Nature of Business and Basis of Presentation	6 Months Ended
Jun. 30, 2026
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 TScan Therapeutics, Inc. and its wholly-owned subsidiary, TScan Securities Corporation (the Company), is a biotechnology company that was incorporated in Delaware on April 17, 2018 and has a principal place of business in Waltham, Massachusetts. The Company is focused on developing a pipeline of TCR-T therapy product candidates for the treatment of patients with cancer. Basis of Presentation The accompanying interim unaudited condensed consolidated financial statements have been prepared in accordance with generally accepted accounting principles in the United States (U.S. GAAP) and applicable rules and regulations of the Securities and Exchange Commission (the SEC) regarding interim financial reporting, and the instructions to Form 10-Q and Article 10 of Regulation S-X. Accordingly, they do not include all of the information and footnotes required by U.S. GAAP for complete financial statements. Management believes that the interim financial statements reflect all adjustments, which include only normal recurring adjustments necessary for the fair statement of the Company’s financial position, results of its operations and cash flows. The condensed consolidated financial statements include the accounts of TScan Therapeutics, Inc. and its subsidiary, TScan Securities Corporation. All intercompany balances and transactions have been eliminated in consolidation. The results for the three and six months ended June 30, 2026, are not necessarily indicative of results to be expected for the year ending December 31, 2026, any other interim periods, or any future year or period. The accompanying condensed consolidated financial statements should be read in conjunction with the Company’s audited consolidated financial statements and notes thereto included in the Company’s Annual Report on Form 10-K, which was filed with the SEC on March 4, 2026. In the opinion of the Company’s management, all adjustments (consisting of normal and recurring adjustments) considered necessary for a fair statement of the results for the interim periods presented have been included. Risks, Uncertainties and Going Concern The Company is subject to risks common to companies in the biotechnology industry, including, but not limited to, successful development of technology, obtaining additional funding, protection of proprietary technology, compliance with government regulations, risks of failure of preclinical studies and clinical trials, the need to obtain marketing approval for its product candidates and the ability to successfully market any products that receive approval, fluctuations in operating results, economic pressure impacting therapeutic pricing, dependence on key personnel, risks associated with changes in technologies, development by competitors of technological innovations and the ability to scale manufacturing to large scale production. Product candidates currently under development will require significant additional research and development efforts, including preclinical and clinical testing and regulatory approval prior to commercialization. These efforts require significant amounts of additional capital, adequate personnel and infrastructure and extensive compliance capabilities. Even if the Company’s development efforts are successful, it is uncertain when, if ever, the Company will realize significant revenue from sales. These unaudited condensed consolidated financial statements have been prepared in accordance with U.S. generally accepted accounting principles assuming the Company will continue as a going concern. The going concern assumption contemplates the realization of assets and satisfaction of liabilities in the normal course of business. However, substantial doubt about the Company’s ability to continue as a going concern exists. The Company has primarily funded its operations with proceeds from sales of capital stock, payments received under its license and collaboration agreements and debt financings. Since inception, the Company has incurred recurring net losses, including net losses of $30.4 million and $37.0 million for the three months ended June 30, 2026 and 2025, respectively, and $59.0 million and $71.1 million for the six months ended June 30, 2026 and 2025, respectively. As of June 30, 2026, the Company had an accumulated deficit of $563.9 million. As of June 30, 2026, the Company had cash and cash equivalents of $100.2 million, excluding restricted cash of $5.0 million. In accordance with generally accepted accounting principles, the Company evaluated whether conditions and events, considered in the aggregate, raise substantial doubt about the Company’s ability to continue as a going concern for twelve months after the date these condensed consolidated financial statements are issued. The Company has sustained recurring losses since inception, used substantial cash in operations, and holds current liabilities due in relation to repayment of its debt. Furthermore, the Company expects to continue to incur operating losses and negative cash flows for the foreseeable future as it executes its strategic plan, including costs related to the research and development of its product candidates. Based on the Company’s current operating plan, existing cash and cash equivalents are not expected to be sufficient to fund the Company’s obligations for twelve months after the date these condensed consolidated financial statements are issued. These conditions raise substantial doubt about the Company’s ability to continue as a going concern. The Company is evaluating strategies to obtain the required additional funding for future operations. These strategies may include, but are not limited to, entering into collaboration agreements, offerings of the Company’s equity securities, the incurrence of debt, or reductions in operating expenditures. However, there can be no assurance that the Company will be able to obtain additional liquidity when needed, on acceptable terms, or at all. Therefore, substantial doubt about the Company’s ability to continue as a going concern has not been alleviated. The unaudited condensed consolidated financial statements do not include any adjustments to the carrying amounts and classification of assets, liabilities, and reported expenses that may be necessary if the Company were unable to continue as a going concern. Emerging Growth Company Status The Company qualifies as an “emerging growth company” as defined in the Jumpstart Our Business Startups Act of 2012 (JOBS Act) and has elected to “opt in” to the extended transition related to complying with new or revised accounting standards, which means that when a standard is issued or revised and it has different application dates for public and nonpublic companies, the Company will adopt the new or revised standard at the time nonpublic companies adopt the new or revised standard and will do so until such time that the Company either (i) irrevocably elects to “opt out” of such extended transition period or (ii) no longer qualifies as an emerging growth company. The Company may choose to early adopt any new or revised accounting standards whenever such early adoption is permitted for nonpublic companies.

