X0202 SCHEDULE 13G 0002018299 XXXXXXXX LIVE Common Stock, $0.0001 par value per share 06/30/2026 0001661998 Q32 Bio Inc. 746964105 830 Winter Street Waltham MA 02451 Rule 13d-1(b) Boxer Capital Management, LLC DE 0.00 3149310.00 0.00 3149310.00 3149310.00 N 13.30 IA Boxer Holdings, LP DE 0.00 3149310.00 0.00 3149310.00 3149310.00 N 13.30 HC PN Boxer Holdings GP, LLC DE 0.00 3149310.00 0.00 3149310.00 3149310.00 N 13.30 HC Aaron Davis X1 0.00 3149310.00 0.00 3149310.00 3149310.00 N 13.30 HC IN Q32 Bio Inc. 830 Winter Street, Waltham, MA 02451 This statement is being jointly filed by (collectively, the "Reporting Persons"): Boxer Capital Management, LLC ("Boxer Capital") Boxer Holdings, LP Boxer Holdings GP, LLC Aaron Davis The business address of each Reporting Person is: 12860 El Camino Real, Suite 300, San Diego, CA 92130 Boxer Capital Management, LLC is a Delaware LLC. Boxer Holdings, LP is a Delaware LP. Boxer Holdings GP, LLC is a Delaware LLC. Aaron Davis is a citizen of the United States. N IA HC Row 9 of each Reporting Person's cover page to this Schedule 13G sets forth the aggregate number of shares of securities of the Issuer beneficially owned by such Reporting Person as of June 30, 2026 and is incorporated by reference. Row 11 of each Reporting Person's cover page to this Schedule 13G sets forth the percentages of securities of the Issuer beneficially owned by such Reporting Person as of June 30, 2026 and is incorporated by reference. Such percentage is based upon 23,681,415 shares of the Issuer's Common Stock outstanding, which is comprised of 16,956,415 shares out as of May 1, 2026, as reported in the Issuer's Quarterly Report on Form 10-Q filed with the Securities and Exchange Commission on May 5, 2026 plus 6,725,000 shares of common stock issued in the private placement of equity securities by the Issuer that closed on May 28, 2026. Row 5 of each Reporting Person's cover page to this Schedule 13G sets forth the sole power to vote or to direct the vote of securities of the Issuer beneficially owned by such Reporting Person as of June 30, 2026 and is incorporated by reference. Row 6 of each Reporting Person's cover page to this Schedule 13G sets forth the sole power to vote or to direct the vote of securities of the Issuer beneficially owned by such Reporting Person as of June 30, 2026 and is incorporated by reference. Row 7 of each Reporting Person's cover page to this Schedule 13G sets forth the sole power to vote or to direct the vote of securities of the Issuer beneficially owned by such Reporting Person as of June 30, 2026 and is incorporated by reference. Row 8 of each Reporting Person's cover page to this Schedule 13G sets forth the sole power to vote or to direct the vote of securities of the Issuer beneficially owned by such Reporting Person as of June 30, 2026 and is incorporated by reference. Y Y Y Y Y N By signing below I certify that, to the best of my knowledge and belief, the securities referred to above were acquired and are held in the ordinary course of business and were not acquired and are not held for the purpose of or with the effect of changing or influencing the control of the issuer of the securities and were not acquired and are not held in connection with or as a participant in any transaction having that purpose or effect, other than activities solely in connection with a nomination under § 240.14a-11. Boxer Capital Management, LLC /s/ Aaron Davis 07/10/2026 Boxer Holdings, LP /s/ Aaron Davis 07/10/2026 Boxer Holdings GP, LLC /s/ Aaron Davis 07/10/2026 Aaron Davis /s/ Aaron Davis 07/10/2026