Organization and Nature of Business	12 Months Ended
Dec. 31, 2020
Organization Consolidation And Presentation Of Financial Statements [Abstract]
Organization and Nature of Business	1. Organization and Nature of the Business Adicet Bio, Inc. (formerly resTORbio, Inc. (resTORbio)), together with its subsidiaries, (the Company) is a biotechnology company discovering and developing allogeneic gamma delta T cell therapies for cancer and other diseases. The Company is advancing a pipeline of off-the-shelf gamma delta T cells, engineered with chimeric antigen receptors (CARs) and T cell receptor-like antibodies to enhance selective tumor targeting, facilitate innate and adaptive anti-tumor immune response, and improve persistence for durable activity in patients. The Company believes its approach has potentially significant advantages over alpha beta T cells, which are the basis of standard CAR-T cell therapies. The Company was incorporated in November 2014 in Delaware. The principal executive offices are located in Boston, Massachusetts. The Company also has another office in Menlo Park, California. Adicet Bio, Inc. (when referred to prior to the Merger (as defined below), (Former Adicet)) was incorporated in November 2014 in Delaware and was headquartered in Menlo Park, CA. Adicet Bio Israel Ltd. (formerly Applied Immune Technologies Ltd.) (Adicet Israel) is a wholly owned subsidiary of Former Adicet and is located in Haifa, Israel. Adicet Israel was founded in 2006. During 2019, Former Adicet consolidated its operations, including research and development activities, in the U.S. and as a result substantially reduced its operations in Israel. Merger with resTORbio Prior to September 15, 2020, the Company was a clinical-stage biopharmaceutical company known as resTORbio that had historically focused on developing innovative medicines that target the biology of aging, to prevent or treat age-related diseases with the potential to extend healthy lifespans. On April 28, 2020, resTORbio entered into a definitive Merger Agreement with Former Adicet. Under the terms of the Merger Agreement, Former Adicet agreed to merge with a wholly owned subsidiary of resTORbio in an all-stock transaction with Former Adicet surviving as a wholly owned subsidiary of resTORbio and changing its name to “Adicet Therapeutics, Inc.” (such transactions, the Merger). Under the exchange ratio formula in the Merger Agreement, immediately following the Effective Time of the Merger, the securityholders of Former Adicet as of immediately prior to the Effective Time of the Merger owned approximately 75% of the outstanding shares of the Company’s common stock on a fully-diluted basis and securityholders of resTORbio as of immediately prior to the Effective Time of the Merger owned approximately 25% of the outstanding shares of the Company’s common stock on a fully-diluted basis (in each case excluding equity incentives available for grant). The Company concluded that the transaction represented a business combination pursuant to Financial Accounting Standards Board (FASB) Accounting Standards Codification (ASC) Topic 805, Business Combinations. Further, Former Adicet was determined to be the accounting acquirer based upon the terms of the Merger and other factors including: (i) Former Adicet’s securityholders own approximately 75% of the voting rights of the combined company (on a fully-diluted basis excluding equity incentives available for grant); (ii) Former Adicet designated a majority (five of seven) of the initial members of the Board of Directors of the combined company; and (iii) the terms of the exchange of equity interests based on the exchange ratio at the announcement of the Merger factored in an implied premium to resTORbio’s stockholders. The composition of senior management of the combined company was determined to be a neutral factor in the accounting acquirer determination, as the combined company will leverage the expertise of the senior management of both companies. Accordingly, the reported operating results prior to the business combination are those of Former Adicet. On September 15, 2020, the Company completed the Merger pursuant to the Merger Agreement (the Effective Time). In connection with the Merger, and immediately prior to the Effective Time, resTORbio effected a reverse stock split of its common stock at a ratio of 1-for-7 (the Reverse Stock Split). Also, in connection with the Merger, the Company changed its name from “resTORbio, Inc.” to “Adicet Bio, Inc.” (the Name Change), Former Adicet changed its name from “Adicet Bio, Inc.” to “Adicet Therapeutics, Inc.” and the business conducted by the Company became primarily the business, which was previously conducted by Former Adicet, which is a biotechnology company discovering and developing allogeneic gamma delta T cell therapies for cancer and other diseases. At the Effective Time, each outstanding share of Former Adicet capital stock was converted into the right to receive 0.1240 (the Exchange Ratio) shares of Company’s common stock, as set forth in the Merger Agreement. The Exchange Ratio was determined based on the total number of outstanding shares of Company’s common stock and Former Adicet capital stock, each on a fully diluted basis, and the respective valuations of Former Adicet and resTORbio at the time of execution of the Merger Agreement. In connection with the Merger, the Company also assumed certain outstanding Former Adicet warrants and Former Adicet stock options under Former Adicet’s 2015 Stock Incentive Plan (the 2015 Adicet Stock Incentive Plan) and Former Adicet’s 2014 Share Option Plan (the 2014 Share Option Plan and, together with the 2015 Adicet Stock Incentive Plan, the Former Adicet Plans), with such stock options and warrants henceforth representing the