SMMT Filings — Summit Therapeutics Inc.

SMMT Filings — Summit Therapeutics Inc. - FilingSpy

10-Q · Quarter ended Jun 30, 2026 · SEC filing ↗

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Original filing text

Management's Discussion and Analysis

The following discussion and analysis of our financial condition and results of operations should be read in conjunction with our unaudited condensed consolidated financial statements and related notes included herein and our audited consolidated financial statements and related notes for the year ended December 31, 2025 included in our Annual Report. Some of the information contained in this discussion and analysis or set forth elsewhere in this filing, including information with respect to our plans and strategy for our business, includes forward-looking statements within the meaning of Section 27A of the Securities Act of 1933, as amended, and Section 21E of the Securities Exchange Act of 1934, as amended, that involve risks and uncertainties. All statements other than statements relating to historical matters including statements to the effect that we “believe,” “expect,” “anticipate,” “plan,” “target,” “intend” and similar expressions should be considered forward-looking statements. As a result of many factors, including those factors set forth in the risks identified in the “Risk Factors” section of our other filings with the SEC, our actual results could differ materially from the results, performance or achievements expressed in or implied by these forward-looking statements. Company Overview Summit Therapeutics Inc. (“we,” “Summit” or the “Company”) is a biopharmaceutical company focused on the discovery, development, and commercialization of patient-, physician-, caregiver- and societal-friendly medicinal therapies intended to improve quality of life, increase potential duration of life, and resolve serious unmet medical needs. The Company’s pipeline of product candidates is designed with the goal to become the patient-friendly, new-era standard-of-care medicines, in the therapeutic area of oncology. The Company’s current lead development candidate is ivonescimab, a novel, potential first-in-class bispecific antibody intending to combine the effects of immunotherapy via a blockade of PD-1 with the anti-angiogenesis effects of an anti-VEGF compound into a single molecule. On December 5, 2022, the Company entered into the License Agreement with Akeso pursuant to which the Company has in-licensed intellectual property rights related to ivonescimab (as amended, the “License Agreement”). Through the License Agreement, the Company obtained the rights to develop and commercialize ivonescimab in the United States, Canada, Europe, and Japan. The License Agreement and transaction closed in January 2023 following customary waiting periods. On June 3, 2024, the Company entered into the Second Amendment with Akeso to expand its territories covered under the License Agreement to also include Latin America, including Mexico and all countries in Central America and South America, the Middle East and Africa. The Company’s operations are focused on the development of ivonescimab and other future activities, as the Company determines. The Company is developing ivonescimab in non-small cell lung cancer (“NSCLC”) and colorectal cancer (“CRC”), specifically conducting Phase III clinical trials in the following proposed indications: (a) ivonescimab combined with chemotherapy in patients with epidermal growth factor receptor (“EGFR”)-mutated, locally advanced or metastatic non-squamous NSCLC who were previously treated with a third-generation EGFR tyrosine kinase inhibitor (“TKI”) (“HARMONi”); (b) ivonescimab combined with chemotherapy in patients with first-line metastatic NSCLC (including separate statistical analyses planned for patients with squamous NSCLC and non-squamous NSCLC) (“HARMONi-3”); (c) ivonescimab monotherapy in patients with first-line metastatic NSCLC whose tumors have high PD-L1 expression (“HARMONi-7”); and (d) ivonescimab combined with chemotherapy in patients with first-line unresectable metastatic CRC (“HARMONi-GI3”). In October 2024, the Company completed enrollment in its HARMONi clinical trial. In May 2025, we announced topline results from our multiregional, double-blinded, placebo-controlled, Phase III study HARMONi. At the prespecified primary data analysis, ivonescimab in combination with chemotherapy demonstrated a statistically significant improvement in progression free survival (“PFS”), the magnitude of which we believe to be clinically meaningful, with a hazard ratio of 0.52 (95% CI: 0.41 – 0.66; p<0.00001) compared to placebo in combination with chemotherapy; median PFS was 6.8 months for 20 those patients receiving ivonescimab plus chemotherapy compared to 4.4 months for those receiving chemotherapy. PFS was assessed by blinded independent central radiology committee (“BICR”). We believe the PFS hazard ratio that was observed in both Asian and western sub-populations to be clinically meaningful. The primary analysis demonstrated the consistency of the magnitude of the PFS benefit between patients randomized in Asian and western territories, as well as the consistency in a single-region study (“HARMONi-A”) with this multiregional study. In a longer-term follow-up of PFS, which included all western patients and at least six months of follow-up time for all patients, ivonescimab plus chemotherapy demonstrated a consistent improvement in PFS with an observed HR of 0.57 (95% CI: 0.46 – 0.71). With the longer-term follow-up analysis, consistency of the magnitude of PFS benefit was demonstrated between patients randomized in Asia and western patients when measured by hazard ratio. This longer-term follow-up analysis of PFS was performed at the time of the primary overall survival (“OS”) analysis. Ivonescimab in combination with chemotherapy showed a positive trend in OS in the primary analysis without achieving a statistically significant benefit with a hazard ratio of 0.79 (95% CI: 0.62 – 1.01; p=0.057). This trend provides further support for its use in EGFRm NSCLC after TKI therapy, a setting where high unmet need continues to exist with limited approved options in the United States and other western territories. Currently there are no FDA-approved regimens that have demonstrated a statistically significant OS benefit in this patient setting. Both Asian and North American patients demonstrated a positive trend in OS. The results of the primary analysis in this multiregional study were consistent with that of the single-region randomized Phase III HARMONi-A study, which demonstrated a statistically significant OS benefit with a hazard ratio of 0.74 in the primary OS analysis in a similar patient population. In September 2025, an additional ad hoc OS analysis was performed for the HARMONi study, whereby the western patients were followed for a longer period of time (Asian patients were locked at the time of the primary analysis). In this analysis that included longer-term follow-up of western patients (median follow-up time of western patients of 13.7 months), a hazard ratio consistent with the primary analysis was observed with an improved nominal p-value (HR=0.78; 95% CI: 0.62 – 0.98; nominal p=0.0332). Median OS for this analysis remained the same in both arms as was observed in the primary analysis. Median OS in Western patients receiving ivonescimab was 17.0 months compared to 14.0 months for those receiving placebo (HR=0.84); median OS in North American patients, specifically, had not yet been reached in the ivonescimab arm compared to 14.0 months in the placebo arm (HR=0.70). The hazard ratios for Western patients in totality, as well as patients from the North American and European regions individually, improved from the primary OS analysis to the analysis with longer-term follow-up of Western patients. Consistent benefit was observed across pre-defined subgroups. In July 2026, an updated analysis was conducted with a data cutoff date of June 2026 which analyzed OS when most western patients had discontinued treatment or completed two years of treatment. This analysis showed a consistent OS trend amongst western and Asian patients as western patients were followed for additional time on study reaching median follow-up of 23.2 months; Asian patients remained locked with a median follow-up time of 32.7 months from the primary analysis. A hazard ratio of 0.76 was observed for the full population; the 0.76 hazard ratio was observed in western patient subgroup, respectively, in this analysis. Ivonescimab continued to demonstrate an acceptable and manageable safety profile, that was consistent with previous Phase III data of ivonescimab plus chemotherapy with no additional safety signals noted. These OS results have been made available to the FDA, and more detailed data are intended to be presented at an upcoming medical conference. Based on the results of the HARMONi clinical trial, we submitted a Biologics License Application (“BLA”) in the fourth quarter of 2025 to seek approval for ivonescimab plus chemotherapy for this proposed indication. After careful consideration of the safety and efficacy profile of the current FDA-approved options for patients in this setting, the positive results of the Phase III multiregional study, including regional consistency, as well as discussions with key opinion leaders and those physicians who have administered ivonescimab to patients in a clinical study setting, we believe that the safety and efficacy data generated in the HARMONi study demonstrates that the ivonescimab regimen offers a potential treatment option for patients impacted by EGFR-mutant NSCLC in this setting with a favorable benefit-risk profile despite the lack of a statistically significant OS benefit. Summit announced in January 2026 that the FDA accepted for filing the BLA seeking approval for ivonescimab in combination with chemotherapy for this proposed indication. The FDA provided a Prescription Drug User Fee Act (PDUFA) goal action date of November 14, 2026. The FDA noted that a statistically significant OS benefit is necessary to support marketing authorization in this setting and the PFS results from this study may not be sufficient to support marketing authorization. 