The information in this proxy statement/prospectus is not complete and may be changed. We may not sell these securities until the registration statement filed with the Securities and Exchange Commission is effective. This proxy statement/prospectus is not an offer to sell these securities and it is not soliciting an offer to buy these securities in any jurisdiction where the offer or sale is not permitted.

SUBJECT TO COMPLETION, DATED DECEMBER 15, 2023

PROPOSED MERGER

YOUR VOTE IS VERY IMPORTANT

To the Stockholders of Homology Medicines, Inc. and Q32 Bio Inc.,

Homology Medicines, Inc., a Delaware corporation, or Homology, and Q32 Bio Inc., a Delaware corporation, or Q32, entered into an Agreement and Plan of Merger, or the Merger Agreement, on November 16, 2023, pursuant to which a direct, wholly owned subsidiary of Homology, Kenobi Merger Sub, Inc., or Merger Sub, will merge with and into Q32, with Q32 surviving as a direct, wholly owned subsidiary of Homology, and the surviving corporation of the merger, which transaction is referred to herein as the Merger. Homology following the Merger is also referred to herein as the combined company.

At the time the certificate of merger is filed with and accepted by the Secretary of State of the State of Delaware, or the Effective Time, as described in more detail in the section titled “The Merger—Effective Time of the Merger” beginning on page 182 of the accompanying proxy statement/prospectus, each share of Q32 common stock (after giving effect to the conversion of each share of Q32’s preferred stock into Q32 common stock and the conversion of Q32’s convertible notes into Q32 common stock and including all such shares that are converted into Q32 common stock) will be converted into the right to receive a number of shares of Homology common stock equal to the total number of shares of Homology common stock to be issued in the Merger multiplied by the applicable Q32 stockholder’s percentage interest in Q32 as set forth in the allocation certificate to be provided by Q32, or the Allocation Certificate, and as described in more detail in the section titled “The Merger Agreement—Allocation Certificate” beginning on page 188 of the accompanying proxy statement/prospectus. The Q32 common stock that will be converted in connection with the Merger includes Q32 common stock to be issued pursuant to the subscription agreement by and among Q32 and certain parties to purchase an aggregate of $42.0 million of shares of Q32’s common stock, which transaction is referred to as the Pre-Closing Financing. If any Q32 common stock outstanding immediately prior to the Effective Time is unvested or is subject to a repurchase option or a risk of forfeiture under any applicable agreement with Q32, then the shares of Homology common stock issued in exchange for such shares of Q32 common stock will to the same extent be unvested and subject to the same repurchase option or risk of forfeiture, and such shares of Homology common stock will be marked with appropriate legends.

In connection with the Merger, each option to purchase shares of Q32 common stock outstanding as of immediately prior to the Effective Time will be assumed by Homology and converted, at the Effective Time, into an option to acquire the number of shares of Homology common stock equal to the number of shares of Q32 common stock subject to such option as of immediately prior to the Effective Time multiplied by the exchange ratio formula in the Merger Agreement and rounding that result down to the nearest whole number of shares, at a per share exercise price equal to the per share exercise price of such option immediately prior to the Effective Time multiplied by the exchange ratio formula in the Merger Agreement, rounded up to the nearest whole cent, and each unexercised warrant to purchase shares of Q32 common stock outstanding immediately prior to the Effective Time will be assumed by Homology and converted into a warrant to purchase shares of Homology’s common stock, with adjustments to the number of shares and the exercise price to reflect the exchange ratio formula in the Merger Agreement.

Each share of Homology common stock that is issued and outstanding at the Effective Time will remain issued and outstanding and such shares will be unaffected by the Merger but will be subject to a proposed reverse stock split of Homology’s issued and outstanding common stock at a ratio ranging from any whole number between 1-for-                 and 1-for-                 as determined by the Homology board of directors in its discretion, or the Reverse Stock Split, as described in the section titled “Matters Being Submitted to a Vote of Homology Stockholders—Proposal No. 3: Approval of the Amendment to the Restated Certificate of Incorporation of

Homology Effecting the Reverse Stock Split” beginning on page 233 of the accompanying proxy statement/prospectus. Each outstanding option to purchase shares of Homology common stock that has an exercise price per share that is less than the closing trading price of a share of Homology common stock on the last full trading date on which the Homology common stock is traded prior to the date on which the Effective Time occurs, which is referred to as a Homology ITM Option, will vest in full immediately prior to the Effective Time and remain outstanding, subject to proportionate adjustment in accordance with the terms of Homology’s 2018 Incentive Award Plan or 2015 Stock Incentive Plan, as applicable, to reflect the Reverse Stock Split and the issuance of the contingent value rights, or CVRs. Each outstanding option to purchase shares of Homology common stock that is not a Homology ITM Option will be cancelled for no consideration immediately prior to the Effective Time. Each restricted stock unit award covering shares of Homology common stock, which is referred to as a Homology Restricted Stock Unit, that is outstanding will vest in full immediately prior to the Effective Time, and the holder of each unsettled Homology Restricted Stock Unit will receive immediately prior to the Effective Time, the number of shares of Homology common stock equal to the number of vested and unsettled shares of Homology common stock underlying such Homology Restricted Stock Unit.

Immediately after the Merger, Homology securityholders as of immediately prior to the Merger are expected to own approximately 25% of the outstanding shares of the combined company on a fully-diluted basis and former Q32 securityholders (including purchasers in the Pre-Closing Financing) are expected to own approximately 75% of the outstanding shares of the combined company on a fully-diluted basis, subject to certain assumptions, including, but not limited to, Homology’s net cash as of closing being equal to $60.0 million and Q32 issuing approximately $42.0 million of Q32 common stock in the Pre-Closing Financing described elsewhere in this proxy statement/prospectus. Under certain circumstances further described in the Merger Agreement, the ownership percentages may be adjusted up or down including, but not limited to, if Homology’s net cash as of closing is lower than $59.5 million or greater than $60.5 million.

Shares of Homology common stock are currently listed on The Nasdaq Global Select Market, or Nasdaq, under the symbol “FIXX.” Q32 intends to file an initial listing application for the combined company with the Nasdaq Stock Market LLC. After completion of the Merger, Homology will be renamed “Q32 Bio Inc.” and it is expected that the common stock of the combined company will trade on Nasdaq under the symbol “QTTB.” On                 , 2024, the last trading day before the date of the accompanying proxy statement/prospectus, the closing sale price of Homology common stock was $                 per share.

Homology stockholders are cordially invited to attend the special meeting of Homology stockholders, or the Homology Special Meeting. Homology is holding the Homology Special Meeting, on                 , 2024, at                  Eastern Time, unless postponed or adjourned to a later date, in order to obtain the stockholder approvals necessary to complete the Merger. The Homology Special Meeting will be held entirely online. Homology stockholders will be able to attend and participate in the Homology Special Meeting online by visiting                  where they will be able to listen to the meeting live, submit questions and vote. At the Homology Special Meeting, Homology will ask its stockholders:

As described in the accompanying proxy statement/prospectus, certain Homology stockholders who in the aggregate owned approximately 18.3% of the outstanding shares of Homology as of November 30, 2023, and certain Q32 stockholders who in the aggregate owned approximately 74.1% of the outstanding shares of Q32 common stock and Q32 preferred stock as of October 31, 2023, are parties to stockholder support agreements with Homology and Q32, respectively, whereby such stockholders have agreed to vote in favor of the approval of the transactions contemplated therein, including, with respect to such Q32 stockholders, adoption of the Merger Agreement and approval of the Merger and, with respect to such Homology stockholders, the issuance of Homology common stock in the Merger pursuant to the Merger Agreement, subject to the terms of the support agreements. Following the effectiveness of the registration statement on Form S-4 of which the accompanying proxy statement/prospectus is a part and pursuant to the Merger Agreement, Q32 stockholders holding a sufficient number of shares of Q32 common stock to adopt the Merger Agreement and approve the Merger and related transactions will be asked to execute written consents providing for such adoption and approval.

After careful consideration, each of the Homology and Q32 boards of directors have approved the Merger Agreement and have determined that it is advisable to consummate the Merger. The Homology board of directors has approved the proposals described in the accompanying proxy statement/prospectus and unanimously recommends that its stockholders vote “FOR” each of the proposals described in the accompanying proxy statement/prospectus.

More information about Homology, Q32, the Merger Agreement and transactions contemplated thereby and the foregoing proposals is contained in the accompanying proxy statement/prospectus. Homology urges you to read the accompanying proxy statement/prospectus carefully and in its entirety. IN PARTICULAR, YOU SHOULD CAREFULLY CONSIDER THE MATTERS DISCUSSED UNDER “RISK FACTORS” BEGINNING ON PAGE 29 OF THE ACCOMPANYING PROXY STATEMENT/PROSPECTUS.

Homology and Q32 are excited about the opportunities the Merger brings to Homology’s and Q32’s stockholders and thank you for your consideration and continued support.

Sincerely,

Neither the Securities and Exchange Commission nor any state securities commission has approved or disapproved of these securities or passed upon the adequacy or accuracy of the accompanying proxy statement/prospectus. Any representation to the contrary is a criminal offense.

The accompanying proxy statement/prospectus is dated                      and is first being mailed to Homology stockholders on or about                  .

HOMOLOGY MEDICINES, INC.

ONE PATRIOTS PARK

BEDFORD, MA 01730

(781) 327-2633

NOTICE OF SPECIAL MEETING OF STOCKHOLDERS

To the stockholders of Homology Medicines, Inc., or Homology:

NOTICE IS HEREBY GIVEN that a special meeting of stockholders of Homology, or the Homology Special Meeting, will be held on                 , 2024, at                 Eastern Time, unless postponed or adjourned to a later date. The Homology Special Meeting will be held entirely online. You will be able to attend and participate in the Homology Special Meeting online by visiting                  where you will be able to listen to the Homology Special Meeting live, submit questions and vote.

The Homology Special Meeting will be held for the following purposes:

Record Date:    Homology’s board of directors has fixed                 as the record date for the determination of stockholders entitled to notice of, and to vote at, the Homology Special Meeting and any adjournment or postponement thereof. Only holders of record of shares of Homology common stock at the close of business on the record date are entitled to notice of, and to vote at, the Homology Special Meeting. At the close of business on the record date, Homology had                  shares of common stock outstanding and entitled to vote.

Your vote is important. The affirmative vote of the holders of a majority in voting power of the votes cast affirmatively or negatively at the Homology Special Meeting by the holders entitled to vote thereon is required for approval of the Stock Issuance Proposal, the Authorized Share Increase Proposal, the

Reverse Stock Split Proposal, the Stock Option and Incentive Plan Proposal, the ESPP Proposal and the Adjournment Proposal. Approval of the Stock Issuance Proposal, the Authorized Share Increase Proposal and the Reverse Stock Split Proposal is a condition to the completion of the Merger. Therefore, the Merger cannot be consummated without the approval of the Stock Issuance Proposal, the Authorized Share Increase Proposal and the Reverse Stock Split Proposal.

Even if you plan to attend the Homology Special Meeting, Homology requests that you sign, date and promptly return the enclosed proxy card or vote by telephone or online to ensure that your shares will be represented at the Homology Special Meeting. You may change or revoke your proxy at any time before it is voted at the Homology Special Meeting.

