10-K

UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

FORM 10-K

(Mark One)

For the fiscal year ended December 31, 2021

Commission File Number 001-40603

TSCAN THERAPEUTICS, INC.

(Exact name of Registrant as specified in its Charter)

830 Winter StreetWaltham, Massachusetts 02451c

(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. ☐

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

As of June 30, 2021, the last business date of the registrant's most recently completed second quarter, there was no public market for the registrant's common stock. 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 Stock market on March 4, 2022, was approximately $64,227,891.

The number of shares of Registrant’s Common Stock outstanding as of March 4, 2022 was 23,976,942.

DOCUMENTS INCORPORATED BY REFERENCE

Portions of the registrant’s proxy statement for the 2022 annual meeting of stockholders to be filed pursuant to Regulation 14A within 120 days after the registrant’s fiscal year ended December 31, 2021, are incorporated by reference in Part III of this Form 10-K.

Table of Contents

Page

PART I.

Item 1. Business 3

Item 1A. Risk Factors 58

Item 1B. Unresolved Staff Comments 117

Item 2. Properties 117

Item 3. Legal Proceedings 117

Item 4. Mine Safety Disclosures 117

PART II.

Item 6. [Reserved] 118

Item 7A. Quantitative and Qualitative Data About Market Risk 130

Item 8. Financial Statements and Supplementary Data 130

Item 9A. Controls and Procedures 130

Item 9B. Other Information 130

PART III.

Item 10. Directors, Executive Officers and Corporate Governance 131

Item 11. Executive Compensation 131

Item 14. Principal Accounting Fees and Services 131

PART IV.

Item 15. Exhibits, Financial Statement Schedules 132

SPECIAL NOTE REGARDING FORWARD-LOOKING STATEMENTS

This Annual Report on Form 10-K, or Annual Report, including the section titled “Management’s Discussion and Analysis of Financial Condition and Results of Operations,” as well as information included in oral statements or other written statements made or to be made by us, 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, that involve substantial risks and uncertainties. All statements other than statements of historical facts contained in this Annual Report, including statements regarding our future results of operations and financial position, future revenue, business strategy, prospects, product candidates, planned preclinical studies and clinical trials, results of clinical trials, research and development costs, regulatory approvals, timing and likelihood of success, as well as plans and objectives of management for future operations, are forward-looking statements. These statements involve known and unknown risks, uncertainties and other important factors that are in some cases beyond our control and may cause our actual results, performance or achievements to be materially different from any future results, performance or achievements expressed or implied by the forward-looking statements.

The words “may,” “will,” “should,” “would,” “expect,” “plan,” “anticipate,” “could,” “intend,” “target,” “project,” “contemplate,” “believe,” “estimate,” “predict,” “potential” or “continue” or the negative of these terms or other similar expressions are intended to identify forward-looking statements. Forward-looking statements contained in this Annual Report include, but are not limited to, express or implied statements about:

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the beneficial characteristics, safety, efficacy, therapeutic effects and potential advantages of our T cell receptor-engineered T cell, or TCR-T, therapy 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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our plans relating to developing and commercializing our TCR-T therapy candidates, if approved, including sales strategy;

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estimates of the size of the addressable market for our TCR-T therapy 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 United States 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 effect of the COVID-19 pandemic, including mitigation efforts and political, economic, legal and social effects, on any of the foregoing or other aspects of our business or operations; and

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

These forward-looking statements are subject to a number of risks, uncertainties and assumptions, including those described in the section titled “Risk Factors” and elsewhere in this Annual Report. 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. 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 reference in this Annual Report and have filed with the SEC 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.

PART I

Item 1. Business

Overview

We are a clinical-stage biopharmaceutical company focused on developing a robust pipeline of T cell receptor-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 in order to treat those who are not. Using one of our proprietary platform technologies, TargetScan, we analyze the T cells of cancer patients with exceptional responses to immunotherapy to discover how the immune system naturally recognizes and eliminates tumor cells in these patients. This allows us to precisely identify the targets of T cell receptors, or TCRs, that are driving these exceptional responses. We aim to use these anti-cancer TCRs to treat patients with cancer by genetically engineering their own T cells to recognize and eliminate their cancer. In addition to discovering TCR-T therapies against novel targets, we are using our ReceptorScan technology to further diversify our portfolio of therapeutic TCRs with TCR-T therapies against known targets. We reduce the risk and enhance the safety profile of these therapeutic TCRs by screening them using SafetyScan to identify potential off-targets of a TCR and eliminate those TCR candidates that cross-react with proteins expressed at high levels in critical organs.

We believe this three-pronged approach will enable us to discover and develop a wide array of potential treatment options for patients with cancer.

We are advancing a robust pipeline of TCR-T therapy candidates for the treatment of patients with hematologic and solid tumor malignancies. Our lead liquid tumor product candidates, TSC-100 and TSC-101, are in development for the treatment of patients with hematologic malignancies to eliminate residual leukemia and prevent relapse following hematopoietic stem cell transplantation, or HCT. TSC-100 and TSC-101 target HA-1 and HA-2 antigens, respectively, which are well-recognized TCR targets that were identified in patients with exceptional responses to HCT-associated immunotherapy. We submitted Investigational New Drug, or IND, applications with the U.S. Food and Drug Administration, or FDA, for each of TSC-100 and TSC-101 in the fourth quarter of 2021. The FDA has cleared the IND for TSC-100 while the IND for TSC-101 remains on clinical hold pending additional assessment of the potential for off-tumor reactivity in certain tissues. We plan to initiate the Phase 1 clinical study of TSC-100 in the first half of 2022. Pending clearance of the IND for TSC-101, we will initiate the TSC-101 arm of the trial. In addition, we are developing multiple TCR-T therapy candidates for the treatment of solid tumors. One of the key goals for our solid tumor program is to develop what we refer to as multiplexed TCR-T therapy. We are designing these multiplexed therapies to be a combination of up to three highly active TCRs that are customized for each patient and selected from our bank of therapeutic TCRs, which we refer to as ImmunoBank. We plan to populate the ImmunoBank with TCRs for multiple targets as well as multiple HLA types for each target, thus helping us to overcome the key solid tumor resistance mechanisms of target loss as well as HLA loss. We are currently advancing five solid tumor programs: TSC-200 in IND-enabling activities; TSC-204 advancing to IND-enabling studies; and TSC-201, TSC-202, and TSC-203, in lead optimization. We expect to submit two IND applications for our solid tumor TCR-T therapy candidates in the second half of 2022, with additional IND applications expected to be submitted in 2023.

T cells are an essential component of the adaptive immune system and provide protection against cancer, infection, and autoimmune disease. Multiple approaches have been and are continuing to be explored to develop effective T cell-based therapies for the treatment of cancer, including tumor infiltrating lymphocyte, or TIL, therapy and chimeric antigen receptor T cell, or CAR-T, therapy. The success of TIL therapy depends on the specific T cells present in the patient. If their TILs 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 liquid tumors. In contrast, CAR-T therapy has proven effective in certain hematological malignancies of lymphoid origin but have not yet shown efficacy or safety in myeloid malignancies. Additionally, this type of treatment is limited to targets on the surface of tumor cells and has not yet been shown to effectively penetrate solid tumors. Both TIL and CAR-T therapies, as well as other immunotherapies such as checkpoint inhibitors, harness the power of cytotoxic T cells in fighting cancer. Despite demonstrating 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.

Our decision to develop TCR-T therapies for the treatment of cancer is based on our conviction that we can learn from the natural interaction between T cells and tumor cells and harness this information to treat patients by reprogramming their immune systems. We believe that TCR-T therapy combines the benefits of TIL and CAR-T therapies while uniquely addressing their key limitations.

The development of TCR-T therapy requires three key prerequisites: (i) an effective anti-cancer TCR; (ii) knowledge of the precise peptide antigen, a protein or other molecule to which an antibody binds, that is recognized by the TCR; and (iii) confirmation that the TCR does not recognize problematic off-targets. We believe that our approach provides us with the following key advantages:

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Our TCR-T therapies 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 therapies 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 therapies are designed to be used in combination with each other. We are building our diverse ImmunoBank of TCRs to allow formultiplexed TCR-T therapy, which has the potential to address the heterogeneous nature of solid tumors and to prevent 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 therapy development to date. We plan to populate ImmunoBank with TCRs for multiple targets as well as multiple HLA types for each target, thus helping us to overcome the key solid tumor resistance mechanisms of target loss as well as HLA loss.

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Our approach is expandable. ImmunoBank has the flexibility to be used with new and optimized methods of T cell engineering that we maydevelop over time. We are building 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.

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-targets of TCRs to eliminate candidates that could potentially pose a safety risk; and (v) manufacture TCR-T therapies efficiently and consistently without the use of viral vectors using our T-Integrate technology. The central elements of our platform that differentiate us from other cell therapy companies are TargetScan, ReceptorScan, SafetyScan, 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 more than 60 shared antigens in patient tumors, and over 90% of these targets have not previously been publicly identified as targets for TCR-T therapy. 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 also we have already identified highly active TCRs that recognize these targets.

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 critical organs. We believe this will allow us to reduce the risk and enhance the potential safety profile of our TCR-T therapy candidates early in development before we initiate clinical trials.