21 HARMONi-3 study (NCT05899608) is a Phase III, multi-regional, potentially registration-enabling clinical trial for which we initiated sites in North America, China and Europe. The two primary endpoints for this study are PFS and OS, and the study compares ivonescimab plus platinum-based doublet chemotherapy versus pembrolizumab plus platinum-based doublet chemotherapy in first-line patients with metastatic squamous NSCLC and non-squamous NSCLC. Enrollment is ongoing in all regions for patients with non-squamous tumors. In October 2025, the Company announced a protocol amendment to separate the statistical analysis of the primary endpoints by histology. Therefore, there will be separate analyses conducted to evaluate ivonescimab plus chemotherapy compared to pembrolizumab plus chemotherapy in patients with squamous NSCLC and in patients with non-squamous NSCLC. In order to sufficiently power for both primary endpoints (PFS and OS) in both cohorts of this study, Summit plans to enroll approximately 600 patients with squamous NSCLC and 1,000 patients with non-squamous NSCLC. As a result of having two separate intention-to-treat analyses within the HARMONi-3 study, the analyses for squamous tumors and non-squamous tumors may be conducted at separate times, as each analysis will be conducted upon the prespecified numbers of events being reached in the separate cohorts. Patient enrollment was completed for the squamous cohort of HARMONi-3 in the first quarter of 2026. Previously, Summit announced its intention to perform an interim PFS analysis for the squamous cohort of the HARMONi-3 study in the second quarter of 2026. To achieve statistical significance, there was a meaningfully higher bar than the upcoming planned final PFS analysis based on the minimal alpha spent on the interim analysis. At this early PFS interim analysis reviewed exclusively by the Independent Data Monitoring Committee (iDMC), the iDMC recommended that the study continue as planned. No safety concerns were noted, and the study continues to be double-blinded. The number of PFS events needed in the squamous cohort for the primary analysis is expected to be reached in the second half of 2026, and a planned early interim analysis for OS is expected to take place in conjunction with the primary PFS analysis. An interim analysis for overall survival independent of PFS is planned for the first half of 2027. Enrollment in the non-squamous cohort of the global HARMONi-3 study was completed in the second quarter of 2026. For this cohort, the number of events needed to conduct the PFS analysis is expected to be reached in the first half of 2027. Akeso Collaboration and License Agreement Pursuant to the License Agreement with Akeso, the Company received the rights to develop and commercialize ivonescimab in the Licensed Territory. Akeso retained development and commercialization rights for the rest of the world excluding the Licensed Territory. In exchange for these rights, Summit made an upfront payment during the first quarter of 2023 comprised of $474.9 million cash and the issuance of 10 million shares of Company common stock in lieu of $25.1 million cash pursuant to a share transfer agreement. Furthermore, on June 3, 2024, the Company entered into an amendment to the License Agreement with Akeso to expand its territories covered under the License Agreement to also include the Latin America, Middle East and Africa regions for which Summit paid an upfront payment of $15.0 million cash in the third quarter of 2024. In addition, the Company may also pay Akeso (a) milestone payments tied to achievement of regulatory approval of ivonescimab with various regulatory authorities in the Licensed Territory, (b) milestone payments tied to achievement of annual revenue from ivonescimab in the Licensed Territory and (c) royalty payments equal to low-double-digit percentage of annual revenues from ivonescimab in the Licensed Territory. In connection with the License Agreement, the Company agreed to purchase a certain portion of drug substance and/or drug product for clinical and commercial supply and to enter into a supply agreement with Akeso. Pursuant to the terms of the License Agreement, Summit has final decision-making authority with respect to all of its commercialization activities including, but not limited to, commercial strategy, pricing and reimbursement in the Licensed Territory. Summit has not assumed any liabilities (including contingent liabilities), nor acquired any physical assets or trade names, or hired or acquired any employees from Akeso in connection with the License Agreement. 22 Other Collaboration Agreements In June 2025, the Company entered into a clinical trial collaboration with Revolution Medicines Inc. (“RevMed”) to evaluate ivonescimab in combination with three RevMed RAS(ON) inhibitors (the “RevMed Collaboration”). In January 2026, the Company entered into a clinical trial collaboration with GSK plc to evaluate ivonescimab in combination with GSK’s novel B7-H3 ADC, risvutatug rezetecan, in multiple solid tumors (the “GSK Collaboration”). Neither the RevMed Collaboration nor the GSK Collaboration include upfront payments, milestone payments, or royalty sharing provisions. For the three and six months ended June 30, 2026, there was no cash consideration exchanged in connection with either the RevMed Collaboration or the GSK Collaboration. In July 2026, the Company entered into a clinical trial collaboration with Arcus Biosciences, Inc (“Arcus”) to evaluate ivonescimab in combination with Arcus’ novel inhibitor of hypoxia-inducible factor 2-alpha, casdatifan, in clear cell renal cell carcinoma (the “Arcus Collaboration”). Both Arcus and the Company will contribute to the cost of the clinical study and each will provide study drug for purposes of conducting the clinical trial. There are no additional milestone payments or royalty sharing provisions thereafter. Ivonescimab Ivonescimab is a novel potential first-in-class PD-1 / VEGF-A bispecific antibody, believed to be the most advanced in clinical development in the Licensed Territory. Engineered with Akeso’s unique Tetrabody technology, ivonescimab, as a single molecule, blocks programmed cell death protein 1 (“PD-1”) from binding to PD-L1 and PD-L2, and blocks the protein vascular endothelial growth factor-A (“VEGF”) from binding to VEGF receptors. Ivonescimab is designed to potentially allow cooperative binding of the intended targets, such that the binding of VEGF increases the binding affinity of PD-1. In view of the co-expression of VEGF and PD-1 in the tumor micro-environment (“TME”), ivonescimab may block these two pathways more effectively and enhance the antitumor activity, as compared to combination therapy through what is believed to be a unique cooperative binding mechanism. 23 This could differentiate ivonescimab as there is potentially higher expression (presence) of both PD-1 and VEGF in tumor tissue and the TME as compared to normal tissue in the body. As shown in Akeso’s in-vitro studies, ivonescimab’s tetravalent structure (four binding sites) enables higher avidity (accumulated strength of multiple binding interactions) in the TME with over 10-fold increased binding affinity to PD-1 in the presence of VEGF. This tetravalent structure, the intentional novel design of the molecule, and bringing these two targets into a single bispecific antibody with cooperative binding qualities has the potential to direct ivonescimab to the tumor tissue versus healthy tissue. The intent of this design is to improve upon previously established efficacy thresholds, in addition to side effects and safety profiles associated with these targets. Ivonescimab is currently being developed by both Akeso and the Company in multiple Phase III clinical trials. Over 4,000 patients have been treated with ivonescimab in clinical studies globally, and over 70,000 patients when considering those treated in a commercial setting in China as noted and updated by Akeso. Product Pipeline Summit Sponsored Ivonescimab Trials Ivonescimab is currently being investigated in global Phase III clinical trials. Phase I and II trials were completed by or are ongoing with our partner Akeso. This pipeline reflects Phase III clinical trials that have been or are planned to be initiated by Summit in its Licensed Territory. 