HOMOLOGY’S BOARD OF DIRECTORS HAS DETERMINED AND BELIEVES THAT EACH OF THE PROPOSALS OUTLINED ABOVE IS FAIR TO, IN THE BEST INTERESTS OF, AND ADVISABLE TO HOMOLOGY AND ITS STOCKHOLDERS AND HAS APPROVED EACH SUCH PROPOSAL. HOMOLOGY’S BOARD OF DIRECTORS UNANIMOUSLY RECOMMENDS THAT HOMOLOGY STOCKHOLDERS VOTE “FOR” EACH SUCH PROPOSAL.

By Order of Homology’s Board of Directors,

Paul Alloway, Ph.D.

President and Chief Operating Officer

Bedford, MA

            ,

ADDITIONAL INFORMATION

This proxy statement/prospectus incorporates important business and financial information about Homology Medicines, Inc. that is not included in or delivered with this document. You may obtain this information without charge through the Securities and Exchange Commission website (www.sec.gov).

If you would like to request documents from Homology or Q32, please send a request in writing or by telephone to either Homology or Q32 at the following addresses:

If you are a Homology stockholder and would like additional copies, without charge, of this proxy statement/prospectus or if you have questions about the Merger, including the procedures for voting your shares, you should contact Homology’s proxy solicitor, Morrow Sodali LLC, or Morrow Sodali, at the following address and telephone number:

Morrow Sodali LLC

430 Park Avenue, 14th Floor

New York, NY 10022

Banks and Brokers Call: (203) 658-9400

Stockholders Call Toll Free: (800) 662-5200

To ensure timely delivery of these documents, any request should be made no later than                 , to receive them before the Homology Special Meeting.

For additional details about where you can find information about Homology, please see the section titled “Where You Can Find More Information” beginning on page 450 of this proxy statement/prospectus.

ABOUT THIS PROXY STATEMENT/PROSPECTUS

This document, which forms part of a registration statement on Form S-4 filed with the U.S. Securities and Exchange Commission, or the SEC, by Homology Medicines, Inc., or Homology, constitutes a prospectus of Homology under the Securities Act of 1933, as amended, or the Securities Act, with respect to the shares of common stock of Homology to be issued (or reserved for issuance) to the securityholders of Q32 Bio Inc., or Q32, pursuant to the Agreement and Plan of Merger, dated as of November 16, 2023, by and among Homology, Kenobi Merger Sub, Inc., a direct, wholly owned subsidiary of Homology, or Merger Sub, and Q32, as it may be amended from time to time, or the Merger Agreement, pursuant to which Merger Sub will merge with and into Q32, with Q32 surviving as a wholly owned subsidiary of Homology, and the surviving corporation of the merger, or the Merger. This document also constitutes a proxy statement of Homology under Section 14(a) of the Securities Exchange Act of 1934, as amended, or the Exchange Act. It also constitutes a notice of meeting with respect to the special meeting of Homology stockholders, or the Homology Special Meeting, at which Homology stockholders will be asked to consider and vote, among other matters, on the issuance of the shares of Homology common stock pursuant to the Merger Agreement and the change of control resulting from the Merger. Homology following the Merger is referred to in this proxy statement/prospectus as the combined company.

Homology has supplied all information contained in this proxy statement/prospectus relating to Homology. Q32 has supplied all information contained in this proxy statement/prospectus relating to Q32.

You should rely only on the information contained in this proxy statement/prospectus. Homology and Q32 have not authorized anyone to provide you with information that is different from that contained in this proxy statement/prospectus. This proxy statement/prospectus is dated                 , 2024, and you should not assume that the information contained in this proxy statement/prospectus is accurate as of any date other than such date. Neither the mailing of this proxy statement/prospectus to Homology stockholders nor the issuance by Homology of shares of Homology common stock pursuant to the Merger Agreement will create any implication to the contrary.

Except where otherwise noted, the information contained in this proxy statement/prospectus does not give effect to the proposed reverse stock split of Homology’s issued and outstanding common stock at a ratio ranging from any whole number between 1-for-                 and 1-for-                 as determined by the Homology board of directors in its discretion, or the Reverse Stock Split, described in the section titled “Matters Being Submitted to a Vote of Homology Stockholders—Proposal No. 3: Approval of the Amendment to the Restated Certificate of Incorporation of Homology Effecting the Reverse Stock Split” beginning on page 233 of this proxy statement/prospectus.

Homology and Q32 have proprietary rights to trademarks, trade names and service marks appearing in this proxy statement/prospectus that are important to their respective businesses. Solely for convenience, the trademarks, trade names and service marks may appear in this proxy statement/prospectus without the ® and TM symbols, but any such references are not intended to indicate, in any way, that Homology or Q32 forgo or will not assert, to the fullest extent under applicable law, their rights or the rights of the applicable licensors to these trademarks, trade names and service marks. All trademarks, trade names and service marks appearing in this proxy statement/prospectus are the property of their respective owners.

TABLE OF CONTENTS

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CAUTIONARY STATEMENT CONCERNING FORWARD-LOOKING STATEMENTS

This proxy statement/prospectus contains forward-looking statements relating to Homology, Q32, the Merger, the combined company, and the other proposed transactions.

These forward-looking statements are based on current expectations and beliefs and involve numerous risks and uncertainties that could cause actual results to differ materially from expectations. These forward-looking statements should not be relied upon as predictions of future events as Homology and Q32 cannot assure you that the events or circumstances reflected in these statements will be achieved or will occur. You can identify forward-looking statements by the use of forward-looking terminology including “believes,” “expects,” “may,” “will,” “should,” “seeks,” “intends,” “plans,” “pro forma,” “estimates” or “anticipates” or the negative of these words and phrases or other variations of these words and phrases or comparable terminology. All statements other than statements of historical fact are statements that could be deemed forward-looking statements. Forward-looking statements include, but are not limited to, any statements regarding the strategies, prospects, plans, expectations or objectives of management of Homology or Q32 for future operations of the combined company, the progress, scope or timing of the development of the combined company’s product candidates, the expectations surrounding the potential safety, efficacy, and regulatory and clinical progress of Q32’s product candidates, including bempikibart and ADX-097, and anticipated milestones and timing therefor, the benefits that may be derived from any future products or the commercial or market opportunity with respect to any future products of the combined company, the ability of the combined company to protect its intellectual property rights, the anticipated operations, financial position, ability to raise capital to fund operations, revenues, costs or expenses of Homology, Q32 or the combined company, statements regarding future economic conditions or performance, statements of belief and any statement of assumptions underlying any of the foregoing. Forward-looking statements may also include any statements regarding the approval and closing of the Merger, including the conditions to and timing of closing of the Merger, the location and management of the combined company, the percentage ownership of the combined company, and the parties’ ability to consummate the proposed transaction, the Pre-Closing Financing, the composition of the board of directors of the combined company, the expected issuance of the CVRs and the contingent payments contemplated by the CVRs, the combined company’s expected cash and the sufficiency of the combined company’s cash, cash equivalents and short-term investments to fund operations into mid-2026, the listing of the combined company’s shares on Nasdaq, and any statement of assumptions underlying any of the foregoing.

For a discussion of the factors that may cause Homology, Q32 or the combined company’s actual results, performance or achievements to differ materially from any future results, performance or achievements expressed or implied in such forward-looking statements, or for a discussion of risks associated with the ability of Homology and Q32 to complete the Merger and the effect of the Merger on the business of Homology, Q32 and the combined company, see the section titled “Risk Factors” beginning on page 29 of this proxy statement/prospectus.

If any of these risks or uncertainties materialize or any of these assumptions prove incorrect, the results of Homology, Q32 or the combined company could differ materially from the forward-looking statements. All forward-looking statements in this proxy statement/prospectus are current only as of the date of this proxy statement/prospectus. Homology and Q32 do not undertake any obligation to (and expressly disclaim any such obligation to) publicly update any forward-looking statement to reflect events or circumstances after the date of this proxy statement/prospectus or to reflect the occurrence of unanticipated events.

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QUESTIONS AND ANSWERS

The following section provides answers to frequently asked questions about the Merger, general information about the Homology Special Meeting and voting. For some questions, this section provides only summary information. For a more complete response to these questions and for additional information, please refer to the cross-referenced sections.

Questions and Answers About the Merger

Immediately after the Merger, Homology securityholders as of immediately prior to the Merger are expected to own approximately 25% of the outstanding shares of the combined company on a fully-diluted basis and former Q32 securityholders (including purchasers in the Pre-Closing Financing) are expected to own approximately 75% of the outstanding shares of the combined company on a fully-diluted basis, subject to certain assumptions, including, but not limited to, Homology’s net cash as of closing being equal to $60.0 million and Q32 receiving $42.0 million in gross proceeds in exchange for issuance of Q32 common stock in the Pre-Closing Financing described elsewhere in this proxy statement/prospectus. Under certain circumstances further described in the Merger Agreement, the ownership percentages may be adjusted up or down including, but not limited to, if Homology’s net cash as of closing is lower than $59.5 million or greater than $60.5 million.

At the Effective Time, each share of Q32 common stock (after giving effect to the conversion of each share of Q32’s preferred stock into Q32 common stock and the conversion of Q32’s convertible notes into Q32 common stock and including all such shares that are converted into Q32 common stock) will be converted into the right to receive a number of shares of Homology common stock equal to the total number of shares of Homology common stock to be issued in the Merger multiplied by the applicable Q32 stockholder’s percentage interest in Q32 as set forth in the Allocation Certificate, and as described in more detail in the section titled “The Merger Agreement—Allocation Certificate” beginning on page 188 of the accompanying proxy statement/prospectus. The Q32 common stock that will be converted in the Merger includes Q32 common stock to be issued pursuant to the subscription agreement by and among Q32 and certain investors to purchase shares of Q32’s common stock for an aggregate purchase price of approximately $42.0 million, which transaction is referred to as the Pre-Closing Financing. If any Q32 common stock outstanding immediately prior to the Effective Time is unvested or is subject to a repurchase option or a risk of forfeiture under any applicable agreement with Q32, then the shares of Homology common stock issued in exchange for such shares of Q32 common stock will to the same extent be unvested and subject to the same repurchase option or risk of forfeiture, and such shares of Homology common stock will be marked with appropriate legends.

In connection with the Merger, each option to purchase shares of Q32 common stock outstanding as of immediately prior to the Effective Time will be assumed by Homology and converted, at the Effective

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Time, into an option to acquire, on the same terms and conditions (including the same vesting and exercisability terms and conditions), the number of shares of Homology common stock equal to the number of shares of Q32 common stock subject to such option as of immediately prior to the Effective Time multiplied by the exchange ratio formula in the Merger Agreement and rounding that result down to the nearest whole number of shares, at a per share exercise price equal to the per share exercise price of such option immediately prior to the Effective Time multiplied by the exchange ratio formula in the Merger Agreement, rounded up to the nearest whole cent, as described in more detail in the section titled “The Merger Agreement—Treatment of Q32 Options” beginning on page 191 of this proxy statement/prospectus. In addition, at the Effective Time, each unexercised warrant to purchase shares of Q32 common stock outstanding immediately prior to the Effective Time will be assumed by Homology and converted into a warrant to purchase shares of Homology’s common stock, with adjustments to the number of shares and the exercise price to reflect the exchange ratio formula in the Merger Agreement, as described in more detail in the section titled “The Merger Agreement—Treatment of Q32 Warrants” beginning on page 191 of this proxy statement/prospectus.