right to purchase a number of shares of Company’s common stock equal to the Exchange Ratio multiplied by the number of shares of Former Adicet’s capital stock previously represented by such stock options and warrants, as applicable, with a proportionate adjustment in exercise price. Immediately following the Effective Time, there were approximately 19,589,828 shares of the Company’s common stock outstanding (post Reverse Stock Split), with the former equity holders of Former Adicet holding approximately 75% of the outstanding shares of Company’s common stock on a fully-diluted basis and the former equity holders of resTORbio holding approximately 25% of the outstanding shares of Company’s common stock on a fully-diluted basis (in each case excluding equity incentives available for grant). Please refer to Note 3 “Business Combinations” for further discussions of the Merger. Liquidity and Going Concern The Company has incurred significant net operating losses and negative cash flows from operations since inception and had an accumulated deficit of $106.5 million as of December 31, 2020. The Company has historically financed its operations primarily through a collaboration and licensing arrangement, the private placement of equity securities and debt, and cash received in the Merger. To date, none of the Company’s product candidates have been approved for sale and therefore the Company has not generated any revenue from product sales. Management expects operating losses and negative cash flows to continue for the foreseeable future, until such time, if ever, that it can generate significant sales of its product candidates currently in development. As of June 23, 2020, the issuance date of the Company’s consolidated financial statements for the year ended December 31, 2019, the Company had concluded that there was substantial doubt about its ability to continue as a going concern. As of December 31, 2020, the Company had $94.6 million in cash, cash equivalents, and marketable debt securities. In February 2021, the Company completed an underwritten public offering of 10,575,513 shares of its common stock, including the exercise in full by the underwriters of their option to purchase up to an additional 1,344,743 shares of common stock at a public offering price of $13.00 per share. The company received aggregate gross proceeds from the offering, before deducting underwriting discounts and commissions and offering expenses of approximately $137.5 million. In connection with the offering, the Company also entered into a stock purchase agreement with certain existing investors for $15.0 million of shares of the Company’s common stock at a price per share equal to the public offering price, with an initial closing for certain investors held simultaneously with the closing of the offering and a subsequent closing for certain additional investors. These two recent events have alleviated the substantial doubt about the Company’s ability to continue as a going concern. The Company expects that its cash, cash equivalents and marketable debt securities, including the gross proceeds it received in February 2021 from its underwritten public offering and the proceeds received from a stock purchase agreement with certain existing investors, will be sufficient to fund its forecasted operating expenses, capital expenditure requirements and debt service payments for at least the next twelve months from the issuance of these annual consolidated financial statements. All of the Company’s revenue to date is generated from the Regeneron Agreement, which is a collaboration and license agreement with Regeneron Pharmaceuticals, Inc. (Regeneron). The Company does not expect to generate any significant product revenue until it obtains regulatory approval of and commercialize any of the Company’s product candidates or enter into additional collaborative agreements with third parties, and it does not know when, or if, either will occur. The Company expects to continue to incur significant losses for the foreseeable future, and it expects the losses to increase as the Company continues the development of, and seek regulatory approvals for, its product candidates and begin to commercialize any approved products. The Company is subject to all of the risks typically related to the development of new product candidates, including, but not limited to, raising additional capital, development by its competitors of new technological innovations, risk of failure in preclinical and clinical studies, safety and efficacy of its product candidates in clinical trials, the risk of relying on external parties such as contract research organizations (CROs) and contract manufacturing organizations (CMOs), the regulatory approval process, market acceptance of the Company’s products once approved, lack of marketing and sales history, dependence on key personnel and protection of proprietary technology and it may encounter unforeseen expenses, difficulties, complications, delays, and other unknown factors that may adversely affect its business. Until such time as the Company can generate significant revenue from product sales, if ever, the Company expects to finance its operations through the sale of equity, debt financings, collaborative or other arrangements with corporate or other sources of financing. Adequate funding may not be available to the Company on acceptable terms or at all. The Company’s failure to raise capital as and when needed could have a negative impact on its financial condition and the Company’s ability to pursue its business strategies. Although the Company continues to pursue these plans, there is no assurance that the Company will be successful in obtaining sufficient funding on terms acceptable to the Company to fund continuing operations, if at all.

