Nature of Business and Basis of Presentation	12 Months Ended
Dec. 31, 2023
Organization, Consolidation and Presentation of Financial Statements [Abstract]
NATURE OF BUSINESS AND BASIS OF PRESENTATION	1. NATURE OF BUSINESS AND BASIS OF PRESENTATION Nature of Business—Homology Medicines, Inc. (the “Company” or "Homology") is a clinical-stage genetic medicines company historically focused on transforming the lives of patients suffering from rare diseases by addressing the underlying cause of the disease with one-time gene therapy and gene editing treatments. The Company was founded in March 2015 as a Delaware corporation. Its principal offices are in Bedford, Massachusetts. On July 27, 2023, the Company announced that it had completed a review of its business and the Company's Board of Directors had approved a plan to explore, review and evaluate a range of potential strategic options available to the Company, including, without limitation, an acquisition, merger, reverse merger, sale of assets, strategic partnerships or other transactions. Based on the financing environment and the Company's anticipated clinical development timeline for its lead program, HMI-103, the Company also announced that it was stopping further development of its programs and reduced its workforce by 86% in an effort to significantly reduce its ongoing operating costs as it evaluated strategic alternatives. The workforce reduction was substantially completed in the third quarter of 2023 (see Note 9). Agreement and Plan of Merger After a comprehensive review of strategic alternatives, on November 16, 2023, the Company entered into an Agreement and Plan of Merger (the "Merger Agreement"), with Q32 Bio Inc., a Delaware corporation ("Q32"), and Kenobi Merger Sub, Inc., a Delaware corporation and the Company's direct, wholly owned subsidiary ("Merger Sub"), pursuant to which, among other matters, and subject to the satisfaction or waiver of the conditions set forth in the Merger Agreement, Merger Sub will merge with and into Q32, with Q32 continuing as the Company's wholly owned subsidiary and the surviving corporation of the merger (the "Merger"). The Company's future operations are highly dependent on the success of the Merger and there can be no assurance that the Merger will be successfully consummated. If the Merger is completed, the business of Q32 will continue as the business of the combined company. Merger Consideration Subject to the terms and conditions of the Merger Agreement, (i) immediately prior to the effective time of the Merger (the “Effective Time”), all Q32 preferred stock will be converted into Q32 common stock pursuant to the organizational documents of Q32 (the “Q32 Preferred Stock Conversion”), and (ii) at the Effective Time, (a) each outstanding share of Q32 common stock (excluding Q32 common stock issued in the Concurrent Financing, as described below) will be converted into the right to receive a number of shares of the Company’s common stock (“Company Common Stock”), calculated in accordance with the Merger Agreement, (b) each outstanding Q32 stock option and warrant that has not previously been exercised prior to the closing of the Merger will be assumed by the Company and become an option or warrant, as applicable, to purchase a number of shares of Company Common Stock and (c) the Q32 common stock issued in the Concurrent Financing will be converted into the right to receive a number of shares of the Company’s Common Stock calculated in accordance with the Merger Agreement. The shares of Company Common Stock that will be issued to stockholders of Q32 will be calculated using a formula in the Merger Agreement based on the equity value of each of Q32 and the Company. Q32 has been ascribed an aggregate equity value of $195 million and the Company’s equity value is expected to be approximately $80 million subject to adjustment based on the amount of net cash of the Company at closing of the Merger. Concurrent Financing Pursuant to the Merger Agreement, immediately prior to the Effective Time, Q32 will consummate a financing through the sale of its common stock for aggregate gross proceeds of $42 million based on the same aggregate equity value of Q32 used in the Merger (the “Concurrent Financing”). On November 16, 2023, Q32 entered into subscription agreements with certain accredited investors (the “Investors”) for the Concurrent Financing with expected gross proceeds to Q32 of $42 million. In connection with the Concurrent Financing, at the closing of the Merger, Q32 will enter into a registration rights agreement with the Investors providing for the registration under the Securities Act of 1933, as amended (the “Securities Act”) of the shares of common stock sold in the Concurrent Financing. The consummation of the transactions contemplated by the subscription agreements is conditioned on the satisfaction or waiver of the conditions set forth in the Merger Agreement and in the subscription agreements. Shares of Q32 common stock issued pursuant to the Concurrent Financing will be converted into shares of Company Common Stock in the Merger in accordance with the Merger Agreement. Contingent Value Rights Agreement At the Effective Time, if any Legacy Assets (as defined below) have not been disposed of in a Legacy Asset Disposition (as defined below) or if additional consideration may be payable for the Legacy Assets (as defined below) after closing of the Merger, the Company and Equiniti Trust Company, LLC, a New York limited liability company, as the initial rights agent (“Rights Agent”), will enter into a Contingent Value Rights Agreement (the “CVR Agreement”), pursuant to which the Company’s common stockholders of record as of the close of business on the last business day prior to the day on which the Effective Time occurs will receive one contingent value right (each, a “CVR”) for each outstanding share of Company Common Stock held by such stockholder on such date. Each CVR will represent the contractual right to receive payments from the Company upon the actual receipt by the Company or its subsidiaries of certain contingent proceeds derived from any cash consideration that is paid to the Company or its subsidiaries as a result of the sale, transfer, license, assignment or other divestiture, disposition or commercialization of any of the Company’s assets, rights and interests relating to the Company’s HMI-103, HMI-204, Capsids and