Each outstanding Homology ITM Option will vest in full immediately prior to the Effective Time and remain outstanding, subject to proportionate adjustment in accordance with the terms of Homology’s 2018 Incentive Award Plan or 2015 Stock Incentive Plan, as applicable, to reflect the Reverse Stock Split and the issuance of the CVRs, and each option to purchase Homology common stock that is not a Homology ITM Option will be cancelled for no consideration immediately prior to the Effective Time. Each Homology Restricted Stock Unit that is outstanding will vest in full immediately prior to the Effective Time, and the holder of each unsettled Homology Restricted Stock Unit will receive immediately prior to the Effective Time, the number of shares of Homology common stock equal to the number of vested and unsettled shares of Homology common stock underlying such Homology Restricted Stock Unit.

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In connection with the Merger, each option to purchase shares of Q32 common stock outstanding as of immediately prior to the Effective Time will be assumed by Homology and converted, at the Effective Time, into an option to acquire, on the same terms and conditions (including the same vesting and exercisability terms and conditions), the number of shares of Homology common stock equal to the number of shares of Q32 common stock subject to such option as of immediately prior to the Effective Time multiplied by the exchange ratio formula in the Merger Agreement and rounding that result down to the nearest whole number of shares, at a per share exercise price equal to the per share exercise price of such option immediately prior to the Effective Time multiplied by the exchange ratio formula in the Merger Agreement, rounded up to the nearest whole cent.

At the Effective Time, each unexercised warrant to purchase shares of Q32 common stock outstanding immediately prior to the Effective Time will be assumed by Homology and converted into a warrant to purchase shares of Homology’s common stock, with adjustments to the number of shares and the exercise price to reflect the exchange ratio formula in the Merger Agreement.

Immediately prior to the Effective Time, Q32 will cause the outstanding principal and accrued but unpaid interest on the convertible notes issued by Q32 on May 20, 2022, or the Q32 Convertible Notes, to be converted into the number of shares of Q32 common stock provided for under the terms of such Q32 Convertible Note, or the Q32 Note Conversion. In addition, outstanding preferred stock of Q32, or the Q32 Preferred Stock, will be converted into Q32 common stock immediately prior to the Effective Time in accordance with, and pursuant to the terms and conditions of, the organizational documents of Q32, or the Q32 Preferred Stock Conversion. In connection with the Merger, all shares of Q32 common stock issued pursuant to the Q32 Note Conversion and the Q32 Preferred Stock Conversion will be cancelled and converted into the right to receive Homology common stock in accordance with the terms of the Merger Agreement.

For a more complete description of what Q32 securityholders will receive in the Merger, please see the sections titled “The Merger Agreement—Merger Consideration,” “The Merger Agreement—Treatment of Q32 Warrants” and “The Merger Agreement—Treatment of Q32 Options” beginning on pages 187, 191 and 191, respectively, of this proxy statement/prospectus.

It is anticipated the director classes of the combined company board of directors will be as follows:

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Each CVR will represent the contractual right to receive payments from Homology upon the actual receipt by Homology or its subsidiaries of certain contingent proceeds derived from any cash consideration that is paid to Homology or its subsidiaries as a result of the sale, transfer, license, assignment or other divestiture, disposition or commercialization of the following, or the Legacy Assets, and such disposition, a Legacy Asset Disposition: any of Homology’s assets, rights and interests relating to Homology’s HMI-103 product candidate (Adult/Pediatric PKU), HMI-204 product candidate (MLD) and Homology’s Capsids and AAVHSC Platform, including any equity interests held directly or indirectly by Homology in Oxford Biomedica Solutions LLC or its affiliates, or OXB Solutions, pursuant to that certain Equity Securities Purchase Agreement, dated as of January 28, 2022, by and between Homology and OXB Solutions, in which Homology currently owns 20% of the fully diluted equity interests in OXB Solutions and Homology is entitled to exercise a put option to sell or transfer Homology’s equity interests in OXB Solutions set forth therein on March 10, 2025, such interests, the Oxford Assets. Payments of the proceeds from a Legacy Asset Disposition will be net of certain taxes, transaction costs and certain other expenses.

The contingent payments under the CVR Agreement, if they become payable, will become payable to the Rights Agent for subsequent distribution to the holders of the CVRs. In the event there is no Legacy Asset Disposition (other than with respect to the Oxford Assets) prior to the 18-month anniversary of the closing date of the Merger, or the Closing Date, holders will not receive any payments pursuant to the CVR Agreement with respect to the Legacy Assets (other than possibly the Oxford Assets). If no disposition of the Oxford Assets occurs prior to the 24-month anniversary of the Closing Date, holders will not receive any payments pursuant to the CVR Agreement with respect to the Oxford Assets. There can be no assurance than any Legacy Asset Disposition (including the disposition of Oxford Assets) will occur or that any holders of CVRs will receive payments with respect thereto.

The right to the contingent payments contemplated by the CVR Agreement is a contractual right only and will not be transferable, except in the limited circumstances specified in the CVR Agreement. The CVRs will not be evidenced by a certificate or any other instrument and will not be registered with the SEC. The CVRs will not have any voting or dividend rights and will not represent any equity or ownership interest in Homology or the combined company or any of its subsidiaries. No interest will accrue on any amounts payable in respect of the CVRs.

For a more detailed description of the CVRs and the CVR Agreement, see “Agreements Related to the Merger—Contingent Value Rights Agreement” beginning on page 211 of this proxy statement/prospectus.

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The closing of the Merger is not conditioned upon the receipt of an opinion of counsel or a ruling from the IRS regarding the U.S. federal income tax treatment of the Merger, and no opinion of counsel or ruling from the IRS will be requested regarding such treatment. Accordingly, there can be no assurance that the IRS will not challenge the qualification of the Merger as a “reorganization” within the meaning of Section 368(a) of the Code or that a court will not sustain such a challenge by the IRS.

The tax consequences to you of the Merger will depend on your particular facts and circumstances. Please consult your tax advisor as to the tax consequences of the Merger in your particular circumstances, including the applicability and effect of U.S. federal, state, local and foreign income and other tax laws. For a more detailed discussion of the material U.S. federal income tax consequences of the Merger, see “Material U.S. Federal Income Tax Consequences of the Merger” beginning on page 220.

Questions and Answers About the Homology Special Meeting and Voting

In addition, each of the other closing conditions set forth in the Merger Agreement must be satisfied or waived for the Merger to close. For a more complete description of the closing conditions under the Merger

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Agreement, please see the section titled “The Merger Agreement—Conditions to the Completion of the Merger” beginning on page 204 of this proxy statement/prospectus.

At the Homology Special Meeting, the holders of Homology common stock will also be asked to consider the following proposals:

The approval of the Stock Option and Incentive Plan Proposal, the ESPP Proposal and the Adjournment Proposal is not a condition to the Merger closing.

Telephone and Internet voting facilities for stockholders of record will be available 24 hours a day and will close at 11:59 p.m. Eastern Time on                 , 2024.

If you attend the Homology Special Meeting online, you will need the 16-digit control number included on your proxy card or on the instructions that accompanied your proxy materials to vote electronically during the meeting.

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Whether or not you expect to attend the Homology Special Meeting online, we urge you to vote your shares as promptly as possible to ensure your representation and the presence of a quorum at the Homology Special Meeting. If you submit your proxy, you may still decide to attend the Homology Special Meeting and vote your shares electronically.

If your shares are held in “street name” through a bank or broker, you will receive instructions on how to vote from the bank or broker. You must follow their instructions in order for your shares to be voted. Internet and telephone voting also may be offered to stockholders owning shares through certain banks and brokers. If your shares are not registered in your own name and you would like to vote your shares electronically at the Homology Special Meeting, you should contact your bank or broker to obtain your 16-digit control number or otherwise vote through the bank or broker. If you lose your 16-digit control number, you may join the Homology Special Meeting as a “Guest” but you will not be able to vote, ask questions or access the list of stockholders as of the Record Date. You will need to obtain your own Internet access if you choose to attend the Homology Special Meeting online and/or vote over the Internet.

A broker is entitled to vote shares held for a beneficial owner on routine matters without instructions from the beneficial owner of those shares. On the other hand, absent instructions from the beneficial owner of such shares, a broker is not entitled to vote shares held for a beneficial owner on non-routine matters.

It is anticipated that all of the proposals currently scheduled for consideration at the Homology Special Meeting will be considered “non-routine” matters, and a broker will lack the authority to vote shares at its discretion on such proposals. Consequently, Homology expects that there will not be any broker non-votes at the Homology Special Meeting. If broker non-votes were received, they would not have any impact on the outcome of the proposals.

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Broker non-votes will also be considered present for the purpose of determining whether there is a quorum for the Homology Special Meeting.

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Certain directors and executive officers of Homology have entered into stockholder support agreements pursuant to which they have agreed to vote all shares of Homology common stock owned by them as of the Record Date in favor of the Stock Issuance Proposal, the Authorized Share Increase Proposal and the Reverse Stock Split Proposal and against any competing “acquisition proposal” (as defined in the support agreements). As of the Record Date, the directors and certain executive officers of Homology owned or controlled     % of the outstanding shares of Homology common stock entitled to vote at the Homology Special Meeting.

Your most recent proxy card or Internet or telephone proxy is the one that is counted. Your attendance at the Homology Special Meeting by itself will not revoke your proxy unless you give written notice of revocation to the Secretary of Homology before your proxy is voted or you vote electronically at the Homology Special Meeting.

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Homology Medicines, Inc.

One Patriots Park

Bedford, Massachusetts 01730

Telephone: Tel: (781) 327-2633

Attn: Paul Alloway, Ph.D.

If your shares are held in street name, please contact your bank, broker or other nominee.

To ensure timely delivery of documents prior to the Homology Special Meeting, any requests must be made no later than                 ,     .

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MARKET PRICE AND DIVIDEND INFORMATION

Shares of Homology common stock are currently listed on Nasdaq under the symbol “FIXX.” The closing price of Homology common stock on November 15, 2023, the last trading day prior to the public announcement of the Merger, was $0.88 per share, as reported on Nasdaq. The closing price of the Homology common stock on                 , 2024, as reported on Nasdaq, was $                 per share.

Because the market price of Homology common stock is subject to fluctuation, the market value of the shares of Homology common stock that Q32 stockholders will be entitled to receive in the Merger may increase or decrease.

Q32 is a private company, and its shares of common stock and preferred stock are not publicly traded.

Assuming approval of the Stock Issuance Proposal, the Authorized Share Increase Proposal and the Reverse Stock Split Proposal, and successful application for initial listing with Nasdaq, following the consummation of the Merger, the Homology common stock will trade on Nasdaq under Homology’s new name, “Q32 Bio Inc.,” and new trading symbol “QTTB.”

As of         , 2024, the Record Date for the Homology Special Meeting, there were approximately holders of record of the Homology common stock. As of         , 2024, Q32 had holders of record of Q32 common stock and holders of record of Q32 preferred stock. For detailed information regarding the beneficial ownership of certain Homology and Q32 stockholders, see the sections of this proxy statement/prospectus titled “Principal Stockholders of Homology” and “Principal Stockholders of Q32.”

Dividends

Homology has never declared or paid cash dividends on its capital stock. Q32 has never paid or declared any cash dividends on its capital stock. Q32 intends to retain all available funds and any future earnings for use in the operation of its business and does not anticipate paying any cash dividends on its capital stock in the foreseeable future. Notwithstanding the foregoing, any determination to pay cash dividends subsequent to the Merger will be at the discretion of the combined company’s board of directors and will depend upon a number of factors, including the combined company’s results of operations, financial condition, future prospects, contractual restrictions, restrictions imposed by applicable law and other factors the combined company’s board of directors deems relevant.