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 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 candidates, TSC-100 targeting HA-1 and TSC-101 targeting HA-2, as well as our other pipeline programs.

ImmunoBank. We are building ImmunoBank, our diverse bank of therapeutic TCRs, to allow formultiplexed TCR-T therapy, which has the potential to address the heterogeneous nature of solid tumors and to prevent resistance developing due to loss of a single haplotype target. We believe this approach may allow us to overcome the limitations and challenges of TCR-T therapy development to date. We plan to populate the ImmunoBank with TCRs for multiple targets as well as multiple HLA types for each target, thus helping us to overcome the key solid tumor resistance mechanisms of target loss as well as HLA loss. Finally, we are building ImmunoBank to have the flexibility to be used with new and optimized methods of T-cell engineering that we maydevelop over time. We are building 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.

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-Ts, we have developed a non-viral vector delivery system that we refer to as T-Integrate. Our TCR-T therapy 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 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 of these components are routinely manufactured in a cost-effective manner without the need for extensive process development.

We have completed the construction and validation of a 7,000 square-foot state-of-the-art good manufacturing practices, or GMP, manufacturing facility to manufacture all necessary Phase 1 and 2 supply for our TCR-T therapies. We expect that this facility will provide sufficient production capacity to supply product for all planned Phase 1 and 2 clinical studies for the liquid and solid tumor programs. Approval of our IND for TSC-100 validates our facility for human manufacturing of our T cell therapies. We believe our manufacturing platform will enable us to efficiently develop and manufacture many different TCR-T therapies, allowing us to deliver customized multiplexed therapy to patients with cancer.

Our Pipeline

We are building ImmunoBank with the goal of delivering customized multiplexed TCR-T therapies to a wide range of patients with cancer. In addition, we are applying our platform to identify targets and TCRs in therapeutic areas outside of oncology, such as

autoimmune disorders and infectious disease, through strategic partnerships. Our current proprietary pipeline is summarized in the figure below.

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 and license agreement with Novartis Institutes for BioMedical Research, Inc., or Novartis, to identify novel cancer antigens from the T cells of patients with a certain specific type of cancer. Novartis has the option to license and develop therapies for up to three of the targets discovered in the collaboration. Should Novartis license a target, we are eligible for a payment of $10 million per target as well as future milestones and royalties. In addition, we have partnered with QIAGEN Sciences, LLC to develop a highly specific diagnostic test to determine prior exposure to SARS-CoV-2 based on the presence of anti-viral T cells.

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

Our Liquid Tumor Program. We are developing our liquid tumor program to treat patients with hematologic malignancies 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.

In the fourth quarter of 2021, we submitted IND applications with the FDA for our lead TCR-T therapy candidates, TSC-100 and TSC-101. The FDA cleared the IND for TSC-100 in January 2022, while the IND for TSC-101 remains on clinical hold. For TSC-101, we received written communication from the FDA asking for additional assessment of the potential for off-tumor reactivity in certain tissues and are working with the agency to resolve its questions as quickly as possible. The liquid tumor trial is based on an umbrella protocol, which will allow us to begin the TSC-100 and control arms of the trial in the near term and to open the TSC-101 arm to the ongoing trial upon clearance of the IND. We plan to initiate the Phase 1 clinical study of TSC-100 in the first half of 2022. Pending clearance of the IND for TSC-101, we will then initiate the TSC-101 arm of the trial, allowing for us to advance TSC-100 into Phase 1 clinical trials. 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, will be eligible for enrollment. Furthermore, eligible patients will require donors who are negative for either the target antigen or the HLA-A*02:01 allele.

Through the development of our liquid tumor program, we are building a foundation of manufacturing, clinical, and regulatory capabilities, which will be applied to the future development of our broader portfolio of TCR-T therapy candidates for solid tumors. With the FDA clearance of our IND for TSC-100, we believe our approach has been validated.

Our Solid Tumor Program. We are developing a portfolio of autologous TCR-T therapy candidates that are designed to be used incombination with each other to treat and eliminate solid tumors. Our TSC-200 series of product candidates are designed to elicit anti-tumor responses in patients by targeting cancer-specific antigens in their tumor cells. Our TCR-T therapy candidates

include: (i) either well-recognized cancer targets that have demonstrated anti-tumor activity in clinical trials or 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 five product candidates include a combination of known targets, such as HPV16 for TSC-200, PRAME for TSC-203, and MAGE-A1 for TSC-204, as well as targets that are novel antigens for TCR-T therapy, such as for TSC-201 and TSC-202. In addition to our five lead product candidates, we have identified over 60 novel antigens based on tumor samples from patients who are actively responding to immunotherapy using our TargetScan technology. We are in early stages of analyzing these additional novel antigens and plan to advance those that we believe have the best potential as a TCR-T product candidate into preclinical development.

Our vision is to create and continuously expand ImmunoBank to enable customized multiplexed TCR-T therapy for a wide range of solid tumor patients. For each patient with a solid tumor malignancy, we plan to analyze their tumor to determine which targets are expressed at high levels in each patient's particular cancer. We will then access 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 multiplexed TCR-T therapy.

Strategic Partnerships and Collaborations. T cells play a fundamental role in many other therapeutic areas beyond cancer, such asautoimmune disorders and infectious disease. 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.

Our Strategy

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

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Leverage our proprietary platform technologies to build our diverse 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. In order 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 candidates with therapeutic potential. As we continue to expand our screening technology, we believe we will be able to generate our ImmunoBank of therapeutic TCRs with the diversity required to treat many solid tumors using multiplexed therapy. We plan to populate the ImmunoBank with TCRs for multiple targets as well as multiple HLA types for each target, thus helping us to overcome the key solid tumor resistance mechanisms of target loss as well as HLA loss.

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Advance our lead liquid tumor 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. Using our ReceptorScan technology, we generated hundreds of highly active TCRs that recognize HA-1 and HA-2. We selected TSC-100 and TSC-101 based on their superior potency and lack of off-target effects. In the fourth quarter of 2021 we submitted INDs for each of TSC-100 and TSC-101 to the FDA. The FDA cleared the IND for TSC-100 in January 2022 enabling us to move forward with Phase 1 clinical development, while the IND for TSC-101 remains on clinical hold pending additional assessment of the potential for off-tumor reactivity in certain tissues. We plan to initiate the Phase 1 clinical study of TSC-100 in the first half of 2022. Pending clearance of the IND for TSC-101, we will then initiate the TSC-101 arm of the trial. 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 liquid tumor programs, we have established a foundation of manufacturing, clinical and regulatory capabilities to support the development of our broad portfolio of TCR-T therapies.

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Apply experience from our liquid tumor program to efficiently develop our solid tumor program targeting both novel and previously identified antigens.Using TargetScan, we have identified over 60 novel antigens based on tumor samples from patients who are actively responding to immunotherapy. We are initially developing our TSC-200 series of TCR-T therapies against five selected target antigens that are frequently expressed across multiple solid tumor types. Our first five solid tumor TCR-T therapy candidates include a combination of known targets, such as HPV16 for TSC-200, PRAME for TSC-203, and MAGE-A1 for TSC-204 as well as targets that are novel antigens for TCR-T therapy, such as for TSC-201 and TSC-202. We

believe that the treatment of solid tumors will require a combination of several TCR-T therapeutics, which we refer to as ‘multiplexed therapy.’ We plan to leverage the foundation built from our liquid tumor programs to efficiently develop a robust portfolio of TCR-T therapy candidates and expand ImmunoBank to enable multiplexed TCR-T therapies for solid tumors.

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Continue to develop manufacturing capabilities based on our non-viral T-Integrate system.We believe that in-house manufacturing capabilities substantially facilitate the successful early development of cell therapies. For our TCR-T therapy 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 expect will provide sufficient capacity to support all of our clinical programs in both liquid and solid tumors through Phase 2 clinical trials. With the FDA clearance of our IND for TSC-100, we believe our approach has been validated.

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Develop next generation T cell engineering capabilities. Our long-term vision is to build an allogeneic repository of off-the-shelf,genetically engineered T cells and provide multiplexed TCR-T therapies 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 allogeneic therapies based on T cells derived from healthy donors or induced pluripotent stem cells. We are also exploring additional next generation technologies, such as in vivo T-cell engineering, to further advance our T-cell engineering capabilities.

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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 disease. 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 collaboration and license agreement with Novartis to identify novel cancer antigens from the T cells of patients with a specific type of cancer. Novartis has the option to license and develop therapies for up to three discovered targets. Should Novartis license a target, we are eligible for a payment of $10 million per target as well as future milestones and royalties. Additionally, we have established a partnership for the development of a T cell-based COVID-19 diagnostic with QIAGEN Sciences, LLC.

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 hematologic 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 disease. 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 T cell receptors, or 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 Major Histocompatibility Complexes, or 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.

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 Human Leukocyte Antigen, or HLA, type. Although there are many different HLA types, some are quite common. For example, 42% of individuals in the United States 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-T therapy harnesses 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 tumor-infiltrating lymphocytes, or 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 hematological 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 chimeric antigen receptor, or 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 hematologic 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 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.

Reprogramming T cells with proven, highly effective TCRs comprehensively treats all cancer patients

The development of TCR-T therapy 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.

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 are building ImmunoBank with the goal of delivering customized multiplexed TCR-T therapy to a wide range of patients with cancers.

