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Company to present poster on initial data from heme malignancies Phase 1 trial at the 65th ASH Annual Meeting and Exposition; Company to host virtual KOL event on Monday, December 11, 2023, at 8:00 a.m. ET Announced recent FDA clearance of IND for TSC-203-A0201 targeting PRAME Presented six posters at the SITC 38th Annual Meeting, highlighting solid tumor Phase 1 trial design and addition of melanoma-associated antigen C2 (MAGE-C2) to ImmunoBank Ended Q3 with cash, cash equivalents, and marketable securities of $215.4 million, funding operations into 2026 WALTHAM, Mass., Nov. 09, 2023 (GLOBE NEWSWIRE) -- TScan Therapeutics, Inc. (Nasdaq: TCRX), 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, today reported financial results and provided a corporate update for the third quarter ended September 30, 2023. “During the third quarter we made meaningful progress across both our heme and solid tumor programs and plan to share initial results from our heme program on six to eight patients treated with TCR-T, as well as several control arm patients, at the ASH Annual Meeting in December,” said Gavin MacBeath, Ph.D., Chief Executive Officer. “With the recent FDA clearance of our IND for TSC-203-A0201 targeting PRAME, we remain committed to populating the ImmunoBank with TCRs that address different targets and HLA types to expand the reach of multiplexed TCR-T cell therapy. We are currently on track to file two additional INDs by the end of the year and further expand the ImmunoBank in 2024. TScan is funded to execute on upcoming anticipated milestones into 2026, by which time we expect to have duration of response data for patients treated with multiplex therapy in the solid tumor program and two-year relapse data for patients in the heme program.” Recent Corporate Highlights TScan will present a poster at the 65th American Society of Hematology (ASH) Annual Meeting and Exposition taking place in San Diego, CA, and online, December 9–12, 2023: Title: Initial Results of a Phase 1 Trial of TSC-100 and TSC-101, Engineered T Cell Therapies That Target Minor Histocompatibility Antigens to Prevent Relapse after Allogeneic Hematopoietic Cell TransplantationAuthors: Monzr Al Malki, Alla Keyzner, Hyung C. Suh, Aasiya Matin, Erica Buonomo, Yun Wang, Nina Abelowitz, Jim Murray, Gavin MacBeath, Debora Barton, Shrikanta Chattopadhyay, Ran ReshefPublication Number: 2090Session Name: 704. Cellular Immunotherapies: Early Phase and Investigational Therapies: Poster ISession Date & Time: Saturday, December 9, 2023; 5:30–7:30 p.m. PTLocation: San Diego Convention Center, Halls G-H The Company will host a virtual KOL event featuring Monzr M. Al Malki, M.D., on Monday, December 11, 2023, at 8:00 a.m. ET to discuss the data presented at ASH. Dr. Al Malki is an Associate Professor in the Department of Hematology & Hematopoietic Cell Transplantation and Director of the Unrelated Donor Bone Marrow Transplant and Haploidentical Transplant Programs at City of Hope. Details for attending the event can be found here. During the third quarter, TScan announced U.S. Food and Drug Administration (FDA) clearance of its investigational new drug (IND) application for TSC-203-A0201, a TCR-T targeting PReferentially expressed Antigen in MElanoma (PRAME). TSC-203-A0201 is TScan’s fourth TCR-T cell product cleared for use in its solid tumor program.This month, TScan presented six posters at the Society for Immunotherapy of Cancer (SITC) 38th Annual Meeting. Notable highlights include TScan’s solid tumor Phase 1 trial design supporting a separate screening protocol to identify patients ahead of disease progression, and the disclosure of the previously undisclosed target of TSC-201-B0702 as MAGE-C2. Copies of the presentation materials can be found on the “Publications” section of the Company’s website at www.tscan.com. Upcoming Anticipated Clinical Milestones Heme Malignancies Program: TScan’s two lead TCR-T cell therapy candidates, TSC-100 and TSC-101, are designed to target HA-1 and HA-2, respectively, to treat residual disease and prevent relapse in acute myeloid leukemia (AML), acute lymphocytic leukemia (ALL) and myelodysplastic syndromes (MDS) patients undergoing allogeneic haploidentical hematopoietic cell transplantation (HCT) with reduced intensity conditioning (RIC). (NCT05473910) Expects to reach the recommended Phase 2 dose for