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RISK FACTORS

The combined company will be faced with a market environment that cannot be predicted and that involves significant risks, many of which will be beyond its control. In addition to the other information contained in this proxy statement/prospectus, you should carefully consider the material risks described below before deciding how to vote your shares of Homology common stock. You should also read and consider the other information in this proxy statement/prospectus.

Risks Related to the Merger

The exchange ratio will not be adjusted based on the market price of Homology common stock so the merger consideration at the closing may have a greater or lesser value than at the time the Merger Agreement was signed.

At the Effective Time, outstanding shares of Q32 common stock (after giving effect to the conversion of each share of Q32’s preferred stock into Q32 common stock and the conversion of the Q32 Convertible Notes into Q32 common stock and including all such shares that are converted into Q32 common stock) will be converted into shares of Homology common stock. Immediately after the Merger, Homology securityholders as of immediately prior to the Merger are expected to own approximately 25% of the outstanding shares of the combined company on a fully-diluted basis and former Q32 securityholders (including purchasers in the Pre-Closing Financing) are expected to own approximately 75% of the outstanding shares of the combined company on a fully-diluted basis, subject to certain assumptions, including, but not limited to, Homology’s net cash as of closing being equal to $60.0 million and Q32 issuing $42.0 million of Q32 common stock in the Pre-Closing Financing described elsewhere in this proxy statement/prospectus. Under certain circumstances further described in the Merger Agreement, the ownership percentages may be adjusted up or down including, but not limited to, if Homology’s net cash as of closing is lower than $59.5 million or greater than $60.5 million.

Any changes in the market price of Homology common stock before the completion of the Merger will not affect the number of shares Q32 stockholders will be entitled to receive pursuant to the Merger Agreement. Therefore, if before the completion of the Merger, the market price of Homology common stock increases from the market price on the date of the Merger Agreement, then Q32 stockholders could receive merger consideration with substantially more value for their shares of Q32 common stock than the parties had negotiated when they established the exchange ratio. Similarly, if before the completion of the Merger the market price of Homology common stock declines from the market price on the date of the Merger Agreement, then Q32 stockholders could receive merger consideration with substantially lower value. The Merger Agreement does not include a price-based termination right.

Failure to complete the Merger may result in Homology paying a termination fee to Q32, which could harm the Homology common stock price and future business and operations of Homology.

If the Merger is not completed, Homology is subject to the following risks:

If the Merger Agreement is terminated and the board of directors of Homology determines to seek another business combination, there can be no assurance that Homology will be able to find a partner with whom a business combination would yield greater benefits than the benefits to be provided under the Merger Agreement.

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If the conditions to the Merger are not satisfied or waived, the Merger may not occur.

Even if the Merger is approved by the stockholders of Q32 and the Stock Issuance Proposal is approved by the Homology stockholders, specified conditions must be satisfied or waived to complete the Merger. These conditions are set forth in the Merger Agreement and described in the section titled “The Merger Agreement—Conditions to the Completion of the Merger” in this proxy statement/prospectus. Homology and Q32 cannot assure you that all of the conditions to the consummation of the Merger will be satisfied or waived. If the conditions are not satisfied or waived, the Merger may not occur or the closing may be delayed, and Homology and Q32 each may lose some or all of the intended benefits of the Merger.

The Merger may be completed even though a material adverse effect may result from the announcement of the Merger, industry-wide changes or other causes.

In general, neither Homology nor Q32 is obligated to complete the Merger if there is a material adverse effect affecting the other party between November 16, 2023, the date of the Merger Agreement, and the closing of the Merger. However, certain types of changes are excluded from the concept of a “material adverse effect.” Such exclusions include but are not limited to changes in general economic or political conditions, changes resulting from the announcement of the Merger, natural disasters, pandemics, other force majeure events, acts or threats of terrorism or war and changes in GAAP. Therefore, if any of these events were to occur impacting Homology or Q32, the other party would still be obliged to consummate the closing of the Merger. If any such adverse changes occur and Homology and Q32 consummate the closing of the Merger, the stock price of the combined company may suffer. This in turn may reduce the value of the Merger to the stockholders of Homology, Q32 or both. For a more complete discussion of what constitutes a material adverse effect on Homology or Q32, see the section titled “The Merger Agreement—Representations and Warranties” in this proxy statement/prospectus.

If Homology and Q32 complete the Merger, the combined company will need to raise additional capital by issuing equity securities or additional debt or through licensing arrangements, which may cause significant dilution to the combined company’s stockholders or restrict the combined company’s operations.

Additional financing may not be available to the combined company when it is needed or may not be available on favorable terms. To the extent that the combined company raises additional capital by issuing equity securities, such financing will cause additional dilution to all securityholders of the combined company, including Homology’s pre-Merger stockholders and Q32’s former securityholders. It is also possible that the terms of any new equity securities may have preferences over the combined company’s common stock. Any debt financing the combined company enters into may involve covenants that restrict its operations. These restrictive covenants may include limitations on additional borrowing and specific restrictions on the use of the combined company’s assets, as well as prohibitions on its ability to create liens, pay dividends, redeem its stock or make investments. In addition, if the combined company raises additional funds through licensing arrangements, it may be necessary to grant licenses on terms that are not favorable to the combined company.

Some Homology and Q32 directors and executive officers have interests in the Merger that are different from yours and that may influence them to support or approve the Merger without regard to your interests.

Directors and executive officers of Homology and Q32 may have interests in the Merger that are different from, or in addition to, the interests of other Homology stockholders generally. These interests with respect to Homology’s directors and executive officers may include, among others, acceleration of Homology ITM Options, Homology Restricted Stock Units, transaction bonus payments, severance payments and benefits if employment is terminated in a qualifying termination in connection with the Merger and rights to continued indemnification, expense advancement and insurance coverage. Arthur Tzianabos, Ph.D. and Mary Thistle, current members of the Homology board of directors will continue as directors of the combined company after the Effective Time. Following the Effective Time, it is expected that the combined company will provide

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compensation to non-employee directors pursuant to a new non-employee director compensation policy that is expected to be adopted post-closing. These interests with respect to Q32’s directors and executive officers may include, among others, certain of Q32’s directors and executive officers have options, subject to vesting, to purchase shares of Q32 common stock which, after the Effective Time, will be converted into and become options to purchase shares of the common stock of the combined company; Q32’s executive officers are expected to continue as executive officers of the combined company after the Effective Time; and all of Q32’s directors and executive officers are entitled to certain indemnification and liability insurance coverage pursuant to the terms of the Merger Agreement. Further, certain current members of Q32’s board of directors will continue as directors of the combined company after the Effective Time, and, following the Effective Time, it is expected that the combined company will provide compensation to non-employee directors pursuant to a new non-employee director compensation policy that is expected to be adopted post-closing.

The board of directors of both Homology and Q32 were aware of and considered these interests, among other matters, in reaching their decisions to approve and adopt the Merger Agreement, approve the Merger, approve the issuance of Homology common stock in the Merger, and recommend the approval of the Merger Agreement to Q32 stockholders and the issuance of the Homology common stock to Q32 stockholders in the Merger to the Homology stockholders. These interests, among other factors, may have influenced the directors and executive officers of Homology and Q32 to support or approve the Merger.

For more information regarding the interests of Homology and Q32 directors and executive officers in the Merger, please see the sections titled “The Merger—Interests of Homology Directors and Executive Officers in the Merger” and “The Merger—Interests of Q32 Directors and Executive Officers in the Merger” in this proxy statement/prospectus.

Homology stockholders may not realize a benefit from the Merger commensurate with the ownership dilution they will experience in connection with the Merger.

If the combined company is unable to realize the full strategic and financial benefits currently anticipated from the Merger, Homology stockholders will have experienced substantial dilution of their ownership interests without receiving any commensurate benefit, or only receiving part of the commensurate benefit to the extent the combined company is able to realize only part of the strategic and financial benefits currently anticipated from the Merger.

If the Merger is not completed, Homology’s stock price may decline significantly.

The market price of Homology common stock is subject to significant fluctuations. During the 12-month period ended September 30, 2023, the closing sales price of Homology common stock on Nasdaq ranged from a high of $2.04 on November 16, 2022 to a low of $ 0.83 on June 28, 2023. Market prices for securities of pharmaceutical, biotechnology and other life science companies have historically been particularly volatile. In addition, the market price of Homology common stock will likely be volatile based on whether stockholders and other investors believe that Homology can complete the Merger or otherwise raise additional capital to support Homology’s operations if the Merger is not consummated and another strategic transaction cannot be identified, negotiated and consummated in a timely manner, if at all. The volatility of the market price of Homology common stock is exacerbated by low trading volume. Additional factors that may cause the market price of Homology common stock to fluctuate include:

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See also “Risks related to Homology common stock—The market price of Homology common stock has been volatile and fluctuated and may in future fluctuate substantially, which could result in substantial losses for Homology’s stockholders”. Moreover, the stock markets in general have experienced substantial volatility that has often been unrelated to the operating performance of individual companies. These broad market fluctuations may also adversely affect the trading price of Homology common stock. In the past, following periods of volatility in the market price of a company’s securities, stockholders have often instituted class action securities litigation against such companies.

Homology and Q32 securityholders will have a reduced ownership and voting interest in, and will exercise less influence over the management of, the combined company following the completion of the Merger as compared to their current ownership and voting interests in the respective companies.

After the completion of the Merger, the current stockholders of Homology and Q32 will own a smaller percentage of the combined company than their ownership of their respective companies prior to the Merger. Immediately after the Merger, Homology securityholders as of immediately prior to the Merger are expected to own approximately 25% of the outstanding shares of the combined company on a fully-diluted basis and former Q32 securityholders (including purchasers in the Pre-Closing Financing) are expected to own approximately 75% of the outstanding shares of the combined company on a fully-diluted basis, subject to certain assumptions, including, but not limited to, Homology’s net cash as of closing being equal to $60.0 million and Q32 issuing approximately $42.0 million of Q32 common stock in the Pre-Closing Financing described elsewhere in this proxy statement/prospectus. Under certain circumstances further described in the Merger Agreement, the ownership percentages may be adjusted up or down including, but not limited to, if Homology’s net cash as of closing is lower than $59.5 million or greater than $60.5 million.

During the pendency of the Merger, Homology and Q32 may not be able to enter into a business combination with another party on more favorable terms because of restrictions in the Merger Agreement, which could adversely affect their respective business prospects.

Covenants in the Merger Agreement impede the ability of Homology and Q32 to make acquisitions during the pendency of the Merger, subject to specified exceptions. As a result, if the Merger is not completed, the parties may be at a disadvantage to their competitors during that period. In addition, while the Merger Agreement is in effect, each party is generally prohibited from soliciting, proposing, seeking or knowingly encouraging, facilitating or supporting any inquiries, indications of interest, proposals or offers that constitute or may reasonably be expected to lead to certain transactions involving a third party, including a merger, sale of assets or other business combination, subject to specified exceptions. Any such transactions could be favorable to such party’s stockholders, but the parties may be unable to pursue them. For more information, see the section titled “The Merger Agreement—Non-Solicitation” this proxy statement/prospectus.

Certain provisions of the Merger Agreement may discourage third parties from submitting competing proposals, including proposals that may be superior to the transactions contemplated by the Merger Agreement.

