X0202 SCHEDULE 13G 0000918923 XXXXXXXX LIVE Common Stock, par value $0.0001 per share 05/28/2026 0001661998 Q32 Bio Inc. 746964105 830 WINTER STREET WALTHAM MA 02451 Rule 13d-1(c) BIOTECHNOLOGY VALUE FUND L P a DE 0.00 1248973.00 0.00 1248973.00 1248973.00 N 5.3 PN BVF I GP LLC a DE 0.00 1248973.00 0.00 1248973.00 1248973.00 N 5.3 OO BIOTECHNOLOGY VALUE FUND II LP a DE 0.00 929003.00 0.00 929003.00 929003.00 N 3.9 PN BVF II GP LLC a DE 0.00 929003.00 0.00 929003.00 929003.00 N 3.9 OO Biotechnology Value Trading Fund OS LP a E9 0.00 155156.00 0.00 155156.00 155156.00 N 0.7 PN BVF Partners OS Ltd. a E9 0.00 155156.00 0.00 155156.00 155156.00 N 0.7 CO BVF GP HOLDINGS LLC a DE 0.00 2177976.00 0.00 2177976.00 2177976.00 N 9.2 OO BVF PARTNERS L P/IL a DE 0.00 2367524.00 0.00 2367524.00 2367524.00 N 9.99 IA PN BVF INC/IL a DE 0.00 2367524.00 0.00 2367524.00 2367524.00 N 9.99 CO LAMPERT MARK N a X1 0.00 2367524.00 0.00 2367524.00 2367524.00 N 9.99 IN Q32 Bio Inc. 830 WINTER STREET, WALTHAM, MA 02451 Biotechnology Value Fund, L.P. ("BVF") BVF I GP LLC ("BVF GP") Biotechnology Value Fund II, L.P. ("BVF2") BVF II GP LLC ("BVF2 GP") Biotechnology Value Trading Fund OS LP ("Trading Fund OS") BVF Partners OS Ltd. ("Partners OS") BVF GP Holdings LLC ("BVF GPH") BVF Partners L.P. ("Partners") BVF Inc. Mark N. Lampert ("Mr. Lampert") Each of the foregoing is referred to as a "Reporting Person" and collectively as the "Reporting Persons." Biotechnology Value Fund, L.P. 44 Montgomery St., 40th Floor San Francisco, California 94104 BVF I GP LLC 44 Montgomery St., 40th Floor San Francisco, California 94104 Biotechnology Value Fund II, L.P. 44 Montgomery St., 40th Floor San Francisco, California 94104 BVF II GP LLC 44 Montgomery St., 40th Floor San Francisco, California 94104 Biotechnology Value Trading Fund OS LP PO Box 309 Ugland House Grand Cayman, KY1-1104 Cayman Islands BVF Partners OS Ltd. PO Box 309 Ugland House Grand Cayman, KY1-1104 Cayman Islands BVF GP Holdings LLC 44 Montgomery St., 40th Floor San Francisco, California 94104 BVF Partners L.P. 44 Montgomery St., 40th Floor San Francisco, California 94104 BVF Inc. 44 Montgomery St., 40th Floor San Francisco, California 94104 Mark N. Lampert 44 Montgomery St., 40th Floor San Francisco, California 94104 Biotechnology Value Fund, L.P. Delaware BVF I GP LLC Delaware Biotechnology Value Fund II, L.P. Delaware BVF II GP LLC Delaware Biotechnology Value Trading Fund OS LP Cayman Islands BVF Partners OS Ltd. Cayman Islands BVF GP Holdings LLC Delaware BVF Partners L.P. Delaware BVF Inc. Delaware Mark N. Lampert United States Y As of the close of business on June 4, 2026, the Reporting Persons and a certain Partners managed account (the "Partners Managed Account") held pre-funded warrants (the "Pre-Funded Warrants") exercisable for an aggregate of 150,000 shares of the Issuer's Common Stock, par value $0.0001 per share (the "Shares"). The Pre-Funded Warrants are exercisable at any time after the date of issuance and will expire when exercised in full. A holder of a Pre-Funded Warrant may not exercise such Pre-Funded Warrant if the holder, together with its affiliates, would beneficially own more than 9.99% (the "Ownership Limit") of the number of Shares outstanding immediately after giving effect to such exercise. As of the close of business on June 4, 2026, the Ownership Limit limits the exercise of the Pre-Funded Warrants held by the Reporting Persons and the Partners Managed Account to 17,524 out of the 150,000 Shares underlying the Pre-Funded Warrants held by them. As of the close of business on June 4, 2026, (i) BVF beneficially owned 1,248,973 Shares, including 17,524 Shares underlying certain Pre-Funded Warrants held by it and excluding 61,079 Shares underlying certain Pre-Funded Warrants held by it, (ii) BVF2 beneficially owned 929,003 Shares, excluding 59,298 Shares underlying the Pre-Funded Warrants held by it, and (iii) Trading Fund OS beneficially owned 155,156 Shares, excluding 9,904 Shares underlying the Pre-Funded Warrants held by it. BVF GP, as the general partner of BVF, may be deemed to beneficially own the 1,248,973 Shares beneficially owned by BVF. BVF2 GP, as the general partner of BVF2, may be deemed to beneficially own the 929,003 Shares beneficially owned by BVF2. Partners OS, as the general partner of Trading Fund OS, may be deemed to beneficially own the 155,156 Shares beneficially