AAVHSC Platform, including any equity interests held directly or indirectly by the Company in Oxford Biomedica Solutions, LLC or its affiliates (“OXB Solutions”) pursuant to that certain Equity Securities Purchase Agreement, dated as of January 28, 2022, by and between the Company and OXB Solutions (the “Legacy Assets” and such disposition, a “Legacy Asset Disposition”), net of certain tax, 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. There can be no assurance 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 Securities and Exchange Commission (the “SEC”). The CVRs will not have any voting or dividend rights and will not represent any equity or ownership interest in the Company or any of its affiliates. No interest will accrue on any amounts payable in respect of the CVRs. Other Recent Developments On March 9, 2023, the Company filed a Registration Statement on Form S-3 (File No. 333-270414) (the “Shelf”) with the SEC in relation to the registration of up to an aggregate of $250.0 million of its common stock, preferred stock, debt securities, warrants and/or units of any combination thereof for a period up to three years from the date of the filing. The Shelf became effective on March 17, 2023. The Company also simultaneously entered into a sales agreement with Cowen and Company, LLC (“Cowen”), as sales agent, providing for the offering, issuance and sale by the Company of up to an aggregate of $75.0 million of its common stock from time to time in “at-the-market” offerings under the Shelf (the “ATM”). The Company did not sell any shares of common stock under the ATM during the year ended December 31, 2023. As of December 31, 2023, there remained $75.0 million of common stock available for sale under the ATM. On March 10, 2022, the Company closed a transaction with Oxford Biomedica (US) LLC ("OXB (US)"), to establish a new adeno-associated virus ("AAV") vector manufacturing company, Oxford Biomedica (US) LLC ("OXB (US) LLC") that provides AAV vector process development and manufacturing services to biotechnology companies. Under the terms of the agreement, the Company contributed its manufacturing team of 125 employees, manufacturing facility and equipment, manufacturing-related intellectual property and know-how and certain other assets. Oxford paid the Company $130.0 million of upfront cash and invested $50.0 million of cash to fund OXB (US) LLC in exchange for an 80 percent ownership interest, while Homology retained a 20 percent ownership interest in the new company and received a put option on this ownership position (see Note 6). Since its inception and until recently, the Company has devoted substantially all of its resources to recruiting personnel, developing its technology platform and advancing its pipeline of product candidates through discovery, preclinical and clinical trials, developing and implementing manufacturing processes, building out manufacturing and research and development space, and maintaining and building its intellectual property portfolio. The Company is subject to a number of risks similar to those of other companies conducting high-risk, early-stage research and development of product candidates. Principal among these risks are dependency on key individuals and intellectual property, competition from other products and companies, and the technical and regulatory risks associated with the successful research, development and manufacturing of its product candidates. To date, the Company has not generated any revenue from product sales and does not expect to generate any revenue from the sale of product in the foreseeable future. Through December 31, 2023, the Company has financed its operations primarily through public offerings of its common stock, the issuance of convertible preferred stock, and with proceeds from its transaction with Oxford (see Note 6), its collaboration and license agreement with a former collaboration partner and its private placement with Pfizer (see Note 17). During the year ended December 31, 2023, the Company incurred a loss from operations of $101.4 million and as of December 31, 2023, had $542.1 million in accumulated deficit. The Company has incurred and expects to continue to incur costs and expenditures in connection with the process of evaluating strategic alternatives. Though the Company has executed the Merger Agreement with Q32 effective November 16, 2023, there can be no assurance that the Company will be able to successfully consummate the Merger or any other strategic transaction. The process of evaluating strategic options has been and may continue to be costly, time-consuming and complex and the Company may incur significant costs related to this continued evaluation, such as legal, accounting and advisory fees and expenses and other related charges. Based on current projections, management believes that the Company's cash and cash equivalents and short-term investments as of December 31, 2023 will enable the Company to continue its operations for at least one year from the date of this filing. However, due to the consideration of certain qualitative factors, including the discontinuation of all clinical trials and research activities, as well as the Company's workforce reduction of all but a few custodial employees, management has concluded there is substantial doubt regarding the Company's ability to continue as a going concern for more than twelve months from the date that the consolidated financial statements included in this Annual Report on Form 10-K have been issued. These financial statements do not include any adjustments that might result from the outcome of this uncertainty. Should the Company resume the development of product candidates, it would need to obtain substantial additional funding in connection with continuing operations, particularly if the Company were to resume its preclinical activities and clinical trials for its product candidates. There can be no assurance that the Company will be able to obtain sufficient capital to cover its costs on acceptable terms, if at all. Basis of Presentation—The accompanying consolidated financial statements have been prepared in conformity with accounting principles generally accepted in the United States of America (“U.S. GAAP”) and have been prepared on a going concern basis, which contemplates the realization of assets and the satisfaction of liabilities in the normal course of business.