both TSC-100 and TSC-101 and report interim clinical data for the program by the end of 2023.Plans to complete Phase 1 dosing and report prevention of relapse data in 2024. Solid Tumor Program: TScan remains committed to populating the ImmunoBank, its collection of therapeutic TCRs across novel and validated targets as well as different HLA types, to overcome tumor heterogeneity and address resistance that can arise from HLA loss with multiplexed therapy. Anticipates further expansion of the ImmunoBank with IND filings for two additional TCR-Ts by year-end 2023.Plans to initiate Phase 1 solid tumor clinical study and enroll the first patient by year-end 2023.Expects to report initial multiplexed therapy data for its first combinations of TCR-Ts under T-Plex, as well as response data for singleplex cohorts, in 2024. Third Quarter 2023 Financial Results As of September 30, 2023, TScan Therapeutics had cash, cash equivalents, and marketable securities of $215.4 million, excluding $5.0 million of restricted cash. Based on current operating plans, the Company believes that existing cash, cash equivalents, and marketable securities will be sufficient to fund its operating expenses and capital expenditure requirements into 2026. Revenue for the third quarter ended September 30, 2023, was $3.9 million, compared to $3.4 million for the third quarter ended September 30, 2022 (2022 Quarter). This increase is primarily due to timing of research activities related to the collaboration agreement with Amgen in the second quarter of 2023 versus timing of research activities related to a collaboration and license agreement with Novartis Institutes for Biomedical Research, Inc. in the 2022 Quarter. Research and development expenses for the third quarter ended September 30, 2023, were $22.7 million, compared to $15.0 million for the 2022 Quarter. The increase of $7.7 million was primarily driven by increased costs associated with clinical trial start-up fees and patient enrollment, increased personnel costs, and expansion of facilities. General and administrative expenses for the third quarter ended September 30, 2023, were $5.9 million, compared to $4.9 million for the 2022 Quarter. The increase of $1.0 million in general and administrative expenses was primarily driven by increased legal and professional fees. For the third quarter ended September 30, 2023, TScan Therapeutics reported a net loss of $23.0 million, compared to a net loss of $16.2 million for the 2022 Quarter. As of September 30, 2023, the Company had issued and outstanding shares of 47,823,116, which consists of 43,546,528 shares of voting common stock and 4,276,588 shares of non-voting common stock, and outstanding pre-funded warrants to purchase 47,010,526 shares of voting common stock at an exercise price of $0.0001 per share. 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 program, including reaching recommended Phase 2 dose for TSC-100 and TSC-101, reporting interim clinical data, completing Phase 1 dosing, and reporting prevention of relapse data; the Company’s plans, progress, and timing relating to the Company’s solid tumor programs, including expanding the ImmunoBank, submitting of INDs, initiating clinical trials, and reporting data; the Company’s ability to fund its operating expenses and capital expenditure requirements with its existing cash and cash equivalents; the Company’s current and future research and development plans or expectations; 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; the Company’s beliefs about operating expenses and that it will have capital to fund the Company into 2026; 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. In some cases, you can identify forward-looking statements by terms such as, but not limited to, “may,” “might,” “will,” “objective,” “intend,” “should,” “could,” “can,” “would,” “expect,” “believe,” “anticipate,” “project,” “target,” “design,” “estimate,” “predict,” “potential,” “plan,” “on track,” or similar expressions or the negative of those terms. Such forward-looking statements are based upon current expectations that involve risks, changes in circumstances, assumptions, and uncertainties. The express or implied forward-looking statements included in this release are only predictions and are subject to a number of risks, uncertainties and assumptions, including, without limitation: the beneficial characteristics, safety, efficacy, therapeutic