24 HARMONi HARMONi study (NCT06396065) is a Phase III, multi-regional, potentially registration-enabling clinical trial, which enrolled patients in North America, Europe, and China. Patients enrolled in China were also enrolled as a part of the HARMONi-A study. We completed enrollment of patients in North America and Europe in October 2024. The two primary endpoints for this study are PFS and OS, and the study compares ivonescimab plus platinum-based doublet chemotherapy versus placebo plus platinum-based doublet chemotherapy in patients with advanced or metastatic EGFR-mutated NSCLC whose tumors have progressed following treatment with a third generation EGFR-TKI. The dual primary endpoints were allocated separate alpha levels and tested individually. The alpha was recycled from the PFS to the OS analysis upon the successful achievement of the PFS endpoint. In May 2025, we announced topline results from our multiregional, double-blinded, placebo-controlled, Phase III study HARMONi. At the prespecified primary data analysis, ivonescimab in combination with chemotherapy demonstrated a statistically significant improvement in PFS, the magnitude of which we believe to be clinically meaningful, with a hazard ratio of 0.52 (95% CI: 0.41 – 0.66; p<0.00001) compared to placebo in combination with chemotherapy; median PFS was 6.8 months for those patients receiving ivonescimab plus chemotherapy compared to 4.4 months for those receiving chemotherapy. PFS was assessed by BICR. We believe the PFS hazard ratio that was observed in both Asian and western sub-populations to be clinically meaningful. The primary analysis demonstrated the consistency of the magnitude of the PFS benefit between patients randomized in Asia and western territories, as well as the consistency in a single-region study (HARMONi-A) with this multiregional study. In a longer-term follow-up of PFS, which included all western patients and at least six months of follow-up time for all patients, ivonescimab plus chemotherapy demonstrated a consistent improvement in PFS with an observed HR of 0.57 (95% CI: 0.46 – 0.71). With the longer-term follow-up analysis, consistency of the magnitude of PFS benefit was demonstrated between patients randomized in Asia and western patients when measured by hazard ratio. This longer-term follow-up analysis of PFS was performed at the time of the primary OS analysis. Ivonescimab in combination with chemotherapy showed a positive trend in OS in the primary analysis without achieving a statistically significant benefit with a hazard ratio of 0.79 (95% CI: 0.62 – 1.01; p=0.057). This trend provides further support for its use in EGFRm NSCLC after TKI therapy, a setting where high unmet need continues to exist with limited approved options in the United States and other western territories. Currently, there are no FDA-approved regimens that have demonstrated a statistically significant OS benefit in this patient setting. Both Asian and North American patients demonstrated a positive trend in OS. The results of the primary analysis in this multiregional study were consistent with that of the single-region randomized Phase III HARMONi-A study, which demonstrated a statistically significant OS benefit hazard ratio of 0.74 in the primary OS analysis in a similar patient population. In September 2025, an additional ad hoc OS analysis was performed for the HARMONi study whereby the western patients were followed for a longer period of time (Asian patients were locked at the time of the primary analysis). In this analysis that included longer-term follow-up of western patients (median follow-up time of western patients of 13.7 months), a hazard 25 ratio consistent with the primary analysis was observed with an improved nominal p-value (HR=0.78; 95% CI: 0.62 – 0.98; nominal p=0.0332). Median OS for this analysis remained the same in both arms as was observed in the primary analysis. Median OS in western patients receiving ivonescimab was 17.0 months compared to 14.0 months for those receiving placebo (HR=0.84); median OS in North American patients, specifically, had not yet been reached in the ivonescimab arm compared to 14.0 months in the placebo arm (HR=0.70). The hazard ratios for western patients in totality, as well as patients from the North American and European regions individually, improved from the primary OS analysis to the analysis with longer-term follow-up of western patients. Consistent benefit was observed across pre-defined subgroups. In July 2026, an updated analysis was conducted with a data cutoff date of June 2026 which analyzed OS when most western patients had discontinued treatment or completed two years of treatment. This analysis showed a consistent OS trend amongst western and Asian patients as western patients were followed for additional time on study reaching median follow-up of 23.2 months; Asian patients remained locked with a median follow-up time of 32.7 months from the primary analysis. A hazard ratio of 0.76 was observed for the full population; the 0.76 hazard ratio was observed in western patient subgroup, respectively, in this analysis. Ivonescimab continued to demonstrate an acceptable and manageable safety profile, that was consistent with previous Phase III data of ivonescimab plus chemotherapy with no additional safety signals noted. These OS results have been made available to the FDA, and more detailed data are intended to be presented at an upcoming medical conference. The safety profile of ivonescimab in combination with chemotherapy was acceptable and manageable in the context of the observed clinical benefit with comparable rates of discontinuation and death between both arms. There were 16 patients (7.3%) who discontinued ivonescimab due to treatment-related adverse events (“TRAEs”) compared to 11 patients (5.0%) who discontinued placebo due to TRAEs. There were four patients (1.8%) in the ivonescimab plus chemotherapy arm and five patients (2.3%) in the chemotherapy alone arm who died as a result of TRAEs. In the ivonescimab plus chemotherapy arm, 50.0% of patients experienced Grade 3 or higher TRAEs compared to 42.2% in the chemotherapy arm. Of note, 0.9% of patients in the ivonescimab plus chemotherapy arm experienced Grade 3 or higher treatment-related hemorrhagic (bleeding) events. Based on the results of the HARMONi clinical trial, Summit submitted a BLA in the fourth quarter of 2025 in order to seek approval for ivonescimab plus chemotherapy in this setting. Summit announced in January 2026 that the FDA accepted for filing the BLA, seeking approval for ivonescimab in combination with chemotherapy for this proposed indication. The FDA provided a Prescription Drug User Fee Act (PDUFA) goal action date of November 14, 2026. The FDA noted that a statistically significant OS benefit is necessary to support marketing authorization in this setting, and the PFS results from this study may not be sufficient to support marketing authorization. HARMONi-3 HARMONi-3 study (NCT05899608) is a Phase III, multi-regional, potentially registration-enabling clinical trial for which we initiated sites in North America, China and Europe. The two primary endpoints for this study are PFS and OS, and the study compares ivonescimab plus platinum-based doublet chemotherapy versus pembrolizumab plus platinum-based doublet chemotherapy in first-line patients with metastatic squamous NSCLC and non-squamous NSCLC. Enrollment is ongoing in all regions for patients with non-squamous tumors. In October 2025, the Company announced a protocol amendment to separate the statistical analysis of the primary endpoints by histology. Therefore, there will be separate analyses conducted to evaluate ivonescimab plus chemotherapy compared to pembrolizumab plus chemotherapy in patients with squamous NSCLC and in patients with non-squamous NSCLC. In order to sufficiently power for both primary endpoints (PFS and OS) in both cohorts of this study, Summit plans to enroll approximately 600 patients with squamous NSCLC and 1,000 patients with non-squamous NSCLC. As a result of having two separate intention-to-treat analyses within the HARMONi-3 study, the analyses for squamous tumors and non-squamous tumors may be conducted at separate times, as each analysis will be conducted upon the prespecified numbers of events being reached in the separate cohorts. 