Sec Form 4 Filing - Tita-Reid Najoh @ bluebird bio, Inc. - 2021-11-11

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 Tita-Reid Najoh 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) 60 BINNEY STREET 3. Date of Earliest Transaction (MM/DD/YY) 11/11/2021 (Street) CAMBRIDGE, MA02142 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( 1 )( 2 )( 3 ) 11/11/2021 J 9,361 A $ 0 9,361 D

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 Stock Option (right to buy) $ 9.46( 4 ) 11/11/2021 J 15,057( 4 ) ( 4 ) 09/29/2031 Common Stock 15,057 $ 0 15,057 D

Reporting Owners Reporting Owner Name / Address Relationships Director 10% Owner Officer Other Tita-Reid Najoh 60 BINNEY STREET CAMBRIDGE, MA02142 X Signatures /s/ Helen Fu, Attorney-in-Fact 11/16/2021 Signature of Reporting Person Date

Explanation of Responses:

( 1 )Represents restricted stock units awarded to the reporting person prior to the separation (the "Separation") of 2seventy bio, Inc. ("2seventy") from bluebird bio, Inc. ("bluebird"). In connection with the Separation, the restricted stock units underlying this award were adjusted pursuant to the the Employee Matters Agreement by and between 2seventy and bluebird (the "EMA") to preserve the value associated with the original restricted stock unit award (see footnotes 2 and 3). This restricted stock unit award was originally granted on September 29, 2021 and vests ratably over three years in annual installments commencing on September 29, 2021. ( 2 )bluebird equity awards granted prior to January 1, 2021 were converted into equity awards of both bluebird and 2seventy. The number of shares underlying the converted bluebird equity awards was determined by multiplying the number of shares underlying the existing bluebird equity award by a fraction, the numerator of which is the volume-weighted average trading price of bluebird common stock (trading "regular way") on the five trading days immediately prior to the distribution date (the "bluebird Pre-Distribution VWAP") and the denominator of which is the sum of (1) the volume-weighted average trading price of 2seventy common stock (trading "regular way") on the five trading days immediately following the distribution date multiplied by the distribution ratio and (2) the volume-weighted average trading price of bluebird bio common stock (trading "regular way") on the five trading days immediately following the distribution date (the "bluebird Post-Distribution VWAP"). ( 3 )bluebird equity awards granted on or after January 1, 2021, such equity awards continued as bluebird equity awards, subject to adjustment. The adjusted number of shares of bluebird common stock underlying such equity awards is equal to the number of shares of bluebird common stock subject to the equity award immediately prior to the distribution multiplied by a fraction, the numerator of which is the bluebird Pre-Distribution VWAP and the denominator of which is the bluebird Post-Distribution VWAP. ( 4 )Represents options to purchase bluebird common stock awarded to the reporting person prior to the Separation. In connection with the Separation, the shares of common stock underlying this award were adjusted pursuant to the EMA to preserve the value associated with the original award (see footnotes 2 and 3). This option was originally granted on September 29, 2021 and shall vest over three years in annual installments commencing on September 29, 2021. The exercise price of the option has been adjusted based on the conversion ratio described in footnotes 2 and 3.

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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