Item 1. Business.

Overview

We are a clinical-stage biopharmaceutical company developing proprietary antibody therapeutics intended to engage the immune system to treat both solid tumors and hematological malignancies. Our immuno-oncology product candidates include a clinical-stage monoclonal antibody targeting solid tumors, a novel bispecific targeting PD-1 and PD-L1, and a portfolio of bispecific and monoclonal antibodies at various stages of pre-clinical development. These product candidates are designed to address three critical components required for an effective immune response to cancer: induction of a potent innate immune response; activation of the adaptive immune system; and alleviation of immunosuppressive mechanisms used by tumors to evade immune surveillance and activation. We plan to advance our product candidates through clinical development either as standalone therapies or in combination with existing therapies as long as their continued development is supported by clinical and nonclinical data.

Our lead product candidate, CTX-471, is a monoclonal antibody agonist of CD137, a key co-stimulatory receptor on immune cells. In preclinical studies, we observed that CTX-471 led to complete eradication of large tumors in mice when dosed as a monotherapy. In treated mice, dosing with CTX-471 was associated with extensive reprogramming of the tumor microenvironment, resulting in increased survival and long-term immune protection. Long after therapy had been completed, after more than eight half-lives of the antibody, treated mice exhibited immune memory that prevented reestablishment of the same tumor. Based on these and other preclinical results, in July 2019 we initiated a Phase 1 trial evaluating the safety and tolerability of CTX-471 as a monotherapy in oncology patients who were previously treated with PD-1 or PD-L1 immune checkpoint inhibitors and subsequently relapsed or progressed after a period of stable disease. The design of this trial includes a dose escalation stage (Phase 1a) followed by a dose expansion stage (Phase 1b). The dose escalation stage of the Phase 1 trial has been completed and CTX-471 was observed to be generally well-tolerated. The dose expansion stage of the trial is currently ongoing and, as of February 28, 2021, 11 patients have received at least one dose of CTX-471. Of the 11 patients treated so far, six patients have reached their first tumor evaluation at week 9, of which five had stable disease. Subsequently, one of those patients who has advanced small cell lung cancer had a partial response at Week 17. As of February 28, 2021, there have been no treatment-related serious adverse events, or SAEs, in the Phase 1b dose expansion stage of the trial. We expect to complete the Phase 1b stage of the trial during the second half of 2021 and to initiate a Phase 2/3 trial of CTX-471 in the second half of 2022.

Pending the results of our Phase 1 monotherapy trial of CTX-471, we plan to initiate a second Phase 1 trial of CTX-471 in combination with trastuzumab, marketed as Herceptin^® by Genentech, in selected human epidermal growth factor receptor 2, or Her2, positive tumors and with cetuximab, marketed as Erbitux^® by Eli Lilly, in epidermal growth factor receptor, or EGFR, positive tumors. We could submit an IND application for this combination in the second half of 2021.

Our second product candidate, CTX-8371, is a bispecific antibody that simultaneously targets both PD-1 and PD-L1, the targets of well-known and widely used checkpoint inhibitor antibodies. Single inhibitors of PD-1 or PD-L1 include some of the highest-revenue-generating therapeutics in history and have been approved for the treatment of a wide range of tumors. There is no marketed therapy that combines inhibition of both PD-1 and PD-L1 in the same molecule and, in CTX-8371, we are developing one. We discovered CTX-8371 using our StitchMabs^TM technology when we screened for the best antibody to pair with our proprietary PD-1 blocker. Additional studies demonstrated that CTX-8371 works via a novel mechanism of action not shared by single PD-1 or single PD-L1 blockers. We have shown in animal models that CTX-8371 was associated with greater antitumor activity than a single PD-1 inhibitor, a single PD-L1 inhibitor or a combination of the two. IND-enabling studies with CTX-8371 were initiated in August 2020. We are targeting an IND submission for CTX-8371 in early 2022 and we could deliver early safety and top-line data later in 2022.

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In addition to CTX-471 and CTX-8371, we are also developing a portfolio of bispecific and monoclonal antibody product candidates, which are currently in preclinical development. These programs all derive from our in-house antibody discovery and development platforms.

Our approach is based on the observation that traditional methods of antibody discovery are slow, inefficient, and are limited by lack of diversity of antigenic sites, or epitopes, that are recognized using these methods. We believe these limitations impair drug developers’ ability to identify the best product candidates. We have created several technological solutions that are designed to address the key challenges in antibody development with the goal of incorporating our solutions into bispecific product candidates. First, we developed and acquired several complementary platforms that enable us to generate antibodies with a high level of epitope diversity and excellent physical and biochemical properties. Second, we have developed sophisticated technologies to screen our antibody sets in functional biological assays designed to prioritize antibodies with desirable biological activities. Third, we have developed our proprietary StitchMabs^TM technology that allows us to rapidly evaluate the potential of the antibodies we discover in a bispecific antibody format.

We have also developed a proprietary transgenic mouse line that produces antibodies with the differentiated property that they all share a human common light chain. We imposed this restriction at the earliest stage of our bispecific antibody discovery process in anticipation of the need to simplify the manufacturing of our bispecific product candidates. Sharing a common light chain enables our bispecific antibodies to be manufactured using a well-established process that has been successfully used by the biopharmaceutical industry to produce monoclonal antibodies at commercial scale, thereby avoiding the complexities associated with the manufacture of bispecific products that lack this property. We found that imposing this restriction on the construction of the antibody pool did not hinder our ability to obtain highly potent and selective antibodies.

In addition to our development of antibody product candidates for immuno-oncology, we have also leveraged our proprietary platform technologies to generate and identify monoclonal antibodies and bispecifics that suppress immune response, which we are evaluating as therapies for autoimmune indications. Several of these programs are currently undergoing characterization and in vitro and in vivo testing.

We have recently conducted a review of our pipeline and have made the strategic decision to deprioritize the development of our NKp30 innate cell engager platform. Along with this decision, we have discontinued the efforts to advance CTX-8573 to IND-enabling studies.

Our management team has a successful record of building and growing biotechnology companies. Our Chief Executive Officer and co-founder, Thomas J. Schuetz, M.D., Ph.D. has over 20 years of experience in oncology, biopharmaceutical drug development and life science venture investing. Prior to co-founding Compass Therapeutics, Dr. Schuetz was a venture partner with OrbiMed Advisors LLC where he participated in OrbiMed’s investments in Enobia Pharma (sold to Alexion), Relypsa (sold to Galenica), Arteaus Therapeutics (sold to Eli Lilly), and Audentes (sold to Astellas) and served on the board of each of these companies. Dr. Schuetz was also the chief medical officer of Therion Biologic Corporation and was vice president of clinical affairs at Transkaryotic Therapies, a company acquired by Shire.

Our President and Chief Operating Officer, Vered Bisker-Leib, Ph.D., M.B.A., has over 18 years of experience in strategy, business development, finance and operations of biotechnology and pharmaceutical companies. Prior to joining Compass Therapeutics, she served as an entrepreneur-in-residence with Atlas Venture. Previously, Dr. Bisker-Leib was chief business officer of Cydan, a biotech accelerator, where she co-founded IMARA, Inc. and other biotech companies focused on therapies addressing rare diseases and served as an executive director and global head of business development for the cardiovascular and metabolic franchises of Bristol-Myers Squibb.

Our investors include leading life science venture and institutional funds led by OrbiMed, F-Prime Capital, Cowen Healthcare Investments, Biomatics Capital, Consonance Capital and Borealis Ventures.

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Pipeline

The figure below details our pipeline of product candidates, including our lead product candidate, CTX-471, our bispecific product candidate, CTX-8371, and our other discovery stage programs.

Our Strategy

Our goal is to expand and extend the role of the immune system in fighting cancer with antibody-based therapies. We believe our approach can be applied both to solid tumors as well as to hematologic malignancies. Our strategy to achieve this goal includes:

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Our approach

We are focused exclusively on modulation of the immune system through the development of novel antibody therapeutics. Antibodies are structurally distinct Y-shaped proteins formed through the pairing of two long proteins, called heavy chains, and two short proteins, called light chains. Each heavy and light chain pair forms a binding site where the antibody specifically binds its target, which is also known as an antigen.

The immune system is capable of not only fighting foreign invaders, but also of recognizing and eliminating a human body’s own cells that have become pathogenic after transformation, such as in cancer. There are two broad classes of antibodies used in cancer therapy. The majority of antibodies directly target the tumor or its surroundings. The more recent class consists of antibodies that modulate the immune system leading to immune- mediated killing of tumors. These antibody drugs mainly exert this effect via a single modulation of the immune system. We believe that modulation of more than one function of the immune system simultaneously has the potential to improve the therapeutic benefit and utility of immuno-oncology therapies.

Antibodies can be generated in many ways, and multiple companies claim to possess proprietary antibody discovery platforms, each with specific advantages. Our antibody platform was designed with a broad set of capabilities and resources that we can leverage with the goal of generating a portfolio of highly distinct bispecific products.

Our approach to bispecific antibody discovery encompasses four principles:

Antibody diversity

We obtain our initial pools of antibodies from multiple internally-developed platforms, including our custom phage display library and our transgenic mouse line. We constructed our phage display library based on the peripheral B cell diversity of 70 healthy human donors. This system allows us to generate large and highly diverse sets of antibodies that are fully human; target multiple epitopes on a target of interest; and possess excellent physical and biochemical properties. We describe these antibodies as having good ‘drug-like’ properties. To generate additional antibody candidates, we can also immunize a proprietary line of humanized transgenic mice with antigens of interest to isolate a diverse set of fully human antibodies that share a common human light chain, but distinct native mouse heavy chains. We estimate that the pool of antibodies from these two platforms represents over 10¹⁰ unique sequences.

We express libraries of antibodies against any particular target using our Human Display technology which streamlines the expression of functional antibodies such that each cell expresses only one antibody clone. We then further screen our diverse sets of antibodies expressed with our Human Display

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technology to fine-tune for specificity. Sequence changes can be readily introduced to further optimize leads from our screens.

Our ability to generate viable antibody candidates, with good drug-like properties and high manufacturability potential in a high-throughput manner has enabled us to rapidly assemble a portfolio of proprietary antibodies to over 40 key innate and adaptive immune targets and tumor antigens. This portfolio of antibodies is designed to provide us with a set of well-characterized antibodies that can be incorporated into our combinatorial bispecific antibody screening platform.

Figure 1. We have discovered proprietary antibodies that modulate two key components of the immune system: innate immunity and adaptive immunity as well as antibodies to selected antigens on tumor cells. This expansive collection of antibodies allows us to use our proprietary technologies to uncover unexpected synergies.