26 Patient enrollment was completed for the squamous cohort of HARMONi-3 in the first quarter of 2026. Previously, Summit announced its intention to perform an interim PFS analysis for the squamous cohort of the HARMONi-3 study in the second quarter of 2026. To achieve statistical significance, there was a meaningfully higher bar than the upcoming planned final PFS analysis based on the minimal alpha spent on the interim analysis. At this early PFS interim analysis reviewed exclusively by the Independent Data Monitoring Committee (iDMC), the iDMC recommended that the study continue as planned. No safety concerns were noted, and the study continues to be double-blinded. The number of PFS events needed in the squamous cohort for the primary analysis is expected to be reached in the second half of 2026, and a planned early interim analysis for OS is expected to take place in conjunction with the primary PFS analysis. An interim analysis for overall survival independent of PFS is planned for the first half of 2027. Enrollment in the non-squamous cohort of the global HARMONi-3 study was completed in the second quarter of 2026. For this cohort, the number of events needed to conduct the PFS analysis is expected to be reached in the first half of 2027. HARMONi-7 Based on the results of HARMONi-2, the Company is enrolling in the HARMONi-7 study (NCT06767514). HARMONi-7 is a multi-regional, potentially registration-enabling Phase III clinical trial that will compare ivonescimab monotherapy to pembrolizumab monotherapy in patients with metastatic squamous and non-squamous NSCLC whose tumors have high PD-L1 expression. The sample size for this study is currently planned to have an estimated 780 patients with two primary endpoints, PFS and OS. HARMONi-GI3 In the fourth quarter of 2025, the Company activated trial sites and began enrolling patients in HARMONi-GI3, a Phase III, multi-regional, clinical trial evaluating ivonescimab plus chemotherapy compared to bevacizumab plus chemotherapy as first line therapy in patients with unresectable metastatic CRC. The primary endpoint for this study is PFS and Summit plans to enroll approximately 600 patients. Non-Sponsored Phase III Clinical Studies (Summit’s License Territories) In the first quarter of 2026, the Company announced that GORTEC (Groupe d'Oncologie Radiothérapie Tête Et Cou or Head and Neck Oncology and Radiotherapy Group), a cooperative group dedicated to Head and Neck Oncology, will initiate the Phase III clinical study, ILLUMINE (NCT07264075), which will evaluate ivonescimab monotherapy and ivonescimab in combination with ligufalimab, Akeso’s proprietary anti-CD47 monoclonal antibody, against monotherapy pembrolizumab in a three-arm study. The study is intended to be conducted in multiple countries in Europe and in China; Summit will consider the expansion of this study into the United States. The primary endpoint for the study is OS. The study, currently planned to enroll 780 patients with recurrent or metastatic PD-L1 positive head and neck squamous cell carcinoma (HNSCC), began enrollment in the second quarter of 2026. Data supporting this study was previously presented at the 2024 European Society for Medical Oncology Annual Congress (“ESMO 2024”), whereby ivonescimab in combination with ligufalimab demonstrated an objective response rate of 60% in 20 patients with a median PFS of 7.1 months after a median follow-up time of 4.1 months; OS was not mature at the time of this analysis. At the time of data cut-off for this presentation, no patients receiving ivonescimab plus ligufalimab permanently discontinued drug treatment due to treatment-related adverse events. Potential Future Clinical Development and Additional Current Activities Summit is conducting its current clinical trials and plans to design and conduct additional clinical trial activities for ivonescimab within its Licensed Territory to support and submit relevant regulatory filings. We intend to explore further clinical development of ivonescimab in solid tumor settings outside of metastatic NSCLC and metastatic CRC, our current areas of focus in our Phase III clinical trials. 27 In the fourth quarter of 2023, we began collaborating with multiple institutions globally and opened our investigator- sponsored trials program across several disease areas. We continued to expand this program in order to discover additional opportunities for ivonescimab, including in several tumors outside of our current development plan. We plan to review the data generated from these clinical trials as well as Akeso-sponsored clinical trials as a part of our consideration for advancing our clinical development pipeline for ivonescimab in the Licensed Territory. Additional Ivonescimab Development: Akeso-Sponsored Trials Akeso is currently developing ivonescimab in NSCLC and other solid tumor settings. Ivonescimab was approved by the National Medical Products Administration (“NMPA”) in May 2024 in China in combination with chemotherapy for patients with EGFR-mutated NSCLC whose tumors have progressed following an EGFR-TKI based on the results of the HARMONi-A clinical trial. Subsequently, ivonescimab was approved by the NMPA in April 2025 as monotherapy based on the results of the HARMONi-2 study in first-line, PD-L1 positive NSCLC. Also in October 2025, Akeso announced the positive data for the HARMONi-6 study in first-line squamous NSCLC for ivonescimab in combination with chemotherapy. Further details related to these three trials, in addition to other Phase II clinical data, are described further below. Akeso is currently conducting Phase III clinical trials in combination with chemotherapy in first-line biliary tract cancer (“HARMONi-GI1”), in first-line advanced PD-L1 low or negative triple-negative breast cancer (“TNBC”) (“HARMONi-BC1”), in first-line advanced microsatellite stable CRC (“HARMONi-GI6”) and in NSCLC for patients whose tumors have progressed following PD-(L)1 inhibitor based therapy (“HARMONi-8A”), as well as in combination with ligufalimab, a proprietary Akeso-owned investigational CD-47 monoclonal antibody, in first-line recurrent / metastatic PD-L1 positive head-and-neck cancer (“HARMONi-HN1”) and in combination with ligufalimab plus chemotherapy in first-line advanced pancreatic cancer (“HARMONi-GI2”). In addition, Akeso is conducting a Phase III study with ivonescimab after consolidation chemotherapy and radiotherapy in the limited stage small cell lung cancer setting (“HARMONi-9”). HARMONi-A Based on data published by Akeso at the American Society of Clinical Oncology (“ASCO 2024”) and in a publication in the Journal of the American Medical Association (JAMA) in the HARMONi-A study, in a single-region (China), randomized, double-blinded Phase III study in patients with NSCLC who have progressed following an EGFR-TKI, ivonescimab achieved its primary endpoint of PFS when combined with doublet chemotherapy (pemetrexed and carboplatin). Patients experienced a 54% reduction in disease progression or death as compared to placebo plus doublet-chemotherapy (HR: 0.46, 95% CI: 0.34 - 0.62; p<0.001). In a pre-specified subgroup analysis of patients who received a previous third-generation TKI, a hazard ratio of 0.48 was observed. At the primary OS analysis of HARMONi-A, ivonescimab achieved a hazard ratio of 0.74 (95% CI: 0.58, 0.95, p=0.019), demonstrating a statistically significant and clinically meaningful OS benefit, which was presented in November 2025 at the 2025 Annual Meeting for the Society for Immunotherapy for Cancer. Ivonescimab demonstrated an acceptable and manageable safety profile, which was consistent with previous studies. There were nine patients (5.6%) who discontinued ivonescimab plus chemotherapy due to TRAEs compared to four patients (2.5%) who discontinued chemotherapy plus placebo due to TRAEs. No TRAEs resulted in the death of a patient in either arm in this Phase III study. Full results were published in JAMA (Fang et al. 2024). HARMONi-2 After announcing positive qualitative results on May 30, 2024 for the HARMONi-2 trial, also referred to as AK112-303, a randomized, single-region (China) Phase III study sponsored by Akeso, quantitative data was presented on September 8, 2024 from the primary analysis as part of the Presidential Symposium at the International Association for the Study of Lung Cancer’s (“IASLC”) 2024 World Conference on Lung Cancer (“WCLC 2024”). The HARMONi-2 presentation evaluated monotherapy ivonescimab compared to monotherapy pembrolizumab in patients with locally advanced or metastatic NSCLC whose tumors have positive PD-L1 expression. HARMONi-2 is a single region, multi-center, double-blinded Phase III study conducted in China sponsored by Akeso, with all relevant data exclusively generated, managed, and analyzed by Akeso. In the HARMONi-2 primary analysis, ivonescimab monotherapy demonstrated a statistically significant improvement in the trial’s primary endpoint, PFS by Independent Radiologic Review Committee (“IRRC”), when compared to monotherapy 28 pembrolizumab, achieving a hazard ratio of 0.51 (95% CI: 0.38, 0.69; p<0.0001). A clinically meaningful benefit was demonstrated across clinical subgroups, including patients with tumors with high PD-L1 expression. OS data was not yet mature at the time of the data cutoff of the primary PFS analysis. Ivonescimab demonstrated an acceptable and manageable safety profile, which was consistent with previous studies. There were three patients (1.5%) who discontinued ivonescimab due to TRAEs compared to six patients (3.0%) who discontinued pembrolizumab due to TRAEs. There was one patient in the ivonescimab arm and two patients in the pembrolizumab arm who died as a result of TRAEs in this Phase III study. Full results were published in Lancet (Xiong et al. 2025). On April 25, 2025, Akeso announced that ivonescimab was approved in China by the NMPA for a second indication based on the results of the HARMONi-2 trial. As a part of the review of the supplemental marketing application submitted by Akeso seeking a label expansion of ivonescimab in China, the NMPA requested that Akeso perform an interim analysis of OS. Akeso announced that the results of this interim OS analysis included a clinically meaningful hazard ratio of 0.777. The analysis was conducted at 39% data maturity, with a nominal alpha level of 0.0001 that had not reached statistical significance. HARMONi-6 After announcing positive qualitative results for the HARMONi-6 trial, on April 23, 2025, detailed clinical trial results of the study were presented as part of the Presidential Symposium at the European Society for Medical Oncology’s 2025 Congress (“ESMO 2025”). Additionally, positive overall survival data from the HARMONi-6 trial was presented on May 31, 2026 as a late breaking abstract for the plenary session at the ASCO 2026 Annual Meeting. The HARMONi-6 study evaluated ivonescimab in combination with platinum-based chemotherapy compared to tislelizumab (a PD-1 inhibitor) in combination with platinum-based chemotherapy in patients with previously untreated advanced NSCLC irrespective of PD-L1 expression. HARMONi-6, also referred to as AK112-306, is a single region, multi-center, double-blinded Phase III study conducted in China sponsored by Akeso, with all relevant data exclusively generated, managed, and analyzed by Akeso. In the HARMONi-6 planned PFS interim analysis, ivonescimab in combination with chemotherapy demonstrated a statistically significant improvement in the primary endpoint, PFS, by IRRC, when compared to tislelizumab in combination with chemotherapy, achieving a hazard ratio of 0.60 (95% CI: 0.46, 0.78; p<0.0001). In the HARMONi-6 planned interim analysis of OS, ivonescimab in combination with chemotherapy demonstrated a statistically significant improvement when compared to tislelizumab in combination with chemotherapy, with a hazard ratio of 0.66 (95% CI: 0.50, 0.87; p=0.0017). For both PFS and OS, a clinically meaningful benefit was demonstrated across clinical subgroups, including those with either PD-L1 negative or positive expression. Ivonescimab demonstrated an acceptable and manageable safety profile in the HARMONi-6 study, which was consistent with previous Phase III studies conducted studying ivonescimab. 14 patients (5.3%) discontinued ivonescimab plus chemotherapy due to TRAEs compared to 12 patients (4.5%) receiving tislelizumab plus chemotherapy due to TRAEs. There were 10 patients in the ivonescimab plus chemotherapy arm and 11 patients in the tislelizumab plus chemotherapy arm who died as a result of TRAEs in this Phase III study. Results were published in Lancet (Lu et al. 2026). Additional Phase II Data Sets In addition to the HARMONi-2 data announced at WCLC 2024, Akeso also announced Phase II trial results from AK112-205, for patients with Stage II or III resectable NSCLC. Further, the Company announced data for ivonescimab was presented as a part of ESMO 2024 featuring updated Phase II ivonescimab data in advanced TNBC, for which subsequent updates to the data have been presented thereafter, recurrent / metastatic head and neck squamous cell carcinoma, and metastatic microsatellite-stable CRC. At ASCO 2024, Akeso presented ivonescimab Phase II data in biliary-tract cancer. Earlier, at the 2024 European Lung Cancer Conference, Akeso announced updated data from AK112-201 (Cohort 1), a Phase II study for patients with first-line advanced NSCLC. Each trial from which the data was generated was a multi-center Phase II study conducted in China sponsored by Akeso, with data generated and analyzed by Akeso. 29 Additionally, at ASCO 2026, Summit presented new global Phase II ivonescimab data in metastatic microsatellite-stable CRC. Data generated was from a multi-center Phase II study conducted in the U.S. and China co-sponsored by Summit and Akeso, with data generated and analyzed by Summit and Akeso. Results of Operations Amounts reported in millions within this Quarterly Report on Form 10-Q are computed based on the amounts in thousands, and therefore, the sum of components may not equal the total amount reported in millions due to rounding. The following table sets forth our results of operations for the three and six months ended June 30, 2026 and 2025: Three Months Ended June 30, Six Months Ended June 30, (in millions) 2026 2025 $ Change 2026 2025 $ Change Operating expenses: Research and development $ 157.7 $ 208.0 $ (50.3) $ 290.3 $ 259.3 $ 31.0 General and administrative 62.8 360.4 (297.6) 125.4 376.0 (250.6) Total operating expenses 220.5 568.4 (347.9) 415.7 635.3 (219.6) Other income, net 4.8 2.7 2.1 10.6 6.7 3.9 Net loss $ (215.7) $ (565.7) $ (350.0) $ (405.1) $ (628.6) $ (223.5) Research and Development Expenses The table below summarizes our research and development expenses by category for the three and six months ended June 30, 2026 and 2025, respectively. Three Months Ended June 30, Six Months Ended June 30, (in millions) 2026 2025 $ Change 2026 2025 $ Change Third-party research and development expenses: Clinical trial related expenses $ 67.5 $ 30.6 $ 36.9 $ 121.8 $ 53.4 $ 68.4 Expenses related to manufacturing and purchasing of clinical trial related materials 38.5 32.2 6.3 66.8 40.6 26.2 Other external research and development expenses 8.3 5.0 3.3 15.9 10.2 5.7 Internal research and development expenses: Compensation related costs, excluding stock-based compensation 19.3 11.6 7.7 37.3 22.4 14.9 Stock-based compensation 24.1 128.6 (104.5) 48.5 132.7 (84.2) Total $ 157.7 $ 208.0 $ (50.3) $ 290.3 $ 259.3 $ 31.0 Research and development expenses decreased $50.3 million during the three months ended June 30, 2026 and increased $31.0 million during the six months ended June 30, 2026, respectively, compared to the same periods in the prior year. The increase in third-party research and development expenses for the three and six months ended June 30, 2026, was primarily driven by a $36.9 million and $68.4 million increase in clinical trial related expenses, respectively, a $6.3 million and $26.2 million increase in expenses related to manufacturing and purchasing of clinical trial related materials as a result of increased enrollment in our HARMONi-3, HARMONi-7, and HARMONi-GI3 trials, respectively, and a $3.3 million and $5.7 million increase in other external research and development expenses, respectively. The decrease in internal research and 30 development expenses for the three and six months ended June 30, 2026, was primarily driven by a $104.5 million and $84.2 million decrease in stock-based compensation expense respectively, as a result of the modification to our performance-based stock option awards during the second quarter of 2025, which is offset by a $7.7 million and $14.9 million increase in compensation related costs, excluding stock-based compensation, respectively, as we continue to hire additional resources to support the clinical development of ivonescimab. We expect research and development expenses to continue to increase as we progress with the development of ivonescimab. General and Administrative Expenses The table below summarizes our general and administrative expenses by category for the three and six months ended June 30, 2026 and 2025, respectively. Three Months Ended June 30, Six Months Ended June 30, (in millions) 2026 2025 $ Change 2026 2025 $ Change Compensation related costs, excluding stock-based compensation $ 8.7 $ 5.2 $ 3.5 $ 17.1 $ 10.2 $ 6.9 Stock-based compensation 44.6 350.2 (305.6) 93.0 357.2 (264.2) Legal fees and professional services 6.5 3.2 3.3 11.1 6.0 5.1 Other general and administrative expenses 3.0 1.8 1.2 4.2 2.6 1.6 Total $ 62.8 $ 360.4 $ (297.6) $ 125.4 $ 376.0 $ (250.6) General and administrative expenses decreased by $297.6 million and $250.6 million for the three and six months ended June 30, 2026 respectively, compared to the same periods in the prior year. The decrease was primarily driven by a $305.6 million and $264.2 million decrease in stock-based compensation respectively, as a result of the modification to our performance-based stock option awards during the second quarter of 2025. In addition, compensation related costs, excluding stock-based compensation, increased by $3.5 million and $6.9 million for the three and six months ended June 30, 2026 respectively, compared to the same periods in the prior year due to increased headcount. Additionally, legal fees and professional services increased by $3.3 million and $5.1 million for the three and six months ended June 30, 2026 respectively, compared to the same periods in the prior year to continue supporting the development of ivonescimab. We expect general and administrative expenses to continue to increase as we scale our infrastructure and increase our headcount to support the development of ivonescimab. Other Income, net The table below summarizes our other income by category for the three and six months ended June 30, 2026 and 2025, respectively. Three Months Ended June 