owned by Trading Fund OS. BVF GPH, as the sole member of each of BVF GP and BVF2 GP, may be deemed to beneficially own the 2,177,976 Shares beneficially owned in the aggregate by BVF and BVF2. Partners, as the investment manager of BVF, BVF2 and Trading Fund OS, and the sole member of Partners OS, may be deemed to beneficially own the 2,367,524 Shares beneficially owned in the aggregate by BVF, BVF2 and Trading Fund OS and held in the Partners Managed Account, including 34,392 Shares held in the Partners Managed Account, which excludes 2,195 Shares underlying the Pre-Funded Warrants held in the Partners Managed Account. BVF Inc., as the general partner of Partners, may be deemed to beneficially own the 2,367,524 Shares beneficially owned by Partners. Mr. Lampert, as a director and officer of BVF Inc., may be deemed to beneficially own the 2,367,524 Shares beneficially owned by BVF Inc. The foregoing should not be construed in and of itself as an admission by any Reporting Person as to beneficial ownership of any Shares owned by another Reporting Person. BVF GP disclaims beneficial ownership of the Shares beneficially owned by BVF. BVF2 GP disclaims beneficial ownership of the Shares beneficially owned by BVF2. Partners OS disclaims beneficial ownership of the Shares beneficially owned by Trading Fund OS. BVF GPH disclaims beneficial ownership of the Shares beneficially owned by BVF and BVF2. Each of Partners, BVF Inc. and Mr. Lampert disclaims beneficial ownership of the Shares beneficially owned by BVF, BVF2 and Trading Fund OS and held in the Partners Managed Account, and the filing of this statement shall not be construed as an admission that any such person or entity is the beneficial owner of any such securities. The following percentages are based upon a denominator that is the sum of: (i) 16,956,415 Shares outstanding 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, (ii) 6,725,000 Shares issued and sold by the Issuer pursuant to a Securities Purchase Agreement, dated May 26, 2026, as set forth in the Issuer's Current Report on Form 8-K filed with the Securities and Exchange Commission on May 27, 2026, and (iii) 17,524 Shares issuable upon the exercise of certain Pre-Funded Warrants held by the Reporting Persons, as applicable. As of the close of business on June 4, 2026, (i) BVF beneficially owned approximately 5.3% of the outstanding Shares, (ii) BVF2 beneficially owned approximately 3.9% of the outstanding Shares, (iii) Trading Fund OS beneficially owned less than 1% of the outstanding Shares, (iv) BVF GP may be deemed to beneficially own approximately 5.3% of the outstanding Shares, (v) BVF2 GP may be deemed to beneficially own approximately 3.9% of the outstanding Shares, (vi) Partners OS may be deemed to beneficially own less than 1% of the outstanding Shares, (vii) BVF GPH may be deemed to beneficially own approximately 9.2% of the outstanding Shares, and (viii) each of Partners, BVF Inc. and Mr. Lampert may be deemed to beneficially own approximately 9.99% of the outstanding Shares (less than 1% of the outstanding Shares are held in the Partners Managed Account). See Cover Pages Items 5-9. See Cover Pages Items 5-9. See Cover Pages Items 5-9. See Cover Pages Items 5-9. Y N BVF GP, BVF GPH, Partners, BVF Inc. and Mr. Lampert share voting and dispositive power over the Shares beneficially owned by BVF. BVF GPH, Partners, BVF Inc. and Mr. Lampert share voting and dispositive power over the Shares beneficially owned by BVF2. Partners, BVF Inc. and Mr. Lampert share voting and dispositive power over the Shares beneficially owned by Trading Fund OS and held in the Partners Managed Account. Y N See Exhibit 99.1. Y N By signing below I certify that, to the best of my knowledge and belief, the securities referred to above 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. 99.1 - Joint Filing Agreement, June 4, 2026. BIOTECHNOLOGY VALUE FUND L P /s/ Mark N. Lampert 06/04/2026 BVF I GP LLC /s/ Mark N. Lampert 06/04/2026 BIOTECHNOLOGY VALUE FUND II LP /s/ Mark N. Lampert 06/04/2026 BVF II GP LLC /s/ Mark N. Lampert 06/04/2026 Biotechnology Value Trading Fund OS LP /s/ Mark N. Lampert 06/04/2026 BVF Partners OS Ltd. /s/ Mark N. Lampert 06/04/2026 BVF GP HOLDINGS LLC /s/ Mark N. Lampert 06/04/2026 BVF PARTNERS L P/IL /s/ Mark N. Lampert 06/04/2026 BVF INC/IL /s/ Mark N. Lampert 06/04/2026 LAMPERT MARK N /s/ Mark N. Lampert 06/04/2026