10-K

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UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

FORM 10-K

(Mark One)

For the fiscal year ended December 31, 2024

Commission File Number 001-40603

TScan Therapeutics, Inc.

(Exact name of Registrant as specified in its Charter)

830 Winter StreetWaltham, Massachusetts 02451

(Address of principal executive offices) (Zip Code)

Registrant’s telephone number, including area code: (857) 399-9500

Securities registered pursuant to Section 12(b) of the Act:

Title of each class TradingSymbol(s) Name of each exchange on which registered

Securities registered pursuant to Section 12(g) of the Act: None

Indicate by check mark if the Registrant is a well-known seasoned issuer, as defined in Rule 405 of the Securities Act. YES ☐No☒

Indicate by check mark if the Registrant is not required to file reports pursuant to Section 13 or 15(d) of the Act. YES ☐No☒

Indicate by check mark whether the Registrant: (1) has filed all reports required to be filed by Section 13 or 15(d) of the Securities Exchange Act of 1934 during the preceding 12 months (or for such shorter period that the Registrant was required to file such reports), and (2) has been subject to such filing requirements for the past 90 days. Yes☒ NO ☐

Indicate by check mark whether the Registrant has submitted electronically every Interactive Data File required to be submitted pursuant to Rule 405 of Regulation S-T (§232.405 of this chapter) during the preceding 12 months (or for such shorter period that the Registrant was required to submit such files). Yes☒ NO ☐

Indicate by check mark whether the registrant is a large accelerated filer, an accelerated filer, a non-accelerated filer, 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.

Large accelerated filer ☐ Accelerated filer ☐

Non-accelerated filer ☒ Smaller reporting company ☒

Emerging growth company ☒

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 13(a) of the Exchange Act. ☐

Indicate by check mark whether the registrant has filed a report on and attestation to its management’s assessment of the effectiveness of its internal control over financial reporting under Section 404(b) of the Sarbanes-Oxley Act (15 U.S.C. 7262(b)) by the registered public accounting firm that prepared or issued its audit report. ☐

If securities are registered pursuant to Section 12(b) of the Act, indicate by check mark whether the financial statements of the registrant included in the filing reflect the correction of an error to previously issued financial statements. ☐

Indicate by check mark whether any of those error corrections are restatements that required a recovery analysis of incentive-based compensation received by any of the registrant’s executive officers during the relevant recovery period pursuant to §240.10D-1(b). ☐

Indicate by check mark whether the Registrant is a shell company (as defined in Rule 12b-2 of the Exchange Act). YES ☐ NO ☒

The aggregate market value of the voting and non-voting common equity held by non-affiliates of the Registrant, based on the closing price of the shares of common stock on The Nasdaq Global Market, LLC on June 30, 2024, was $201,649,026.

The number of shares of Registrant’s Common Stock outstanding as of February 28, 2025 was 52,314,039 shares of voting common stock, $0.0001 par value per share, outstanding and 4,276,588 shares of non-voting common stock, $0.0001 par value per share, outstanding.

DOCUMENTS INCORPORATED BY REFERENCE

None.

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Page

PART I.

Item 1. Business 6

Item 1A. Risk Factors 48

Item 1B. Unresolved Staff Comments 107

Item 1C. Cybersecurity 107

Item 2. Properties 108

Item 3. Legal Proceedings 108

Item 4. Mine Safety Disclosures 108

PART II.

Item 6. [Reserved] 109

Item 7A. Quantitative and Qualitative Data About Market Risk 120

Item 8. Financial Statements and Supplementary Data 120

Item 9A. Controls and Procedures 120

Item 9B. Other Information 121

PART III.

Item 10. Directors, Executive Officers and Corporate Governance 122

Item 11. Executive Compensation 127

Item 14. Principal Accounting Fees and Services 138

PART IV.

Item 15. Exhibits, Financial Statement Schedules 140

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SPECIAL NOTE REGARDING FORWARD-LOOKING STATEMENTS

This Annual Report on Form 10-K, or Annual Report, contains forward-looking statements within the meaning of Section 27A of the Securities Act of 1933, as amended, and Section 21E of the Securities Exchange Act of 1934, as amended, or the Exchange Act, that involve substantial risks and uncertainties. All statements, other than statements of historical facts, contained in this Annual Report are forward-looking statements.

In some cases, you can identify forward-looking statements by words such as “may,” “can,” “will,” “should,” “would,” “expect,” “plan,” “anticipate,” “could,” “intend,” “target,” “project,” “seek,” “contemplate,” “believe,” “estimate,” “predict,” “potential,” “possible” or “continue” or the negative of these terms or other similar expressions are intended to identify forward-looking statements, although not all forward-looking statements contain these identifying words. Forward-looking statements contained in this Annual Report include, but are not limited to, statements about:

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the beneficial characteristics, safety, efficacy, therapeutic effects and potential advantages of our T cell receptor (TCR)-engineered T cell, or TCR-T, therapy product candidates;

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our expectations regarding our preclinical studies being predictive of clinical trial results;

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the timing of the initiation, progress and expected results of our preclinical studies, clinical trials and our research and development programs;

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the timing of and our ability to submit applications for, and obtain and, if approved, maintain regulatory approvals for our TCR-T therapy product candidates;

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our expectations regarding clinical trial results being predictive of continued development and commercial success of our product candidates;

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our plans relating to developing and commercializing our TCR-T therapy product candidates, if approved, including sales strategy;

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estimates of the size of the addressable market for our TCR-T therapy product candidates;

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our manufacturing capabilities and the scalable nature of our manufacturing process;

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our estimates regarding expenses, future milestone payments and revenue, capital requirements and needs for additional financing;

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our expectations regarding competition;

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our anticipated growth strategies;

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our ability to attract or retain key personnel;

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our ability to establish and maintain development partnerships and collaborations;

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our expectations regarding federal, state and foreign regulatory requirements;

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regulatory developments in the U.S. and foreign countries;

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our ability to obtain and maintain intellectual property protection for our proprietary platform technology and our product candidates;

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the anticipated trends and challenges in our business and the market in which we operate;

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the sufficiency of our existing capital resources to fund our future operating expenses and capital expenditure requirements;

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the effects of any public health crises in regions where we, our partners, or other third parties on which we rely, on any of the foregoing or other aspects of our business or operations;

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the effects of rising inflation rates and the impact on operating costs, liquidity and access to credit on any of the foregoing or other aspects of our business operations;

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the effects of global economic uncertainty and financial market volatility caused by political instability, or new or increased international tariffs, changes in U.S. policy, changes in international trade relationships and conflicts, such as the ongoing conflict between Russia and Ukraine, on any of the foregoing or other aspects of our business or operations including our ability to obtain additional financing; and

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our anticipated use of our existing cash resources and our ability to obtain additional financing in the future.

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Any forward-looking statements in this Annual Report reflect our current views with respect to future events or to our future financial performance and involve known and unknown risks, uncertainties and other important factors that may cause our actual results, performance or achievements to be materially different from any future results, performance or achievements expressed or implied by these forward-looking statements. These forward-looking statements are subject to a number of risks, uncertainties and assumptions included in this Annual Report, particularly those described in the “Risk Factors” section in Part I, Item 1A of this Annual Report, that could cause actual results or events to differ materially from the forward-looking statements that we make. Moreover, we operate in a very competitive and rapidly changing environment. New risks emerge from time to time and it is not possible for our management to predict all risks, nor can we assess the impact of all factors on our business or the extent to which any factor, or combination of factors, may cause actual results to differ materially from those contained in any forward-looking statements we may make. We may not actually achieve the plans, intentions or expectations disclosed in our forward-looking statements, and you should not place undue reliance on our forward-looking statements. In light of these risks, uncertainties and assumptions, the forward- looking events and circumstances discussed in this Annual Report may not occur and actual results could differ materially and adversely from those anticipated or implied in the forward-looking statements.

You should not rely upon forward-looking statements as predictions of future events. The forward-looking statements contained in this Annual Report are made as of the date of this Annual Report, and although we believe that the expectations reflected in the forward-looking statements are reasonable, we cannot guarantee that the future results, advancements, discoveries, levels of activity, performance or events and circumstances reflected in the forward-looking statements will be achieved or occur. Moreover, except as required by law, neither we nor any other person assumes responsibility for the accuracy and completeness of the forward-looking statements. We undertake no obligation to update publicly any forward-looking statements for any reason after the date of this Annual Report to conform these statements to actual results or to changes in our expectations.

You should read this Annual Report and the documents that we have filed as an exhibit to this Annual Report with the understanding that our actual future results, levels of activity, performance and events and circumstances may be materially different from what we expect.

In addition, this Annual Report contains estimates, projections and other information concerning our industry, our business and the markets for our product candidates, including data regarding the estimated size of such markets and the incidence of certain medical conditions. We obtained the industry, market and similar data set forth in this Annual Report from our internal estimates and research, and from academic and industry research, publications, surveys and studies conducted by third parties, including governmental agencies. Industry publications and third-party research, surveys and studies generally indicate that their information has been obtained from sources believed to be reliable. Our estimates of the potential market opportunities for our product candidates include a number of key assumptions based on our industry knowledge, industry publications and third-party research, surveys and studies, which may be based on a small sample size and fail to accurately reflect market opportunities. Information based on estimates, forecasts, projections, market research or similar methodologies is inherently subject to uncertainties and actual events or circumstances may differ materially from events and circumstances that are assumed in this information. Unless otherwise expressly stated, we obtained this industry, business, market and other data from reports, research surveys, studies and similar data prepared by us and third parties, industry, medical and general publications, government data and similar sources. This Annual Report contains summaries of certain provisions contained in some of the documents described herein, but reference is made to the actual documents for complete information. All of the summaries are qualified in their entirety by the actual documents.

Unless stated otherwise, references in this Annual Report to “us,” “we,” “our,” “our Company,” or “the Company” and similar terms refer to TScan Therapeutics, Inc.

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RISK FACTOR SUMMARY

Our business operations are subject to numerous risks that, if realized, could materially and adversely affect our business, financial condition, results of operations, and future growth prospects. These risks are discussed more fully in Part I, Item 1A. “Risk Factors” in this Annual Report on Form 10-K. These risks include, but are not limited to, the following:

Risks Related to Our Business and Industry

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We have incurred significant losses since inception, and we expect to incur losses over the next several years and may not be able to achieve or sustain revenues or profitability in the future.

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Our business depends upon the success of our proprietary platform.

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Our limited operating history may make it difficult to evaluate the success of our business to date and to assess our future viability.

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We have never generated any revenue from sales of our TCR-T therapy product candidates, and our ability to generate revenue from product sales and become profitable depends significantly on our success in a number of areas.

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We will need to obtain substantial additional funding to complete the development and any commercialization of our product candidates, if approved. If we are unable to raise this necessary capital when needed, we could be forced to delay, reduce or eliminate our product development programs, commercialization efforts or other operations.

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Raising additional capital may cause dilution to our existing stockholders, restrict our operations or require us to relinquish rights to our intellectual property or product candidates on unfavorable terms to us.

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Global economic uncertainty and financial market volatility caused by political instability, changes in international trade relationships and conflicts could make it more difficult for us to access financing and could adversely affect our business and operations.

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The U.S. Congress or the Trump administration, may make substantial changes to fiscal, tax, and other federal policies that may adversely affect our business.

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Recent volatility in capital markets and lower market prices for many securities may affect our ability to access new capital through sales of shares of our common stock or issuance of indebtedness, which may impact our liquidity, limit our ability to grow our business, pursue acquisitions or improve our operating infrastructure and restrict our ability to compete in our markets.

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Adverse developments affecting the financial services industry, such as actual events or concerns involving liquidity, defaults or non-performance by financial institutions or transactional counterparties, could adversely affect our current and projected business operations and its financial condition and results of operations.

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The terms of our loan agreement place restrictions on our operating and financial flexibility. If we raise additional capital through debt financing, the terms of any new debt could further restrict our operating and financial flexibility.

Risks Related to the Development of Our Product Candidates

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Our approach to the discovery and development of product candidates based on our proprietary platform represents a novel approach to cancer treatment, which creates significant challenges for us.

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We are early in our development efforts. If we are unable to advance our product candidates through clinical development, obtain regulatory approval and ultimately commercialize our product candidates, or experience significant delays in doing so, our business will be materially harmed.

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Although many of our personnel have extensive experience in clinical development and manufacturing at other companies, we have limited direct experience as a company in conducting clinical trials and managing a manufacturing facility for our product candidates.

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Our preclinical studies and clinical trials may fail to demonstrate adequately the safety, potency and purity of any of our product candidates, which would prevent or delay development, regulatory approval and commercialization.

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Our business could be adversely affected by the effects of health epidemics in regions where we, our partners or other third parties on which we rely have significant manufacturing facilities, concentrations of potential clinical trial sites or other business operations.

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We may rely on third parties to manufacture our clinical product supplies, and we may rely on third parties to produce and process our product candidates, if licensed.

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We cannot guarantee that our product candidates will show any functionality in the solid tumor microenvironment.

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Allogeneic hematopoietic cell transplantation (HCT) is a high-risk procedure that may result in complications or adverse events for patients in our clinical trials including those unrelated to the use of our product candidates.

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Our product candidates may cause undesirable side effects or have other properties that could halt their clinical development, prevent their regulatory approval, require expansion of the trial size, limit their commercial potential, or result in other significant negative consequences.

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If we encounter difficulties enrolling patients in our clinical trials, our clinical development activities could be delayed or otherwise adversely affected.

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The market opportunities for our product candidates may be relatively small. In addition, our estimates of the prevalence of our target patient populations may be inaccurate.

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We face significant competition, and our operating results will suffer if we fail to compete effectively.

Risks Related to Manufacturing

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Manufacturing and administering our product candidates is complex and we may encounter difficulties in production, particularly with respect to process development or scaling up of our manufacturing capabilities. If we encounter such difficulties, our ability to provide supply of our TCR-T therapy product candidates for clinical trials or for commercial purposes could be delayed or stopped.

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Although many of our personnel have experience in clinical manufacturing at other companies, we have limited experience as a company managing manufacturing for our product candidates, which will be costly and time-consuming, and which may not be successful.

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We may have difficulty validating our manufacturing process as we manufacture TCR-T therapy product candidates from an increasingly diverse patient population for our clinical trials.

Risks Related to Government Regulation

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The regulatory approval process is lengthy and time-consuming, and we may experience significant delays in the clinical development and regulatory approval of our product candidates.

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We may be unable to obtain regulatory approval for our product candidates under applicable regulatory requirements. The denial or delay of any such approval would delay commercialization of our product candidates and adversely impact our potential to generate revenue, our business and our results of operations.

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Obtaining and maintaining regulatory approval of our product candidates in one jurisdiction does not mean that we will be successful in obtaining regulatory approval of our product candidates in other jurisdictions.