Nature of Business and Basis of Presentation

12 Months Ended

Dec. 31, 2023

Organization, Consolidation and Presentation of Financial Statements [Abstract]

NATURE OF BUSINESS AND BASIS OF PRESENTATION

1. NATURE OF BUSINESS AND BASIS OF PRESENTATION

Nature of Business—Homology Medicines, Inc. (the “Company” or "Homology") is a clinical-stage genetic medicines company historically focused on transforming the lives of patients suffering from rare diseases by addressing the underlying cause of the disease with one-time gene therapy and gene editing treatments. The Company was founded in March 2015 as a Delaware corporation. Its principal offices are in Bedford, Massachusetts.

On July 27, 2023, the Company announced that it had completed a review of its business and the Company's Board of Directors had approved a plan to explore, review and evaluate a range of potential strategic options available to the Company, including, without limitation, an acquisition, merger, reverse merger, sale of assets, strategic partnerships or other transactions. Based on the financing environment and the Company's anticipated clinical development timeline for its lead program, HMI-103, the Company also announced that it was stopping further development of its programs and reduced its workforce by 86% in an effort to significantly reduce its ongoing operating costs as it evaluated strategic alternatives. The workforce reduction was substantially completed in the third quarter of 2023 (see Note 9).

Agreement and Plan of Merger

After a comprehensive review of strategic alternatives, on November 16, 2023, the Company entered into an Agreement and Plan of Merger (the "Merger Agreement"), with Q32 Bio Inc., a Delaware corporation ("Q32"), and Kenobi Merger Sub, Inc., a Delaware corporation and the Company's direct, wholly owned subsidiary ("Merger Sub"), pursuant to which, among other matters, and subject to the satisfaction or waiver of the conditions set forth in the Merger Agreement, Merger Sub will merge with and into Q32, with Q32 continuing as the Company's wholly owned subsidiary and the surviving corporation of the merger (the "Merger"). The Company's future operations are highly dependent on the success of the Merger and there can be no assurance that the Merger will be successfully consummated. If the Merger is completed, the business of Q32 will continue as the business of the combined company.