Learning

When a patient responds to an immunotherapy drug such as an immune checkpoint inhibitor, their tumor shrinks because T cells in their tumor become activated and drive an anti-tumor cytotoxic response. The TCRs of their T cells recognize tumor-specific antigens on tumor cells and signal the T cell to kill the cancer cells. Our approach starts with isolating clinically active anti-cancer T cells from tumor samples of patients who are actively responding to immunotherapy agents. We then use our proprietary TargetScan technology to determine the precise targets being recognized by their TCRs. This provides us with a novel TCR/target pair that can be developed into a TCR-T therapy candidate. The advantage of our approach is that when we identify a new target, we know the target is immunologically relevant – the human immune system has already used that target to recognize and fight cancer. Furthermore, we have already identified a TCR that recognizes the target and, importantly, is associated with a meaningful clinical response in a patient. To de-risk clinical development of the TCR, we use our SafetyScan technology to scan across every peptide sequence in the entire human proteome with the goal of ensuring that it does not have any problematic off-target effects. We then select TCRs that are highly active with no apparent problematic off-target effects to be added to ImmunoBank.

In addition to discovering novel TCR/target pairs, we are leveraging our proprietary ReceptorScan technology to identify highly active TCRs against previously identified and clinically validated targets. Once we identify these highly active TCRs, we use our SafetyScan technology to reduce the risk that they exhibit problematic off-target effects, which de-risks their subsequent clinical development. The diagram below illustrates our proprietary discovery process where therapeutic TCR candidates are discovered using either TargetScan or ReceptorScan and those that we characterize as the best TCRs after screening with SafetyScan are added to ImmunoBank.

Our Proprietary Target and TCR Discovery Process

Treating

Our discovery process enables us to build and expand 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 therapies 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 ImmunoBank. We believe the continued expansion and diversification of ImmunoBank will enable us to deliver customized multiplexed TCR-T therapy to 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.

Once the T cells are engineered with a combination of the most relevant TCRs, they will be transported back to the hospital 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. Our patient treatment and manufacturing process is summarized in the graphic below.

Our Patient Treatment and Manufacturing Process

Key Features of Our Approach

We believe there are three key advantages to our approach:

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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-targets of TCRs to eliminate candidates that could potentially pose a safety risk; (v) multiplex treatments through inclusion of clinically relevant targets with HLA type to customize treatments and (vi) manufacture TCR-T therapies efficiently and consistently without the use of viral vectors using T-Integrate. The central elements of our platform that differentiate us from other cell therapy companies are our proprietary platform technologies: TargetScan, ReceptorScan, SafetyScan, ImmunoBank and T-Integrate.

TargetScan—Identification of Novel Targets of Clinically Active TCRs

At the core of our proprietary platform is our TargetScan technology that enables us to identify the natural target of a TCR using an unbiased, 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.

To identify the target of a clinically active TCR found in the T cells of a patient actively responding to immunotherapy, we mix T cells expressing that TCR with a genome-wide library of target cells where every cell in the library expresses a different protein fragment. In each target cell, the protein fragment is processed naturally by the proteasome or immunoproteasome and the resulting peptides are displayed on cell-surface MHC proteins. If a T cell recognizes the peptide-MHC complex on a target cell, it attempts to kill the target cell, thereby activating a proprietary fluorescent reporter in the target cell. By isolating fluorescent target cells and sequencing their expression cassettes, TargetScan reveals the natural target(s) of the T cell, as shown below. This technology was published as a feature article in Cell in 2019.

Overview of Our Proprietary TargetScan Technology

Central to this technology is the library of protein fragments used for any given TargetScan screen. Our proprietary libraries comprise hundreds of thousands of specific sequences that collectively include most or all of the targets that a TCR could potentially recognize. For example, our current Oncology Target Discovery Library (version 3.0) comprises over one million clones, each expressing a unique protein fragment. Collectively, these fragments span every human protein encoded in the human genome, along with all single nucleotide polymorphisms, or SNPs, which are single amino acid variations in naturally occurring proteins, observed at over 1% frequency in the human population. In addition, the library includes elements that are specific to cancer cells, which are particularly interesting to us as potential targets: common oncogenic driver mutations, cancer/testis antigens, human endogenous retroviruses, or HERVs, and a large collection of sequences that are not translated in normal tissue but frequently translated in human cancers. We constructed our libraries using a tiling pattern of overlapping fragments to provide complete and redundant coverage of every targeted sequence, as shown in the graphic below.

Oncology Target Discovery Library (Version 3.0)

Our Oncology Target Discovery Library allows us to precisely identify the novel targets recognized by TCRs from patients who are actively responding to immunotherapy. In addition, because the library comprehensively covers every non-mutated human protein sequence, we are also able to fully characterize all potential off-target interactions for any given TCR, which we believe will help us reduce the risk and enhance the potential safety profile of our TCR-T therapy candidates before we advance them to clinical development. Furthermore, we can use our screen for any HLA type, enabling target discovery across a wide range of patient demographics.

To validate our TargetScan technology, we performed the following proof-of-concept screens using our Oncology Target Discovery Library (version 2.0), which includes approximately 600,000 protein fragments spanning every human protein. In the first screen, we used a naturally occurring TCR that is known to recognize the protein MAGE-A3. As shown below, our screen correctly identified the primary target of this TCR, and also identified three off-targets, including two that are unrelated at the gene level to MAGE-A3 and would likely not have been identified in a bioinformatic search.

TargetScan Proof-of-Concept:

Target Screen of MAGE-A3 Specific TCR Identifies MAGE-A3 and Three Off-Target

SafetyScan—Elimination of Off-Target Activity

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

The ability to identify problematic off-targets is critical as TCR-T therapies engineered with TCRs that recognize off-targets expressed at high levels in critical organs could cause toxicities, thereby limiting their therapeutic potential. To further validate this application of our technology, we used SafetyScan to screen an affinity-enhanced version of the MAGE-A3 TCR described above. Affinity enhancement is a process by which a naturally occurring TCR is mutated in order to generate a more potent therapeutic construct. The affinity-enhanced TCR that we screened had previously entered clinical trials with a different sponsor, but human testing of the TCR was halted abruptly because two patients treated with T cells engineered to express this affinity-enhanced TCR died of acute cardiac failure within five days of T cell administration. Subsequent studies revealed that this TCR recognized an off-target derived from the muscle protein Titin, which is abundantly expressed in cardiac tissue. When we screened this same affinity-enhanced TCR using our SafetyScan technology, we identified a variety of potential additional off-targets which were not seen in our screen of the natural TCR, including the protein Titin, as shown below. This experiment demonstrates why we believe that our SafetyScan technology provides a significant competitive advantage, because it enables us to rapidly and efficiently eliminate from our preclinical pipeline TCRs that are identified as recognizing potentially problematic off-targets. Importantly, this includes off-targets that may not be identified through standard bioinformatics or in-vitro tissue assays. We believe that SafetyScan thereby has the potential to enable us to decrease the risk of encountering unexpected toxicities in our clinical trials by providing a genome-wide understanding of off-target effects.

SafetyScan Proof-of-Concept: Target Screen of Affinity-Enhanced MAGE-A3-Specific TCR Identifies Clinically Relevant Off-target Linked to Toxicity

Using TargetScan, we have identified more than 60 shared antigens in patient tumors, and over 90% of these targets have not previously been identified as targets for TCR-T therapy. 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 also we have already identified highly active TCRs that recognize these targets.

ReceptorScan identifies ultrahigh affinity, naturally occurring TCRs with low risk of off-target effects

T-Integrate—Genetic Engineering of T Cells Using Transposons

Cell therapy manufacturing is highly complex, and associated challenges have led to significant delays or failures in the development of many cell therapies. To enable the rapid, cost-effective, and consistent manufacturing of TCRs, we have developed a non-viral vector delivery system that we refer to as T-Integrate. Our manufacturing platform enables us to introduce any of the TCRs from ImmunoBank, along with additional genetic elements such as CD8 that further augment T cell function, into the genomes of patient- or donor-derived T cells.

Genetically engineering a T cell requires two steps: (1) delivering DNA encoding the TCR into the nucleus of a T cell and (2) integrating that DNA into the genome of the T cell. These two steps are often accomplished through the use of retroviral vectors, such as lentivirus, by packaging RNA encoding the TCR into lentiviral particles, which are then used to infect T cells. Although effective, manufacturing lentiviral particles is time-consuming, costly, and often highly variable. In addition, each new TCR requires extensive process development, as the TCR sequence affects the efficiency with which it is packaged into the lentivirus.

As a more efficient and reproducible alternative to lentivirus, we have developed T-Integrate to genetically engineer T cells using a transposon/transposase system, as shown in the graphic below. In this system, DNA encoding the TCR is manufactured as a NanoplasmidTM and enables DNA delivery using a smaller plasmid footprint. 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 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 mRNA, which is constant for all TCR products. Unlike lentivirus, both of these components are routinely manufactured in a cost-effective manner without the need for extensive process development. We believe our manufacturing platform will enable us to efficiently develop and manufacture many different TCR-T therapies, allowing us to deliver customized multiplexed therapy to patients with cancer.