Functional screening

A critical part of our antibody discovery process is our ability to produce sufficient quantities of purified antibodies to assess their biological activities both in cells and, in some cases, animal models. Our human display technology allows us to efficiently express full-length antibodies on cell surface, thereby facilitating the high throughput screening of our antibodies across multiple functional screens. While we do assess standard biochemical parameters such as binding affinity and specificity as part of the initial screening of our candidate sets, we note that activity in a complex biological system cannot be predicted based on physical and biochemical parameters alone. We have shown with CTX-471, for example, that activity in a complex biological system cannot necessarily be predicted on strictly biochemical parameters.

StitchMabs^TM technology

A natural antibody recognizes a single target antigen and is therefore monospecific. Because a natural antibody features two identical binding sites, it is considered bivalent for that target. Although natural antibodies recognize a single target antigen, it is possible to engineer antibodies so that their two binding sites bind two different targets. The construction of a bispecific antibody typically requires a significant investment in cloning, construct optimization, protein expression, and protein purification before the therapeutic potential of any particular bispecific antibody can be assessed. In practice, these requirements mean that the diversity of antigen pairs targeted by bispecific antibodies is limited, and development is oftentimes prioritized for antigen pairs suggested by existing scientific literature.

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Our proprietary StitchMabs^TM technology is a novel screening approach which we developed to assess the potential of any pair of antigen-binding sites in a bispecific antibody format. This combinatorial antibody-linking technology stably and irreversibly attaches a second pair of antigen-binding domains to a standard antibody during a 15-minute incubation at room temperature. The resulting stitched antibody acts structurally and functionally like a bispecific antibody.

StitchMabs^TM allows us to assess our large library of antigen-binding domains in combinatorial fashion. Once we have generated and purified large numbers of bispecific candidates, we then assess the potential of these candidates in functional assays and determine whether these bispecifics have additive, reductive or synergistic activity. Screening of these bispecific molecules in functional assays has led us to discover novel product candidates with unexpected synergistic activity in cellular and animal models.

Our common light chain platform greatly simplifies manufacturing

The embedded common light chain feature in our antibodies greatly simplifies the manufacture of our bispecific product candidates. Most antigen-binding domains of antibodies are composed of a heavy chain and a light chain that have been optimized together to recognize a specific antigen. If these two chains are expressed independently, as is the case with most antibody manufacturing processes, they are often reassembled in various ways, leading to heterogenous mixture of the desired product along with peptide segments corresponding to two heavy chains and two light chains. Separation of the desired product from the mixture is a technically challenging and expensive process. We address this challenge by including only common light chain compatible antibodies as part of our antibody discovery process for potential incorporation into bispecifics. The variability in the antigen-binding domain of our antibodies in the heavy chain is sufficient to generate a diverse, potent, selective, and functionally active set of antibodies. We further simplified the manufacturing of our bispecific antibodies by assembling a single heavy chain construct that encodes both antigen-binding domains. As a result, the manufacturing of our bispecifics closely resembles that of standard monoclonal antibodies, which include—one heavy chain and one light chain. Our focus on common light chain antibodies simplifies the process of converting our StitchMabs^TM screening candidates into bispecific antibody product candidates.

Figure 2. A common light chain simplifies the production of bispecific antibodies

CTX-471, a monoclonal antibody targeting CD137

CTX-471, our monoclonal antibody product candidate, is an agonist of CD137, a key co-stimulatory receptor on immune cells. Binding of CTX-471 to CD137 leads to ligand-stimulated activation of T-cells and NK cells. In tumor models, treatment with CTX-471 as a monotherapy led to recruitment and activation of immune cells in the tumor microenvironment. In the treated mice, dosing with CTX-471 led to extensive reprogramming of the tumor microenvironment, including increased recruitment of immune cells, reversion of exhausted cytotoxic CD8+ T-cells, reductions in immunosuppressive regulatory T-cells, and reductions in immunosuppressive tumor- associated macrophages. Long after the completion of the

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treatment with CTX-471, a period described as eight half-lives of the antibody, treated mice exhibited immune memory that prevented reestablishment of the same tumor.

In July 2019, we initiated a Phase 1 trial evaluating CTX-471 as a monotherapy in oncology patients who were previously treated with a PD-1 or PD-L1 immune checkpoint inhibitor and subsequently relapsed or progressed after a period of stable disease. The design of this trial includes a Phase 1a dose escalation stage followed by a Phase1b dose expansion stage. The Phase 1a dose escalation stage has been completed and the Phase 1b dose expansion stage is ongoing.

Overview of NSCLC

According to the World Health Organization, an estimated 1.8 million people worldwide die of lung cancer each year, which accounts for approximately 18% of all cancer deaths, making lung cancer the leading cause of cancer-related death. In the United States, there are an estimated 228,000 newly diagnosed cases of lung cancer and approximately 137,000 deaths annually. NSCLC accounts for approximately 80%-85% of lung cancer cases. The treatment paradigm for NSCLC has significantly changed over the past few years. Previously, patients were primarily treated with radiation therapy or combinations of cytotoxic drugs. Recent advancements have led to the development of targeted therapies based on blockade of alteration in mutated genes, such as EGFR, anaplastic lymphoma kinase gene, or ALK, ROS1 or BRAF. Up to two thirds of advanced or metastatic NSCLC patients who are ineligible for or resistant to treatment with targeted therapies have tumors that express PD-L1 and are candidates for checkpoint inhibitor therapies, which lead to significant improvements in progression free survival and overall survival compared to standard chemotherapy. Despite the availability of these therapies, the prognosis in NSCLC remains poor, with an overall five-year survival for all patients diagnosed with NSCLC of 19%. In the KEYNOTE-042 trial in treatment naïve metastatic NSCLC patients, conducted by Merck from December 2014 to March 2017, treatment with pembrolizumab as monotherapy led to partial responses in 27% of patients and complete responses in 0.5%. The duration of response in the majority of the patients was less than one year. We believe there remains significant unmet medical need in this patient population that could be addressed with novel antibody therapeutics.

Role of CD137 in immunology

CD137, also known as 4-1BB and TNFRSF9, is an inducible co-stimulatory receptor expressed on T-cells and NK cells. Activation of CD137 triggers a signaling cascade that results in upregulation of antiapoptotic molecules, cytokine secretion and enhanced cell killing function. On NK cells, CD137 signaling can increase antibody-dependent cell-mediated cytotoxicity, or ADCC.

When antigen-presenting cells, such as dendritic cells, express CD137L or 4-1BBL, the natural ligand for CD137, they induce increases in the levels of CD137 on T-cells. Tumors with a high tumor mutation burden are enriched in these antigen-presenting cells and such tumors represent promising opportunities to improve on standard of care checkpoint inhibitors by adding antibody therapies directed against CD137.

Historically, across preclinical cancer models, agonist antibodies targeting CD137 have been immunotherapeutic agents that showed great promise. In the clinic, however, these agents have been hampered, in part by dose-limiting toxicities, as seen with urelumab, and, in part by weak agonist activity, as seen with utomilumab.

Our product candidate, CTX-471

CTX-471 is a fully human, IgG4 monoclonal antibody that is an agonist of the CD137 receptor. We selected CTX-471 from among a panel of CD137 antibodies based on multiple preclinical parameters. The CD137 antigenic site recognized by CTX-471 does not block the binding of CD137 ligand and is differentiated from the site recognized by CD137 antibodies from competitors. We designed and made the antibody using different backbones and chose to use a human IgG4 backbone for CTX-471 to enable

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engagement of Fc receptors Fc_gRI and Fc_gRIIb to facilitate CD137 cross-linking while avoiding binding to Fc_gRIIIa and depletion of immune effector cells through ADCC.

Identification through functional screening

We evaluated a panel of anti-CD137 antibodies as potential candidates for CTX-471 and used a series of in vitro and in vivo functional assays to screen for the best candidate. One of the most stringent assays was antitumor activity in a CT26 mouse colon carcinoma model in which tumors were allowed to grow to 500 mm3 before CTX-471 candidates were administered. Tumors of this size are generally considered futile to treat and are highly resistant to monotherapy with other immuno-oncology therapies such as checkpoint inhibitors.

Figure 3. Preclinical antitumor activity evaluation of CTX-471 was conducted in syngeneic mice with 500 mm³ CT26 tumors

We observed that multiple CTX-471 candidates exhibited activity treatments in this model, leading to the complete eradication of these large tumors when dosed as monotherapy. Certain antibody candidates exhibited greater activity than others and there was not a strict correlation between potency for the CD137 antigen and antitumor activity. We selected the antibody candidate that became CTX-471 based on a combination of in vivo and in vitro properties. We also tested antibodies that target PD-1, PD-

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L1, CTLA-4 and OX-40 in the CT26 model alongside CTX-471 and observed that these antibodies failed to generate similar responses in this model.

Figure 4. CTX-471a, CTX-471b and CTX-471c are three CD137 agonistic antibodies with low, intermediate and high affinity to CD137 respectively. Four groups of CT26 syngeneic mice models were dosed with control antibody, CTX-471a, CTX-471b and CTX-471c. Treatment initiated when tumors reached 500 mm³. CTX-471b exhibited the most activity, eradicating tumors in 6/6 mice, followed by CTX-471a and CTX-471c, which eradicated tumors in 4/6 mice each, and none in the control group.

Immunoregulatory role

Treatment of mice with CTX-471 stimulated long-term immunological memory. In order to assess the long-term immunological memory, we tested tens of mice cured of their initial tumors by CTX-471 monotherapy to a re-challenge with the same tumor. Upon a re-challenge, these mice have all demonstrated resistance to establishment of new tumors. To investigate whether this observed effect may be explained by residual CTX-471, we have conducted some of these re-challenge experiments 88 days after dosing, or greater than eight half-lives of CTX-471. We believe that, in mice previously cured of CT26 tumors by CTX-471, the inability to establish CT26 tumors is consistent with the ability of CTX-471 to induce long-term immune memory capable of rejecting the reintroduced tumor cells.

Figure 5. All mice cured by CTX-471 treatment were resistant to re-challenge with the same tumor

Immune cell depletion experiments showed that the activity of CTX-471 required the presence of CD4+ T-cells, CD8+ T-cells, and NK cells, indicating a coordinated involvement of both innate and adaptive immune cells. Encouragingly, treatment of tumors in mice with CTX-471 led to a marked reprogramming of the immune component of the tumor microenvironment. CTX-471-treated mice had over three times more tumor infiltrating immune cells than control mice. Of the CD8+ T-cells in these tumors, there was a reduction of exhausted T-cells, determined by the reduction of CD8+ T-cells that express both PD-1 and TIGIT, from 43% to 8%. Similarly, treatment with CTX-471 led to a sharp decline

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in immunosuppressive regulatory T-cells, or Tregs, from 31% to 7%. We also observed that tumors treated with CTX-471 had an approximate two-fold reduction in the number of immunosuppressive tumor-associated macrophages.