Nature of Business and Basis of Presentation

6 Months Ended

Jun. 30, 2026

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

TScan Therapeutics, Inc. and its wholly-owned subsidiary, TScan Securities Corporation (the Company), is a biotechnology company that was incorporated in Delaware on April 17, 2018 and has a principal place of business in Waltham, Massachusetts. The Company is focused on developing a pipeline of TCR-T therapy product candidates for the treatment of patients with cancer.

Basis of Presentation

The accompanying interim unaudited condensed consolidated financial statements have been prepared in accordance with generally accepted accounting principles in the United States (U.S. GAAP) and applicable rules and regulations of the Securities and Exchange Commission (the SEC) regarding interim financial reporting, and the instructions to Form 10-Q and Article 10 of Regulation S-X. Accordingly, they do not include all of the information and footnotes required by U.S. GAAP for complete financial statements. Management believes that the interim financial statements reflect all adjustments, which include only normal recurring adjustments necessary for the fair statement of the Company’s financial position, results of its operations and cash flows. The condensed consolidated financial statements include the accounts of TScan Therapeutics, Inc. and its subsidiary, TScan Securities Corporation. All intercompany balances and transactions have been eliminated in consolidation. The results for the three and six months ended June 30, 2026, are not necessarily indicative of results to be expected for the year ending December 31, 2026, any other interim periods, or any future year or period. The accompanying condensed consolidated financial statements should be read in conjunction with the Company’s audited consolidated financial statements and notes thereto included in the Company’s Annual Report on Form 10-K, which was filed with the SEC on March 4, 2026. In the opinion of the Company’s management, all adjustments (consisting of normal and recurring adjustments) considered necessary for a fair statement of the results for the interim periods presented have been included.

Risks, Uncertainties and Going Concern

The Company is subject to risks common to companies in the biotechnology industry, including, but not limited to, successful development of technology, obtaining additional funding, protection of proprietary technology, compliance with government regulations, risks of failure of preclinical studies and clinical trials, the need to obtain marketing approval for its product candidates and the ability to successfully market any products that receive approval, fluctuations in operating results, economic pressure impacting therapeutic pricing, dependence on key personnel, risks associated with changes in technologies, development by competitors of technological innovations and the ability to scale manufacturing to large scale production. Product candidates currently under development will require significant additional research and development efforts, including preclinical and clinical testing and regulatory approval prior to commercialization. These efforts require significant amounts of additional capital, adequate personnel and infrastructure and extensive compliance capabilities. Even if the Company’s development efforts are successful, it is uncertain when, if ever, the Company will realize significant revenue from sales.

These unaudited condensed consolidated financial statements have been prepared in accordance with U.S. generally accepted accounting principles assuming the Company will continue as a going concern. The going concern assumption contemplates the realization of assets and satisfaction of liabilities in the normal course of business. However, substantial doubt about the Company’s ability to continue as a going concern exists.

The Company has primarily funded its operations with proceeds from sales of capital stock, payments received under its license and collaboration agreements and debt financings. Since inception, the Company has incurred recurring net losses, including net losses of $30.4 million and $37.0 million for the three months ended June 30, 2026 and 2025, respectively, and $59.0 million and $71.1 million for the six months ended June 30, 2026 and 2025, respectively. As of June 30, 2026, the Company had an accumulated deficit of $563.9 million.

As of June 30, 2026, the Company had cash and cash equivalents of $100.2 million, excluding restricted cash of $5.0 million. In accordance with generally accepted accounting principles, the Company evaluated whether conditions and events, considered in the aggregate, raise substantial doubt about the Company’s ability to continue as a going concern for twelve months after the date these condensed consolidated financial statements are issued. The Company has sustained recurring losses since inception, used substantial cash in operations, and holds current liabilities due in relation to repayment of its debt. Furthermore, the Company expects to continue to incur operating losses and negative cash flows for the foreseeable future as it executes its strategic plan, including costs related to the research and development of its product candidates. Based on the Company’s current operating plan, existing cash and cash equivalents are not expected to be sufficient to fund the Company’s obligations for twelve months after the date these condensed

consolidated financial statements are issued. These conditions raise substantial doubt about the Company’s ability to continue as a going concern.

The Company is evaluating strategies to obtain the required additional funding for future operations. These strategies may include, but are not limited to, entering into collaboration agreements, offerings of the Company’s equity securities, the incurrence of debt, or reductions in operating expenditures. However, there can be no assurance that the Company will be able to obtain additional liquidity when needed, on acceptable terms, or at all. Therefore, substantial doubt about the Company’s ability to continue as a going concern has not been alleviated.

The unaudited condensed consolidated financial statements do not include any adjustments to the carrying amounts and classification of assets, liabilities, and reported expenses that may be necessary if the Company were unable to continue as a going concern.

Emerging Growth Company Status

The Company qualifies as an “emerging growth company” as defined in the Jumpstart Our Business Startups Act of 2012 (JOBS Act) and has elected to “opt in” to the extended transition related to complying with new or revised accounting standards, which means that when a standard is issued or revised and it has different application dates for public and nonpublic companies, the Company will adopt the new or revised standard at the time nonpublic companies adopt the new or revised standard and will do so until such time that the Company either (i) irrevocably elects to “opt out” of such extended transition period or (ii) no longer qualifies as an emerging growth company. The Company may choose to early adopt any new or revised accounting standards whenever such early adoption is permitted for nonpublic companies.