Nature of Business and Plan of Operations	12 Months Ended
Dec. 31, 2022
Nature of Business and Plan of Operations
Nature of Business and Plan of Operations	IMMUNOGEN, INC. NOTES TO CONSOLIDATED FINANCIAL STATEMENTS A.Nature of Business and Plan of Operations ImmunoGen, Inc. (the Company) was incorporated in Massachusetts in 1981 and is focused on the development and commercialization of antibody-drug conjugates, or ADCs. On November 14, 2022, the U.S. Food and Drug Administration (FDA) granted accelerated approval for ELAHERE™ (mirvetuximab soravtansine-gynx) for the treatment of adult patients with folate receptor alpha (FRα)-positive, platinum-resistant epithelial ovarian, fallopian tube, or primary peritoneal cancer, who have received one to three prior systemic treatment regimens. ELAHERE was approved under FDA's accelerated approval program based on objective response rate (ORR), duration of response (DOR), and safety data from the pivotal SORAYA trial. Continued approval may be contingent upon verification and description of clinical benefit in a confirmatory trial. The Company has generally incurred operating losses and negative cash flows from operations since inception, incurred a net loss of $222.9 million during the year ended December 31, 2022, and had an accumulated deficit of approximately $1.7 billion as of December 31, 2022. The Company has primarily funded these losses through payments received from its collaborations and equity, convertible debt, and other financings such as royalty financing transactions. Until the Company can generate significant cash flows from sales of ELAHERE, management expects to continue to generate substantial operating losses for at least the near term as the Company incurs significant operating expenses related to research and development and selling and marketing of ELAHERE. At December 31, 2022, the Company had $275.1 million of cash and cash equivalents on hand. The Company’s current level of cash and cash equivalents is not sufficient to meet its current operating plans for the next twelve months following the issuance of these financial statements. As a result, substantial doubt is deemed to exist regarding the Company’s ability to continue as a going concern for a period of one year from the issuance of these financial statements. The Company plans to meet its operating cash flow requirements with its current cash and cash equivalents, cash generated from commercial sales of ELAHERE, milestone payments from new or existing collaborations, and additional funds accessed through equity, debt, or other financings such as royalty financing transactions, as well as cash preservation activities. Such activities may not succeed. The failure of the Company to obtain sufficient funds on acceptable terms could have a material adverse effect on the Company’s business, results of operations, and financial condition and require the Company to defer or limit some or all of its research, development, clinical and/or commercial projects, including trials to support potential label expansion of ELAHERE. The accompanying consolidated financial statements have been prepared on a going concern basis, which contemplates the realization of assets and satisfaction of liabilities in the ordinary course of business. The consolidated financial statements do not include any adjustments relating to the recoverability and classification of recorded asset amounts or the amounts and classification of liabilities that might result from the outcome of this uncertainty. The Company is subject to risks common to companies in the biotechnology industry including, but not limited to, the development by its competitors of new technological innovations, dependence on key personnel, protection of proprietary technology, manufacturing and marketing limitations, challenges entering into new collaborations, complexities associated with managing collaboration arrangements, third-party reimbursements, and compliance with governmental regulations.

Nature of Business and Plan of Operations

12 Months Ended

Dec. 31, 2022

Nature of Business and Plan of Operations

Nature of Business and Plan of Operations

IMMUNOGEN, INC.

NOTES TO CONSOLIDATED FINANCIAL STATEMENTS

A.Nature of Business and Plan of Operations

ImmunoGen, Inc. (the Company) was incorporated in Massachusetts in 1981 and is focused on the development and commercialization of antibody-drug conjugates, or ADCs. On November 14, 2022, the U.S. Food and Drug Administration (FDA) granted accelerated approval for ELAHERE™ (mirvetuximab soravtansine-gynx) for the treatment of adult patients with folate receptor alpha (FRα)-positive, platinum-resistant epithelial ovarian, fallopian tube, or primary peritoneal cancer, who have received one to three prior systemic treatment regimens. ELAHERE was approved under FDA's accelerated approval program based on objective response rate (ORR), duration of response (DOR), and safety data from the pivotal SORAYA trial. Continued approval may be contingent upon verification and description of clinical benefit in a confirmatory trial.

The Company has generally incurred operating losses and negative cash flows from operations since inception, incurred a net loss of $222.9 million during the year ended December 31, 2022, and had an accumulated deficit of approximately $1.7 billion as of December 31, 2022. The Company has primarily funded these losses through payments received from its collaborations and equity, convertible debt, and other financings such as royalty financing transactions. Until the Company can generate significant cash flows from sales of ELAHERE, management expects to continue to generate substantial operating losses for at least the near term as the Company incurs significant operating expenses related to research and development and selling and marketing of ELAHERE.

At December 31, 2022, the Company had $275.1 million of cash and cash equivalents on hand. The Company’s current level of cash and cash equivalents is not sufficient to meet its current operating plans for the next twelve months following the issuance of these financial statements. As a result, substantial doubt is deemed to exist regarding the Company’s ability to continue as a going concern for a period of one year from the issuance of these financial statements.

The Company plans to meet its operating cash flow requirements with its current cash and cash equivalents, cash generated from commercial sales of ELAHERE, milestone payments from new or existing collaborations, and additional funds accessed through equity, debt, or other financings such as royalty financing transactions, as well as cash preservation activities. Such activities may not succeed. The failure of the Company to obtain sufficient funds on acceptable terms could have a material adverse effect on the Company’s business, results of operations, and financial condition and require the Company to defer or limit some or all of its research, development, clinical and/or commercial projects, including trials to support potential label expansion of ELAHERE.

The accompanying consolidated financial statements have been prepared on a going concern basis, which contemplates the realization of assets and satisfaction of liabilities in the ordinary course of business. The consolidated financial statements do not include any adjustments relating to the recoverability and classification of recorded asset amounts or the amounts and classification of liabilities that might result from the outcome of this uncertainty.

The Company is subject to risks common to companies in the biotechnology industry including, but not limited to, the development by its competitors of new technological innovations, dependence on key personnel, protection of proprietary technology, manufacturing and marketing limitations, challenges entering into new collaborations, complexities associated with managing collaboration arrangements, third-party reimbursements, and compliance with governmental regulations.