effects and potential advantages of TScan’s TCR-T therapy candidates; TScan’s expectations regarding its preclinical studies being predictive of clinical trial results; the timing of the initiation, progress and expected results of TScan’s preclinical studies, clinical trials and its research and development programs; TScan’s plans relating to developing and commercializing its TCR-T therapy candidates, if approved, including sales strategy; estimates of the size of the addressable market for TScan’s TCR-T therapy candidates; TScan’s manufacturing capabilities and the scalable nature of its manufacturing process; TScan’s estimates regarding expenses, future milestone payments and revenue, capital requirements and needs for additional financing; TScan’s expectations regarding competition; TScan’s anticipated growth strategies; TScan’s ability to attract or retain key personnel; TScan’s ability to establish and maintain development partnerships and collaborations; TScan’s expectations regarding federal, state and foreign regulatory requirements; TScan’s ability to obtain and maintain intellectual property protection for its proprietary platform technology and our product candidates; the sufficiency of TScan’s existing capital resources to fund its future operating expenses and capital expenditure requirements and execute on upcoming anticipated milestones into 2026; and the effect of the COVID-19 pandemic, including mitigation efforts and political, economic, legal and social effects, on any of the foregoing or other aspects of TScan’s business or operations; and other factors that are described in the “Risk Factors” and “Management’s Discussion and Analysis of Financial Condition and Results of Operations” sections of TScan’s most recent Annual Report on Form 10-K and any other filings that TScan has made or may make with the SEC in the future. Any forward-looking statements contained in this release represent TScan’s views only as of the date hereof and should not be relied upon as representing its views as of any subsequent date. Except as required by law, TScan explicitly disclaims any obligation to update any forward-looking statements. Contacts Heather SavelleTScan Therapeutics, Inc.VP, Investor Relations857-399-9840hsavelle@tscan.com Joyce AllaireLifeSci Advisors, LLCManaging Director617-435-6602jallaire@lifesciadvisors.com TScan Therapeutics, Inc.Condensed Consolidated Balance Sheet Data(unaudited, in thousands, except share amount) September 30,2023 December 31,2022Assets Cash and cash equivalents$155,193 $120,027 Other assets 136,186 79,064 Total assets$291,379 $199,091 Liabilities and Stockholders' Equity Total liabilities$122,418 $99,657 Total stockholders' equity 168,961 99,434 Total liabilities and stockholders' deficit$291,379 $199,091 Common stock outstanding as of September 30, 2023 47,823,116 TScan Therapeutics, Inc.Condensed Consolidated Statements of Operations(unaudited, in thousands, except share and per share amounts) Three Months Ended September 30, 2023 2022Revenue Collaboration and license revenue$3,887 $3,363 Operating expenses: Research and development 22,741 15,031 General and administrative 5,894 4,910 Total operating expenses 28,635 19,941 Loss from operations (24,748) (16,578)Interest and other income, net 2,733 534 Interest expense (982) (201)Net loss$(22,997) $(16,245)Net loss per share, basic and diluted$(0.24) $(0.67)Weighted average common shares outstanding—basic and diluted 94,829,844 24,073,935

Poster highlights Phase 1 results following treatment with TSC-100 and TSC-101 after hematopoietic cell transplantation Company to host a virtual KOL event featuring Monzr M. Al Malki, M.D., to discuss highlights from the meeting and preliminary data today, Wednesday, May 17th at 5:30 p.m. ET WALTHAM, Mass., May 17, 2023 (GLOBE NEWSWIRE) -- TScan Therapeutics, Inc. (Nasdaq: TCRX), 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, today announced a poster presentation highlighting preliminary data from the Phase 1 umbrella clinical trial evaluating TSC-100 and TSC-101 targeting minor histocompatibility antigens (MiHA) HA-1 and HA-2, respectively, to treat residual disease 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) at the American Society of Gene & Cell Therapy (ASGCT) 26th Annual Meeting 2023. TScan has developed two lead TCR-T cell therapy candidates, TSC-100 and TSC-101, that express