Organization and Nature of Business

12 Months Ended

Dec. 31, 2020

Organization Consolidation And Presentation Of Financial Statements [Abstract]

1. Organization and Nature of the Business

Adicet Bio, Inc. (formerly resTORbio, Inc. (resTORbio)), together with its subsidiaries, (the Company) is a biotechnology company discovering and developing allogeneic gamma delta T cell therapies for cancer and other diseases. The Company is advancing a pipeline of off-the-shelf gamma delta T cells, engineered with chimeric antigen receptors (CARs) and T cell receptor-like antibodies to enhance selective tumor targeting, facilitate innate and adaptive anti-tumor immune response, and improve persistence for durable activity in patients. The Company believes its approach has potentially significant advantages over alpha beta T cells, which are the basis of standard CAR-T cell therapies. The Company was incorporated in November 2014 in Delaware. The principal executive offices are located in Boston, Massachusetts. The Company also has another office in Menlo Park, California.

Adicet Bio, Inc. (when referred to prior to the Merger (as defined below), (Former Adicet)) was incorporated in November 2014 in Delaware and was headquartered in Menlo Park, CA. Adicet Bio Israel Ltd. (formerly Applied Immune Technologies Ltd.) (Adicet Israel) is a wholly owned subsidiary of Former Adicet and is located in Haifa, Israel. Adicet Israel was founded in 2006. During 2019, Former Adicet consolidated its operations, including research and development activities, in the U.S. and as a result substantially reduced its operations in Israel.

Merger with resTORbio

Prior to September 15, 2020, the Company was a clinical-stage biopharmaceutical company known as resTORbio that had historically focused on developing innovative medicines that target the biology of aging, to prevent or treat age-related diseases with the potential to extend healthy lifespans. On April 28, 2020, resTORbio entered into a definitive Merger Agreement with Former Adicet. Under the terms of the Merger Agreement, Former Adicet agreed to merge with a wholly owned subsidiary of resTORbio in an all-stock transaction with Former Adicet surviving as a wholly owned subsidiary of resTORbio and changing its name to “Adicet Therapeutics, Inc.” (such transactions, the Merger). Under the exchange ratio formula in the Merger Agreement, immediately following the Effective Time of the Merger, the securityholders of Former Adicet as of immediately prior to the Effective Time of the Merger owned approximately 75% of the outstanding shares of the Company’s common stock on a fully-diluted basis and securityholders of resTORbio as of immediately prior to the Effective Time of the Merger owned approximately 25% of the outstanding shares of the Company’s common stock on a fully-diluted basis (in each case excluding equity incentives available for grant).

The Company concluded that the transaction represented a business combination pursuant to Financial Accounting Standards Board (FASB) Accounting Standards Codification (ASC) Topic 805, Business Combinations. Further, Former Adicet was determined to be the accounting acquirer based upon the terms of the Merger and other factors including: (i) Former Adicet’s securityholders own approximately 75% of the voting rights of the combined company (on a fully-diluted basis excluding equity incentives available for grant); (ii) Former Adicet designated a majority (five of seven) of the initial members of the Board of Directors of the combined company; and (iii) the terms of the exchange of equity interests based on the exchange ratio at the announcement of the Merger factored in an implied premium to resTORbio’s stockholders. The composition of senior management of the combined company was determined to be a neutral factor in the accounting acquirer determination, as the combined company will leverage the expertise of the senior management of both companies. Accordingly, the reported operating results prior to the business combination are those of Former Adicet.

On September 15, 2020, the Company completed the Merger pursuant to the Merger Agreement (the Effective Time). In connection with the Merger, and immediately prior to the Effective Time, resTORbio effected a reverse stock split of its common stock at a ratio of 1-for-7 (the Reverse Stock Split). Also, in connection with the Merger, the Company changed its name from “resTORbio, Inc.” to “Adicet Bio, Inc.” (the Name Change), Former Adicet changed its name from “Adicet Bio, Inc.” to “Adicet Therapeutics, Inc.” and the business conducted by the Company became primarily the business, which was previously conducted by Former Adicet, which is a biotechnology company discovering and developing allogeneic gamma delta T cell therapies for cancer and other diseases.