Our T-Integrate Manufacturing Platform

Our transposon vector includes both the beta and alpha chains of the TCR under the control of a strong promoter. This is designed to ensure that high levels of the TCR are produced on the surface of the T cells and that the TCRs that are normally expressed in the patient or donor’s T cells, or the ‘endogenous’ TCRs, are suppressed. We have also introduced specific alterations in the constant region of the TCR to further augment its stability. In addition to the TCR, our transposon construct includes genes encoding the alpha and beta chains of the cell-surface protein CD8. CD8 forms a complex with the TCR and is necessary for the TCR to recognize its target on tumor cells. Including the CD8 co-receptor in our construct enables us to genetically reprogram both major types of T cells: cytotoxic T cells that naturally make their own CD8 and helper T cells that do not make CD8. Our final TCR-T therapies are a mixture of both cytotoxic and helper T cells that have been reprogrammed to recognize and eliminate tumor cells expressing the relevant targets. We also included a short peptide tag at the beginning of CD8 alpha in our construct. This tag does not interfere with the function of CD8 alpha but provides a way to easily purify the engineered T cells during our manufacturing process. We plan to further enhance our T cell therapies with the addition of a TGFβ blocker to overcome the immunosuppressive tumor microenvironment. An illustration of the construct of our TCR-T therapies is shown below.

Construct of our TCR-T Therapies

Another important advantage of T-Integrate, our manufacturing platform, is that its greater carrying capacity than the commonly used lentiviral approach enables us to introduce additional genes that augment T cell function along with the gene that encodes the TCR itself. As our programs advance, we intend to introduce additional elements to our products with the goal of further improving their performance in the solid tumor setting, including features designed to increase the penetration of our T cells into solid tumors, with the aim of keeping our T cells active for a longer time and rendering our T cells more impervious to the hostile tumor microenvironment.

Our Programs

With our differentiated platform as our foundation, we are building a three-pillar research and development strategy to create transformational TCR-T therapies for patients, as shown below.

Our Liquid Tumor Program

We are developing our liquid tumor program to treat patients with hematologic malignancies 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 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 in order to prevent relapse in patients undergoing HCT.

Minor histocompatibility antigens like HA-1 and HA-2 are distinct from other cancer-associated antigens such as WT1 previously targeted by TCR-T therapies in hematologic 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 relatively spared. WT1-targeted TCR-T therapies proved to have relatively poor efficacy in patients with AML, potentially due to the rapid emergence of resistant tumor cells that had lacked WT1 expression and thus escaped killing by engineered T cells. HA-1 and HA-2 in contrast have high and homogenous expression (see below) making it less likely for tumors cells to escape due to low antigen expression. While HA-1 and HA-2 are also expressed in normal blood cells, treating HA-1/ HA-2 positive patients who receive stem cell transplantation from donors who are negative for HA-1/ HA-2, ensures that the engineered T cells selectively eliminate all the patient’s blood cells, cancerous 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 plan to conduct clinical trials of our lead TCR-T therapy 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, will be eligible for enrollment. Furthermore, eligible patients will require donors who are negative for either the target antigen or the HLA-A*02:01 allele.

Our Clinical Development Strategy for Multiple TCR-T Therapies

Background on Hematologic Malignancies

Hematopoietic stem cell transplantation, or HCT, has become the standard of care for many hematologic 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 acute myeloid leukemia, or AML, who receive HCT have a five-year post-transplant survival rate of 44%.

Approximately 7,000 allogeneic HCT procedures are performed yearly in the United States, primarily in patients with AML, MDS, or ALL. As a curative therapy for many hematologic malignancies, use of HCT has been steadily increasing over the last two decades, as shown below, 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 of CD19-targeted CAR-T therapies. CD19 is a target highly expressed on the surface of tumor cells and is also expressed on 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 hematologic malignancies such as myeloid leukemias and HCT remains the standard of care for those patients.

The Number of Allogeneic HCT Procedures in the U.S. Continues to Rise

However, despite the increasing use of HCT and the resulting clinical benefits or cures, approximately 40% of the patients who receive HCT relapse, 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 minor histocompatibility antigens, or 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, 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 liquid tumor 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 TCR-T therapy candidate directed at eliminating all native blood cells, including residual cancer cells, in HA-1-positive and HLA-A*02:01-positive patients with hematologic malignancies who undergo HCT using a donor who is either HA-1-negative or HLA-A*02:01-negative. Using ReceptorScan, we screened over a hundred million CD8+ T cells and identified and assessed hundreds of highly active TCRs that recognize the HA-1 antigen. We selected TCR-100a based on its superior affinity, cytotoxic activity, and specificity compared to the others. 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 TCR-100a will generate an anti-tumor effect in patients, leading to a reduction in relapse rates and an increase in long-term survival. In the fourth quarter of 2021, we filed an IND for TSC-100 with the FDA. The FDA cleared our IND for TSC-100, enabling us to move forward with Phase 1 clinical development.

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 United States have the HLA type A*02:01, which means that approximately 25% of individuals in the United States 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. A summary of the treatment paradigm for TSC-100 is illustrated below.

TSC-100 Treatment Paradigm

Preclinical Data

Using ReceptorScan, we screened over 175 million T cells from six healthy donors to identify naturally occurring TCRs specific for HA-1. We then extensively characterized over 300 of these TCRs for their ability to specifically recognize and kill tumor cells that express HA-1. We prioritized TCRs with the highest potency in cytotoxicity assays and in their production of cytokines associated with increased T-cell activation and function. Through this screening process, we identified TCR-100a, which exhibited superior potency compared to the other TCRs. We assessed the in vitro HA-1-specific cytotoxicity of TCR-100a using cell lines with various levels of HA-1 expression, as shown below. THP1, a cell line that expresses moderate levels of HA-1, was susceptible to cell killing by multiple TCRs we tested. However, TF1, a cell line that expresses less than half the level of HA-1 expressed by THP1, was sensitive to cell killing by TCR-100a but was resistant to almost all other HA-1-specific TCRs, including TCRs reported in the literature. Our preclinical studies also demonstrated that SUDHL1 cells, which lack HA-1 expression, were resistant to all tested HA-1-specific TCRs, as expected, highlighting the high selectivity and potential safety of TCR-T therapies.

In Vitro Studies Demonstrate Superior HA-1-Specific Cytotoxicity

of TCR-100a Compared to Other TCRs

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 is able to 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. As shown below, TSC-100 eliminates both homozygous and heterozygous HA-1-positive healthy blood cells and leukemia cells.

TSC-100 Displays Specific Cytotoxic Activity Towards HA-1-positive Cells

It is known in the cell therapy field that TCRs which exhibit off-target effects can potentially cause toxicity. In order to reduce the potential for TCR-100a to exhibit problematic off-target effects, we used SafetyScan to comprehensively scan for any other potential targets recognized by TCR-100a. This screen was performed using a subset of our Oncology Target Discovery Library (version 2.0), which includes approximately 600,000 protein fragments and collectively spans every protein encoded in the human proteome as well as all common SNPs. As shown below, all three protein fragments in the library that contain the HA-1-positive peptide antigen were strongly enriched in the screen, and no significant off-target interactions were observed. In contrast, some of the other HA-1-specific TCRs identified by ReceptorScan did exhibit off-target effects, highlighting our ability to select candidates that we believe have favorable risk/benefit profiles.

SafetyScan Screen Reveals No Significant Off-Targets for TCR-100a

To further evaluate the potential safety profile of TSC-100, we screened TCR-100a against HA-1-positive and HA-1-negative cells that individually express each of the 108 most common HLA alleles. In the HA-1-positive cells, TCR-100a was able to mediate efficient recognition in cells expressing HLA-A*02:01 as well as in cells expressing two related HLA types, HLA-A*02:02 and HLA-A*02:06. This suggests that patients with any of these three HLA types could potentially benefit from TSC-100. Notably, TCR-100a showed no recognition of HA-1-negative cells across all 108 HLA types, indicating low risk of alloreactivity or misrecognizing other antigens on other HLA types, as shown below.

TSC-100 Shows No Detectable Alloreactivity Across 108 Different HLA Types

TSC-101

Similar to TSC-100, TSC-101 is an allogeneic TCR-T therapy candidate directed at eliminating residual cancer cells in HA-2-positive and HLA-A*02:01-positive patients with hematologic 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. Using ReceptorScan, we have identified a highly active TCR, which we refer to as TCR-101a, that recognizes HA-2. In the fourth quarter of 2021, we filed an IND for TSC-101. The FDA placed a clinical hold on the TSC-101 IND; we received written communication from the FDA asking for additional assessment of the potential for off-tumor reactivity in certain tissues and are working with the agency to resolve its questions as quickly as possible.

Unlike HA-1, the HA-2 antigen is highly prevalent, with approximately 95% of individuals in the United States 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 United States, 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 patients typically have between two and three potential haploidentical donors.