TCRs targeting MiHAs HA-1 and HA-2, respectively, both presented by HLA-A*02:01. The goal is to select HCT patients who are HA-1 or HA-2 positive, with donors who are mismatched on either the MiHA or HLA-A*02:01. In this context, TSC-100 and TSC-101 are designed to eliminate all recipient hematopoietic cells, including malignant cells, that persist post-transplant, while leaving donor-derived cells unaffected. Both products are being developed in patients with AML, ALL, and MDS undergoing allogeneic haploidentical HCT with RIC, with the goal of preventing disease relapse. Approximately 42% of patients with these diseases relapse within two years of RIC transplant, at which point there are limited treatment options and poor prognosis. The longer-term objective is to enable more patients to maintain prolonged remission after receiving HCT with RIC, which is a more tolerable conditioning regimen than myeloablative conditioning. “We continue to make meaningful progress in our Phase 1 umbrella trial with preliminary data presented at ASGCT demonstrating notable differences following treatment with both of our TCR-T cell therapy candidates,” said Debora Barton, M.D., Chief Medical Officer. “In a p53-mutated MDS patient who received TSC-101 infusion, we observed T cell expansion between 14 and 21 days post-treatment and observed markers of T cell activation and proliferation. Particularly encouraging, this patient had 100% donor chimerism post-transplant with no detectable patient-derived hematopoietic cells with sensitivity limit of 0.13%, and no dose-limiting toxicities. Our Phase 1 study is rapidly enrolling and TSC-101 is advancing into the second dose level. We are on track to reach the recommended Phase 2 dose for TSC-100 and TSC-101 and report interim clinical data for the program by the end of 2023.” Gavin MacBeath, Ph.D., acting Chief Executive Officer and Chief Scientific and Operating Officer added: “We are very excited to progress to the second dose level for TSC-101 after seeing encouraging results from the patient at this first dose level. We are hopeful to continue to produce robust clinical outcomes as we progress our Phase 1 trial and remain excited about the potential clinical benefits our engineered T cells may have in difficult-to-treat patient populations.” 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. Patients enrolled in Dose Level 1 (DL1) receive either TSC-100 or TSC-101 upon count recovery after HCT at approximately day 21. Patients enrolled in Dose Level 2 (DL2) will receive the same dose of TSC-100 or TSC-101 approximately 21 days post-transplant, followed by a second dose administered 40 days after the initial dose, provided there are no safety issues. The trial design also includes a third dose level (DL3), where the second dose is escalated 4-fold. Key Poster Highlights: Phase 1 umbrella clinical trial evaluating TSC-100 and TSC-101 targeting MiHAs HA-1 and HA-2, respectively, to treat residual disease and prevent relapse following HCT using RIC in patients with AML, MDS or ALL Two control arm patients have been enrolled and received standard of care (SOC) (HCT alone): Both control arm patients have medium-risk MDS and experienced incomplete donor chimerism (presence of patient-derived cells) following transplant One patient is now in early stages of relapse: after 100 days, patient-derived cells are still observed and increasing TSC-101 treatment arm (n=1 high-risk MDS with p53 mutation): DL1 administered 21 days after transplant Engineered T cells showed expansion between 14-21 days after infusion Detectable markers of activation and proliferation observed Twenty-one days after treatment and 42 days after transplant, donor chimerism was at 100% (no detectable patient-derived hematopoietic cells with sensitivity limit of 0.13%) Minimal residual disease (MRD) assessment: p53 mutation was not detected post-transplant in bone marrow and peripheral blood samples, with sensitivity limit of 0.01% No DLTs observed Study advancing to DL2 TSC-100 treatment arm (n=1 T-cell ALL): DL1 administered 28 days after transplant T cell expansion occurred on Day 7 with detectable markers of T cell activation and proliferation Two assays are used to detect the action of T cells: MRD: SOC assays measuring remaining malignant cells use flow cytometry, which has a sensitivity of ~0.1% High sensitivity assay based on next-generation sequencing (NGS) and droplet digital PCR is also used in this study, with a sensitivity of 0.01% Chimerism: SOC STR assays have ~1% sensitivity Study is using the high-sensitivity NGS-based Alloheme assay, with a sensitivity of ~0.13% A copy of the poster can be accessed on the “Publications” section of the Company’s website at . Virtual KOL Event The Company will share highlights from its poster presented at ASGCT, featuring Monzer M. Al Malki, M.D, Associate Profession, Division of Leukemia, Department of Hematology and Hematopoietic Cell Transplantation, City of Hope, on Wednesday, May 17th at 5:30 p.m. ET to discuss the presentation and results from the ongoing Phase 1 study of TSC-100 and TSC-101 to treat residual disease and prevent relapse following HCT using RIC in patients with AML, MDS and ALL. To register for the event, please click here. A replay will be available on the “Events and Presentations” section of the Company’s website at ir.tscan.com. 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 program, including patient enrollment, reaching recommended Phase 2 dose for TSC-100 and TSC-101, and interim clinical data; the structure, timing and success of the Company’s planned preclinical development 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, focus, 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. In some cases, you can identify forward-looking statements by terms such as, but not limited to, “may,” “might,” “advance,” “will,” “objective,” “intend,” “should,” “could,” “can,” “would,” “expect,” “believe,” “anticipate,” “project,” “target,” “design,” “estimate,” “predict,” “potential,” “plan,” “on track,” or similar expressions or the negative of those terms. Such forward-looking statements are based upon current expectations that involve risks, changes in circumstances, assumptions, and uncertainties. The express or implied forward-looking statements included in this release are only predictions and are subject to a number of risks, uncertainties and assumptions, including, without limitation: the beneficial characteristics, safety, efficacy, therapeutic effects and potential advantages of TScan’s TCR-T therapy candidates; TScan’s expectations regarding its preclinical studies being predictive of clinical trial results; TScan’s approved INDs and enrollment of patients in its study being indicative or predictive of bringing TScan closer to its goal of providing customized TCR-T therapies to treat patients with cancer; the partnership with Amgen being indicative or predictive of the value of TScan’s target discovery platform outside of oncology; the timing of the launch, initiation, progress and expected results and announcements of TScan’s preclinical studies, clinical trials and its research and development programs; TScan’s timeline regarding its filing of INDs for its TCRs throughout the year, TScan’s ability to enroll patients for its clinical trials within its expected timeline, TScan’s plans relating to developing and commercializing its TCR-T therapy candidates, if approved, including sales strategy; estimates of the size of the addressable market for TScan’s TCR-T therapy candidates; TScan’s manufacturing capabilities and the scalable nature of its manufacturing process; TScan’s estimates regarding expenses, future milestone payments and revenue, capital requirements and needs for additional financing; TScan’s expectations regarding competition; TScan’s anticipated growth strategies; TScan’s ability to attract or retain key personnel; TScan’s ability to establish and maintain development partnerships and collaborations; TScan’s expectations regarding federal, state and foreign regulatory requirements; TScan’s ability to obtain and maintain intellectual property protection for its proprietary platform technology and our product candidates; the sufficiency of TScan’s existing capital resources to fund its future operating expenses and capital expenditure requirements; and other factors that are described in the “Risk Factors” and “Management’s Discussion and Analysis of Financial Condition and Results of Operations” sections of TScan’s most recent Annual Report on Form 10-K and any other filings that TScan has made or may make with the SEC in the future. Any forward-looking statements contained in this release represent TScan’s views only as of the date hereof and should not be relied upon as representing its views as of any subsequent date. Except as required by law, TScan explicitly disclaims any obligation to update any forward-looking statements. Contacts Heather Savelle TScan Therapeutics, Inc. VP, Investor Relations 857-399-9840 hsavelle@tscan.com Joyce Allaire LifeSci Advisors, LLC Managing Director 617-435-6602 jallaire@lifesciadvisors.com