30, Six Months Ended June 30, (in millions) 2026 2025 $ Change 2026 2025 $ Change Foreign currency (loss) gain $ (0.1) $ (0.2) $ 0.1 $ (0.2) $ (0.1) $ (0.1) Investment income 4.4 3.0 1.4 10.3 6.8 3.5 Other (1) 0.5 (0.1) 0.6 0.5 — 0.5 Total $ 4.8 $ 2.7 $ 2.1 $ 10.6 $ 6.7 $ 3.9 (1) In June 2026, the Company entered into an asset purchase agreement (the “APA”) with a third party. Pursuant to the APA, the Company sold the asset relating to the pharmaceutical compound known as ridinilazole. In consideration for such assignment of rights, the third party has made an upfront non-refundable payment to the Company of $0.5 million. Additionally, the third party has also agreed to make additional payments totaling $1.5 million that are contingent upon the 31 achievement of certain regulatory milestones, sales-based milestone payments of up to $103 million, as well as quarterly royalty payments that are based on a single digit percentage of net sales for certain products covered by the assigned and transferred patent rights. The Company did not have any amounts capitalized related to the underlying portfolio of patents, nor was any write-down of assets recorded upon executing the APA. The Company received the payment of $0.5 million from the third party in June 2026 and recognized the $0.5 million within other income, net on the condensed consolidated statements of operations and comprehensive loss for the three and six months ended June 30, 2026. The Company does not have any ongoing obligations associated with the APA. As of June 30, 2026, the Company is unable to estimate the timing or likelihood of achieving the regulatory milestone payments, sales-based milestone payments, and the quarterly royalty payments. For the three and six months ended June 30, 2026, other income, net increased by $2.1 million and $3.9 million, compared to the same periods in the prior year, primarily due to an increase of $1.4 million and $3.5 million in investment income due to higher cash equivalents and short-term investments balance, respectively. Liquidity, Capital Resources and Going Concern Going Concern During the three and six months ended June 30, 2026, we incurred a net loss of $215.7 million and $405.1 million and cash flows used in operating activities for the six months ended June 30, 2026 was $263.4 million. As of June 30, 2026, we had an accumulated deficit of $2,699.3 million, cash and cash equivalents of $419.4 million and short-term investments of $271.3 million. We expect to continue to generate operating losses for the foreseeable future. Our cash and cash equivalents and short-term investments are not sufficient to fund our planned operations for a period of at least one year from the date these unaudited condensed consolidated financial statements are issued. Until we can generate substantial revenue and achieve profitability, we will need to raise additional capital to fund our ongoing operations and capital needs. We continue to evaluate options to further finance our operating cash needs for our product candidates through a combination of some, or all, of the following: equity and debt offerings, collaborations, strategic alliances, grants and clinical trial support from government entities, philanthropic, non-government and not-for-profit organizations, and marketing, distribution or licensing arrangements. There is no assurance, however, that additional financing will be available when needed or that we will be able to obtain financing on terms acceptable to us. If we are unable to obtain funding when required in the future, we could be required to delay or reduce research and development programs, product portfolio expansion, or future commercialization efforts, which could adversely affect our business prospects. These conditions raise substantial doubt about our ability to continue as a going concern. Sources of Liquidity As of June 30, 2026, we have financed our operations primarily through issuances of our common stock, including our most recent private placements issued in October 2025 and September 2024 for gross proceeds of $500.0 million and $235.0 million, respectively, and the raise of $381.6 million gross proceeds from our Distribution Agreement since inception, issuance of debt, and receipt of payments to us under license and collaboration arrangements. The remaining gross proceeds available under the Distribution Agreement as of June 30, 2026 was approximately $68.4 million which was utilized subsequent to June 30, 2026. We have devoted substantially all of our efforts to research and development, including clinical trials. We have not completed the development of any drugs. We expect to continue to incur significant expenses and increasing operating losses for at least the next few years. The net losses we incur may fluctuate significantly from quarter to quarter and year to year, due to the nature and timing of our research and development activities. We expect that our research and development and general and administrative expenses will continue to be significant in connection with our ongoing research and development efforts. In addition, if we obtain marketing approval for any of our product candidates in the United States or other jurisdictions where we retain commercial rights, and if we choose to retain those rights, we would expect to incur significant sales, marketing, distribution and outsourced manufacturing expenses, as well as ongoing research and development expenses. In addition, our expenses will increase if and as we: 32 •invest in clinical development of ivonescimab in our Licensed Territory; •conduct research and continue development of additional product candidates; •maintain and augment our intellectual property portfolio and opportunistically acquire complementary intellectual property; •seek further regulatory advancement for ivonescimab; •invest in our manufacturing capabilities for ivonescimab and any other products for which we may obtain regulatory approval; •seek marketing approvals for any product candidates that successfully complete clinical development; •ultimately establish a sales, marketing and distribution infrastructure in jurisdictions where we have retained commercialization rights and scale up external manufacturing capabilities to commercialize any product candidates for which we receive marketing approval; •perform our obligations under our collaboration agreements; •pursue business development opportunities, including investing in other businesses, products and technologies; •experience any delays or encounter any issues with any of the above, including but not limited to failed studies, complex results, safety issues or other regulatory challenges •hire additional clinical, regulatory, scientific and administrative personnel; •expand our physical presence; •add operational, financial and management information systems and personnel, including personnel to support our product development and planned future commercialization efforts; and •borrow capital to fund our resources and have to pay interest expenses on such borrowings. From time to time, we may raise additional equity or debt capital through both registered offerings off of a shelf registration, including ATM offerings, and private offerings of securities. On February 20, 2024, we filed a shelf registration statement on Form S-3 with the SEC, which the SEC declared effective on February 27, 2024. Through our shelf registration statement we may, from time to time, sell up to an aggregate of $450 million of our common stock, preferred stock, debt securities, depository shares, warrants, subscription rights, purchase contracts, or units. Of the $450 million of liquidity available to us under this shelf registration statement, on May 13, 2024, we had established an ATM offering program with J.P. Morgan Securities LLC, as sales agent, in the amount of up to $90.0 million. On August 11, 2025, we entered into the Amendment to the Original Distribution Agreement. Pursuant to the Amendment, the Original Distribution Agreement was amended to, among other things, increase the aggregate offering price of shares of the Company’s common stock, par value $0.01 per share, from time to time, through the sales agent, by up to an additional $360.0 million. The remaining gross proceeds available under the Distribution Agreement as of June 30, 2026 was approximately $68.4 million which was utilized subsequent to June 30, 2026. In addition to the payments already made to Akeso under the License Agreement and Second Amendment, there are additional potential milestone payments of $4.56 billion, as Akeso will be eligible to receive regulatory milestones of up to $1.05 billion and commercial milestones of up to $3.51 billion. In addition, Akeso will be eligible to receive low double-digit royalties on net sales. Until we can generate substantial revenue and achieve profitability, we will need to raise additional capital to fund ongoing operations and capital needs, including the payment of the milestone payments referenced above. We have based the foregoing estimate on assumptions that may prove to be wrong, and we could use our capital resources sooner than we currently expect. This