Figure 6. CTX-471 altered the immune composition in the tumor microenvironment

We believe that the ability of CTX-471 to transform the tumor microenvironment through the combined action of immune cell recruitment, alleviation of T-cell exhaustion, suppression of Tregs, and reduction of tumor suppressing macrophages is what drives CTX-471’s antitumor activity in mouse models. We believe that CTX-471 has the potential to affect the same aspects of the immune system in cancer patients in the clinic, which could lead to improved patient outcomes.

In addition to testing CTX-471 in the CT26 syngeneic mouse model described above, we have also tested CTX-471 as a monotherapy in multiple other syngeneic tumor models of different histologies and have observed potent activity, including various levels of tumor eradication. CTX-471 has demonstrated activity and led to tumor eradication in the A20 model of lymphoma, the MC38 model of colon carcinoma, and in the EMT6 model of breast cancer. We believe that this broad biological activity across multiple tumor models of different histologies suggests that CTX-471 might benefit patients with different tumor types.

Phase 1 clinical trial of CTX-471

We are currently conducting a Phase 1 clinical trial of CTX-471 in adult patients who have achieved three months of stable disease or better after treatment with PD-1/PD-L1 checkpoint therapy and who have subsequently relapsed or progressed. We selected this population of patients for this trial because multiple clinical trials and meta-analyses have shown that not all patients respond to checkpoint inhibitor therapy due to many possible reasons. By focusing on those that did previously respond to checkpoint inhibitor therapy, we believe that this trial design enriches for patients who have tumors that are capable of being recognized and killed by their immune systems. We believe that disease progression after the initial checkpoint inhibitor response is likely due to an increase in immunosuppressive activity that CTX-471 has the potential to overcome.

This Phase 1 trial is an open-label multiple ascending dose, dose-escalation trial. After a period of 28 days to allow checkpoint inhibitors and other drugs to be eliminated from the body, each patient

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receives CTX-471 by intravenous infusion every two weeks as monotherapy. Disease progression is measured by CT scans every eight weeks. We collect blood samples to assess standard safety biomarkers as well as cytokines and potential pharmacodynamic biomarkers. Baseline tumor biopsies are also collected for retrospective analyses.

The primary objective of the Phase 1a dose escalation stage of the trial was to assess the safety and tolerability of CTX-471 monotherapy at various doses. The goal of the Phase 1b dose expansion stage is to determine an optimized dose for future clinical trials. Secondary endpoints include measures of overall response rate and progression-free survival, among others.

Dosing strategy

In contrast to dosing strategies for other immuno-oncology antibodies, such as checkpoint inhibitors where the goal is often to deliver a dose that is capable of fully inhibiting the receptor at all times, our dose selection for this trial is aimed at binding to only a fraction of the available CD137 receptors. Dosing of an agonist antibody, such as CTX-471, at levels capable of binding to the majority of receptors can lead to inappropriate cell activation and downregulation of the receptor and overall weaker activity.

Agonist antibodies typically trigger their activity through independent binding of each of their two antigen-binding domains to individual receptors on a cell surface. This binding to both receptors at once forces the receptors into close physical proximity. This grouping of receptors that drives receptor activation, especially when the ratio of antibody molecules to receptor molecules is relatively low. As the ratio of antibody to receptor increases, the level of receptor activation increases up to a point above which activation may decrease due to down-regulation of the receptors. This results in a bell-shaped activation curve in which maximal activation occurs at intermediate antibody concentrations.

We observed evidence of the importance of lower receptor occupancy while screening candidate antibodies against CD137. The antibodies with the greatest tumor-killing activity were the ones with intermediate potency. Very high-potency antibodies had weaker antitumor activity.

Consistent with the finding of lower activity at high antibody to receptor levels, we observed that the antitumor activity of CTX-471 appeared to peak at doses between 50 ug and 100 ug in the mouse CT26 tumor model. At the higher dose of 200 ug, the number of complete responses, four out of eight mice, was less than that observed at 100 ug, seven out of eight mice, suggesting that the optimal receptor occupancy had been exceeded. This is also consistent with our observation that intermediate affinity antibodies exhibited greater antitumor activity compared to high affinity antibodies.

Figure 7. Antitumor activity of CTX-471 is optimized at intermediate dose and decreased at the highest dose level

Our findings are consistent with those reported for an agonist antibody against OX40, another immune target in oncology. Thus, for many agonist antibodies, it is likely that both intermediate affinities and intermediate doses will deliver optimal activity.

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Phase 1 clinical trial data

We are conducting a Phase 1 trial of CTX-471 in patients with metastatic or locally advanced solid tumors whose tumors have progressed while receiving an approved PD-1 or PD-L1 inhibitor after a period of stable disease. The design of this trial includes a dose escalation stage (Phase 1a) followed by a dose expansion stage (Phase 1b). Our selection of doses in the Phase 1a stage of the trial was informed by multispecies pharmacokinetics and by the intent to select doses capable of maintaining receptor occupancy between 20% and 80% in tumors.

Figure 8. The number of patients dosed with CTX-471 in the Phase 1a dose escalation stage

CTX-471 was observed to be generally well-tolerated in the Phase 1a stage of the trial. There were two SAEs determined to be treatment-related, which included one hypoxia event that resolved with approximately one day of supplemental oxygen therapy and one immune thrombocytic purpura event that also resolved. The dose-limiting toxicities were two events of thrombocytopenia in Cohort 4, which was expanded from three to six patients to collect additional safety data. Based on these results, 0.6 mg/kg was determined to be the maximum tolerated dose.

While the goal of the Phase 1a stage of the trial was to evaluate the safety and tolerability of CTX-471, we also collected data from these patients to evaluate the pharmacokinetics of CTX-471, the potential development of anti-drug antibodies of CTX-471, and to obtain certain efficacy data, based on the objective response rate, or ORR, as per Response Evaluation Criteria in Solid Tumors, RECIST. Patients who were enrolled in the Phase 1a stage of the trial have been evaluated every eight weeks by imaging techniques, such as MRI or CT, until disease progression or withdrawal from the trial, in order to collect such data.

The Phase 1a stage of the trial is now complete. None of the patients enrolled in the Phase 1a stage of the trial had a complete response or a partial response by RECIST. The best overall response has been stable disease. Two patients with NSCLC had stable disease until progression at Weeks 25 and 41, respectively. In addition, one patient with metastatic melanoma of mucosal origin had an approximately 24% decline in the total size of his measured metastatic tumors (target lesions) at week 33. This patient remained on study and received CTX-471 for 49 weeks.

We have analyzed preliminary pharmacokinetic data from the trial and these data have confirmed our receptor occupancy modeling. Based on this modeling and the correlation of the observed pharmacokinetics with our predictions, we selected 0.3 mg/Kg and 0.6 mg/Kg as the doses of the cohorts of our Phase 1b stage of the trial. We estimate that a dose of 0.3 mg/kg would lead to a peak receptor occupancy of approximately 50% and a dose of 0.6 mg/kg would lead to a peak receptor occupancy of approximately 70%.

Phase 1b - Dose Expansion

In September 2020, we enrolled the first patient in the Phase 1b dose expansion stage of the trial. As of February 28, 2021, 11 patients have received at least one dose of CTX-471. Of the 11 patients treated so far, six patients have reached their first tumor evaluation at week 9, of which five had stable disease. Subsequently, one of those patients who has advanced small cell lung cancer had a partial response at Week 17. As of February 28, 2021, there have been no treatment-related SAEs in the Phase

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1b dose expansion stage of the trial.  This Phase 1b dose expansion stage of the trial is intended to inform the Phase 2 recommended dose.

Subject to the results of our Phase 1 monotherapy trial of CTX-471 and the receipt of additional funding, we also plan to initiate a second Phase 1 trial of CTX-471 in combination with trastuzumab, marketed as Herceptin^® by Genentech, in Her2 positive tumors, and with cetuximab, marketed as Erbitux^® by Eli Lilly, in EGFR positive tumors.

Potential market opportunity for CTX-471

In preclinical studies, CTX-471 was associated with antitumor activity as a monotherapy in multiple syngeneic tumor models, including colon carcinoma, lymphoma, and breast cancer. This broad biological activity suggests that CTX-471 may have benefit as a therapy for patients with different tumor types.

We seek to maximize the potential value of each of our product candidates, if any, across all indications in which it may demonstrate promising clinical results and receives marketing approval. While we have not selected a specific target indication for CTX-471, as an example for the potential size of the market opportunity for CTX-471 in one of those potential target indications, we have modeled the positioning of CTX-471 as a second line therapy for advanced/metastatic NSCLC.

In the United States, there are 228,000 lung cancer patients each year, of those 80-85% have NSCLC. Patients with stage 0-2 NSCLC are treated with surgery or a combination of surgery and chemotherapy, which are generally effective. However, some patients will progress to the later stages of the disease, and other patients already have locally advanced or metastatic disease at the time of diagnosis. There are approximately 90,000 patients with advanced/metastatic NSCLC per year who are in great need of pharmacological treatment.

In the 1^st line setting, the majority of the advanced/metastatic NSCLC patients without defined point mutations are treated by either PD-1 blocker alone or PD-1 blocker combination with chemotherapy, depending on PD-1 expression levels. Patients who do not respond to the 1^st line settings have very limited therapeutic options, mostly comprising chemotherapy combinations, with or without checkpoint blockers. We estimate that there are approximately 36,000 patients in this category who will progress after 1^st line treatment to 2^nd line setting as depicted in the diagram below.

Figure 9. Estimate of the number of treatment-eligible advanced/metastatic NSCLC patients based on NCCN guidelines and other Compass analysis.

CTX-8371, a PD-1 x PD-L1 bispecific antibody

CTX-8371 is a bispecific antibody that binds to both PD-1 and PD-L1. Preclinical studies demonstrate that CTX-8371 has the ability to outperform PD-1, PD-L1, and combinations of the two to

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activate T-cells in in vitro assays. In mouse xenografts, treatment with CTX-8371 led to significantly greater tumor growth control and longer survival than treatment with a PD-1 inhibitor alone, a PD-L1 inhibitor alone or the combination of PD-1 and PD-L1 inhibitors. IND-enabling studies on CTX-8371 were initiated in August 2020.