Risks Related to Our Intellectual Property

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If we are unable to obtain and maintain patent protection for any product candidates we develop and for our technology, or if the scope of the patent protection obtained is not sufficiently broad, our competitors could develop and commercialize products, product candidates and technology similar or identical to ours, and our ability to successfully commercialize any product candidates we may develop and our technology may be adversely affected.

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We are currently, and expect in the future to be, party to material license or collaboration agreements, which may impose numerous obligations and restrictions on us.

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Third-party claims of intellectual property infringement, misappropriation or other violations may prevent or delay our product candidate discovery and development efforts.

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Risks Related to Our Reliance on Third Parties

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We rely on third parties to conduct our clinical trials. If these third parties do not properly and successfully carry out their contractual duties or meet expected deadlines, we may not be able to obtain regulatory approval of or commercialize our product candidates.

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We have in the past and may in the future form or seek collaborations or strategic alliances or enter into additional licensing arrangements, and we may not realize the benefits of such collaborations, alliances or licensing arrangements.

General Risk Factors

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Rising inflation rates may result in increased operating costs and reduced liquidity and affect our ability to access credit.

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PART I

Item 1. Business

Overview

We are a clinical-stage biotechnology company focused on developing a robust pipeline of T cell receptor (TCR)-engineered T cell, or TCR-T, therapies for the treatment of patients with cancer. Our approach is based on the central premise that we can learn from patients who are winning their fight against cancer to treat those who are not. Over the past several years, we have built our ImmunoBank, a repository of therapeutic TCRs that recognize diverse targets and are associated with multiple human leukocyte antigen, or HLA, types. We then use these TCRs to manufacture enhanced TCR-T therapies to treat a broad population of patients with both hematologic, or heme, and solid tumor malignancies. Every TCR in our ImmunoBank has come from our proprietary platform technologies, and we are continuing to expand our ImmunoBank.

We are advancing a robust pipeline of TCR-T therapy product candidates for the treatment of patients with heme malignancies and solid tumors. Our lead product candidates, TSC-100 and TSC-101, are in development for the treatment of patients with acute myeloid leukemia (AML), myelodysplastic syndrome (MDS), and acute lymphoblastic leukemia (ALL), who are undergoing allogeneic hematopoietic cell transplantation (HCT). The products are designed to eliminate residual disease and promote complete donor chimerism, thereby preventing relapse. TSC-100 and TSC-101 target the antigens HA-1 and HA-2, respectively, which are well-recognized TCR targets that were first identified in patients with exceptional responses to HCT-associated immunotherapy. We are currently conducting a multi-arm Phase 1 "umbrella" clinical study of TSC-100 and TSC-101, the ALLOHATM Phase 1 heme trial, with 15 clinical sites activated, and we plan to open additional sites before the end of 2025.

In addition, we are developing multiple TCR-T therapy product candidates for the treatment of solid tumors. One of the challenges of treating solid tumors is that they are heterogeneous – not every tumor cell expresses a given target and some tumor cells lose half their HLA genes. To address this challenge, we are developing what we refer to as multiplex TCR-T therapy, or T-Plex, in which we treat a patient with more than one TCR-T therapy product candidate at a time. We are designing these multiplex therapies to be a simultaneous administration of up to three highly active TCR-T therapy product candidates, selected from our ImmunoBank, that are customized for each patient based on which targets are expressed in their tumors and which HLA genes are still intact. We continue to prioritize expanding the ImmunoBank with TCRs for additional targets and multiple HLA types for each target. We have now advanced seven TCR-T therapy product candidates into Phase 1 development for solid tumors: TSC-203-A0201 (PRAME, HLA-A*02:01); TSC-200-A0201 (HPV16, HLA-A*02:01); TSC-201-B0702 (MAGE-C2, HLA-B*07:02); TSC-202-A0201 (MAGE-A4, HLA-A*02:01); TSC-204-A0201 (MAGE-A1, HLA-A*02:01); TSC-204-C0702 (MAGE-A1, HLA-C*07:02); and TSC-204-A0101 (MAGE-A1, HLA-A*01:01). In addition to clearing these seven solid-tumor investigational new drug (IND) applications, the U.S. Food and Drug Administration (FDA) has cleared our IND application for T-Plex, enabling us to treat patients with multiplex TCR-T therapy. We plan to further expand the ImmunoBank by filing IND applications for additional TCR-T therapy product candidates. We have initiated a Phase 1 solid tumor clinical trial, the PLEXI-TTM trial, with 15 clinical sites activated, and we plan to open additional sites before the end of 2025.

We have an internal good manufacturing practices, or GMP, facility to manufacture clinical supply for our TCR-T therapy product candidates. This facility allows us to rapidly, cost-effectively, and consistently manufacture our TCR-Ts. Our TCR-T therapy product candidates are manufactured using a non-viral transposon/transposase system. This non-viral platform approach can be rapidly applied to new TCR-T therapy product candidates in a cost-effective manner without the need for extensive process development. The larger cargo capacity of our non-viral vector delivery system allows us to include additional T cell enhancements in our product candidates. In both our heme and solid tumor programs, we are introducing the gene for CD8α/β along with the TCR gene, which enables us to engineer both cytotoxic and helper T cells with our TCRs. We believe this enhancement has the potential to improve responses to TCR-T therapy in the clinic compared to engineering cytotoxic T cells alone. In our solid tumor program, we are also adding a dominant-negative (DN) form of TGFβRII to our T cells, which enables them to proliferate despite the presence of TGFβ in the hostile tumor microenvironment. This has the potential to enhance T cell persistence. Our GMP facility has the estimated capacity to manufacture clinical trial materials for up to 250 TCR-T components per year. To further increase our existing clinical manufacturing capacity and prepare for potential commercialization, we have engaged a global contract development and manufacturing organization, or CDMO, with worldwide commercial capabilities to support both the heme and solid tumor programs. The CDMO is on track to add capacity and to support additional clinical manufacturing of the heme program in the second half of 2025.

T cells are an essential component of the adaptive immune system and provide protection against cancer, infection, and autoimmune disorders. Multiple approaches have been and are continuing to be explored to develop effective T cell-based therapies for the treatment of cancer, including checkpoint inhibitor therapy, tumor infiltrating lymphocyte, or TIL, therapy, and chimeric antigen receptor (CAR) T cell, or CAR-T, therapy. The success of checkpoint inhibitor and TIL therapy depends on the specific T-cells present in the patient. If their T-cells do not have appropriate anti-cancer specificities, the therapy is unlikely to be effective. In addition, TIL therapy has, to date, shown limited applicability for the treatment of heme malignancies. In contrast, CAR-T therapy has proven effective

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in certain heme malignancies of lymphoid origin but has shown only limited activity in myeloid malignancies or solid tumors. To address a broader patient population, we believe additional T cell-based approaches are needed that more closely mimic the way the immune system recognizes and fights cancer.

The successful development of TCR-T therapy product candidates has three key prerequisites: (i) an effective anti-cancer TCR; (ii) knowledge of the precise peptide antigen that is recognized by the TCR; and (iii) confirmation that the TCR does not recognize problematic off-targets. We believe our approach provides us with the following key advantages:

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Our TCR-T therapy product candidates are based on highly active TCRs that are clinically relevant. Many other approaches to T cell therapy rely onspecifically expanding T cells that are already present in the patient. Our platform analyzes anti-cancer T cells from a broad set of individuals, including patients responding to immunotherapy as well as healthy donors, to find the most active and clinically relevant TCRs against each target. We believe that we can develop TCR-T therapy product candidates for a wide range of patients, including those who do not have T cells that efficiently recognize their cancers.

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Our TCR-T therapy product candidates are designed to be used in combination with each other. We have built the ImmunoBank of TCRs to allow formultiplexed TCR-T therapy, which has the potential to address the heterogeneous nature of solid tumors and address resistance due to target or HLA loss. We continue to expand the ImmunoBank with TCRs for additional targets as well as multiple common HLA types for each target.

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Our approach is expandable. TheImmunoBank has the flexibility to be used with new and optimized methods of T cell engineering that we maydevelop over time. We are currently employing the validated approach of patient-specific ex vivo engineering, but as the field evolves, our TCRs may be transitioned to "off-the-shelf" methods, including allogeneic T cells or in vivo engineering. As we expand the ImmunoBank to include TCRs across additional targets and HLA types, we believe we will increase the eligible patient population for our clinical trials, which will allow for rapid and efficient clinical trial enrollment with fewer screen failures.

Our Pipeline

In addition, we are developing multiple TCR-T therapy product candidates for the treatment of various solid tumors. We have developed and continue to expand the ImmunoBank with the goal of delivering customized multiplex TCR-T therapy to a wide range of patients with cancer. Our current proprietary pipeline is summarized in the figure below.

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In addition to our proprietary pipeline programs noted above, we have also entered into collaborations with strategic partners for applications of our platform technologies. We have a collaboration with Amgen Inc., or Amgen, to identify the antigens recognized by T cells in patients with Crohn's disease. Amgen will evaluate a variety of modalities to create therapeutic candidates based on targets discovered by TScan and will retain all global development and commercial rights.

With our differentiated platform as the foundation, we are building a three-pillar research and development strategy to create transformational TCR-T therapy product candidates for patients.

Our Heme Program. We are developing TCR-T therapy product candidates to treat patients with heme malignancies, including AML, MDS, and ALL who are undergoing allogeneic HCT. In the first phase of our clinical development strategy, we are initially focusing on clinically validated cancer targets that have been discovered in patients with exceptional responses to HCT-associated immunotherapy, including HA-1 and HA-2. Additionally, we are planning to expand our heme program to include additional HLA types. We have now advanced TSC-102-A0301, which targets an HLA-A*03:01-restricted epitope on CD45, into IND-enabling activities.

We are currently enrolling patients in a multi-arm Phase 1 "umbrella" clinical study with 15 clinical sites activated and additional sites planned to be opened in 2025. The study protocol allows us to conduct clinical trials of TSC-100 and TSC-101 in parallel, with patients enrolled in treatment arms based on their genotype. Patients who are positive for the target antigen, HA-1 or HA-2, as well as the HLA-A*02:01 allele, which is the HLA type required to display HA-1 and HA-2 on the cell surface for recognition by a T cell, are eligible for enrollment. Eligible patients require donors who are negative for either the target antigen or the HLA-A*02:01 allele.

Through the development of our heme malignancies program, we have built a foundation of manufacturing, clinical, and regulatory capabilities, which we are also applying to the development of our broader portfolio of TCR-T therapy product candidates for solid tumors.

Our Solid Tumor Program. We are developing a portfolio of autologous TCR-T therapy product candidates designed to be used in combination with each other to treat and eliminate solid tumors. Our solid tumor product candidates are designed to elicit anti-tumor responses in patients by targeting cancer-specific antigens in their tumor cells. Our TCR-T therapy product candidates include: (i) well-recognized cancer targets that have demonstrated anti-tumor activity in clinical trials as well as novel targets that were identified by TargetScan from the T cells of patients responding to immunotherapy, and (ii) naturally occurring TCRs specific to a patient’s HLA type that recognize these cancer-specific targets. Such targets are not only commonly shared among patients with the same cancer type, but also frequently expressed in multiple solid tumor types, enabling clinical development across multiple indications. Our first seven product candidates address known and novel targets: E7 of HPV16 for TSC-200-A0201, MAGE-C2 for TSC-201-B0702, MAGE-A4 for TSC-202-A0201, PRAME for TSC-203-A0201, and MAGE-A1 for TSC-204-A0201, TSC-204-C0702, and TSC-204-A0101.

We have built and continue to expand the ImmunoBank to enable customized multiplex TCR-T therapy for a wide range of solid tumor patients. Our initial solid tumor indications include non-small cell lung cancer, sarcoma, head & neck cancer, cervical cancer, and anal & genital cancer. For each patient with a solid tumor malignancy, we first analyze the patient's tumor to determine which targets are expressed at high levels and which HLA genes are still intact. We then access the ImmunoBank and select up to three TCRs that match their HLA type and address the most highly expressed targets in their tumor. We will use this set of TCRs to genetically reprogram their T cells to recognize these targets, and the resulting T cells will be infused back into the patient as a multiplex TCR-T therapy.

Enabled by the additional cargo capacity of our non-viral vector delivery system, we are also introducing enhancements to our product candidates to deepen tumor responses and prolong duration of response. By introducing the gene for CD8α/β along with the TCR gene, we are able to engineer both cytotoxic and helper T cells, which we believe has the potential to improve responses to treatment with TCR-T therapy in the clinic compared to engineering cytotoxic T cells alone. We are also adding DN-TGFβRII to T cells, which allows them to proliferate despite the presence of TGFβ in the hostile tumor microenvironment. This has the potential to enhance T cell persistence.

Strategic Partnerships and Collaborations. T cells play a fundamental role in many other therapeutic areas beyond cancer, such asautoimmune disorders and infectious diseases. We believe that our TargetScan technology is well suited to discover novel antigens for the development of therapeutics, diagnostics, and vaccines in these other therapeutic areas. We intend to opportunistically pursue collaborations with strategic partners for applications of our platform technologies outside our core focus of oncology.

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Our Strategy

Our mission is to create life-changing TCR-T therapy product candidates for patients by unleashing the untapped potential of the human immune system. Our goal is to use our proprietary platform technologies to identify novel tumor-specific antigens and clinically active TCRs to become a leader in the development of engineered T cell therapies for the treatment of heme malignancies and solid tumors. Our strategy includes the following key elements:

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Advance our lead product candidates, TSC-100 and TSC-101, through clinical development.Our two lead programs,TSC-100 and TSC-101, are designed to target HA-1 and HA-2, respectively, both of which are antigens with clinically demonstrated anti-tumor effects in patients who naturally develop T cells specific to these targets. We are currently enrolling patients in a multi-arm Phase 1 clinical study of TSC-100 and TSC-101 with 15 clinical sites activated and additional sites planned to be added in 2025. The study protocol allows us to conduct clinical trials of TSC-100 and TSC-101 in parallel, with patients enrolled in treatment arms based on their genotype. In addition, through our heme malignancies program, we have established a foundation of manufacturing, clinical and regulatory capabilities to support the development of our broad portfolio of TCR-T therapy product candidates.

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Advance our solid tumor program through clinical development.We are initially developing our solid tumor TCR-T therapy product candidates against five selected target antigens that are frequently expressed across multiple solid tumor types. Our first seven solid tumor TCR-T therapy product candidates address known and novel targets, including E7 of HPV16 for TSC-200-A0201, MAGE-C2 for TSC-201-B0702, MAGE-A4 for TSC-202-A0201, PRAME for TSC-203-A0201, and MAGE-A1 for TSC-204-A0201, TSC-204-C0702, and TSC-204-A0101. We believe that the treatment of solid tumors will require a combination of several therapeutic TCRs, which we refer to as 'multiplex therapy'. We plan to expand the ImmunoBank to broaden the reach of multiplex TCR-T therapy for the treatment of solid tumors.