estimate assumes, among other things, that we do not obtain any additional funding through grants and clinical trial support or through new collaboration arrangements. Our future capital requirements will depend on many factors, including: •the costs, timing and outcome of clinical trials required for clinical development of ivonescimab; •the number and development requirements of other future product candidates that we pursue; •the costs, timing and outcome of regulatory review of ivonescimab and/or our other product candidates we develop; •the costs and timing of commercialization activities, including product sales, marketing, distribution and manufacturing, for any of our product candidates that receive marketing approval; 33 •the extent to which we become liable for milestone payments under the License Agreement and Second Amendment for ivonescimab; •subject to receipt of marketing approval, revenue received from commercial sales of any product candidates; •the costs and timing of preparing, filing and prosecuting patent applications, maintaining and protecting our intellectual property rights and defending against any intellectual property-related claims; •our ability to establish and maintain collaborations, licensing or other arrangements and the financial terms of such arrangements; •the extent to which we acquire or invest in other businesses, products and technologies; •the rate of the expansion of our physical presence; and •the extent to which we change our physical presence. Until such time, if ever, as we can generate substantial product revenues, we expect to finance our cash needs through a combination of some, or all, of the following: equity and debt offerings, collaborations, strategic alliances, grants and clinical trial support from government entities, philanthropic, non-government and not-for-profit organizations, and marketing, distribution or licensing arrangements. We will need to seek additional funding in the future to fund operations. Additional capital, when needed, may not be available to us on acceptable terms, or at all. To the extent that we raise additional capital through the sale of equity or convertible debt securities, the ownership interest of our existing stockholders may be diluted, and the terms of these securities may include liquidation or other preferences that adversely affect the rights of our existing stockholders. Additional debt financing, if available, may involve agreements that include covenants limiting or restricting our ability to take specific actions, such as incurring additional debt, making capital expenditures or declaring dividends or other distributions. If we raise additional funds through collaborations, strategic alliances or marketing, distribution, or licensing arrangements with third parties, we may have to relinquish valuable rights to our technologies, future revenue streams, research programs or product candidates or to grant licenses on terms that may not be favorable to us. As of the date of this Quarterly Report on Form 10-Q, additional capital has not been secured. If we are unable to raise additional funds through equity or debt financings or other arrangements when needed, we may be required to delay, limit, reduce or terminate our product development or future commercialization efforts or grant rights to develop and market product candidates that we would otherwise prefer to develop and market ourselves, which could materially adversely affect our business, operating results and financial condition and our ability to continue operations. Cash Flows The following table summarizes our cash flows for the six months ended June 30, 2026 and 2025: Six Months Ended June 30, (in millions) 2026 2025 Net cash used in operating activities $ (263.4) $ (127.9) Net cash provided by investing activities $ 222.7 $ 310.9 Net cash provided by financing activities $ 234.9 $ 9.9 Operating Activities Net cash used in operating activities for the six months ended June 30, 2026 was $263.4 million and primarily consisted of a net loss of $405.1 million and a $7.1 million net change in operating assets and liabilities, partially offset by non-cash charges of $134.6 million. The non-cash charges primarily consisted of $141.5 million of stock-based compensation driven by the modification to outstanding performance-based stock option awards which removed the performance-based vesting criteria, partially offset by $7.2 million relating to amortization of the discount on short-term investments in U.S. government treasury bills. The net change in operating assets and liabilities was primarily due to a $33.0 million increase in accrued liabilities and a $2.9 million increase in accounts payable, offset by a $23.0 million increase in prepaid expenses and other current assets, a $1.2 million increase in other assets, and a $5.5 million decrease in accrued compensation. 34 Net cash used in operating activities for the six months ended June 30, 2025 was $127.9 million and primarily consisted of a net loss of $628.6 million and a $15.2 million net change in working capital, partially offset by non-cash charges of $485.5 million. The non-cash charges primarily consisted of $489.9 million of stock-based compensation driven by the modification to outstanding performance-based stock option awards which removed the performance-based vesting criteria, partially offset by $4.0 million relating to amortization of the discount on short-term investments in U.S. Treasury securities. The net change in working capital was primarily due to a $18.3 million increase in accounts payable and a $6.5 million increase in accrued liabilities, partially offset by a $5.4 million decrease in accrued compensation and a $3.7 million increase in other assets. Investing Activities Net cash provided by investing activities for the six months ended June 30, 2026 was $222.7 million and primarily driven by $626.1 million in maturities and sales of short-term investments, offset by $402.3 million in purchase of short-term investments and $1.2 million in purchases of property and equipment. Net cash provided by investing activities for the six months ended June 30, 2025 was $310.9 million and was primarily due to $311.3 million received from maturities of short-term investments in U.S. Treasury securities. Financing Activities Net cash provided by financing activities for the six months ended June 30, 2026 was $234.9 million and was driven by $227.4 million net proceeds from our current Distribution Agreement and $7.5 million of proceeds received related to employee stock awards and purchase plans. Net cash provided by financing activities was $9.9 million for the six months ended June 30, 2025, and was due to $7.3 million of proceeds received related to the exercise of warrants and $2.6 million of proceeds received related to employee stock awards and purchase plans. Critical Accounting Policies and Significant Judgments and Estimates Our management’s discussion and analysis of our financial condition and results of operations are based on our unaudited condensed consolidated financial statements, which have been prepared in accordance with U.S. GAAP. The preparation of our financial statements requires us to make estimates and judgments that affect the reported amounts of assets, liabilities, and expenses and the disclosure of contingent liabilities in our financial statements. On an ongoing basis, we evaluate our estimates and judgments, including those related to research and development expenses, stock-based compensation and income taxes. We base our estimates on historical experience, known trends and events, and various other factors that we believe to be reasonable under the circumstances, the results of which form the basis for making judgments about the carrying values of assets and liabilities that are not readily apparent from other sources. Actual results may differ from these estimates under different assumptions or conditions. Our significant accounting policies are described in Item 7. Management's Discussion and Analysis of Financial Condition and Results of Operations, and in Critical Accounting Policies and Significant Judgments and Estimates in our Annual Report. There have been no material changes to our critical accounting policies and estimates that were disclosed in our Annual Report. Except as set forth in Note 12, Commitments and Contingencies, to our unaudited condensed consolidated financial statements included in this Quarterly Report on Form 10-Q, there have been no material changes from the contractual obligations and commitments as of December 31, 2025 previously disclosed in our Annual Report on Form 10-K filed with the SEC on February 23, 2026. We did not have during the periods presented, and we do not currently have, any off-balance sheet arrangements, as defined in the rules and regulations of the SEC. Recently Issued Accounting Pronouncements 35 For a discussion of recently issued accounting pronouncements, refer to Note 2, Summary of Significant Accounting Policies and Recent Accounting Pronouncements, to our unaudited condensed consolidated financial statements included in this Quarterly Report on Form 10-Q.