Preclinical Data

Similar to TCR 100a, we used ReceptorScan to identify TCR 101a. We screened approximately 237 million CD8+ cells from five healthy HA-2 negative donors and identified approximately 1,302 natural TCRs that recognize HA-2. These were then narrowed down to 15 TCRs with the highest surface expression and greatest affinity for the HA-2 peptide. We further evaluated the top five TCRs for off-target cross-reactivity against the entire human proteome using SafetyScan, identifying TCR-101 as the most active TCR with the lowest off-target activity and cleanest cross-reactivity profile against 108 other HLA alleles. Finally, TSC-101, our TCR-T therapy candidate which is T cells manufactured to express TCR-101, was tested on a panel of normal cell types representing all vital organs and did not recognize any normal non-hematologic cell type. In contrast, TSC-101 demonstrated efficient cell killing of both normal and malignant primary hematologic samples confirming a high degree of selectivity for hematologic cells. The discovery of TCR-101 was presented at the 63rd American Society of Hematology Annual Meeting and Exposition, in December 2021.

TCR-101a Demonstrates High Activity Similar to TSC100a

Clinical Development Plan for Our Liquid Tumor 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 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 better tolerated, but are associated with higher relapse rates. TSC-100 and TSC-101 are both designed to substantially reduce relapse rates, and we plan to enroll patients who are eligible for RIC-based HCT with the goal of improving clinical outcomes for these patients.

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 the majority of 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, parent 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 United States and worldwide.

The use of haplos 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 TSC-100 and TSC-101 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 believe TSC-100 and TSC-101 should have minimal toxic side effects.

Planned Phase 1 Clinical Trial

We are planning to conduct clinical studies for TSC-100 and TSC-101 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 ALL, AML, and MDS, that are undergoing HCT following RIC.

Our Phase 1 clinical trial is designed to include measurements of early surrogate markers of efficacy, such as chimerism, or the percentage of blood cells that are donor-derived, and whether patients continue to have detectable residual leukemia in their post-transplant bone marrow biopsy, both of which are predictors of relapse. As shown in the graphic below, we also plan to include 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 Phase 2 trial towards a future biologics license application, or BLA, filing.

Planned Multi-Arm Phase 1 Clinical Trial Design

Anticipated timeline

We filed INDs on TSC-100 and TSC-101 in the fourth quarter of 2021. The FDA has cleared our IND for TSC-100, enabling us to move forward with our clinical development plan for TSC-100. We anticipate dosing the first patient in the TSC-100 arm of our Phase 1 clinical trial in the first half of 2022; and presenting initial clinical data on our Phase 1 trial in the second half of 2022. The FDA placed a clinical hold on our IND for TSC-101. We received written communication from the FDA asking for additional assessment of the potential for off-tumor reactivity in certain tissues and are working with the agency to resolve its questions as quickly as possible. The liquid tumor trial is based on an umbrella protocol, which will allow us to begin the TSC-100 and control arms of the trial in the near term and to open the TSC-101 arm to the ongoing trial upon clearance of the TSC-101 IND.

Future market expansion opportunities

If TSC-100 and TSC-101 demonstrate the ability to significantly reduce relapse rates after hematopoietic cell transplantation, 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 7,000 patients undergo HCT per year in the United States out of approximately 40,000 patients diagnosed each year with AML, MDS and ALL. There are two reasons for this relatively modest rate of transplant utilization. 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 safely use HCT. If HCT combined with TSC products markedly reduce relapse rates, patients who do not achieve CR could still undergo HCT and benefit from its curative potential. This market expansion would require a separate clinical trial. Second, while reduced intensity conditioning 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 to eliminate residual leukemia cells and reducing doses further would result in greater relapse rates. If however, the relapse rates could be reduced by a TSC product post HCT, 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 therapy to older, frailer patients. A final market expansion opportunity could occur from the use of TSC products as a chemotherapy andradiation 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.

Solid Tumor Program

We are developing a portfolio of autologous TCR-T therapy candidates that are designed to be used in combination with each other to treat and eliminate solid tumors. Our TSC-200 series of 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 candidates include: (i) either well-recognized cancer targets that have demonstrated anti-tumor activity in clinical trials or 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 five solid tumor TCR-T therapy candidates include a combination of known targets, such as HPV16 for TSC-200, PRAME for TSC-203, and MAGE-A1 for TSC-204, as well as novel TCR-T therapy targets that have not yet been tested in the clinic, such as TSC-201 and TSC-202. We are currently advancing our five solid tumor TCR-T therapy candidates through lead optimization, and we expect to submit IND applications for two candidates in the second half of 2022, with additional IND submissions expected to be filed in 2023. In addition to our five lead solid tumor TCR-T therapy candidates, we have identified over 60 novel antigens based on tumor samples from patients who are actively responding to immunotherapy using our TargetScan technology. We are in early stages of analyzing these additional novel antigens and plan to advance those that we believe have the best potential as a TCR-T therapy candidate into preclinical development.

We are building ImmunoBank, a collection of highly active TCRs, to enable multiplexed TCR-T therapy. Our vision is to expand ImmunoBank with TCRs that recognize diverse targets and are associated with multiple HLA types in order to provide a broad array of therapeutic options for patients with various types of solid tumors. For patients with a solid tumor malignancy, we plan to analyze their tumor to determine which targets are expressed at high levels in their particular cancer. We will then access 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 engineered T cells will be infused back into the patient as a multiplexed TCR-T therapy.

Our Strategy to Treat Solid Tumors with Multiplexed TCR-T Therapy

TCR-T Therapy 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 well in excess of $20 billion.

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 based on the premise that if we can understand how T cells naturally fight cancer, we can use this information to design life-changing TCR-T therapies for virtually any patient with cancer. Our discovery process begins with identifying patient T cells that are actively driving their clinical response to immunotherapy. We then use TargetScan to determine the precise targets of these highly active TCRs. Our discovery efforts are initially focused on patients with head and neck cancer who respond to checkpoint inhibitor therapy and patients with melanoma who respond to TIL therapy. These cancers represent tumor types with a high degree of T cell infiltration and strong responses to immunotherapy, which provides us with clinically active T cells from which we can discover novel TCR/target pairs. We have found that targets discovered in one type of cancer are often expressed in other cancers as well, enabling broader clinical development of our TCR-T therapy candidates. The tumor types we are focused on also express several known targets that were previously discovered from patient T cells. We are using ReceptorScan to discover highly active TCRs for these previously identified targets to complement the discovery of our novel TCR/target pairs. Finally, ImmunoBank will allow us to target multiple HLA types to prevent target loss and increase durability of response.

Novel Targets Identified from Patients with Head and Neck Cancer

One of the ways we identify anti-cancer TCRs is by focusing on T cells that clonally expand in a tumor when the patient responds to checkpoint inhibitor therapy. Some of this work is being performed under collaborative research agreements with various academic institutions. Using single cell sequencing, our collaborators determined the TCR sequences of thousands of T cells in the tumors of patients with head and neck cancer before and after immunotherapy. This analysis also revealed the frequency of each T cell clone in the tumor samples. As an example, if a particular TCR sequence is observed at 0.05% frequency in the tumor before the patient receives immunotherapy and then increases to 5% after the tumor starts to shrink, the T cell has clonally expanded 100-fold and is likely to have played a causal role in driving the patient’s clinical response. Certain TCR sequences are not detectable in the pre-treatment biopsy but are observed at high frequency in the post-treatment tumor. These emerging clones are also potential candidates for driving the patient’s clinical response. An illustrative example of T cell sequencing data from one patient with head and neck cancer who had a complete response to immunotherapy.

Clinically Relevant Anti-Cancer T Cells Identified Through T Cell Sequencing

We have performed genome-wide TargetScan screens on over 100 TCRs derived from T cells that clonally expanded in the tumors of patients with head and neck cancer who are responding to immune checkpoint inhibitors, which has resulted in our discovery of over 60 novel shared antigens. An example of one such screen is shown below. This screen was performed with our Oncology Target Discovery Library (version 2.0), which comprises over 600,000 protein fragments. Two protein fragments, shown in dark pink, were specifically recognized by the TCR. Due to the redundancy built into our library through its overlapping tiling pattern, both of the identified clones contain the same nine amino acid-long peptide antigen that we determined to be the target of this TCR. Notably, no off-targets were observed in the screen, highlighting the value of the SafetyScan technology in identifying TCRs with clean specificity profiles.

Identification of a Novel Target from a Patient with Head and Neck Cancer

Novel Targets Identified from Patients with Melanoma

Another approach we use to identify clinically relevant anti-cancer T cells is to analyze T cells from patients with melanoma who respond to TIL therapy. Using single cell sequencing, we determine the TCR sequences of the T cells in the responding patient’s TIL therapy product and focus on the most abundant T cell clones. We have found that TIL therapy products are often dominated by as few as two or three clones, further increasing our confidence that these TCRs played a causal role in fighting the patient’s cancer.

To increase the throughput of our discovery efforts, we have used TargetScan in a more directed manner to screen sub-libraries of protein fragments that focus on particular classes of tumor antigens. For example, we built a sub-library that focuses on cancer/testis antigens, or CTAs, which are genes that typically play a role in embryonic development but are not expressed in any adult tissues other than testes. T cells do not infiltrate testes and cells in the testes have very low levels of MHC proteins, making testes an immune-privileged site that will not be targeted by engineered T cells in the context of cell therapy. CTA genes are frequently found to be expressed in tumor cells and often play a role in causing cancer. Several well-recognized targets in development for TCR-T therapy are CTAs, including NY-ESO-1 and MAGE-A4.

