Xilio Therapeutics, Inc. 10-K

Item 1. Business Overview We are a clinical-stage biotechnology company discovering and developing tumor-activated immuno-oncology, or I-O, therapies with the goal of significantly improving outcomes for people living with cancer without the systemic side effects of current I-O treatments. We are leveraging our proprietary platform to build a pipeline of novel, tumor-activated I-O molecules that are designed to optimize the therapeutic index by localizing anti-tumor activity within the tumor microenvironment, including tumor-activated cytokines and antibodies (including bispecifics) and immune cell engagers (including tumor-activated cell engagers and tumor-activated effector-enhanced cell engagers). Current I-O therapies have curative potential for patients with cancer; however, their potential is significantly curtailed by systemic toxicity that results from activity of the therapeutic molecule outside the tumor microenvironment. Our molecules are engineered to localize activity within the tumor microenvironment with minimal systemic effects, resulting in the potential to achieve enhanced anti-tumor activity and increasing the population of patients who may be eligible to receive our medicines. Our most advanced tumor-activated, clinical-stage product candidates are XTX101, an Fc-enhanced, anti-CTLA-4 monoclonal antibody, or mAb, XTX301, an interleukin 12, or IL-12, therapy, and XTX202, an interleukin 2, or IL-2, therapy. In 2023, we presented clinical data across these programs showing initial clinical validation for each of these molecules and our tumor-activated approach. In addition to our clinical-stage product candidates, we are continuing to leverage our differentiated research platform and expertise in developing tumor-activated I-O therapies to advance preclinical development for tumor-activated bispecific molecules and immune cell engager molecules (including tumor-activated cell engagers and tumor-activated effector-enhanced cell engagers). XTX101 XTX101 is an investigational tumor-activated, Fc-enhanced, high-affinity binding anti-CTLA-4 mAb designed to block CLTA-4 and deplete regulatory T cells when activated (unmasked) in the tumor microenvironment and improve upon the therapeutic index of existing anti-CTLA-4 therapies. In the third quarter of 2023, we entered into a co-funded clinical trial collaboration with F. Hoffmann-La Roche Ltd., or Roche, to evaluate XTX101 in combination with atezolizumab (Tecentriq®) in a multi-center, open-label Phase 1/2 clinical trial. We are currently evaluating the safety and tolerability of the combination in patients with advanced solid tumors in the Phase 1 dose escalation portion of the clinical trial. We plan to select a recommended Phase 2 dose, or RP2D, for XTX101 in combination with atezolizumab in the second quarter of 2024, and subject to the results of the Phase 1 combination dose escalation portion of the trial, we plan to initiate the Phase 2 portion of the trial for XTX101 in combination with atezolizumab in patients with microsatellite stable colorectal cancer, or MSS CRC, in the third quarter of 2024. In addition, we plan to report initial Phase 2 data for XTX101 in combination with atezolizumab in approximately 20 patients with MSS CRC in the fourth quarter of 2024 and in approximately 20 additional patients (40 patients total) in the first quarter of 2025. XTX301 XTX301 is an investigational tumor-activated IL-12 designed to potently stimulate anti-tumor immunity and reprogram the tumor microenvironment of poorly immunogenic “cold” tumors towards an inflamed or “hot” state. In March 2024, our wholly-owned subsidiary Xilio Development, Inc., or Xilio Development, entered into an exclusive license agreement with Gilead Sciences, Inc., or Gilead, pursuant to which it granted Gilead an exclusive global license to develop and commercialize XTX301 and specified other molecules directed at IL-12. For more information, please see “—License and Collaboration Agreements—Exclusive License Agreement with Gilead” below. We are currently evaluating XTX301 in an ongoing Phase 1 first-in-human, multicenter, open-label clinical trial designed to evaluate the safety and tolerability of XTX301 as a monotherapy in patients with advanced solid tumors. In January 2024, we reported preliminary safety data into the third dose level in the Phase 1 dose escalation and anticipate reporting safety, pharmacokinetic, or PK, and pharmacodynamic, or PD, data for XTX301 in the fourth quarter of 2024. 5 Table of Contents XTX202 XTX202 is an investigational tumor-activated, beta-gamma biased IL-2 designed to potently stimulate CD8+ effector T cells and natural killer, or NK, cells without concomitant stimulation of regulatory T cells, or TREGs, when activated (unmasked) in the tumor microenvironment. In March 2024, we announced updated data from our Phase 2 clinal trial evaluating XTX202 as a monotherapy in patients with unresectable or metastatic melanoma and metastatic renal cell carcinoma, or RCC, who have progressed on standard-of-care treatment. Together with previously reported data, we believe these additional data further validate our tumor-activated approach and support the broad potential for XTX202 as a combination therapy. In March 2024, we also announced plans to explore strategic opportunities to continue to develop XTX202 in combination with other agents and, as part of a strategic portfolio reprioritization, plans to discontinue further investment in XTX202 as a monotherapy. Future Opportunities In addition to our most advanced product candidates, we believe our proprietary platform technology has the potential to develop additional product candidates using our tumor-activated masking approach, which is designed to achieve tumor-specific molecule activation and derive a clinically meaningful improvement in therapeutic index. We are currently leveraging our differentiated platform technology, and our unique expertise in masking antibodies and cytokines, to develop a new generation of tumor-activated bispecific molecules and immune cell engager molecules. Subject to obtaining sufficient additional capital, we plan to advance XTX501, our tumor-activated PD-1/IL-2 bispecific development candidate, into IND-enabling studies. We also plan to continue to make focused investments in our promising research-stage pipeline for additional tumor-activated bispecific molecules and immune cell engager molecules (including tumor-activated cell engagers and tumor-activated effector-enhanced cell engagers). We will continue to evaluate opportunities for better tolerated and more efficacious combination therapies, using product candidates from across our portfolio with other cancer therapies, to increase the potential for curative regimens in oncology. March 2024 Private Placement On March 28, 2024, we entered into a securities purchase agreement with certain existing accredited investors, including Bain Capital Life Sciences and Rock Springs Capital, to issue and sell an aggregate of 1,953,125 shares of our common stock at a price of $0.64 per share and prefunded warrants to purchase up to an aggregate of 15,627,441 shares of our common stock at a purchase price of $0.6399 per prefunded warrant share, through a private investment in public equity financing. The prefunded warrants will have an exercise price of $0.0001 per share of common stock, be immediately exercisable and remain exercisable until exercised in full. We anticipate receiving aggregate gross proceeds from the private placement of approximately $11.3 million, before deducting placement agent fees and expenses payable by us. The private placement is expected to close on April 2, 2024, subject to the satisfaction of customary closing conditions. We expect to use the proceeds from the private placement to fund working capital and other general corporate purposes. Our Approach—Improving the Therapeutic Index of I-O Therapies Our focus is to improve upon two of the foundational mechanisms of I-O: cytokines and checkpoint inhibitors. Since the 1980s, cytokines have been explored as a cancer therapy due to their ability to carry messages between cells and serve as master regulators of the body’s response to inflammation and immune attack. Although cytokines have demonstrated compelling clinical efficacy in certain tumors, including the ability to generate sustained complete responses, or CRs, in a subset of patients, their use has been limited by severe systemic toxicity. Similar to cytokines, checkpoint inhibitors have shown the potential to provide meaningful improvements in survival for patients with cancer, but the utilization of these therapies, beyond those that target the immune proteins PD(L)-1, is also limited largely by toxicity. Finally, immune cell engagers, including T cell engaging bispecific molecules, have demonstrated encouraging clinical activity, but treatment is typically associated with significant toxicities including cytokine-release syndrome and on-target/off-tumor cytotoxicity. Our goal is to overcome the limitations of current I-O therapies by developing products with an improved efficacy-to-toxicity ratio, or therapeutic index. The toxicities for cytokines, checkpoint inhibitors and immune cell engagers stem from their activity outside of the tumor microenvironment. Our proprietary platform is designed to overcome these systemic toxicities by creating tumor-activated molecules and unleashing the activity of tumor-activated cytokines and antibodies 6 Table of Contents (including bispecifics) and immune cell engagers (including tumor-activated cell engagers and tumor-activated effector-enhanced cell engagers) in the tumor microenvironment. These molecules are intended to be inactive until they reach the tumor microenvironment, where they are activated by the unique conditions of the tumor microenvironment, resulting in localized clinical activity with minimal dose-limiting toxicities. To achieve this tumor selectivity, we apply our platform, which includes engineered features and a proprietary protein masking technology that seeks to minimize interaction with healthy tissue and cells by rendering our molecules inactive until reaching the tumor. Our platform is also designed to enable optimal PK by preventing undesired binding and elimination outside of the tumor microenvironment, resulting in geographically localized pharmacology. The engineered features are designed to ensure that our product candidates are stable molecules with well-understood properties and a reproducible manufacturing approach. Our Strategy Our vision is to transform the lives of patients with cancer by harnessing the power of highly potent, tumor-selective I-O therapies that deliver deep and durable clinical responses. By leveraging our proprietary platform for tumor-activated molecules, we aim to discover, develop and, ultimately, commercialize I-O therapies that overcome the known limitations of today’s approaches and provide effective, tolerable and durable therapeutic options for patients and their physicians. In order to achieve these goals, the key elements of our strategy are to: ● Rapidly advance clinical development for XTX101, our tumor-activated, Fc-enhanced anti-CTLA-4, through our co-funded clinical collaboration with Roche. In the third quarter of 2023, we entered into a co-funded clinical trial collaboration with Roche to evaluate XTX101 in combination with atezolizumab (Tecentriq®) in a multi-center, open-label Phase 1/2 clinical trial. We are currently evaluating XTX101 in combination with atezolizumab (Tecentriq®) in Phase 1 combination dose escalation. We plan to select a RP2D for XTX101 in combination with atezolizumab in the second quarter of 2024, and subject to the results of the Phase 1 combination dose escalation portion of the trial, we plan to initiate the Phase 2 portion of the trial for XTX101 in combination with atezolizumab in patients with MSS CRC in the third quarter of 2024. In addition, we plan to report initial Phase 2 data for XTX101 in combination with atezolizumab in approximately 20 patients with MSS CRC in the fourth quarter of 2024 and in approximately 20 additional patients (40 patients total) in the first quarter of 2025. ● Rapidly advance clinical development for XTX301, our tumor-activated IL-12, through our partnership with Gilead. In March 2024, we entered into an exclusive license agreement with Gilead to develop and commercialize XTX301, as well as other molecules directed at IL-12. We are currently evaluating XTX301 in Phase 1 monotherapy dose escalation, and we anticipate reporting safety, PK and PD data for XTX301 in the fourth quarter of 2024. Under our license agreement with Gilead, we are responsible for conducting clinical development for XTX301 in the ongoing Phase 1 clinical trial through an initial planned Phase 2 dose expansion, and then following the delivery by us of a specified clinical data package for XTX301, Gilead can elect to transition responsibilities for the development and commercialization of XTX301 to Gilead, subject to the terms of the license agreement and payment by Gilead of a transition fee. ● Explore opportunities for strategic partnerships to evaluate XTX202, our tumor-activated, beta-gamma biased IL-2, in combination with other agents. In March 2024, we announced additional data from our Phase 2 clinical trial evaluating XTX202 in patients with metastatic RCC or unresectable or metastatic melanoma. Together with previously reported data, we believe these additional data further validate our tumor-activated approach and support the broad potential for XTX202 as a combination therapy. In March 2024, we also announced plans to explore strategic opportunities to continue to develop XTX202 in combination with other agents and, as part of a strategic portfolio reprioritization, plans to discontinue further investment in XTX202 as a monotherapy. ● Leverage our promising research platform to advance differentiated, tumor-activated bispecific molecules and immune cell engager molecules (including tumor-activated cell engagers and tumor-activated effector-enhanced cell engagers). We believe our proprietary platform technology has the potential to develop additional product candidates using our tumor-activated masking approach. In particular, we are currently leveraging our 7 Table of Contents differentiated platform technology and our unique expertise in masking antibodies and cytokines to develop a new generation of tumor-activated bispecific molecules and immune cell engager molecules. Subject to obtaining sufficient additional capital, we plan to advance XTX501, our tumor-activated PD-1/IL-2 bispecific development candidate, into IND-enabling studies. We also plan to continue to make focused investments in our promising research-stage pipeline for additional tumor-activated bispecific molecules and immune cell engager molecules (including tumor-activated cell engagers and tumor-activated effector-enhanced cell engagers). We will continue to evaluate opportunities for better tolerated and more efficacious combination therapies, using product candidates from across our portfolio with other cancer therapies, to increase the potential for curative regimens in oncology. ● Leverage the broad applicability of our proprietary platform for tumor-activated I-O molecules through strategic collaborations and partnerships. We believe the collective components of our proprietary platform technology and the reproducibility it enables in our drug discovery and development efforts present a meaningful opportunity for us to leverage our platform in combination with other agents in oncology. We plan to continue to explore strategic collaborations and partnership that would enable us to access capital, accelerate the development of our current product candidates or additional product candidates or programs, evaluate our current or additional product candidates in combination with other agents, and expand our capabilities, pipeline opportunities and product offerings, particularly where a collaborator may have expertise or capabilities that are synergistic or additive to our own. About I-O The discovery of a role for immunotherapy in the treatment of cancer was made more than 100 years ago, when William Coley treated patients with heat-treated bacterial toxins, resulting in a profound anti-tumor effect in some of those patients. Two of the most important mechanisms within I-O are cytokines and checkpoint inhibitors, with cytokine therapies having been introduced in the 1980s and checkpoint inhibitors in the period after 2011, when the first such product was approved. Both therapeutic approaches are known to provide efficacy in terms of clinical responses and tumor shrinkage. However, toxicities have limited the application of these therapies, resulting in the need to dose-reduce, dose-interrupt or discontinue many patients from treatment. Immune checkpoint inhibitors are associated with immune-related adverse events, or AEs, that may affect any organ system and may be life-threatening or fatal to patients. Cytokines in particular are associated with broad ranging multi-organ toxicities that can be lethal and have limited the development of this class of potential therapies. Anti-PD-1/PD-L1 checkpoint inhibitors have been used broadly because they generally achieve efficacy with minimal systemic toxicity, enabling their administration at their maximally effective doses. Anti-PD-1/PD-L1 treatments have become the most widely utilized immunotherapy agent in oncology, with the U.S. Food and Drug Administration, or FDA, approvals in more than a dozen separate tumor types and $27 billion in worldwide sales in 2020. Our mission is to overcome the limitations of cytokine therapies and checkpoint inhibitors, such as anti-CTLA-4, and make immunotherapies beyond anti-PD-1/PD-L1 treatments more accessible, efficacious and safe for patients with cancer. The promise and limitations of checkpoint inhibitors Checkpoint inhibitors have become mainstays in cancer therapy since the FDA approved ipilimumab, an anti-CTLA-4 therapy, in 2011. Similar to cytokines, checkpoint inhibitors have shown the potential to provide meaningful improvements in survival for patients with cancer, but the utilization of these therapies has been limited largely by toxicities. These toxicities, which can be life-threatening or fatal, have resulted in the need to dose-reduce, dose-interrupt or discontinue many patients from treatment. To date, anti-PD-1/PD-L1 checkpoint inhibitors have been used broadly due to their ability to achieve efficacy with minimal systemic toxicity, enabling their administration at their maximally effective doses. In contrast, while the clinical benefit of CTLA-4 blockade to patients with cancer is well-established, the efficacy of current CTLA-4 therapies is impaired by dose-limiting toxicities arising from systemic immune activation. This has reduced the use of anti-CTLA-4 mAbs both as a monotherapy and in combination therapy. We believe XTX101, our tumor-activated, Fc-enhanced high affinity binding anti-CTLA-4, has the potential to overcome these limitations and deliver the full clinical benefit of anti-CTLA-4 mechanisms without the dose-limiting toxicities associated with existing CTLA-4 treatments. 8 Table of Contents The promise and limitations of cytokines Cytokines are small signaling proteins that serve as master regulators of the body’s response to inflammation and immune attack. There are multiple cytokines, including IL-2, which are approved in a range of oncology and non-oncology indications. Aldesleukin, a high-dose IL-2 therapy, was first approved in 1992 as a monotherapy for patients with melanoma and RCC. Similarly, IL-12 development has been relentlessly pursued due to its unique potential to treat immunologically cold tumors, but currently there are no approved IL-12 therapies. Cytokines such as IL-2 and IL-12 have not achieved therapeutic success in a broad population of patients because their use has been limited by severe toxicity, including fatal outcomes. We believe XTX301, our tumor-activated IL-12 product candidate, has the potential to overcome these limitations and deliver a therapeutic dose with low systemic toxicity and the ability to achieve a broad therapeutic index. We also believe that XTX202, our IL-2 product candidate, has broad potential as a combination therapy based on the safety, PK and PD data reported to date from our Phase 1 and Phase 2 clinical trials. I-O Combinations The ability to combine oncology agents has been an important step in developing effective cancer regimens. Combination chemotherapy can be curative in settings where single agents have had limited efficacy and were not considered curative. The substantial dose-limiting toxicities associated with I-O agents has prevented these agents from being combined effectively. The ultimate promise of I-O for patients is dependent upon the ability to develop I-O agents that can be combined at their optimal doses without life-threatening toxicity. The severe toxicity of IL-2 has limited the ability to combine IL-2 with other cancer treatments without compromising the dose administered. Similarly, data from third-party clinical trials has demonstrated that the combination of ipilimumab, an anti-CTLA-4 therapy, with nivolumab, which targets the immune checkpoint protein PD-1, was associated with improved clinical outcomes, but it was limited by significantly higher risk of all-grade and high-grade immune-related AEs such as pruritus, rash, diarrhea, colitis, elevation of the liver enzyme alanine transaminase, known as ALT, hyperthyroidism, hypophysitis and pneumonitis. Importantly, combination therapy generally requires use of low dose ipilimumab at 1 mg/kg rather than the more efficacious dose of 10 mg/kg. Even at the lower dose, ipilimumab combination therapy is poorly tolerated, with AEs causing up to 80% of patients to discontinue treatment, up to 50% of patients requiring emergency room visits and up to 36% of patients requiring hospitalization. The potential of our tumor-activated molecules to minimize the systemic toxicity of I-O could allow us to combine I-O agents to meaningfully improve survival in a broader range of tumor types. We are currently evaluating XTX101, our anti-CTLA-4 product candidate, in combination with atezolizumab, and as discussed above, we plan to explore opportunities to continue to develop XTX202, our IL-2 product candidate, in combination with other agents. Our Solution: Our Proprietary Platform Enables Tumor-Activated I-O Molecules Designed to Optimize Their Therapeutic Index I-O therapies have curative potential for patients with cancer. However, this potential has been significantly curtailed to date by dose-limiting toxicities that result from activity of the therapeutic molecule outside the tumor microenvironment. We believe that selectively targeting the activity of I-O agents to the tumor microenvironment can overcome these dose-limiting toxicities and enable maximal therapeutic benefit for patients. Tumor-selective activation could be achieved by harnessing unique characteristics of the tumor microenvironment to activate therapeutic molecules locally that have minimal or non-detectable levels of activity outside of the tumor microenvironment. Matrix metalloproteases, or MMPs, are enzymes involved in protein degradation that are essential for tumor growth and metastasis because they regulate key processes within the tumor microenvironment, including tumor growth, angiogenesis, invasion and metastasis. MMPs are dysregulated in the tumor microenvironment, resulting in preferential activity of MMPs in the tumor microenvironment by comparison to non-tumor, healthy tissues. As a result, we believe that our platform for tumor-activated molecules, which is designed to harness tumor MMP activity, can design molecules that selectively activate within the tumor microenvironment while maintaining minimal or non-detectable levels of activity outside of the tumor microenvironment. Our platform enables us to engineer a broad range of immune-modulatory molecules, including tumor-activated cytokines and antibodies (including bispecifics) and immune cell engagers (including tumor-activated cell engagers and tumor-activated effector-enhanced cell engagers), that contain masking domains designed to minimize their activity outside of 9 Table of Contents the tumor microenvironment and turn on selectively in the tumor microenvironment where they are preferentially activated by tumor MMPs. Specifically, MMPs enzymatically cleave a protease cleavage site incorporated in a peptide linker that