As filed with the Securities and Exchange Commission on March 4, 2026

Registration No. 333-   

UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

WASHINGTON, D.C. 20549

FORM S-8

REGISTRATION STATEMENT

UNDER

THE SECURITIES ACT OF 1933

TSCAN THERAPEUTICS, INC.

(Exact name of registrant as specified in its charter)

TSCAN THERAPEUTICS, INC. AMENDED AND RESTATED 2021 EQUITY INCENTIVE PLAN

TSCAN THERAPEUTICS, INC. 2021 EMPLOYEE STOCK PURCHASE PLAN

(Full title of the plan)

Gavin MacBeath

Chief Executive Officer

TScan Therapeutics, Inc.

830 Winter Street

Waltham, Massachusetts 02451

(Name and address of agent for service)

(857) 399-9500

(Telephone number, including area code, of agent for service)

Copies to:

Mitchell S. Bloom, Esq.

William D. Collins, Esq.

Finnbarr Murphy, Esq.

Goodwin Procter LLP

100 Northern Avenue

Boston, Massachusetts 02210

(617) 570-1000

Indicate by check mark whether the registrant is a large accelerated filer, an accelerated filer, a non-accelerated filer, a smaller reporting company or an emerging growth company. See the definitions of “large accelerated filer,” “accelerated filer,” “smaller reporting company,” and “emerging growth company” in Rule 12b-2 of the Exchange Act.

If an emerging growth company, indicate by check mark if the registrant has elected not to use the extended transition period for complying with any new or revised financial accounting standards provided pursuant to Section 7(a)(2)(B) of the Securities Act. ☐

EXPLANATORY NOTE

This Registration Statement on Form S-8 registers (i) 5,196,535 additional shares of common stock, $0.0001 par value per share (“Common Stock”), of TScan Therapeutics, Inc. (the “Registrant”), under the TScan Therapeutics, Inc. Amended and Restated 2021 Equity Incentive Plan (the “2021 Plan”) and (ii) 569,016 additional shares of Common Stock under the TScan Therapeutics, Inc. 2021 Employee Stock Purchase Plan (the “2021 ESPP”). The number of shares of Common Stock reserved and available for issuance under the 2021 Plan is subject to an automatic annual increase on each January 1, beginning in 2022, by an amount equal to the lower of (i) four percent of the number of shares of Common Stock outstanding (including the shares of Common Stock underlying outstanding pre-funded warrants) on the immediately preceding December 31 and (ii) an amount of shares determined by our Board of Directors. Accordingly, on January 1, 2026, the number of shares of Common Stock reserved and available for issuance under the 2021 Plan increased by 5,196,535. The additional shares are of the same class as other securities relating to the 2021 Plan for which the Registrant’s registration statements filed on Form S-8 with the Securities and Exchange Commission on July 16, 2021 (Registration No. 333-257941), March 9, 2022 (Registration No.  333-263380), March 8, 2023 (Registration No.  333-270343), June 16, 2023 (Registration No.  333-272733), March 6, 2024 (Registration No.  333-277695), June 14, 2024 (Registration No.  333-280212) and March 5, 2025 (Registration No. 333-285571) are effective. The number of shares of Common Stock reserved and available for issuance under the 2021 ESPP is subject to an automatic annual increase on each January 1, beginning in 2022, by an amount equal to the least of (i) one percent of the number of shares of Common Stock issued and outstanding on the immediately preceding December 31 or (ii) such number of shares of Common Stock as determined by our Board of Directors. Accordingly, on January 1, 2026, the number of shares of Common Stock reserved and available for issuance under the 2021 ESPP increased by 569,016. The additional shares are of the same class as other securities relating to the 2021 ESPP for which the Registrant’s registration statements filed on Form S-8 with the Securities and Exchange Commission on July 16, 2021 (Registration No. 333-257941), March 9, 2022 (Registration No.  333-263380), March 8, 2023 (Registration No.  333-270343), March 6, 2024 (Registration No.  333-277695) and March 5, 2025 (Registration No. 333-285571) are effective. The information contained in the Registrant’s registration statements on Form S-8 (Registration No. 333-257941, No. 333-263380, No. 333-270343, No. 333-272733, No. 333-277695, No. 333-280212 and No. 333-285571) is hereby incorporated by reference pursuant to General Instruction E.