Entered into partnership with Amgen to identify novel targets in Crohn’s disease; TScan to receive $30 million upfront Enrolled patients in all three arms of Phase 1 hematologic malignancies study; TSC-101 progressing to second dose level Announced upcoming trial-in-progress poster presentation on 5/17 at ASGCT, followed by call at 5:30 p.m. ET Appointed Barbara Klencke, M.D., to Board of Directors Ended 1Q 2023 with cash and cash equivalents of $95.6 million, which combined with Amgen partnership extends cash runway into 3Q 2024 WALTHAM, Mass., May 10, 2023 (GLOBE NEWSWIRE) -- TScan Therapeutics, Inc. (Nasdaq: TCRX) (“TScan” or the “Company”), 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, today reported financial results and provided a corporate update for the first quarter ended March 31, 2023. “The partnership with Amgen highlights the additional value of TScan’s target discovery platform outside oncology, and we look forward to working with them to identify novel T-cell targets in Crohn’s disease,” said Gavin MacBeath, Ph.D., acting Chief Executive Officer and Chief Scientific and Operating Officer. “During the first quarter we announced the dosing of our first patient in the Phase 1 heme malignancies umbrella study. This patient was dosed with TSC-101, which targets minor histocompatibility antigen HA-2, and we are pleased to announce that the Safety Review Committee has now approved initiating dose level two for TSC-101. The second dose level will consist of two successive doses of TSC-101, administered 40 days apart. We have also recently dosed the first patient in the TSC-100 arm, achieving our midyear milestone of enrolling patients in all three arms of the study. With regards to solid tumors, we remain on track to file INDs for two additional TCRs by the middle of 2023 and two more by the end of the year. These will cover additional target antigens, including HPV16 and PRAME, and a variety of HLA types, allowing us to further expand the reach of multiplexed TCR-T cell therapy.” Recent Corporate Highlights In May 2023, the Company announced a partnership with Amgen to identify T-cell targets in Crohn’s disease for the development of novel therapeutics. The partnership combines TScan’s proprietary target discovery platform with Amgen’s expertise in Crohn’s disease and their capabilities to develop novel, target-specific treatments for autoimmune disorders. TScan will receive $30 million up front with potential development and commercial milestone payments exceeding $500 million. In March 2023, TScan announced that the first patient was dosed in the Phase 1 umbrella clinical trial evaluating TSC-100 and TSC-101 for the treatment of patients with hematologic malignancies undergoing hematopoietic cell transplantation (HCT). The first patient was treated with TSC-101, the first clinical cell therapy product targeting minor histocompatibility antigen (MiHA) HA-2, to treat residual leukemia and prevent relapse following HCT. After completing the dose limiting toxicity observation period for patient one, the Safety Review Committee approved escalating to dose level two for TSC-101. TScan recently dosed the first patient in the TSC-100 arm (targeting MiHA HA-1) of the Phase 1 study in hematologic malignancies. The Company has now enrolled patients in all three arms of the study, including the two treatment arms and the control arm. The Company will present a trial-in-progress poster at the American Society of Gene and Cell Therapy (ASGCT) 26th Annual Meeting on Wednesday, May 17, 2023:Title: Trial in Progress: A Phase 1 Trial of TSC-100 and TSC-101, Engineered T Cell Therapies that Target Minor Histocompatibility Antigens to Eliminate Residual Disease After Hematopoietic Cell TransplantationPresenter: Monzr M. Al Maki, M.D.Poster Board and Abstract Number: 798Session Title: Wednesday Poster SessionSession Date/Time: Wednesday, May 17, 2023, at 12:00 p.m. PT / 3:00 p.m. ETThe Company will host a virtual event on Wednesday, May 17th at 5:30 p.m. ET to discuss highlights from the presentation. Registration for the event