Merger Consideration

Subject to the terms and conditions of the Merger Agreement, (i) immediately prior to the effective time of the Merger (the “Effective Time”), all Q32 preferred stock will be converted into Q32 common stock pursuant to the organizational documents of Q32 (the “Q32 Preferred Stock Conversion”), and (ii) at the Effective Time, (a) each outstanding share of Q32 common stock (excluding Q32 common stock issued in the Concurrent Financing, as described below) will be converted into the right to receive a number of shares of the Company’s common stock (“Company Common Stock”), calculated in accordance with the Merger Agreement, (b) each outstanding Q32 stock option and warrant that has not previously been exercised prior to the closing of the Merger will be assumed by the Company and become an option or warrant, as applicable, to purchase a number of shares of Company Common Stock and (c) the Q32 common stock issued in the Concurrent Financing will be converted into the right to receive a number of shares of the Company’s Common Stock calculated in accordance with the Merger Agreement. The shares of Company Common Stock that will be issued to stockholders of Q32 will be calculated using a formula in the Merger Agreement based on the equity value of each of Q32 and the Company. Q32 has been ascribed an aggregate equity value of $195 million and the Company’s equity value is expected to be approximately $80 million subject to adjustment based on the amount of net cash of the Company at closing of the Merger.

Concurrent Financing

Pursuant to the Merger Agreement, immediately prior to the Effective Time, Q32 will consummate a financing through the sale of its common stock for aggregate gross proceeds of $42 million based on the same aggregate equity value of Q32 used in the Merger (the “Concurrent Financing”). On November 16, 2023, Q32 entered into subscription agreements with certain accredited investors (the “Investors”) for the Concurrent Financing with expected gross proceeds to Q32 of $42 million. In connection with the Concurrent Financing, at the closing of the Merger, Q32 will enter into a registration rights agreement with the Investors providing for the registration under the Securities Act of 1933, as amended (the “Securities Act”) of the shares of common stock sold in the Concurrent Financing. The consummation of the transactions contemplated by the subscription agreements is conditioned on the satisfaction or waiver of the conditions set forth in the Merger Agreement and in the subscription agreements. Shares of Q32 common stock issued pursuant to the Concurrent Financing will be converted into shares of Company Common Stock in the Merger in accordance with the Merger Agreement.

Contingent Value Rights Agreement

At the Effective Time, if any Legacy Assets (as defined below) have not been disposed of in a Legacy Asset Disposition (as defined below) or if additional consideration may be payable for the Legacy Assets (as defined below) after closing of the Merger, the Company and Equiniti Trust Company, LLC, a New York limited liability company, as the initial rights agent (“Rights Agent”), will enter into a Contingent Value Rights Agreement (the “CVR Agreement”), pursuant to which the Company’s common stockholders of record as of the close of business on the last business day prior to the day on which the Effective Time occurs will receive one contingent value right (each, a “CVR”) for each outstanding share of Company Common Stock held by such stockholder on such date.

Each CVR will represent the contractual right to receive payments from the Company upon the actual receipt by the Company or its subsidiaries of certain contingent proceeds derived from any cash consideration that is paid to the Company or its subsidiaries as a result of the sale, transfer, license, assignment or other divestiture, disposition or commercialization of any of the Company’s assets, rights and interests relating to the Company’s HMI-103, HMI-204, Capsids and AAVHSC Platform, including any equity interests held directly or indirectly by the Company in Oxford Biomedica Solutions, LLC or its affiliates (“OXB Solutions”) pursuant to that certain Equity Securities Purchase Agreement, dated as of January 28, 2022, by and between the Company and OXB Solutions (the “Legacy Assets” and such disposition, a “Legacy Asset Disposition”), net of certain tax, 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. There can be no assurance 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 Securities and Exchange Commission (the “SEC”). The CVRs will not have any voting or dividend rights and will not represent any equity or ownership interest in the Company or any of its affiliates. No interest will accrue on any amounts payable in respect of the CVRs.