Part II

INFORMATION REQUIRED IN THE REGISTRATION STATEMENT

SIGNATURES

Pursuant to the requirements of the Securities Act of 1933, as amended, the Registrant certifies that it has reasonable grounds to believe that it meets all of the requirements for filing on Form S-8 and has duly caused this Registration Statement to be signed on its behalf by the undersigned, thereunto duly authorized, in the City of Waltham, Commonwealth of Massachusetts, on March 4, 2026.

POWER OF ATTORNEY AND SIGNATURES

KNOW ALL PERSONS BY THESE PRESENTS, that each person whose signature appears below constitutes and appoints Gavin MacBeath and Jason A. Amello, and each of them, as such person’s true and lawful attorneys-in-fact and agents, with full power of substitution and resubstitution in each of them, for such person in such person’s place and stead, in any and all capacities, to sign for us and in our names in the capacities indicated below the Registration Statement on Form S-8 of TScan Therapeutics, Inc., and any or all amendments (including post-effective amendments), and to file the same, with all exhibits thereto, and other documents in connection therewith, with the Securities and Exchange Commission, granting unto said attorneys-in-fact and agents, and each of them, full power and authority to do and perform each and every act and thing requisite or necessary to be done in connection therewith and about the premises, as fully to all intents and purposes as he might or could do in person, hereby ratifying and confirming all that said attorneys-in-fact and agents or any of them, or substitutes of any of them, may lawfully do or cause to be done by virtue hereof.

Pursuant to the requirements of the Securities Act of 1933, as amended, this Registration Statement on Form S-8 has been signed by the following persons in the capacities and on the dates indicated.

Exhibit 5.1

		Goodwin Procter LLP 100 Northern Avenue Boston, MA 02210   goodwinlaw.com +1 617 570 1000

March 4, 2026

TScan Therapeutics, Inc.

830 Winter Street

Waltham, Massachusetts 02451

We have acted as your counsel in connection with your filing of a Registration Statement on Form S-8 (the “Registration Statement”) pursuant to the Securities Act of 1933, as amended (the “Securities Act”), on or about the date hereof relating to an aggregate of (i) 5,196,535 additional shares (the “Plan Shares”) of Common Stock, $0.0001 par value per share (“Common Stock”), of TScan Therapeutics, Inc., a Delaware corporation (the “Company”), that may be issued pursuant to the Company’s Amended and Restated 2021 Equity Incentive Plan (the “2021 Plan”) and (ii) 569,016 additional shares (collectively with the Plan Shares, the “Shares”) of Common Stock that may be issued pursuant to the Company’s 2021 Employee Stock Purchase Plan (collectively with the 2021 Plan, the “Plans”).

We have reviewed such documents and made such examination of law as we have deemed appropriate to give the opinion set forth below. We have relied, without independent verification, on certificates of public officials and, as to matters of fact material to the opinion set forth below, on certificates of officers of the Company.

For purposes of the opinion set forth below, we have assumed that, at the time Shares are issued, the total number of then unissued Shares, when added to the number of shares of Common Stock issued, subscribed for, or otherwise committed to be issued, does not exceed the number of shares of Common Stock authorized by the Company’s certificate of incorporation.

The opinion set forth below is limited to the Delaware General Corporation Law. Based on the foregoing, we are of the opinion that the Shares have been duly authorized and, when delivered against payment therefor in accordance with the terms of the Plans, will be validly issued, fully paid and nonassessable.

This opinion letter and the opinion it contains shall be interpreted in accordance with the Core Opinion Principles as published in 74 Business Lawyer 815 (Summer 2019).

We hereby consent to the inclusion of this opinion as Exhibit 5.1 to the Registration Statement. In giving our consent, we do not admit that we are in the category of persons whose consent is required under Section 7 of the Securities Act or the rules and regulations thereunder.

TScan Therapeutics, Inc.

March 4, 2026

Page 2

Exhibit 23.1

CONSENT OF INDEPENDENT REGISTERED PUBLIC ACCOUNTING FIRM

We consent to the incorporation by reference in this Registration Statement on Form S-8 of our report dated March 4, 2026, relating to the financial statements of TScan Therapeutics, Inc. appearing in the Annual Report on Form 10-K of TScan Therapeutics, Inc. for the year ended December 31, 2025.

/s/ Deloitte & Touche LLP

Boston, Massachusetts

March 4, 2026