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Leverage our proprietary platform technologies to expand the ImmunoBank of therapeutic TCRs to treat a wide range of tumor types. Our TargetScan technology enables us to identify novel antigens that are broadly expressed across multiple types of solid tumors. To ensure that the antigens identified are clinically relevant, we use TCRs from tumor samples of patients with exceptional responses to immunotherapy. Our platform allows us to assess the specificity and cytotoxicity of these TCRs to develop a portfolio of TCR-T therapy product candidates with therapeutic potential. We continue to prioritize expanding the ImmunoBank with TCRs for additional targets as well as multiple common HLA types for each target, thus enabling us to address tumor heterogeneity and resistance that may arise from target loss or HLA loss.

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Maintain manufacturing capabilities.We believe that in-house manufacturing capabilities substantially facilitate the successful early development of cell therapies. For our TCR-T therapy product candidates, we have developed a non-viral gene delivery system, which we refer to as T-Integrate, based on transposons that are designed to enable cost-effective and consistent cell manufacturing with short development times. We have built an internal, fully operational GMP manufacturing facility that we believe provides sufficient capacity to support our clinical programs in both heme malignancies and solid tumors. Additionally, we have engaged a global CDMO with commercial capabilities to further increase manufacturing capacity for both the heme and solid tumor programs and prepare for potential commercial manufacturing. The CDMO is on track to support clinical manufacturing of the heme program in the second half of 2025. The additional cargo capacity of our non-viral vector delivery system allows us to add T cell enhancements to our product candidates. By introducing the gene for CD8α/β along with the TCR gene, we are able to engineer both cytotoxic and helper T cells, which we believe has the potential to improve responses to TCR-T therapy in the clinic compared to engineering cytotoxic T cells alone. We are also adding DN-TGFβRII to T cells, which enables them to proliferate despite the presence of TGFβ in the hostile tumor microenvironment. This has the potential to enhance T cell persistence. Having treated over 30 patients with six different TCR-T candidates across both heme and solid tumor malignancies, we consider our approach to be validated.

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Develop next generation T cell engineering capabilities. Our long-term vision is to develop off-the-shelf products, either through allogeneic T-cell engineering or in vivo engineering, and provide customized multiplex TCR-T therapy to patients with a wide range of malignancies. Although our initial solid tumor programs are autologous, we are developing T cell engineering technologies and in-house manufacturing capabilities to transition our therapeutic TCRs to alternative modalities.

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Opportunistically pursue strategic partnerships and collaborations to maximize the full potential of our platform. Our platform representsa powerful tool to identify targets and TCRs in therapeutic areas outside of oncology, such as autoimmune disorders and infectious diseases. We intend to seek strategic partners with proven clinical development and commercialization capabilities for certain targets and/or assets that do not overlap with our internal programs or our core focus. To date, we have a research collaboration and license agreement with Amgen to identify the antigens recognized by T cells in patients with Crohn’s disease. Under the terms of the agreement, TScan received a $30.0 million upfront payment and is eligible to earn success-based milestone payments of over $500 million, based upon the achievement of certain development and commercial milestones as well as tiered single-digit royalty payments on net sales of products developed

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from the collaboration. Amgen will evaluate a variety of modalities to create therapeutics based on targets discovered by TScan and will retain all global development and commercial rights to such therapeutics. We have also expanded our target discovery capabilities to include both CD8+ and CD4+ T-cells by engineering our platform to include class II antigen presentation. This capability allows for us to expand discovery efforts into T cell-mediated autoimmune disorders that have a strong Major Histocompatibility Complexes, or MHC, class II linkage. We intend to leverage this new capability to identify the pathogenic autoantigens driving T-cell mediated autoimmune disorders.

Background on T Cell Therapies

The human immune system constantly provides a natural and highly effective defense against cancer, which only forms when tumor cells find a way to evade the immune system. The treatment of cancer was revolutionized over a decade ago with the advent of immunotherapy – therapeutic approaches designed to re-enable or re-direct immune cells to recognize and fight cancer. Over the past 10 years, a suite of immuno-oncology drugs has been approved and adopted as part of routine clinical practice. Successes in immuno-oncology came initially from the approval of immune checkpoint inhibitors and more recently from the development of cellular therapies, such as CAR-T and TIL therapies. These therapies all harness the power of cytotoxic T cells in fighting both heme malignancies and solid tumors. Although these therapies have demonstrated compelling efficacy, they are only effective in a subset of patients. To address a broader patient population, we believe additional T cell-based approaches are needed that more closely mimic the way the immune system recognizes and fights cancer in patients who are responding to immunotherapy.

Overview of T Cell Biology

T cells are an essential component of the adaptive immune system and provide protection against cancer, infection, and autoimmune disorders. T cells are classically divided into two primary types of activating cells: helper T cells and cytotoxic T cells. Helper T cells, which express the CD4 co-receptor, function by providing signals to other immune cells for activation and recruitment. Cytotoxic T cells, which express the CD8 co-receptor, function by killing any cells in the human body that are expressing unnatural proteins, including proteins that are not expressed in normal tissue, proteins that arise from mutated genes, or proteins derived from pathogens. By definition, tumor cells are abnormal and make a wide variety of unnatural proteins. T cells are activated and exert their helper or cytotoxic function when their TCRs recognize antigens displayed on the surface of malignant or infected cells.

Virtually every cell in the body has a mechanism for displaying on its surface a sampling of every protein that is being made by the cell. This includes all normal proteins as well as aberrant proteins if the cell is cancerous or proteins from pathogens if the cell has been infected. Cellular proteins are broken down into short fragments, or peptides, by the proteasome, and these peptides are loaded into MHCs to be displayed on the outside of the cell. These peptide/MHC complexes are recognized by TCRs on cytotoxic CD8+ T cells, as shown in the graphic below. Because the TCR recognizes both the peptide and the MHC, a TCR only functions correctly when both the peptide and the correct MHC are present.

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TCRs on Cytotoxic CD8+ T Cells Recognize the

Peptide/MHC Complexes of Tumor Cells

MHC proteins, which present different peptides to the human immune system, are highly variable among people. An individual’s MHC proteins are determined by their HLA type. Although there are many different HLA types, some are quite common. For example, 42% of individuals in the U.S. are positive for the HLA-A*02:01 allele, or variant. TCRs are often referred to as “HLA-restricted” because they are only able to interact with specific HLA types. For this reason, TCR-Ts harness the specificity of the TCR-peptide-MHC interaction to selectively target tumor cells.

Current Approaches to T Cell Therapy

Multiple approaches are being explored to develop effective T cell-based therapies for the treatment of cancer. One approach is to isolate naturally occurring T cells from a patient’s tumor, referred to as TILs, expand and activate those cells ex vivo, and then return them to the patient via intravenous infusion. Although the targets of these T cells are not known, it is presumed that T cells isolated from a tumor are enriched in T cells directed against cancer cells. This approach, however, depends on the anti-cancer T cells present in the patient. If the patient’s TILs do not have appropriate anti-cancer specificities or if their anti-cancer TILs cannot be adequately expanded ex vivo, the therapy is unlikely to be effective.

A different approach that has proven effective in certain heme malignancies is to identify targets that are highly expressed on the surface of tumor cells, such as CD19. Antibody fragments that recognize these targets are used to create an artificial construct that links the antibody to key signaling elements required for T cell activation. The resulting CAR is incorporated genetically into a patient’s T cells, thereby redirecting those cells to recognize and fight the patient’s cancer. Although CAR-T therapies have been highly effective in certain tumor types, leading to multiple approved products, the benefit of these therapies and the addressable cancer indications have been limited by several factors. First, it is likely that there is a relatively limited set of truly tumor-specific cell surface antigens. In general, most antigens expressed on the surface of tumor cells are also expressed on normal cells, resulting in therapies that, even if effective, have a narrow therapeutic window and are vulnerable to potentially life-threatening toxicities. Second, CAR-T cells rely on antibody fragments that recognize cell-surface proteins, precluding intracellular proteins as potential targets. Third, CAR-T therapies generally do not efficiently penetrate solid tumors, which to date has limited their applicability to heme malignancies.

In contrast to CAR-T therapies, naturally occurring TCRs offer two important benefits compared to antibody-containing artificial receptors. First, TCRs are the natural receptors used by the T cell to recognize foreign antigens. As such, they are optimized to stimulate the T cell appropriately when they engage their targets on a tumor cell. An appropriately stimulated T cell will not only kill the tumor

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cell, but also produce cytokines that stimulate other immune cells and make copies of itself, or proliferate, to further augment the immune response. Balancing all the cellular responses of a T cell is something that has been finely tuned over millions of years of evolution and is best mediated by naturally occurring TCRs, rather than by artificial constructs. Second, TCRs can recognize a much broader set of antigens, including peptides derived from both cell surface and intracellular proteins, whereas CARs are restricted to recognizing only cell surface proteins. MHC-I peptides are predominantly derived from intracellular proteins rather than extracellular proteins, which dramatically increases the universe of potential cancer-specific antigens that can be recognized by TCRs compared to CARs. We believe TCR-T therapy combines the benefits of TIL and CAR-T therapies while uniquely addressing their key limitations, as shown below.

Building on the Remarkable Success of Immunotherapy

The development of TCR-T therapy product candidates requires three key prerequisites: (i) an effective anti-cancer TCR; (ii) knowledge of the precise peptide antigen that is recognized by the TCR; and (iii) confirmation that the TCR does not recognize problematic off-targets. Each of these prerequisites is technically challenging. Historically, targets of anti-cancer T cell clones were identified through a manual and labor-intensive process, and the identification of each target was often a multi-year project. As a result, only a few dozen targets have been identified to date and most clinical development efforts are focused on a short list of the most promising targets.

Two key shortcomings in the TCR field remain: low response rates and limited duration of response. These are in part related to solid tumors being heterogenous, and to poor persistence of engineered T cells in patients. We believe we can overcome these known issues by adding enhancements to our product candidates, such as the addition of CD8α/β to improve persistence compared to CD8α alone. We are also co-introducing DN-TGFβRII, which is designed to overcome immunosuppression from TGFβ in the tumor microenvironment.

Our Approach

Our approach is based on the central premise that we can learn from patients who are winning their fight against cancer in order to treat those who are not. Using our proprietary platform technologies, we are analyzing the T cells of cancer patients with exceptional responses to immunotherapy to discover clinically relevant targets and TCRs. We have built and are expanding the ImmunoBank with the goal of delivering customized multiplex TCR-T therapy to a wide range of patients with cancers.

Our discovery process enables us to build and expand the ImmunoBank with what we believe represents the most active TCRs isolated from a large group of diverse patients who are responding to immunotherapy. We are developing TCR-T therapy product candidates that use these clinically relevant TCRs to reprogram the T cells of patients who do not spontaneously generate effective anti-cancer T cells and thus do not respond to immunotherapy. Such patients will first have their tumors undergo HLA typing and testing for the presence of tumor-specific targets. Next, to manufacture engineered T cells, white blood cells will be obtained from either the patient or a healthy donor using a procedure called leukapheresis. We will then transport these white blood cells to our in-house manufacturing facility, where we isolate the T cells and genetically engineer them using TCR sequences from the ImmunoBank. We believe the continued expansion and diversification of the ImmunoBank will enable us to deliver customized multiplexed TCR-T therapies to more

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patients, where each patient’s T cells are engineered with multiple TCRs that are matched to their specific tumor and HLA type. For example, if a patient’s tumor expresses high levels of a particular cancer target, their T cells will be reprogrammed with a TCR that recognizes that particular cancer target. The FDA's clearance of our T-Plex IND application for the simultaneous administration of different TCRs, as well as secondary IND applications for the first seven TCRs in our solid tumor program, allows us to rapidly and efficiently expand the ImmunoBank and enables us to work toward our goal of bringing customized, multiplex therapies to patients.

Once the T cells are engineered with a combination of the most relevant TCRs, they will be transported back to the treatment facility and reintroduced into the patient by intravenous infusion. Following the infusion, the engineered T cells, which are designed to recognize multiple targets expressed by the patient’s tumor, will proliferate in vivo and mount an anti-cancer immune response.

Key Features of Our Approach

We believe there are three key advantages to our approach:

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Our TCR-T therapy product candidates are based on highly active TCRs that are clinically relevant. Many other approaches to T cell therapy rely onspecifically expanding T cells that are already present in the patient. Our platform analyzes anti-cancer T cells from a wide variety of patients who are responding to immunotherapy in order to find the most active and clinically relevant TCRs against each target. We believe that we can develop TCR-T therapy product candidates for a wide range of patients, including those who do not have T cells that efficiently recognize their cancers.

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Our TCR-T therapy product candidates are designed to be used in combination with each other. We have built and are expanding the ImmunoBank of TCRs to allow formultiplex TCR-T therapy, which has the potential to address the heterogeneous nature of solid tumors and address resistance developing due to loss of a single target. We believe this approach may allow us to overcome the limitations and challenges of TCR-T development to date. We continue to prioritize expanding the ImmunoBank with TCRs for additional targets as well as multiple common HLA types for each target, thus enabling us to address tumor heterogeneity and resistance that may arise from target loss or HLA loss. As the ImmunoBank is populated with more TCRs, we expect that patient eligibility will expand, as will our target market opportunities.

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Our approach is expandable. TheImmunoBank has the flexibility to be used with new and optimized methods of T cell engineering that we maydevelop over time. We have built the ImmunoBank to be compatible with both autologous and allogeneic engineering technologies in order to potentially transition to generating off-the-shelf, allogeneic T cells that have been pre-engineered with our TCRs for direct administration to patients.

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Our Heme Malignancies Program

We are developing our heme malignancies program to treat patients with AML, MDS, or ALL who are undergoing allogeneic HCT. In the first phase of our clinical development strategy, we are initially focusing on well-recognized cancer targets that have been discovered in patients with exceptional responses to HCT-associated immunotherapy, including HA-1 and HA-2. Our program is based on the well-established observation that patients who are mismatched with their donors for minor histocompatibility antigens, or miHAs, such as HA-1 or HA-2, and naturally mount a T cell response against those antigens, show significantly lower relapse rates following HCT. By developing TSC-100 and TSC-101, TScan aims to recreate this natural graft versus leukemia response to prevent relapse in patients undergoing HCT.

We plan to further expand this program with the addition of TCRs targeting additional antigens across different HLA types. For example, TSC-102-A0301, a TCR-T therapy product candidate targeting an HLA-A*03:01-restricted epitope on CD45, is currently in IND-enabling activities.