Other Recent Developments

On March 9, 2023, the Company filed a Registration Statement on Form S-3 (File No. 333-270414) (the “Shelf”) with the SEC in relation to the registration of up to an aggregate of $250.0 million of its common stock, preferred stock, debt securities, warrants and/or units of any combination thereof for a period up to three years from the date of the filing. The Shelf became effective on March 17, 2023. The Company also simultaneously entered into a sales agreement with Cowen and Company, LLC (“Cowen”), as sales agent, providing for the offering, issuance and sale by the Company of up to an aggregate of $75.0 million of its common stock from time to time in “at-the-market” offerings under the Shelf (the “ATM”). The Company did not sell any shares of common stock under the ATM during the year ended December 31, 2023. As of December 31, 2023, there remained $75.0 million of common stock available for sale under the ATM.

On March 10, 2022, the Company closed a transaction with Oxford Biomedica (US) LLC ("OXB (US)"), to establish a new adeno-associated virus ("AAV") vector manufacturing company, Oxford Biomedica (US) LLC ("OXB (US) LLC") that provides AAV vector process development and manufacturing services to biotechnology companies. Under the terms of the agreement, the Company contributed its manufacturing team of 125 employees, manufacturing facility and equipment, manufacturing-related intellectual property and know-how and certain other assets. Oxford paid the Company $130.0 million of upfront cash and invested $50.0 million of cash to fund OXB (US) LLC in exchange for an 80 percent ownership interest, while Homology retained a 20 percent ownership interest in the new company and received a put option on this ownership position (see Note 6).

Since its inception and until recently, the Company has devoted substantially all of its resources to recruiting personnel, developing its technology platform and advancing its pipeline of product candidates through discovery, preclinical and clinical trials, developing and implementing manufacturing processes, building out manufacturing and research and development space, and maintaining and building its intellectual property portfolio. The Company is subject to a number of risks similar to those of other companies conducting high-risk, early-stage research and development of product candidates. Principal among these risks are dependency on key individuals and intellectual property, competition from other products and companies, and the technical and regulatory risks associated with the successful research, development and manufacturing of its product candidates.

To date, the Company has not generated any revenue from product sales and does not expect to generate any revenue from the sale of product in the foreseeable future. Through December 31, 2023, the Company has financed its operations primarily through public offerings of its common stock, the issuance of convertible preferred stock, and with proceeds from its transaction with Oxford (see Note 6), its collaboration and license agreement with a former collaboration partner and its private

placement with Pfizer (see Note 17). During the year ended December 31, 2023, the Company incurred a loss from operations of $101.4 million and as of December 31, 2023, had $542.1 million in accumulated deficit.

The Company has incurred and expects to continue to incur costs and expenditures in connection with the process of evaluating strategic alternatives. Though the Company has executed the Merger Agreement with Q32 effective November 16, 2023, there can be no assurance that the Company will be able to successfully consummate the Merger or any other strategic transaction. The process of evaluating strategic options has been and may continue to be costly, time-consuming and complex and the Company may incur significant costs related to this continued evaluation, such as legal, accounting and advisory fees and expenses and other related charges.

Based on current projections, management believes that the Company's cash and cash equivalents and short-term investments as of December 31, 2023 will enable the Company to continue its operations for at least one year from the date of this filing. However, due to the consideration of certain qualitative factors, including the discontinuation of all clinical trials and research activities, as well as the Company's workforce reduction of all but a few custodial employees, management has concluded there is substantial doubt regarding the Company's ability to continue as a going concern for more than twelve months from the date that the consolidated financial statements included in this Annual Report on Form 10-K have been issued. These financial statements do not include any adjustments that might result from the outcome of this uncertainty. Should the Company resume the development of product candidates, it would need to obtain substantial additional funding in connection with continuing operations, particularly if the Company were to resume its preclinical activities and clinical trials for its product candidates. There can be no assurance that the Company will be able to obtain sufficient capital to cover its costs on acceptable terms, if at all.

Basis of Presentation—The accompanying consolidated financial statements have been prepared in conformity with accounting principles generally accepted in the United States of America (“U.S. GAAP”) and have been prepared on a going concern basis, which contemplates the realization of assets and the satisfaction of liabilities in the normal course of business.