The terms of the Merger Agreement prohibit each of Homology and Q32 from soliciting competing proposals or cooperating with persons making unsolicited takeover proposals, except in limited circumstances as described in further detail in the section titled “The Merger Agreement—Non-Solicitation” in this proxy statement/prospectus. In addition, if Homology terminates the Merger Agreement under specified circumstances, Homology may be required to pay Q32 a termination fee of $2.4 million. This termination fee may discourage third parties from submitting competing proposals to Homology or its stockholders, and may cause the Homology board of directors to be less inclined to recommend a competing proposal.

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Because the lack of a public market for Q32’s stock makes it difficult to evaluate the fair market value of Q32’s stock, Homology may pay more than the fair market value of Q32’s stock and/or the stockholders of Q32 may receive consideration in the Merger that is less than the fair market value of Q32’s stock.

The outstanding Q32 common stock is privately held and is not traded in any public market. The lack of a public market makes it difficult to determine the fair market value of Q32’s stock. Because the percentage of Homology equity to be issued to Q32 stockholders was determined based on negotiations between the parties, it is possible that the value of the Homology common stock to be received by Q32 stockholders will be less than the fair market value of Q32’s stock, or Homology may pay more than the aggregate fair market value for Q32’s stock.

Homology stockholders may not receive any payment on the CVRs, and the CVRs may expire valueless.

The right of Homology stockholders to receive any future payment on or derive any value from the CVRs will be contingent solely upon the occurrence of the Legacy Asset Dispositions within the time periods specified in the CVR Agreement and the consideration received being greater than the amounts permitted to be withheld or deducted by Homology under the CVR Agreement. There is no guarantee that Homology will be able to successfully collaborate or sell any of these assets or establish a viable entity to manage the development of these assets. In the event that no Legacy Asset Dispositions occur within the time periods specified in the CVR Agreement, no payments will be made under the CVR Agreement, and the CVRs will expire valueless.

Furthermore, the CVRs will be unsecured obligations of the combined company and all payments under the CVRs, all other obligations under the CVR Agreement and the CVRs and any rights or claims relating thereto may be subordinated in right of payment to the prior payment in full of all current or future senior obligations of the combined company.

The tax treatment of the CVRs is unclear.

The U.S. federal income tax treatment of the CVRs is unclear. There is no legal authority directly addressing the U.S. federal income tax treatment of the receipt of, holding of or payments under, the CVRs, and there can be no assurance that the IRS would not assert, or that a court would not sustain, a position that could result in adverse U.S. federal income tax consequences to holders of the CVRs.

For example, as discussed in the section titled “Agreements Related to the Merger—Contingent Value Rights Agreement—Material U.S. Federal Income Tax Consequences of the CVRs to Holders of Homology Common Stock” in this proxy statement/prospectus, Homology does not intend to report the issuance of the CVRs as a current distribution of property with respect to its stock, but it is possible that the IRS could assert that Homology stockholders are treated as having received a distribution of property equal to the fair market value of the CVRs on the date the CVRs are distributed, which could be taxable to Homology stockholders without the corresponding receipt of cash. In addition, it is possible that the IRS or a court could determine that the issuance of the CVRs (and/or any payments thereon) and the Reverse Stock Split constitute a single “recapitalization” for U.S. federal income tax purposes with the CVRs constituting taxable “boot” received in such recapitalization exchange. In such case, the tax consequences of the CVRs and the Reverse Stock Split would differ from those described in this proxy statement/prospectus, including with respect to the timing and character of income.

Risks Related to the Proposed Reverse Stock Split

The Reverse Stock Split may not increase the combined company’s stock price over the long-term.

The principal purpose of the Reverse Stock Split is to (i) increase the per-share market price of Homology common stock above the minimum bid price requirement under the Nasdaq rules so that Homology can maintain its listing on Nasdaq and (ii) increase the number of theorized and unissued shares available for future issuance in connection with the merger. It cannot be assured, however, that the Reverse Stock Split will accomplish this objective for any meaningful period of time. While it is expected that the reduction in the number of outstanding shares of

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common stock will proportionally increase the market price of Homology common stock, it cannot be assured that the Reverse Stock Split will increase the market price of its common stock by enough to maintain the listing of Homology common stock on Nasdaq, or result in any permanent or sustained increase in the market price of Homology common stock, which is dependent upon many factors, including Homology’s business and financial performance, general market conditions, and prospects for future success. Thus, while the stock price of Homology might meet the continued listing requirements for Nasdaq initially, it cannot be assured that it will continue to do so.

The Reverse Stock Split may decrease the liquidity of the combined company’s common stock.

Although the Homology board of directors believes that the anticipated increase in the market price of the combined company’s common stock resulting from the proposed Reverse Stock Split could encourage interest in its common stock and possibly promote greater liquidity for its stockholders, such liquidity could also be adversely affected by the reduced number of shares outstanding after the Reverse Stock Split. The reduction in the number of outstanding shares may lead to reduced trading and a smaller number of market makers for the combined company’s common stock. In addition, the Reverse Stock Split may not result in an increase in the combined company’s stock price necessary to satisfy Nasdaq’s initial listing requirements for the combined company.

The Reverse Stock Split may lead to a decrease in the combined company’s overall market capitalization.

Should the market price of the combined company’s common stock decline after the Reverse Stock Split, the percentage decline may be greater, due to the smaller number of shares outstanding, than it would have been prior to the Reverse Stock Split. A Reverse Stock Split is often viewed negatively by the market and, consequently, can lead to a decrease in the combined company’s overall market capitalization. If the per share market price does not increase in proportion to the Reverse Stock Split ratio, then the value of the combined company, as measured by its stock capitalization, will be reduced. In some cases, the per-share stock price of companies that have effected reverse stock splits subsequently declined back to pre-reverse split levels, and accordingly, it cannot be assured that the total market value of the combined company’s common stock will remain the same after the Reverse Stock Split is effected, or that the Reverse Stock Split will not have an adverse effect on the combined company’s stock price due to the reduced number of shares outstanding after the Reverse Stock Split.

Risks Related to the Combined Company

Following completion of the Merger, the combined company will be susceptible to many of the risks described in the sections titled “Risks Related to Homology’s Business” and “Risks Related to Q32’s Business” in this proxy statement/prospectus. To the extent any of the events in the risks described in those sections occur, the potential benefits of the Merger may not be realized and the results of operations and financial condition of the combined company could be adversely affected in a material way. This could cause the market price of the combined company’s common stock to decline.

The market price of the combined company’s common stock is expected to be volatile, and the market price of the common stock may drop following the Merger.

The market price of the combined company’s common stock following the Merger could be subject to significant fluctuations. Some of the factors that may cause the market price of the combined company’s common stock to fluctuate include:

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Moreover, the stock markets in general have experienced substantial volatility that has often been unrelated to the operating performance of individual companies. These broad market fluctuations may also adversely affect the trading price of the combined company’s common stock. In addition, a recession, depression or other sustained adverse market event could materially and adversely affect the combined company’s business and the value of its common stock. In the past, following periods of volatility in the market price of a company’s securities, stockholders have often instituted class action securities litigation against such companies. Furthermore, market volatility may lead to increased shareholder activism if the combined company experiences a market valuation that activists believe is not reflective of its intrinsic value. Activist campaigns that contest or conflict with the combined company’s strategic direction or seek changes in the composition of its board of directors could have an adverse effect on its operating results, financial condition and cash flows.

The combined company may incur losses for the foreseeable future and might never achieve profitability.

The combined company may never become profitable, even if the combined company is able to complete clinical development for one or more product candidates and eventually commercialize such product candidates. The combined company will need to successfully complete significant research, development, testing and regulatory compliance activities that, together with projected general and administrative expenses, is expected to result in substantial increased operating losses for at least the next several years. Even if the combined company does achieve profitability, it may not be able to sustain or increase profitability on a quarterly or annual basis.

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Following the Merger, the combined company may be unable to integrate successfully the businesses of Homology and Q32 and realize the anticipated benefits of the Merger.

The Merger involves the combination of two companies that currently operate as independent companies. Following the Merger, the combined company will be required to devote significant management attention and resources to integrating its business practices and operations. The combined company may fail to realize some or all of the anticipated benefits of the Merger if the integration process takes longer than expected or is more costly than expected. Potential difficulties the combined company may encounter in the integration process include the following:

In addition, Homology and Q32 have operated and, until the completion of the Merger, will continue to operate, independently. It is possible that the integration process also could result in the diversion of each company’s management’s attention, the disruption or interruption of, or the loss of momentum in, each company’s ongoing businesses or inconsistencies in standards, controls, procedures and policies, any of which could adversely affect the combined company’s ability to maintain its business relationships or the ability to achieve the anticipated benefits of the Merger, or could otherwise adversely affect the business and financial results of the combined company.

If the combined company fails to attract and retain management and other key personnel, it may be unable to continue to successfully develop or commercialize its product candidates or otherwise implement its business plan.

The combined company’s ability to compete in the highly competitive pharmaceuticals industry depends on its ability to attract and retain highly qualified managerial, scientific, medical, legal, sales and marketing and other personnel. The combined company will be highly dependent on its management and scientific personnel. The loss of the services of any of these individuals could impede, delay, or prevent the successful development of the combined company’s product pipeline, completion of its planned clinical trials, commercialization of its product candidates or in-licensing or acquisition of new assets and could impact negatively its ability to implement successfully its business plan. If the combined company loses the services of any of these individuals, it might not be able to find suitable replacements on a timely basis or at all, and its business could be harmed as a result. The combined company might not be able to attract or retain qualified management and other key personnel in the future due to the intense competition for qualified personnel among biotechnology, pharmaceutical and other businesses.

The combined company will need to raise additional financing in the future to fund its operations, which may not be available to it on favorable terms or at all.

The combined company will require substantial additional funds to conduct the costly and time-consuming clinical efficacy trials necessary to pursue regulatory approval of each potential product candidate. The combined company’s future capital requirements will depend upon a number of factors, including: the number and timing of future product candidates in the pipeline; progress with and results from preclinical testing and clinical trials; the ability to manufacture sufficient drug supplies to complete preclinical and clinical trials; the costs involved in preparing, filing, acquiring, prosecuting, maintaining and enforcing patent and other intellectual property claims; and the time and costs involved in obtaining regulatory approvals and favorable reimbursement or formulary

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acceptance. Raising additional capital may be costly or difficult to obtain and could, for example, through the sale of common stock or securities convertible or exchangeable into common stock, significantly dilute its stockholders’ ownership interests or inhibit the combined company’s ability to achieve its business objectives. If the combined company raises additional funds through public or private equity offerings, the terms of these securities may include liquidation or other preferences that adversely affect the rights of its common stockholders. In addition, any debt financing may subject the combined company to fixed payment obligations and covenants limiting or restricting its ability to take specific actions, such as incurring additional debt, making capital expenditures or declaring dividends. If the combined company raises additional capital through marketing and distribution arrangements or other collaborations, strategic alliances or licensing arrangements with third parties, the combined company may have to relinquish certain valuable intellectual property or other rights to its product candidates, technologies, future revenue streams or research programs or grant licenses on terms that may not be favorable to it. Even if the combined company were to obtain sufficient funding, there can be no assurance that it will be available on terms acceptable to the combined company or its stockholders.

The combined company will incur additional costs and increased demands upon management as a result of complying with the laws and regulations affecting public companies.