Minor histocompatibility antigens like HA-1 and HA-2, and lineage-specific antigens like CD45, are distinct from other cancer-associated antigens such as WT1 previously targeted by TCR-Ts in heme malignancies. As shown below, cancer-associated antigens like WT1 have low and heterogenous expression and were previously selected so that normal blood cells in the patient would be spared. WT1-targeted TCR-Ts proved to have relatively poor efficacy in patients with ALL and AML, potentially due to the rapid emergence of resistant tumor cells that lacked WT1 expression and thus escaped killing by engineered T cells. HA-1, HA-2, and CD45, in contrast, have high and homogenous expression, making it less likely for tumors cells to escape due to low antigen expression. Although HA-1, HA-2, and CD45 are also expressed in normal blood cells, treating patients who are positive for these antigens, but have undergone hematopoietic cell transplantation from donors who are negative, ensures that the engineered T cells selectively eliminate all the patient’s blood cells – malignant, pre-malignant, or normal – while sparing donor-derived normal blood cells. This strategy therefore enables high levels of anti-cancer efficacy with what we believe to be less risk of life-threatening toxicities to normal cells.

We are conducting a Phase 1 clinical trial of our lead TCR-T therapy product candidates, TSC-100 and TSC-101, in parallel, with patients enrolled in treatment arms based on their genotype, as shown below. Patients who are positive for the target antigen, HA-1 or HA-2, as well as the HLA-A*02:01 allele, which is the HLA type required to display HA-1 and HA-2 on the cell surface for recognition by a T cell, are eligible for enrollment, provided they are paired with donors who are negative for either the target antigen or the HLA-A*02:01 allele.

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ALLOHATM, a Multi-arm Phase 1 Trial for TSC-100 and TSC-101 in Subjects with AML, ALL, and MDS

Background on Heme Malignancies

HCT has become the standard of care for many heme malignancies. When a patient with leukemia undergoes HCT, they start by receiving a conditioning regimen of high dose chemotherapy with or without radiation. This regimen is intended to kill both the patient’s leukemia cells as well as their native blood cells and blood cell precursors, including hematopoietic stem cells in their bone marrow. The patient then receives hematopoietic stem cells from an HLA-matched donor. The stem cells engraft in their bone marrow and start to repopulate their body with new blood cells, which are now genetically identical to the donor. HCT has demonstrated the rare opportunity in cancer treatment to generate long-term remissions or cures. For example, patients with AML who receive HCT have a five-year post-transplant survival rate of up to 50%.

Approximately 7,350 allogeneic HCT procedures are performed yearly in the U.S. in patients with AML, MDS, or ALL. As a curative therapy for many heme malignancies, use of HCT has been steadily increasing over the last two decades, with increased use driven largely by increasing donor qualification, an increase in disease prevalence due to aging populations, and improved conditioning regimens permitting broader use in older and frailer patient segments. In addition, newer, more effective leukemia therapies continue to drive an increasing use of HCT in patients who previously failed to achieve proper remission prior to transplant. While the approval of CAR-T therapies has significantly impacted the treatment of B cell malignancies over the last decade, HCT in non-B cell malignancies is anticipated to remain the standard of care for patients. An example of the limitations associated with CAR-T therapy is the difficulty differentiating tumor from normal cells as seen with CD19-targeted CAR-T therapies. CD19 is a target highly expressed on the surface of tumor cells, as well as normal B cells, which are also eliminated by CD19 targeted CAR-T cells. While loss of B cells does not generally lead to serious complications, toxicity on other normal myeloid blood cell types such as neutrophils would cause a life-threatening complication called febrile neutropenia in which bacterial infections occur due to the loss of neutrophils. This is one reason why CAR-T therapies cannot be used in non-B cell heme malignancies such as myeloid leukemias and HCT remains the standard of care for those patients.

However, despite the increasing use of HCT and the resulting clinical benefits or cures, approximately 40% of the patients who receive HCT relapse within two years, at which point there are limited treatment options, and the prognosis is very poor. Clinical observations have shown that if the T cells of the donor recognize certain miHAs in the patient’s leukemia cells, such as proteins that have single amino acid differences between the patient and the donor, the T cells of the donor drive a specific graft vs. leukemia, or GvL, effect, whereby the engrafted donor T cells detect remaining leukemia as foreign and eliminate the remaining disease. As a result,

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the patient often experiences a long-term remission from their cancer, or even a complete cure. If the miHAs are also expressed in non-hematopoietic tissues, the patient may develop graft vs. host disease, or GvHD, but if the miHAs are only expressed in blood cells, a specific GvL effect is observed without an increase in GvHD. Our heme malignancies program is focused on targeting miHAs that are exclusively expressed in hematopoietic cells in order to induce the GvL effect while potentially mitigating the risk of GvHD.

TSC-100

TSC-100 is an allogeneic, donor derived TCR-T therapy product candidate directed at eliminating all native blood cells, including residual cancer cells, in HA-1-positive and HLA-A*02:01-positive patients with heme malignancies who undergo HCT using a donor who is either HA-1-negative or HLA-A*02:01-negative. We selected this product candidate based on its superior affinity, cytotoxic activity, and specificity compared to the other potential candidates. TSC-100 is designed to elicit an anti-tumor response in patients by targeting HA-1, which is present on malignant and normal blood cells of HA-1-positive patients but not on any of the new, donor-derived blood cells they receive from a donor who is either HA-1-negative or HLA-A*02:01-negative. We believe that donor T cells specifically engineered to express this TCR will generate an anti-tumor effect in patients, leading to a reduction in relapse rates and an increase in long-term survival.

HA-1 was one of the first miHAs to be discovered in a patient undergoing HCT. HA-1 is a peptide antigen derived from the protein ARHGAP45, which is an intracellular protein expressed at high levels in all blood cells but not in any other tissue. ARHGAP45 comes in two forms. In HA-1-positive individuals, the peptide has the sequence VLHDDLLEA and, if the individual has the HLA type A*02:01, the antigen is efficiently displayed on the surface of blood cells. In HA-1-negative individuals, the peptide has the sequence VLRDDLLEA, and the HA-1 antigen is not displayed. Approximately 60% of people have the VLHDDLLEA sequence and approximately 42% of people in the U.S. have the HLA type A*02:01, which means that approximately 25% of individuals in the U.S. are HA-1-positive with the specific HLA type required for antigen expression. Studies of patients receiving HCT have shown that in cases where the T cells of an HA-1-negative donor naturally develop a response to HA-1 in an HA-1-positive patient, the T cells mediate a specific GvL effect, and the patient often experiences a long-term remission. TSC-100 is based on this clinical observation and is designed to specifically cause this GvL effect in patients receiving HCT.

We are developing TSC-100 as a treatment for patients with cancer who are HA-1-positive and have been deemed eligible for HCT. For each patient, a healthy donor who is HA-1-negative or HLA-A*02:01-negative will be identified. Hematopoietic stem cells isolated from that donor will be used as the source of transplant material. In parallel, T cells isolated from the same donor will be genetically engineered to recognize HA-1. Once engraftment of donor stem cells is established in the patient, TSC-100 will be infused into the patient with the goal of eliciting a highly specific anti-tumor effect. The engineered donor T cells are designed to recognize and eliminate all of the patient’s native blood cells, including residual leukemia cells, which are HA-1-positive, thereby preventing relapse and potentially promoting complete cures. Because the patient’s new healthy blood cells are derived from the donor and are therefore either HA-1-negative or HLA-A*02:01-negative, we believe that TSC-100 should have minimal toxic side effects.

Because people inherit two copies of every chromosome, one from their mother and one from their father, everyone has two copies of the ARHGAP45 gene. HA-1-positive patients can therefore be either homozygous for HA-1 (+/+), with both genes encoding the HA-1-positive peptide (VLHDDLLEA), or heterozygous for HA-1 (+/-), with one gene encoding the HA-1-positive peptide and the other encoding the HA-1-negative peptide (VLRDDLLEA). To ensure that TSC-100 can effectively eliminate healthy blood cells and leukemia cells that are either homozygous HA-1-positive (+/+) or heterozygous HA-1-positive (+/-), we assessed the activity of TSC-100 against blood cells derived from a variety of healthy donors and patients with AML and ALL.

TSC-101

Like TSC-100, TSC-101 is an allogeneic, donor derived TCR-T therapy product candidate directed at eliminating residual cancer cells in HA-2-positive and HLA-A*02:01-positive patients with heme malignancies who undergo HCT using a donor who is either HA-2-negative or HLA-A*02:01-negative. HA-2, which is derived from the protein MYO1G, is another miHA that has been identified to be clinically relevant. In patients who naturally develop HA-2-specific T cells, a GvL effect has been observed and these patients experience long-term remissions. We are developing TSC-101 based on a highly active TCR we discovered that recognizes HA-2.

Unlike HA-1, the HA-2 antigen is highly prevalent, with approximately 95% of individuals in the U.S. being HA-2-positive. However, as with HA-1, a specific HLA type, HLA-A*02:01, which is present in approximately 42% of individuals in the U.S., is required to display the HA-2 antigen on the cell surface for recognition by a T cell. As a result, approximately 40% of HCT patients would be positive for both HA-2 and HLA-A*02:01 and therefore be eligible for treatment with TSC-101 using a donor who is negative for HLA-A*02:01, regardless of whether the donor is HA-2-positive or HA-2-negative. Such donors are straightforward to identify and should be available to most patients who undergo half-matched, or haploidentical, transplantation using family members as donors, as

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patients typically have between two and three potential haploidentical donors. A summary of the treatment paradigm for TSC-101 is shown below.

Patient Journey for TSC-101

TSC-102-A0301

Like TSC-100 and TSC-101, TSC-102-A0301 is an allogeneic, donor derived TCR-T therapy product candidate directed at eliminating residual cancer cells in patients with heme malignancies who are HLA-A*03:01-positive undergoing HCT using a donor who is HLA-A*03:01-negative. CD45, which is derived from the protein PTPRC, is an antigen that has been identified to be clinically relevant. For example, radiolabeled CD45 is in clinical trials for relapsed AML, and a CAR-T product candidate targeting CD45 with epitope-edited HSCs is in pre-clinical development. We are developing TSC-102-A0301 based on a highly active TCR we discovered that recognizes a CD45 antigen presented on HLA-A*03:01. TSC-102-A0301 is currently in IND-enabling activities.

The CD45 antigen is expressed on all nucleated cells of hematopoietic origin. As with TSC-100 and TSC-101, a specific HLA type, HLA-A*03:01, which is present in approximately 22% individuals in the U.S. is required to display the CD45 antigen on the cell surface for recognition by TSC-102-A0301. HLA-A*03:01 negative donors are straightforward to identify and should be available to most patients who undergo HLA half-matched, or haploidentical, transplantation using family members as donors. HLA-A*03:01 negative donors can also be mismatched unrelated donors readily identified through donor registries such as the National Marrow Donor Program. Having such donor options thus enables virtually all HLA-A*03:01 positive patients to potentially qualify for treatment with TSC-102-A0301.

Clinical Development Plan for Our Heme Malignancies Program

Background on Types of HCT

Patients with acute leukemias who undergo allogeneic HCT have heterogeneous outcomes that are primarily related to two main variables: (i) the intensity or doses of the conditioning regimen they receive prior to the stem cell infusion and (ii) the type of donor who provides the stem cells.

High-intensity conditioning regimens are called myeloablative conditioning and are associated with higher mortality rates. They are therefore reserved for young and relatively fit patients. Lower-intensity regimens are called reduced-intensity conditioning, or RIC, and are better tolerated, but are associated with higher relapse rates. Our heme malignancies TCR-T therapy product candidates are designed to substantially reduce relapse rates, and we are enrolling patients into our ongoing Phase 1 clinical trial who are eligible for RIC-based HCT with the goal of improving clinical outcomes for these patients.

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There are different types of donors who are eligible for allogeneic HCT procedures. Donors who are siblings of the patient and are perfectly matched for eight out of eight HLA alleles are considered the highest priority donor type for patients undergoing allogeneic HCT, but these types of donors are available for less than a third of patients. For most patients, the choice is between an unrelated donor who is perfectly matched for eight out of eight HLA alleles, referred to as a matched unrelated donor, or MUD, or a family member such as a sibling or child who has a half-match with the patient, referred to as a haploidentical donor, or haplo. Historically, haplo donor transplantation was associated with much higher GvHD than MUD transplants, but a recent treatment regimen that uses chemotherapy given three days after stem cell infusion called post-transplantation cyclophosphamide, or PTCy, specifically kills immune cells that cause GvHD. As a result, haplo transplants with PTCy have recently achieved equivalent outcomes as MUD transplants and are rapidly increasing in usage in the U.S. and worldwide.

The use of haplo greatly expands the donor pool for patients undergoing HCT and provides patients with the optionality to choose donors who are mismatched on specific HLA types, such as A*02:01, as opposed to being mismatched on certain minor antigens, such as HA-1 or HA-2. We are developing our product candidates with a specific focus on patients undergoing haplo donor transplantation with donors who are negative for either the miHA or the specific HLA type. We believe the engineered donor T cells will recognize any residual leukemia cells, which are target-positive, in the patient and prevent relapse with the potential to promote complete cures. Because the patient’s new healthy blood cells are derived from the donor and are therefore either target-negative or not able to express the target, we expect that these product candidates should have minimal toxic side effects.

Phase 1 Clinical Trial

The clinical studies for TSC-100 and TSC-101 are well underway, within a multi-arm, controlled, Phase 1, "umbrella" design clinical trial to investigate the safety and efficacy of TSC-100 and TSC-101 in patients with AML, MDS, and ALL that are undergoing HCT following RIC. We are currently treating patients at the third and final dose level.

Our Phase 1 clinical trial is designed to include measurements of early surrogate markers of efficacy, such as donor chimerism, or the percentage of blood cells that are donor-derived, and whether patients continue to have detectable residual leukemia, referred to as minimal residual disease, or MRD, in their post-transplant bone marrow biopsy, both of which are predictors of relapse. As shown in the graphic below, we are also including a control arm, comprising patients who do not meet the HLA or miHA genetic criteria and are treated with standard RIC haplo transplantation alone. Comparisons of both safety and efficacy outcomes with this control arm will potentially enable all patients treated with TSC-100 or TSC-101 to be included as part of the efficacy analysis for the initial Phase 1 trial prior to transitioning the program into a registrational trial towards a potential future biologics license application, or BLA, filing.

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Multi-Arm Phase 1 Clinical Trial Design

Clinical data

In December 2024 we reported updated results from the ongoing Phase 1 ALLOHATM trial, which we presented at the 66th American Society of Hematology (ASH) Annual Meeting and Exposition. At that time, 38 patients had been enrolled in the trial and undergone HCT, with 26 in the treatment arm and 12 in the control arm. The key endpoints in the trial are safety and efficacy, with exploratory endpoints of donor chimerism and MRD.

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As shown below, event-free survival favored the treatment arm (HR=0.30; P=0.04) and early trends suggested a lower probability of relapse (HR=0.28; P=0.14).