Figure 10. CTX-8371 is a PD-1 x PD-L1 bispecific antibody

Overview of PD-1 and PD-L1 checkpoint inhibitors

PD-L1 is a surface protein that is overexpressed by over 35% of certain types of cancer, such as melanoma, hepatocellular carcinoma, colorectal cancer, and NSCLC. Binding of PD-L1 to its receptor, PD-1, on immune T-cells leads to suppression of cytotoxic CD8+ T-cells preventing immune attack of the tumor. Multiple inhibitors of PD-1 and PD-L1 have been approved as therapies for a broad range of tumors including melanoma, NSCLC, small cell lung cancer, head and neck squamous cell cancer, renal cell carcinoma, bladder cancer; gastric cancer, cervical cancer; and other cancers with microsatellite instability or mismatch repair deficiency. While PD-1/PD-L1 checkpoint therapies have resulted in remarkable clinical efficacy across multiple cancer types, their efficacy, even in tumors with high immunogenicity, is limited to approximately 20% of patients. Nevertheless, sales of checkpoint therapies in 2019 were estimated to be $22 billion. There is no approved therapy that combines inhibition of both PD-1 and PD-L1 in the same molecule.

Discovery and preclinical activity of CTX-8371

The desire to improve the efficacy of PD-1/PD-L1 inhibitors has sparked multiple attempts to create bispecific antibodies in which one antigen binding site targets PD-1 or PD-L1 and the other targets immuno-oncology receptors such as CTLA-4 or LAG-3. In contrast to those bispecific efforts described by others that have focused on a single pair of antigen-binding domains at a time, we have applied our StitchMabs^TM technology to broadly screen for pairs of bispecific antigen-binding domains with the highest potential to generate antitumor activity. Our efforts were enabled not only by the StitchMabs^TM technology, but also by our investment in generating a broad portfolio of selective antibodies to 40 potential immune targets across the innate and adaptive immune system.

We designed our combinatorial screen such that one antigen-binding domain was directed against PD-1, and the other selected from our library of candidate antibodies. We screened these StitchMabs^TM bispecific constructs in T-cell activation assays in the presence of PD-L1 expressing cells. Our unbiased screening led us to an antibody that pairs a PD-1 binding domain and a PD-L1 binding domain. This novel bispecific antibody contributed to T-cell activation that outperformed the activation observed in response

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to treatment with PD-1-only antibodies. We designated CTX-8371 as the bispecific antibody we constructed using our common light chain antibodies having a PD-1 and PD-L1 antigen binding domains.

Figure 11. A PD-1 x PD-L1 bispecific antibody outperformed single PD-1 antibodies in a T-cell activation assay

The observation that the combination of a PD-1 and PD-L1 antibody into a bispecific antibody would be hundreds to thousands fold more potent in a T-cell activation assay than a PD-1 antibody alone was unexpected. A simple model would suggest that inhibiting either PD-1 or PD-L1 should have approximately equal effects in this assay and there would be no advantage to inhibiting both. Further investigation into the mechanism of CTX-8371 found that it led to T-cell activation through four mechanisms:

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Figure 12. Differentiated mechanism of action of CTX-8371 drives enhanced T-cell activation

We also found that the greater activity of CTX-8371 in our T-cell activation assay compared to PD-1 inhibition also extended to PD-L1 inhibition. Furthermore, CTX-8371 was associated with significantly more antitumor activity in a murine B16F10 melanoma model than was monotherapy with either a PD-1 inhibitor or a PD-L1 inhibitor or combination of both. Tumor growth in monotherapy-treated mice and in the combination PD-1 and PD-L1-treated mice was slowed to approximately half that observed with tumors in untreated mice. In contrast, tumor growth was essentially stopped by the CTX-8371 bispecific antibody. Treatment with CTX-8371 resulted in improved overall survival in this model and cured three of eight mice, such that their tumors were completely eradicated.

Figure 13. Tumor growth inhibition was improved when treating mice with CTX-8371 compared to treating them with monoclonal antibodies that inhibited either PD-1, PD-L1, or the combination of PD-1 and PD-L1

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Figure 14. Dosing with CTX-8371 led to improved overall survival in a B16F10 melanoma model compared to either PD-1- or PD-L1- checkpoint inhibitors or to the combination of both

CTX-8371 also reduced tumor growth in the syngeneic MB49 bladder cancer model and in the syngeneic EMT-6 breast cancer models which are known to be non-responsive to checkpoint blocker treatments.

Figure 15. Dosing with CTX-8371 led to tumor growth inhibition in the syngeneic EMT-6 breast cancer model and in the syngeneic MB49 bladder cancer model

IND-enabling studies with CTX-8371 were initiated in August 2020 with the goal of initiating its clinical testing in the second half of 2021 following submission and acceptance of an IND.

License Agreement

We are successor to an amended and restated collaboration agreement with Adimab, LLC, or Adimab, dated February 11, 2015, as amended. This agreement relates to our license from Adimab for certain antibodies for development and commercialization as biopharmaceutical products, including our lead product candidate, CTX-471. We were granted an exclusive option to license antibodies under the agreement, which we exercised with respect to CTX-471, through which we gained an exclusive license to certain Adimab patents and know-how related to CTX-471. We are required to use commercially reasonable efforts to develop, seek marketing authorization for, launch and commercialize the licensed antibody. We are required to make payments upon achievement of development milestones that, as of December 31, 2020, amounted to $3.5 million, of which we have already made $1.5 million in milestone payments and we have additional potential payments due in the amount of $2.0 million. In addition, we

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are required to pay royalties at rates ranging in the single digits as a percentage of future net sales within a specified term from the first commercial sale.

The agreement will expire on a country-by-country basis on the expiration of the last royalty term for a product in the particular country, which commences from the first commercial sale of such product in such country until the twelve-year anniversary of such sale, in which case the license for any licensed antibody will automatically convert to be perpetual, irrevocable, non-exclusive and fully-paid in such country. The agreement may also be terminated by the parties for uncured material breach by the other party, and we may also terminate the agreement upon three months prior written notice to Adimab.

Intellectual Property

Overview

We strive to protect the proprietary technology, inventions, and know-how to enhance improvements that are important to the development of our business, including seeking, maintaining, and defending patent rights. We also rely on trade secrets and know-how relating to our proprietary technology platform, on continuing technological innovation and on in-licensing opportunities to develop, strengthen and maintain the strength of our position in the field of antibody therapeutics that may be important for the development of our business. We additionally may rely on regulatory protection afforded through data exclusivity, market exclusivity and patent term extensions where available.

Our success depends in part on our ability to: obtain and maintain patent and other protections for commercially important technology, inventions and know-how related to our business; defend and enforce our patents; preserve the confidentiality of our trade secrets; and operate without infringing the valid enforceable patents and intellectual property rights of third parties.

Our ability to stop third parties from making, using, selling, offering to sell, or importing our products depends in large part on the extent to which we have rights under valid and enforceable licenses, patents, or trade secrets that cover these activities. In some cases, these rights may need to be enforced by third-party licensors. With respect to company-owned intellectual property, we cannot be sure that patents will be granted with respect to any of our pending patent applications or with respect to any patent applications filed by us in the future, nor can we be sure that any of our existing patents or any patents that may be granted to us in the future will be useful in protecting our commercial products and methods of manufacturing the same. For more information, please see “Risk Factors—Risks Related to Our Intellectual Property.”

We seek to protect our proprietary position by, among other things, filing patent applications in the United States and internationally in certain jurisdictions where it is available. For example, we file U.S. and selected foreign patent applications related to our proprietary technology, inventions, and improvements that are important to the development of our business. We also intend to seek patent protection, or rely upon trade secret rights, to protect other technologies that may be used to discover and validate targets and that may be used to identify and develop novel products or improvements thereof. We seek protection, in part, through confidentiality and proprietary information agreements.

The term of individual patents depends upon the legal term of the patents in the countries in which they are obtained. In most countries in which we file, the patent term is 20 years from the earliest date of filing a non-provisional application which matures into a granted patent. A U.S. patent also may be accorded a patent term adjustment, or PTA, under certain circumstances to compensate for delays in obtaining the patent caused by the U.S. Patent and Trademark Office. In some instances, such a PTA may result in a U.S. patent term extending beyond 20 years from the earliest date of filing a non-provisional patent application. In addition, in the U.S., the term of a U.S. patent that covers an FDA approved drug may also be eligible for patent term extension, which permits patent term restoration as compensation for the patent term lost during the FDA regulatory review process. The Hatch Waxman Act permits a patent term extension of up to five years beyond the expiration of the patent. The length of the patent term extension is related to the length of time the drug is under regulatory review. Patent term

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extension cannot extend the remaining term of a patent beyond a total of 14 years from the date of product approval and only one patent applicable to an approved drug may be extended. Similar provisions are available in Europe and other foreign jurisdictions to extend the term of a patent that covers an approved drug. In the future, if and when our products receive FDA approval, we expect to apply for patent term extensions on patents covering those products. We plan to seek patent term extensions to any of our issued patents in any jurisdiction where these are available; however, there is no guarantee that the applicable authorities, including the FDA in the U.S., will agree with our assessment of whether such extensions should be granted, and if granted, the length of such extensions.

Patent Protection

For all patent applications, we determine strategy for claim scope on a case-by-case basis, taking into account advice of counsel and our business model and needs. We file patents containing claims for protection of all useful applications of our proprietary technologies and any products, as well as all new applications and/or uses we discover for existing technologies and products, based on our assessment of their strategic value. We continuously reassess the number and type of patent applications, as well as pending and issued patent claims to ensure that maximum coverage and value are obtained for our processes and compositions, given existing patent office rules and regulations. Further, claims may be modified during patent prosecution to meet our intellectual property and business needs.

Our patent estate includes patent applications with claims relating to our product candidates, methods of use and manufacturing processes, and claims for potential future products and developments. As of February 28, 2021, we have had 74 patent applications pending in the United States and foreign jurisdictions relating to CTX-471, CTX-8371 and other discovery and research programs. We have six patents which have issued in the United States related to our CTX-471 program.

We own five pending patent families with six issued U.S. patents, four U.S. Utility or provisional patent applications, one Patent Cooperation Treaty, or PCT, patent applications and 26 patent applications in foreign jurisdictions, related to our CD137 agonist antibody therapeutic platform including, but not limited to, our CTX-471 therapeutic candidate. Patents that grant from these patent families are generally expected to start to expire in 2038, subject to possible patent term extension.