The combined company will incur significant legal, accounting and other expenses as a public company that Q32 did not incur as a private company, including costs associated with public company reporting obligations under the Exchange Act. The combined company’s management team will consist of the executive officers of Q32 prior to the Merger, some of whom have not previously managed and operated a public company. These executive officers and other personnel will need to devote substantial time to gaining expertise related to public company reporting requirements and compliance with applicable laws and regulations to ensure that the combined company complies with all of these requirements. Any changes the combined company makes to comply with these obligations may not be sufficient to allow it to satisfy its obligations as a public company on a timely basis, or at all. These reporting requirements, rules and regulations, coupled with the increase in potential litigation exposure associated with being a public company, could also make it more difficult for the combined company to attract and retain qualified persons to serve on the board of directors or on board committees or to serve as executive officers, or to obtain certain types of insurance, including directors’ and officers’ insurance, on acceptable terms.

Upon completion of the Merger, failure by the combined company to comply with the initial listing standards of Nasdaq will prevent its stock from being listed on Nasdaq.

Upon completion of the Merger, Homology, under the new name “Q32 Bio Inc.,” will be required to meet the initial listing requirements to maintain the listing and continued trading of its shares on Nasdaq. These initial listing requirements are more difficult to achieve than the continued listing requirements. Pursuant to the Merger Agreement, Homology agreed, to the extent required by the rules and regulations of Nasdaq, to use its commercially reasonable efforts to cause the shares of Homology common stock being issued in the Merger to be approved for listing on Nasdaq at or prior to the Effective Time. Based on information currently available to Homology, Homology anticipates that its stock will be unable to meet the $4.00 (or, to the extent applicable, $3.00) minimum bid price initial listing requirement at the closing of the Merger unless it effects a reverse stock split. The board of directors of Homology intends to effect a reverse stock split of the shares of Homology common stock at a ratio of between 1:    to 1:    . In addition, often times a reverse stock split will not result in a trading price for the affected common stock that is proportional to the ratio of the split. Following the Merger, if the combined company is unable to satisfy Nasdaq listing requirements, Nasdaq may notify the combined company that its shares of common stock will not be listed on Nasdaq.

Upon a potential delisting from Nasdaq, if the common stock of the combined company is not then eligible for quotation on another market or exchange, trading of the shares could be conducted in the over-the-counter market or on an electronic bulletin board established for unlisted securities such as the Pink Sheets or the OTC Bulletin Board. In such event, it is likely that there would be significantly less liquidity in the trading of the common stock of the combined company; decreases in institutional and other investor demand for the shares,

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coverage by securities analysts, market making activity and information available concerning trading prices and volume; and fewer broker dealers willing to execute trades in the common stock of the combined company. Also, it may be difficult for the combined company to raise additional capital if the combined company’s common stock is not listed on a major exchange. The occurrence of any of these events could result in a further decline in the market price of the common stock of the combined company and could have a material adverse effect on the combined company.

Once the combined company is no longer an emerging growth company, a smaller reporting company or otherwise no longer qualifies for applicable exemptions, the combined company will be subject to additional laws and regulations affecting public companies that will increase the combined company’s costs and the demands on management and could harm the combined company’s operating results and cash flows.

The combined company will be subject to the reporting requirements of the Exchange Act, which requires, among other things, that the combined company file with the SEC, annual, quarterly and current reports with respect to the combined company’s business and financial condition as well as other disclosure and corporate governance requirements. However, as an emerging growth company, the combined company may take advantage of exemptions from various requirements such as an exemption from the requirement to have the combined company’s independent auditors attest to the combined company’s internal control over financial reporting under Section 404 of the Sarbanes-Oxley Act of 2002 as well as an exemption from the “say on pay” voting requirements pursuant to the Dodd-Frank Wall Street Reform and Consumer Protection Act of 2010. The combined company also qualifies as a “smaller reporting company,” as such term is defined in Rule 12b-2 under the Exchange Act, which allows the combined company to take advantage of many of the same exemptions from disclosure requirements, including not being required to comply with the auditor attestation requirements of Section 404 of the Sarbanes-Oxley Act and reduced disclosure obligations regarding executive compensation in this proxy statement/prospectus and in the combined company’s periodic reports and proxy statements. Once the combined company is no longer an emerging growth company or a smaller reporting company or otherwise no longer qualifies for these exemptions, the combined company will be required to comply with these additional legal and regulatory requirements applicable to public companies and will incur significant legal, accounting and other expenses to do so. If the combined company is not able to comply with the requirements in a timely manner or at all, the combined company’s financial condition or the market price of the combined company’s common stock may be harmed. For example, if the combined company or its independent auditor identifies deficiencies in the combined company’s internal control over financial reporting that are deemed to be material weaknesses, the combined company could face additional costs to remedy those deficiencies, the market price of the combined company’s stock could decline or the combined company could be subject to sanctions or investigations by the SEC or other regulatory authorities, which would require additional financial and management resources.

If the combined company fails to maintain proper and effective internal controls, its ability to produce accurate financial statements on a timely basis could be impaired.

Provided the combined company continues to be listed on Nasdaq, the combined company will be subject to the reporting requirements of the Exchange Act, the Sarbanes-Oxley Act and the rules and regulations of Nasdaq. The Sarbanes-Oxley Act requires, among other things, that the combined company maintain effective disclosure controls and procedures and internal control over financial reporting. The combined company must perform system and process evaluation and testing of its internal control over financial reporting to allow management to report on the effectiveness of its internal controls over financial reporting in its Annual Report on Form 10-K filing for that year, as required by Section 404 of the Sarbanes-Oxley Act. As a private company, Q32 has never been required to test its internal controls within a specified period. This will require that the combined company incur substantial professional fees and internal costs to expand its accounting and finance functions and that it expends significant management efforts. The combined company may experience difficulty in meeting these reporting requirements in a timely manner.

The combined company may discover weaknesses in its system of internal financial and accounting controls and procedures that could result in a material misstatement of its financial statements. The combined company’s

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internal control over financial reporting will not prevent or detect all errors and all fraud. A control system, no matter how well designed and operated, can provide only reasonable, not absolute, assurance that the control system’s objectives will be met. Because of the inherent limitations in all control systems, no evaluation of controls can provide absolute assurance that misstatements due to error or fraud will not occur or that all control issues and instances of fraud will be detected.

If the combined company is not able to comply with the requirements of Section 404 of the Sarbanes-Oxley Act, or if it is unable to maintain proper and effective internal controls, the combined company may not be able to produce timely and accurate financial statements. If that were to happen, the market price of its common stock could decline and it could be subject to sanctions or investigations by Nasdaq, the SEC or other regulatory authorities.

The unaudited pro forma condensed combined financial information for Homology and Q32 included in this proxy statement/prospectus are preliminary, and the combined company’s actual financial position and operations after the Merger may differ materially from the unaudited pro forma financial information included in this proxy statement/prospectus.

The unaudited pro forma financial information for Homology and Q32 included in this proxy statement/prospectus are presented for illustrative purposes only and is not necessarily indicative of the combined company’s actual financial condition or results of operations of future periods, or the financial condition or results of operations that would have been realized had the entities been combined during the period presented. The combined company’s actual results and financial position after the Merger may differ materially and adversely from the unaudited pro forma financial information included in this proxy statement/prospectus. The exchange ratio formula reflected in this proxy statement/prospectus is preliminary. The final exchange ratio will be determined in accordance with the formula in the Merger Agreement and could differ materially from the preliminary exchange ratio used to prepare the pro forma adjustments. For more information see the section titled “Unaudited Pro Forma Condensed Combined Financial Information”.

Q32 and its independent registered public accounting firm have identified a material weakness in its internal control over financial reporting. If Q32 is unable to remediate this material weakness, or if the combined company identifies additional material weaknesses in the future or otherwise fail to maintain an effective system of internal controls, it may not be able to accurately or timely report its financial condition or results of operations, which may adversely affect its business and the market price of the combined company’s common stock.

In preparation of its consolidated financial statements to meet the requirements applicable to this Merger, Q32 and its independent registered public accounting firm identified a material weakness in its internal control over financial reporting. A material weakness is a deficiency, or a combination of deficiencies, in internal control over financial reporting, such that there is a reasonable possibility that a material misstatement of our annual or interim financial statements will not be prevented or detected on a timely basis.

The material weakness identified related to deficiencies in Q32 controls over complex accounting topics. Specifically, Q32’s accounting and internal control infrastructure did not allow for adequate review processes over complex accounting topics due to lack of sufficient personnel. Due to this material weakness, material errors were identified and corrected in Q32 unaudited condensed consolidated financial statements for the nine months ended September 30, 2023.

Q32 has plans to implement measures designed to improve internal controls over financial reporting to remediate the control deficiencies that led to the material weakness, including strengthening reviews by its finance team, expanding its accounting and finance team to add additional qualified accounting and finance resources, which may include augmenting its finance team with third party consultants that possess the required expertise to assist management with its review.

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Q32 cannot assure you that the measures it has taken to date, and actions it may take in the future, will be sufficient to remediate the control deficiencies that led to the material weakness in its internal control over financial reporting or that they will prevent or avoid potential future material weaknesses. In addition, neither its management nor an independent registered public accounting firm has performed an evaluation of its internal control over financial reporting in accordance with the provisions of the Sarbanes-Oxley Act because no such evaluation has been required. Had Q32 or its independent registered public accounting firm performed an evaluation of its internal control over financial reporting in accordance with the provisions of the Sarbanes-Oxley Act, additional material weaknesses may have been identified. If Q32 is unable to successfully remediate its existing or any future material weaknesses in its internal control over financial reporting, or identify any additional material weaknesses in the future, or otherwise fail to maintain an effective system of internal controls, the accuracy and timing of its financial reporting may be adversely affected, it may be unable to maintain compliance with securities law requirements regarding timely filing of periodic reports in addition to applicable stock exchange listing requirements, investors may lose confidence in its financial reporting, and the market price of the combined company’s common stock may decline as a result.

The combined company’s certificate of incorporation and bylaws and provisions under Delaware law could make an acquisition of the combined company more difficult and may prevent attempts by its stockholders to replace or remove its management.

If the Merger is completed, Homology’s amended and restated bylaws and Homology’s restated certificate of incorporation, as amended by the amendments thereto attached to this proxy statement/prospectus as Annex G and, assuming Proposal Nos. 2 and 3 are approved by Homology stockholders at the Homology Special Meeting, will become the combined company’s bylaws and certificate of incorporation. Provisions that will be included in the combined company’s certificate of incorporation and bylaws may discourage, delay or prevent a merger, acquisition or other change in control of the combined company that stockholders may consider favorable, including transactions in which its common stockholders might otherwise receive a premium price for their shares. These provisions could also limit the price that investors might be willing to pay in the future for shares of the combined company’s common stock, thereby depressing the market price of its common stock. In addition, because the combined company’s board of directors will be responsible for appointing the members of the combined company’s management team, these provisions may frustrate or prevent any attempts by the combined company’s stockholders to replace or remove its current management by making it more difficult for stockholders to replace members of the combined company’s board of directors. Among other things, these provisions:

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Moreover, because the combined company will be incorporated in Delaware, it is governed by the provisions of Section 203 of the DGCL, which prohibits stockholders owning in excess of 15% of the outstanding combined company voting stock from merging or combining with the combined company. Although Homology and Q32 believe these provisions collectively will provide for an opportunity to receive higher bids by requiring potential acquirors to negotiate with the combined company’s board of directors, they would apply even if the offer may be considered beneficial by some stockholders. In addition, these provisions may frustrate or prevent any attempts by the combined company’s stockholders to replace or remove then current management by making it more difficult for stockholders to replace members of the board of directors, which is responsible for appointing the members of management.