As of the latest data cut (December 2, 2024, shown below), 2 of 26 (8%) of treatment-arm patients relapsed compared to 4 of 12 (33%) control-arm patients. One treatment-arm relapse and subsequent mortality occurred in a very high-risk patient who was taken to transplant without first achieving complete remission, and the other was an extramedullary relapse in the patient's central nervous system with no evidence of systemic relapse. Median time to relapse was not evaluable in the treatment-arm versus 160 days in the control arm. Eight of 38 (21%) patients in the study had TP53 mutations, with 6 cases in the treatment-arm and 2 cases in the control arm. Of the 4 patients in the treatment arm with these mutations who received TCR-T cell infusions, none has relapsed, and one patient has now been relapse-free for 22 months. Of the two patients in the control arm with mutated TP53, both relapsed within 6 months of transplant and died shortly thereafter.

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TSC-100 and TSC-101 infusions were generally well-tolerated at all three dose levels with no dose-limiting toxicities. Observed adverse events were similar across the treatment and control arms and were generally consistent with post-HCT adverse events. TSC-100 and TSC-101 TCR-T cells were detected at all time points in all treated patients, including those who have been on study for over a year, with clear evidence of a dose-persistence relationship (shown below).

Anticipated timeline

We have now successfully manufactured our product candidates and dosed patients in both treatment arms of the Phase 1 clinical trial. Patients have been enrolled up to the third 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. We have opened expansion cohorts at dose level 3 to further characterize safety and evaluate translational and efficacy endpoints. We plan to continue development of TSC-101 only, as TSC-101 enables treatment of ~98% of patients with the HLA type A*02:01. We expect to initiate a registrational trial for TSC-101, pending further feedback from regulatory authorities, in the second half of 2025. We plan to present additional data from the Phase 1 trial by the end of the year, including two-year relapse data on the initial patients. We also plan to file an IND application for TSC-102-A0301, a TCR-T therapy product candidate targeting an HLA-A*03:01-restricted epitope on CD45, in the second half of 2025.

Future market expansion opportunities

If TSC-100 and TSC-101 demonstrate the ability to significantly reduce relapse rates after HCT, there could potentially be new opportunities to expand the curative potential of HCT combined with TSC products to greater numbers of patients. Currently, only about 7,350 patients with AML, MDS, or ALL undergo HCT per year in the U.S. out of approximately 35,000 patients diagnosed each year. There are two reasons for this relatively modest rate of transplant use. First, only patients who achieve a clinical complete remission (CR) are referred for HCT since the relapse rates of patients not in CR are considered too high to effectively use HCT. If HCT, combined with either TSC-100 or TSC-101, markedly reduces relapse rates, patients who do not achieve CR could possibly undergo HCT and benefit from its curative potential. This market expansion would require a separate clinical trial. Second, while RIC has enabled many more elderly and frail patients to undergo transplantation, the chemotherapy and radiation doses used for conditioning are still high and considered too toxic for most patients over the age of 65 or those with underlying comorbidities. This is because the conditioning regimen of HCT is considered the primary modality for eliminating residual leukemia cells and reducing doses further would result in greater relapse rates. If the relapse rates could be reduced by treatment with either TSC-100 or TSC-101 post HCT, however, a clinical trial could test the use of minimal intensity conditioning prior to HCT. If successful, this would further expand the curative potential of HCT combined with TSC-100 or TSC-101 therapy to older, frailer patients. We could also expand the addressable market through the addition of TCRs for other HLA types, of which TSC-102-A0301 is an example of this approach.

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A final market expansion opportunity could occur from the use of either TSC-100 or TSC-101 as a chemotherapy and radiation-free conditioning regimen for non-malignant diseases such as sickle cell anemia which are currently treated with HCT. Since chemotherapy and radiation are associated with the risk of long-term toxicities such as cancer, heart damage, lung damage and infertility, cellular therapies such as TSC-100 or TSC-101 could reduce those risks and increase the numbers of patients willing to undergo HCT for non-malignant diseases.

Solid Tumor Program

We are developing a portfolio of autologous TCR-T therapy product candidates designed to be used in combination with each other to treat and eliminate solid tumors. Our solid tumor product candidates are designed to elicit an anti-tumor response in patients by targeting cancer-specific antigens in their tumor cells. Our TCR-T therapy product candidates include: (i) well-recognized cancer targets that have demonstrated anti-tumor activity in clinical trials as well as novel targets that were identified by TargetScan from the T cells of patients responding to immunotherapy and (ii) naturally occurring TCRs specific to a patient’s HLA type that recognize these cancer-specific targets. Such targets are not only commonly shared among patients with the same cancer type, but also frequently expressed in multiple solid tumor types, enabling clinical development across multiple indications. Our seven solid tumor TCR-T therapy product candidates address known and novel targets, including HPV16 for TSC-200-A0201, MAGE-C2 for TSC-201-B0702, MAGE-A4 for TSC-202-A0201, PRAME for TSC-203-A0201, and MAGE-A1 for TSC-204-A0201, TSC-204-C0702, and TSC-204-A0101. To date, we have received FDA clearance for eight INDs for the treatment of solid tumors. These include a primary IND for the entire solid tumor program, which we refer to as T-Plex, which supports the simultaneous use of multiple TCRs to create customized multiplex TCR-T therapy product candidates based on target and HLA expression. The FDA has also cleared INDs for TSC-203-A0201 (PRAME, HLA-A*02:01); TSC-200-A0201 (HPV16, HLA-A*02:01); TSC-201-B0702 (MAGE-C2, HLA-B*07:02); TSC-202-A0201 (MAGE-A4, HLA-A*02:01); TSC-204-A0201 (MAGE-A1, HLA-A*02:01); TSC-204-C0702 (MAGE-A1, HLA-C*07:02); and TSC-204-A0101 (MAGE-A1, HLA-A*01:01). We plan to further expand the ImmunoBank by filing INDs for additional TCRs.

We have built the ImmunoBank, a repository of highly active TCRs, to enable multiplex TCR-T therapy. We are expanding the ImmunoBank with additional TCRs that recognize diverse targets and are associated with multiple HLA types to provide a broad array of therapeutic options for patients with various types of solid tumors. For patients with a solid tumor malignancy, we analyze their tumor to determine which targets are expressed at high levels in their cancer. We then access the ImmunoBank and select up to three TCRs that match their HLA type and address the most highly expressed targets in their tumor. We use this set of TCRs to genetically reprogram their T cells to recognize these targets and the resulting engineered T cells are infused back into the patient simultaneously as a multiplex TCR-T therapy.

We Are Building the ImmunoBank of TCRs to Enable Multiplex TCR-T Therapy

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TCR-T Therapy Product Candidates for the Treatment of Solid Tumors

Immunotherapy has reshaped the treatment of solid tumors by demonstrating that tumor shrinkage, eradication, and long-term durable responses can be obtained by stimulating the patient’s own immune system to attack their cancer cells. Immune checkpoint inhibitors, such as nivolumab or pembrolizumab, work by unleashing anti-cancer T cells that are already present in a patient’s tumor, enabling those T cells to recognize and eliminate their cancer. For patients who respond to checkpoint inhibitors, these agents have been shown to be very effective. However, only a subset of patients responds to checkpoint inhibitors, highlighting the need for T cell-based therapies that can treat those patients who do not respond. Despite their efficacy in only a subset of patients, checkpoint inhibitors have annual sales of about $25 billion in the U.S.

One reason why patients do not respond to current immunotherapy treatments is that they lack T cells with highly active TCRs that recognize cancer-specific antigens in their tumors. By reprogramming the patient’s own T cells to recognize these targets, we believe that we can expand the dramatic responses observed with checkpoint inhibitor therapy to the patients for whom these therapies are ineffective.

Our Solution

Our solid tumor program is designed to overcome key solid tumor resistance mechanisms of target loss and HLA loss. Solid tumors are notoriously heterogeneous, with a solid tumor often expressing more than one target antigen. We believe that by targeting multiple antigens expressed on in-tact HLAs, we will be able to drive deep and durable responses. We continue to prioritize expanding the ImmunoBank with TCRs across different targets and HLA types to potentially enable customized multiplex TCR-T therapy.

Our Solid Tumor Product Candidates

Our seven clinical-stage solid tumor TCR-T therapy product candidates address known and novel targets, including E7 of HPV16 for TSC-200-A0201, MAGE-C2 for TSC-201-B0702, MAGE-A4 for TSC-202-A0201, PRAME for TSC-203-A0201, and MAGE-A1 for TSC-204-A0201, TSC-204-C0702, and TSC-204-A0101. All of these targets are frequently expressed in the solid tumors of interest to us, including NSCLC, sarcoma, head and neck cancer, cervical cancer, and anal and genital cancer. In 2024, it is estimated that in the U.S., approximately 190,000 patients were diagnosed with NSCLC, 14,000 with sarcoma, 58,000 with head and neck cancer, 14,000 with cervical cancer, and 28,000 with anal and genital cancer. We have advanced a combination of known and novel targets into clinical development, which is allowing us to use the product candidates targeting known antigens as backbones for our initial clinical trials evaluating multiplex TCR-T therapy. For example, we plan to evaluate TSC-203-A0201, which targets PRAME, a well-known and clinically validated tumor-specific protein, in combination with TSC-201-B0702 targeting MAGE-C2.

TSC-200 (HPV16)

We are developing the TSC-200 series of product candidates as TCR-Ts targeting human papilloma virus, or HPV. Over 25% of head and neck cancers are caused by HPV infection, including up to 70% of oropharangeal cancers. HPV antigens are a particularly compelling set of targets as HPV proteins drive tumorigenesis in these cancers, which means that these proteins are (1) present in every tumor cell in an HPV-positive tumor and (2) essential to the survival of the tumor cell. In addition to head and neck cancers, HPV is found in more than 90% of cervical, anal and genital cancers. Phase 1 clinical data from the National Cancer Institute showed tumor regression with objective clinical responses in 50% of patients with metastatic HPV-positive cancers who were treated with a TCR-T therapy candidate targeting E7 of HPV16, which we believe provides clinical support for the inclusion of an HPV16-targeting TCR-T, TSC-200-A0201, in our multiplex TCR-T treatment strategy. We have advanced TSC-200-A0201 (HPV16, HLA-A*02:01) into Phase 1 development. We also intend to extend our discovery efforts to include additional HPV16-derived antigens presented on other HLA types as the program advances, such as TSC-200-C0702 (HPV16, HLA-C*07:02), currently in discovery.

TSC-201 (MAGE-C2)

We are developing the TSC-201 series of TCR-T therapy product candidates as TCR-Ts targeting melanoma-associated antigen C2, or MAGE-C2. We initially identified MAGE-C2 as the target of T cells from a melanoma patient responding to TIL therapy. MAGE-C2 is a cancer testis antigen, or CTA, that is exclusively expressed in testis and is not expressed in normal adult tissues. The testis is an immune-privileged tissue and, as a result, we believe that targeting MAGE-C2 should not pose a significant safety concern. In addition, MAGE-C2, which contributes to tumorigenesis by suppressing the cellular mechanisms responsible for controlling cell division, is selectively expressed across multiple different types of tumors, including approximately 25% of head and neck cancers, and approximately 50% of non-small cell lung cancers. Tumors expressing MAGE-C2 have been shown to be associated with metastasis and poor patient survival. We are currently advancing three MAGE-C2 TCRs: TSC-201-B0702 (MAGE-C2, HLA-B*07:02), currently in Phase 1 development; TSC-201-A0201 (MAGE-C2, HLA-A*02:01), currently in discovery; and TSC-201-A2402 (MAGE-C2, HLA-A*24:02), currently in discovery. We are also using ReceptorScan to identify additional TCRs for MAGE-C2 epitopes presented on other HLA alleles to further expand the ImmunoBank and increase the addressable patient population.

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TSC-202 (MAGE-A4)

We are developing the TSC-202 series of TCR-T therapy product candidates as TCR-Ts targeting melanoma-associated antigen 4, or MAGE-A4. MAGE-A4 is a clinically established CTA that contributes to tumorigenesis by interfering with cell cycle arrest. MAGE-A4 is expressed in 33% of cervical cancers enabling multiplexing with TSC-200, and MAGE-A4 is expressed in 50% of non-small cell lung cancers, 40% of head and neck cancers, and 20-70% of sarcomas depending on sub-type. We have advanced one MAGE-A4 TCR-T therapy product candidate, TSC-202-A0201, into Phase 1 development.

TSC-203 (PRAME)

We are developing the TSC-203 series of TCR-T therapy product candidates as TCR-Ts targeting Preferentially Expressed Antigen in Melanoma, or PRAME. Like MAGE-C2, PRAME contributes to tumorigenesis by suppressing cellular signals that control cell division, and higher expression levels of PRAME in tumors correlate with increased metastasis and poor patient outcomes. PRAME is a CTA that, like MAGE-C2 and MAGE-A4, is absent in adult tissues except in the ovaries and testis. Approximately 50% of NSCLCs, approximately 25% of cervical cancers, approximately 90% of head and neck cancers, and approximately 10-90% of sarcomas (depending on sub-type) express PRAME. Notably, sarcoma subtypes that highly express PRAME also highly express MAGE-A4, making this an attractive indication for multiplex therapy. We are currently advancing three PRAME TCR-T therapy product candidates: TSC-203-A0201 (PRAME, HLA-A*02:01), currently in Phase 1 development; TSC-203-B0702 (PRAME, HLA-B*07:02), currently in lead optimization; and TSC-203-A2402 (PRAME, HLA-A*24:02) currently in discovery.

TSC-204 (MAGE-A1)

We are developing the TSC-204 series of TCR-T therapy product candidates as TCR-Ts targeting melanoma-associated antigen 1, or MAGE-A1. MAGE-A1 is a cancer/testis gene frequently overexpressed in a wide variety of solid tumors, including approximately 45% of head and neck cancers, 50% of cervical cancers and 50% of NSCLC. Using our TargetScan platform, we initially identified MAGE-A1 as one of the targets of expanded T cells from a head and neck cancer patient responding to checkpoint inhibitor therapy. Multiple different TCRs from this patient recognize a novel HLA-C*07:02-restricted epitope of MAGE-A1, and one of these TCRs is the basis of TSC-204-C0702 (MAGE-A1, HLA-C*07:02), currently in Phase 1 development. In addition to this TCR-T therapy product candidate, we further expanded the TSC-204 series by using ReceptorScan to identify additional TCRs for MAGE-A1 epitopes presented on several other common HLA alleles to further expand the addressable patient population. We are currently advancing five MAGE-A1 TCR-T therapy product candidates: TSC-204-A0201 (MAGE-A1, HLA-A*02:01), currently in Phase 1 development; TSC-204-C0702 (MAGE-A1, HLA-C*07:02), currently in Phase 1 development; TSC-204-A0101 (MAGE-A1, HLA-A*01:01) currently in Phase 1 development; TSC-204-A0301 (MAGE-A1, HLA-A*03:01) currently in discovery; and TSC-204-B0702 (MAGE-A1, HLA-B*07:02) currently in discovery.

