SEC Form 3

FORM 3

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

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1. Name and Address of Reporting Person* Snow Jessica (Last) (First) (Middle) 60 BINNEY STREET (Street) CAMBRIDGE MA 02142 (City) (State) (Zip)	2. Date of Event Requiring Statement (Month/Day/Year) 04/01/2024	3. Issuer Name and Ticker or Trading Symbol 2seventy bio, Inc. [ TSVT ]
		4. Relationship of Reporting Person(s) to Issuer (Check all applicable) Director 10% Owner X Officer (give title below) Other (specify below) See Remarks	5. If Amendment, Date of Original Filed (Month/Day/Year)
			6. Individual or Joint/Group Filing (Check Applicable Line) X Form filed by One Reporting Person Form filed by More than One Reporting Person

Table I - Non-Derivative Securities Beneficially Owned
1. Title of Security (Instr. 4)	2. Amount of Securities Beneficially Owned (Instr. 4)	3. Ownership Form: Direct (D) or Indirect (I) (Instr. 5)	4. Nature of Indirect Beneficial Ownership (Instr. 5)
Common Stock	25,036	D

Table II - Derivative Securities Beneficially Owned (e.g., puts, calls, warrants, options, convertible securities)
1. Title of Derivative Security (Instr. 4)	2. Date Exercisable and Expiration Date (Month/Day/Year)		3. Title and Amount of Securities Underlying Derivative Security (Instr. 4)		4. Conversion or Exercise Price of Derivative Security	5. Ownership Form: Direct (D) or Indirect (I) (Instr. 5)	6. Nature of Indirect Beneficial Ownership (Instr. 5)
	Date Exercisable	Expiration Date	Title	Amount or Number of Shares
Stock Options (Right to buy)	(1)	08/01/2028	Common Stock	990	$241.47	D
Stock Options (Right to buy)	(1)	02/01/2029	Common Stock	425	$209.06	D
Stock Options (Right to buy)	(1)	03/02/2030	Common Stock	491	$114.67	D
Stock Options (Right to buy)	(2)	05/01/2030	Common Stock	343	$78.84	D
Stock Options (Right to buy)	(3)	07/01/2031	Common Stock	2,098	$50.35	D
Stock Options (Right to buy)	(4)	03/01/2032	Common Stock	9,500	$13.41	D
Stock Options (Right to buy)	(5)	02/01/2033	Common Stock	6,800	$13.2	D
Stock Options (Right to buy)	(5)	02/01/2033	Common Stock	6,400	$13.2	D
Stock Options (Right to buy)	(6)	10/02/2033	Common Stock	18,300	$3.97	D

Explanation of Responses:

1. This stock option is fully vested and currently exercisable.

2. This stock option vests over a four-year period at the rate of 25% on May 1, 2021, and then in 36 equal monthly installments thereafter.

3. This stock option vests over a four-year period at the rate of 25% on July 1, 2022, and then in 36 equal monthly installments thereafter.

4. This stock option vests over a four-year period at the rate of 25% on January 1, 2023, and then in 36 equal monthly installments thereafter.

5. This stock option vests over a four-year period at the rate of 25% on January 1, 2024, and then in 36 equal monthly installments thereafter.

6. This stock option vests over a three-year period at the rate of 25% on June 2, 2024, 25% on October 2, 2024, and then in 2 equal annual installments thereafter.

Remarks:

Title: Senior Vice President of Quality and Enabling Functions; Exhibit 24 Power of Attorney

	/s/ Iya Kessler, Attorney-in-Fact	04/03/2024
	** Signature of Reporting Person	Date
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 5 (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).
Note: File three copies of this Form, one of which must be manually signed. If space is insufficient, see Instruction 6 for procedure.
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