X0508 4 2025-05-13 true 0001860782 2seventy bio, Inc. TSVT 0001578408 Leschly Nick 60 BINNEY STREET CAMBRIDGE MA 02142 true false false false false Common Stock 2025-05-13 4 D false 335964.00 D 897642.00 D Common Stock 2025-05-13 4 U false 897642.00 D 0.00 D Common Stock 2025-05-13 4 U false 15233.00 D 0.00 I Nick Leschly 2001 Trust Common Stock 2025-05-13 4 U false 41000.00 D 0.00 I Nick Leschly Irrevocable GST Trust of 2019 Stock Options (Right to buy) 3.97 2025-05-13 4 D false 469000.00 D Common Stock 469000.00 0.00 D This Form 4 reports securities disposed pursuant to the Agreement and Plan of Merger (the "Merger Agreement"), dated as of March 10, 2025, by and among the Issuer, Bristol-Myers Squibb Company ("Parent"), and Daybreak Merger Sub Inc., a wholly owned subsidiary of Parent ("Merger Sub"). Pursuant to the Merger Agreement, Merger Sub completed a cash tender offer to acquire all of the issued and outstanding shares of common stock of the Issuer, par value $0.0001 per share (the "Company Common Stock"), for a price per share of $5.00 (the "Merger Consideration"), without interest and subject to any withholding of taxes required by applicable law. Effective as of May 13, 2025, Merger Sub merged with and into the Issuer, with the Issuer continuing as the surviving corporation and as a wholly owned subsidiary of Parent (the "Merger"). Pursuant to the terms of the Merger Agreement, each share of Company Common Stock subject to issuance pursuant to outstanding restricted stock units (each, a "Company RSU Award"), whether vested or unvested that was outstanding immediately prior to the effective time of the Merger (the "Effective Time"), became fully vested, and was cancelled and automatically converted into the right to receive, for each share of Company Common Stock underlying such Company RSU Award, an amount (without interest and subject to deduction for any required withholding under applicable law relating to tax) in cash equal to the Merger Consideration. Pursuant to the terms of the Merger Agreement, at the Effective Time, each share of Company Common Stock was tendered in exchange for the Merger Consideration, without interest and subject to any withholding of taxes required by applicable law. Pursuant to the terms of the Merger Agreement, each outstanding option to purchase shares of Company Common Stock ("Company Option"), whether vested or unvested, that was outstanding immediately prior to the Effective Time and had a per share exercise price that was less than the Merger Consideration became fully vested, was cancelled and automatically converted into the right to receive for each share of Company Common Stock underlying such Company Option, an amount (without interest and subject to deduction for any required withholding under applicable law) in cash equal to the excess of the Merger Consideration over the per share exercise price of such Company Option. Each Company Option, whether vested or unvested, that was outstanding and unexercised immediately prior to the Effective Time and had a per share exercise price that is equal to or greater than the Merger Consideration was automatically cancelled for no consideration. /s/ William Baird, Attorney-in-Fact 2025-05-15