connects the masking protein domain to the active agent. This separates the mask from the active agent, enabling the unmasked agent to promote an anti-tumor response within the tumor microenvironment. Key features of our tumor-activated molecules exemplify the engineering approach that underpins our platform. Each feature contributes to multiple characteristics of the molecule that are designed to enable tumor selective biological activity and tumor growth inhibition while minimizing toxicity outside of the tumor microenvironment. The general architecture of each of our tumor-activated molecules is: · a masking domain; · linker sequences; · a protease cleavage site; · a cleavable or retained half-life extension domain for cytokine, immune cell engager and bispecific molecules, as appropriate; and · the effector domain (i.e., an engineered cytokine, antibody or immune cell engager). The engineered features are designed to ensure that our product candidates are stable molecules with well-understood properties and a reproducible manufacturing approach. We have applied our masking approach to cytokines and antibodies that regulate immune checkpoints, and with our earlier stage work, we have expanded the application of our platform to tumor-activated bispecific molecules and immune cell engager molecules (including tumor-activated cell engagers and tumor-activated effector-enhanced cell engagers). Our molecules are designed to contain a masking domain that is released by protease cleavage. When the linker sequence, which contains a protease cleavage site, is cleaved by MMPs, the masking domain is released, allowing the unmasked molecule to bind to the target receptor, or in the case of an immune cell engager, bind to the immune cell and tumor antigen to facilitate an immune synapse. Before cleavage by the MMPs in the tumor microenvironment, the engineered molecule is designed to minimize interaction with healthy tissue and cells outside the tumor microenvironment. Specifically, there is no binding to target receptors, and the molecule has a long half-life outside the tumor microenvironment. After cleavage in the tumor microenvironment, the engineered molecule is locally activated and has a relatively short half-life. ​ Key Features of Xilio’s Tumor-Activated Molecules 10 Table of Contents We believe that the characteristics of our proprietary platform for tumor-activated molecules described above will enable the following key advantages: · masking that takes advantage of multiple intra-molecular interactions, minimizing the risk of activity outside of the tumor microenvironment and therefore minimizing the risk of toxicity; · engineering the active molecule such that unmasking in the tumor microenvironment promotes a potent, localized anti-tumor immune response; · early consideration and incorporation of manufacturing and development aspects into the design of molecules to facilitate production of high-quality drug product for clinical use; · half-life optimized molecules with prolonged half-life in the inactive (masked) state to support administration to patients on a schedule consistent with other biologics agents; and · locally activating molecules that have a short half-life in the tumor microenvironment, which minimizes the risk of the activated molecule exhibiting activity outside of the tumor microenvironment and, therefore, further reduces the risk of toxicity. Our Pipeline Leveraging our platform technology, we are building a pipeline of tumor-activated I-O molecules to treat cancer, including tumor-activated cytokines and antibodies (including bispecifics) and immune cell engagers (including tumor-activated cell engagers and tumor-activated effector-enhanced cell engagers). Our goal is to overcome the limitations of current I-O therapies by developing products with an improved therapeutic index. Consistent with this goal, we selected molecules that have prior clinical validation demonstrating therapeutic benefit, but that have been limited by significant toxicities that we believe can be addressed with our approach. Program Tumor Types Mechanism of Action Stage of Development Partnerships XTX101 in combination with atezolizumab (1) Advanced MSS CRC anti-CTLA-4 + PD-L1 Phase 1 combination dose escalation ongoing Co-funded clinical collaboration with Roche XTX301 (2) Advanced Solid Tumors IL-12 Phase 1 monotherapy dose escalation ongoing Exclusive global license with Gilead XTX202 Advanced RCC and Melanoma IL-2βγ Phase 2 monotherapy enrollment complete (3) Plan to explore strategic opportunities to develop in combinations (3) XTX501 Advanced Solid Tumors PD-1/IL-2 bispecific Development candidate (4) ​ Additional research-stage programs Undisclosed Tumor-activated immune cell engagers Discovery-stage ​ 1. Evaluating XTX101 in combination with atezolizumab (Tecentriq®) in Phase 1 combination dose escalation trial and planned Phase 2 combination trial in MSS CRC. 2. Evaluating XTX301 in Phase 1 monotherapy dose escalation for the treatment of advanced solid tumors. 3. Plan to discontinue further investment in XTX202 as a monotherapy. 4. Plan to advance in IND-enabling studies, subject to sufficient additional capital. ​ ​ XTX101, Our Clinical-Stage, Tumor-Activated, Fc-Enhanced, High Affinity Binding Anti-CTLA-4 Product Candidate XTX101 is an investigational tumor-activated, Fc-enhanced, high-affinity binding anti-CTLA-4 mAb designed to block CLTA-4 and deplete TREGs when activated (unmasked) in the tumor microenvironment and improve upon the therapeutic index of existing anti-CTLA-4 therapies. In the third quarter of 2023, we entered into a co-funded clinical trial collaboration with Roche to evaluate XTX101 in combination with atezolizumab (Tecentriq®) in a multi-center, open- 11 Table of Contents label Phase 1/2 clinical trial. We are currently evaluating the safety and tolerability of the combination in patients with advanced solid tumors in the Phase 1 dose escalation portion of the clinical trial. Subject to the results of Phase 1 combination dose escalation, we plan to evaluate the safety and efficacy of the combination in the Phase 2 portion of the clinical trial in patients with microsatellite stable colorectal cancer. Background on CTLA-4 CTLA-4 is an immune checkpoint protein that is well-established as playing a central role in the development of tumors. The scientific insight that led to the early development of CTLA-4 therapeutics is attributable to investigators recognizing CTLA-4 as a protein on T cells that acts as a brake on T cell activation. By removing this brake, T cells were freed to attack cancer. This work led to the development and FDA approval of ipilimumab, a CTLA-4 mAb, for the treatment of unresectable or metastatic melanoma at a dose of 3 mg/kg in 2011 and in additional indications in subsequent years. While anti-CTLA-4 therapies such as ipilimumab have demonstrated meaningful efficacy across a range of tumor types, autoimmune toxicities have significantly limited their use to date. Clinical trials have shown that 20% of ipilimumab-treated melanoma patients survive at least three years, and a subset survive for 10 years or longer. Ipilimumab remains one of the most impactful drugs for these patients; however, the number of patients who benefit from treatment with ipilimumab remains limited due to its toxicity. Investigation of dose-response in two third-party clinical trials of melanoma patients showed that higher doses of ipilimumab are likely to increase the proportion of patients who benefit; however, the increased dose also resulted in an unacceptable toxicity profile for most patients. In a Phase 2 trial of ipilimumab conducted by Bristol-Myers Squibb Company, a dose range of 0.3 mg/kg to 10 mg/kg was tested and efficacy was measured both by response rate and by clinical outcome. Both the response rate and median overall survival, or mOS, were higher at 10 mg/kg than at 3 mg/kg, with the 0.3 mg/kg dose determined as being ineffective. The rate of severe AEs was 25% at the 10 mg/kg dose, 7% at the 3 mg/kg dose and 0% at the ineffective dose of 0.3 mg/kg. Similarly, as shown in the table below, in a Phase 3 trial conducted by Bristol-Myers Squibb Company, mOS was higher at the 10 mg/kg dose but resulted in unacceptable toxicity for most patients. Therefore, we believe that achieving a three-fold increase in therapeutic index would be transformational. High-Dose Ipilimumab Improved Survival but Resulted in Unacceptable Toxicity ​ ​ ​ ​ ​ ​ ​ Adverse Events: Dose (mg/kg) ​ mOS (mo) ​ Gr 3/4 irAEs / disconts. (%) 3 11.5 14 / 19 10 15.7 30 / 31 ​ Ipilimumab has shown preliminary evidence of promising anti-tumor activity in a range of tumor types outside of its currently approved indications, but successful additional approvals have been limited due to its toxicity. For example, ipilimumab has been observed to be more active when combined with the anti-PD-1/PD-L1 antibody nivolumab. However, the combination of ipilimumab and nivolumab has been shown to cause a greatly increased rate of immune-related toxicity when compared to treatment with either ipilimumab or nivolumab as a monotherapy. Clinical results from patients who express high-affinity FcγR polymorphisms have shown improved responses to ipilimumab, but efforts to improve the potency of the antibody have been limited by perceived toxicity risk. There remains a critical need to develop safe and effective forms of anti-CTLA-4 mAbs that can achieve efficacious doses within the tumor microenvironment. Our Solution: XTX101, a Tumor-Activated, Fc-Enhanced Anti-CTLA-4 XTX101 is a clinical-stage, tumor-activated, Fc-enhanced anti-CTLA-4 mAb that is designed to improve upon the therapeutic index of existing anti-CTLA-4 therapies by overcoming potency and tolerability limitations. Our goal is to demonstrate an improved safety profile enabling higher anti-CTLA-4 exposure in the tumor that will result in increased efficacy. In preclinical studies, we observed the following tolerability and activity profile of XTX101: · improved in vivo potency and the intra-tumoral PD effects of XTX101 are consistent with the improved potency being a result of the higher affinity binding to the target CTLA-4 and enhanced IgG1-Fc effector function, which 12 Table of Contents further improves checkpoint inhibition and enhances antibody-dependent cellular cytotoxicity to deplete immune-suppressive TREGs in the tumor microenvironment; · reduced peripheral immune activity due to masking of the CDR sequences; and · activation by protease-dependent release of the masks, which acts selectively in the tumor microenvironment and minimizes toxicity associated with systemic immune activation. XTX101 is designed to enhance the desirable features of an anti-CTLA-4 antibody while mitigating the known limitations of anti-CTLA-4 antibodies due to toxicity. We expect this combination of features to result in an increased therapeutic index. Tumor-Activated Design Components of XTX101 ​ Preliminary Phase 1 Monotherapy Data Presented in May 2023 In May 2023, we announced initial Phase 1 monotherapy dose escalation data for XTX101. As of a data cutoff date of May 2, 2023, 25 patients had been treated with XTX101, including dose levels ranging from 7 mg to 180 mg administered once every three weeks, or Q3W, and one dose level at 150 mg administered once every six weeks, or Q6W. Of these patients, 20 patients were dosed in monotherapy dose-escalation and five patients were dosed in monotherapy dose-expansion. ​ Patients had a wide range of advanced and treatment-refractory solid tumors, including colorectal cancer, or CRC, non-small cell lung cancer, or NSCLC, and pancreatic cancer. In addition, 76% of patients had been previously treated with at least three prior lines of anti-cancer therapy, and 44% had been previously treated with at least one I-O agent. As of the data cutoff date, three patients were continuing on treatment with XTX101, and 22 patients had discontinued treatment with XTX101. ​ Preliminary Safety Data ​ A recommended Phase 2 dose, or RP2D, and schedule of 150 mg Q6W was determined based on the favorable preliminary safety, PK and PD data for XTX101. At the RP2D, no dose-limiting toxicities were observed, and there was no reported evidence of immune-related endocrine or skin AEs that are commonly associated with systemically active anti-CTLA-4 agents. In addition, evidence of effective masking of XTX101 was demonstrated by low levels of unmasked drug detected in peripheral circulation, and XTX101 achieved target PK exposure at the RP2D, reaching the targeted area under the curve, or AUC, and peak concentration, or C max . 13 Table of Contents ​ As of the data cutoff date of May 2, 2023: ​ ● Across all dosing levels and dosing intervals, no Grade 4 or Grade 5 treatment-related AEs were reported by investigators. ​ ● Among seven patients who received XTX101 administered at the RP2D of 150 mg on a Q6W dosing schedule, the most common treatment-related AEs (≥10% incidence) of any grade reported by investigators were diarrhea (14%), fatigue (14%) and decreased appetite (14%). In these patients, no treatment-related colitis or infusion related reaction of any grade was observed. Investigators reported only one Grade 3 treatment-related AE of diarrhea, which occurred after two doses and resolved after five days without steroid use. This patient tolerated two additional doses of XTX101 after dose reduction to 75 mg Q6W without any symptom recurrence. At the RP2D of 150 mg Q6W, this was the only patient with a dose reduction due to an AE, and no patients discontinued treatment due to a treatment-related AE. ​ ● Among 18 patients who received XTX101 administered on a Q3W dosing schedule, the most common treatment-related AEs (≥10% incidence) of any grade reported by investigators were diarrhea (28%), colitis (28%), infusion related reaction (28%), nausea (17%), vomiting (17%) and abdominal pain (11%). Of these, investigators reported the following Grade 3 treatment-related AEs: diarrhea (6%), colitis (22%) and infusion related reaction (17%). Infusion related reactions were associated with antidrug antibodies. Across all dose levels administered Q3W, two patients had dose reductions due to AEs, and four patients discontinued treatment due to an infusion related reaction. ​ Preliminary Anti-Tumor Activity Data ​ A partial response, or PR, was observed at nine weeks in one patient with advanced PD-L1 negative NSCLC with hepatic metastases treated with XTX101 at the 150 mg Q6W dose level and confirmed after the data cutoff date at week 27. The only treatment-related AE reported for this patient was Grade 1 fatigue. In addition, PD markers for anti-CTLA-4 reported for this patient showed minimal immune activation in peripheral circulation, demonstrating evidence of tumor-selective activation of XTX101. ​ Updated Phase 1 Monotherapy Data Presented at the European Society for Medical Oncology (ESMO) Immuno-Oncology Congress in December 2023 In December 2023, we reported updated Phase 1 monotherapy data for XTX101 at the ESMO Immuno-Oncology Congress. As of a data cutoff date of November 13, 2023, 36 patients with advanced solid tumors had been administered XTX101 monotherapy, including 18 patients at the RP2D and schedule of 150 mg Q6W. ​ Patients treated at the RP2D of 150 mg Q6W were heavily pre-treated, with 83% of patients receiving three or more lines of anti-cancer therapy and 56% previously treated with an immunotherapy. ​ Preliminary Safety Data ​ At the RP2D of 150 mg Q6W, 18 patients (including nine patients previously reported) were evaluable for safety as of the data cutoff date of November 13, 2023: ​ ● Safety data were consistent with previously reported results. XTX101 monotherapy was generally well-tolerated with treatment-related AEs primarily Grade 1 or 2, and no patients discontinued treatment due to a treatment-related AE. In addition, as previously reported, only one patient had a dose reduction due to an AE. ​ ● The most common treatment-related AE of any grade (≥10% incidence) reported by investigators was fatigue (11%). ​ 14 Table of Contents ● As previously reported, investigators reported only two Grade 3 treatment-related AEs: Grade 3 treatment-related AE of diarrhea, which occurred after two doses and resolved after five days without steroid use, and one Grade 3 treatment-related AE of dermatitis. ​ In addition, no Grade 4 or 5 treatment-related AEs were reported by investigators across all dosing levels and dosing intervals. ​ Preliminary Anti-Tumor Activity Data ​ At the RP2D of 150 mg Q6W, 12 patients were evaluable for anti-tumor activity as of the data cutoff date: ​ ● As previously reported, a confirmed PR was observed in a patient with Stage 4 PD-L1 negative NSCLC, including complete resolution of liver metastases. The confirmed PR continued through 36 weeks of treatment with XTX101, with the patient discontinuing treatment after week 36 due to an unrelated AE. ​ ● Additional data reported demonstrated a disease control rate, or DCR, of 33% in late-line and I-O refractory patients administered XTX101 monotherapy at the RP2D of 150 mg Q6W, consisting of the confirmed PR in the NSCLC patient and stable disease in three patients (triple-negative breast cancer, melanoma and MSS CRC (n=1 each)). ​ Preliminary Pharmacokinetic Data ​ As previously reported, consistent with the tumor-selective design for XTX101, preliminary pharmacokinetic analyses demonstrated 96% activation of XTX101 in a melanoma tumor and 73% activation in a metastatic liver lesion in a CRC patient, compared to minimal peripheral activation of XTX101 of 13% in both patients. Cytokine Programs The major focus in our cytokine programs is the development of tumor-activated cytokines with exemplary clinical activity and tolerability. These cytokine programs include our clinical-stage, tumor-activated product candidates, XTX301 (IL-12) and XTX202 (IL-2), as well as discovery-stage programs for oncology. XTX301, Our Clinical-Stage, Tumor-Activated IL-12 Product Candidate XTX301 is an investigational tumor-activated IL-12 designed to potently stimulate anti-tumor immunity and reprogram the tumor microenvironment of poorly immunogenic “cold” tumors towards an inflamed or “hot” state. In March 2024, our wholly-owned subsidiary Xilio Development entered into an exclusive license agreement with Gilead pursuant to which it granted Gilead an exclusive global license to develop and commercialize XTX301 and specified other molecules directed at IL-12. For more information, please see “—License and Collaboration Agreements—Exclusive License Agreement with Gilead” below. We are currently evaluating XTX301 in an ongoing Phase 1 first-in-human, multicenter, open-label clinical trial designed to evaluate the safety and tolerability of XTX301 as a monotherapy in patients with advanced solid tumors. In January 2024, we reported preliminary safety data into the third dose level in the Phase 1 dose escalation and anticipate reporting safety, PK and PD data for XTX301 in the fourth quarter of 2024. 15 Table of Contents Background on IL-12 IL-12 is a potent, pro-inflammatory cytokine produced by antigen-presenting cells such as dendritic cells, macrophages and B cells. IL-12 has two subunits, p35 and p40, that together form a heterodimer protein. IL-12 is a key cytokine in the body’s response to pathogen infection, sending a signal to T cells, among others. IL-12 interacts with diverse immune cells, including CD4+ T cells, CD8+ effector T cells, NK cells, monocytes and macrophages. IL-12’s broad range of pro-inflammatory functions suggests that it could potentially be highly potent in controlling anti-cancer immunity. IL-12 has been shown in preclinical studies to induce robust anti-tumor effects against many types of malignancies and it has been tested against multiple human cancers in clinical trials. Recombinant human IL-12 has been evaluated in clinical trials, and anti-tumor efficacy was observed in a small number of patients across a range of tumor types. Unfortunately, systemic IL-12 therapy has historically caused severe AEs in patients with cancer. Life-threatening liver damage, called hepatotoxicity, was identified during the early development of previous IL-12 therapies, which severely limited the dose of IL-12 that could be administered, and further trials to evaluate efficacy were therefore conducted at sub-optimal doses due to the toxicity. In an early Phase 2 trial of recombinant human IL-12, the MTD of 0.5 μg/kg (administered in days 1-5 in a 21-day dosing cycle) caused severe side effects in 70% of patients, or 12 of 17 patients, of whom two died from gastrointestinal bleeding and multi-organ failure, respectively. The severe toxicities indicated that recombinant human IL-12 could not be used systemically due to rapid increases in the cytokines IFN-γ, TNF-α and IL-6 that caused a cytokine storm syndrome characterized by systemic inflammation, multi-organ dysfunction and immune cytopenias. Efforts to overcome these systemic liabilities include alternate drug delivery approaches such as intra-tumoral administration of IL-12 encoding DNA vaccines or administration of oncolytic viruses expressing IL-12. Despite activity in individual lesions, cancer is a systemic disease that cannot be cured with local therapy once it has reached an advanced stage. Therefore, to unleash the potential for IL-12 in the majority of patients with advanced or metastatic cancer, an IL-12 that can be administered systemically but act locally at the tumor site is needed. The failure of systemic IL-12 to induce meaningful anti-tumor efficacy is generally attributed to tolerability, which limits the dose and, as a result, the ability to reach therapeutic concentrations within the tumor microenvironment. Therefore, maximizing the amount of IL-12 that reaches the tumor, while minimizing exposure of non-tumor tissue, may be critical for a safe and effective anti-tumor response. Tumor-selective activation is therefore a desirable therapeutic profile. Our Solution: XTX301, a Tumor-Activated IL-12 Our goal for our IL-12 program is to create a tumor-activated, extended half-life IL-12 therapeutic with minimal peripheral effects. We are using our platform technology and proprietary approach to achieve systemic delivery of tumor-activated IL-12, which we believe would have potential as a monotherapy and in combination with other therapies. The design of our masked IL-12 cytokine molecule is closely related to that of our masked IL-2 cytokine molecule, described below, which illustrates the flexibility and robustness of our cytokine engineering approach. The masking domain is designed to prevent binding to the cell-surface IL-12 receptor, unless the linker containing the protease site is cleaved by proteases preferentially active in the tumor microenvironment. The half-life extension domain is designed to overcome the short circulating half-life of the native cytokine and the overall molecule is designed to enhance the efficiency of manufacturing. 16 Table of Contents Tumor-Activated Design Components of XTX301 ​ ​ We have undertaken extensive preclinical studies that demonstrated the ability of XTX301 to induce potent anti-tumor activity and PD changes consistent with known IL-12 biology. Importantly, these effects on the tumor were observed without inducing concomitant systemic toxicity, which provides evidence that the masking design was performing as intended in preclinical studies. ​ Preliminary Phase 1 Dose Escalation Safety Data Reported in January 2024 In January 2024, we reported preliminary safety data into the third dose level in the Phase 1 clinical trial. As of a data cutoff date of January 5, 2024, nine patients had been treated with XTX301 in the outpatient setting in Phase 1 dose escalation at three dose levels ranging from 5 ug/kg to 45 ug/kg administered once every three weeks. XTX301 was generally well-tolerated across all dose levels with no dose-limiting toxicities observed in patients as of the data cutoff date. We anticipate reporting safety, PK and PD data for XTX301 in the fourth quarter of 2024. XTX202, Our Clinical-Stage, Tumor-Activated IL-2 Product Candidate XTX202 is an investigational tumor-activated, beta-gamma biased IL-2 designed to potently stimulate CD8+ effector T cells and NK cells without concomitant stimulation of TREGs when activated (unmasked) in the tumor microenvironment. In March 2024, we announced updated data from our Phase 2 clinal trial evaluating XTX202 as a monotherapy in patients with unresectable or metastatic melanoma and metastatic RCC who have progressed on standard-of-care treatment. Together with previously reported data, we believe these additional data further validate our tumor-activated approach and support the broad potential for XTX202 as a combination therapy. In March 2024, we also announced plans to explore strategic opportunities to continue to develop XTX202 in combination with other agents and, as part of a strategic portfolio reprioritization, plans to discontinue further investment in XTX202 as a monotherapy. Background on IL-2 IL-2: Extensive clinical evidence of the promise and limitations of cytokines As shown in the figure below, high-dose IL-2 has resulted in long-term survival in a subset of patients who had achieved a CR. We believe that patients who develop a CR when treated with high-dose IL-2 are highly likely to achieve a long-term durable response or cure. 17 Table of Contents Survival of Patients Who Achieved a CR with High-Dose IL-2 Historical use of IL-2 in cancer has been accompanied by severe toxicity The power of IL-2 is promising, but it has been greatly reduced due to toxicities. When administered locally, IL-2 has been shown to be clinically active and well-tolerated, shrinking local cancerous lesions and reducing malignant effusions. However, when administered systemically, treatment with IL-2 has been shown to induce severe toxicities, including vascular leak syndrome, or VLS, myocardial infarction, or heart attack, acute renal failure and immune-mediated neuropathy. This toxicity profile greatly limits its current use. In order to localize IL-2, many groups have tried linking IL-2 to tumor-targeting mAbs, creating fusion proteins. These fusion proteins can accumulate in a tumor and create locally high IL-2 concentrations. However, the use of cytokine fusion proteins has not prevented systemic toxicity because the long circulating half-life of antibody fusions and unexpected cleavage of IL-2 from the antibody domain has contributed to high systemic IL-2 levels in some cases. The toxicities associated with early IL-2 therapies, such as aldesleukin, are hypothesized to be associated in part with binding and signaling through the high affinity αβγ IL-2receptor on immune cells or vascular endothelial cells. In addition, the αβγ IL-2receptor is expressed at high levels on regulatory T cells, or TREGs, which act to inhibit the immune response, whereas the intermediate affinity βγ IL-2 receptor is expressed on cells that promote immune response including CD8+ effector T cells and NK cells. Modeling of IL-2 activity in preclinical animal tumor models and evaluation of dosage and dose-frequency data from patients has suggested that IL-2 has a steep dose-activity curve, with reduced exposure impacting both efficacy and toxicity. IL-2 anti-tumor activity and toxicity are both dependent on the amount of IL-2 administered. Therefore, in order to provide the greatest benefit to patients, the goal is to engineer a form of IL-2 that can minimize systemic effects while harnessing and directing activity to the tumor microenvironment. Rationale for non-alpha IL-2 The application of cytokines to treat cancer fits with the role these signaling molecules have evolved to play in the body. Many key cytokines, including IL-2, regulate the immune system, and it is now recognized that there are immune stimulatory cytokines, immune suppressive cytokines and cytokines that have multiple activities on different target cell types. IL-2 is a master regulator of immune responses and has been investigated extensively as a potential anti-cancer immunotherapy. IL-2 supports the function, survival and proliferation of T cells, including the subset of T cells known as CD8+ effector T cells that are most closely linked to anti-tumor immunity. The activities of IL-2 are driven by two classes of receptor complexes, which are present on different T cell subsets. The high-affinity αβγ receptor present primarily on TREGs, and the intermediate-affinity βγ receptor present primarily on CD8+ effector T cells and NK cells. In contrast to wild-type IL-2, XTX202 does not bind the α-subunit of the IL-2 receptor and therefore does not induce the preferential activity on TREGs that limits the immune activating effect of wild type IL-2. XTX202 is designed to potently stimulate CD8+ effector T cells and NK cells that express the βγ receptor. 18 Table of Contents Our Solution: XTX202, a Tumor-Activated IL-2 The critical challenge in the development of IL-2 therapies is to improve patient tolerability without reducing efficacy. Deploying the key structural components of our platform technology, we have designed XTX202 with three key features designed to overcome this: (1) avoidance of binding to CD25, the IL-2α receptor subunit, in order to reduce the activation of Treg cells that inhibit immune response, while maintaining effective activation of CD8+ and NK cells that promote an anti-tumor immune response; (2) overcoming the short circulating half-life of the native cytokine using the half-life extension domain; and (3) a removable protease-cleavable protein mask that prevents XTX202 from binding and signaling until the mask is removed by the MMPs that are preferentially active within the tumor microenvironment. Tumor-Activated Design Components of XTX202 These key features are intended to ensure that XTX202 is released and activated preferentially within the tumor microenvironment, where it has been designed to bind to lymphocytes. In the tumor microenvironment, XTX202 is designed to be unmasked and to bind to the IL-2 βγ receptors that are abundantly expressed on CD8+ effector T cells and NK cells, activating these cells. Locally activated T cells and NK cells have potent anti-tumor cytotoxic activity. The unmasked XTX202 is then rapidly internalized by these lymphocytes, shortening the systemic half-life of the active (unmasked) molecule and localizing its activity to the tumor. Initial Phase 1/2 Monotherapy Data Presented at Society for Immunotherapy of Cancer (SITC) 38 th Annual Meeting in November 2023 In November 2023, we reported initial Phase 1/2 monotherapy data for XTX202 at the SITC Annual Meeting. As of a data cutoff date of October 26, 2023, 62 patients with advanced solid tumors had been administered XTX202 in an outpatient setting. Fifty-four patients were treated in Phase 1 monotherapy dose-escalation and dose-expansion at seven dose levels ranging from 0.27 mg/kg to 4 mg/kg administered on a Q3W dosing schedule. Eight patients were treated in Phase 2 monotherapy at a dose level of 1.4 mg/kg Q3W. Patients enrolled in Phase 1 were heavily pre-treated, with 74% of patients previously treated with three or more lines of anti-cancer therapy and 69% of patients previously treated with an immunotherapy. All patients in Phase 2 had been previously treated with an immunotherapy. As of the data cutoff date, 20 patients were continuing treatment with XTX202 across the Phase 1/2 trial. 19 Table of Contents Preliminary Safety Data Across all dose levels administered in the Phase 1/2 trial, 62 patients were evaluable for safety. ● No signs or symptoms of vascular leak syndrome were reported by investigators through the 4.0 mg/kg dose. ● XTX202 was generally well-tolerated. Treatment-related adverse events, or TRAE, were primarily Grade 1 or 2, and no patients discontinued treatment due to a TRAE. Higher grade TRAEs were primarily asymptomatic laboratory abnormalities, and no Grade 5 TRAEs were reported by investigators. ● The most common TRAEs (≥10% incidence) of any grade reported by investigators across all dose levels were: fatigue (19%, no grade ≥3); pyrexia (18%, no grade ≥3); chills (16%, 2% grade 3); and lymphocyte count decreased (15%, 8% grade 3-4). Grade 3 TRAEs reported in one patient each (2%) were: diarrhea/colitis; myalgia; hypoxia; lymphopenia; and aspartate transferase, or AST/alanine transaminase, or ALT, increased. Investigators reported two Grade 4 TRAEs of lymphocyte count decreased/lymphopenia, which were both transient (<3 days) and resolved without intervention, with both patients able to continue on treatment. ● Across all dose levels, only two patients (3%) had a dose reduction due to a TRAE, and only one dose-limiting toxicity was observed, which was a reversible and transient (<5 days) Grade 3 elevation of AST and ALT at the 1 mg/kg dose. Preliminary Anti-Tumor Activity Across all dose levels administered in the Phase 1/2 trial, 42 patients were evaluable for anti-tumor activity. Of these response-evaluable patients, 27 patients were treated at dose levels of 1.4 mg/kg or higher, including six patients treated at the 2.8 mg/kg dose level or higher. ● Data demonstrated evidence of a dose-dependent increase in disease control rate, or DCR. Among the 42 response-evaluable patients treated across all dose levels, investigators reported stable disease, or SD, of at least 9-weeks duration in 13 patients (31% DCR) across a range of solid tumors, including cold tumors: melanoma (n=3); RCC (n=2); NSCLC (n=2); CRC (n=2); and myoepithelial carcinoma, vaginal cancer, testicular cancer and squamous penile cancer (n=1 each). Among the six response-evaluable patients treated at the 2.8 mg/kg dose level or higher, investigators reported SD of at least 9-weeks duration in three patients (50% DCR). ● In addition, two patients were ongoing on treatment for more than one year as of the data cutoff date, including a treatment-refractory MSS CRC patient and an RCC patient, suggesting XTX202 was well-tolerated with repeated, long-term dosing in these patients. Preliminary PK and PD Data Preliminary PK analysis demonstrated limited XTX202 activation in peripheral circulation, including: ● Dose-proportional exposure for XTX202 with minimal levels of unmasked XTX202 detected in peripheral circulation that were consistent across dose levels. ● Approximately 15% activated XTX202 in the tumor based on an analysis of an on-treatment patient biopsy for a patient treated with XTX202 at the 2.8 mg/kg dose level as compared to <1% activated XTX202 in plasma across patients treated with XTX202 at the 2.8 mg/kg dose level for whom PK analysis was available. These data along with non-clinical pharmacology data suggest 2.8 mg/kg or higher monotherapy doses of XTX202 are approaching the optimal range to activate CD8+ effector T cells and NK cells in the tumor. Consistent with IL-2 beta-gamma biology, preliminary PD analysis of four available on-treatment tumor samples showed an average increase >200% of CD8+ effector T cells in the tumor as compared to pre-treatment biopsies. 20 Table of Contents Additional Phase 2 Monotherapy Data Reported in March 2024 In March 2024, we announced additional data from our Phase 2 clinical trial evaluating XTX202 in patients with metastatic RCC or unresectable or metastatic melanoma. As of a data cutoff date of March 6, 2024: ​ ● A total of 17 RCC patients and 20 melanoma patients were administered XTX202 in the Phase 2 trial in an outpatient setting at dose levels of 1.4 mg/kg Q3W or 4 mg/kg Q3W. ● In 26 patients evaluable for anti-tumor activity in the Phase 2 trial, SD continued to be the best response. Investigators reported SD of at least nine-weeks duration in seven RCC patients (70% disease control rate) and in nine melanoma patients (56% disease control rate). In addition, XTX202 continued to be generally well-tolerated with safety data consistent with previously reported results. We plan to present the full data set at a future medical meeting. Together with previously reported data, we believe these additional data further validate our tumor-activated approach and support the broad potential for XTX202 as a combination therapy. We plan to explore strategic opportunities to continue to develop XTX202 in combination with other agents. As part of a strategic portfolio reprioritization announced in March 2024, we plan to discontinue further investment in XTX202 as a monotherapy. ​ Future Opportunities Leveraging Our Proprietary Platform for Tumor-Activated Bispecific Molecules and Immune Cell Engager Molecules (Including Tumor-Activated Cell Engagers and Tumor-Activated Effector-Enhanced Cell Engagers) To date, we have prioritized efforts to develop XTX101 (anti-CTLA-4), XTX301 (IL-12) and XTX202 (IL-2) based on the therapeutic activity established in other clinical trials, while recognizing that the benefits of anti-CTLA-4, IL-12 and IL2 have been historically hampered by issues of significant toxicity, poor bioavailability and, in the case of cytokines like IL-12 and IL-2, a short half-life. By leveraging the insights and capabilities of our proprietary platform and building on our unique expertise in masking antibodies as well as cytokines, we are focusing our differentiated research platform on developing tumor-activated bispecific molecules and immune cell engager molecules (including tumor-activated cell engagers and tumor-activated effector-enhanced cell engagers). Subject to obtaining sufficient additional capital, we plan to advance XTX501, our tumor-activated PD-1/IL-2 bispecific development candidate, into IND-enabling studies. We also plan to continue to make focused investments in our promising research-stage pipeline for additional tumor-activated bispecific molecules and immune cell engager molecules (including tumor-activated cell engagers and tumor-activated effector-enhanced cell engagers). We will continue to evaluate opportunities for better tolerated and more efficacious combination therapies, using product candidates from across our portfolio with other cancer therapies, to increase the potential for curative regimens in oncology. Competition We believe our novel and proprietary platform technology and masking approach represent a meaningful competitive advantage in seeking to develop novel and highly effective treatments for cancer. However, the biotechnology and biopharmaceutical industries are characterized by rapid evolution of technologies and sharp competition and emphasis on intellectual property. Any product candidates that we successfully develop and commercialize will have to compete with existing therapies and new therapies that may become available in the future. While we believe that our technology, development experience and scientific knowledge provide us with competitive advantages, we face potential competition from many different sources, including major pharmaceutical, specialty pharmaceutical and biotechnology companies, academic institutions, governmental agencies and public and private research institutions. Some of our competitors, either independently or with strategic partners, have substantially greater financial, technical and human resources than we do. In addition, our competitors may be more successful than we are in research and development, manufacturing, preclinical testing, conducting clinical trials, obtaining regulatory approval for treatments and achieving widespread market acceptance. Merger and acquisition activity in the biotechnology and biopharmaceutical industries may result in resources being concentrated among a smaller number of our competitors. These companies also compete with 21 Table of Contents us in recruiting and retaining qualified scientific and management personnel, establishing clinical trial sites and patient registration for clinical trials and acquiring technologies complementary to, or necessary for, our programs. Smaller or early-stage companies may also prove to be significant competitors, particularly through collaborative arrangements with large and established companies. In addition to competitors specifically targeting anti-CTLA-4, IL-12 and IL-2, we also face competition more broadly across the oncology market. 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. Beyond these treatments, we may also be subject to competition from additional modalities, including oncolytic viruses and cancer vaccines. Our commercial opportunity could be substantially limited if our competitors develop and commercialize products that are more effective, safer, less toxic, more convenient, or less expensive than products we may develop. In geographies that are critical to our commercial success, competitors may also obtain regulatory approvals before us, resulting in our competitors building a strong market position in advance of the entry of our products. In addition, our ability to compete may be affected in many cases by insurers or other third-party payers seeking to encourage the use of other drugs. The key competitive factors affecting the success of any products we may develop are likely to be their efficacy, safety, convenience, price and availability of reimbursement. Tumor-Activated Anti-CTLA-4 Program We are aware of a number of companies that are developing anti-CTLA-4 therapies as immunotherapies. With respect to XTX101, if approved, we may face competition from other anti-CTLA-4 based therapies. For example, Yervoy (ipilimumab), an anti-CTLA-4, is approved to treat melanoma, RCC, NSCLC and certain cancers of the large intestine, and Imjudo (tremelimumab) is approved as a combination therapy to treat unresectable hepatocellular carcinoma. In addition, we are aware that several companies have anti-CTLA-4 programs in development, including Adagene, Inc., Agenus Inc., AstraZeneca plc, BioAtla, Inc., CytomX Therapeutics, Inc., MacroGenics, Inc. and OncoC4, Inc. Tumor Activated Cytokine Programs With respect to XTX301, there are no approved IL-12 therapies currently on the market for the treatment of cancer; however, we are aware of several other companies that have modified IL-12 or intra-tumoral IL-12 delivery programs for the treatment of cancer in development, including Amunix Pharmaceuticals, Inc., AstraZeneca plc / Moderna, Inc., Cullinan Management Inc., Dragonfly Therapeutics, Inc., ImmunityBio, Inc., PDS Biotechnology Corporation, Philogen S.p.A., Sonnet BioTherapeutics, Werewolf Therapeutics, Inc., Xencor Inc. and Zymeworks Inc. With respect to XTX202, if approved, it may face competition from other IL-2 based cancer therapies. For example, Proleukin (aldesleukin), a human recombinant interleukin-2 product, is approved and marketed for the treatment of metastatic RCC and melanoma. In addition, we are aware that a number of other companies have modified or low-dose IL-2 programs in development for the treatment of cancer, including Alkermes plc, Anaveon AG, Ascendis Pharma A/S, Asher Biotherapeutics, Inc., Aulos Bioscience, Inc., Bright Peak Therapeutics, Cue Biopharma, Inc., Cugene Inc., Cullinan Management Inc., Egle Therapeutics SAS, GI Innovation, Iovance Biotherapeutics, Inc., Kymab Ltd., Medicenna Therapeutics Corp., Medikine, Inc., Modulate Therapeutics, Inc., Neoleukin Therapeutics, Inc., Philogen S.p.A., Proviva Therapeutics, Inc., Roche AG, Sanofi, Selecxine, Synthekine, Inc., Trutino Biosciences Inc., Werewolf Therapeutics, Inc., XOMA Corporation and Zydus Cadila. Intellectual Property We strive to protect our proprietary technology, inventions, improvements, and platforms, including composition of matter for product candidates, methods of use and processes for their manufacture that we believe are important to our business, including by obtaining, maintaining, defending and enforcing patent and other intellectual property rights for the foregoing in the United States and in certain foreign jurisdictions. We also rely on trade secrets and confidentiality agreements to 22 Table of Contents protect our confidential information and know-how and other aspects of our business that are not amenable to, or that we do not consider appropriate for, patent protection. Our success depends in part on our ability to: ● obtain, maintain, enforce and defend patent and other intellectual property rights for our commercially important technology, inventions and improvements; ● preserve the confidentiality of our trade secrets and other confidential information; ● obtain and maintain licenses to use and exploit intellectual property owned or controlled by third parties; ● operate without infringing, misappropriating or otherwise violating any valid and enforceable patents and other intellectual property rights of third parties; and ● defend against challenges and assertions by third parties challenging the validity or enforceability of our intellectual property rights, or our rights in our intellectual property, or asserting that the operation of our business infringes, misappropriates or otherwise violates their intellectual property rights. Patent portfolio As of March 31, 2024, we own, co-own or exclusively license 18 patent application families related to our business, including four pending Patent Cooperation Treaty, or PCT, patent applications, 14 pending U.S. non-provisional applications, seven issued U.S. patents, 19 issued patents in Armenia, Azerbaijan, Belarus, China, India, Indonesia, Japan, Kazakhstan, Kyrgyzstan, Malaysia, Mexico, South Korea, Russia, Saudi Arabia, Taiwan, Tajikistan, and Turkmenistan and 169 pending foreign applications in Australia, Brazil, Canada, China, Eurasia, Europe, Hong Kong, Indonesia, Israel, India, Japan, South Korea, Mexico, Malaysia, New Zealand, the Philippines, Saudi Arabia, Singapore, South Africa and Taiwan. In addition, we own four U.S. provisional patent applications within the priority year. Our owned, co-owned or exclusively in-licensed patent applications cover various aspects of our programs and technology, including composition of matter and method of use as further described below. Any U.S. or foreign patents issued from national stage filings of our owned, co-owned, or exclusively in-licensed PCT patent applications and any U.S. patents issued from non-provisional applications we may file in connection with our provisional patent applications will have a statutory expiration date ranging between 2037 and 2045, without taking into account any possible patent term adjustments or extensions and assuming payment of all appropriate maintenance, renewal, annuity and other governmental fees. Xilio’s Platform for Tumor-Activated I-O Molecules Our proprietary engineering platform technology enables tumor-activated I-O molecules that can effect tumor-activated immunotherapy while minimizing systemic toxicity. By masking biological agents such as cytokines, antibodies and multi-functional molecules, our platform technology can be used to decouple therapeutic effects from toxicity for treating different cancers. As of March 31, 2024, we own four patent families covering the platform in the cytokine space: a first patent family, including one pending U.S. patent application and corresponding foreign applications in Australia, Brazil, Canada, China, Eurasia, Europe, Hong Kong, Indonesia, Israel, India, South Korea, Mexico, Malaysia, New Zealand, the Philippines, Saudi Arabia, Singapore and South Africa; and three additional patent families covering our multi-functional, including bispecific, platform technology in the cytokine space, include two pending U.S. and Taiwan applications, two pending PCT applications, and one provisional application within the priority year. We exclusively license two patent families relating to the platform technology and our cytokine and antibody programs. One of the two patent families is exclusively in-licensed in the oncology field from AskGene Pharma, Inc., or AskGene, and covers certain aspects of the platform technology for cytokines. These owned and exclusively licensed patent families will have a statutory expiration date ranging between 2039 and 2041, without taking into account any possible patent term adjustments or extensions and assuming payment of all appropriate maintenance, renewal, annuity and other governmental fees. 23 Table of Contents In addition, we own two patent families covering various linker designs that are used or can be used in our technology, including one pending PCT application, and pending patent applications in the United States, Canada, Europe, Japan, South Korea and Taiwan. Cytokine Programs Our cytokine pipeline includes our clinical-stage, tumor-activated product candidates, XTX202 (IL-2) and XTX301 (IL-12), and our preclinical bispecific product candidate XTX501 (PD-1/IL-2). ● IL-12 Program. As of March 31, 2024, we own two patent families directed to different masked IL-12 constructs and sequences, including XTX301, with composition of matter and methods of use claims. These patent families include one issued U.S. patent, one pending U.S. application, and corresponding foreign applications in Australia, Brazil, Canada, China, Eurasia, Europe, Indonesia, Israel, India, Japan, South Korea, Mexico, Malaysia, New Zealand, Philippines, Saudi Arabia, Singapore, South Africa and Taiwan. These patent families will have a statutory expiration date in 2039 and 2041, without taking into account any possible patent term adjustments or extensions and assuming payment of all appropriate maintenance, renewal, annuity and other governmental fees. ● IL-2 Program. As of March 31, 2024, we own two patent families relating to masked IL-2 cytokines, including XTX202, and seven families related to multi-functional, including bispecific, IL-2 cytokines, including XTX501, with composition of matter and methods of use claims. The masked IL-2 cytokine patent families include one pending U.S. application, five issued U.S. patents, one issued patent in India and corresponding foreign applications pending in Australia, Brazil, Canada, China, Eurasia, Europe, Hong Kong, Indonesia, Israel, India, Japan, South Korea, Mexico, Malaysia, New Zealand, Philippines, Saudi Arabia, Singapore, South Africa and Taiwan. The multi-functional/bispecific IL-2 cytokine patent families include three pending PCT applications and four provisional applications within the priority year. The patent family exclusively in-licensed in the oncology field from AskGene also relates to the IL-2 program. These owned and exclusively in-licensed patent families will have a statutory expiration date ranging between 2039 and 2045, without taking into account any possible patent term adjustments or extensions and assuming payment of all appropriate maintenance, renewal, annuity and other governmental fees. Antibody Program As of March 31, 2024, we own, co-own or exclusively in-license three patent families relating to masked anti-CTLA-4 antibody constructs and sequences, including XTX101, with composition of matter and methods of use claims. A first patent family is exclusively in-licensed from WuXi Biologics (Shanghai) Co., Ltd. and directed to anti-CTLA-4 antibodies. This family includes two issued U.S. patents covering certain complementarity-determining regions and variable region sequences of anti-CTLA-4 antibodies, including XTX101. Corresponding foreign applications are issued in Armenia, Azerbaijan, Belarus, China, Indonesia, Japan, Kazakhstan, Kyrgyzstan, Malaysia, Mexico, Russia, South Korea, Saudi Arabia, Taiwan, Tajikistan, and Turkmenistan and pending in Australia, Brazil, Canada, China, European Patent Office, Hong Kong, India, Indonesia, Israel, Japan, South Korea, Mexico, New Zealand, Philippines, Singapore, South Africa and Taiwan. A second patent family is owned and directed to anti-CTLA-4 antibodies with modifications that improve antibody-dependent cellular cytotoxicity and includes one pending U.S. application. Corresponding foreign applications are pending in Australia, Brazil, Canada, China, Eurasia, Europe, Hong Kong, India, Indonesia, Israel, Japan, South Korea, Mexico, Malaysia, New Zealand, Philippines, Saudi Arabia, Singapore, and South Africa. A third patent family is co-owned and directed to masked anti-CTLA-4 antibodies, which includes one pending U.S. application. Corresponding foreign applications are pending in Australia, Brazil, Canada, Eurasia, Europe, Hong Kong, India, Indonesia, Israel, Japan, South Korea, Mexico, Malaysia, New Zealand, Philippines, Saudi Arabia, Singapore, South Africa and Taiwan. In addition, we own two patent applications directed to combination therapies using masked or unmasked anti-CTLA-4 antibodies, including XTX101 and PD-1/PD-L1 antibodies. These families include two pending U.S. applications. Corresponding foreign applications are pending in Australia, Canada, Eurasia, Europe, Japan, South Africa and Taiwan. These owned, co-owned and licensed patent families will have a statutory expiration date ranging between 2037 and 2042, without taking into account any possible patent term adjustments or extensions and assuming payment of all appropriate maintenance, renewal, annuity and other governmental fees. 24 Table of Contents Trademark portfolio As of March 15, 2024, we own two federal trademark registrations for XILIO and XILIO THERAPEUTICS (Class 42) in the United States and a pending federal trademark application for XILIO (Class 5) in the United States that has been approved and published for opposition. Patent prosecution A PCT patent application is not eligible to become an issued patent until, among other things, we file one or more national stage patent applications within 30 months, 31 months or 32 months of the PCT application’s priority date, depending on the jurisdiction, in the countries in which we seek patent protection. If we do not timely file any national stage patent applications, we may lose our priority date with respect to our PCT patent application and any potential patent protection on the inventions disclosed in such PCT patent application. Moreover, a provisional patent application is not eligible to become an issued patent. A provisional patent application may serve as a priority filing for a non-provisional patent application, we file within 12 months of such provisional patent application. If we do not timely file non-provisional patent applications, we may lose our priority date with respect to our existing provisional patent applications and any potential patent protection on the inventions disclosed in our provisional patent applications. While we intend to timely file additional provisional patent applications and national stage and non-provisional patent applications relating to our PCT patent applications, we cannot predict whether any of our patent applications will result in the issuance of patents. If we do not successfully obtain patent protection, or if the scope of the patent protection we or our licensors obtain with respect to our product candidates, platform or technology is not sufficiently broad, we will be unable to prevent others from using our technology or from developing or commercializing technology and products similar or identical to ours or other similar competing products and technologies. Our ability to stop third parties from making, using, selling, offering to sell, importing or otherwise commercializing any of our technology, inventions and improvements, either directly or indirectly, will depend in part on our success in obtaining, maintaining, defending and enforcing patent claims that cover our technology, inventions and improvements. The patent positions of companies like ours are generally uncertain and involve complex legal and factual questions. The protection afforded by a patent varies on a product-by-product basis, from jurisdiction-to-jurisdiction, and depends upon many factors, including the type of patent, the scope of its coverage, the availability of patent term adjustments and regulatory-related patent term extensions, the availability of legal remedies in a particular jurisdiction and the validity and enforceability of the patent. Moreover, patent laws and related enforcement in various jurisdictions outside of the United States are uncertain and may not protect our rights to the same extent as the laws of the United States. Changes in the patent laws and rules, whether by legislation, judicial decisions or regulatory interpretation, in the United States and other jurisdictions may diminish our ability to protect our inventions and obtain, maintain, defend and enforce our patent rights, and could therefore affect the value of our business. The area of patent and other intellectual property rights in biotechnology is evolving and has many risks and uncertainties, and third parties may have blocking patents and other intellectual property that could be used to prevent us from commercializing our platforms and product candidates and practicing our proprietary technology. Our patent rights may be challenged, narrowed, circumvented, invalidated or ruled unenforceable, which could limit our ability to stop third parties from marketing and commercializing related platforms or product candidates or limit the term of patents that cover our platforms and product candidates. In addition, the rights granted under any issued patents may not provide us with protection or competitive advantages against third parties with similar technology, and third parties may independently develop similar technologies. Moreover, because of the extensive time required for development, testing and regulatory review of a potential product, it is possible that before any of our product candidates can be commercialized, any related patent may expire or remain in force for only a short period following commercialization, thereby reducing any competitive advantage provided by the patent. For this and other risks related to our proprietary technology, inventions, improvements, platforms and product candidates and intellectual property rights related to the foregoing, please see the section entitled “Risk Factors—Risks Related to our Intellectual Property.” 25 Table of Contents Patent term extensions The term of individual patents depends upon the laws of the jurisdictions in which they are obtained. In most jurisdictions in which we file, the patent term is 20 years from the earliest date of filing of the first non-provisional patent application to which the patent claims priority. However, the term of U.S. patents may be extended or adjusted for delays incurred due to compliance with FDA requirements or by delays encountered during prosecution that are caused by the U.S. Patent and Trademark Office, or the USPTO. For example, in the United States, a patent claiming a new biologic product, its method of use or its method of manufacture may be eligible for a limited patent term extension under the Drug Price Competition and Patent Term Restoration Act of 1984, or the Hatch-Waxman Act, for up to five years beyond the normal expiration date of the patent. Patent term restoration cannot be used to extend the remaining term of a patent past a total of 14 years from the product’s approval date in the United States. Only one patent applicable to an approved product is eligible for the extension, and the application for the extension must be submitted prior to the expiration of the patent for which extension is sought. A patent that covers multiple products for which approval is sought can only be extended in connection with one of the approvals. For more information on patent term extensions, see “Business—Government Regulation and Product Approval—Patent Term Restoration and Extension.” In the future, if and when any product candidates we may develop receive FDA approval, we expect to apply for patent term extensions on issued patents covering those product candidates. Moreover, we intend to seek patent term adjustments and extensions for any of our issued patents in any jurisdiction where such adjustments and extensions are available. However, there is no guarantee that the applicable authorities, including the USPTO and FDA, will agree with our assessment of whether such adjustments and extensions should be granted, and even if granted, the length of such adjustments and extensions. Trade secrets In addition to patent protection, we also rely on trade secrets, know-how, unpatented technology and other proprietary information to strengthen our competitive position. We take steps to protect and preserve our trade secrets and other confidential and proprietary information and prevent the unauthorized disclosure of the foregoing, including by entering into non-disclosure and invention assignment agreements with parties who have access to our trade secrets or other confidential and proprietary information, such as employees, consultants, outside scientific collaborators, contract research and manufacturing organizations, sponsored researchers and other advisors, at the commencement of their employment, consulting or other relationships with us. In addition, we take other appropriate precautions, such as maintaining physical security of our premises and physical and electronic security of our information technology systems, to guard against any misappropriation or unauthorized disclosure of our trade secrets and other confidential and proprietary information by third parties. Despite these efforts, third parties may independently develop substantially equivalent proprietary information and techniques or otherwise gain access to our trade secrets or other confidential or proprietary information. In addition, we cannot provide any assurances that all of the foregoing non-disclosure and invention assignment agreements have been duly executed, and any of the counterparties to such agreements may breach them and disclose our trade secrets and other confidential and proprietary information. Although we have confidence in the measures we take to protect and preserve our trade secrets and other confidential and proprietary information, they may be inadequate, our agreements or security measures may be breached, and we may not have adequate remedies for such breaches. Moreover, to the extent that our employees, contractors, consultants, collaborators and advisors use intellectual property owned by others in their work for us, disputes may arise as to our rights in any know-how or inventions arising out of such work. For more information, please see the section entitled “Risk Factors—Risks Related to our Intellectual Property.” License and Collaboration Agreements Exclusive License Agreement with Gilead In March 2024, Xilio Development entered into an exclusive license agreement with Gilead pursuant to which it granted Gilead an exclusive global license to develop and commercialize our clinical-stage product candidate XTX301, a tumor-activated IL-12, and specified other molecules directed to IL-12. 26 Table of Contents Xilio Development will be responsible for conducting clinical development for XTX301 in the ongoing Phase 1 clinical trial through an initial planned Phase 2 dose expansion. Following the delivery by Xilio Development of a specified clinical data package for XTX301 related to the Phase 1 clinical trial and planned Phase 2 clinical trial, Gilead can elect to transition responsibilities for the development and commercialization of XTX301 to Gilead, subject to the terms of the agreement and payment by Gilead of a $75.0 million transition fee. Under the license agreement, we are eligible to receive approximately $43.5 million in upfront payments, including a cash payment of $30.0 million and an initial equity investment by Gilead of approximately $13.5 million of our common stock at a purchase price of $1.97 per share. The initial equity investment closed on March 28, 2024, and the $30.0 million upfront cash payment is payable by Gilead within a specified time period promptly following signing of the license agreement. We are eligible to receive up to $604.0 million in additional contingent payments, which include (i) the proceeds from up to three additional private placements of common stock, (ii) the $75.0 million transition fee and (iii) specified development, regulatory and sales-based milestones. Prior to the potential transition fee, up to $29.0 million of the total contingent payments are related to the potential additional private placements of common stock and a near-term development milestone. In addition, we are eligible to receive tiered royalties ranging from high single digits to mid-teens on annual global net product sales. Unless earlier terminated in accordance with its terms, the license agreement will expire upon expiration of the last royalty term for the last licensed product. Gilead may terminate the license agreement for convenience upon specified time periods. If Gilead elects not to transition responsibilities for development and commercialization of the licensed products and pay the transition fee, then the license agreement will automatically terminate. Either party may terminate the license agreement for the other party’s uncured material breach or insolvency. Subject to the terms of the license agreement, effective upon termination of the license agreement, the licenses to Gilead terminate and Xilio Development is entitled to continue to exploit the licensed products. During the term of the license agreement, Xilio Development and its affiliates have agreed not to directly or indirectly conduct specified development, manufacturing or commercialization activities with respect to any molecule that contains, comprises or incorporates IL-12, except for the performance of Xilio Development’s activities under and in accordance with the license agreement. In connection with the execution of the license agreement, on March 27, 2024, we entered into a stock purchase agreement with Gilead. In addition to the initial equity investment by Gilead of approximately $13.5 million of our common stock, through March 27, 2025, we may, at our election and subject to the terms and conditions of the stock purchase agreement, cause Gilead to purchase up to approximately $11.5 million of additional shares of common stock (including, at Gilead’s sole election, prefunded warrants in lieu of shares of common stock) in up to three additional private placements at a predetermined price per share specified therein, at all times subject to Gilead not being deemed the beneficial owner of greater than 19.9% of our common stock upon the closing of the applicable additional private placement with Gilead. If Gilead elects to purchase prefunded warrants, each prefunded warrant will have an exercise price of $0.0001 per share of common stock, be immediately exercisable and remain exercisable until exercised in full. Gilead may not exercise its prefunded warrants to the extent that it would beneficially own more than 19.99% of the number of shares of common stock outstanding immediately after giving effect to such exercise. Any prefunded warrants that may be issued to Gilead in an additional private placement with Gilead will be in substantially the same form as the prefunded warrants issued to investors in the March 2024 private placement. In-License Agreements We are a party to license agreements under which we license patents, patent applications and other intellectual property from third parties. These licenses impose various diligence and financial payment obligations on us. We expect to continue to enter into these types of license agreements in the future. We consider the following license agreements to be material to our business. 27 Table of Contents Cross-License Agreement with AskGene In December 2020, Xilio Development entered into a cross-license agreement with AskGene Pharma, Inc., or AskGene, pursuant to which AskGene granted us certain exclusive licenses for AskGene patent rights related to non-antigen binding IL-2 products in the field of oncology and certain co-exclusive licenses for AskGene patent rights related to antigen binding IL-2 products in all fields. Under the agreement, AskGene retains rights to the AskGene patent rights in Singapore, Thailand, Malaysia, Vietnam, the People’s Republic of China, Taiwan, Macau, Hong Kong, Korea and India, which we refer to as the AskGene territory, and granted licenses to us for the AskGene patent rights worldwide, excluding the AskGene territory, which we refer to as the Xilio territory. Under the agreement, we paid AskGene an upfront payment of $6.0 million, and for any licensed IL-2 product, we are obligated to pay AskGene up to $13.0 million in the aggregate upon the achievement of specified regulatory milestones. In addition, subject to specified conditions, for any IL-2 licensed product, we are obligated to pay AskGene percentage royalties in the mid-single digits on aggregate annual net sales of IL-2 licensed products in the Xilio territory during the applicable royalty term. In addition, we granted a non-exclusive, royalty-free, non-transferable, worldwide license to AskGene for specified Xilio patent rights related to non-antigen binding IL-2 products in the field of immunology and for specified Xilio patent rights related to antigen binding IL-2 products in all fields. Subject to the terms of the agreement and during the time period specified, we also granted AskGene an option to obtain a license in the AskGene territory to develop and commercialize our IL-2 licensed products. If AskGene exercises its option to develop and commercialize our IL-2 licensed products in the AskGene territory, then the parties will negotiate and enter into a license agreement for AskGene’s exclusive development and commercialization of such products in the AskGene territory, and AskGene would be obligated to pay us percentage royalties in the mid-single digits on aggregate annual net sales of such licensed products in the AskGene territory. During the term of the agreement, AskGene has agreed not to exploit any non-antigen binding IL-2 product comprised of specified masking technology in the field of oncology in the Xilio territory. Subject to the terms of the agreement, each party’s obligation to make royalty payments is subject to adjustment in specified circumstances and extends with respect to a licensed product in a country upon the first commercial sale of such licensed product in such country and ending upon the latest of (i) the expiration of the last valid claim of any licensed patent rights in such country that cover such licensed product, (ii) the expiration of regulatory exclusivity, if any, for such licensed product in such country, and (iii) for a specified time period following first commercial sale of such licensed product in such country. The agreement continues on a product-by-product and country-by-country basis until the expiration of the applicable royalty term in each country, at which time the agreement expires with respect to such product in such country, and the licensed party receives a perpetual, irrevocable, fully-paid and royalty-free license to the licensed patent rights in such country. Either party has the right to terminate the agreement if the other party materially breaches the agreement and fails to cure such breach within specified cure periods or in the event the other party becomes insolvent or files for bankruptcy. Upon any termination, other than the expiration of the agreement with respect to a particular product in a particular country, the licenses granted by each party will terminate and neither party will have the right to practice the other party’s patent rights. Amended and Restated Exclusive License Agreement with City of Hope In August 2016, Xilio Development entered into an amended and restated exclusive license agreement with City of Hope pursuant to which City of Hope granted us an exclusive worldwide license to specified patent rights related to our anti-CTLA-4 monoclonal antibody program. For the first three licensed products or licensed services to achieve specified development and regulatory milestones, we are obligated to pay City of Hope up to $10.3 million in the aggregate per licensed product or licensed service. Subject to specified conditions, we are obligated to pay City of Hope tiered royalties in the low single digits on aggregate annual net 28 Table of Contents sales of licensed products or licensed services on a country-by-country basis until the expiration of the last-to-expire patent or patent application licensed from City of Hope covering the applicable licensed product or licensed service in such country. We are also obligated to pay City of Hope a portion of any consideration we receive for the grant of sublicenses under the agreement ranging from a low to mid double-digit percentage of such consideration, subject to specified conditions under that agreement at the time that we grant any such sublicense. In addition, we paid $0.5 million to City of Hope in connection with the closing of our initial public offering. The agreement continues on a country-by-country basis until the expiration of the last to expire licensed patent right in such country. We have the right to terminate the agreement for convenience at any time on 30 days’ prior written notice to City of Hope. Either party has the right to terminate the agreement if the other party materially breaches the agreement and fails to cure such breach within specified cure periods. City of Hope may terminate the agreement if we or any of our affiliates or sublicensees bring specified patent challenges with respect to the licensed patents against City of Hope or if we assist others in bringing a patent challenge against City of Hope. However, instead of terminating as a result of a patent challenge, City of Hope may elect to increase our payment obligations by a specified percentage amount retroactive to the commencement of such patent challenge. CTLA-4 Monoclonal Antibody License Agreement with WuXi Biologics In September 2016, we entered into a license agreement with WuXi Biologics (Hong Kong) Limited, or WuXi Biologics, as amended in December 2017, pursuant to which WuXi Biologics granted us an exclusive worldwide license, including the rights to grant sublicenses through multiple tiers, to specified monoclonal antibodies and patent rights and know-how controlled by WuXi Biologics, including certain patent rights related to our anti-CTLA-4 mAb program. For each product that incorporates a licensed antibody that has been modified using the rights licensed under the agreement, we are obligated to pay WuXi Biologics up to approximately $25.8 million in the aggregate for specified development and regulatory milestones. In addition, subject to specified conditions, we are obligated to pay WuXi Biologics tiered royalties in the low to mid-single digits on aggregate annual worldwide net sales of licensed products during the applicable royalty term and subject to early expiration or adjustment in specified circumstances. Our obligation to make royalty payments extends with respect to a licensed product in a country until the later of the expiration of the last-to-expire patent or patent application licensed from WuXi Biologics covering the applicable licensed product in such country or for a specified time period following the first commercial sale of such licensed product. Subject to specified conditions under the agreement, we also have certain obligations to contract with WuXi Biologics for specified services related to the development or manufacture of licensed products. Unless terminated earlier in accordance with its terms, the agreement will continue until the expiration of the last to expire royalty term for a licensed product. We have the right to terminate the agreement for convenience at any time upon at least 90 days’ prior written notice to WuXi Biologics. Either party may terminate the agreement for the other party’s uncured material breach. Other than following our termination for convenience or termination by WuXi Biologics for our material breach, upon the expiration of the applicable royalty term for a licensed product in a country, we will receive a paid-up and royalty free license to exploit such licensed product in such country. Manufacturing We currently contract with a third-party contract development and manufacturing organization, or CDMO, to manufacture our product candidates for preclinical studies and our ongoing clinical trials, and we intend to continue to do so with one or more third parties for future preclinical studies and clinical trials. We do not own or operate manufacturing facilities for the production of our product candidates, and we currently do not have plans to build our own clinical or commercial scale manufacturing capabilities. To date, our CDMO has met our production requirements. Our CDMO is under contract to provide clinical material meeting FDA current good manufacturing practice, or cGMP, requirements and in sufficient quantities to meet anticipated clinical-trial demands. To meet our projected needs for commercial manufacturing, our current third-party manufacturer will need to increase its scale of production, or we will need to secure one or more alternate suppliers. We believe that there are alternate manufacturers that could satisfy our anticipated clinical and commercial requirements, although we cannot be certain that identifying and establishing relationships with such manufacturers, if necessary, would not result in significant delay or material additional costs. 29 Table of Contents Although we expect to rely on one or more third-party contract manufacturers for the production of our current and future product candidates, we have personnel with extensive technical, manufacturing, analytical and quality experience in biotherapeutic protein manufacturing to oversee our contract manufacturer relationships. In collaboration with our third-party manufacturer, we have manufactured cGMP clinical supply for our clinical trials for our tumor-activated, clinical-stage product candidates, XTX101 (anti-CTLA-4), XTX301 (IL-12), and XTX202 (IL-2). As we scale clinical and develop commercial manufacturing capability for each of our product candidates, we intend to develop the network of contract manufacturing sites operated by our CDMO to include EU- or U.S.-based sites. Government Regulation and Product Approval Government authorities in the United States, at the federal, state and local level, and in other countries and foreign jurisdictions, including the European Union, or EU, extensively regulate, among other things, the research, development, testing, manufacture, quality control, approval, packaging, storage, recordkeeping, labeling, advertising, promotion, distribution, marketing, sales, pricing, reimbursement, post-approval monitoring and reporting, and import and export of pharmaceutical products. The processes for obtaining regulatory approvals in the United States and in foreign countries and jurisdictions, along with subsequent compliance with applicable statutes and regulations and other regulatory authorities, require the expenditure of substantial time and financial resources. Review and Approval of Drugs and Biologics in the United States In the United States, the FDA approves and regulates drugs under the Federal Food, Drug, and Cosmetic Act, or FDCA, and related regulations. Biological products, or biologics, are licensed for marketing under the Public Health Service Act, or PHSA, and subject to regulation under the FDCA and related regulations. A company, institution, or organization that takes responsibility for the initiation and management of a clinical development program for such products is generally referred to as a sponsor. A sponsor seeking approval to market and distribute a new drug or biological product in the United States must typically secure the following: ● completion of preclinical laboratory tests in compliance with the FDA’s good laboratory practice, or GLP, regulations and standards; ● design of a clinical protocol and submission to the FDA of an investigational new drug application, or IND, which must take effect before human clinical trials may begin; ● approval by an independent institutional review board, or IRB, representing each clinical site before each clinical trial may be initiated; ● performance of adequate and well-controlled human clinical trials in accordance with good clinical practices, or GCPs, to establish the safety and efficacy of the proposed drug product, and with respect to biologics, the purity, potency and safety of such drug product, for each proposed indication; ● submission to the FDA of a new drug application, or NDA, for a drug candidate product and a biologics license application, or BLA, for a biological product requesting marketing for one or more proposed indications; ● review of the request for approval by an FDA advisory committee, where appropriate or if applicable; ● completion of one or more FDA inspections of the manufacturing facility or facilities at which the product, or components thereof, are produced to assess compliance with current good manufacturing practices, or cGMPs, to assure the product’s identity, strength, quality and purity; ● completion of FDA audits of clinical trial sites to assure compliance with GCPs and the integrity of the clinical data; ● payment of user fees and securing FDA approval of the NDA or BLA; and 30 Table of Contents ● compliance with any post-approval requirements, including the potential requirement to implement a Risk Evaluation and Mitigation Strategy, or REMS, and the potential requirement to conduct post-approval studies. Preclinical Studies Before a sponsor begins testing a compound with potential therapeutic value in humans, the product candidate enters the preclinical testing stage. Preclinical studies include laboratory evaluation of the purity and stability of the manufactured substance or active pharmaceutical ingredient and the formulated product, as well as in vitro and animal studies to assess the safety and activity of the product candidate for initial testing in humans and to establish a rationale for therapeutic use. These studies are typically referred to as IND-enabling studies. The conduct of preclinical studies is subject to federal regulations and requirements, including GLP regulations and standards and the U.S. Department of Agriculture’s Animal Welfare Act, if applicable. Some long-term preclinical testing, such as animal tests of reproductive AEs and carcinogenicity, and long-term toxicity studies, may continue after the IND is submitted. The IND and IRB Processes An IND is a request for FDA authorization to administer an investigational product candidate to humans. Such authorization must be secured prior to interstate shipment and administration of any new drug or biologic that is not the subject of an approved NDA or BLA. In support of a request for an IND, sponsors must submit a protocol for each clinical trial and any subsequent protocol amendments must be submitted to the FDA as part of the IND. In addition, the results of the preclinical tests, together with manufacturing information, analytical data, any available clinical data or literature and plans for clinical trials, among other things, are submitted to the FDA as part of an IND. The FDA requires a 30-day waiting period after the filing of each IND before clinical trials may begin. This waiting period is designed to allow the FDA to review the IND to determine whether human research subjects and patients will be exposed to unreasonable health risks or whether there are any issues surrounding chemistry, manufacturing and controls, or CMC, for the proposed product. At any time during this 30-day period, or thereafter, the FDA may raise concerns or questions about the conduct of the trials as outlined in the IND and impose a clinical hold or partial clinical hold. In this case, the IND sponsor and the FDA must resolve any outstanding concerns before clinical trials can begin. The FDA’s primary objectives in reviewing an IND are to assure the safety and rights of patients and to help assure that the quality of the investigation will be adequate to permit an evaluation of the drug’s effectiveness and safety and of the biological product’s safety, purity and potency. Following commencement of a clinical trial under an IND, the FDA may also place a clinical hold or partial clinical hold on that trial. Clinical holds are imposed by the FDA whenever there is concern for patient safety and may be a result of new data, findings, or developments in clinical, nonclinical, and/or CMC. A clinical hold is an order issued by the FDA to the sponsor to delay a proposed clinical investigation or to suspend an ongoing investigation. A partial clinical hold is a delay or suspension of only part of the clinical work requested under the IND. For example, a specific protocol or part of a protocol is not allowed to proceed, while other protocols may do so. No more than 30 days after imposition of a clinical hold or partial clinical hold, the FDA will provide the sponsor a written explanation of the basis for the hold. Following issuance of a clinical hold or partial clinical hold, an investigation may only resume after the FDA has notified the sponsor that the investigation may proceed. The FDA will base that determination on information provided by the sponsor correcting the deficiencies previously cited or otherwise satisfying the FDA that the investigation can proceed. A sponsor may choose, but is not required, to conduct a foreign clinical study under an IND. When a foreign clinical study is conducted under an IND, all IND requirements must be met unless waived. When a foreign clinical study is not conducted under an IND, the sponsor must ensure that the study complies with certain regulatory requirements of the FDA in order to use the study as support for an IND or application for marketing approval in the United States. Specifically, the studies must be conducted in accordance with GCP, including undergoing review and receiving approval by an independent ethics committee, or IEC, and seeking and receiving informed consent from subjects. The FDA’s regulations are intended to help ensure the protection of human subjects enrolled in non-IND foreign clinical studies, as well as the quality and integrity of the resulting data. They further help ensure that non-IND foreign studies are conducted in a manner comparable to that required for IND studies. In addition to the foregoing IND requirements, an IRB representing each institution participating in the clinical trial must review and approve the plan for any clinical trial before it commences at that institution, and the IRB must conduct 31 Table of Contents continuing review and reapprove the trial at least annually. The IRB must review and approve, among other things, the trial protocol and informed consent information to be provided to trial subjects. An IRB must operate in compliance with FDA regulations. An IRB can suspend or terminate approval of a clinical trial at its institution, or an institution it represents, if the clinical trial is not being conducted in accordance with the IRB’s requirements or if the product candidate has been associated with unexpected serious harm to patients. Additionally, some trials are overseen by an independent group of qualified experts organized by the trial sponsor, known as a data monitoring committee, or DMC. This group provides authorization for whether a trial may move forward at designated check points based on access that only the group maintains to available data from the trial. Suspension or termination of development during any phase of clinical trials can occur if it is determined that the participants or patients are being exposed to an unacceptable health risk or for other reasons, including evolving business objectives and/or competitive climate. Human Clinical Studies in Support of an NDA or BLA Clinical trials involve the administration of the investigational product to human subjects under the supervision of qualified investigators in accordance with GCP requirements, which include, among other things, the requirement that all research subjects provide their informed consent in writing before their participation in any clinical trial. Clinical trials are conducted under written trial protocols detailing, among other things, the inclusion and exclusion criteria, the objectives of the trial, the parameters to be used in monitoring safety and the effectiveness criteria to be evaluated. The clinical investigation of an investigational drug or biological product is generally divided into four phases. Although the phases are usually conducted sequentially, they may overlap or be combined. The four phases of an investigation are as follows: ● Phase 1 . Phase 1 studies include the initial introduction of an investigational new drug or biological product into humans. These studies are designed to evaluate the safety, dosage tolerance, metabolism and pharmacologic actions of the investigational drug or biological product in humans, the side effects associated with increasing doses, and if possible, to gain early evidence on effectiveness. ● Phase 2 . Phase 2 includes the controlled clinical trials conducted to preliminarily or further evaluate the effectiveness of the investigational drug or biological product for a particular indication(s) in patients with the disease or condition under trial, to determine dosage tolerance and optimal dosage, and to identify possible adverse side effects and safety risks associated with the drug or biological product. Phase 2 trials are typically well-controlled, closely monitored, and conducted in a limited patient population. ● Phase 3 . Phase 3 trials are generally controlled clinical trials conducted in an expanded patient population generally at geographically dispersed clinical trial sites. They are performed after preliminary evidence suggesting effectiveness of the drug or biological product has been obtained, and are intended to further evaluate dosage, clinical effectiveness and safety, to establish the overall benefit-risk relationship of the investigational drug or biological product, and to provide an adequate basis for product approval. ● Phase 4 . Post-approval studies may be conducted after initial marketing approval. These studies are used to gain additional experience from the treatment of patients in the intended therapeutic indication. A company’s designation of a clinical trial as being of a particular phase is not necessarily indicative that the study will be sufficient to satisfy the FDA requirements of that phase because this determination cannot be made until the protocol and data have been submitted to and reviewed by the FDA. Moreover, a pivotal trial is a clinical trial that is believed to satisfy FDA requirements for the evaluation of a product candidate’s safety and efficacy such that it can be used, alone or with other pivotal or non-pivotal trials, to support regulatory approval. Generally, pivotal trials are Phase 3 trials, but they may be Phase 1 or Phase 2 trials if the design provides a well-controlled and reliable assessment of clinical benefit, particularly in an area of unmet medical need. 32 Table of Contents In December 2022, with the passage of Food and Drug Omnibus Reform Act, or FDORA, Congress required sponsors to develop and submit a diversity action plan for each Phase 3 clinical trial or any other “pivotal study” of a new drug or biological product. These plans are meant to encourage the enrollment of more diverse patient populations in late-stage clinical trials of FDA-regulated products. Specifically, plans must include the sponsor’s goals for enrollment, the underlying rationale for those goals, and an explanation of how the sponsor intends to meet them. In addition to these requirements, the legislation directs the FDA to issue new guidance on diversity action plans. In January 2024, the FDA issued draft guidance setting out its policies for the collection of race and ethnicity data in clinical trials. In March 2022, the FDA released a final guidance entitled “Expansion Cohorts: Use in First-In-Human Clinical Trials to Expedite Development of Oncology Drugs and Biologics,” which outlines how developers can utilize an adaptive trial design commonly referred to as a seamless trial design in early stages of oncology biological product development (i.e., the first-in-human clinical trial) to compress the traditional three phases of trials into one continuous trial called an expansion cohort trial. Information to support the design of individual expansion cohorts are included in IND applications and assessed by FDA. Expansion cohort trials can potentially bring efficiency to biological product development and reduce developmental costs and time. In June 2023, the FDA issued draft guidance with updated recommendations for GCPs aimed at modernizing the design and conduct of clinical trials. The updates are intended to help pave the way for more efficient clinical trials to facilitate the development of medical products. The draft guidance is adopted from the International Council for Harmonisation’s recently updated E6(R3) draft guideline that was developed to enable the incorporation of rapidly developing technological and methodological innovations into the clinical trial enterprise. In addition, the FDA issued draft guidance outlining recommendations for the implementation of decentralized clinical trials. Concurrent with clinical trials, companies often complete additional animal studies and must also develop additional information about the chemistry and physical characteristics of the candidate product as well as finalize a process for manufacturing the product in commercial quantities in accordance with cGMP requirements. The manufacturing process must be capable of consistently producing quality batches of the drug candidate and, among other things, must develop methods for testing the identity, strength, quality, purity, and potency of the final drug. Additionally, appropriate packaging must be selected and tested, and stability studies must be conducted to demonstrate that the drug candidate does not undergo unacceptable deterioration over its shelf life. Sponsors of clinical trials are required to register and disclose certain clinical trial information on a public registry (clinicaltrials.gov) maintained by the U.S. National Institutes of Health, or NIH. In particular, information related to the product, patient population, phase of investigation, study sites and investigators and other aspects of the clinical trial is made public as part of the registration of the clinical trial. The NIH’s Final Rule on registration and reporting requirements for clinical trials became effective in 2017. Although the FDA has historically not enforced these reporting requirements due to the long delay by the Department of Health and Human Services, or HHS, in issuing final implementing regulations, the FDA has issued several pre-notices for voluntary corrective action and several notices of non-compliance during the past two years. While these notices of non-compliance did not result in civil monetary penalties, the failure to submit clinical trial information to clinicaltrials.gov is a prohibited act under the FDCA with violations subject to potential civil monetary penalties of up to $10,000 for each day the violation continues. Interactions with FDA During the Clinical Development Program Following the clearance of an IND and the commencement of clinical trials, the sponsor will continue to have interactions with the FDA. An annual report on the progress of the study must be submitted to the FDA and more frequently if serious AEs occur. In addition, IND safety reports must be submitted to the FDA for any of the following: serious and unexpected suspected adverse reactions; findings from other studies or animal or in vitro testing that suggest a significant risk in humans exposed to the product; and any clinically important increase in the occurrence of a serious suspected adverse reaction over that listed in the protocol or investigator brochure. Phase 1, Phase 2 and Phase 3 clinical trials may not be completed successfully within any specified period, or at all. The FDA will typically inspect one or more clinical sites to assure compliance with GCP and the integrity of the clinical data submitted. 33 Table of Contents In addition, sponsors are given opportunities to meet with the FDA at certain points in the clinical development program. Specifically, sponsors may meet with the FDA prior to the submission of an IND, or Pre-IND meeting, at the end of Phase 1 clinical trial, or EOP1 meeting, at the end of Phase 2 clinical trial, or EOP2 meeting, and before an NDA or BLA is submitted, or Pre-NDA or Pre-BLA meeting. Meetings at other times may also be requested. There are five types of meetings that occur between sponsors and the FDA. Type A meetings are those that are necessary for an otherwise stalled product development program to proceed or to address an important safety issue. Type B meetings include pre-IND and pre-NDA/pre-BLA meetings, as well as end of phase meetings such as EOP2 meetings. A Type C meeting is any meeting other than a Type A or Type B meeting regarding the development and review of a product, including, for example, meetings to facilitate early consultations on the use of a biomarker as a new surrogate endpoint that has never been previously used as the primary basis for product approval in the proposed context of use. A Type D meeting is focused on a narrow set of issues and does not require input from more than three disciplines or divisions. Finally, INTERACT meetings are intended for novel products and development programs that present unique challenges in the early development of an investigational product. The FDA has indicated that its responses, as conveyed in meeting minutes and advice letters, only constitute mere recommendations and/or advice made to a sponsor and, as such, sponsors are not bound by such recommendations and/or advice. Nonetheless, from a practical perspective, a sponsor’s failure to follow the FDA’s recommendations for design of a clinical program may put the program at significant risk of failure. In September 2023, the FDA issued draft guidance outlining the terms of such meetings in more detail. Expanded Access Expanded access, sometimes called “compassionate use,” is the use of investigational products outside of clinical trials to treat patients with serious or immediately life-threatening diseases or conditions when there are no comparable or satisfactory alternative treatment options. FDA regulations allow access to investigational products under an IND by the sponsor or the treating physician for treatment purposes on a case-by-case basis for: individual patients (single-patient IND applications for treatment in emergency settings and non-emergency settings); intermediate-size patient populations; and larger populations for use of the investigational product under a treatment protocol or treatment IND application. There is no requirement for a sponsor to provide expanded access to an investigational product. However, if a sponsor decides to make its investigational product available for expanded access, the FDA reviews requests for expanded access and determines if treatment may proceed. Expanded access may be appropriate when all of the following criteria apply: patient(s) have a serious or immediately life-threatening disease or condition, and there is no comparable or satisfactory alternative therapy to diagnose, monitor or treat the disease or condition; the potential patient benefit justifies the potential risks of the treatment and the potential risks are not unreasonable in the context or condition to be treated; and the expanded use of the investigational drug for the requested treatment will not interfere with initiation, conduct or completion of clinical investigations that could support marketing approval of the product or otherwise compromise the potential development of the product. Sponsors of one or more investigational products for the treatment of a serious disease(s) or condition(s) must make publicly available their policy for evaluating and responding to requests for expanded access for individual patients. Sponsors are required to make such policies publicly available upon the earlier of initiation of a Phase 2 or Phase 3 trial; or 15 days after the investigational drug or biologic receives designation as a Breakthrough Therapy, fast track product or regenerative medicine advanced therapy. In addition, on May 30, 2018, the Right to Try Act was signed into law. The law, among other things, provides an additional mechanism for patients with a life-threatening condition who have exhausted approved treatments and are unable to participate in clinical trials to access certain investigational products that have completed a Phase 1 trial, are the subject of an active IND and are undergoing investigation for FDA approval. Unlike the expanded access framework described above, the Right to Try Pathway does not require FDA to review or approve requests for use of the investigational product. There is no obligation for a manufacturer to make its investigational products available to eligible patients under the Right to Try Act. 34 Table of Contents Pediatric Studies Under the Pediatric Research Equity Act of 2003, or PREA, an application or supplement thereto must contain data that are adequate to assess the safety and effectiveness of the product for the claimed indications in all relevant pediatric subpopulations, and to support dosing and administration for each pediatric subpopulation for which the product is safe and effective. Sponsors must also submit pediatric study plans prior to the assessment data. Those plans must contain an outline of the proposed pediatric study or studies the sponsor plans to conduct, including study objectives and design, any deferral or waiver requests and other information required by regulation. The sponsor, the FDA, and the FDA’s internal review committee must then review the information submitted, consult with each other and agree upon a final plan. The FDA or the sponsor may request an amendment to the plan at any time. In May 2023, the FDA issued new draft guidance that further describes the pediatric study requirements under PREA. For investigational products intended to treat a serious or life-threatening disease or condition, the FDA must, upon the request of a sponsor, meet to discuss preparation of the initial pediatric study plan or to discuss deferral or waiver of pediatric assessments. In addition, the FDA will meet early in the development process to discuss pediatric study plans with sponsors, and the FDA must meet with sponsors by no later than the end-of-phase 1 meeting for serious or life-threatening diseases and by no later than 90 days after the FDA’s receipt of the study plan. The FDA may, on its own initiative or at the request of the sponsor, grant deferrals for submission of some or all pediatric data until after approval of the product for use in adults, or full or partial waivers from the pediatric data requirements. A deferral may be granted for several reasons, including a finding that the product is ready for approval for use in adults before pediatric trials are complete or that additional safety or effectiveness data needs to be collected before the pediatric trials begin. The law now requires the FDA to send a PREA Non-Compliance letter to sponsors who have failed to submit their pediatric assessments required under PREA, have failed to seek or obtain a deferral or deferral extension or have failed to request approval for a required pediatric formulation. Unless otherwise required by regulation, the pediatric data requirements do not apply to products with orphan designation, although FDA has taken steps to limit what it considers abuse of this statutory exemption in PREA by announcing that it does not intend to grant any additional orphan drug designations for rare pediatric subpopulations of what is otherwise a common disease. The FDA maintains a list of diseases that are exempt from PREA requirements due to low prevalence of disease in the pediatric population. In 2017, with the passage of the FDA Reauthorization Act of 2017, or FDARA, Congress established new requirements to govern certain molecularly targeted cancer indications. Section 505B of the FDCA, as amended by FDARA, requires that any original NDA or BLA submitted on or after August 18, 2020, for a new active ingredient, must contain reports on the molecularly targeted pediatric cancer investigation, unless the requirement is waived or deferred, if the drug that is the subject of the application is: (i) intended for the treatment of an adult cancer, and (ii) directed at a molecular target that the Secretary of HHS determines to be substantially relevant to the growth or progression of a pediatric cancer in accordance with FDA guidance. The FDA maintains a list of diseases that are exempt from PREA requirements due to low prevalence of disease in the pediatric population. Submission and Review of an NDA or BLA by the FDA In order to obtain approval to market a drug or biological product in the United States, a marketing application must be submitted to the FDA that provides data establishing the safety and effectiveness of the proposed drug product for the proposed indication, and the safety, purity and potency of the biological product for its intended indication. The application includes all relevant data available from pertinent preclinical and clinical trials, including negative or ambiguous results as well as positive findings, together with detailed information relating to the product’s chemistry, manufacturing, controls and proposed labeling, among other things. Data can come from company-sponsored clinical trials intended to test the safety and effectiveness of a use of a product, or from a number of alternative sources, including studies initiated by investigators. To support marketing approval, the data submitted must be sufficient in quality and quantity to establish the safety and effectiveness of the investigational drug product and the safety, purity and potency of the biological product to the satisfaction of the FDA. The application is the vehicle through which sponsors formally propose that the FDA approve a new product for marketing and sale in the United States for one or more indications. Every new product candidate must be the subject of an approved 35 Table of Contents NDA or BLA before it may be commercialized in the United States. Under federal law, the submission of most applications is subject to an application user fee. The sponsor of an approved application is also subject to an annual program fee. Certain exceptions and waivers are available for some of these fees, such as an exception from the application fee for products with orphan designation and a waiver for certain small businesses. If an application is withdrawn prior to the FDA acceptance for filing, 75% of these fees may be refunded to the sponsor. If an application is withdrawn after filing, a lower portion of these fees may be refunded in certain circumstances. Currently, the fee required for the submission and review of an application for federal fiscal year 2024 is approximately $4.05 million, and the sponsor of an approved application is also subject to an annual program fee, currently more than $416,000 for federal fiscal year 2024. The FDA conducts a preliminary review of all applications within 60 days of receipt and must inform the sponsor at that time or before whether an application is sufficiently complete to permit substantive review. The FDA’s regulations state that an application “shall not be considered as filed until all pertinent information and data have been received” by the FDA. In the event that the FDA determines that an application does not satisfy this standard, it will issue a Refuse to File, or RTF, determination to the applicant. Typically, an RTF will be based on administrative incompleteness, such as clear omission of information or sections of required information; scientific incompleteness, such as omission of critical data, information or analyses needed to evaluate safety and efficacy or provide adequate directions for use; or inadequate content, presentation, or organization of information such that substantive and meaningful review is precluded. The FDA may request additional information rather than accept an application for filing. In this event, the application must be resubmitted with the additional information. The resubmitted application is also subject to review before the FDA accepts it for filing. The FDA has agreed to specified performance goals in the review process of NDAs and BLAs. Under that agreement, 90% of applications seeking approval of New Molecular Entities, or NMEs, are meant to be reviewed within ten months from the date on which FDA accepts the NDA for filing, and 90% of applications for NMEs that have been designated for “priority review” are meant to be reviewed within six months of the filing date. The review process and the Prescription Drug User Fee Act goal date may be extended by the FDA for three additional months to consider new information or clarification provided by the sponsor to address an outstanding deficiency identified by the FDA following the original submission. In connection with its review of an application, the FDA typically will inspect the facility or facilities where the product is or will be manufactured. These pre-approval inspections may cover all facilities associated with an NDA or BLA submission, including drug component manufacturing (e.g., active pharmaceutical ingredients), finished drug product manufacturing, and control testing laboratories. The FDA will not approve an application unless it determines that the manufacturing processes and facilities are in compliance with cGMP requirements and adequate to assure consistent production of the product within required specifications. Additionally, before approving an NDA or BLA, the FDA will typically inspect one or more clinical sites to assure compliance with GCP and the integrity of the clinical data submitted to the FDA. With the passage of FDORA, Congress clarified the FDA’s authority to conduct inspections by expressly permitting inspection of facilities involved in the preparation, conduct, or analysis of clinical and non-clinical studies submitted to the FDA as well as other persons holding study records or involved in the study process. In addition, as a condition of approval, the FDA may require a sponsor to develop a REMS. REMS use risk minimization strategies beyond the professional labeling to ensure that the benefits of the product outweigh the potential risks. To determine whether a REMS is needed, the FDA will consider the size of the population likely to use the product, seriousness of the disease, expected benefit of the product, expected duration of treatment, seriousness of known or potential AEs, and whether the product is a new molecular entity. Under FDARA, the FDA must implement a protocol to expedite review of responses to inspection reports pertaining to certain applications, including applications for products in shortage or those for which approval is dependent on remediation of conditions identified in the inspection report. The FDA may refer an application for a novel product to an advisory committee or explain why such referral was not made. Typically, an advisory committee is a panel of independent experts, including clinicians and other scientific experts, that reviews, evaluates and provides a recommendation as to whether the application should be approved and under what conditions. The FDA is not bound by the recommendations of an advisory committee, but it considers such recommendations carefully when making decisions. 36 Table of Contents The FDA’s Decision on an NDA or BLA The FDA reviews an application to determine, among other things, whether the product is safe and whether it is effective for its intended use(s), with the latter determination being made on the basis of substantial evidence. The term “substantial evidence” is defined under the FDCA as “evidence consisting of adequate and well-controlled investigations, including clinical investigations, by experts qualified by scientific training and experience to evaluate the effectiveness of the product involved, on the basis of which it could fairly and responsibly be concluded by such experts that the product will have the effect it purports or is represented to have under the conditions of use prescribed, recommended, or suggested in the labeling or proposed labeling thereof.” The FDA has interpreted this evidentiary standard to require at least two adequate and well-controlled clinical investigations to establish effectiveness of a new product. Under certain circumstances, however, the FDA has indicated that a single trial with certain characteristics and additional information may satisfy this standard. In December 2019, the FDA issued draft guidance further explaining the studies that are needed to establish substantial evidence of effectiveness. Although the FDA has not yet finalized that guidance, it did issue additional draft guidance in September 2023 that outlines considerations for relying on confirmatory evidence in lieu of a second clinical study. After evaluating the application and all related information, including the advisory committee recommendations, if any, and inspection reports of manufacturing facilities and clinical trial sites, the FDA will issue either an approval letter or a Complete Response Letter, or CRL. To issue an approval letter, the FDA must determine that the drug is effective and that its expected benefits outweigh its potential risks to patients. This “benefit-risk” assessment is informed by the extensive body of evidence about the product’s safety and efficacy in the NDA or BLA. This assessment is also informed by other factors, including: the severity of the underlying condition and how well patients’ medical needs are addressed by currently available therapies; uncertainty about how the premarket clinical trial evidence will extrapolate to real-world use of the product in the post-market setting; and whether risk management tools are necessary to manage specific risks. A CRL indicates that the review cycle of the application is complete, and the application will not be approved in its present form. A CRL generally outlines the deficiencies in the submission and may require substantial additional testing or information in order for the FDA to reconsider the application. The CRL may require additional clinical or other data, additional pivotal Phase 3 clinical trial(s) and/or other significant and time-consuming requirements related to clinical trials, preclinical studies or manufacturing. If a CRL is issued, the sponsor will have one year to respond to the deficiencies identified by the FDA, at which time the FDA can deem the application withdrawn or, in its discretion, grant the sponsor an additional six-month extension to respond. The FDA has committed to reviewing resubmissions in response to an issued CRL in either two or six months depending on the type of information included. Even with the submission of this additional information, however, the FDA ultimately may decide that the application does not satisfy the regulatory criteria for approval. The FDA has taken the position that a CRL is not final agency action making the determination subject to judicial review. An approval letter, on the other hand, authorizes commercial marketing of the product with specific prescribing information for specific indications described in the FDA-approved labeling. Depending on the specific risk(s) to be addressed, the FDA may require that contraindications, warnings or precautions be included in the product labeling, require that post-approval trials, including Phase 4 clinical trials, be conducted to further assess a product’s safety after approval, require testing and surveillance programs to monitor the product after commercialization or impose other conditions, including distribution and use restrictions or other risk management mechanisms under a REMS which can materially affect the potential market and profitability of the product. The FDA may prevent or limit further marketing of a product based on the results of post-marketing trials or surveillance programs. After approval, some types of changes to the approved product, such as adding new indications, manufacturing changes and additional labeling claims, are subject to further testing requirements and FDA review and approval. Under the Ensuring Innovation Act, which was signed into law in April 2021, the FDA must publish action packages summarizing its decisions to approve new drugs and biologics within 30 days of approval of such products. To date, CRLs are not publicly available documents. 37 Table of Contents Fast Track, Breakthrough Therapy and Priority Review Designations The FDA is authorized to designate certain products for expedited review if they are intended to address an unmet medical need in the treatment of a serious or life-threatening disease or condition. These programs include fast track designation, Breakthrough Therapy designation and priority review designation. None of these expedited programs changes the standards for approval but they may help expedite the development or approval process governing product candidates. Specifically, the FDA may designate a product for Fast Track review if it is intended, whether alone or in combination with one or more other products, for the treatment of a serious or life-threatening disease or condition, and it demonstrates the potential to address unmet medical needs for such a disease or condition. For Fast Track products, sponsors may have greater interactions with the FDA and the FDA may initiate review of sections of a Fast Track product’s application before the application is complete. This rolling review may be available if the FDA determines, after preliminary evaluation of clinical data submitted by the sponsor, that a Fast Track product may be effective. The sponsor must also provide, and the FDA must approve, a schedule for the submission of the remaining information and the sponsor must pay applicable user fees. However, the FDA’s time period goal for reviewing a Fast Track application does not begin until the last section of the application is submitted. In addition, the Fast Track designation may be withdrawn by the FDA if the FDA believes that the designation is no longer supported by data emerging in the clinical trial process. Second, a product may be designated as a Breakthrough Therapy if it is intended, either alone or in combination with one or more other products, to treat a serious or life-threatening disease or condition and preliminary clinical evidence indicates that the product may demonstrate substantial improvement over existing therapies on one or more clinically significant endpoints, such as substantial treatment effects observed early in clinical development. The FDA may take certain actions with respect to Breakthrough Therapies, including holding meetings with the sponsor throughout the development process; providing timely advice to the product sponsor regarding development and approval; involving more senior staff in the review process; assigning a cross-disciplinary project lead for the review team; and taking other steps to help the sponsor design the clinical trials in an efficient manner. Third, the FDA may designate a product for priority review if it is a product that treats a serious condition and, if approved, would provide a significant improvement in safety or effectiveness. The FDA determines, on a case-by-case basis, whether the proposed product represents a significant improvement when compared with other available therapies. Significant improvement may be illustrated by evidence of increased effectiveness in the treatment of a condition, elimination or substantial reduction of a treatment-limiting product reaction, documented enhancement of patient compliance that may lead to improvement in serious outcomes, and evidence of safety and effectiveness in a new subpopulation. A priority designation is intended to direct overall attention and resources to the evaluation of such applications, and to shorten the FDA’s goal for taking action on a marketing application from ten months to six months. Accelerated Approval Pathway The FDA may grant accelerated approval to a product for a serious or life-threatening condition that provides meaningful therapeutic advantage to patients over existing treatments based upon a determination that the product has an effect on a surrogate endpoint that is reasonably likely to predict clinical benefit. The FDA may also grant accelerated approval for such a condition when the product has an effect on an intermediate clinical endpoint that can be measured earlier than an effect on irreversible morbidity or mortality, or IMM, and that is reasonably likely to predict an effect on irreversible morbidity or mortality or other clinical benefit, taking into account the severity, rarity or prevalence of the condition and the availability or lack of alternative treatments. Products granted accelerated approval must meet the same statutory standards for safety and effectiveness as those granted traditional approval. For the purposes of accelerated approval, a surrogate endpoint is a marker, such as a laboratory measurement, radiographic image, physical sign or other measure that is thought to predict clinical benefit, but is not itself a measure of clinical benefit. Surrogate endpoints can often be measured more easily or more rapidly than clinical endpoints. An intermediate clinical endpoint is a measurement of a therapeutic effect that is considered reasonably likely to predict the clinical benefit of a drug, such as an effect on IMM. The FDA has limited experience with accelerated approvals based on intermediate clinical endpoints but has indicated that such endpoints generally may support accelerated approval where the therapeutic 38 Table of Contents effect measured by the endpoint is not itself a clinical benefit and basis for traditional approval, if there is a basis for concluding that the therapeutic effect is reasonably likely to predict the ultimate clinical benefit of a product. The accelerated approval pathway is most often used in settings in which the course of a disease is long, and an extended period of time is required to measure the intended clinical benefit of a product, even if the effect on the surrogate or intermediate clinical endpoint occurs rapidly. Thus, accelerated approval has been used extensively in the development and approval of products for treatment of a variety of cancers in which the goal of therapy is generally to improve survival or decrease morbidity and the duration of the typical disease course requires lengthy and sometimes large trials to demonstrate a clinical or survival benefit. Thus, the benefit of accelerated approval derives from the potential to receive approval based on surrogate endpoints sooner than possible for trials with clinical or survival endpoints, rather than deriving from any explicit shortening of the FDA approval timeline, as is the case with priority review. The accelerated approval pathway is usually contingent on a sponsor’s agreement to conduct, in a diligent manner, additional post-approval confirmatory studies to verify and describe the product’s clinical benefit. As a result, a product candidate approved on this basis is subject to rigorous post-marketing compliance requirements, including the completion of phase 4 or post-approval trials to confirm the effect on the clinical endpoint. Failure to conduct required post-approval studies, or confirm a clinical benefit during post-marketing studies, would allow the FDA to initiate expedited proceedings to withdraw approval of the product. All promotional materials for product candidates approved under accelerated regulations are subject to prior review by the FDA. With the passage of FDORA in December 2022, Congress modified certain provisions governing accelerated approval of drug and biologic products. Specifically, the new legislation authorized the FDA to require a sponsor to have its confirmatory clinical trial underway before accelerated approval is awarded, require a sponsor of a product granted accelerated approval to submit progress reports on its post-approval studies to the FDA every six months (until the study is completed), and use expedited procedures to withdraw accelerated approval of an NDA or BLA after the confirmatory trial fails to verify the product’s clinical benefit. Further, FDORA requires the agency to publish on its website “the rationale for why a post-approval study is not appropriate or necessary” whenever it decides not to require such a study upon granting accelerated approval. In March 2023, the FDA issued draft guidance that outlines its current thinking and approach to accelerated approval. The agency indicated that the accelerated approval pathway is commonly used for approval of oncology drugs due to the serious and life-threatening nature of cancer. Although single-arm trials have been commonly used to support accelerated approval, a randomized controlled trial is the preferred approach as it provides a more robust efficacy and safety assessment and allows for direct comparisons to an available therapy. To that end, the FDA outlined considerations for designing, conducting, and analyzing data for trials intended to support accelerated approvals of oncology therapeutics. While this guidance is currently only in draft form and will ultimately not be legally binding even when finalized, sponsors typically observe the FDA’s guidance closely to ensure that their investigational products qualify for accelerated approval. Post-Approval Regulation Drugs and biologics manufactured or distributed pursuant to FDA approvals are subject to pervasive and continuing regulation by the FDA, including, among other things, requirements relating to recordkeeping, periodic reporting, product sampling and distribution, advertising and promotion and reporting of adverse experiences with the product. After approval, most changes to the approved product, such as adding new indications or other labeling claims, are subject to prior FDA review and approval. There also are continuing annual user fee requirements for any marketed products and the establishments at which such products are manufactured, as well as new application fees for supplemental applications with clinical data. In addition, manufacturers and other entities involved in the manufacture and distribution of approved products are required to register their establishments with the FDA and state agencies and are subject to periodic unannounced inspections by the FDA and these state agencies for compliance with cGMP requirements. Changes to the manufacturing process are strictly regulated and often require prior FDA approval before being implemented. FDA regulations also require investigation and correction of any deviations from cGMP and impose reporting and documentation requirements 39 Table of Contents upon the sponsor and any third-party manufacturers that the sponsor may decide to use. Accordingly, manufacturers must continue to expend time, money, and effort in the area of production and quality control to maintain cGMP compliance. Once an approval is granted, the FDA may withdraw the approval if compliance with regulatory requirements and standards is not maintained or if problems occur after the product reaches the market. Later discovery of previously unknown problems with a product, including AEs of unanticipated severity or frequency, or with manufacturing processes, or failure to comply with regulatory requirements, may result in revisions to the approved labeling to add new safety information; imposition of post-market studies or clinical trials to assess new safety risks; or imposition of distribution or other restrictions under a REMS program. Other potential consequences include, among other things: ● restrictions on the marketing or manufacturing of the product, suspension of the approval, or complete withdrawal of the product from the market or product recalls; ● fines, warning letters or holds on post-approval clinical trials; ● refusal of the FDA to approve pending NDAs or supplements to approved NDAs, or suspension or revocation of product license approvals; ● product seizure or detention, or refusal to permit the import or export of products; or ● injunctions or the imposition of civil or criminal penalties. The FDA strictly regulates marketing, labeling, advertising and promotion of products that are placed on the market. Products may be promoted only for the approved indications and in accordance with the provisions of the approved label. The FDA and other agencies actively enforce the laws and regulations prohibiting the promotion of off-label uses, and a company that is found to have improperly promoted off-label uses may be subject to significant liability. If a company is found to have promoted off-label uses, it may become subject to adverse public relations and administrative and judicial enforcement by the FDA, the Department of Justice, or the Office of the Inspector General of the Department of Health and Human Services, as well as state authorities. This could subject a company to a range of penalties that could have a significant commercial impact, including civil and criminal fines and agreements that materially restrict the manner in which a company promotes or distributes drug products. In September 2021, the FDA published final regulations that describe the types of evidence the FDA will consider in determining the intended use of a drug or biologic. It may be permissible, under very specific, narrow conditions, for a manufacturer to engage in nonpromotional, non-misleading communication regarding off-label information, such as distributing scientific or medical journal information. Moreover, with the passage of the Pre-Approval Information Exchange Act in December 2022, sponsors of products that have not been approved may proactively communicate to payors certain information about products in development to help expedite patient access upon product approval. Previously, such communications were permitted under FDA guidance, but the new legislation explicitly provides protection to sponsors who convey certain information about products in development to payors, including unapproved uses of approved products. In addition, in October 2023, the FDA published draft guidance outlining the agency’s non-binding policies governing the distribution of scientific information on unapproved uses to healthcare providers. This draft guidance calls for such communications to be truthful, non-misleading, factual, and unbiased and include all information necessary for healthcare providers to interpret the strengths and weaknesses and validity and utility of the information about the unapproved use. In addition, the distribution of prescription pharmaceutical products is subject to a variety of federal and state laws. The Prescription Drug Marketing Act, or PDMA, was the first federal law to set minimum standards for the registration and regulation of drug distributors by the states and to regulate the distribution of drug samples. Both the PDMA and state laws limit the distribution of prescription pharmaceutical product samples and impose requirements to ensure accountability in distribution. In November 2013, the federal Drug Supply Chain Security Act, or DSCSA, became effective in the United States, mandating an industry-wide, electronic, interoperable system to trace prescription drugs through the pharmaceutical distribution supply chain with a ten-year phase-in process. Manufacturers were required by November 2023 to have such systems and processes in place but, in August 2023, the FDA set a one-year period in which it would exercise its enforcement discretion with respect to these requirements. 40 Table of Contents Biosimilars and Regulatory Exclusivity The 2010 Patient Protection and Affordable Care Act, or ACA, which was signed into law on March 23, 2010, included a subtitle called the Biologics Price Competition and Innovation Act of 2009, or BPCIA. The BPCIA established a regulatory scheme authorizing the FDA to approve biosimilars and interchangeable biosimilars. To date, the FDA has approved a number of biosimilar products and several interchangeable biosimilar products. The FDA has also issued numerous guidance documents outlining its approach to reviewing and licensing biosimilars and interchangeable biosimilars under the PHSA. Under the BPCIA, a manufacturer may submit an application for licensure of a biologic product that is “biosimilar to” or “interchangeable with” a previously approved biological product or “reference product.” In order for the FDA to license a biosimilar product, it must find that there are no clinically meaningful differences between the reference product and proposed biosimilar product in terms of safety, purity, and potency. For the FDA to license a biosimilar product as interchangeable with a reference product, the agency must find that the biosimilar product can be expected to produce the same clinical results as the reference product, and (for products administered multiple times) that the biologic and the reference biologic may be switched after one has been previously administered without increasing safety risks or risks of diminished efficacy relative to exclusive use of the reference biologic. In December 2022, Congress clarified through FDORA that the FDA may license multiple first interchangeable biosimilar biological products so long as the products are all approved on the first day on which such a product is approved as interchangeable with the reference product. Under the BPCIA, an application for a biosimilar product may not be submitted to the FDA until four years following the date of approval of the reference product. The FDA may not license a biosimilar product until 12 years from the date on which the reference product was approved. Even if a product is considered to be a reference product eligible for exclusivity, another company could market a competing version of that product if the FDA approves a full BLA for such product containing the sponsor’s own preclinical data and data from adequate and well-controlled clinical trials to demonstrate the safety, purity and potency of their product. The BPCIA also created certain exclusivity periods for biosimilars approved as interchangeable products. There have been recent government proposals to reduce the 12-year reference product exclusivity period, but none has been enacted to date. At the same time, since passage of the BPCIA, many states have passed laws or amendments to laws, which address pharmacy practices involving biosimilar products. Orphan Drug Designation and Exclusivity Under the Orphan Drug Act, the FDA may designate a drug product as an “orphan drug” if it is intended to treat a rare disease or condition, generally meaning that it affects fewer than 200,000 individuals in the United States, or more in cases in which there is no reasonable expectation that the cost of developing and making a drug product available in the United States for treatment of the disease or condition will be recovered from sales of the product. A company must request orphan drug designation before submitting an NDA or BLA for the candidate product. If the request is granted, the FDA will disclose the identity of the therapeutic agent and its potential use. Orphan drug designation does not shorten the Prescription Drug User Fee Act, or PDUFA, goal dates for the regulatory review and approval process, although it does convey certain advantages such as tax benefits and exemption from the PDUFA application fee. If a product with orphan designation receives the first FDA approval for the disease or condition for which it has such designation or for a select indication or use within the rare disease or condition for which it was designated, the product generally will receive orphan drug exclusivity. Orphan drug exclusivity means that the FDA may not approve another sponsor’s marketing application for the same drug for the same indication for seven years, except in certain limited circumstances. Orphan exclusivity does not block the approval of a different product for the same rare disease or condition, nor does it block the approval of the same product for different indications. If a drug or biologic designated as an orphan drug ultimately receives marketing approval for an indication broader than what was designated in its orphan drug application, it may not be entitled to exclusivity. Orphan exclusivity will not bar approval of another product under certain circumstances, including if a company with orphan drug exclusivity is not able to meet market demand and in cases where a subsequent product with the same drug or biologic for the same indication is shown to be clinically superior to the approved product on the basis of greater efficacy or safety, or providing a major contribution to patient care. Under Omnibus legislation signed by President Trump on December 27, 2020, the requirement for a subsequent product to show clinical superiority in order to break the previous product’s orphan drug exclusivity applies to drugs and biologics that 41 Table of Contents received orphan drug designation before enactment of FDARA in 2017 but have not yet been approved or licensed by FDA. Further, in September 2021, the Court of Appeals for the 11 th Circuit held that, for the purpose of determining the scope of market exclusivity, the term “same disease or condition” in the statute means the designated “rare disease or condition” and could not be interpreted by the FDA to mean the “indication or use.” Thus, the court concluded, orphan drug exclusivity applies to the entire designated disease or condition rather than the “indication or use.” Although there have been legislative proposals to overrule this decision, they have not been enacted into law. On January 23, 2023, the FDA announced that, in matters beyond the scope of that court order, the FDA will continue to apply its existing regulations tying orphan-drug exclusivity to the uses or indications for which the orphan drug was approved. Pediatric Exclusivity Pediatric exclusivity is another type of non-patent marketing exclusivity in the United States and, if granted, provides for the attachment of an additional six months of existing regulatory exclusivity. For drug products, the six-month exclusivity may be attached to the term of any existing patent or regulatory exclusivity. For biologic products, the six-month period may be attached to any existing regulatory exclusivities but not to any patent terms. This six-month exclusivity may be granted if an NDA or BLA sponsor submits pediatric data that fairly respond to a written request from the FDA for such data. The data do not need to show the product to be effective in the pediatric population studied; rather, if the clinical trial is deemed to fairly respond to the FDA’s request, the additional protection is granted. If reports of requested pediatric studies are submitted to and accepted by the FDA within the statutory time limits, whatever statutory or regulatory periods of non-patent exclusivity for drugs and biologics, or patent protection that covers a drug product, are extended by six months. This is not a patent term extension, but it effectively extends the regulatory period during which the FDA cannot approve another application. Patent Term Restoration and Extension A patent claiming a new drug product may be eligible for a limited patent term extension under the Hatch-Waxman Act, which permits a patent restoration of up to five years for patent term lost during product development and the FDA regulatory review. The restoration period granted on a patent covering a product is typically one-half the time between the effective date of the IND approval and the submission date of an application, plus the time between the submission date of an application and the ultimate approval date. Patent term restoration cannot be used to extend the remaining term of a patent past a total of 14 years from the product’s approval date. Only one patent applicable to an approved product is eligible for the extension, and the application for the extension must be submitted prior to the expiration of the patent in question. A patent that covers multiple products for which approval is sought can only be extended in connection with one of the approvals. The USPTO reviews and approves the application for any patent term extension or restoration in consultation with the FDA. Pharmaceutical Coverage, Pricing and Reimbursement In the United States and markets in other countries, patients who are prescribed treatments for their conditions and providers performing the prescribed services generally rely on third-party payors to reimburse all or part of the associated healthcare costs. Significant uncertainty exists as to the coverage and reimbursement status of products approved by the FDA and other government authorities. Thus, even if a product candidate is approved, sales of the product will depend, in part, on the extent to which third-party payors, including government health programs in the United States such as Medicare and Medicaid, commercial health insurers and managed care organizations, provide coverage, and establish adequate reimbursement levels for, the product. The process for determining whether a payor will provide coverage for a product may be separate from the process for setting the price or reimbursement rate that the payor will pay for the product once coverage is approved. Third-party payors are increasingly challenging the prices charged, examining the medical necessity, and reviewing the cost-effectiveness of medical products and services and imposing controls to manage costs. Third-party payors may limit coverage to specific products on an approved list, also known as a formulary, which might not include all of the approved products for a particular indication. 42 Table of Contents It is time consuming and expensive to seek coverage and reimbursement from third-party payors. In order to secure coverage and reimbursement for any product that might be approved for sale, a company may need to conduct expensive pharmacoeconomic studies in order to demonstrate the medical necessity and cost- effectiveness of the product, in addition to the costs required to obtain FDA or other comparable marketing approvals. Nonetheless, product candidates may not be considered medically necessary or cost effective. A decision by a third-party payor not to cover a product candidate could reduce physician utilization once the product is approved and have a material adverse effect on sales, results of operations and financial condition. Additionally, a payor’s decision to provide coverage for a product does not imply that an adequate reimbursement rate will be approved. Further, one payor’s determination to provide coverage for a drug product does not assure that other payors will also provide coverage and reimbursement for the product, and the level of coverage and reimbursement can differ significantly from payor to payor. Healthcare Law and Regulation Health care providers and third-party payors play a primary role in the recommendation and prescription of drug products that are granted marketing approval. Arrangements with providers, consultants, third-party payors and customers are subject to broadly applicable fraud and abuse, anti-kickback, false claims laws, patient privacy laws and regulations and other health care laws and regulations that may constrain business and/or financial arrangements. Restrictions under applicable federal and state health care laws and regulations, include the federal Anti-Kickback Statute, which prohibits, among other things, persons and entities from knowingly and willfully soliciting, offering, paying, receiving or providing remuneration, directly or indirectly, in cash or in kind, to induce or reward either the referral of an individual for, or the purchase, order or recommendation of, any good or service, for which payment may be made, in whole or in part, under a federal health care program such as Medicare and Medicaid; the federal civil and criminal false claims laws, false statements, and civil monetary penalties laws, including the civil False Claims Act, which prohibit individuals or entities from, among other things, knowingly presenting, or causing to be presented, to the federal government, claims for payment that are false, fictitious or fraudulent or knowingly making, using or causing to made or used a false record or statement to avoid, decrease or conceal an obligation to pay money to the federal government; the Health Insurance Portability and Accountability Act, or HIPAA, which, in addition to privacy protections applicable to healthcare providers and other entities, prohibits executing a scheme to defraud any healthcare benefit program or making false statements relating to healthcare matters; federal laws that require pharmaceutical manufacturers to report certain calculated product prices to the government or provide certain discounts or rebates to government authorities or private entities, often as a condition of reimbursement under government healthcare programs; analogous state laws and regulations, including state anti-kickback and false claims laws; and the federal transparency requirements known as the federal Physician Payments Sunshine Act, which requires certain manufacturers of drugs, devices, biologics and medical supplies to report annually to the Centers for Medicare & Medicaid Services, or CMS, within the United States Department of Health and Human Services, information related to payments and other transfers of value made by that entity to physicians (defined to include doctors, dentists, optometrists, podiatrists and chiropractors) and teaching hospitals, as well as ownership and investment interests held by physicians and their immediate family members. Effective January 1, 2022, these federal transparency reporting obligations will extend to include transfers of value made during the previous year to physician assistants, nurse practitioners, clinical nurse specialists, anesthesiologist assistants, certified registered nurse anesthetists and certified nurse midwives. In addition, HIPAA as amended by the Health Information Technology for Economic and Clinical Health Act, or HITECH, among other things, imposes limitations on certain covered healthcare providers, health plans, and healthcare clearinghouses and their respective business associates and their covered subcontractors that perform services for them that involve the use, or disclosure of, individually identifiable health information, relating to the privacy, security and transmission of individually identifiable health information. Further, some state laws require pharmaceutical companies to comply with the pharmaceutical industry’s voluntary compliance guidelines and the relevant compliance guidance promulgated by the federal government in addition to requiring manufacturers to report information related to payments to physicians and other health care providers or marketing expenditures or restrict financial interactions between pharmaceutical companies and healthcare providers. Additionally, some state and local laws require the registration of pharmaceutical sales representatives in the jurisdiction. State and foreign laws also govern the privacy and security of health information in some circumstances, many of which differ from each other in significant ways and often are not preempted by HIPAA, thus complicating compliance efforts. In particular, numerous federal and state laws and regulations, including state data breach notification laws, state health 43 Table of Contents information privacy laws, and federal and state consumer protection laws, govern the collection, use, disclosure, and protection of health-related and other personal information. In addition, we may be subject to laws and regulations prohibiting bribery and corruption such as the Foreign Corrupt Practices Act, or FCPA, which prohibits companies and their intermediaries from making, or offering or promising to make, improper payments to non-U.S. officials for the purpose of obtaining or retaining business or otherwise seeking favorable treatment as well as federal consumer protection and unfair competition laws, which broadly regulate marketplace activities and activities that potentially harm consumers. Violation of the laws described above or any other governmental laws and regulations may result in significant penalties, including civil, criminal, and administrative penalties, damages, fines, the curtailment or restructuring of operations, the exclusion from participation in federal and state healthcare programs, disgorgement, contractual damages, reputational harm, diminished profits and future earnings, imprisonment, and additional reporting requirements and oversight if a manufacturer becomes subject to a corporate integrity agreement or similar agreement to resolve allegations of non-compliance with these laws. Furthermore, efforts to ensure that business activities and business arrangements comply with applicable healthcare laws and regulations can be costly. Similar healthcare laws and regulations exist in the EU and other jurisdictions, including reporting requirements detailing interactions with and payments to healthcare providers and laws governing the privacy and security of personal information Health Care Reform in the United States and Potential Changes to Health Care Laws Sales of any biopharmaceutical products, if and when approved by the FDA or analogous authorities outside the United States, will depend in significant part on the availability of third-party coverage and adequate reimbursement for the products. Health care reform has been a significant trend in the U.S. health care industry and elsewhere. In particular, government authorities and other third-party payors have attempted to control costs by limiting coverage and the amount of reimbursement for particular medical products and services. Under the former Trump administration, there were efforts to repeal or modify prior health care reform legislation and regulation and also to implement new health care reform measures, including measures related to payment for drugs under government health care programs. However, on June 17, 2021 the U.S. Supreme Court dismissed a challenge on procedural grounds that argued the ACA is unconstitutional in its entirety because the “individual mandate’’ was repealed by Congress. Thus, the ACA will remain in effect in its current form. The nature and scope of health care reform in the new Biden administration remains uncertain but early actions including additional health care reform, its expressed intent to pursue certain policy initiatives to reduce drug prices, as well as challenges to actions taken under the Trump administration have been taken and are likely to continue. There has been heightened governmental scrutiny in recent years over the manner in which manufacturers set prices for their marketed products, which has resulted in proposed and enacted federal and state legislation designed to, among other things, bring more transparency to product pricing and reform government program reimbursement methodologies for pharmaceutical and biologic products. For example, on August 16, 2022, the Inflation Reduction Act of 2022, or the IRA, was signed into law by President Biden. The new legislation has implications for Medicare Part D, which is a program available to individuals who are entitled to Medicare Part A or enrolled in Medicare Part B, to give them the option of paying a monthly premium for outpatient prescription drug coverage. Among other things, the IRA requires manufacturers of certain drugs to engage in price negotiations with Medicare (beginning in 2026), with prices that can be negotiated subject to a cap; imposes rebates under Medicare Part B and Medicare Part D to penalize price increases that outpace inflation (first due in 2023); and replaces the Part D coverage gap discount program with a new discounting program (beginning in 2025). The IRA permits the Secretary of HHS to implement many of these provisions through guidance, as opposed to regulation, for the initial years. Specifically, with respect to price negotiations, Congress authorized Medicare to negotiate lower prices for certain costly single-source drug and biologic products that do not have competing generics or biosimilars and are reimbursed under Medicare Part B and Part D. CMS may negotiate prices for ten high-cost drugs paid for by Medicare Part D starting in 2026, followed by 15 Part D drugs in 2027, 15 Part B or Part D drugs in 2028, and 20 Part B or Part D drugs in 2029 and 44 Table of Contents beyond. This provision applies to drug products that have been approved for at least 9 years and biologics that have been licensed for 13 years, but it does not apply to drugs and biologics that have been approved for a single rare disease or condition. Further, the legislation subjects drug manufacturers to civil monetary penalties and a potential excise tax for failing to comply with the legislation by offering a price that is not equal to or less than the negotiated “maximum fair price” under the law or for taking price increases that exceed inflation. The legislation also requires manufacturers to pay rebates for drugs in Medicare Part D whose price increases exceed inflation. The new law also caps Medicare out-of-pocket drug costs at an estimated $4,000 a year in 2024 and, thereafter beginning in 2025, at $2,000 a year. On June 6, 2023, Merck & Co. filed a lawsuit against the HHS and CMS asserting that, among other things, the IRA’s Drug Price Negotiation Program for Medicare constitutes an uncompensated taking in violation of the Fifth Amendment of the Constitution. Subsequently, a number of other parties, including the U.S. Chamber of Commerce, Bristol Myers Squibb Company, the Pharmaceutical Research and Manufacturers of America, or PhRMA, Astellas, Novo Nordisk, Janssen Pharmaceuticals, Novartis, AstraZeneca and Boehringer Ingelheim, also filed lawsuits in various courts with similar constitutional claims against the HHS and CMS. We expect that litigation involving these and other provisions of the IRA will continue, with unpredictable and uncertain results. In addition, the HHS and the FDA published a final rule allowing states and other entities to develop a Section 804 Importation Program to import certain prescription drugs from Canada into the United States. That regulation was challenged in a lawsuit by PhRMA but the case was dismissed by a federal district court in February 2023 after the court found that PhRMA did not have standing to sue the HHS. Nine states (Colorado, Florida, Maine, New Hampshire, New Mexico, North Dakota, Texas, Vermont and Wisconsin) have passed laws allowing for the importation of drugs from Canada. Certain of these states have submitted Section 804 Importation Program proposals and are awaiting FDA approval. On January 5, 2024, the FDA approved Florida’s plan for Canadian drug importation. At the state level, legislatures are increasingly passing legislation and implementing regulations designed to control pharmaceutical and biological product pricing, including price or patient reimbursement constraints, discounts, restrictions on certain product access and marketing cost disclosure and transparency measures, and, in some cases, designed to encourage importation from other countries and bulk purchasing. In addition, regional health care authorities and individual hospitals are increasingly using bidding procedures to determine what pharmaceutical products and which suppliers will be included in their prescription drug and other health care programs. These measures could reduce the ultimate demand for our products, once approved, or put pressure on our product pricing. We expect that additional state and federal healthcare reform measures will be adopted in the future, any of which could limit the amounts that federal and state governments will pay for healthcare products and services, which could result in reduced demand for our product candidates or additional pricing pressures. We cannot predict the likelihood, nature or extent of government regulation that may arise from future legislation or administrative or executive action, either in the United States or abroad. We expect that additional federal and state health care reform measures will be adopted in the future, any of which could limit the amounts that federal and state governments will pay for health care products and services. Data Privacy Regulation U.S. Privacy Law There are multiple privacy and data security laws that may impact our business activities in the United States and in other countries where we may conduct trials or do business in the future. These laws are evolving and may increase both our obligations and our regulatory risks in the future. In the health care industry generally, for example, under HIPAA, the U.S. Department of Health and Human Services has issued regulations to protect the privacy and security of protected health information used or disclosed by specific covered entities including certain healthcare providers, health plans and healthcare clearinghouses. HIPAA also imposes certain obligations on the business associates of covered entities that obtain protected health information in providing services to or on behalf of covered entities. HIPAA may apply to us in certain circumstances and may also apply to our business partners in ways that may impact our relationships with them. Our clinical trials are regulated by the Federal Policy for the Protection of Human Subjects, also known as the Common Rule, which also includes specific privacy-related provisions. In addition to federal privacy regulations, there are a number 45 Table of Contents of state laws governing confidentiality and security of health information that may be applicable to our business. In addition to possible federal civil and criminal penalties for HIPAA violations, state attorneys general are authorized to file civil actions for damages or injunctions in federal courts to enforce HIPAA and seek attorney’s fees and costs associated with pursuing federal civil actions. In addition, state attorneys general (along with private plaintiffs) have brought civil actions seeking injunctions and damages resulting from alleged violations of HIPAA’s privacy and security rules. State attorneys general also have authority to enforce state privacy and security laws. Moreover, new laws and regulations governing privacy and security may be adopted in the future as well. There have been several developments in recent years with respect to U.S. state data privacy laws. In 2018, California passed into law the California Consumer Privacy Act, or the CCPA, which took effect on January 1, 2020 and imposed many requirements on businesses that process the personal information of California residents. Many of the CCPA’s requirements are similar to those found in the General Data Protection Regulation, or the GDPR, including requiring businesses to provide notice to data subjects regarding the information collected about them and how such information is used and shared, and providing data subjects the right to request access to such personal information and, in certain cases, request the erasure of such personal information. The CCPA also affords California residents the right to opt-out of “sales” of their personal information. The CCPA contains significant penalties for companies that violate its requirements. In addition, the California Privacy Rights Act, or the CPRA, went into effect on January 1, 2023 and significantly expanded the CCPA to incorporate additional GDPR-like provisions including requiring that the use, retention, and sharing of personal information of California residents be reasonably necessary and proportionate to the purposes of collection or processing, granting additional protections for sensitive personal information, and requiring greater disclosures related to notice to residents regarding retention of information. The CPRA also created the California Privacy Protection Agency, a new enforcement agency whose sole responsibility is to enforce the CPRA, which will further increase compliance risk. In addition to California, 11 other states have passed comprehensive privacy laws similar to the CCPA and CPRA. These laws are either in effect or will go into effect sometime before the end of 2026. Like the CCPA and CPRA, these laws create obligations related to the processing of personal information, as well as special obligations for the processing of “sensitive” data, which includes health data in some cases. Some of the provisions of these laws may apply to our business activities. There are also states that are strongly considering or have already passed comprehensive privacy laws during the 2024 legislative sessions that will go into effect in 2025 and beyond. Other states will be considering similar laws in the future, and Congress has also been debating passing a federal privacy law. There are also states that are specifically regulating health information that may affect our business. For example, the State of Washington passed the My Health My Data Act in 2023 which specifically regulated health information that is not otherwise regulated by the HIPAA rules, and the law also has a private right of action, which further increases the relevant compliance risk. Connecticut and Nevada have also passed similar laws regulating consumer health data, and more states are considering such legislation in 2024, including New York and New Jersey. These laws may impact our business activities, including our identification of research subjects, relationships with business partners and ultimately the marketing and distribution of our products. General data protection regulation Many countries outside of the United States maintain rigorous laws governing the privacy and security of personal information. The collection, use, disclosure, transfer or other processing of personal data, including personal health data, regarding individuals who are located in the European Economic Area, or EEA, and the processing of personal data that takes place in the EEA, is subject to the GDPR, which became effective on May 25, 2018. The GDPR is wide-ranging in scope and imposes numerous requirements on companies that process personal data, and it imposes heightened requirements on companies that process health and other sensitive data, such as requiring in many situations that a company obtain the consent of the individuals to whom the sensitive personal data relate before processing such data. Examples of obligations imposed by the GDPR on companies processing personal data that fall within the scope of the GDPR include providing information to individuals regarding data processing activities, implementing safeguards to protect the security and confidentiality of personal data, appointing a data protection officer, providing notification of data breaches and taking certain measures when engaging third-party processors. The GDPR also imposes strict rules on the transfer of personal data to countries outside the EEA, including the United States, and permits data protection authorities to impose large penalties for violations of the GDPR, including potential fines of up to €20 million or 4% of annual global revenues, whichever is greater. The GDPR also confers a private right of action on data subjects and consumer associations to lodge complaints with supervisory authorities, seek judicial remedies, and obtain compensation for damages resulting from 46 Table of Contents violations of the GDPR. Compliance with the GDPR is a rigorous and time-intensive process that may increase the cost of doing business or require companies to change their business practices to ensure full compliance. Following the Court of Justice of the European Union, or the CJEU, decision, in October 2022, President Biden signed an executive order to implement the EU-U.S. Data Privacy Framework, which would serve as a replacement to the EU-U.S. Privacy Shield. The EU initiated the process to adopt an adequacy decision for the EU-U.S. Data Privacy Framework in December 2022, and the European Commission, or EC, adopted the adequacy decision in July 2023. The adequacy decision permits U.S. companies who self-certify to the EU-U.S. Data Privacy Framework to rely on it as a valid data transfer mechanism for data transfers from the EU to the United States. However, some privacy advocacy groups have already suggested that they will be challenging the EU-U.S. Data Privacy Framework. If these challenges are successful, they may not only impact the EU-U.S. Data Privacy Framework, but also further limit the viability of the standard contractual clauses and other data transfer mechanisms. The uncertainty around this issue has the potential to impact our business. On June 23, 2016, the electorate in the United Kingdom voted in favor of leaving the EU, commonly referred to as Brexit. As with other issues related to Brexit, there are open questions about how personal data will be protected in the United Kingdom and whether personal information can transfer from the EU to the United Kingdom. Following the withdrawal of the United Kingdom from the EU, the United Kingdom Data Protection Act 2018 applies to the processing of personal data that takes place in the United Kingdom and includes parallel obligations to those set forth by GDPR. While the Data Protection Act of 2018 in the United Kingdom that “implements” and complements the GDPR has achieved Royal Assent on May 23, 2018 and is now effective in the United Kingdom, it is unclear whether transfer of data from the EEA to the United Kingdom will remain lawful under the GDPR, although these transfers currently are permitted by an adequacy decision from the EC. The United Kingdom government has already determined that it considers all EU 27 and EEA member states to be adequate for the purposes of data protection, ensuring that data flows from the United Kingdom to the EU/EEA remain unaffected. In addition, a recent decision from the European Commission appears to deem the United Kingdom as being “essentially adequate” for purposes of data transfer from the EU to the United Kingdom, although this decision may be re-evaluated in the future. The United Kingdom and the United States have also agreed to a U.S.-UK “Data Bridge,” which functions similarly to the EU-U.S. Data Privacy Framework and provides an additional legal mechanism for companies to transfer data from the United Kingdom to the United States. In addition to the United Kingdom, Switzerland is also in the process of approving an adequacy decision in relation to the Swiss-U.S. Data Privacy Framework (which would function similarly to the EU-U.S. Data Privacy Framework and the U.S.-UK Data Bridge in relation to data transfers from Switzerland to the United States). Any changes or updates to these developments have the potential to impact our business. Beyond GDPR, there are privacy and data security laws in a growing number of countries around the world. While many loosely follow GDPR as a model, other laws contain different or conflicting provisions. These laws will impact our ability to conduct our business activities, including both our clinical trials and any eventual sale and distribution of commercial products. Employees and Human Capital Resources As of March 25, 2024, we had 73 full-time employees, including 32 employees with M.D., Pharm.D. or Ph.D. degrees. Of these full-time employees, 53 were engaged in research and development activities and 20 were engaged in general and administrative activities. None of our employees is represented by a labor union or covered by a collective bargaining agreement. We consider our relationship with our employees to be good. In March 2024, as part of a strategic portfolio reprioritization, we announced plans to undergo a workforce reduction to further reduce our expenses and streamline our operations, including a reduction in headcount of 15 employees, representing approximately 21% of our workforce prior to the workforce reduction. We anticipate that the workforce reduction will be substantially completed in the first half of 2024. Our human capital resources objectives include, as applicable, identifying, recruiting, retaining, incentivizing and developing our existing and additional employees. We are committed to diversity, equity and inclusion across all aspects of our organization, including in our recruitment, advancement and development practices. Each year, we review employee demographic information to evaluate our diversity efforts across all functions and levels of the company. We conduct 47 Table of Contents annual performance and development reviews for each of our employees to discuss the individual’s strengths and development opportunities, career development goals and performance goals. We also regularly survey employees to assess employee engagement and satisfaction. In addition, each regular full-time employee is provided an allowance and time to attend appropriate job-related trainings and other professional development courses, seminars, meetings, and similar sessions. The principal purposes of our equity incentive plans are to attract, retain and motivate selected employees, consultants and directors through the granting of stock-based compensation awards. We value our employees and regularly benchmark total rewards we provide, such as short- and long-term compensation, 401(k) contributions, tuition reimbursement, health, welfare and quality of life benefits, paid time off and personal leave, against our industry peers to ensure we remain competitive and attractive to potential new hires. Corporate Information We are a Delaware corporation that was incorporated on June 18, 2020 under the name Xilio Therapeutics, Inc. We maintain a website at the following address: www.xiliotx.com. The information contained on, or that can be accessed through, our website is not incorporated by reference into this Annual Report on Form 10-K or in any other report or document we have filed or may file with the Securities and Exchange Commission, or SEC, and any reference to our website address is intended to be an inactive textual reference only. We make available on or through our website certain reports and amendments to those reports that we file with or furnish to the SEC in accordance with the Securities Exchange Act of 1934, as amended, or the Exchange Act. These include our Annual Reports on Form 10-K, our Quarterly Reports on Form 10-Q and our Current Reports on Form 8-K. We make this information available on our website (free of charge as soon as reasonably practicable after we electronically file the information with, or furnish it to, the SEC. In addition, we routinely post on the “Investors & Media” page of our website investor and scientific presentations, SEC filings, press releases, public conference calls and webcasts and other statements about our business and results of operations, some of which may contain information that may be deemed material to investors. Accordingly, investors should monitor these portions of our website, in addition to following our press releases, SEC filings, public conference calls and webcasts, as well as current or future social media channels (including LinkedIn). This list of channels may be updated from time to time on our investor relations website and may include other social media channels than the one described above. The contents of our website or these channels, or any other website that may be accessed from our website or these channels, shall not be deemed incorporated by reference in any filing under the Securities Act of 1933, as amended. The SEC maintains a website that contains reports, proxy and information statements, and other information regarding issuers that file electronically with the SEC at the following address: http://www.sec.gov. 48 Table of Contents