MAGEC2

Presented updated data from ongoing Phase 1 study of TSC-100 and TSC-101 for the treatment of heme malignancies at the Tandem Meetings of ASTCT and CIBMTR; 8/8 (100%) patients in treatment arms are relapse-free and show complete donor chimerism Announced the clearance of two additional INDs for Solid Tumor Program: TSC-201-B0702 targeting MAGE-C2 on HLA-B*07:02 and TSC-204-A0101 targeting MAGE-A1 on HLA-A*01:01 Solid tumor clinical trial actively enrolling, with initial data for singleplex and multiplex cohorts anticipated in 2024 Expands leadership team with key appointments and promotions Cash, cash equivalents, and marketable securities continues to fund operations into 2026 WALTHAM, Mass., March 06, 2024 (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 for the three months and full year ended December 31, 2023, and provided a business update. “The advancements we made across our pipeline in 2023 have set the stage for a momentous year ahead as we continue to treat and follow patients in the heme malignancies study and commence patient dosing in the solid tumor program. We continue to make meaningful progress with our Phase 1 heme malignancies study, with updated data on eight treatment-arm patients and six control-arm patients presented at the Tandem Meetings of ASTCT and CIBMTR,” said Gavin MacBeath, Ph.D., Chief Executive Officer. “We are encouraged to see that none of the patients in the treatment arms has relapsed following treatment with TSC-100 or TSC-101, including one high-risk TP53-mutated MDS patient who has now reached one year of follow-up. The one-year mark is a meaningful milestone for patients as the likelihood of relapse is now much lower, leading to an improved quality of life. We look forward to completing Phase 1 enrollment and reporting clinical and translational data in 2024 with two-year relapse-free survival data in 2025.” “We are on-track to treat the first patient in our Phase 1 solid tumor program this month, which will bring us one step closer to delivering customized, enhanced, multiplexed TCR-T therapies to patients with a variety of solid tumors,” said Debora Barton, M.D., Chief Medical Officer. “Solid tumors are notoriously heterogenous, with tumors frequently expressing more than one target antigen. We believe the only way to eradicate solid tumors is through a multi-targeted approach. To make this a reality, we continue to prioritize expanding the ImmunoBank with additional TCRs to increase patient eligibility for multiplexed therapy. With recent FDA clearance of our INDs for TSC-201-B0702 and TSC-204-A0101, we now have six TCR-Ts cleared for clinical development. We look forward to continuing to advance the solid tumor program and sharing data on patients from singleplex and multiplex cohorts in 2024.” Recent Corporate Highlights In February 2024, the Company presented updated Phase 1 clinical results on lead TCR-T candidates TSC-100 and TSC-101 at the Tandem Meetings: Transplantation & Cellular Therapy Meetings of the American Society for Transplantation and Cellular Therapy (ASTCT®) and the Center for International Blood and Marrow Transplant Research (CIBMTR®). Data showed that all eight (100%) treatment-arm patients were free from relapse, including four patients with follow-up beyond ten months. Notably, one high-risk TP53-mutated MDS patient has now reached the one-year mark following treatment with TSC-101. Additionally, no patient-derived hematopoietic cells were detected in any of the eight treatment-arm patients, indicating complete elimination of target cells. One AML patient with detectable disease post-transplant converted to, and continues to show, no detectable disease following treatment with TSC-101, with the most recent measurement at day 180. Patients have now been enrolled up to the third and final dose level in both treatment arms with no dose limiting toxicities thus far, suggesting that the third dose level will likely become the recommended Phase 2 dose.Of the six patients enrolled in the control arm (transplant alone), two control-arm patients relapsed at day 161 and day 180, and one of them succumbed to the relapse on day 265 post-transplant. A third control-arm patient required clinical intervention on day 133 because of concerns of impending relapse, and only two of the control-arm patients achieved and maintained complete donor chimerism following transplantation.The Company hosted a virtual KOL event following the Tandem Meetings to discuss these data. A replay of the event can be found here. The Company recently received U.S. Food and Drug Administration (FDA) clearance of its investigational new drug (IND) applications for two additional TCR-Ts in their Solid Tumor Program: TSC-201-B0702, a TCR-T targeting melanoma-associated antigen C2 (MAGE-C2) on HLA -B*07:02TSC-204-A0101, a TCR-T targeting melanoma-associated