can be found here. The Company recently announced the appointment of Barbara Klencke, M.D., to its Board of Directors. Dr. Klencke is an accomplished oncology drug developer with a demonstrated track record of success, having made substantial contributions to the development and approval of numerous oncology products. She most recently served as the Chief Medical and Chief Development Officer of Sierra Oncology, Inc., which was acquired by GlaxoSmithKline in 2022. Upcoming Anticipated Milestones Hematologic Malignancies Program: Enrolled patients in all three arms in the Phase 1 umbrella trial (NCT05473910) for TSC-100 and TSC-101, with upcoming poster presentation at the ASGCT 26th Annual Meeting.Expects to reach the recommended Phase 2 dose for TSC-100 and TSC-101 and report interim clinical data for the program by the end of 2023.Plans to complete Phase 1 dosing and report prevention of relapse data in 2024.Anticipates reporting two-year relapse data and initiating a registration trial in 2025. Solid Tumor Program: Anticipates further expansion of the ImmunoBank by filing INDs for two additional TCR-Ts (TSC-200-A0201 targeting HPV16 and TSC-203-A0201 targeting PRAME) by the middle of 2023, and two more TCR-Ts by year end.Plans to initiate Phase 1 solid tumor clinical study in the second half of 2023 and anticipates sharing preliminary singleplex data for the most advanced TCRs by the end of 2023.Expects to report initial multiplexed therapy data for its first combination of TCR-Ts under T-Plex, as well as response data for initial singleplex cohorts, in 2024.Anticipates T-Plex duration of response data and singleplex response data for additional TCR-Ts in 2025. First Quarter 2023 Financial Results As of March 31, 2023, TScan Therapeutics had cash and cash equivalents of $95.6 million, excluding $5.0 million of restricted cash. Based on current operating plans, the Company believes that existing cash and cash equivalents, combined with expected proceeds from the Amgen partnership, will be sufficient to fund its operating expenses and capital expenditure requirements into the third quarter of 2024. Revenue for the first quarter ended March 31, 2023, was $6.8 million, compared to $3.0 million for the first quarter ended March 31, 2022 (2022 Quarter). This increase is primarily due to the timing of research activities related to the conclusion of the Company’s Collaboration and License Agreement with Novartis Institutes for Biomedical Research, Inc. Research and development expenses for the first quarter ended March 31, 2023, were $21.8 million, compared to $14.7 million for the 2022 Quarter. The increase of $7.1 million was primarily driven by an increase in personnel expense, expansion of leased facilities, and Phase 1 study start-up activities for the hematologic malignancies and solid tumor clinical trials. General and administrative expenses for the first quarter ended March 31, 2023, were $7.8 million, compared to $4.5 million for the 2022 Quarter. The increase of $3.3 million in general and administrative expenses was primarily driven by increased personnel and facilities costs to support the progress of the Company into the clinic. For the first quarter ended March 31, 2023, TScan Therapeutics reported a net loss of $22.6 million, compared to a net loss of $16.2 million for the 2022 Quarter. As of March 31, 2023, the Company had issued and outstanding shares of 24,225,954, which consists of 19,480,729 shares of voting common stock and 4,745,225 shares of non-voting common stock. 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 program, including patient enrollment, reaching recommended Phase 2 dose for TSC-100 and TSC-101, interim clinical data, and prevention of relapse data; the Company’s plans, progress, and timing relating to the Company’s solid tumor program, including submission of INDs and reporting of preliminary data and initial multiplexed therapy data; the Company’s ability to fund its operating expenses and capital expenditure requirements with its existing cash and cash equivalents; the structure, timing and success of the Company’s planned preclinical development 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, focus, strategy, and anticipated financial performance. 