X0306 4 2022-03-17 false 0001860782 2seventy bio, Inc. TSVT 0001578408 Leschly Nick 60 BINNEY STREET CAMBRIDGE MA 02142 true true false false President and CEO Common Stock 2022-03-17 4 A false 368857.00 12.20 A 556888.00 D Common Stock 15233.00 I Nick Leschly 2001 Trust Common Stock 41000.00 I Nick Leschly Irrevocable GST Trust of 2019 The shares of common stock were acquired by the Reporting Person pursuant to a share purchase agreement in a private placement offering of shares of the Issuer's common stock, which offering closed on March 17, 2022. The issuance of such shares by the Reporting Person was approved by the Issuer's board of directors in accordance with Rule 16(b)-3 of the Securities Exchange Act of 1934, as amended. /s/ Teresa Jurgensen, Attorney-in-Fact 2022-03-21