We are continuing to leverage our platform technologies to expand patient eligibility for multiplex TCR-T therapy. We plan to expand the ImmunoBank to address different HLA types to enable customized multiplex TCR-T therapy product candidates while also addressing the potential issue of HLA loss leading to resistance for a wide range of solid tumor patients.

Clinical Development Plan for Our Solid Tumor Program

For the initial first-in-human studies for our solid tumor TCR-T therapy product candidates, we are evaluating multiple TCRs in parallel to determine the safety and preliminary efficacy of multiplex TCR-T therapy. The FDA has cleared our IND application for T-Plex, which serves as the primary IND application for our solid tumor program, enabling customized simultaneous administration of TCR-T therapy product candidates to be administered to patients based on the targets and HLAs expressed in their tumors. Specific TCRs for each patient are chosen from the ImmunoBank consisting of high affinity, naturally occurring TCRs that recognize a variety of prevalent cancer-specific targets and are associated with common HLA types. Each unique TCR-T therapy product candidate has been or will be filed as a secondary IND application and will reference the primary T-Plex IND application.

In addition to the T-Plex IND application, the FDA has cleared secondary IND applications for seven TCR-T therapy product candidates: TSC-203-A0201 (PRAME, HLA-A*02:01); TSC-200-A0201 (HPV16, HLA-A*02:01); TSC-201-B0702 (MAGE-C2, HLA-B*07:02); TSC-202-A0201 (MAGE-A4, HLA-A*02:01); TSC-204-A0201 (MAGE-A1, HLA-A*02:01); TSC-204-C0702 (MAGE-A1, HLA-C*07:02); and TSC-204-A0101 (MAGE-A1, HLA-A*01:01). We have initiated a multicenter Phase 1 clinical trial to evaluate the safety, preliminary efficacy, and feasibility of repeat dosing of multiplex TCR-T therapy. We are enrolling patients with NSCLC, sarcoma, head and neck cancer, cervical cancer, and anal and genital cancer. We expect that many of the clinical trial sites enrolling patients in our heme malignancies program are planning to join our solid tumor Phase 1 study. We are currently enrolling and treating patients in this study.

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After establishing single agent safety for each of our initial solid tumor TCR-T therapy product candidates in a multi-arm Phase 1 clinical trial, we plan to test our solid tumor TCR-T therapy product candidates in combination with other TCR-T therapy product candidates in the ImmunoBank in patients who are positive for the respective targets of these therapies. We will explore up to three-TCR simultaneous administrations in patients who are positive for the respective targets. A summary of our planned Phase 1 clinical strategy is shown below.

Dose Escalation Scheme Provides a Rapid Path to Multiplex TCR-T Therapy in Phase 1

Anticipated timeline

As we advance our solid tumor program, we anticipate submitting IND filings for additional TCRs. We believe this trial will serve as the first step towards our long-term goal of expanding the ImmunoBank to provide customized multiplex TCR-T therapy product candidates for virtually any patient with a solid tumor malignancy. We have successfully manufactured product candidates and infused patients with singleplex therapy and expect to dose our first multiplex patient in the first half of 2025. We plan to report safety and response data for multiplex therapy in the second half of 2025.

ImmunoBank – Flexible Content for Diverse Platforms

Our current clinical development strategy is based on autologous T cell engineering. As the field of T cell engineering evolves, a wide variety of additional manufacturing platforms are being developed that may further improve TCR-T products. For example, companies such as Lyell Immunopharma, Inc. are developing methods to enhance autologous T cell engineering to provide improved duration of efficacy, while companies such as Allogene Therapeutics, Inc. are developing ways to engineer allogeneic T cells and companies such as Umoja Biopharma, Inc. are developing ways to engineer T cells in vivo. All of these engineering platforms require validated “content” – TCRs that recognize tumor-specific antigens on cancer cells without recognizing problematic off-targets. As we advance the ImmunoBank of TCRs through clinical development, we intend to continue to optimize our own manufacturing platform, in preparation for potential commercial manufacturing. Ultimately, we aspire to build the largest collection of validated TCR “content” that can be used with a variety of T cell engineering platforms.

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Expansion Opportunities Beyond Oncology

Our primary focus is on the development of T cell therapies to treat cancer. However, T cells play a fundamental role in many other disease areas, such as infectious disease and autoimmune disorders. We believe that our TargetScan technology is well suited to discover novel antigens for the development of therapeutics, diagnostics, and vaccines in these other areas. We intend to build additional corporate value by opportunistically pursuing collaborations with strategic partners for applications of our platform technologies outside our core focus.

Other Diseases

TargetScan can also be used for novel target discovery in additional infectious diseases and autoimmune disorders. For example, infections such as tuberculosis, influenza, and HIV have been shown to be T cell-mediated and are associated with high mortality rates. In addition, many autoimmune disorders such as rheumatoid arthritis, psoriasis, and scleroderma are largely T cell-mediated, but with poorly defined instigating self-antigens. Our TargetScan technology, which provides an unbiased, genome-wide method to discover the natural targets of disease-relevant T cells, is well positioned to identify these self-antigens. We believe the discovery of these targets could enable the development of novel, more targeted therapeutic approaches to treat these diseases.

Our Platform

Our proprietary platform is designed to: (i) discover anti-cancer TCRs from patients with exceptional responses to immunotherapy; (ii) determine novel targets of clinically relevant TCRs; (iii) discover novel TCRs that recognize clinically validated targets; (iv) identify off-target interactions of TCRs to eliminate candidates that could potentially pose a safety risk; and (v) manufacture TCR-T therapy product candidates efficiently and consistently without the use of viral vectors using our T-Integrate technology. The central elements of our platform that we believe differentiate us from other cell therapy companies are TargetScan, ReceptorScan, SafetyScan, the ImmunoBank, and T-Integrate.

TargetScan. At the core of our proprietary platform is TargetScan, which enables us to identify natural targets of TCRs using anunbiased, genome-wide, high-throughput screen. We have developed this technology to be extremely versatile and applicable across multiple therapeutic areas, including cancer, autoimmune disorders, and infectious diseases. It can be applied to virtually any TCR that plays a role in the cause or prevention of disease. Using TargetScan, we have identified approximately 200 novel antigens as targets of tumor infiltrating T cells from patients who are actively responding to immunotherapy. We believe this provides us with a competitive advantage, because not only are we among the first to identify these targets as tumor-specific antigens, but we have also already identified highly active TCRs that recognize these targets. Two of our pipeline programs emerged from TargetScan: TSC-201-B0702 (MAGE-C2, HLA-B*07:02) and TSC-204-C0702 (MAGE-A1, HLA-C*07:02), the latter of which was featured in the peer-reviewed journal Cell in 2022.

ReceptorScan. To further expand our ability to discover and develop therapeutic TCRs, we have developed our proprietary ReceptorScan technologyto enable us to identify and clone highly active TCRs that recognize known or clinically validated targets. We co-culture hundreds of millions of CD8+ T cells from either healthy donors or cancer patients with dendritic cells, also referred to as antigen-presenting cells, that display the target antigen of interest to the T cells. T cells that recognize the target of interest proliferate

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and are subsequently isolated based on their ability to recognize a fluorescently labeled version of the target. We then use single cell sequencing to identify the specific TCR sequences that recognize the target. Our novel technologies allow us to gene-synthesize hundreds of TCRs simultaneously and to rapidly sort through hundreds of target-specific TCRs in a single high-throughput screen to identify the most active clones. Using ReceptorScan, we have identified our two lead TCR-T therapy product candidates, TSC-100 targeting HA-1 and TSC-101 targeting HA-2, as well as several other pipeline programs, including TSC-203-A0201 (PRAME, HLA-A*02:01), TSC-200-A0201 (HPV16, HLA-A*02:01), TSC-204-A0201 (MAGE-A1, HLA-A*02:01), TSC-204-A0101 (MAGE-A1, HLA-A*01:01), and TSC-202-A0201 (MAGE-A4, HLA-A*02:01).

SafetyScan. SafetyScan is designed to identify potential off-target interactions of a given TCR and eliminate those TCR candidates that cross-react with proteins expressed at high levels in normal tissue. We believe this will allow us to reduce the risk and enhance the potential safety profile of our TCR-T therapy product candidates early in development before we initiate clinical trials.

ImmunoBank. We are expanding the ImmunoBank, our diverse repository of therapeutic TCRs, to allow formultiplex TCR-T therapy, which has the potential to address the heterogeneous nature of solid tumors and address resistance developing due to loss of a single HLA haplotype. We believe this approach may allow us to overcome the limitations and challenges of TCR-T development to date. We continue to prioritize expanding the ImmunoBank with TCRs for additional targets as well as multiple HLA types for each target, thus helping us overcome the key solid tumor resistance mechanisms of target loss and HLA loss. Finally, we are expanding the ImmunoBank to have the flexibility to be used with new and optimized methods of T cell engineering that we maydevelop over time. We have built the ImmunoBank to be compatible with autologous, allogeneic, and in vivo engineering technologies in order to potentially transition to generating off-the-shelf products for direct, customized administration to patients.

T-Integrate. Manufacturing cell therapies is highly complex, and associated challenges have led to significant delays or failures in the development ofmany cell therapies. To enable the rapid, cost-effective, and consistent manufacturing of TCR-T therapy product candidates, we have developed a non-viral vector delivery system that we refer to as T-Integrate. Our TCR-T therapy product candidates are manufactured using a transposon/transposase system, in which the DNA encoding the TCR is manufactured as a NanoplasmidTM, a non-viral vector. The Nanoplasmid, together with an mRNA sequence encoding a transposase enzyme, is introduced into the T cell by electroporation. After the T cell translates the mRNA into protein, the transposase enzyme inserts the TCR sequence from the Nanoplasmid, as well as any enhancements such as CD8a/b and DN-TGFbRII, into the genome of the T cell. This system is highly reproducible, as the only required components are a Nanoplasmid, which is different for each TCR product, and an mRNA, which is constant for all TCR products. Unlike lentivirus, both components are routinely manufactured in a cost-effective manner without the need for extensive process development.

We have a 51,100 square-foot GMP manufacturing facility (consisting of GMP clean room suites, laboratories, warehouse and office space) to manufacture clinical supply for our TCR-T therapy product candidates. Our manufacturing platform has enabled us to efficiently develop and manufacture many different TCR-T therapy product candidates, allowing us to deliver customized multiplex therapy to patients with cancer. We have successfully manufactured product candidates and have dosed patients in both our heme malignancies and solid tumor Phase 1 programs. The FDA has cleared eight IND applications for our solid tumor program, including our primary IND application T-Plex, which supports the use of multiple TCR-T therapy product candidates to create customized multiplex TCR-T therapy, as well as IND applications for TSC-200-A0201 (HPV16, HLA-A*02:01), TSC-201-B0702 (MAGE-C2, HLA-B*07:02), TSC-202 (MAGE-A4, HLA-A*02:01), TSC-203-A0201 (PRAME, HLA-A*02:01), TSC-204-A0201 (MAGE-A1, HLA-A*02:01), TSC-204-C0702 (MAGE-A1, HLA-C*07:02), and TSC-204-A0101 (MAGE-A1, HLA-A*01:01), demonstrating our manufacturing capabilities. To further increase our clinical manufacturing capacity and prepare for potential commercialization, we have engaged a global contract development and manufacturing organization, or CDMO, with worldwide commercial capabilities to support both the heme and solid tumor programs. The CDMO is on track to support clinical manufacturing of the heme program in the second half of 2025.

License and Collaboration Agreements

Collaboration Agreement with Amgen

On May 8, 2023, we entered into a Research Collaboration and License Agreement with Amgen Inc. (Amgen), or the Amgen Agreement, to identify antigens recognized by T cells in patients with Crohn’s disease utilizing our proprietary target discovery platform, or TargetScan. Under the terms of the Amgen Agreement, Amgen will then evaluate a variety of modalities to create therapeutics based on targets discovered by TScan and will retain all global development and commercialization rights. Amgen made an upfront payment of $30.0 million to us, and we are eligible to earn success-based milestone payments of over $500 million based upon the achievement of certain development and commercial milestones, as well as tiered single-digit royalty payments on net sales of products developed from the collaboration, subject to reductions set forth in the Amgen Agreement.

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Exclusive Patent License Agreement with BWH

On December 5, 2018, we entered into an Exclusive Patent License Agreement with The Brigham and Women’s Hospital, Inc., or BWH, as amended on July 26, 2019 and further amended and restated on April 20, 2021, or, collectively, the BWH Agreement, pursuant to which we obtained an exclusive, sublicensable, worldwide license to practice under certain of BWH’s patent rights for identifying T cell epitopes, which are relevant to our TargetScan technology for identifying potential therapeutic products. The original 2018 BWH Agreement granted us the right to practice BWH’s patent rights in a certain field of use, MHC Class I License Field. In connection with the amendment and restatement of the BWH Agreement in 2021, we expanded the field of use in which we are authorized to practice BWH’s patent rights to include MHC Class II uses and applications in exchange for certain additional payments to BWH. We are obligated to use commercially reasonable efforts to develop and commercialize at least one product or process that practices the licensed patent rights and at least one therapeutic or diagnostic product or process directed to an epitope identified through practicing the licensed patent rights.

Upon execution of the amendment of the BWH Agreement dated April 20, 2021, we paid an additional one-time fee of $466,500. We are required to pay BWH up to an aggregate of $12.72 million upon the achievement of certain clinical, regulatory and sales milestones for therapeutic products and processes. We are obligated to pay a low double-digit percentage of all non-royalty income we receive under sublicenses of BWH’s patent rights. We are also obligated to pay a low single-digit percentage of all non-royalty income we receive under agreements with third parties, or Collaborators, where we practice under BWH’s patent rights in connection with the research or development of one or more therapeutic products or processes with or for such third party, or Collaboration Agreements. We are also obligated to pay tiered royalties in the high single-digit percentage range on annual net sales of products and processes that practice the licensed patent rights and in the low single-digit percentage range on annual net sales of therapeutic and diagnostic products and processes directed to an epitope identified through practicing the licensed patent rights (other than those sold by Collaborators), with the royalty percentage for such products and processes decreasing to lower than one-percent royalties if directed to epitopes identified through practicing the licensed patent rights after December 31, 2019. For therapeutic and diagnostic products and processes directed to an epitope identified through practicing the licensed patent rights and sold by a Collaborator, we are obligated to pay lower than one-percent royalties of the Collaborator’s annual net sales of such products and processes. For products and processes sold by us, our affiliates or sublicensees, such royalties only apply to products and processes directed to epitopes in a defined field of use MHC Class I field identified prior to December 31, 2022, and products and processes based on epitopes in the MHC Class II field identified prior to September 30, 2023. For products or processes directed to epitopes identified under a Collaboration Agreement, such royalties apply regardless of when the epitopes were identified. For each applicable product or process, the royalty term continues until the tenth (10th) anniversary of the first commercial sale of such product or process. The royalty rates are also subject to reduction upon certain other events. Within 60 days of each anniversary of December 5th, we are obligated to pay BWH a non-refundable, mid-five-figure minimum annual royalty, which amount is creditable against royalties subsequently due on net sales of products and processes in such calendar year.

