Sec Form 4 Filing - GILLIS STEVEN @ bluebird bio, Inc. - 2014-10-09

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 GILLIS STEVEN 2. Issuer Name and Ticker or Trading Symbol bluebird bio, Inc. [ BLUE] 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 ARCH VENTURE PARTNERS, 8725 WEST HIGGINS ROAD, SUITE 290 3. Date of Earliest Transaction (MM/DD/YY) 10/09/2014 (Street) CHICAGO, IL60631 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 10/09/2014 S 115,000 D $ 35.2512 ( 1 ) 1,041,111 I By ARCH Venture Fund VII, L.P. ( 2 ) ( 3 )

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 GILLIS STEVEN C/O ARCH VENTURE PARTNERS 8725 WEST HIGGINS ROAD, SUITE 290 CHICAGO, IL60631 X Signatures /s/ Steven Gillis 10/10/2014 Signature of Reporting Person Date

Explanation of Responses:

( 1 )The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $35.25 to $35.47, inclusive. The reporting person undertakes to provide to BLUE, any security holder of BLUE, or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of shares sold at each seperate price within the range set forth in footnote (1) to this Form 4. ( 2 )These shares are owned directly by ARCH Venture Fund VII, L.P. ("ARCH Fund VII"). The sole general partner of ARCH Fund VII is ARCH Venture Partners VII, L.P. ("ARCH Partners VII"). The sole general partner of ARCH Partners VII is ARCH Venture Partners VII, LLC ("ARCH VII LLC"). The Managing Directors of ARCH VII LLC, Robert T. Nelsen, Keith Crandell and Clinton Bybee, are deemed to have voting and dispositive power over the shares and may be deemed to beneficially own Fund shares held by ARCH Fund VII. Each Managing Director disclaims beneficial ownership of these securities, except to the extent of his pecuniary interest therein, and this report shall not be deemed an admission that such Managing Director is the beneficial owner of such securities for Section 16 or any other purpose. ( 3 )Steven Gillis owns an interest in ARCH Partners VII but does not have voting or investment control over the shares held by ARCH Fund VII and disclaims beneficial ownership of such shares, except to the extent of any pecuniary interest therein, and this report shall not be deemed an admission that Steven Gillis is the beneficial owner of such securities for Section 16 or any other purpose.

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).

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