TScan Therapeutics, Inc. announced that the first patient has been dosed in its Phase 1 umbrella trial of TSC-100 and TSC-101 targeting minor histocompatibility antigens (MiHA) HA-1 and HA-2, respectively, to treat residual leukemia and prevent relapse following hematopoietic cell transplantation (HCT) using reduced intensity conditioning (RIC) in patients with acute myeloid leukemia (AML), myelodysplastic syndromes (MDS), or acute lymphocytic leukemia (ALL). The patient was treated with TSC-101, the first clinical cell therapy product targeting MiHA HA-2. These therapies may ultimately enable more patients to be treated with transplant by using the more tolerable RIC regimen followed by TSC-100 or TSC-101. The Phase 1 umbrella trial is a multi-arm, i3+3 study evaluating TSC-100, TSC-101, and standard of care HCT alone (control arm) in patients with AML, ALL or MDS.

Treatment assignment is based on HLA and antigen expression, and the endpoints will include safety of repeated doses and efficacy of the TCR-T as compared to the control arm. Exploratory endpoints include cellular kinetics, minimal residual disease rates, percentage of donor chimerism, and persistence of TSC-100 and TSC-101. To learn more about the clinical trial, visit clinicaltrials.gov (identifier: NCT 05473910).

About TScan Therapeutics, Inc. TScan is a clinical-stage biopharmaceutical company focused on the development of T cell receptor (TCR)-engineered T cell therapies (TCR-T) for the treatment of patients with cancer. The Company's lead TCR-T therapy candidates, TSC-100 and TSC-101, are in development for the treatment of patients with hematologic malignancies to eliminate residual disease and prevent relapse after allogeneic hematopoietic cell transplantation. The Company is also developing multiplexed TCR-T therapy candidates for the treatment of various solid tumors.

The Company has developed and continues to build its ImmunoBank, the Company's repository of therapeutic TCRs that recognize diverse targets and are associated with multiple HLA types, to provide customized multiplexed TCR-T therapies for patients with a variety of solid tumors. Forward-Looking Statements This release contains forward-looking statements within the meaning of the Private Securities Litigation Reform Act of 1995, including, but not limited to, express or implied statements regarding the Company's plans, progress, and timing relating to the Company's hematologic malignancies programs, including the enrollment of patients and presentation of data, the structure, timing and success of the Company's planned preclinical development, submission of INDs, and clinical trials, the potential benefits of any of the Company's proprietary platforms, multiplexing, or current or future product candidates in treating patients, and the Company's goals and strategy. TScan intends such forward-looking statements to be covered by the safe harbor provisions for forward-looking statements contained in Section 21E of the Securities Exchange Act of 1934 and the Private Securities Litigation Reform Act of 1995.