The BWH Agreement will terminate upon the later of (a) the last to expire or abandoned valid claim within the licensed patents, and (b) one year after the last sale for which a royalty is due. The current expected expiration date for the last-to-expire licensed patent right is June 8, 2038 (absent any adjustments or extensions of term). We also have the right to terminate the BWH Agreement in its entirety or on a country-by-country basis, for any reason upon 90 days’ prior written notice to BWH. BWH may terminate the BWH Agreement: (i) without notice if we fail to maintain insurance required by the BWH Agreement; (ii) upon notice within 60 days of our bankruptcy; (iii) upon notice within 60 days after notice by BWH of our default in the performance of any obligation under the BWH Agreement that is not cured within such 60-day period; (iv) if we fail to make any payments due under the BWH Agreement and do not cure such failure within 10 days after receiving BWH notice thereof; or (v) if we or any of our affiliates challenge the validity, enforceability or scope of any of the patent rights licensed to us under the BWH Agreement.

Non-Exclusive License Agreement with Provincial Health Services Authority

On October 15, 2020, we entered into a Non-Exclusive License Agreement with the Provincial Health Services Authority of British Columbia, or PHSA, and such agreement, the PHSA Agreement. Pursuant to the PHSA Agreement, we obtained a non-exclusive, perpetual, non-transferable, sublicensable, worldwide license to practice certain of PHSA’s patent rights for identifying T cell epitopes, which epitopes are relevant to our platform for identifying potential TCR-T therapy product candidates. Any sublicenses we grant to PHSA’s patent rights must also include a license of our own intellectual property; we are not permitted to sublicense PHSA’s rights on a standalone basis.

Pursuant to the PHSA Agreement, we paid PHSA a one-time, non-refundable upfront fee of $500,000 as well as reimbursement for previously incurred patent prosecution costs of approximately $50,000. Starting on the first anniversary of the effective date of the PHSA Agreement and continuing for five years thereafter, we are required to pay PHSA a mid-five-figure annual license fee, of which the first installment has been paid. In addition, we are obligated to pay a mid-six-figure fee for each sublicense and each further sublicense granted by one of our sublicensees or a sublicensee of our sublicensee (through multiple tiers) of the rights granted to us under the PHSA Agreement.

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The PHSA Agreement will terminate upon the last to expire patent licensed under the PHSA Agreement. We also have the right to terminate the PHSA Agreement at any time, but such termination will not be effective until the later of (a) October 16, 2023, and (b) the date we have paid PHSA total aggregate fees equal to the upfront fee plus five years of annual license fees totaling $750,000. PHSA may terminate the PHSA Agreement upon giving us two separate written notices at least 30 days apart if: (i) we or any of our affiliates challenge the validity, enforceability or scope of any of the patents licensed to us under the PHSA Agreement; (ii) we owe unpaid fees due under the PHSA Agreement in excess of $100,000; or (iii) we breach material terms of the PHSA Agreement regarding sublicense restrictions (such as failing to pay the sublicense fee or sublicensing PHSA technology on a standalone basis) or our obligation to indemnify PHSA for damages resulting from our research or commercialization of PHSA’s patent rights and, in each case described above, such termination will be effective only if we fail to cure such breach after receiving PHSA’s two separate notices.

Royalty Agreement

In connection with our incorporation in April 2018, we entered into a royalty agreement with one of our founders. We amended and restated this royalty agreement in June 2018, and our founder assigned his rights and obligations under the royalty agreement to one of his affiliated entities in January 2021. Pursuant to the royalty agreement, we are required to pay him a royalty of 1% of net sales (as defined in the royalty agreement) of any product sold by us or by any of our direct or indirect licensees for use in the treatment of any disease or disorder covered by a pending patent application or issued patent held or controlled by us as of the last date that the founder was providing services to us as a director or consultant under a written agreement. Royalties are payable with respect to each applicable product on a country-by-country and product-by-product basis, beginning on the first commercial sale of the first royalty-bearing product and ending on the later of (i) the date on which the exploitation of such royalty-bearing product is no longer covered by such patent in such country or (ii) the 15th anniversary of the first commercial sale of the first royalty-bearing product in such country. We may not assign our rights and obligations under the royalty agreement except in the event of a change in control relating to our company. The term of the royalty agreement continues until expiration of the last applicable royalty term.

Manufacturing

We have built in-house cell therapy manufacturing capabilities as one of the key components of our platform. The manufacturing of cell therapies requires the integration of several distinct components. Primary human blood cells are the source of T cells, along with a vector that delivers the desired genetic elements into these T cells. As a more operationally flexible and cost-efficient alternative to lentivirus, we have developed a manufacturing platform to genetically engineer T cells using a transposon/transposase system, which we refer to as T-Integrate.

We have designed our programs to use a transposon vector and corresponding transposase enzyme, which is derived from sfR fall armyworm, to deliver our TCRs into the genome of T cells. Our transposon/transposase system effectively inserts our TCRs and other exogenous genes, such as CD8, at random locations in the genome. The transposon is delivered as a NanoplasmidTM and has no antibiotic selection element, reducing the risk of inadvertent transmission of antibiotic resistance into T cells. The transposase is delivered as mRNA. mRNA is transiently expressed in the cell, reducing exposure of cells to prolonged transposase activity, which could result in multiple transposition events where the transposon would be moved around the genome.

We have developed a manufacturing process currently producing product for clinical studies, using industry standard equipment and instrumentation. The equipment and instrumentation used in our manufacturing facility allows for functionally closed processes in a small footprint. For clinical product manufacturing, we use single-use bag and tubing kits, supplies, and process reagents that are available from well-established vendors who specialize in supplying clinical grade reagents for the cell and gene therapy industry. Our TCR-T therapy product candidates are released and characterized using well-developed analytical methods. The final product used in clinical studies is cryopreserved, simplifying logistics and reducing risk of delivery failures to support patient dosing. We have controls and safeguards throughout the entire process to ensure product identity, integrity, sterility, and chain of custody. A clearly defined and documented manufacturing process, performed by trained operators using specialized instrumentation in an appropriately designed, commissioned, and operated manufacturing facility is critical for the manufacturing of safe, effective, and well-characterized cell therapies.

Our cell product manufacturing facility in Waltham, MA has been designed and built to support multiple programs through Phase 1 and Phase 2 clinical development, with a projected capacity to support up to 250 TCR-T components per year. We believe internalizing our manufacturing process and product testing enables us to better control this key aspect of clinical development and reduces the risk of program delay due to third-party reliance. We continue to refine our manufacturing process to ensure it is commercially viable with focus on cost, consistency, and manufacturing success rate. We have engaged a CDMO with global capabilities to support increased capacity and potential commercial manufacturing. The CDMO is on track to support clinical manufacturing of the heme program in the second half of 2025.

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Competition

We believe our novel and proprietary platform technologies, TargetScan, SafetyScan, and ReceptorScan, and our in-house cell therapy expertise constitute a meaningful competitive advantage in successfully developing novel and highly safe and effective treatments for cancer. However, the biopharmaceutical industry in general, and the cell therapy field in particular, is characterized by rapidly advancing and changing technologies, intense competition, and a strong emphasis on intellectual property. We face substantial and increasing competition from many different sources, including large and specialty biopharmaceutical companies, academic research institutions, governmental agencies, and public and private research institutions. Competitors may compete with us in hiring scientific and management personnel, establishing clinical study sites, recruiting patients to participate in clinical trials, and acquiring technologies complementary to, or necessary for, our programs.

We face competition from segments of the pharmaceutical, biotechnology and other related markets that pursue the development of TCR-based or cell-based therapies for the treatment of cancer. We expect to compete with a number of other TCR-based companies, utilizing both cell therapy and other therapeutic modalities, such as Immatics N.V., Adaptimmune Therapeutics, Plc., Affini-T Therapeutics, Inc., Medigene AG, T-Knife GmbH, Enara Bio Ltd., Immunocore Holdings, Plc., and 3T Biosciences Inc. We may also face competition from companies focused on other T cell therapies (e.g., TIL, CAR-T, gammadelta T cells) such as Iovance Biotherapeutics, Inc., Instil Bio, Inc., Achilles Therapeutics plc, Kite Pharma, Inc., a subsidiary of Gilead, Inc. (including Yescarta, which is approved for the treatment for large B cell lymphoma or follicular lymphoma, two types of non-Hodgkin lymphoma), Juno Therapeutics, Inc., a subsidiary of Bristol-Myers Squibb, Inc., Regeneron Pharmaceuticals, Inc., through their acquisition of 2seventy Bio, Inc.’s research pipeline, AstraZeneca plc, through their acquisition of Gracell Biotechnologies, Inc., Legend Biotech Corporation, Autolus Therapeutics plc, Sana Biotechnology, Inc., Lyell Immunopharma, Inc., Allogene Therapeutics, Inc., Century Therapeutics, Inc., and Adicet Bio, Inc. There are also companies utilizing other cell-based approaches that may be competitive to our product candidates. For example, companies such as Takeda Pharmaceutical Company, Ltd., Celyad, S.A., ImmunityBio, Inc., Celularity, Inc., Fate Therapeutics, Inc., and Nkarta, Inc. are developing therapies that target and/or engineer natural killer, or NK, cells. In addition, for our lead programs, TSC-100 and TSC-101, we may face competition from BlueSphere Bio, VOR Biopharma, Inc., IN8bio, Inc., Orca Biosystems, Inc., and Marker Therapeutics, Inc., who are also developing cell therapies in the post-HCT setting. The named companies are not fully inclusive of all possible competitive threats.

Furthermore, we also face competition more broadly across the oncology market for cost-effective and reimbursable cancer treatments. The most common methods of treating patients with cancer are surgery, radiation, and drug therapy, including chemotherapy, hormone therapy, biologic therapy, such as monoclonal and bispecific antibodies, immunotherapy, cell-based therapy, and targeted therapy, or a combination of any such treatments. There are a variety of available drug therapies marketed for cancer. In many cases, these drugs are administered in combination to enhance efficacy. While our TCR-T therapy product candidates, if any are approved, may compete with these existing drugs and other therapies, to the extent they are ultimately used in combination with or as an adjunct to these therapies, our TCR-T therapy product candidates may not be competitive with them. Some of these drugs are branded and subject to patent protection, and others are available on a generic basis. As a result, obtaining market acceptance of, and gaining a significant share of the market for, and commanding a certain price for any of our TCR-T therapy product candidates that we successfully introduce to the market may pose challenges. In addition, many companies are developing new oncology therapeutics, and we cannot predict what the standard of care will be as our product candidates progress through clinical development.

We could see a reduction or elimination in our commercial opportunity if our competitors develop and commercialize drugs that are safer, more effective, have fewer or less severe side effects, are more convenient to administer, are less expensive, are more accessible, or receive a more favorable label than our TCR-T therapy product candidates. Our competitors also may obtain FDA or other regulatory approval for their drugs more rapidly than we may obtain approval for ours, which could result in our competitors establishing a strong market position before we are able to enter the market. The key competitive factors affecting the success of all of our TCR-T therapy product candidates, if approved, are likely to be their efficacy, safety, convenience, accessibility, price, and the availability of reimbursement from government and other third-party payors.

Intellectual Property

Our success depends in part on our ability to obtain, maintain and protect our proprietary technology and intellectual property and proprietary rights and to operate our business without infringing, misappropriating and otherwise violating the intellectual property and proprietary rights of third parties. We rely on a combination of patent applications, trademarks, trade secrets, and other intellectual property rights and measures to protect the intellectual property rights that we consider important to our business. We also rely on know-how and continuing technological innovation to develop and maintain our competitive position. We also seek to protect our proprietary rights by entering into confidentiality agreements and proprietary information agreements with suppliers, employees, consultants and others who may have access to our proprietary information. The steps we have taken to protect our trade secrets, trademarks, patent applications and other intellectual property and proprietary rights may not be adequate, and third parties could infringe, misappropriate

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or misuse our intellectual property. If this were to occur, it could harm our reputation and adversely affect our business, competitive position, financial condition or results of operations.

As of the date hereof, our patent portfolio includes a patent family exclusively licensed from BWH, including a granted U.S. patent, a pending U.S. non-provisional patent application, and multiple foreign granted patents and non-provisional patent applications, relating to methods and compositions for identifying target antigens specific to T cells. In addition, we have filed applications in multiple patent families including multiple pending U.S. provisional patent applications, multiple granted foreign patents, and more than 140 pending international and foreign patent applications. The claims of these patent applications are directed toward various aspects of our therapy candidates and research programs, including compositions of matter and uses thereof directed to SARS-CoV-2 immunodominant antigens, anti-SARS-CoV-2 TCRs, anti-SARS-CoV-2 vaccines, anti-HA-1 TCRs (including the TSC-100 TCR-T therapy product candidate), anti-HA-2 TCRs (including the TSC-101 TCR-T therapy product candidate), anti-HPV TCRs (including the TSC-200 TCR-T therapy product candidate), anti-MAGE-C2 TCRs (including the TSC-201 TCR-T therapy product candidate), anti-MAGE-A4 TCRs (including the TSC-202 TCR-T therapy product candidate), anti-PRAME TCRs (including the TSC-203 TCR-T therapy product candidate), and anti-MAGE-A1 TCRs (including the TSC-204 TCR-T therapy product candidate), as well as platform technologies including a phospholipid scrambling reporter-based T cell antigen screening platform and certain screening methods thereof, and a TCR multiplexing platform and certain therapeutic methods thereof. These patent applications, if issued, are expected to expire on various dates from 2038 through 2045, in each case without taking into account any possible patent term adjustments or extensions and assuming that appropriate maintenance and governmental fees are paid.

Heme Malignancies Program Product Patent Families

We have filed multiple patent families encompassing pending U.S. and foreign patent applications covering aspects of our heme malignancies programs including claims to the composition-of-matter and uses thereof of TSC-100, TSC-101, and other anti-HA-1 and anti-HA-2 TCRs and related T cell therapies. We expect the issued Australian and Singaporean patents, as well as any additional patents within these families, if issued, to expire no earlier than 2041 (without taking into account any possible patent term adjustments or extensions and assuming that appropriate maintenance and governmental fees are paid).