At the Effective Time, each outstanding share of Former Adicet capital stock was converted into the right to receive 0.1240 (the Exchange Ratio) shares of Company’s common stock, as set forth in the Merger Agreement. The Exchange Ratio was determined based on the total number of outstanding shares of Company’s common stock and Former Adicet capital stock, each on a fully diluted basis, and the respective valuations of Former Adicet and resTORbio at the time of execution of the Merger Agreement. In connection with the Merger, the Company also assumed certain outstanding Former Adicet warrants and Former Adicet stock options under Former Adicet’s 2015 Stock Incentive Plan (the 2015 Adicet Stock Incentive Plan) and Former Adicet’s 2014 Share Option Plan (the 2014 Share Option Plan and, together with the 2015 Adicet Stock Incentive Plan, the Former Adicet Plans), with such stock options and warrants henceforth representing the right to purchase a number of shares of Company’s common stock equal to the Exchange Ratio multiplied by the number of shares of Former Adicet’s capital stock previously represented by such stock options and warrants, as applicable, with a proportionate adjustment in exercise price.

Immediately following the Effective Time, there were approximately 19,589,828 shares of the Company’s common stock outstanding (post Reverse Stock Split), with the former equity holders of Former Adicet holding approximately 75% of the outstanding shares of Company’s common stock on a fully-diluted basis and the former equity holders of resTORbio holding approximately 25% of the outstanding shares of Company’s common stock on a fully-diluted basis (in each case excluding equity incentives available for grant).

Please refer to Note 3 “Business Combinations” for further discussions of the Merger.

Liquidity and Going Concern

The Company has incurred significant net operating losses and negative cash flows from operations since inception and had an accumulated deficit of $106.5 million as of December 31, 2020. The Company has historically financed its operations primarily through a collaboration and licensing arrangement, the private placement of equity securities and debt, and cash received in the Merger. To date, none of the Company’s product candidates have been approved for sale and therefore the Company has not generated any revenue from product sales. Management expects operating losses and negative cash flows to continue for the foreseeable future, until such time, if ever, that it can generate significant sales of its product candidates currently in development.

As of June 23, 2020, the issuance date of the Company’s consolidated financial statements for the year ended December 31, 2019, the Company had concluded that there was substantial doubt about its ability to continue as a going concern. As of December 31, 2020, the Company had $94.6 million in cash, cash equivalents, and marketable debt securities. In February 2021, the Company completed an underwritten public offering of 10,575,513 shares of its common stock, including the exercise in full by the underwriters of their option to purchase up to an additional 1,344,743 shares of common stock at a public offering price of $13.00 per share. The company received aggregate gross proceeds from the offering, before deducting underwriting discounts and commissions and offering expenses of approximately $137.5 million. In connection with the offering, the Company also entered into a stock purchase agreement with certain existing investors for $15.0 million of shares of the Company’s common stock at a price per share equal to the public offering price, with an initial closing for certain investors held simultaneously with the closing of the offering and a subsequent closing for certain additional investors. These two recent events have alleviated the substantial doubt about the Company’s ability to continue as a going concern. The Company expects that its cash, cash equivalents and marketable debt securities, including the gross proceeds it received in February 2021 from its underwritten public offering and the proceeds received from a stock purchase agreement with certain existing investors, will be sufficient to fund its forecasted operating expenses, capital expenditure requirements and debt service payments for at least the next twelve months from the issuance of these annual consolidated financial statements.

All of the Company’s revenue to date is generated from the Regeneron Agreement, which is a collaboration and license agreement with Regeneron Pharmaceuticals, Inc. (Regeneron). The Company does not expect to generate any significant product revenue until it obtains regulatory approval of and commercialize any of the Company’s product candidates or enter into additional collaborative agreements with third parties, and it does not know when, or if, either will occur. The Company expects to continue to incur significant losses for the foreseeable future, and it expects the losses to increase as the Company continues the development of, and seek regulatory approvals for, its product candidates and begin to commercialize any approved products. The Company is subject to all of the risks typically related to the development of new product candidates, including, but not limited to, raising additional capital, development by its competitors of new technological innovations, risk of failure in preclinical and clinical studies, safety and efficacy of its product candidates in clinical trials, the risk of relying on external parties such as contract research organizations (CROs) and contract manufacturing organizations (CMOs), the regulatory approval process, market acceptance of the Company’s products once approved, lack of marketing and sales history, dependence on key personnel and protection of proprietary technology and it may encounter unforeseen expenses, difficulties, complications, delays, and other unknown factors that may adversely affect its business.

Until such time as the Company can generate significant revenue from product sales, if ever, the Company expects to finance its operations through the sale of equity, debt financings, collaborative or other arrangements with corporate or other sources of financing. Adequate funding may not be available to the Company on acceptable terms or at all. The Company’s failure to raise capital as and when needed could have a negative impact on its financial condition and the Company’s ability to pursue its business strategies. Although the Company continues to pursue these plans, there is no assurance that the Company will be successful in obtaining sufficient funding on terms acceptable to the Company to fund continuing operations, if at all.