 2 ) D $ 35.02( 3 ) 1,937,574 I See footnotes( 4 )( 5 )( 6 ) Common Stock 06/23/2014 S( 1 ) 13,618( 7 ) D $ 35.27( 8 ) 1,923,956 I See footnotes( 4 )( 5 )( 9 ) Common Stock 06/24/2014 S( 1 ) 10,402( 10 ) D $ 35.03( 11 ) 1,913,554 I See footnotes( 4 )( 5 )( 12 )

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 Indire ct (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 George Jean C/O ADVANCED TECHNOLOGY VENTURE 500 BOYLSTON STREET, SUITE 1380 BOSTON, MA02116 X Signatures /s/ Jean George 06/24/2014 Signature of Reporting Person Date

Explanation of Responses:

( 1 )Series of transactions pursuant to Rule 10b5-1 Plans on behalf of each entity each of which was entered into on February 28, 2014 and amended on May 22, 2014. ( 2 )Represents 1,365 shares, 55 shares, 26 shares, 8 shares and 3 shares that were held directly by Advanced Technology Ventures VII, L.P. ("ATV VII"), Advanced Technology Ventures VII (B), L.P. ("ATV VII B"), Advanced Technology Ventures VII (C), L.P. ("ATV VII C"), ATV Entrepreneurs VII, L.P. ("ATV VII E") and ATV Alliance 2003, L.P. ("ATV 2003"), respectively. ( 3 )Represents weighted average sales price. The shares were sold at prices ranging from $35.00 to $35.07. The Reporting Person will provide upon request, to the SEC, the Issuer or any security holder of the Issuer, full information regarding the number of shares sold at each separate price. ( 4 )ATV Associates VII, L.L.C. ("ATV A VII") is the general partner of ATV VII, ATV VII B, ATV VII C and ATV VII E and exercises voting and dispositive authority over the shares held by ATV VII, ATV VII B, ATV VII C and ATV VII E. Jean George is a managing director of ATV A VII and exercises voting and dispositive decisions of ATV A VII collectively with each of four other managing directors. Ms. George disclaims beneficial ownership of these securities and this report shall not be deemed an admission that she is the beneficial owner of such securities for purposes of Section 16 or for any other purpose, except to the extent of her pecuniary interest therein. ( 5 )ATV Alliance Associates, L.L.C. ("ATV Alliance LLC") is the general partner of ATV 2003 and exercises voting and dispositive authority over the shares held by ATV 2003. Voting and dispositive decisions of ATV Alliance LLC are made by Ms. George. Ms. George disclaims beneficial ownership of these securities and this report shall not be deemed an admission that she is the beneficial owner of such securities for purposes of Section 16 or for any other purpose, except to the extent of her pecuniary interest therein. ( 6 )Represents 1,815,175 shares, 72,839 shares, 35,011 shares, 10,814 shares and 3,735 shares that are held directly by ATV VII, ATV VII B, ATV VII C, ATV VII E and ATV 2003, respectively. Ms. George disclaims beneficial ownership of these securities and this report shall not be deemed an admission that she is the beneficial owner of such securities for purposes of Section 16 or for any other purpose, except to the extent of her pecuniary interest therein. ( 7 )Represents 12,759 shares, 512 shares, 246 shares, 76 shares and 25 shares that were held directly by ATV VII, ATV VII B, ATV VII C, ATV VII E and ATV 2003, respectively. ( 8 )Represents weighted average sales price. The shares were sold at prices ranging from $35.00 to $35.90. The Reporting Person will provide upon request, to the SEC, the Issuer or any security holder of the Issuer, full information regarding the number of shares sold at each separate price. ( 9 )Represents 1,802,416 shares, 72,327 shares, 34,765 shares, 10,738 shares and 3,710 shares that are held directly by ATV VII, ATV VII B, ATV VII C, ATV VII E and ATV 2003, respectively. Ms. George disclaims beneficial ownership of these securities and this report shall not be deemed an admission that she is the beneficial owner of such securities for purposes of Section 16 or for any other purpose, except to the extent of her pecuniary interest therein. ( 10 )Represents 9,746 shares, 391 shares, 188 shares, 58 shares and 19 shares that were held directly by ATV VII, ATV VII B, ATV VII C, ATV VII E and ATV 2003, respectively. ( 11 )Represents weighted average sales price. The shares were sold at prices ranging from $35.00 to $35.25. The Reporting Person will provide upon request, to the SEC, the Issuer or any security holder of the Issuer, full information regarding the number of shares sold at each separate price. ( 12 )Represents 1,792,670 shares, 71,936 shares, 34,577 shares, 10,680 shares and 3,691 shares that are held directly by ATV VII, ATV VII B, ATV VII C, ATV VII E and ATV 2003, respectively. Ms. George disclaims beneficial ownership of these securities and this report shall not be deemed an admission that she is the beneficial owner of such securities for purposes of Section 16 or for any other purpose, except to the extent of her pecuniary interest therein.

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