We are focused on the discovery of novel targets within this class of antigens and have built a TargetScan library comprising 40,000 fragments that cover 1,600 CTA genes. Because this library is substantially less complex than our genome-wide Oncology Target Discovery Library, we can screen the TargetScan library with dozens of TCRs simultaneously. For example, the screen shown below was conducted with 35 TCRs derived from 11 patients with melanoma who received TIL therapy. In a single screen, we identified three TCR/target pairs that recognize CTAs, including the antigen target for one of our lead solid tumor product candidates, TSC-201, which we refer to as Target-201, as well as two other antigens that have not previously been identified as targets for TCR-T therapy.

Three Novel Cancer/Testis Antigen Targets Identified

from TIL-Responsive Patients

TCR and Target Validation Process

When we discover novel TCR/target pairs, we first determine if the gene that encodes the target is expressed at high levels in normal tissue. As shown below, Target-201 is exclusively expressed in testis, which is an immune privileged tissue and, as a result, should not pose a significant safety concern. We also examine how frequently the target is expressed in various solid tumors. As shown below in dark pink, Target-201 is overexpressed in a high percentage of melanoma tumor samples as well as in several other tumor types, including non-small cell lung cancer, or NSCLC, head and neck cancer, and cervical cancer.

Selective Expression of Target-201 in Multiple Tumor Types vs. Normal Tissues

Next, as part of our discovery process, we test if the TCRs discovered with our approach are able to kill cancer cells that naturally express the relevant target and specific HLA type. As shown below on the left, when T cells expressing the TCR that recognizes Target-201 are cultured with melanoma cell lines that naturally express different levels of Target-201, such as A101D and SKMEL5, the degree to which the T cells get activated correlates with the expression level of Target-201 in the melanoma cells. In addition, the T cells kill melanoma cells expressing high levels of Target-201, as shown below on the right but do not kill cells that express low levels of Target-201, which highlights the selectivity of the TCR for Target-201.

Finally, to reduce the risk that a TCR discovered in a targeted screen recognizes any problematic off-targets, we re-screen the TCR using SafetyScan and our genome-wide library. As shown below, when the TCR that recognizes Target-201 was re-screened using our Oncology Target Discovery Library (version 2.0), which includes protein fragments spanning every normal protein encoded in the human genome, only one potential off-target was observed. We subsequently identified several cell lines that naturally express the full-length protein from which the off-target antigen was derived and found that T cells engineered with the TCR do not recognize or kill these cells. Although the TCR recognizes target cells overexpressing protein fragments containing this off-target antigen, it does not recognize cells expressing the full-length protein at normal levels. This shows that our genome-wide screen detects potential off-targets with very high sensitivity, and that not all off-targets detected in this manner are problematic. In the event, however, that a TCR exhibits

problematic off-target effects, we can use ReceptorScan to discover alternative TCRs that have similar anti-cancer effects but do not cross-react with proteins expressed at high levels on normal tissue or critical organs.

Genome-Wide Safety Screen of Target-201 TCR Using SafetyScan

To further expand the pool of addressable patients with our TSC-200 series of product candidates, we can also use ReceptorScan to identify TCRs recognizing antigens on the same target protein that are presented by different HLA alleles. Ultimately, we believe this strategy has the potential to enable multiplexed TCR-T therapy in which a patient is treated with more than one TCR for the same target protein, presented on two different HLA alleles. This approach could reduce the risk of resistance arising from loss, downregulation, or mutation of individual HLA genes.

TSC-200 Series

Our first five solid tumor TCR-T therapy candidates include a combination of known targets, such as HPV16 for TSC-200, PRAME for TSC-203, and MAGE-A1 for TSC-204, as well as targets that are novel antigens for TCR-T therapy, such as for TSC-201 and TSC-202. All of these targets are frequently expressed in the solid tumors of interest to us, including melanoma, head and neck cancer, NSCLC, and cervical cancer. In 2021, it is estimated that in the U.S., approximately 100,000 patients are diagnosed with melanoma, 66,000 with head and neck cancer, 185,000 with NSCLC, and 15,000 with cervical cancer. We plan to advance a combination of known and novel targets into clinical development, which will allow us to use the product candidates targeting known antigens as backbones for our initial clinical trials evaluating multiplexed TCR-T therapy. For example, we plan to evaluate TSC-200, which targets well-known and clinically-validated oncogenic proteins derived from HPV16, in combination with TSC-201 and TSC-202, which target antigens that have not yet been tested for TCR-T therapy.

TSC-200

In parallel with our TargetScan discovery efforts in head and neck cancer, we are using ReceptorScan to discover highly active TCRs that target antigens in human papilloma virus, or HPV, for our TSC-200 program. 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 due to the fact that 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 and anal cancers as well as over 60% of vaginal, vulval, and penile cancers. Recent 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 candidate targeting HPV16, which we believe provides clinical support for the inclusion of an HPV16-targeting TCR, TSC-200, in our multiplexed TCR-T therapy strategy. We have identified over a thousand TCRs that recognize HLA-A*02:01- specific antigens derived from HPV16, and we are currently identifying the most active TCR with a de-risked safety profile to advance to IND-enabling studies. We also intend to extend our discovery efforts to include additional HPV16-derived antigens presented on other HLA types as the program advances.

TSC-201

As detailed above, using our TargetScan technology, we have identified what we refer to as Target-201, as one of three targets from the T cells of melanoma patients responding to TIL therapy. Target-201 is a 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 Target-201 should not pose a significant safety concern. In addition, Target-201, 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 50% of melanomas, approximately 25% of head and neck cancers, and approximately 50% of non-small cell lung cancers. Tumors expressing Target-201 have been shown to be associated with metastasis and poor patient survival. We have identified two clinically active TCRs that recognize novel epitopes derived from Target-201 presented on two common HLA alleles, and we are currently evaluating which TCR/Target-201 antigen pair to advance to IND-enabling studies. We are also using ReceptorScan to identify additional TCRs for Target-201 epitopes presented on other HLA alleles to further expand the addressable patient population.

TSC-202

We have also identified clinically active TCRs targeting what we refer to as Target-202, which is a protein involved in cell invasion and migration that plays a role in the metastasis of tumors. Target-202 is a CTA that is expressed only in the placenta, with very low expression in testis and no expression in any other adult tissue. Increased expression of Target-202 is positively correlated with the degree of tumor invasion, lymph node metastasis, distant metastasis, and poor prognosis. Expression of Target-202 is especially high in HPV-positive tumors. Target-202 expression is repressed in normal tissue by the tumor suppressor protein p53. In HPV-driven carcinomas, however, the viral protein E6 causes degradation of p53, leading to increased expression of Target-202. As a result, high expression of Target-202 is observed in over 90% of cervical cancers and approximately 75% head and neck cancers. Target-202 is also expressed in HPV-negative tumors, including approximately 40% of NSCLCs, over 95% of melanomas, and up to 80% of primary breast cancers. Using ReceptorScan, we have identified thousands of TCRs that recognize multiple HLAA*02:01-specific epitopes derived from Target-202, and we are currently identifying the most active TCR to advance to IND-enabling studies.

TSC-203

We are developing TSC-203 as a TCR-T therapy candidate targeting a known cancer antigen, Preferentially Expressed Antigen in Melanoma, or PRAME. Similar to Target-201, 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 Target-201 and Target-202, is absent in adult tissues except in the ovaries and testis. Approximately 50% of NSCLCs, approximately 25% of cervical cancers, and approximately 90% of melanomas and head and neck cancers express PRAME. Moreover, PRAME expression is homogeneous within these tumors, which we believe make it an attractive target for multiplexed TCR-T therapy. Using ReceptorScan, we have identified thousands of TCRs across multiple PRAME-derived epitopes presented on HLA-A*02:01, and we are currently identifying the most active TCR to advance to IND-enabling studies. In addition, we are using TargetScan on clinically active TCRs from patients with melanoma and head & neck cancer to identify novel PRAME epitopes presented on other HLA types.

In addition to our five lead solid tumor TCR-T therapy candidates, we have identified more than 60 novel antigens using TargetScan, of which over 90% have not previously been publicly disclosed as targets for TCR-T therapy. Although target validation naturally results in attrition, it is clear that tumor-resident T cells recognize many more shared antigens than have been reported to date. Many of the antigens we have identified are expressed across multiple solid tumor types and some have expression levels comparable or superior to targets currently in clinical development by others such as NY-ESO-1. We are currently in the process of validating several of these additional novel antigens and identifying potential TCR/target pairs using our platform technologies. We plan to continuously expand ImmunoBank with TCRs for both known and novel targets as well as address different HLA types to enable customized multiplexed TCR-T therapy while also addressing the potential issue of HLA loss leading to resistance for a wide range of solid tumor patients.

TSC-204

We are developing TSC-204 as a TCR-T therapy candidate targeting a known cancer antigen, melanoma-associated antigen 1, or MAGE-A1, that will include multiple TCRs for different HLA-restricted epitopes on this target. Using our TargetScan platform we have identified MAGE-A1 as one of the targets of T cells from a head and neck cancer patient responding to checkpoint inhibitor therapy. From this patient, we discovered multiple different TCRs recognizing a novel HLA-C*07:02 restricted epitope of MAGE-A1 which is a cancer/testis gene frequently overexpressed in a wide variety of solid tumors, including approximately 45% of head & neck cancers, 50% of melanomas, 50% of cervical cancers and 50% of non-small cell lung cancers. In addition to these highly active HLA-C*07:02 restricted TCRs, we are also using ReceptorScan to identify additional clinical TCRs for MAGE-A1 epitopes presented on multiple

other HLA alleles to further expand the addressable patient population. TScan believes that it is the only company with a disclosed TCR program in MAGE-A1 for HLA types other than A*02:01. The Company anticipates filing an IND for TSC-204 in the second half of 2022.