Solid Tumor Program Product Patent Families

We have filed multiple patent families encompassing pending U.S. and foreign patent applications covering aspects of our solid tumor programs including claims to the composition-of-matter of anti-HPV, anti-MAGE-C2, anti-MAGE-A4, anti-PRAME, anti-MAGE-A1 TCRs, and related T cell therapies. We expect the issued Australian patents, as well as any additional patents within these families, if issued, to expire no earlier than 2042 (without taking into account any possible patent term adjustments or extensions and assuming that appropriate maintenance and governmental fees are paid).

Infectious Disease Product Patent Families

We have filed multiple patent families encompassing pending U.S. and foreign patent applications covering aspects of our infectious disease programs including claims to the composition-of-matter of SARS-CoV-2 immunodominant antigens, anti-SARS-CoV-2 TCRs, and the composition-of-matter of certain SARS-CoV-2 vaccines. We expect the issued Australian and Democratic Republic of the Congo patents, as well as any additional patents within these families, if issued, to expire no earlier than 2041 (without taking into account any possible patent term adjustments or extensions and assuming that appropriate maintenance and governmental fees are paid). Certain of these pending patent applications are jointly owned by us and AHS Hospital Corporation, or AHS. AHS has exclusively licensed their interest in such patent applications to us.

Platform Technology

We have filed a patent family encompassing pending U.S. and foreign patent applications covering aspects of our reporter-based T cell antigen screening platform. We expect any claims within this family, if issued, to expire no earlier than 2041 (without taking into account any possible patent term adjustments or extensions and assuming that appropriate maintenance and governmental fees are paid).

In addition, we have filed several patent families encompassing pending U.S. and foreign patent applications covering certain multiplexed TCR compositions and certain therapeutic methods thereof. We expect any claims within these families, if issued, to expire no earlier than 2043 (without taking into account any possible patent term adjustments or extensions and assuming that appropriate maintenance and governmental fees are paid).

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Our pending patent applications may not result in issued patents and we can give no assurance that any patents that might issue in the future will protect our products or provide us with any competitive advantage. Moreover, U.S. provisional patent applications are not eligible to become issued patents until, among other things, we file a non-provisional patent application within 12 months of filing of one or more of our related provisional patent applications. With regard to such U.S. provisional patent applications, if we do not timely file any non-provisional patent applications, we may lose our priority date with respect to our provisional patent applications and any patent protection on the inventions disclosed in our provisional patent applications. While we generally intend to timely file non-provisional patent applications relating to our provisional patent applications, we cannot predict whether any such patent applications will result in the issuance of patents that provide us with any competitive advantage. For more information regarding the risks related to our intellectual property, please see “Item 1A. Risk Factors—Risks Related to Our Intellectual Property” in this Annual Report.

Third-Party Intellectual Property Rights

For certain aspects of our business, we rely on certain technology and intellectual property rights that we in-license from third parties. We have an exclusive patent license from BWH to a patent family directed to aspects of a granzyme B (GzB)-based antigen screening technology platform, as well as compositions-of-matter and certain screening methods thereof (consisting of one granted U.S. patent, one pending U.S. patent application, a granted patent in each of Australia, France, Germany, Great Britain, Japan, Netherlands, Switzerland, and six foreign patent applications pending in Australia, Canada, China, Europe, Hong Kong, and Japan). Any patents issuing from the U.S. and foreign patent applications are expected to expire no earlier than 2038 (without taking into account any possible patent term adjustments or extensions and assuming that appropriate maintenance and governmental fees are paid). We also have a non-exclusive, perpetual, non-transferable patent license from PHSA to a patent family directed to granzyme-based antigen screening methods consisting of an issued U.S. patent that is expected to expire on August 4, 2035 (assuming that appropriate maintenance and governmental fees are paid) and issued Canadian patent that is expected to expire March 25, 2035 (assuming that appropriate maintenance and governmental fees are paid).

As of the date hereof, we own or have rights to U.S. and foreign trademark registrations and applications that cover certain aspects of our business.

Government Regulation

FDA Regulation and Marketing Approval

In the U.S., the FDA regulates drugs under the Federal Food, Drug and Cosmetic Act, or FDCA, and biologics under the Public Health Service Act, the regulations promulgated under both laws and other federal, state, and local statutes and regulations. Failure to comply with the applicable U.S. regulatory requirements at any time during the product development process, approval process or after approval may subject an applicant to administrative or judicial sanctions and non-approval of product candidates. These sanctions could include, among other things, the imposition by the FDA of a clinical hold on trials, the FDA’s refusal to approve pending applications or related supplements, withdrawal of an approval, untitled or warning letters, product recalls, product seizures, total or partial suspension of production or distribution, injunctions, fines, restitution, disgorgement, civil penalties, or criminal prosecution. Such actions by government agencies could also require us to expend a large amount of resources to respond to the actions. Any agency or judicial enforcement action could have a material adverse effect on us.

The FDA and comparable regulatory agencies in state and local jurisdictions and in foreign countries impose substantial requirements upon the clinical development, approval, manufacture, distribution and marketing of pharmaceutical products. These agencies and other federal, state and local entities regulate research and development activities and the testing, manufacture, quality control, safety, effectiveness, labeling, packaging, storage, distribution, record keeping, approval, post-approval monitoring, advertising, promotion, sampling and import and export of our products. Our drugs must be approved by the FDA as biologics through the BLA approval process applicable to gene therapy product candidates before they may be legally marketed in the U.S.

Within the FDA, the FDA’s Center for Biologics Evaluation and Research, or CBER, regulates gene therapy products and has published guidance documents with respect to the development of these types of products. The FDA also has published guidance documents related to, among other things, gene therapy products in general, their preclinical assessment, observing subjects involved in gene therapy studies for delayed adverse events, potency testing, and chemistry, manufacturing and control information in gene therapy INDs.

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The process required by the FDA before a biologic may be marketed in the U.S. generally involves the following:

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completion of non-clinical laboratory tests, animal studies and formulation studies conducted according to Good Laboratory Practice, or GLP, or other applicable regulations;

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submission of an IND application, which allows clinical trials to begin unless the FDA objects within 30 days;

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performance of adequate and well-controlled human clinical trials to establish the safety and efficacy of the proposed drug or biologic for its intended use or uses conducted in accordance with FDA regulations and Good Clinical Practices, or GCP, which are international ethical and scientific quality standards meant to ensure that the rights, safety and well-being of trial participants are protected, and that the integrity of the data is maintained;

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preparation and submission to the FDA of a BLA;

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submission of a user fee for FDA review of the BLA;

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review of the product by an FDA advisory committee, where appropriate or if applicable;

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satisfactory completion of pre-approval inspection of manufacturing facilities and clinical trial sites at which the product, or components thereof, are produced to assess compliance with current Good Manufacturing Practice, or cGMP, requirements, and if applicable, the FDA’s current Good Tissue Practice, or cGTP, requirements, and of selected clinical trial sites to assess compliance with GCP requirements; and

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FDA approval of a BLA which must occur before a biologic can be marketed or sold.

Preclinical Studies

Preclinical studies include laboratory evaluation of the purity and stability of the manufactured drug substance or active pharmaceutical ingredient and the formulated drug or drug product, as well as in vitro and animal studies to assess the safety and activity of the drug for initial testing in humans and to establish a rationale for therapeutic use. The conduct of preclinical studies is subject to federal regulations and requirements, including GLP regulations. The results of the preclinical tests, together with manufacturing information, analytical data, any available clinical data or literature and plans for clinical studies, among other things, are submitted to the FDA as part of an IND application.

Companies usually must complete some long-term preclinical testing, such as animal tests of reproductive adverse events and carcinogenicity and must also develop additional information about the chemistry and physical characteristics of the drug and finalize a process for manufacturing the drug in commercial quantities in accordance with, or cGMP, requirements. The manufacturing process must be capable of consistently producing quality batches of the drug candidate and, among other things, the manufacturer must develop methods for testing the identity, strength, quality, and purity of the final drug product. Additionally, appropriate packaging must be selected and tested, and stability studies must be conducted to demonstrate that the drug candidate does not undergo unacceptable deterioration over its shelf life.

IND Application and Clinical Trials

Clinical trials involve the administration of the investigational product to human subjects under the supervision of qualified investigators in accordance with GCP requirements. Clinical trials are conducted under written study protocols detailing, among other things, the objectives of the study, the parameters to be used in monitoring safety and the effectiveness criteria to be evaluated. Prior to commencing the first clinical trial, an initial IND application, which contains the results of preclinical testing along with other information, such as information about product chemistry, manufacturing and controls and a proposed protocol, must be submitted to the FDA. The IND application automatically becomes effective 30 days after receipt by the FDA unless the FDA, within the 30-day time period, raises concerns or questions about the drug product or the conduct of the clinical trial and imposes a clinical hold. A clinical hold may also be imposed at any time while the IND application is in effect. In such a case, the IND application sponsor must resolve any outstanding concerns with the FDA before the clinical trial may begin or re-commence. Accordingly, submission of an IND application may or may not result in the FDA allowing clinical trials to commence or continue.

In addition to the submission of an IND application to the FDA before initiation of a clinical trial in the U.S., certain human clinical trials involving recombinant or synthetic nucleic acid molecules are subject to oversight of institutional biosafety committees, or IBCs, as set forth in the National Institutes for Health, or NIH, Guidelines for Research Involving Recombinant or Synthetic Nucleic Acid Molecules, or NIH Guidelines. Under the NIH Guidelines, recombinant and synthetic nucleic acids are defined as: (i) molecules that are constructed by joining nucleic acid molecules and that can replicate in a living cell (i.e., recombinant nucleic acids); (ii) nucleic acid molecules that are chemically or by other means synthesized or amplified, including those that are chemically or otherwise modified but can base pair with naturally occurring nucleic acid molecules (i.e., synthetic nucleic acids); or (iii) molecules that result from the replication of those described in (i) or (ii). Specifically, under the NIH Guidelines, supervision of human gene transfer trials includes

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evaluation and assessment by an Institutional Biosafety Committee (IBC), a local institutional committee that reviews and oversees research utilizing recombinant or synthetic nucleic acid molecules at that institution. The IBC assesses the safety of the research and identifies any potential risk to public health or the environment, and such review may result in some delay before initiation of a clinical trial. While the NIH Guidelines are not mandatory unless the research in question is being conducted at or sponsored by institutions receiving NIH funding of recombinant or synthetic nucleic acid molecule research, many companies and other institutions not otherwise subject to the NIH Guidelines voluntarily follow them.

A sponsor who wishes to conduct a clinical trial outside the U.S. may, but need not, obtain FDA authorization to conduct the clinical trial under an IND application. If a foreign clinical trial is not conducted under an IND application, the sponsor may submit data from the clinical trial to the FDA in support of a BLA or IND application so long as the clinical trial is conducted in compliance with GCP, and the FDA is able to validate the data from the study through an onsite inspection if the agency deems it necessary.

A separate submission to the existing IND application must be made for each successive clinical trial to be conducted during product development. Further, an independent Institutional Review Board, or IRB, for each site at which the clinical trial will be conducted must review and approve the clinical trial before it commences at that site. Informed written consent must also be obtained from each trial subject. Regulatory authorities including the FDA, or IRB, or the sponsor, may suspend or terminate a clinical trial at any time on various grounds, including a finding that the participants are being exposed to an unacceptable health risk or that the clinical trial is not being conducted in accordance with FDA requirements. Additionally, some clinical trials are overseen by an independent group of qualified experts organized by the clinical trial sponsor, known as a data safety monitoring board or committee. This group provides authorization as to whether or not a trial may move forward at designated check points based on access to certain data from the trial and may recommend halting the clinical trial if it determines that there is an unacceptable safety risk for subjects or other grounds, such as no demonstration of efficacy.

Human clinical trials for BLA approval typically involve a three-phase process, although some phases may overlap or be combined. Phase 1, the initial clinical evaluations, consists of administering the drug and testing for safety and tolerated dosages and in some indications, such as rare disease, as preliminary evidence of efficacy in humans. Phase 2 involves a study to evaluate the effectiveness of the drug for a particular indication and to determine optimal dosage and dose interval and to identify possible adverse side effects and risks in a larger patient group. When a product is found safe, and initial efficacy is established in Phase 2, it is then evaluated in Phase 3 clinical trials. Phase 3 trials consist of expanded multi-location testing for efficacy and safety to evaluate the overall benefit-to-risk index of the investigational drug in relationship to the disease treated. In March 2022, the FDA released a final guidance, “Expansion Cohorts: Use in First-In-Human Clinical Trials to Expedite Development of Oncology Drugs and Biologics,” which outlines how drug developers can utilize an adaptive trial design in early stages of oncology drug development (i.e., the first-in-human clinical trial) to compress the traditional three phases of trials into one continuous trial called an expansion cohort trial. Expansion cohort trials can potentially bring efficiency to drug development and reduce developmental costs and time.

All clinical trials must be conducted in accordance with FDA regulations, GCP requirements and their protocols in order for the data to be considered reliable for regulatory purposes. Progress reports detailing the results of the clinical trials must be submitted at least annually to the FDA and more frequently if serious adverse events occur. The results of preclinical and human clinical testing are submitted to the FDA in the form of a BLA for approval to commence commercial sales. Our clinical trials may not be completed successfully within any specified period, or at all. Government regulation may delay or prevent marketing of product candidates or new drugs for a considerable period of time and impose costly procedures upon our activities.

Disclosure of Clinical Trial Information

Sponsors of clinical trials of FDA-regulated products, including drugs, are required to register and disclose certain clinical trial information. Information related to the product, patient population, phase of investigation, study sites and investigators, and other aspects of the clinical trial is then made public as part of the registration. Sponsors are also obligated to disclose the results of their clinical trials after completion. Disclosure of the results of these trials can be delayed until the new product or new indication being studied has been approved up to a maximum of two years. Competitors may use this publicly available information to gain knowledge regarding the progress of development programs.

The Biologics License Application Approval Process

In order to obtain approval to market a drug in the U.S., a marketing application must be submitted to the FDA that provides data establishing to the FDA’s satisfaction the safety and effectiveness of the investigational drug for the proposed indication. The application includes all relevant data available from pertinent non-clinical or preclinical studies and clinical trials, including negative or ambiguous results as well as positive findings, together with detailed information relating to the product’s chemistry, manufacturing, controls and proposed labeling, among other things. Data can come from company-sponsored clinical trials intended to test the safety and effectiveness of a use of a product, or from a number of alternative sources, including studies initiated by investigators that meet GCP requirements.

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During the development of a new drug, sponsors are given opportunities to meet with the FDA at certain points. These points may be prior to submission of an IND application, at the End-of-Phase 1 or 2, and before a Biologics License Application, or BLA, is submitted. Meetings at other times may be requested. These meetings can provide an opportunity for the sponsor to share information about the data gathered to date, for the FDA to provide advice and for the sponsor and the FDA to reach agreement on the next phase of development.

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