Nature of Business and Basis of Presentation	9 Months Ended
Sep. 30, 2018
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”) is a pre-clinical stage biopharmaceutical company dedicated to translating proprietary gene editing and gene therapy technology into novel treatments for patients with rare genetic diseases. The Company was founded in March 2015 as a Delaware corporation. Its principal offices are in Bedford, Massachusetts. Since its inception, the Company has devoted substantially all of its resources to recruiting personnel, developing its technology platform and advancing its pipeline of product candidates, developing 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 risks associated with the successful research, development and clinical manufacturing of its product candidates. The Company’s success is dependent upon its ability to continue to raise additional capital in order to fund ongoing research and development, obtain regulatory approval of its products, successfully commercialize its products, generate revenue, meet its obligations, and, ultimately, attain profitable operations. 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 September 30, 2018, the Company has financed its operations primarily through the public offering of its common stock, the issuance of convertible preferred stock, and with proceeds from its collaboration and license agreement with Novartis (see Note 11). On April 2, 2018, the Company completed an initial public offering (“IPO”) in which the Company issued and sold 10,350,000 shares of its common stock at a public offering price of $16.00 per share, for aggregate gross proceeds of $165.6 million before fees and expenses. The Company expects to incur additional operating losses and negative operating cash flows for the foreseeable future. In connection with the IPO, the Company effected a one-for-5.263 reverse stock split of its issued and outstanding shares of common stock and a proportional adjustment to the conversion ratios for the Company’s Series A and Series B preferred stock. Accordingly, all share and per share amounts for all periods presented in the accompanying financial statements and notes thereto have been retroactively adjusted, where applicable, to reflect this reverse stock split and adjustment of the preferred stock conversion ratios. The reverse stock split became effective on March 16, 2018. Upon the closing of the IPO, all of the outstanding shares of convertible preferred stock automatically converted into 24,168,656 shares of common stock at the applicable conversion ratio then in effect. Subsequent to the closing of the IPO, there were no shares of preferred stock outstanding. Management believes that existing cash, cash equivalents and short-term investments will allow the Company to continue its operations for at least the next two years. In the absence of a significant source of recurring revenue, the continued viability of the Company beyond that point is dependent on its ability to continue to raise additional capital to finance its operations. 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 unaudited condensed consolidated financial statements have been prepared by the Company in conformity with accounting principles generally accepted in the United States of America (“U.S. GAAP”) and pursuant to the rules and regulations of the Securities and Exchange Commission (“SEC”) for interim financial statements. Certain information and footnote disclosures normally included in financial statements prepared in accordance with U.S. GAAP have been condensed or omitted pursuant to such rules and regulations. However, the Company believes that the disclosures are adequate to make the information presented not misleading. These condensed consolidated financial statements should be read in conjunction with the Company’s audited consolidated financial statements and the notes thereto for the year ended December 31, 2017, included in the Company's final prospectus that forms a part of the Company’s Registration Statement on Form S-1 (Reg. No. 333-223409), filed with the SEC pursuant to Rule 424(b)(4) on March 29, 2018. The unaudited interim condensed consolidated financial statements have been prepared on the same basis as the audited consolidated financial statements. In the opinion of management, the accompanying unaudited interim condensed consolidated financial statements contain all adjustments which are necessary for a fair statement of the Company’s financial position as of September 30, 2018, and consolidated results of operations and cash flows for the three and nine months ended September 30, 2018 and 2017, respectively. Such adjustments are of a normal and recurring nature. The results of operations for the three and nine months ended September 30, 2018 are not necessarily indicative of the results of operations that may be expected for the year ending December 31, 2018.

1. NATURE OF BUSINESS AND BASIS OF PRESENTATION

Nature of Business—Homology Medicines, Inc. (the “Company”) is a pre-clinical stage biopharmaceutical company dedicated to translating proprietary gene editing and gene therapy technology into novel treatments for patients with rare genetic diseases. The Company was founded in March 2015 as a Delaware corporation. Its principal offices are in Bedford, Massachusetts.

Since its inception, the Company has devoted substantially all of its resources to recruiting personnel, developing its technology platform and advancing its pipeline of product candidates, developing 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 risks associated with the successful research, development and clinical manufacturing of its product candidates. The Company’s success is dependent upon its ability to continue to raise additional capital in order to fund ongoing research and development, obtain regulatory approval of its products, successfully commercialize its products, generate revenue, meet its obligations, and, ultimately, attain profitable operations.

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 September 30, 2018, the Company has financed its operations primarily through the public offering of its common stock, the issuance of convertible preferred stock, and with proceeds from its collaboration and license agreement with Novartis (see Note 11).

On April 2, 2018, the Company completed an initial public offering (“IPO”) in which the Company issued and sold 10,350,000 shares of its common stock at a public offering price of $16.00 per share, for aggregate gross proceeds of $165.6 million before fees and expenses. The Company expects to incur additional operating losses and negative operating cash flows for the foreseeable future.

In connection with the IPO, the Company effected a one-for-5.263 reverse stock split of its issued and outstanding shares of common stock and a proportional adjustment to the conversion ratios for the Company’s Series A and Series B preferred stock. Accordingly, all share and per share amounts for all periods presented in the accompanying financial statements and notes thereto have been retroactively adjusted, where applicable, to reflect this reverse stock split and adjustment of the preferred stock conversion ratios. The reverse stock split became effective on March 16, 2018.

Upon the closing of the IPO, all of the outstanding shares of convertible preferred stock automatically converted into 24,168,656 shares of common stock at the applicable conversion ratio then in effect. Subsequent to the closing of the IPO, there were no shares of preferred stock outstanding.

Management believes that existing cash, cash equivalents and short-term investments will allow the Company to continue its operations for at least the next two years. In the absence of a significant source of recurring revenue, the continued viability of the Company beyond that point is dependent on its ability to continue to raise additional capital to finance its operations. 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 unaudited condensed consolidated financial statements have been prepared by the Company in conformity with accounting principles generally accepted in the United States of America (“U.S. GAAP”) and pursuant to the rules and regulations of the Securities and Exchange Commission (“SEC”) for interim financial statements. Certain information and footnote disclosures normally included in financial statements prepared in accordance with U.S. GAAP have been condensed or omitted pursuant to such rules and regulations. However, the Company believes that the disclosures are adequate to make the information presented not misleading. These condensed consolidated financial statements should be read in conjunction with the Company’s audited consolidated financial statements and the notes thereto for the year ended December 31, 2017, included in the Company's final prospectus that forms a part of the Company’s Registration Statement on Form S-1 (Reg. No. 333-223409), filed with the SEC pursuant to Rule 424(b)(4) on March 29, 2018.

The unaudited interim condensed consolidated financial statements have been prepared on the same basis as the audited consolidated financial statements. In the opinion of management, the accompanying unaudited interim condensed consolidated financial statements contain all adjustments which are necessary for a fair statement of the Company’s financial position as of September 30, 2018, and consolidated results of operations and cash flows for the three and nine months ended September 30, 2018 and 2017, respectively. Such adjustments are of a normal and recurring nature. The results of operations for the three and nine months ended September 30, 2018 are not necessarily indicative of the results of operations that may be expected for the year ending December 31, 2018.