Clinical Development Plan for Our Solid Tumor Program

For the initial first-in-human studies for our TSC-200 series of TCR-T therapy candidates, we plan to evaluate multiple TCRs in parallel to determine the safety and preliminary efficacy of multiplexed TCR-T therapy. We envision using TSC-200 as the backbone therapy for patients with HPV-positive malignancies, including head and neck, cervical, and anal cancers. According to the Centers for Disease Control, the incidence of HPV-positive cancers in the U.S. is approximately 46,000 cases per year, with five-year survival rates ranging from approximately 50% to 70%. The targets of TSC-201, TSC-202, TSC-203, and TSC-204 are also frequently expressed in the solid tumors of interest to us, as shown below.

Cancer Expression Levels for the Targets of our Lead Solid Tumor Programs

After establishing single agent safety for each of our initial solid tumor TCR-T therapy candidates in a multi-arm Phase 1 clinical trial, we plan to test TSC-200 in combination with TSC-201, TSC-202, or TSC-203 in patients who are positive for the respective targets of these therapies. We will also explore three-TCR combinations in patients who are positive for the three respective targets. Because the targets of TSC-201, TSC-202, TSC-203, and TSC-204 are also frequently expressed in melanoma and NSCLC, we will also explore various combinations of these TCR-T therapy candidates in patients with HPV-negative head and neck cancer, melanoma, and NSCLC. A summary of our planned Phase 1 clinical strategy is shown below.

TSC-200 Series Phase 1 Clinical Strategy

Anticipated timeline

As we advance our solid tumor program, we anticipate presenting pre-clinical data at a major scientific meeting in the first half of 2022; filing INDs for two solid tumor TCR-T therapy candidates in the second half of 2022 with additional IND filings in 2023; and presenting initial clinical data on our multi-arm Phase 1 clinical trial in 2023. As we continue to discover and validate TCR/target pairs, we aim to continue to file additional INDs and introduce those solid tumor TCR-T therapy candidates into this multi-arm basket-style Phase 1 clinical trial. We believe this trial will serve as the first step towards our long-term goal of building and expanding ImmunoBank to provide customized multiplexed TCR-T therapy for virtually any patient with a solid tumor malignancy.

ImmunoBank – Flexible Content for Diverse Platforms

Our current clinical development strategy is based on autologous T cell engineering, which is the basis for approved CAR-T products such as Kymriah and Yescarta. As the field of T cell engineering evolves, a wide variety of additional manufacturing platforms are being developed that may further improve TCR-T cell 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 Sana Biotechnology, 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 our ImmunoBank of TCRs through clinical development, we intend to continue to build our own manufacturing platform, while simultaneously investigating novel T cell engineering platforms once they have established safety and efficacy. Ultimately, we aspire to build the largest collection of validated TCR “content” that can be used with a variety of T cell engineering platforms.

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 disease. 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.

COVID-19

As a proof-of-concept for TargetScan’s applicability and antigen discovery capabilities in infectious disease, we applied our technology to identify the antigens most frequently recognized by the T cells of patients who had recovered from COVID-19. We screened the entire genome of SARS-CoV-2, the virus that causes COVID-19, as well as the genomes of SARS-CoV and the four seasonal coronaviruses that cause the common cold. We found that the antigens recognized by CD8+ T cells were largely derived from segments of the virus that are not part of the spike protein, which is the current target of COVID-19 vaccines. Additionally, patient T cells were generally not found to be cross-reactive with seasonal coronaviruses, suggesting that prior coronavirus exposure is unlikely to confer immunity to COVID-19. We published the details of these studies in the journal Immunity in 2020.

T Cell Targets in SARS-CoV-2 Are Primarily Located

In Proteins Other Than the Spike Protein

We have partnered with QIAGEN Sciences, LLC to develop a highly specific diagnostic test to determine prior exposure to the virus based upon the presence of anti-viral T cells.

We believe that our findings can also be used to develop next-generation vaccines for COVID-19 that confer durable immune protection from SARS-CoV-2 infection and potentially provide protection against future variants. Most current vaccine efforts elicit a response to the SARS-CoV-2 spike protein. While these first-generation vaccines are able to elicit neutralizing antibodies and provide effective protection against infection, it is not clear how durable these responses will be given that antibody levels have been shown to rapidly decline after a few months and numerous coronavirus variants have now been discovered with mutations in the spike protein. Notably, none of the mutations observed in these variants occurs in the 29 T cell targets that we identified, suggesting that vaccines delivering these target antigens may be less susceptible to vaccine-resistant strains emerging in the future. We have partnered with Akagera Medicines to develop an mRNA lipid nanoparticle (LNP) vaccine candidate which includes not only the spike protein that elicits neutralizing antibodies but also all the non-spike T cell epitopes we discovered which would elicit a protective T cell response. The LNP vaccine candidate utilizes Akagera’s novel LNP technology which is designed to better target lymph nodes thereby reducing the risk of local toxicity such as injection site swelling, reduce the vaccine dose by up to 10-fold and have improved stability requiring a -20°C cold chain rather than the more onerous -80°C cold chain that existing mRNA LNP vaccines require. Preclinical testing of this vaccine candidate has demonstrated efficient eliciting of a broad T cell response mimicking the T cell responses observed in convalescent COVID-19 patients.

Other Diseases

TargetScan can also be used for novel target discovery in additional infectious and autoimmune diseases. 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 diseases 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.

License and Collaboration Agreements

Collaboration and License Agreement with Novartis

On March 27, 2020, we entered into a Collaboration and License Agreement with Novartis Institutes for BioMedical Research, Inc. (Novartis) (such agreement, the Novartis Agreement). Pursuant to the Novartis Agreement, we have received an aggregate of $20.0 million of cash representing the upfront payment and have receivables for reimbursement of expenditures under the arrangement of $0.9 million as of December 31, 2021. We granted Novartis and its affiliates options to obtain exclusive, royalty-bearing, sublicensable, transferable, worldwide licenses to certain target antigens identified in performance of the Novartis Agreement and corresponding T-cell receptors for such target antigens to make, have made, import, use, sell or offer for sale, including to develop, manufacture, commercialize, register, hold or keep, have used, export, transport, distribute, promote, market or have sold or otherwise dispose of such target antigens and corresponding T-cell receptors. Novartis can exercise each option by paying us $10.0 million and can exercise up to three options (each target antigen for which Novartis exercises an option, an “Optioned Program”). In addition, we granted Novartis and its affiliates an option to obtain a non-exclusive, royalty-bearing, sublicensable, transferable, worldwide license under our intellectual property corresponding to products associated with such Optioned Program and improvements to our platform created in performance of activities under the Novartis Agreement, in each case, solely as necessary to exploit products associated with such Optioned Program.

The ownership of inventions (and resulting patent rights) created in performance of the collaboration will be determined by inventorship (i.e., inventions invented solely by us in performance of the collaboration and inventions invented solely by Novartis in performance of the collaboration will be owned by Novartis and inventions invented jointly by us and Novartis in performance of the collaboration will be jointly owned). We retain our rights to (i) our intellectual property, (ii) programs that are not selected by Novartis and (iii) our platform improvements, which will not be considered collaboration technology.

Each party has the sole right (but not the obligation) in its sole discretion and cost, to prepare, file, prosecute and maintain all patents and patent applications that are owned solely by such party. For any collaboration patents or patent applications owned by us, if we elect not to file a patent application or to cease the prosecution or maintenance of any of our collaboration patents or patent applications, we must notify Novartis immediately of such decision, at which point Novartis will become permitted to file or continue prosecution or maintenance of such patent or patent application in our name. For joint collaboration patents and patent applications, Novartis has the first right (but not the obligation) to prepare, file, prosecute and maintain any joint collaboration patent or patent applications and/or optioned program patents or patent applications.

For each Optioned Program, as between the parties Novartis is solely responsible for the clinical development of such Option Program. Novartis is required to pay us up to an aggregate of $230.0 million upon achievement of certain clinical milestones and milestones for the first commercial sale in certain countries with respect to products directed to the corresponding target antigen for each Optioned Program. Novartis is also required to pay us up to an aggregate of $260.0 million upon achievement of certain annual net sales milestones for products directed to the corresponding target antigen for each Optioned Program. In addition, for each Optioned Program, Novartis is required to pay us, on a product-by-product and country-by-country basis, tiered royalties in the low-single-digit to mid-single-digit percentage on Novartis’, its affiliates’ and sublicensees’ net sales of certain products directed to target antigens for each Optioned Program and a percentage in the mid-single-digits to low-teens on Novartis’ net sales of products directed to such antigens and containing a T-cell receptor we identified to Novartis in our performance of the Novartis Agreement, subject to certain customary reductions. Royalties will be payable on a product-by-product and country-by-country basis during the period of time commencing on the first commercial sale of an applicable product in a country and ending upon the later of: (a) 10 years from the date of first commercial sale of such product in such country; (b) expiration of the last-to-expire valid claim of patents licensed by us to Novartis under the Novartis Agreement covering the manufacture, use or sale of such product in such country; or (c) the expiration of any regulatory or marketing exclusivity in such country with respect to such product (the “Royalty Term”). Novartis may terminate the Novartis Agreement entirely or on a program-by-program basis at any time for convenience upon 90 days’ notice; provided, however, that Novartis will be required to fulfill any payment obligations that accrued prior to termination.