The certificate of incorporation of the combined company will provide that, unless the combined company consents in writing to the selection of an alternative forum, certain designated courts will be the sole and exclusive forum for certain legal actions between the combined company and its stockholders, which could limit its stockholders’ ability to obtain a favorable judicial forum for disputes with the combined company or its directors, officers, employees or agents.

The certificate of incorporation of the combined company will provide that, unless it consents in writing to an alternative forum, the Court of Chancery of the State of Delaware is the sole and exclusive forum for state law claims for (i) any derivative action or proceeding brought on its behalf, (ii) any action asserting a claim of or based on a breach of a fiduciary duty owed by any of its current or former directors, officers, or other employees to the combined company or its stockholders, (iii) any action asserting a claim arising pursuant to any provision of the DGCL, its charter or its bylaws, or (iv) any action asserting a claim that is governed by the internal affairs doctrine, in each case subject to the Court of Chancery having personal jurisdiction over the indispensable parties named as defendants therein, which for purposes of this risk factor refers to herein as the “Delaware Forum Provision.” The Delaware Forum Provision will not apply to any causes of action arising under the Securities Act and the Exchange Act. The bylaws of the combined company will further provide that, unless it consents in writing to an alternative forum, federal district courts of the United States will be the exclusive forum for resolving any complaint asserting a cause of action arising under the Securities Act, which for purposes of this risk factor is referred to herein as the “Federal Forum Provision.” In addition, the certificate of incorporation and bylaws of the combined company will provide that any person or entity purchasing or otherwise acquiring any interest in shares of its capital stock is deemed to have notice of and consented to the foregoing Delaware Forum Provision and Federal Forum Provision; provided, however, that stockholders cannot and will not be deemed to have waived its compliance with the U.S. federal securities laws and the rules and regulations thereunder.

The Delaware Forum Provision and the Federal Forum Provision may impose additional litigation costs on stockholders of the combined company in pursuing any such claims, particularly if the stockholders do not reside in or near the State of Delaware. Additionally, the forum selection clauses in the bylaws of the combined company may limit its stockholders’ ability to bring a claim in a judicial forum that they find favorable for disputes with the combined company or its directors, officers or employees, which may discourage such lawsuits against the combined company and its directors, officers and employees even though an action, if successful, might benefit its stockholders.

Homology and Q32 do not anticipate that the combined company will pay any cash dividends in the foreseeable future.

The current expectation is that the combined company will retain its future earnings, if any, to fund the growth of the combined company’s business as opposed to paying dividends. As a result, capital appreciation, if any, of the common stock of the combined company will be your sole source of gain, if any, for the foreseeable future.

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An active trading market for the combined company’s common stock may not develop and its stockholders may not be able to resell their shares of common stock for a profit, if at all.

Prior to the Merger, there had been no public market for shares of Q32 capital stock. An active trading market for the combined company’s shares of common stock may never develop or be sustained. If an active market for the combined company’s common stock does not develop or is not sustained, it may be difficult for its stockholders to sell their shares at an attractive price or at all.

Future sales of shares by existing stockholders could cause the combined company’s stock price to decline.

If existing securityholders of Homology and Q32 sell, or indicate an intention to sell, substantial amounts of the combined company’s common stock in the public market after legal restrictions on resale discussed in this proxy statement/prospectus lapse, the trading price of the common stock of the combined company could decline. Based on shares outstanding as of             ,             after giving effect to the estimated exchange ratio, which has been adjusted to reflect the proposed Reverse Stock Split, the Pre-Closing Financing and shares expected to be issued upon completion of the Merger, the combined company is expected to have outstanding a total of approximately shares of common stock immediately following the completion of the Merger. Of the              shares of common stock, approximately              shares will be available for sale in the public market beginning 180 days after the closing of the Merger as a result of the expiration of lock-up agreements between Homology and Q32 on the one hand and certain securityholders of Homology and Q32 on the other hand. All other outstanding shares of common stock, other than shares held by affiliates of the combined company and shares of Homology common stock issued in exchange for shares of Q32 common stock issued in the Pre-Closing Financing will be freely tradable, without restriction, in the public market. In addition, shares of common stock that are subject to outstanding options or warrants of Q32 will become eligible for sale in the public market to the extent permitted by the provisions of various vesting agreements and Rules 144 and 701 under the Securities Act. If these shares are sold, the trading price of the combined company’s common stock could decline.

After completion of the Merger, the combined company’s executive officers, directors and principal stockholders will have the ability to control or significantly influence all matters submitted to the combined company’s stockholders for approval.

Upon the completion of the Merger, and giving effect to the issuance of the Pre-Closing Financing, it is anticipated that the combined company’s executive officers, directors and principal stockholders will, in the aggregate, beneficially own approximately    % of the combined company’s outstanding shares of common stock, subject to certain assumptions, including, but not limited to, Homology’s net cash as of closing being equal to $60.0 million and Q32 issuing approximately $42.0 million of Q32 common stock in the Pre-Closing Financing. As a result, if these stockholders were to choose to act together, they would be able to control or significantly influence all matters submitted to the combined company’s stockholders for approval, as well as the combined company’s management and affairs. For example, these stockholders, if they choose to act together, would control or significantly influence the election of directors and approval of any merger, consolidation or sale of all or substantially all of the combined company’s assets. This concentration of voting power could delay or prevent an acquisition of the combined company on terms that other stockholders may desire.

If equity research analysts do not publish research or reports, or publish unfavorable research or reports, about the combined company, its business or its market, its stock price and trading volume could decline.

The trading market for the combined company’s common stock will be influenced by the research and reports that equity research analysts publish about it and its business. Equity research analysts may elect to not provide research coverage of the combined company’s common stock after the completion of the Merger, and such lack of research coverage may adversely affect the market price of its common stock. In the event it does have equity research analyst coverage, the combined company will not have any control over the analysts or the content and opinions included in their reports. The price of the combined company’s common stock could decline if one or more equity research analysts downgrade its stock or issue other unfavorable commentary or

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research. If one or more equity research analysts ceases coverage of the combined company or fails to publish reports on it regularly, demand for its common stock could decrease, which in turn could cause its stock price or trading volume to decline.

The combined company will have broad discretion in the use of the cash and cash equivalents of the combined company and the proceeds from the Pre-Closing Financing and may invest or spend the proceeds in ways with which you do not agree and in ways that may not increase the value of your investment.

The combined company will have broad discretion over the use of the cash and cash equivalents of the combined company and the proceeds from the Pre-Closing Financing. You may not agree with the combined company’s decisions, and its use of the proceeds may not yield any return on your investment. The combined company’s failure to apply these resources effectively could compromise its ability to pursue its growth strategy and the combined company might not be able to yield a significant return, if any, on its investment of these net proceeds. You will not have the opportunity to influence its decisions on how to use the combined company’s cash resources.

Changes in tax laws or in their implementation or interpretation may adversely affect the combined company’s business and financial condition.

The rules dealing with U.S. federal, state and local income taxation are constantly under review by persons involved in the legislative process and by the Internal Revenue Service and the U.S. Treasury Department. Changes to tax laws (which changes may have retroactive application) could adversely affect the combined company’s business and financial condition. In recent years, many such changes have been made and changes are likely to continue to occur in the future. The combined company cannot predict whether, when, in what form or with what effective dates, tax laws, regulations and rulings may be enacted, promulgated or decided or whether they could increase its tax liability or require changes in the manner in which it operates in order to minimize increases in its tax liability.

The combined company’s ability to use net operating loss carryforwards and other tax attributes may be limited, including as a result of the Merger.

The combined company’s ability to utilize net operating loss carryforwards, or NOLs, and other tax attributes to offset future taxable income or tax liabilities may be limited as a result of ownership changes, including, as discussed below, in connection with the Merger or other transactions. Similar rules may apply under state tax laws. If the combined company earns taxable income, such limitations could result in increased future income tax liability to the combined company, and the combined company’s future cash flows could be adversely affected.

For a more complete discussion of the risks related to the net operating loss carryforwards and certain other tax attributes of Homology and Q32, please see the discussions under “Risk Factors—Risks Related to Homology’s Business—Risks Related to Homology’s Common Stock—Homology’s ability to use net operating losses and research and development credits to offset future taxable income or income tax liabilities may be subject to certain limitations” and “Risk Factors—Risks Related to Q32’s Business—General Risk Factors—Q32’s ability to utilize its net operating loss carryforwards and certain other tax attributes may be limited,” respectively.

Unfavorable global economic conditions could adversely affect the combined company’s business, financial condition, results of operations or cash flows.

The combined company’s results of operations could be adversely affected by general conditions in the global economy and in the global financial markets. A severe or prolonged economic downturn could result in a variety of risks to the combined company’s business, including, weakened demand for the combined company’s product candidates and the combined company’s ability to raise additional capital when needed on acceptable

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terms, if at all. A weak or declining economy could also strain the combined company’s suppliers, possibly resulting in supply disruption. Any of the foregoing could harm the combined company’s business and the combined company cannot anticipate all of the ways in which the current economic climate and financial market conditions could adversely impact its business.

Risks Related to Homology’s Business

Risks Related to Homology’s Financial Position and Need for Additional Capital

Homology has incurred significant losses since inception and anticipates that it will incur continued losses for the foreseeable future. If Homology is unable to achieve and sustain profitability, the market value of its common stock will likely decline. Homology may never achieve or maintain profitability.

Homology is a clinical-stage genetic medicines company with a limited operating history. Since inception, Homology has incurred significant operating losses. Homology’s net loss for the nine months ended September 30, 2023 was $96.8 million. As of September 30, 2023, Homology had an accumulated deficit of approximately $526.0 million. On March 10, 2022, Homology closed its transaction with OXB Solutions and recorded a gain of $131.2 million on the sale of its manufacturing business which resulted in net income of $29.3 million for the nine months ended September 30, 2022 (see Note 5 to Homology’s condensed consolidated financial statements included elsewhere in this proxy statement/prospectus for additional information regarding the OXB Solutions Transaction). In addition, Homology has not commercialized any products and has never generated any revenue from product sales. Homology has historically devoted most of its financial resources to research and development, including its preclinical development activities.

In July 2023, Homology completed a review of its business and its board of directors approved a plan to explore, review and evaluate a range of potential strategic options available to Homology, including, without limitation, an acquisition, merger, reverse merger, sale of assets, strategic partnerships or other transactions. Based on the financing environment and its anticipated clinical development timeline, Homology stopped further development of its programs and reduced its workforce by 86% to significantly reduce its ongoing operating costs as Homology evaluates strategic alternatives.

Homology has incurred and expects to continue to incur costs and expenditures in connection with the process of evaluating its strategic alternatives and will continue to incur costs associated with operating as a public company. The process of continuing to evaluate strategic transactions may be costly, time-consuming and complex, and Homology may incur significant costs related to these processes, such as legal, accounting and advisory fees and expenses and other related charges. A considerable portion of these costs will be incurred regardless of whether any particular course of action is implemented or transaction is completed. Any such expenses will decrease the remaining cash available for use in Homology’s business.

