Material Agreement Form 8 K

Effective October 28, 2024, TScan Therapeutics, Inc. (the "Company") entered into a second amendment (the "Second Amendment") to its existing lease with PPF OFF 828-830Winter Street LLC (the "Landlord"), dated August 13, 2019, as amended by the first amendment thereto dated November 8, 2023 (as amended the "Existing Lease"), with respect to 25,472 rentable square feet of space (the "Existing Premises") in certain premises located at 830 Winter Street, Waltham, Massachusetts.

Under the terms of the Second Amendment, the Company has agreed to lease approximately an additional 25,628 rentable square feet of space (the "Expansion Premises") in the premises located at 830 Winter Street, Waltham, Massachusetts to support its operations, for a term commencing in the fourth quarter 2024 to October 31, 2029, subject to any permitted renewal pursuant to the Existing Lease. The Company will be obligated to pay the Landlord an additional base rent for the Expansion Premises at the monthly rate of $163,378.50, commencing two months after the start of the term for the Expansion Premises, for the first 12-monthperiod, $168,279.86 for the second 12-monthperiod, $173,328.25 for the third 12-monthperiod, $178,528.10 for the fourth 12-monthperiod, and $183,883.94 for the final 12-month period, which may be prorated for any partial year, in addition to the base rent for the Existing Premises as set forth in the Existing Lease.

Under the terms of the Second Amendment, the Landlord has agreed to provide to the Company a tenant improvement allowance of up to approximately $2,681,540.

The forgoing summary of the material terms of the Second Amendment is qualified in its entirety by reference to the complete text of the Second Amendment, a copy of which will be filed as an exhibit to the Company's Annual Report on Form 10-K for theyear ended December 31, 2024.