We own two pending patent families with three U.S. Utility or provisional patent applications, one PCT patent application, and two patent applications in foreign jurisdictions, related to our PD-1/PD-L1 bispecific antibody therapeutic platform including, but not limited to, our CTX-8371 therapeutic candidate. Patents that grant from these patent families are generally expected to start to expire in 2039, subject to possible patent term extension.

We own, or have an ownership interest in, seven pending patent families with eight U.S. Utility or provisional patent applications and two PCT patent applications and eight patent applications in foreign jurisdictions related to our discovery and research programs. Patents that grant from these patent families are generally expected to start to expire in 2039, subject to possible patent term extension.

We own four pending patent families with two U.S. Utility or provisional patent applications and two PCT patent applications related to our antibody and display programs including, but not limited to, common light chains and mammalian display platforms. Patents that grant from these patent families are generally expected to start to expire in 2039, subject to possible patent term extension.

Trademark Protection

We have filed for and obtained trademark protection in multiple jurisdictions for the COMPASS THERAPEUTICS word mark and logo for goods and services. We have filed for and obtained trademark protection on the StitchMabs^TM word mark in the U.S. for goods.

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Trade Secret Protection

Finally, we may rely, in some circumstances, on trade secrets to protect our technology. We seek to protect our proprietary technology and processes, in part, by entering into confidentiality agreements with our employees, consultants, scientific advisors and contractors. We also seek to preserve the integrity and confidentiality of our data and trade secrets by maintaining physical security of our premises and physical and electronic security of our information technology systems. While we have confidence in these individuals, organizations and systems, agreements or security measures may be breached, and we may not have adequate remedies for any breach. In addition, our trade secrets may otherwise become known or be independently discovered by competitors. To the extent that our consultants, contractors or collaborators use intellectual property owned by others in their work for us, disputes may arise as to the rights in related or resulting know-how and inventions. For further information, please see “Risk Factors—Risks Related to Our Intellectual Property.”

Competition

The biotechnology and pharmaceutical industries, and the immuno-oncology subsector, are characterized by rapid evolution of technologies, fierce competition and strong defense of intellectual property. We believe that our programs, including CTX-471, CTX-8371 and our platform technologies, including our StitchMabs^TM platform and our programs, technology, knowledge, experience and scientific resources provide us with competitive advantages, but we also face competition from pharmaceutical and biotechnology companies, academic institutions, governmental agencies and public and private research institutions, among others. Our competitors include larger and better funded biopharmaceutical, biotechnology and therapeutics companies, including companies focused on cancer immunotherapies, such as AbbVie, Amgen, Inc., AstraZeneca plc, Bristol-Myers Squibb Company, or BMS, Eli Lilly, Genentech, Inc., GlaxoSmithKline PLC, Johnson & Johnson, Merck & Co., Inc., Merck KGaA, Novartis AG, Pfizer Inc., Roche Holding Ltd and Sanofi S.A. Moreover, we may also compete with smaller or earlier-stage companies, universities and other research institutions that have developed, are developing or may be developing current and future cancer therapeutics.

Product candidates that we successfully develop will compete with a range of therapies that are currently approved and any new therapies that may become available in the future. Key product features that would affect our ability to effectively compete with other therapeutics include the efficacy, safety and convenience of our products. Currently marketed oncology drugs and therapeutics range from traditional cancer therapies, including chemotherapy, to antibody-drug conjugates, such as Genentech Inc.’s Kadcyla, to immune checkpoint inhibitors targeting CTLA-4, such as BMS’ Yervoy, and PD-1/PD-L1, such as BMS’ Opdivo, Merck & Co.’s Keytruda and Genentech’s Tecentriq, to T cell-engager immunotherapies, such as Amgen’s Blincyto. In addition to these marketed therapies, numerous compounds are in clinical development for the potential treatment of cancer.

If we are successful in advancing one or more of our product candidates toward registrational studies and filing a BLA or BLAs, and if we are successful at obtaining approvals from the FDA or any other regulatory agency to market one or more of our product candidates, then the availability of reimbursement from government and other third-party payors will also significantly affect the pricing and competitiveness of our products. Our competitors, who may be successful at obtaining marketing approval from the FDA or other regulatory approval for their products prior to us obtaining marketing approval for our product candidates, could result in our competitors launching their products sooner and establishing a strong market position before we are even able to enter the market.

Sales and Marketing

We hold worldwide rights to all of our product candidates, which provide us the optionality to grow our internal pipeline independently or partner selected rights to our product candidates in different geographies throughout the world. Subject to receiving marketing approval, we intend to maximize the value of our product candidates by either independently planning to pursue the commercialization of our

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products in one or more major geographies by building an internal sales and marketing organization, or by seeking collaborations with third parties with commercialization infrastructure.

At the appropriate time in the future, and if one or more of our product candidates continues to advance successfully in development and enter registrational studies, we also plan to build a marketing and sales management organization to create and implement marketing strategies for any product candidates that we would potentially market through our own sales organization and to oversee and support our sales force. The responsibilities of such marketing organization would include developing educational initiatives with respect to approved products and establishing relationships with researchers and practitioners in relevant fields of medicine.

Manufacturing

We do not currently own or operate manufacturing facilities for the production of clinical quantities of our product candidates. We have relied on, and intend to continue to rely on, qualified third-party contract manufacturers to produce our product candidates, including clinical supplies to support our clinical trials. At the appropriate time in the product development process, we will determine whether to establish manufacturing facilities or continue to rely on third parties to manufacture clinical quantities of any products that we may successfully develop. We expect that commercial quantities of any compound and materials for our product candidates, if approved, will be manufactured in facilities and by processes that comply with FDA and other regulations, which may differ from our current clinical supply manufacturers.

Government Regulation

Government authorities in the United States, including federal, state, and local authorities, and in other countries, extensively regulate, among other things, the manufacturing, research and clinical development, marketing, labeling and packaging, storage, distribution, post-approval monitoring and reporting, advertising and promotion, and export and import of biological products, such as those we are developing. In addition, some government authorities regulate the pricing of such products. The process of obtaining regulatory approvals and the subsequent compliance with appropriate federal, state, local, and foreign statutes and regulations require the expenditure of substantial time and financial resources.

Review and Approval for Licensing Biologics in the United States

In the United States, the FDA regulates biological products under the Federal Food, Drug, and Cosmetic Act, or FDCA, and the Public Health Service Act, or PHSA, and their implementing regulations. FDA approval is required before any biological product can be marketed in the United States. Biological products are also subject to other federal, state, and local statutes and regulations. If we fail to comply with applicable FDA or other requirements at any time during the product development process, clinical testing, the approval process or after approval, we may become subject to administrative or judicial sanctions. These sanctions could include the FDA’s refusal to approve pending applications, license suspension or revocation, withdrawal of an approval, untitled or warning letters, product recalls, product seizures, total or partial suspension of production or distribution, injunctions, fines, civil penalties or criminal prosecution. Any FDA enforcement action could have a material adverse effect on us.

The process required by the FDA before product candidates may be marketed in the United States generally involves the following:

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The nonclinical and clinical testing and approval process requires substantial time, effort, and financial resources, and we cannot be certain that any approvals for our product candidates will be granted on a timely basis, if at all.

An IND is a request for authorization from the FDA to administer an investigational biological product to humans in clinical trials. The central focus of an IND submission is on the general investigational plan, the protocol(s) for human trials and the safety of study participants. The IND also includes results of animal and in vitro studies assessing the toxicology, pharmacokinetics, pharmacology, and pharmacodynamic characteristics of the product; chemistry, manufacturing and controls information; and any available human data or literature to support the use of the investigational product. An IND must become effective before human clinical trials may begin. An IND will automatically become effective 30 days after receipt by the FDA, unless before that time the FDA raises concerns or questions related to the proposed clinical trials. In such a case, the IND may be placed on clinical hold and the IND sponsor and the FDA must resolve any outstanding concerns or questions before clinical trials can begin. Accordingly, submission of an IND may or may not result in the FDA allowing clinical trials to commence. The FDA may impose a clinical hold at any time during clinical trials and may impose a partial clinical hold that would limit trials, for example, to certain doses or for a certain length of time.

Clinical Trials

Clinical trials involve the administration of the investigational product to human subjects under the supervision of qualified investigators in accordance with GCPs, which include the requirement that all research subjects provide their informed consent for their participation in any clinical trial. Clinical trials are conducted under protocols detailing, among other things, the objectives of the study, the inclusion and exclusion criteria, the parameters to be used in monitoring safety, and the efficacy criteria to be evaluated. A protocol for each clinical trial and any subsequent protocol amendments must be submitted to the FDA as part of the IND. Additionally, approval must also be obtained from each clinical trial site’s IRB, before the trials may be initiated and the IRB must monitor the trial until completed. There are also requirements governing the reporting of ongoing clinical trials and clinical trial results to public registries.

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The clinical investigation of a biological product is generally divided into three or four phases. Although the phases are usually conducted sequentially, they may overlap or be combined.

Phase 1.  The investigational product is initially introduced into healthy human subjects or patients with the target disease or condition. These studies are designed to evaluate the safety, dosage tolerance, metabolism and pharmacologic actions of the investigational product in humans, the side effects associated with increasing doses, and if possible, to gain early evidence on effectiveness.

Phase 2.  The investigational product is administered to a limited patient population to evaluate dosage tolerance and optimal dosage, identify possible adverse side effects and safety risks, and preliminarily evaluate efficacy.

Phase 3.  The investigational product is administered to an expanded patient population, generally at geographically dispersed clinical trial sites to generate enough data to statistically evaluate safety, purity and potency, to evaluate the overall benefit-risk profile of the investigational product, and to provide an adequate basis for physician labeling.

Phase 4.  In some cases, the FDA may condition approval of a BLA for a product candidate on the sponsor’s agreement to conduct additional clinical trials after approval. In other cases, a sponsor may voluntarily conduct additional clinical trials after approval to gain more information about the biological product. Such post-approval studies are typically referred to as Phase 4 clinical trials.

Sponsors must also report to the FDA, within certain timeframes, serious and unexpected adverse reactions, any clinically important increase in the rate of a serious suspected adverse reaction over that listed in the protocol or investigator’s brochure, or any findings from other studies or animal or in vitro testing that suggest a significant risk in humans exposed to the product candidate. The FDA, the IRB, or the clinical trial sponsor may suspend or terminate a clinical trial at any time on various grounds, including a finding that the research subjects are being exposed to an unacceptable health risk. Additionally, some clinical trials are overseen by an independent group of qualified experts organized by the clinical trial sponsor, known as a data safety monitoring board or committee. This group provides authorization for whether or not a trial may move forward at designated check points based on access to certain data from the trial. We may also suspend or terminate a clinical trial based on evolving business objectives or competitive climate.

A manufacturer of an investigational biological product for a serious disease or condition is required to make available, such as by posting on its website, its policy on evaluating and responding to requests for individual patient access to such investigational biological product. This requirement applies on the earlier of the first initiation of a Phase 2 or Phase 3 trial of the investigational biological product or, as applicable, 15 days after the biological product receives a designation as a breakthrough therapy or fast track product.

Submission of a BLA to the FDA

Assuming successful completion of all required testing in accordance with all applicable regulatory requirements, detailed investigational product information is submitted to the FDA in the form of a BLA requesting approval to market the product for one or more indications. Under federal law, the submission of most BLAs is subject to an application user fee. For fiscal year 2020, the application user fee is $2,942,965, and the sponsor of an approved BLA is also subject to an annual program fee of $325,424 for each approved biological product on the market. These fees are typically increased annually. Applications for orphan drug products are exempted from the BLA application fee and may be exempted from program fees, unless the application includes an indication for other than a rare disease or condition.

A BLA must include all relevant data available from pertinent nonclinical studies and clinical trials, including negative or ambiguous results as well as positive findings, together with detailed information relating to the product’s chemistry, manufacturing, controls, and proposed labeling, among other things.

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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 trials 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 product to the satisfaction of the FDA.

The FDA conducts a preliminary review of all BLAs within the first 60 days after submission before accepting them for filing to determine whether they are sufficiently complete to permit substantive review. The FDA may request additional information rather than accept an application for filing. Once a BLA has been submitted, the FDA’s goal for novel biological products generally is to review the application within ten months after it accepts the application for filing, or, if the application relates to an unmet medical need in a serious or life-threatening indication, six months after the FDA accepts the application for filing. The review process is often significantly extended by the FDA’s requests for additional information or clarification.

Before approving a BLA, the FDA typically will inspect the facility or facilities where the product is manufactured. 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 a BLA, the FDA will typically inspect one or more clinical sites to assure compliance with GCP.

The FDA is required to refer an application for a novel biological product to an advisory committee or explain why such referral was not made. 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.

The FDA’s Decision on a BLA

After the FDA evaluates the BLA and conducts relevant inspections, it may issue an approval letter or a Complete Response Letter. An approval letter authorizes commercial marketing of the biological product with specific prescribing information for specific indications. A Complete Response Letter indicates that the review cycle of the application is complete and the application is not ready for approval. A Complete Response Letter will identify the deficiencies that prevent the FDA from approving the application and may require additional clinical data or an additional Phase 3 clinical trial(s), or other significant, expensive and time-consuming requirements related to clinical trials, nonclinical studies or manufacturing. Even if such additional information is submitted, the FDA may ultimately decide that the BLA does not satisfy the criteria for approval and issue a denial.

The FDA could also approve the BLA with a Risk Evaluation and Mitigation Strategy, or REMS, program to mitigate risks, which could include medication guides, physician communication plans, or elements to assure safe use, such as restricted distribution methods, patient registries and other risk minimization tools. The FDA also may condition approval on, among other things, changes to proposed labeling, development of adequate controls and specifications, or a commitment to conduct one or more post-market studies or clinical trials. Such post-market testing may include Phase 4 clinical trials and surveillance to further assess and monitor the product’s safety and effectiveness after commercialization.

New government requirements, including those resulting from new legislation, may be established, or the FDA’s policies may change, which could delay or prevent regulatory approval of our products under development.

Expedited Review and Accelerated Approval Programs

A sponsor may seek approval of its product candidate under programs designed to accelerate FDA’s review and approval of BLAs. For example, Fast Track Designation may be granted to a biological

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product intended for treatment of a serious or life-threatening disease or condition that has potential to address unmet medical needs. The key benefits of fast track designation are more frequent interactions with the FDA during development and testing, the eligibility for priority review, and rolling review, which is submission of portions of an application before the complete marketing application is submitted.

Based on results of the Phase 3 clinical trial(s) submitted in a BLA, the FDA may grant the BLA a priority review designation, which sets the target date for FDA action on the application for a novel product at six months after the FDA accepts the application for filing. Priority review is granted where there is evidence that the proposed product would be a significant improvement in the safety or effectiveness of the treatment, diagnosis, or prevention of a serious condition. If criteria are not met for priority review, the application is subject to the standard FDA review period of ten months after FDA accepts the application for filing. Priority review designation does not change the scientific/medical standard for approval or the quality of evidence necessary to support approval.

Under the accelerated approval program, the FDA may approve a BLA on the basis of either a surrogate endpoint that is reasonably likely to predict clinical benefit, or on a clinical endpoint that can be measured earlier than irreversible morbidity or mortality, 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. Post-marketing trials or completion of ongoing trials after marketing approval are generally required to verify the biological product’s clinical benefit in relationship to the surrogate endpoint or ultimate outcome in relationship to the clinical benefit.

In addition, a sponsor may seek FDA designation of its product candidate as a breakthrough therapy if the biological product is intended, alone or in combination with one or more other drugs, to treat a serious or life- threatening disease or condition and preliminary clinical evidence indicates that the biological 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 benefits of breakthrough therapy designation include the same benefits as a Fast Track designation, in addition to intensive guidance from FDA to ensure an efficient development program.

Post-Approval Requirements

Biological products 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. Biological product manufacturers are subject to periodic unannounced inspections by the FDA and state agencies for compliance with cGMP requirements. Changes to the manufacturing process are strictly regulated, and, depending on the significance of the change, may 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 upon us and any third-party manufacturers that we may decide to use. Accordingly, manufacturers must continue to expend time, money and effort in the area of production and quality control to maintain compliance with cGMP and other aspects of regulatory compliance.

We rely, and expect to continue to rely, on third parties for the production of clinical quantities of our product candidates, and expect to rely in the future on third parties for the production of commercial quantities. Future FDA and state inspections may identify compliance issues at our facilities or at the facilities of our contract manufacturers that may disrupt production, or distribution, or may require substantial resources to correct. In addition, discovery of previously unknown problems with a product or the failure to comply with applicable requirements may result in restrictions on a product, manufacturer or holder of an approved BLA, including withdrawal or recall of the product from the market or other voluntary, FDA-initiated or judicial action that could delay or prohibit further marketing.

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The FDA may suspend or revoke product license approvals 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 adverse events 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 restrictions or other restrictions under a REMS program. FDA has authority to require post-market studies, in certain circumstances, on reduced effectiveness of a biological product and FDA may require labeling changes related to new reduced effectiveness information. Other potential consequences of a failure to maintain regulatory compliance include, among other things:

The FDA strictly regulates marketing, labeling, advertising, and promotion of products that are placed on the market. Biological 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.

Pediatric Trials and Exclusivity

A sponsor who is planning to submit a marketing application for a biological product that includes a new active ingredient, new indication, new dosage form, new dosing regimen or new route of administration must submit an initial Pediatric Study Plan, or PSP, within sixty days of an end of Phase 2 meeting or as may be agreed between the sponsor and FDA. The initial PSP must include an outline of the pediatric study or studies that the sponsor plans to conduct, including study objectives and design, age groups, relevant endpoints and statistical approach, or a justification for not including such detailed information, and any request for a deferral of pediatric assessments or a full or partial waiver of the requirement to provide data from pediatric studies along with supporting information. Generally, development program candidates designated as orphan drugs are exempt from the above requirements. FDA and the sponsor must reach agreement on the PSP. A sponsor can submit amendments to an agreed upon initial PSP at any time if changes to the pediatric plan need to be considered based on data collected from nonclinical studies, early phase clinical trials, and/or other clinical development programs.

Pediatric exclusivity is another type of non-patent exclusivity in the United States and, if granted, provides for the attachment of an additional six months of marketing protection to the term of any existing regulatory exclusivity, including the five-year and three-year non-patent and orphan exclusivity. This six-month exclusivity may be granted if a 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 FDA-requested pediatric trials are submitted to and accepted by the FDA within the statutory time limits, whatever statutory or regulatory periods of exclusivity or patent protection covering the 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 accept or approve another application relying on the BLA sponsor’s data.

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Patent Term Restoration

Depending upon the timing, duration, and specifics of the FDA approval of the use of our product candidates, some of our U.S. patents may be eligible for limited patent term extension under the Drug Price Competition and Patent Term Restoration Act of 1984, commonly referred to as the Hatch-Waxman Amendments. The Hatch- Waxman Amendments permit a patent restoration term of up to five years as compensation for patent term lost during product development and the FDA regulatory review process. However, patent term restoration cannot extend the remaining term of a patent beyond a total of 14 years from the product’s approval date. The patent term restoration period is generally one-half the time between the effective date of an IND and the submission date of a BLA, plus the time between the submission date and the approval of that application. 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 and within 60 days of the product’s approval. The U.S. Patent and Trademark Office, in consultation with the FDA, reviews and approves the application for any patent term extension or restoration. In the future, we may apply for restoration of patent term for one of our currently owned or licensed patents to add patent life beyond its current expiration date, depending on the expected length of the clinical trials and other factors involved in the filing of the relevant BLA.

Biosimilars and Exclusivity

The Patient Protection and Affordable Care Act, or Affordable Care Act, signed into law on March 23, 2010, includes a subtitle called the Biologics Price Competition and Innovation Act of 2009, or BPCI Act, which created an abbreviated approval pathway for biological products shown to be similar to, or interchangeable with, an FDA-licensed reference biological product. This amendment to the PHSA attempts to minimize duplicative testing. Biosimilarity, which requires that there be no clinically meaningful differences between the proposed biological product and the reference product in terms of safety, purity, and potency, can be shown through analytical studies, animal studies, and a clinical trial or trials. Interchangeability requires that a product is biosimilar to the reference product and the product must demonstrate that it can be expected to produce the same clinical results as the reference product and, for products administered multiple times, 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.

A reference biologic is granted twelve years of exclusivity from the time of first licensure of the reference product.

European Union/Rest of World Government Regulation

In addition to regulations in the United States, we will be subject to a variety of regulations in other jurisdictions governing, among other things, clinical trials and any commercial sales and distribution of our products. The cost of establishing a regulatory compliance system for numerous varying jurisdictions can be very significant. Although many of the issues discussed above with respect to the United States apply similarly in the context of the European Union and in other jurisdictions, the approval process varies between countries and jurisdictions and can involve additional product testing and additional administrative review periods. The time required to obtain approval in other countries and jurisdictions might differ from and be longer than that required to obtain FDA approval. Regulatory approval in one country or jurisdiction does not ensure regulatory approval in another, but a failure or delay in obtaining regulatory approval in one country or jurisdiction may negatively impact the regulatory process in others.

Whether or not we obtain FDA approval for a product, we must obtain the requisite approvals from regulatory authorities in foreign countries prior to the commencement of clinical trials or marketing of the product in those countries. Certain countries outside of the United States have a similar process that requires the submission of a clinical trial application much like the IND prior to the commencement of human clinical trials. In the European Union, for example, a clinical trial authorization application, or CTA, must be submitted for each clinical protocol to each country’s national health authority and an

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independent ethics committee, much like the FDA and IRB, respectively. Once the CTA is accepted in accordance with a country’s requirements, the clinical trial may proceed.

The requirements and process governing the conduct of clinical trials vary from country to country. In all cases, the clinical trials are conducted in accordance with GCP, the applicable regulatory requirements, and the ethical principles that have their origin in the Declaration of Helsinki.

To obtain regulatory approval of an investigational medicinal product under European Union regulatory systems, we must submit a marketing authorization application. The content of the BLA filed in the United States is similar to that required in the European Union, with the exception of, among other things, country-specific document requirements.

For other countries outside of the European Union, such as countries in Eastern Europe, Latin America or Asia, the requirements governing product licensing, pricing, and reimbursement vary from country to country.

Countries that are part of the European Union, as well as countries outside of the European Union, have their own governing bodies, requirements, and processes with respect to the approval of biological products. If we fail to comply with applicable foreign regulatory requirements, we may be subject to, among other things, fines, suspension or withdrawal of regulatory approvals, product recalls, seizure of products, operating restrictions and criminal prosecution.

Authorization Procedures in the European Union

Medicines can be authorized in the European Union by using either the centralized authorization procedure or national authorization procedures.

Centralized procedure.  The European Medicines Agency, or EMA, implemented the centralized procedure for the approval of human medicines to facilitate marketing authorizations that are valid throughout the European Economic Area, or EEA, which is comprised of the 28 member states of the European Union plus Norway, Iceland, and Lichtenstein. This procedure results in a single marketing authorization issued by the EMA that is valid across the EEA. The centralized procedure is compulsory for human medicines that are: derived from biotechnology processes, such as genetic engineering, contain a new active substance indicated for the treatment of certain diseases, such as HIV/AIDS, cancer, diabetes, neurodegenerative disorders or autoimmune diseases and other immune dysfunctions, and officially designated orphan medicines.

For medicines that do not fall within these categories, an applicant has the option of submitting an application for a centralized marketing authorization to the European Commission following a favorable opinion by the EMA, as long as the medicine concerned is a significant therapeutic, scientific or technical innovation, or if its authorization would be in the interest of public health.

National authorization procedures.  There are also two other possible routes to authorize medicinal products in several European Union countries, which are available for investigational medicinal products that fall outside the scope of the centralized procedure:

Decentralized procedure.  Using the decentralized procedure, an applicant may apply for simultaneous authorization in more than one European Union country of medicinal products that have not yet been authorized in any European Union country and that do not fall within the mandatory scope of the centralized procedure.

Mutual recognition procedure.  In the mutual recognition procedure, a medicine is first authorized in one European Union Member State, in accordance with the national procedures of that country. Following this, further marketing authorizations can be sought from other European Union countries in a procedure

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whereby the countries concerned agree to recognize the validity of the original, national marketing authorization.

In some cases, a Pediatric Investigation Plan, or PIP, or a request for waiver or deferral, is required for submission prior to submitting a marketing authorization application. A PIP describes, among other things, proposed pediatric trials and their timing relative to clinical trials in adults.

New Chemical Entity Exclusivity

In the European Union, new chemical entities, sometimes referred to as new active substances, qualify for eight years of data exclusivity upon marketing authorization and an additional two years of market exclusivity. This data exclusivity, if granted, prevents regulatory authorities in the European Union from referencing the innovator’s data to assess a generic (abbreviated) application for eight years, after which generic marketing authorization can be submitted, and the innovator’s data may be referenced, but not approved for two years. The overall ten-year period will be extended to a maximum of eleven years if, during the first eight years of those ten years, the marketing authorization holder obtains an authorization for one or more new therapeutic indications which, during the scientific evaluation prior to their authorization, are held to bring a significant clinical benefit in comparison with existing therapies.

Accelerated Review

Under the centralized procedure in the European Union, the maximum timeframe for the evaluation of a marketing authorization application is 210 days (excluding clock stops, when additional written or oral information is to be provided by the applicant in response to questions asked by the EMA’s Committee for Medicinal Products for Human Use, or CHMP). Accelerated evaluation might be granted by the CHMP in exceptional cases, when a medicinal product is expected to be of a major public health interest, particularly from the point of view of therapeutic innovation. In this circumstance, EMA ensures that the opinion of the CHMP is given within 150 days, excluding clock stops.

Pharmaceutical Coverage, Pricing and Reimbursement

Significant uncertainty exists as to the coverage and reimbursement status of any products for which we may obtain regulatory approval. In the United States and markets in other countries, sales of any products for which we may receive regulatory approval for commercial sale will depend in part on the availability of coverage and reimbursement for our products from third-party payors, such as government healthcare programs (e.g., Medicare, Medicaid), managed care providers, private health insurers, health maintenance organizations, and other organizations. These third-party payors decide which medications they will pay for and will establish reimbursement levels. The availability of coverage and extent of reimbursement by governmental and other third-party payors is essential for most patients to be able to afford treatments such as antibody-based therapies.

In the United States, the principal decisions about reimbursement for new medicines are typically made by the Centers for Medicare & Medicaid Services, or CMS, an agency within the U.S. Department of Health and Human Services, or HHS. CMS decides whether and to what extent our products will be covered and reimbursed under Medicare and private payors tend to follow CMS to a substantial degree. Factors payors consider in determining reimbursement are based on whether the product is:

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Our ability to successfully commercialize our product candidates will depend in part on the extent to which coverage and adequate reimbursement for these products and related treatments will be available from third-party payors. Moreover, a payor’s decision to provide coverage for a drug product does not imply that an adequate reimbursement rate will be approved.

No uniform policy of coverage and reimbursement for drug products exists among third-party payors. Therefore, coverage and reimbursement for drug products can differ significantly from payor to payor. The process for determining whether a payor will provide coverage for a product may be separate from the process for setting the reimbursement rate that the payor will pay for the product. One payor’s determination to provide coverage for a 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. Third-party payors may also limit coverage to specific products on an approved list, or formulary, which might not include all of the FDA-approved products for a particular indication.

Further, third-party payors are increasingly challenging the price and examining the medical necessity and cost- effectiveness of medical products and services, in addition to their safety and efficacy. In order to secure coverage and reimbursement for any product that might be approved for sale, we may need to conduct expensive pharmacoeconomic studies in order to demonstrate the medical necessity and cost-effectiveness of our products, in addition to the costs required to obtain FDA or comparable regulatory approvals. Additionally, we may also need to provide discounts to purchasers, private health plans or government healthcare programs. Our product candidates may nonetheless not be considered medically necessary or cost-effective. If third-party payors do not consider a product to be cost-effective compared to other available therapies, they may not cover the product after approval as a benefit under their plans or, if they do, the level of payment may not be sufficient to allow a company to sell its products at a profit. A decision by a third-party payor not to cover a product could reduce physician utilization once the product is approved and have a material adverse effect on sales, our operations and financial condition.

In some foreign countries, the proposed pricing for a drug must be approved before it may be lawfully marketed. The requirements governing drug pricing vary widely from country to country. For example, in the European Union Member States can restrict the range of medicinal products for which their national health insurance systems provide reimbursement and they can control the prices of medicinal products for human use. To obtain reimbursement or pricing approval, some of these countries may require the completion of clinical trials that compare the cost effectiveness of a particular product candidate to currently available therapies. A Member State may approve a specific price for the medicinal product or it may instead adopt a system of direct or indirect controls on the profitability of the company placing the medicinal product on the market. Approaches between Member States are diverging. For example, in France, effective market access will be supported by agreements with hospitals and products may be reimbursed by the Social Security Fund. The price of medicines is negotiated with the Economic Committee for Health Products, or CEPS. There can be no assurance that any country that has price controls or reimbursement limitations for pharmaceutical products will allow favorable reimbursement and pricing arrangements for any of our product candidates. Historically, products launched in the European Union do not follow price structures of the United States and generally prices tend to be significantly lower.

Current and future healthcare reform legislation

In the United States and in some foreign jurisdictions, there have been, and likely will continue to be, a number of legislative and regulatory changes and proposed changes regarding the healthcare system directed at broadening the availability of healthcare, improving the quality of healthcare, and containing or lowering the cost of healthcare. For example, the Patient Protection and Affordable Care Act, as amended by the Health Care and Education Reconciliation Act, collectively, the Affordable Care Act, or ACA, among other things, subjects biological products to potential competition by lower-cost

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biosimilars, expands the types of entities eligible for the 340B drug discount program, addresses a new methodology by which rebates owed by manufacturers under the Medicaid Drug Rebate Program are calculated for drugs that are inhaled, infused, instilled, implanted or injected, increases rebates for drugs sold to Medicaid programs owed by manufacturers under the Medicaid Drug Rebate Program and extends the rebate program to individuals enrolled in Medicaid managed care organizations, establishes annual fees and taxes on manufacturers of certain branded prescription drugs, and created a mandatory discount program for certain Medicare Part D beneficiaries in which manufacturers must agree to offer 50% (increased to 70% pursuant to the Bipartisan Budget Act of 2018, or BBA, effective as of January 2019) point-of-sale discounts off negotiated prices of applicable brand drugs to eligible beneficiaries during their coverage gap period, as a condition for the manufacturer’s outpatient drugs to be covered under Medicare Part D.

Since its enactment, there have been numerous judicial, administrative, executive, and legislative challenges to certain aspects of the ACA, and we expect there will be additional challenges and amendments to the ACA in the future. Various portions of the ACA are currently undergoing legal and constitutional challenges in the United States Supreme Court; the previous Trump administration issued various Executive Orders which eliminated cost sharing subsidies and various provisions that would impose a fiscal burden on states or a cost, fee, tax, penalty or regulatory burden on individuals, healthcare providers, health insurers, or manufacturers of pharmaceuticals or medical devices; and Congress has introduced several pieces of legislation aimed at significantly revising or repealing the ACA. It is unclear whether the ACA will be overturned, repealed, replaced, or further amended. We cannot predict what affect further changes to the ACA would have on our business.