Should Homology resume development of its product candidates, Homology would expect to continue to incur significant additional operating losses for the foreseeable future as it seeks to advance product candidates through preclinical and clinical development, expand its research and development activities, develop new product candidates, complete clinical trials, seek regulatory approval and, if Homology receives U.S. Food and Drug Administration, or FDA, or foreign regulatory authorities approval, commercialize its products. Furthermore, the costs of advancing product candidates into each succeeding clinical phase tend to increase substantially over time. The total costs to advance any of Homology’s product candidates to marketing approval in even a single jurisdiction would be substantial. Because of the numerous risks and uncertainties associated with genetic medicines product development, Homology is unable to accurately predict the timing or amount of increased expenses or when, or if, Homology will be able to begin generating revenue from the commercialization of products or achieve or maintain profitability. Homology’s expenses will also increase substantially if Homology:

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Furthermore, should Homology resume development of its product candidates, its ability to successfully develop, commercialize and license its products and generate product revenue would be subject to substantial additional risks and uncertainties. Each of its programs and product candidates will require additional preclinical and clinical development, potential regulatory approval in multiple jurisdictions, securing manufacturing supply, capacity and expertise, building of a commercial organization, substantial investment and significant marketing efforts before Homology generates any revenue from product sales. These risks are further described under “—Risks Related to Discovery, Development, Clinical Testing, Manufacturing and Regulatory Approval” and “—Risks Related to Commercialization.”

As a result, Homology expects to continue to incur net losses and negative cash flows for the foreseeable future. These net losses and negative cash flows have had, and will continue to have, an adverse effect on its stockholders’ equity and working capital. The amount of Homology’s future net losses will depend, in part, on the rate of future growth of its expenses and its ability to generate revenues. If Homology is unable to develop and commercialize one or more of its product candidates either alone or with collaborators, or if revenues from any product candidate that receives marketing approval are insufficient, Homology will not achieve profitability. Even if Homology does achieve profitability, it may not be able to sustain or increase profitability. If Homology is unable to achieve and then maintain profitability, the value of its equity securities will be materially and adversely affected.

Any financial or strategic option Homology pursues may not be successful.

In July 2023, Homology’s board of directors approved a process to explore, review and evaluate a range of potential strategic options available to Homology, including, without limitation, an acquisition, merger, reverse merger, sale of assets, strategic partnerships or other transactions. The process of continuing to evaluate these strategic options has been and may continue to be costly, time-consuming and complex and Homology may incur significant costs related to this continued evaluation, such as legal, accounting and advisory fees and expenses and other related charges. There can be no assurance that the proposed Merger with Q32 will be completed, and Homology can provide no assurance that any other strategic alternative it may pursue will have a positive impact on its results of operations or financial condition.

Raising additional capital may cause dilution to Homology’s stockholders, restrict its operations or require it to relinquish rights to its technologies or product candidates.

Until such time, if ever, as Homology can generate substantial revenue, it may finance its cash needs through a combination of equity offerings, debt financings, marketing and distribution arrangements and other

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collaborations, strategic alliances and licensing arrangements. As of September 30, 2023, Homology does not have any committed external source of funds. In addition, Homology may seek additional capital due to favorable market conditions or strategic considerations, even if it believes that it has sufficient funds for its current or future operating plans.

To the extent that Homology raises additional capital through the sale of equity or convertible debt securities, including under its effective Registration Statement on Form S-3, the ownership interests of its stockholders will be diluted, and the terms of these securities may include liquidation or other preferences that adversely affect the rights of its common stockholders. Debt financing and preferred equity financing, if available, may involve agreements that include covenants limiting or restricting Homology’s ability to take specific actions, such as incurring additional debt, making capital expenditures or declaring dividends. If Homology raises additional funds through collaborations, strategic alliances or marketing, distribution or licensing arrangements with third parties, it may be required to relinquish valuable rights to its technologies, future revenue streams or product candidates or grant licenses on terms that may not be favorable to it. If Homology is unable to raise additional funds through equity or debt financings when needed, it may be required to delay, limit, reduce or terminate its product development or future commercialization efforts, should it resume development of its product candidates, or grant rights to develop and market product candidates that it would otherwise prefer to develop and market itself.

Homology’s decision to discontinue further program development efforts may not result in the anticipated savings for Homology and may adversely affect its business.

In connection with its decision to pursue strategic alternatives and reduce its ongoing operating expenses, in July 2023 Homology decided to stop further program developments. Based on the anticipated clinical development timeline of HMI-103 and the financing environment, Homology believes this decision to discontinue further program development efforts will significantly reduce its ongoing operating costs. Homology may not realize, in full or in part, the anticipated benefits and savings in operating expenses from this decision due to unforeseen difficulties, delays or other unexpected costs. For instance, this decision to stop further program developments may include higher than expected costs associated with winding down Homology’s clinical programs. Moreover, if Homology is unable to realize the expected cost savings, its financial condition could be adversely affected, and it may be more difficult to complete the proposed Merger with Q32 or any other potential strategic transaction.

Homology will require additional capital to fund its operations, and if Homology fails to obtain necessary financing, it may not be able to continue its operations for more than twelve months after the date the unaudited consolidated financial statements included elsewhere in this proxy statement/prospectus have been issued.

Homology will require additional capital, which it may raise through equity offerings, debt financings, marketing and distribution arrangements and other collaborations, strategic alliances and licensing arrangements or other sources to enable it to complete the development and potential commercialization of its product candidates and any future product candidates should it resume such activities. In addition, Homology may not be able to enter into any collaborations that will generate significant cash. Adequate additional financing may not be available to Homology on acceptable terms, or at all. Homology’s failure to raise capital as and when needed would have a negative effect on its financial condition and its ability to pursue its business strategy. In addition, attempting to secure additional financing may divert the time and attention of Homology’s management from day-to-day activities.

Based upon its current projections, Homology believes that its existing cash, cash equivalents, and short-term investments will enable it to continue to fund its operations for at least one year from the date its unaudited consolidated financial statements for the period ended September 30, 2023 included elsewhere in this proxy statement/prospectus were issued. However, due to considerations of certain qualitative factors, including the

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discontinuation of all clinical trials and research activities, as well as Homology’s significant reduction in force of all but a few custodial employees, Homology’s management has concluded that there is substantial doubt regarding Homology’s ability to continue as a going concern for more than twelve months after the date the unaudited condensed consolidated financial statements included elsewhere in this proxy statement/prospectus have been issued. Beyond that, Homology will need to raise additional capital in order to fund operating expenses and capital expenditure requirements. This estimate is based on assumptions that may prove to be wrong, and Homology could use its available capital resources sooner than it currently expects. In addition, its resource requirements could materially change depending on the outcome of its ongoing strategic alternative review process. As a result, Homology is unable to estimate the exact amount of its working capital requirements. Changing circumstances could cause Homology to consume capital significantly faster than it currently anticipates, and it may need to spend more than currently expected because of circumstances beyond its control. Should Homology resume development of its product candidates, its future funding requirements, both near and long-term, would depend on many factors, including, but not limited to:

Homology maintains the majority of its cash and cash equivalents in accounts with major U.S. and multi-national financial institutions, and Homology’s deposits at these institutions exceed insured limits. Market conditions can impact the viability of these institutions. In the event of failure of any of the financial institutions where Homology maintains its cash and cash equivalents, there can be no assurance that Homology would be able to access uninsured funds in a timely manner or at all. Any inability to access or delay in accessing these funds could adversely affect its business and financial position.

Homology cannot be certain that additional funding will be available on acceptable terms, or at all. For example, the trading prices for Homology’s and other biopharmaceutical companies’ stock have been highly volatile as a result of macroeconomic conditions, developments in the industry and COVID-19. As a result, Homology may face difficulties raising capital through sales of its common stock and any such sales may be on unfavorable terms. If Homology is unable to raise additional capital in sufficient amounts or on terms acceptable to it, it may have to significantly delay, scale back or discontinue the development or commercialization of or product candidates or potentially discontinue operations.

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Homology has a limited operating history and no history of commercializing genetic medicine products, which may make it difficult to evaluate the prospects for its future viability.

Homology was established and began operations in 2015. Homology’s operations to date have been limited to financing and staffing its company, developing its technology and identifying and developing its product candidates. Homology has not yet demonstrated an ability to successfully complete any clinical trials, including large-scale, pivotal clinical trials, obtain marketing approval, manufacture a commercial scale product, or arrange for a third party to do so on its behalf, or conduct sales and marketing activities necessary for successful product commercialization. Typically, it takes about six to ten years to develop a new drug from the time it enters Phase 1 clinical trials to when it is approved for treating patients, but in many cases, it may take longer. Consequently, should Homology resume development of its product candidates, predictions about its future success or viability may not be as accurate as they could be if it had a longer operating history or a history of successfully developing and commercializing genetic medicine products.

In addition, as a business with a limited operating history, Homology may encounter unforeseen expenses, difficulties, complications, delays and other known and unknown factors. Homology will eventually need to transition from a company with a research focus to a company capable of supporting commercial activities. Homology may not be successful in such a transition.

Homology expects its financial condition and operating results may fluctuate significantly from quarter to quarter and year to year due to a variety of factors, many of which are beyond its control. Accordingly, you should not rely upon the results of any particular quarterly or annual period as indications of future operating performance.

Should Homology resume development of its product candidates, Homology would be heavily dependent on the success of its product candidates, and if none of its candidates receives regulatory approval or is not successfully commercialized, its business may be harmed.

Homology has historically invested a significant portion of its efforts and financial resources in the development of its product candidates. Homology’s future success and ability to generate product revenue is substantially dependent on its ability to successfully develop, obtain regulatory approval for and successfully commercialize its product candidates. Homology currently has no products that are approved for commercial sale and may never be able to develop marketable products, and it has stopped development activities. Should Homology resume development of its product candidates, Homology expects that a substantial portion of its efforts and expenditures over the next few years would be devoted to development of these candidates, which would require additional clinical development, management of clinical and manufacturing activities, regulatory approval in multiple jurisdictions, securing manufacturing supply, building of a commercial organization, substantial investment and significant marketing efforts before Homology can generate any revenues from any commercial sales. Accordingly, Homology’s business has historically depended heavily on the successful development, regulatory approval and commercialization of its product candidates, which may never occur. Therefore, Homology cannot be certain that any of its product candidates would be successful in future clinical trials, receive regulatory approval or be successfully commercialized even if Homology receives regulatory approval.

Even if Homology receives approval to market any product candidate from the FDA or other regulatory authorities, Homology cannot be certain that its product candidates will be successfully commercialized, widely accepted in the marketplace or more effective than other commercially available alternatives. Additionally, the research, testing, manufacturing, labeling, approval, sale, marketing and distribution of genetic medicine products are and will remain subject to extensive regulation by the FDA and other regulatory authorities in the United States and other countries that each have differing regulations. Homology is not permitted to market any product candidate in the United States until it receives approval of a Biologics License Application, or BLA from the FDA, or in any foreign countries until it receives the requisite approval from such countries.

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Homology has not submitted a BLA to the FDA or comparable applications to other regulatory authorities and does not expect to be in a position to do so for the foreseeable future.

If any of Homology’s product candidates shows unexpected adverse events or a lack of efficacy in the indications it intends to treat, or if it experiences other regulatory or developmental issues, its development plans and business could be significantly harmed. Further, competitors may be developing products with similar technology and may experience problems with their products that could identify problems that would potentially harm Homology’s business.

Homology may not be successful in its efforts to identify additional product candidates.

Historically, part of Homology’s strategy has involved, and to the extent such activities are resumed in the future may involve, identifying novel product candidates. The process by which Homology identifies product candidates may fail to yield product candidates for clinical development for a number of reasons, including those discussed in these risk factors and also: