Edgar Filing: bluebird bio, Inc.

Ownership Submission

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 OF SECURITIES

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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3235-0287

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(Print or Type Responses)

1. Name and Address of Reporting Person ^*

THIRD ROCK VENTURES LP

2. Issuer Name and Ticker or Trading Symbol
bluebird bio, Inc. [BLUE]

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)

29 NEWBURY STREET

3. Date of Earliest Transaction (Month/Day/Year)
06/24/2013

(Street)

BOSTON, MA 02116

4. If Amendment, Date Original Filed(Month/Day/Year)

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 (Month/Day/Year)	2A. Deemed Execution Date, if any (Month/Day/Year)	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	06/24/2013		C		4,734,248 ⁽¹⁾	A	$ 0	4,734,248	D ⁽²⁾

Reminder: Report on a separate line for each class of securities beneficially owned directly or indirectly.
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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 (Month/Day/Year)

3A. Deemed Execution Date, if any (Month/Day/Year)

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
(Month/Day/Year)

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

(A)

(D)

Date Exercisable

Expiration Date

Title

Amount or Number of Shares

Series B Convertible Preferred Stock

⁽³⁾

06/24/2013

64,377,682

⁽³⁾

Common Stock

3,394,194

⁽³⁾

D ⁽²⁾

Series C Convertible Preferred Stock

⁽³⁾

06/24/2013

14,379,294

⁽³⁾

Common Stock

758,121

⁽³⁾

D ⁽²⁾

Series D Convertible Preferred Stock

⁽³⁾

06/24/2013

11,037,527

⁽³⁾

Common Stock

581,933

⁽³⁾

D ⁽²⁾

Reporting Owners

Reporting Owner Name / Address	Relationships
Reporting Owner Name / Address	Director	10% Owner	Officer	Other
THIRD ROCK VENTURES LP 29 NEWBURY STREET BOSTON, MA 02116		X
TRV GP, LLC 29 NEWBURY STREET BOSTON, MA 02116		X
Third Rock Ventures GP, L.P. 29 NEWBURY STREET BOSTON, MA 02116		X

Signatures

By: Third Rock Ventures GP, L.P., its general partner By: TRV GP, LLC, its general partner By: /s/ Kevin Gillis Kevin Gillis, Manager		06/26/2013
^**Signature of Reporting Person		Date
/s/ Kevin Gillis, Manager		06/24/2013
^**Signature of Reporting Person		Date
By: TRV GP, LLC, its general partner By: /s/ Kevin Gillis, Manager		06/24/2013
^**Signature of Reporting Person		Date

Explanation of Responses:

*	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).
(1)	Represents the total number of shares received upon conversion of shares of the Issuer's Series B Convertible Preferred Stock (the "Series B Shares"), Series C Convertible Preferred Stock (the "Series C Shares") and Series D Convertible Preferred Stock (the "Series D Shares" and together with the Series B Shares and the Series C Shares, collectively, the "Preferred Shares").
(2)	The general partner of Third Rock Ventures, L.P. is Third Rock Ventures GP, LP ("TRV GP"). The general partner of TRV GP is TRV GP, LLC. TRV GP and TRV GP, LLC disclaim beneficial ownership of such shares, except to the extent of any pecuniary interest therein.
(3)	Effective upon the closing of the Issuer's initial public offering of its Common Stock, each Preferred Share automatically converted at a ratio of 18.967-to-one into the number of shares of Common Stock shown in column 7. The Preferred Shares had no expiration date.

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