Quantitative and Qualitative Disclosures About Market Risk

Our primary exposures to market risk are liquidity risk and foreign currency risk. Liquidity Risk We have funded our operations since inception primarily through the issuance of equity and debt securities. We have also received funding from our license and collaboration arrangements. Until such time as we can generate significant revenue from product sales, if ever, we expect to finance our operations through a combination of public or private equity or debt financings or other sources. Adequate additional financing may not be available to us on acceptable terms, or at all. Our inability to raise capital as and when needed would have a negative impact on our financial condition and our ability to pursue our business strategy. Foreign Currency Exchange Rate Risk Foreign currency exchange rate risk refers to the risk that the value of a financial commitment or recognized asset or liability will fluctuate due to changes in foreign currency rates. Our net loss and financial position, as expressed in U.S. dollars, are exposed to movements in foreign exchange rates against the pound sterling and the euro. The main trading currencies are the pound sterling, the U.S. dollar, Japanese Yen, and the euro. We are exposed to foreign currency exchange rate risk as a result of entering into operating transactions denominated in currencies other than the functional currency of our subsidiaries, particularly in relation to our monetary assets and liabilities relating to intercompany transactions, supplier liabilities and the translation of foreign cash balances. Operating transaction foreign currency gains and losses are included in the determination of net loss in our statements of operations and comprehensive loss. We monitor our exposure to foreign currency exchange rate risk. Exposures are generally managed through natural hedging via the currency denomination of cash balances and any impact currently is not material to us. Interest Rate Risk We hold our cash, cash equivalents and short-term investments for working capital purposes. Some of the securities we invest in are subject to market risk. This means that a change in prevailing interest rates may cause the principal amount of such investments to fluctuate. To minimize this risk, we maintain our portfolio of cash, cash equivalents and short-term investments which are invested in a variety of short-term securities, including money market funds and investments in U.S. treasury securities. Due to the short-term nature of these instruments, we believe that we do not have any material exposure to changes in the fair value of our investment portfolio as a result of changes in interest rates. Declines in interest rates, however, would reduce future interest income. The effect of a hypothetical 10% increase or decrease in overall interest rates would not have had a material impact on our operating results or the total fair value of our portfolio. Credit Risk We consider all of our material counterparties to be creditworthy. We consider the credit risk for each of our counterparties to be low and do not have a significant concentration of credit risk at any of our counterparties. We have $0.6 million of research and development tax credits outstanding at June 30, 2026. Given that these receivables relate to the United Kingdom research and development tax credit cash rebate regimes and given our history of collection, it is highly unlikely that these amounts will not be collected.

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Legal Proceedings

From time to time, we may become involved in legal proceedings arising in the ordinary course of our business. Except as described below, we are not aware of any legal proceedings arising outside the ordinary course of business. Litigation Relating to the December 2022 Notes Entered into in Connection with the License Agreement On March 17, 2025, Rainaldi Revocable Trust, a purported stockholder of the Company, filed a derivative lawsuit in the Delaware Court of Chancery against certain of the Company’s current and former directors and the Company, solely as a nominal defendant, concerning the December 2022 Notes entered into by the Company, Mr. Duggan and Dr. Zanganeh in connection with the License Agreement. The suit asserts claims for breach of fiduciary duty and unjust enrichment and seeks, among other things, unspecified damages, rescission of the shares that Mr. Duggan and Dr. Zanganeh received as part of prepaid interest payments under the December 2022 Notes, as well as attorneys’ fees and costs. Pursuant to the December 2022 Notes, the Company obtained $520 million in bridge financing through three unsecured promissory notes: (1) a $400 million note issued to Mr. Duggan due on February 15, 2023; (2) a $20 million note issued to Dr. Zanganeh due on February 15, 2023; and (3) a $100 million note issued to Mr. Duggan due on September 15, 2023 (the “$100 Million Note”). The notes had an interest rate of 7.5% through February 15, 2023, with prepaid interest through that date paid in shares valued at $0.7913 per share. For periods after February 15, 2023, interest would accrue at the U.S. prime interest rate plus 50 basis points for three months, and thereafter at the U.S. prime rate plus 300 basis points. The notes contained no warrant coverage and no security interests. The Company announced the 2023 Rights Offering on December 6, 2022, which ran from February 7 through March 1, 2023. The 2023 Rights Offering was fully subscribed, with stockholders purchasing 476,190,471 shares of the Company’s common stock at $1.05 per share, raising $500 million in gross proceeds. Mr. Duggan and Dr. Zanganeh fully subscribed to their basic subscription rights, with Mr. Duggan participating by purchasing 376,489,880 shares for approximately $395.31 million. Following the Company’s fully subscribed $500 million 2023 Rights Offering, Dr. Zanganeh’s $20 million note was repaid on February 15, 2023, and Mr. Duggan's $400 million note was repaid. In the interest of minimizing stockholders dilution, the $100 Million Note was extended, and eventually the $75.5 million repayment was funded through the proceeds of the securities purchase agreements the Company entered into with multiple biotech institutional investors and individual accredited investors (the "September 2024 Private Placement") in which Mr. Duggan purchased 3,325,991 shares for an aggregate purchase price of $75.5 million as a participant in the September 2024 Private Placement at a purchase price of $22.70 per share, and the remaining $24.5 million was repaid in full on October 1, 2024, along with $7.3 million in accrued interest. Defendants’ motion to dismiss the complaint was filed on May 16, 2025 (the “Motion to Dismiss”). Plaintiff filed a motion to certify certain constitutional questions to the Delaware Supreme Court on May 29, 2025 (the “Motion to Certify”). Defendants agreed to a stipulation staying briefing on the Motion to Certify and the Motion to Dismiss pending the Delaware Supreme Court’s decision in another case involving substantially the same constitutional questions. On June 18, 2025, the Court granted such stipulation. The Delaware Supreme Court's decision came down on February 27, 2026. The briefing schedule for the Motion to Dismiss was filed by the parties with the courts on April 16, 2026. On May 27, 2026, Plaintiff and the Defendants stipulated to voluntary dismissal of Plaintiff’s claims with prejudice as to Plaintiff and without prejudice as to any other stockholder of the Company, and the Court approved that dismissal the same day. European Patent Opposition On June 18, 2025, an unknown third party (the “Opponent”) filed a notice of opposition against the Company’s in-licensed EP3882275B1 patent (the “’275 patent”) in the European Opposition Division of the European Patent Office (“EPO”). The ’275 patent covers Ivonescimab. The notice primarily asserts that the ’275 patent lacks inventive step. The Company contests these assertions and worked with its collaboration partner, Akeso, to timely file a response before the European Opposition Division of the EPO on January 2, 2026. The Opponent has filed a reply on March 25, 2026 and Summit and Akeso filed a response to the reply on May 8, 2026. An anonymous Third Party Observation (“TPO”) was filed on June 8, 2026. Summit and Akeso filed a reply on June 22, 2026. Another anonymous TPO was filed on June 24, 2026. 38

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Risk Factors

An investment in our common stock or other securities involves a number of risks. In addition to other information set forth in this Quarterly Report on Form 10-Q, you should carefully consider each of the risks described in our Annual Report, which includes a detailed discussion of the Company’s risk factors. If any of the risks described therein or other uncertainties currently unknown to us, or that we currently deem to be immaterial, develop into actual events, our business, financial condition, or results of operations could be negatively affected, the market price of our common stock or other securities could decline, and you may lose all or part of your investment. We do not currently have sufficient working capital to fund our planned operations for the next twelve months. There is uncertainty regarding our ability to raise additional capital and as such, there is substantial doubt regarding our ability to continue as a going concern. Our unaudited financial statements have been prepared under the assumption that we would continue as a going concern. However, we have concluded that there is substantial doubt about our ability to continue as a going concern, because without additional sources of funding, our cash and cash equivalents and short-term investments at June 30, 2026 are not sufficient for us to fund our working capital needs for the next twelve months after the date that the unaudited financial statements included in this Quarterly Report on Form 10-Q are issued. Management’s plans concerning these matters, including raising additional capital, are described in Part I - Item 2 – Management’s Discussion and Analysis of Financial Condition and Results of Operation - Liquidity and Capital Resources – Sources of Liquidity of our unaudited financial statements included within this Quarterly Report on Form 10-Q. We continue to evaluate options to further finance our operating cash needs for our product candidates through a combination of some, or all, of the following: equity and debt offerings, collaborations, strategic alliances, grants and clinical trial support from government entities, philanthropic, non-government and not-for-profit organizations, and marketing, distribution or licensing arrangements. However, we cannot guarantee that we will be able to obtain any or sufficient additional funding or that such funding, if available, will be obtainable on terms satisfactory to us. If we are unable to raise capital in the near term or on attractive terms, we could be forced to delay or reduce our research and development programs or any future commercialization efforts, or even curtail or cease operations. There have been no material changes to the risk factors disclosed in Item 1A of our Annual Report other than disclosed above.

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