antigen 1 (MAGE-A1) on HLA-A*01:01 With the clearance of these IND applications, TScan now has six enhanced TCR-Ts cleared for clinical development. The Company remains on-track to dose the first patient in its Phase 1 solid tumor program in the first quarter of 2024 and anticipates sharing initial data on patients from both the singleplex and multiplex cohorts in 2024. The Company will present two “Trials in Progress” poster presentations at the upcoming American Association for Cancer Research (AACR) Annual Meeting 2024. Details for the posters include: 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 transplantationSession Title: Phase I Clinical Trials in Progress 2Session Date and Time: Monday April 8, 2024; 1:30 - 5:00 PM PDTLocation: Poster Section 50Poster Board Number: 2Abstract Presentation Number: CT151 Title: Trial in progress: A phase 1, first in human clinical trial for T-Plex, a multiplexed, enhanced T cell receptor-engineered T cell therapy (TCR-T) for solid tumorsSession Title: Phase I Clinical Trials in Progress 2Session Date and Time: Monday April 8, 2024; 1:30 - 5:00 PM PDTLocation: Poster Section 50Poster Board Number: 21Abstract Presentation Number: CT170 The Company continues to expand its leadership team with key appointments and promotions: Appointed Jason A. Amello as Chief Financial OfficerAppointed Justin McCue, Ph.D., as Chief Technology OfficerPromoted Zoran Zdraveski, J.D., Ph.D., to Chief Legal and Strategy OfficerAppointed R. Keith Woods to its Board of DirectorsPromoted Cagan Gurer, Ph.D., to Senior Vice President, DiscoveryPromoted Jim Murray to Senior Vice President, Head of Development OperationsAppointed Dawn Pinchasik, M.D., M.S., as Vice President, Clinical Development In November 2023, the Company was named a Top Place to Work by The Boston Globe for the second consecutive year. Upcoming Anticipated Milestones Heme Malignancies Program: TScan’s two lead TCR-T cell therapy candidates, TSC-100 and TSC-101, are designed to treat residual disease and prevent relapse in patients with acute myeloid leukemia (AML), acute lymphocytic leukemia (ALL), or myelodysplastic syndromes (MDS) undergoing hematopoietic cell transplantation (HCT) (NCT05473910). Plans to open expansion cohorts at the recommended Phase 2 dose level to further characterize safety and evaluate translational and efficacy endpoints in the third quarter of 2024.Plans to complete Phase 1 enrollment and report one-year clinical and translational data on initial patients in 2024.Expects to initiate registration trial and report two-year relapse data in 2025. Solid Tumor Program: TScan continues to expand the ImmunoBank, a collection of therapeutic TCRs that target different cancer-associated antigens presented on diverse HLA types. TScan’s strategy is to treat patients with multiple TCR-Ts to overcome tumor heterogeneity and prevent resistance that may arise from either target or HLA loss (screening protocol: NCT05812027) (treatment protocol: NCT05973487). Initiated Phase 1 solid tumor clinical study and expects to dose the first patient in the first quarter of 2024.Expects to share initial data on patients from both singleplex and multiplex cohorts in 2024.Plans to continue to expand the ImmunoBank with additional IND filings throughout 2024.Long-term duration of response data for multiplexed therapy anticipated in 2025. Financial Results Revenue: Revenue for the fourth quarter of 2023, was $7.2 million, compared to $3.1 million for the fourth quarter of 2022, and $21.0 million for the full-year 2023, compared to $13.5 million for the full-year 2022. The increase in both periods is primarily due to timing of research activities related to the collaboration agreement with Amgen which commenced in May 2023 compared to the collaboration and license agreement with Novartis which ended in March 2023. R&D Expenses: Research and development expenses for the fourth quarter of 2023 were $22.4 million, compared to $15.6 million for the fourth quarter of 2022, and $88.2 million for the full-year 2023, compared to $59.8 million for the full-year 2022. The period over period increases were primarily driven by increased costs associated with clinical trial start-up fees and patient enrollment, increased personnel costs, and expansion of facilities. G&A Expenses: General and administrative expenses for the fourth quarter of 2023, were $6.2 million, compared to $6.1 million for the fourth quarter of 2022, and $26.4 million for the full-year 2023, compared to $20.4 million for the full-year 2022. The full-year increase of $6.0 million was primarily driven by increased legal and professional fees and expansion of facilities. Net Loss: Net loss was $19.6 million for the fourth quarter of 2023, compared to $18.7 million for the fourth quarter of 2022, and included net interest income of $1.7 million and $0, respectively. Net loss for the full-year 2023 was $89.2 million, compared to $66.2 million for the full-year 2022, and included net interest income of $4.2 million and $0.4 million, respectively. Cash Position: Cash, cash equivalents, and marketable securities as of December 31, 2023 were $192.0 million, excluding $5.0 million of restricted cash. The Company believes that its existing cash resources will be sufficient to fund its current operating plan into 2026. Share Count: As of December 31, 2023, the Company had issued and outstanding shares of 47,829,529, which consists of 43,552,941 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 prevent relapse following allogeneic hematopoietic cell transplantation. The Company is also developing TCR-T therapy candidates for the treatment of various solid tumors. The Company has developed and continues to expand 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 cancers. 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 potential indicators of treatment success, completion of enrollment and opening of expansion cohorts, and the presentation of data; the Company’s plans, progress, and timing relating to the Company’s solid tumor programs, including treatment of patients and the presentation of data; 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 ability to fund its operating expenses and capital expenditure requirements with its existing cash and cash equivalents; and the Company’s goals and strategy, focus, 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,” “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 recently approved INDs being indicative or predictive of bringing TScan closer to its goal of providing customized TCR-T therapies to treat patients with cancer; the timing of the launch, initiation, progress, 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(in thousands) December 31,2023 December 31, 2022 Assets Cash, cash equivalents, and marketable securities$192,044 $120,027 Other assets 80,105 79,064 Total assets$272,149 $199,091 Liabilities and Stockholders' Equity Total liabilities$121,282 $99,657 Total stockholders' equity 150,867 99,434 Total liabilities and stockholders' deficit$272,149 $199,091 TScan Therapeutics, Inc.Condensed Consolidated Statements of Operations(in thousands, except share and per share amounts) Three Months Ended December 31, Twelve Months Ended December 31, 2023 2022 2023 2022 Revenue: Collaboration and license revenue$7,211 $3,096 $21,049 $13,535 Operating expenses: Research and development 22,407 15,604 88,153 59,819 General and administrative 6,161 6,140 26,354 20,352 Total operating expenses 28,568 21,744 114,507 80,171 Loss from operations (21,357) (18,648) (93,458) (66,636)Other income 2,596 900 7,999 1,591 Interest expense (852) (975) (3,759) (1,176)Net loss$(19,613) $(18,723) $(89,218) $(66,221)Net loss per share, basic and diluted$(0.21) $(0.78) $(1.36) $(2.75)Weighted average common shares outstanding—basic and diluted 94,835,735 24,077,857 65,599,858 24,048,267

Reported positive initial data from Phase 1 heme program at the 65th American Society of Hematology (ASH) Annual Meeting Clearance of INDs for four TCR-Ts, including a TCR-T for PRAME, in support of use of multiple TCRs in combination for the solid tumor clinical trial Entered a collaboration with Amgen to identify novel targets in Crohn’s Disease Closed underwritten public offering with net proceeds of $140.6 million, funding operations into 2026 WALTHAM, Mass., Jan. 04, 2024 (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 its 2024 clinical pipeline plans and highlighted recent corporate achievements. “2023 was a pivotal year for TScan, most recently marked by the Phase 1 heme malignancies data presented at the ASH Annual Meeting on six treatment arm patients and four control arm patients. We are encouraged to see complete donor chimerism and MRD negativity achieved and maintained in all six treated patients, with a median follow-up of over six months,” said Gavin MacBeath, Ph.D., Chief Executive Officer. “Over the course of the year we also continued to build our ImmunoBank for the treatment of solid tumors. We have now cleared INDs for four TCRs, including TCRs for PRAME, HPV16, and MAGE-A1, and have regulatory clearance to treat patients with multiple TCRs sequentially in our Phase 1 study. Additionally, we submitted INDs for two additional TCRs in December and the 30-day review period with the FDA is ongoing. We look forward to dosing the first patient in the Phase 1 solid tumor clinical study in the first quarter and reporting clinical data, initially on patients treated with singleplexed therapy, and then on patients treated with multiplexed therapy, in 2024.” “The data from our heme program presented at ASH is a true testament to the progress we made over the past year. We have now enrolled and dosed patients up to the third and final dose level with no DLTs observed to date and no safety signals thus far, indicating that the third dose level will likely be the recommended Phase 2 dose,” added Debora Barton, M.D., Chief Medical Officer. “We plan to activate additional sites and provide clinical updates at major medical meetings throughout the year. Upon establishing the recommended Phase 2 dose, we plan to open expansion cohorts at that dose to further characterize safety and evaluate translational and efficacy endpoints.” 