As filed with the Securities and Exchange Commission on March 10, 2026

Registration No. 333-   

UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

FORM S-8

REGISTRATION STATEMENT

UNDER

THE SECURITIES ACT OF 1933

Q32 BIO INC.

(Exact name of registrant as specified in its charter)

830 Winter Street

Waltham, MA 02451

(781) 999-0232

(Address of Principal Executive Offices, Zip Code)

Q32 Bio Inc. 2024 Stock Option and Incentive Plan

Q32 Bio Inc. 2024 Employee Stock Purchase Plan

(Full title of the plan)

Jodie Morrison

Chief Executive Officer

Q32 Bio Inc.

830 Winter Street

Waltham, MA 02451

(781) 999-0232

(Name and address of agent for service; Telephone number, including area code, of agent for service)

Copies to:

Jacqueline Mercier, Esq.

Sarah Ashfaq, Esq.

Alicia M. Tschirhart, Esq.

Goodwin Procter LLP

100 Northern Avenue

Boston, MA 02210

(617) 570-1000

Indicate by check mark whether the registrant is a large accelerated filer, an accelerated filer, a non-accelerated filer, a smaller reporting company, or an emerging growth company. See the definitions of “large accelerated filer,” “accelerated filer,” “smaller reporting company,” and “emerging growth company” in Rule 12b-2 of the Exchange Act.

If an emerging growth company, indicate by check mark if the registrant has elected not to use the extended transition period for complying with any new or revised financial accounting standards provided pursuant to Section 7(a)(2)(B) of the Securities Act. ☐

EXPLANATORY NOTE

This Registration Statement on Form S-8 (this “Registration Statement”) is being filed by Q32 Bio Inc. (the “Registrant”) with the Securities and Exchange Commission (the “Commission”) to register 642,903 additional shares of its common stock, par value $0.0001 per share (the “Common Stock”), reserved for issuance under the Q32 Bio Inc. 2024 Stock Option and Incentive Plan (the “2024 Plan”) and 128,581 additional shares of its Common Stock, reserved for issuance under the Q32 Bio Inc. 2024 Employee Stock Purchase Plan (the “ESPP”), pursuant to the “evergreen” provision of each of the 2024 Plan and the ESPP. The number of shares of Common Stock reserved and available for issuance under the 2024 Plan is subject to an automatic annual increase on each January 1, beginning January 1, 2025, in an amount equal to the lesser of: (i) 5% of the outstanding shares on the immediately preceding December 31, or (ii) such lesser amount as determined by the Administrator (as defined in the 2024 Plan). The number of shares of Common Stock reserved and available for issuance under the ESPP is subject to an automatic annual increase by the lesser of (a) 241,677 shares of Common Stock, (b) one percent (1%) of the number of shares of Common Stock issued and outstanding on the immediately preceding December 31, or (c) such lesser number of shares of Common Stock as determined by the Administrator (as defined in the ESPP). The additional shares are of the same class as other securities relating to the 2024 Plan and the ESPP for which the Registrant’s registration statements filed on Form S-8 with the Commission on May 31, 2024 (File No. 333-279877) and March 11, 2025 (File No. 333-285699) are effective.

Pursuant to General Instruction E of Form S-8 regarding Registration of Additional Securities, the content of the Registrant’s Registration Statements on Form S-8 filed with the Commission on May 31, 2024 (File No. 333-279877) and March 11, 2025 (File No. 333-285699) relating to the 2024 Plan and the ESPP are hereby incorporated by reference in this Registration Statement, except to the extent supplemented, amended or superseded by the information set forth herein.

Part II

INFORMATION REQUIRED IN THE REGISTRATION STATEMENT

Item 8. Exhibits.

See the Exhibit Index below for a list of exhibits filed as part of this registration statement on Form S-8, which Exhibit Index is incorporated herein by reference.

EXHIBIT INDEX

SIGNATURES

Pursuant to the requirements of the Securities Act, the Registrant certifies that it has reasonable grounds to believe that it meets all of the requirements for filing on Form S-8 and has duly caused this Registration Statement to be signed on its behalf by the undersigned, thereunto duly authorized, in the City of Waltham, Commonwealth of Massachusetts, on this 10th day of March, 2026.

POWER OF ATTORNEY AND SIGNATURES

KNOW ALL BY THESE PRESENT, that each individual whose signature appears below hereby constitutes and appoints each of Jodie Morrison and Lee Kalowski, as such person’s true and lawful attorney-in-fact and agent with full power of substitution and resubstitution, for such person in such person’s name, place and stead, in any and all capacities, to sign any and all amendments (including post-effective amendments) to this Registration Statement, and to file the same, with all exhibits thereto, and all documents in connection therewith, with the Commission granting unto each said attorney-in-fact and agent full power and authority to do and perform each and every act and thing requisite and necessary to be done in and about the premises, as fully to all intents and purposes as such person might or could do in person, hereby ratifying and confirming all that any said attorney-in-fact and agent, or any substitute or substitutes of any of them, may lawfully do or cause to be done by virtue hereof.

Pursuant to the requirements of the Securities Act, this Registration Statement has been signed by the following person in the capacities and on the date indicated.

Exhibit 5.1

March 10, 2026

Q32 Bio Inc.

830 Winter Street

Waltham, MA 02451

Re: Securities Being Registered under Registration Statement on Form S-8

We have acted as your counsel in connection with your filing of a Registration Statement on Form S-8 (the “Registration Statement”) pursuant to the Securities Act of 1933, as amended (the “Securities Act”), on or about the date hereof relating to an aggregate of 771,484 shares (the “Shares”) of Common Stock, par value $0.0001 per share (“Common Stock”), of Q32 Bio Inc., a Delaware corporation (the “Company”), that may be issued pursuant to the Company’s 2024 Stock Option and Incentive Plan and 2024 Employee Stock Purchase Plan (collectively, the “Plans”).

We have reviewed such documents and made such examination of law as we have deemed appropriate to give the opinion set forth below. We have relied, without independent verification, on certificates of public officials and, as to matters of fact material to the opinion set forth below, on certificates of officers of the Company.

For purposes of the opinion set forth below, we have assumed that, at the time Shares are issued, the total number of then unissued Shares, when added to the number of shares of Common Stock issued, subscribed for, or otherwise committed to be issued, does not exceed the number of shares of Common Stock authorized by the Company’s certificate of incorporation.

The opinion set forth below is limited to the Delaware General Corporation Law.

Based on the foregoing, we are of the opinion that the Shares have been duly authorized and, when delivered against payment therefor in accordance with the terms of the Plans, will be validly issued, fully paid and nonassessable.

This opinion letter and the opinion it contains shall be interpreted in accordance with the Core Opinion Principles as published in 74 Business Lawyer 815 (Summer 2019).

We hereby consent to the inclusion of this opinion as Exhibit 5.1 to the Registration Statement. In giving our consent, we do not admit that we are in the category of persons whose consent is required under Section 7 of the Securities Act or the rules and regulations thereunder.

Exhibit 23.1

Consent of Independent Registered Public Accounting Firm

We consent to the incorporation by reference in the Registration Statement (Form S-8) pertaining to the Q32 Bio Inc. 2024 Stock Option and Incentive Plan and Q32 Bio Inc. 2024 Employee Stock Purchase Plan of our report dated March 10, 2026, with respect to the consolidated financial statements of Q32 Bio Inc. included in its Annual Report (Form 10-K) for the year ended December 31, 2025, filed with the Securities and Exchange Commission.

/s/ Ernst & Young LLP

Boston, Massachusetts

March 10, 2026