Other legislative changes have been proposed and adopted in the United States since the ACA was enacted. For example, on August 2, 2011, the Budget Control Act of 2011 among other things, created measures for spending reductions by Congress. Specifically, the Joint Select Committee on Deficit Reduction was created to recommend to Congress proposals in spending reductions. The Joint Select Committee on Deficit Reduction did not achieve a targeted deficit reduction of at least $1.2 trillion for the years 2012 through 2021, thereby triggering the legislation’s automatic reduction to several government programs. This includes aggregate reductions to Medicare payments to providers of up to 2% per fiscal year, and due to subsequent legislative amendments, will stay in effect through 2030 unless additional Congressional action is taken. However, under the Coronavirus Aid, Relief and Economic Security Act, or CARES Act, the 2% Medicare sequestration reductions will be suspended from May 1, 2020 through December 31, 2020 due to the COVID-19 pandemic. The American Taxpayer Relief Act of 2012, or the ATRA, among other things, reduced Medicare payments to several providers and increased the statute of limitations period for the government to recover overpayments to providers from three to five years. Additionally, in December 2018, CMS published a final rule permitting further collections and payments to and from certain ACA qualified health plans and health insurance issuers under the Affordable Care Act risk adjustment program in response to the outcome of a federal district court litigation regarding the method CMS uses to determine this risk adjustment. Since then, the ACA risk adjustment program payment parameters have been updated annually.

Moreover, payment methodologies may be subject to changes in healthcare legislation and regulatory initiatives. For example, CMS may develop new payment and delivery models, such as bundled payment models. Recently, there has been heightened governmental scrutiny over the manner in which manufacturers set prices for their marketed products. Such scrutiny has resulted in several recent U.S. Congressional inquiries and proposed and enacted federal and state legislation designed to, among other things, bring more transparency to drug pricing, review the relationship between pricing and manufacturer patient programs, reduce the cost of drugs under Medicare and reform government program reimbursement methodologies for drug products. For example, at the federal level, the previous Trump administration’s budget proposal for fiscal year 2021 includes a $135 billion allowance to support legislative proposals seeking to reduce drug prices, increase competition, lower out-of-pocket drug costs for patients, and increase patient access to lower-cost generic and biosimilar drugs. On March 10, 2020, the previous Trump administration sent “principles” for drug pricing to Congress, calling for legislation that would, among other things, cap Medicare Part D beneficiary out-of-pocket pharmacy expenses, provide an option to cap Medicare Part D beneficiary monthly out-of-pocket expenses, and place limits on

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pharmaceutical price increases. Additionally, the previous Trump administration previously released a “Blueprint” to lower drug prices and reduce out of pocket costs of drugs that contained proposals to increase manufacturer competition, increase the negotiating power of certain federal healthcare programs, incentivize manufacturers to lower the list price of their products and reduce the out-of-pocket costs of drug products paid by consumers. HHS has solicited feedback on some of these measures and has implemented others under its existing authority. For example, in May 2019, CMS issued a final rule to allow Medicare Advantage Plans the option of using step therapy, a type of prior authorization, for Part B drugs beginning January 1, 2020. This final rule codified CMS’s policy change that became effective as of January 1, 2019. Although a number of these, and other measures may require additional authorization to become effective, Congress has indicated that they will continue to seek new legislative and/or administrative measures to control drug costs.

On July 24, 2020 and September 13, 2020, then-President Trump announced several executive orders related to prescription drug pricing that seek to implement several of the administration's proposals. In response, the FDA released a final rule on September 24, 2020, which went into effect on November 30, 2020, providing guidance for states to build and submit importation plans for drugs from Canada. Further, on November 20, 2020, CMS issued an Interim Final Rule implementing the Most Favored Nation (“MFN”) Model under which Medicare Part B reimbursement rates will be calculated for certain drugs and biologicals based on the lowest price drug manufacturers receive in Organization for Economic Cooperation and Development countries with a similar gross domestic product per capita. The MFN Model regulations mandate participation by identified Part B providers and will apply in all U.S. states and territories for a seven-year period beginning January 1, 2021 and ending December 31, 2027. On December 28, 2020, a judge in the U.S. District Court for the Northern District of California granted a preliminary injunction prohibiting CMS from implementing the MFN rule.

At the state level, legislatures have increasingly passed legislation and implemented regulations designed to control pharmaceutical 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.

On May 30, 2018, the Right to Try Act, was signed into law. The law, among other things, provides a federal framework for certain patients to access certain investigational new drug products that have completed a Phase 1 clinical trial and that are undergoing investigation for FDA approval. Under certain circumstances, eligible patients can seek treatment without enrolling in clinical trials and without obtaining FDA permission under the FDA expanded access program. There is no obligation for a drug manufacturer to make its drug products available to eligible patients as a result of the Right to Try Act.

Other Healthcare Laws and Compliance Requirements

Healthcare providers, physicians, and third-party payors will play a primary role in the recommendation and prescription of any products for which we obtain marketing approval. Our business operations and any current or future arrangements with third-party payors, healthcare providers and physicians may expose us to broadly applicable fraud and abuse and other healthcare laws and regulations that may constrain the business or financial arrangements and relationships through which we develop, market, sell and distribute any drugs for which we obtain marketing approval. In the United States, these laws include, among others:

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The scope and enforcement of each of these laws is uncertain and subject to rapid change in the current environment of healthcare reform, especially in light of the lack of applicable precedent and regulations. Federal and state enforcement bodies have recently increased their scrutiny of interactions between healthcare companies and healthcare providers, which has led to a number of investigations, prosecutions, convictions and settlements in the healthcare industry. It is possible that governmental authorities will conclude that our business practices do not comply with current or future statutes, regulations or case law involving applicable fraud and abuse or other healthcare laws and regulations. If our operations are found to be in violation of any of the laws described above or any other governmental regulations that apply to us, we may be subject to administrative, civil, and criminal penalties, exclusion from participation in government healthcare programs, such as Medicare and Medicaid, imprisonment, damages, fines, disgorgement, reputational harm, the curtailment or restructuring of our operations, and additional oversight and reporting obligations if we become subject to a corporate integrity agreement or similar settlement to resolve allegations of non-compliance with these laws and the curtailment or restructuring of our operations, any of which could adversely affect our ability to operate our business and our results of operations. If any of the physicians or other healthcare providers or entities with whom we expect to do business is found to be not in compliance with applicable laws, they may be subject to similar actions, penalties and sanctions. Ensuring business arrangements comply with applicable healthcare laws, as well as responding to possible investigations by government authorities, can be time- and resource-consuming and can divert a company’s attention from its business.

We are also subject to the U.S. Foreign Corrupt Practices Act, or FCPA, which prohibits improper payments or offers of payments to foreign governments and their officials for the purpose of obtaining or retaining business and requires companies to maintain accurate books and records and a system of internal accounting controls. Safeguards we implement to discourage improper payments or offers of payments by our employees, consultants, and others may be ineffective, and violations of the FCPA and similar laws may result in severe criminal or civil sanctions, or other liabilities or proceedings against us, any of which would likely harm our reputation, business, financial condition and result of operations.

In the event we decide to conduct future clinical trials in the European Union, we may be subject to additional privacy restrictions. The collection, use, storage, disclosure, transfer, or other processing of personal data regarding individuals in the European Economic Area, or EEA, including personal health data, is subject to the EU General Data Protection Regulation, or 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, including requirements relating to processing health and other sensitive data, obtaining consent of the individuals to whom the personal data relates, providing information to individuals regarding data processing activities, implementing safeguards to protect the security and confidentiality of personal data, 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

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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 violations of the GDPR. In addition, the GDPR includes restrictions on cross-border data transfers. The GDPR may increase our responsibility and liability in relation to personal data that we process where such processing is subject to the GDPR, and we may be required to put in place additional mechanisms to ensure compliance with the GDPR, including as implemented by individual countries. Compliance with the GDPR will be a rigorous and time-intensive process that may increase our cost of doing business or require us to change our business practices, and despite those efforts, there is a risk that we may be subject to fines and penalties, litigation, and reputational harm in connection with our European activities. Further, the United Kingdom’s decision to leave the European Union, often referred to as Brexit, has created uncertainty with regard to data protection regulation in the United Kingdom. In particular, it is unclear how data transfers to and from the United Kingdom will be regulated now that the United Kingdom has left the European Union.

Employees and Human Capital

As of December 31, 2020, we had 31 employees, of which all were full-time employees, 19 were primarily engaged in research and development activities and 13 hold M.D. or Ph.D. degrees. None of our employees is represented by labor unions or covered by collective bargaining agreements. We consider our relationship with our employees to be good.

Our human capital resources objectives include, as applicable, identifying, recruiting, retaining, incentivizing and integrating our existing and new employees, advisors and consultants. The principal purposes of our equity and cash incentive plans are to attract, retain and reward personnel through the granting of stock-based and cash-based compensation awards, in order to increase shareholder value and the success of our company by motivating such individuals to perform to the best of their abilities and achieve our objectives.

As an emerging company operating in a competitive industry, much of our success is rooted in the diversity of our teams and our commitment to inclusion. We value diversity at all levels and continue to focus on extending our diversity and inclusion initiatives across our entire workforce, from working with managers to develop strategies for building diverse teams to promoting the advancement of leaders from different backgrounds.

Corporate Information

We were incorporated as Olivia Ventures, Inc. in the State of Delaware on March 20, 2018. On June 17, 2020, a wholly-owned subsidiary of ours merged with and into Compass Therapeutics, a private limited liability company formed in 2014. Following the Merger, Compass Therapeutics was the surviving entity and became our wholly-owned subsidiary, and all of the outstanding common and preferred membership interests of Compass Therapeutics were converted into shares of our common stock. On June 17, 2020, we changed our name to Compass Therapeutics, Inc. As a result of the Merger, we acquired the business of Compass Therapeutics and we will continue the existing business operations of Compass Therapeutics as a public reporting company under the name Compass Therapeutics, Inc.

Our principal executive offices are located at 80 Guest Street, Suite 601, Boston, Massachusetts 02135, and our telephone number is (617) 500-8099.

Available Information

Our website address is www.compasstherapeutics.com. Our Form 10-K, Quarterly Reports on Form 10-Q, Current Reports on Form 8-K and any amendments to such reports are filed with the SEC. We are subject to the informational requirements of the Exchange Act and file or furnish reports, proxy

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statements, and other information with the SEC. Such reports and other information filed by us with the SEC will be available free of charge on our website at www.compasstherapeutics.com when such reports are available on the SEC’s website. The SEC maintains a website that contains reports, proxy and information statements, and other information that issuers file electronically with the SEC at www.sec.gov.

The contents of the websites referred to above are not incorporated into this filing. Further, our references to the URLs for these websites are intended to be inactive textual references only.

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