2023 Key Achievements and Recent Company Highlights Heme Malignancies Program: TScan’s two lead TCR-T cell therapy candidates, TSC-100 and TSC-101, are designed to treat residual disease and prevent relapse in patients with acute myeloid leukemia (AML), acute lymphocytic leukemia (ALL), or myelodysplastic syndromes (MDS) undergoing hematopoietic cell transplantation (HCT) (NCT05473910). Recently presented initial Phase 1 clinical results at the 65th American Society of Hematology (ASH) Annual Meeting. Highlights from the poster included: No relapses have occurred in six of six treatment-arm patients, four with follow-up past six months; one of four control-arm patients relapsed at six months and two others required clinical intervention for increasing mixed chimerism.No patient-derived hematopoietic cells were detected in six of six treatment-arm patients, indicating complete elimination of target cells, versus zero of four control-arm patients.An AML patient with detectable disease post-transplant converted to no detectable disease following treatment with TSC-101.Patients were enrolled up to the third and final dose level in both treatment arms with no dose limiting toxicities. Solid Tumor Program: TScan continues to build the ImmunoBank, a collection of therapeutic TCRs that target different cancer-associated antigens presented on diverse HLA types. TScan’s strategy is to treat patients with multiple TCR-Ts sequentially to overcome tumor heterogeneity and prevent resistance that may arise from either target or HLA loss (screening protocol: NCT05812027) (treatment protocol: NCT05973487). Continued to build the ImmunoBank with U.S. Food and Drug Administration (FDA) clearance of five investigational new drug applications (INDs): T-Plex IND supports the sequential use of multiple TCRs to deliver customized, multiplexed TCR-T cell therapies based on target and HLA expression.TSC-200-A0201 targets HPV16 on HLA type A*02:01.TSC-203-A0201 targets PReferentially expressed Antigen in MElanoma (PRAME) on HLA type A*02:01.TSC-204-A0201 and TSC-204-C0702 target melanoma-associated antigen 1 (MAGE-A1) on HLA types A*02:01 and C*07:02, respectively.Filed INDs in December 2023 for TSC-201-B0702 targeting melanoma-associated antigen C2 (MAGE-C2) on HLA type B*07:02 and TSC-204-A0101 targeting MAGE-A1 on HLA type A*01:01; 30-day review period ongoing. 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. Corporate and Financial Highlights: Appointed Gavin MacBeath, Ph.D., as Chief Executive Officer and as a member of the Board of Directors.Appointed Justin McCue, Ph.D., as Chief Technology Officer.Appointed Barbara Klencke, M.D., and R. Keith Woods to the Board of Directors.Entered into a collaboration with Amgen to identify novel targets in Crohn’s Disease. TScan received $30 million upfront and is eligible to earn over $500 million in success-based milestones as well as tiered single-digit royalty payments.Closed underwritten public offering with gross proceeds of $140.6 million, funding operations into 2026.TScan named as a Top Place to Work for two consecutive years by The Boston Globe. Upcoming Anticipated Milestones Heme Malignancies Program: Plans to complete Phase 1 dosing and report clinical and translational data in 2024, and two-year relapse data in 2025.Plans to open expansion cohorts at the recommended Phase 2 dose level to further characterize safety and evaluate translational and efficacy endpoints.Expects to initiate registration trial in 2025. Solid Tumor Program: Initiated Phase 1 solid tumor clinical study and expects to dose the first patient in the first quarter of 2024.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.Plans to continue to build ImmunoBank with additional IND filings throughout 2024.Long-term duration data for multiplexed therapy anticipated in 2025. 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 cancers. 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 the completion of Phase 1 dosing, reporting of data, opening expansion cohorts, and initiation of registrational trial; the Company’s plans, progress, and timing relating to the Company’s solid tumor program, including dosing of patients, reporting of data, and filing of INDs; 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

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