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. In some cases, you can identify forward-looking statements by terms such as, but not limited to, “may,” “might,” “advance,” “will,” “objective,” “intend,” “should,” “could,” “can,” “would,” “expect,” “believe,” “anticipate,” “project,” “target,” “design,” “estimate,” “predict,” “potential,” “plan,” “on track,” or similar expressions or the negative of those terms. Such forward-looking statements are based upon current expectations that involve risks, changes in circumstances, assumptions, and uncertainties. The express or implied forward-looking statements included in this release are only predictions and are subject to a number of risks, uncertainties and assumptions, including, without limitation: the beneficial characteristics, safety, efficacy, therapeutic effects and potential advantages of TScan’s TCR-T therapy candidates; TScan’s expectations regarding its preclinical studies being predictive of clinical trial results; TScan’s approved INDs and enrollment of patients in its study being indicative or predictive of bringing TScan closer to its goal of providing customized TCR-T therapies to treat patients with cancer; the partnership with Amgen being indicative or predictive of the value of TScan’s target discovery platform outside of oncology; the timing of the launch, initiation, progress and expected results and announcements of TScan’s preclinical studies, clinical trials and its research and development programs; TScan’s timeline regarding its filing of INDs for its TCRs throughout the year, TScan’s ability to enroll patients for its clinical trials within its expected timeline, TScan’s plans relating to developing and commercializing its TCR-T therapy candidates, if approved, including sales strategy; estimates of the size of the addressable market for TScan’s TCR-T therapy candidates; TScan’s manufacturing capabilities and the scalable nature of its manufacturing process; TScan’s estimates regarding expenses, future milestone payments and revenue, capital requirements and needs for additional financing; TScan’s expectations regarding competition; TScan’s anticipated growth strategies; TScan’s ability to attract or retain key personnel; TScan’s ability to establish and maintain development partnerships and collaborations; TScan’s expectations regarding federal, state and foreign regulatory requirements; TScan’s ability to obtain and maintain intellectual property protection for its proprietary platform technology and our product candidates; the sufficiency of TScan’s existing capital resources to fund its future operating expenses and capital expenditure requirements; and other factors that are described in the “Risk Factors” and “Management’s Discussion and Analysis of Financial Condition and Results of Operations” sections of TScan’s most recent Annual Report on Form 10-K and any other filings that TScan has made or may make with the SEC in the future. Any forward-looking statements contained in this release represent TScan’s views only as of the date hereof and should not be relied upon as representing its views as of any subsequent date. Except as required by law, TScan explicitly disclaims any obligation to update any forward-looking statements. Contacts Heather SavelleTScan Therapeutics, Inc.VP, Investor Relations857-399-9840hsavelle@tscan.com Joyce AllaireLifeSci Advisors, LLCManaging Director617-435-6602jallaire@lifesciadvisors.com TScan Therapeutics, Inc.Condensed Consolidated Balance Sheet Data(unaudited, in thousands, except share amount) March 31,2023 December 31, 2022 Assets Cash and cash equivalents $95,608 $120,027 Other assets 77,969 79,064 Total assets $173,577 $199,091 Liabilities and Stockholders' Equity Total liabilities $95,559 $99,657 Total stockholders' equity 78,018 99,434 Total liabilities and stockholders' deficit $173,577 $199,091 Common stock outstanding as of March 31, 2023 24,225,954 TScan Therapeutics, Inc.Condensed Consolidated Statements of Operations(unaudited, in thousands, except share and per share amounts) Three Months Ended March 31, 2023 2022 Revenue Collaboration and license revenue $6,803 $3,021 Operating expenses: Research and development 21,779 14,690 General and administrative 7,767 4,494 Total operating expenses 29,546 19,184 Loss from operations (22,743) (16,163) Interest and other income, net 1,136 7 Interest expense (956) - Net loss $(22,563) $(16,156) Net loss per share, basic and diluted $(0.93) $(0.67) Weighted average common shares outstanding—basic and diluted 24,225,954 23,974,642