For a period of up to 180 days after the end of the collaboration period (which collaboration period will end no later than March 2023), we agree to notify Novartis if we intend to seek a third party partner to exclusively license or similarly grant rights to patents or know-how developed by us under the collaboration to allow for the development or commercialization of products directed to any programs that Novartis has not exercised an option to prior to the expiration of such option (a ROFN Notice). Upon receiving such notice, Novartis will have 90 days to provide us with a term sheet to exclusively license such collaboration technology to develop or commercialize products directed to such previously declined program, which will trigger Novartis’s right of first negotiation. If Novartis delivers such term sheet, then Novartis will have 270 days following the ROFN Notice to negotiate a license for such collaboration technology.

The Novartis Agreement will remain in effect until (i) all options expire unexercised or (ii) if any options are exercise, on a product-by-product and country-by-country basis for each Optioned Program, upon the expiration of the Royalty Term for all products

associated with such Optioned Program in such country. Either party may terminate the Novartis Agreement upon an uncured material breach of the agreement or insolvency of the other party. We may terminate the Novartis Agreement immediately upon written notice to Novartis if Novartis challenges the validity, enforceability or scope of any of the patents we license to Novartis under the agreement. Novartis may terminate the agreement, either in its entirety or on a program-by-program basis, for convenience at any time with 90 days’ prior written notice.

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. (“BWH”), as amended on July 26, 2019 and further amended and restated on April 20, 2021 (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 amended 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 (“Collaborators”) where we practice under BWH’s patent rights in connection with the research or development one or more therapeutic products or processes with or for such third party (“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 sixty (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: (1) without notice if we fail to maintain insurance required by the BWH Agreement; (2) upon notice within 60 days of our bankruptcy; (3) 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; (4) 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 (5) 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.

Option and Exclusive License Agreement with Qiagen

On November 5, 2020, we entered into an Option and Exclusive License Agreement with QIAGEN Sciences, LLC (Qiagen) (such agreement, the Qiagen Agreement). Pursuant to the Qiagen Agreement, Qiagen paid us a one-time non-refundable, non-creditable $150,000 option fee (Option Fee) in exchange for an option to obtain an exclusive, royalty-bearing, sublicensable, worldwide license under our rights to patents and patent applications related to certain SARS- CoV-2 peptides to use, make and otherwise commercialize products containing such SARS-CoV-2 peptides (the Option). Qiagen exercised the Option on April 14, 2021 and paid us an additional $150,000 option exercise fee. Qiagen may freely sublicense its rights through multiple tiers so long as it binds each sublicensee to terms

consistent with the Qiagen Agreement and remains responsible for any breaches of such terms by its sublicensees. We expressly reserved the right to conduct research or develop or commercialize products for or related to the treatment of SARS-CoV-2.

In addition, Qiagen is required to pay us a one-time, non-refundable, non-creditable $300,000 milestone payment upon launch of the first in vitro diagnostic product containing the licensed peptides. Qiagen is also required to pay us, on a product-by-product and country-by-country basis, royalties in the low-single-digit to mid-single-digit percentage on Qiagen’s and its affiliates’ net sales of products containing the licensed peptides, subject to certain customary reductions, for as long as such products are covered by a valid claim of the patents licensed by us to Qiagen under the Qiagen Agreement.

We are solely responsible for managing patent maintenance, prosecution and enforcement during the term of both the Option Exercise Period (defined below) and term of the Qiagen Agreement.

The Qiagen Agreement will expire upon the later to occur of (i) expiration of the last to expire valid claim of patents we license to Qiagen under the Qiagen Agreement or (ii) 15 years from the effective date of the Qiagen Agreement. Should any patents issue from any non-provisional patent applications claiming priority to any of the licensed U.S. provisional patent applications, the current expected expiration date for the last-to-expire licensed patent right is June 17, 2041 (absent any adjustments or extensions of term). Qiagen may terminate the Qiagen Agreement for any reason upon 60 days’ prior written notice to us; provided, however, that Qiagen will be required to fulfill any payment obligations that accrued prior to termination.

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 (PHSA) (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 therapies. Any sublicenses we grant to PHSA’s patent rights must also include a license of our own IP; 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 a 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.

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 are designing 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 will be delivered as a NanoplasmidTM, which was developed by Nature Technology, an Aldevron Company, and has no antibiotic selection element, reducing the risk of inadvertent transmission of antibiotic resistance into T cells. The transposase will be 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. Aldevron has a license from Nature Technology to manufacture research-grade and GMP-grade transposon and transposase. The initial batch of research-grade and GMP-grade transposon and transposase which we intend to use in connection with our near-term pre-clinical studies and clinical trials will be manufactured by Aldevron pursuant to a non-exclusive, fee-for-service supply arrangement pursuant to which we may purchase materials from time-to-time, subject to normal market pricing.

We are developing our manufacturing process using industry standard instrumentation to enable direct transfer of methods from process development to manufacturing. These devices also allow for functionally closed processes in a small footprint. For 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 therapies will be characterized and released using well-developed analytic methods. The final product will be cryopreserved, simplifying logistics and reducing risk of delivery failures. We plan to have controls and safeguards throughout the entire process to ensure product identity, integrity, 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, are all critical for the manufacturing of safe, effective, and well-characterized cell therapies.

Our cell product manufacturing facility in Waltham, MA was designed and built to support multiple programs through Phase 1 and Phase 2 clinical development, with a projected capacity to support treating over 300 patients per year. We believe internalizing our manufacturing process enables us to better control this key aspect of clinical development and reduces the risk of program delay due to third party reliance. We expect to revisit our manufacturing process prior to commencing registrational trials and may use third-party CMOs to manufacture product candidates for our registrational trials.

Competition

We believe our novel and proprietary platform technologies, TargetScan and ReceptorScan, and our in-house cell therapy expertise constitute a meaningful competitive advantage in successfully developing novel and highly 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-T or other cell therapies for the treatment of cancer. We expect to compete with a number of other T-cell therapy companies, including those with target discovery platforms, such as Adaptive Therapeutics, Inc., Immatics N.V., Enara Bio Ltd., Repertoire Immune Medicines, Inc., and 3T Biosciences Inc. In addition, we may face competition from other TCR companies such as Adaptimmune Therapeutics, Plc., Medigene AG, GlaxoSmithKline Pharmaceuticals Ltd, T-Knife GmbH, and Alaunos Therapeutics, Inc. We may also face competition from companies focused on CAR-T, TIL, gammadelta T cell, and other T cell therapies, such as 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., Iovance Biotherapeutics, Inc., Instil Bio, Inc., Achilles Therapeutics plc, Sana Biotechnology, Inc., 2seventy Bio, Inc., Atara Biotherapeutics, Inc., Lyell Immunopharma, Inc., Allogene Therapeutics, Inc., PACT Pharma, Inc., Gadeta B.V., 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 liquid tumor programs, TSC-100

and TSC-101, we may face competition from HighPass Bio, Inc. NexImmune, Inc., VOR Biopharma, Inc., and Marker Therapeutics, Inc., who are also developing cell therapies in the post-HCT setting.

Immunocore’s KIMMTRAK is the first TCR-based therapeutic to receive FDA approval, potentially establishing a regulatory pathway, pricing benchmark, and commercial uptake pattern for TCR-based therapeutics. However, KIMMTRAK is a bispecific antibody indicated for use in a rare patient population with unresectable or metastatic uveal melanoma, which is not directly competitive to TScan. Immunocore’s other programs using TCR-mimic bispecifics in other indications such as cutaneous melanoma may be a more direct competitor to TScan’s products.

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 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 therapies 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 significant share of the market for, and commanding a certain price for any of our TCR-T therapies 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 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 candidates, if approved, are likely to be their efficacy, safety, convenience, 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 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 consisted of a patent family exclusively licensed from BWH, including a pending U.S. non-provisional patent application and multiple pending foreign non-provisional patent applications, relating to methods and compositions for identifying target antigens specific to T cells. In addition, we have filed multiple patent families including multiple pending U.S. provisional patent applications and more than ten 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 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 candidate), anti-HA-2 TCRs (including the TSC-101 TCR-T therapy candidate), TCRs targeting the antigen of TSC-200, anti-HPV TCRs (including the TSC-200 TCR-T therapy candidate), and TCRs targeting the antigen of TSC-204 (including the TSC-204 TCR-T therapy candidate), as well as a phospholipid scrambling reporter-based T cell antigen screening platform and certain screening methods thereof. These patent applications, if issued, are expected to expire on various dates from 2038 through 2042, in each case without taking into account any possible patent term adjustments or extensions and assuming that appropriate maintenance and governmental fees are paid.

Liquid Tumor Program Product Patent Families

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