a20260723q2earningsdeck

Summit Therapeutics Q2 2026 Earnings Call July 23, 2026 4:30pm ET

Forward-Looking Statements Any statements in this presentation about uncertainties related to market conditions, the Company’s future expectations, plans and prospects, including but not limited to, statements about the clinical and preclinical development of the Company’s product candidates, entry into and actions related to the Company’s partnership with Akeso Inc., and other collaborations, the intended use of the net proceeds from the private placements the Company's anticipated spending and cash runway, the therapeutic potential of the Company’s product candidates, the potential commercialization of the Company’s product candidates, the timing of initiation, completion and availability of data from clinical trials, the potential submission of applications for marketing approvals, the expected timing of BLA submissions or FDA decisions, potential acquisitions, the size and gross proceeds about this offering program, the satisfaction of customary closing conditions related to the offering and sale of securities, the grant to the underwriters of an option to purchase additional shares and the Company’s ability to complete the offering, statements about the disclosed At-The-Market equity offering program (“ATM Program”), the expected proceeds and uses thereof, the Company’s estimates regarding stock-based compensation, and other statements containing the words "anticipate," "believe," "continue," "could," "estimate," "expect," "intend," "may," "plan," "potential," "predict," "project," "should," "target," "would," and similar expressions, constitute forward-looking statements within the meaning of The Private Securities Litigation Reform Act of 1995. Actual results may differ materially from those indicated by such forward-looking statements as a result of various important factors, including the Company’s ability to sell shares of our common stock under the ATM Program, the conditions affecting the capital markets, and the satisfaction of closing conditions related to the proposed public offering, the grant to the underwriters of the option to purchase additional shares, timing and size of the proposed offering and Summit’s intended use of proceeds therefrom, general economic, industry, or political conditions, including the effects of geopolitical developments, domestic and foreign trade policies, and monetary policies, the results of our evaluation of the underlying data in connection with the development and commercialization activities for ivonescimab, the outcome of discussions with regulatory authorities, including the Food and Drug Administration, the uncertainties inherent in the initiation of future clinical trials, availability and timing of data from ongoing and future clinical trials, the results of such trials, and their success, global public health crises, that may affect timing and status of our clinical trials and operations, whether preliminary results from a clinical trial will be predictive of the final results of that trial or whether results of early clinical trials or preclinical studies will be indicative of the results of later clinical trials, whether business development opportunities to expand the Company’s pipeline of drug candidates, including without limitation, through potential acquisitions of, and/or collaborations with, other entities occur, expectations for regulatory approvals, laws and regulations affecting government contracts and funding awards, availability of funding sufficient for the Company’s foreseeable and unforeseeable operating expenses and capital expenditure requirements and other factors discussed in the "Risk Factors" and “Management’s Discussion and Analysis of Financial Condition and Results of Operations” sections of filings that the Company makes with the Securities and Exchange Commission. Summit defines a “positive study” as a clinical study that with one or more prespecified primary endpoints in which one of those endpoints achieves a statistically significant benefit according to the protocol or statistical analysis plan. Any change to our ongoing trials could cause delays, affect our future expenses, and add uncertainty to our commercialization efforts, as well as to affect the likelihood of the successful completion of clinical development of ivonescimab. Accordingly, readers should not place undue reliance on forward-looking statements or information. In addition, any forward-looking statements included in this presentation represent the Company’s views only as of the date of this release and should not be relied upon as representing the Company’s views as of any subsequent date. The Company specifically disclaims any obligation to update any forward-looking statements included in this presentation. 2 Summit Proprietary Information - Do Not Copy or Distribute Q2 2026 Earnings Presentation | 7/2026

Ivonescimab: By The Numbers Ivonescimab is an investigational therapy not presently approved by any regulatory authority other than China’s National Medical Products Administration (NMPA). Ivonescimab is an investigational therapy not presently approved by any regulatory authority other than China’s National Medical Products Administration (NMPA). Positive Phase III Readouts to Date The only in-class Phase III Readouts Phase III Trials in Multiple Tumor Types Patients Dosed in All Clinical Trials Indications Approved in China by the NMPA 2 Chinese Approvals3 Patients Dosed Commercially in China Total Ivonescimab Trials Sponsored by Summit, Akeso, or via Collaboration Total Trials Involving Ivonescimab on clinicaltrials.gov 4 Phase III Trials with Positive Results 15 Phase III Trials1 >4,000 Trial Patients2 >70,000 Commercial Patients in China3 52 Sponsored Trials1 171 Total Trials1 Anti-VEGF Anti-PD-1 Most Advanced, First-in-Class, PD-1/VEGF Bispecific Antibody Abbreviations: PD-1=programmed cell death protein 1; VEGF=vascular endothelial growth factor; NMPA = National Medical Products Administration (China) References: 1. Total sponsored (by Summit, Akeso, or GORTEC) clinical trials as of July 16, 2026, via clinicaltrials.gov or public announcement; 2. Data on File 56, 57. Summit Therapeutics Inc. 3. Akeso March 27, 2026 press release, Akeso Reports Full-Year 2025 Financial Results 3 Summit Proprietary Information - Do Not Copy or Distribute Q2 2026 Earnings Presentation | 7/2026

Abbreviations: 1L=first-line; 2L=second-line; BTC=biliary tract cancer; Chemo=chemotherapy; CPS=combined positive score; CRC=colorectal cancer; EGFRm+=epidermal growth factor receptor mutant positive; GEJ=gastroesophageal junction; GORTEC=Groupe Oncologie Radiotherapie Tete et Cou; HCC=hepatocellular carcinoma; HNSCC=head and neck squamous cell carcinoma; mAb=monoclonal antibody; NSCLC=non-small cell lung cancer; OC=ovarian cancer; PD-L1=programmed cell death-ligand 1; PDAC=pancreatic ductal adenocarcinoma; SCLC=small cell lung cancer; TGF-β=transforming growth factor beta; TIGIT=T cell immunoreceptor with Ig and ITIM domains; TKI=tyrosine kinase inhibitor; TNBC=triple negative breast cancer; vs.=versus. * ILLUMINE is a cooperative group study between GORTEC (global lead and EU Sponsor), Akeso (collaborator and China Sponsor), and Summit (collaborator) In HARMONi: Summit + Akeso Ivonescimab Pipeline with 15 Phase IIIs FOCUS AREA STUDY LINE & INDICATION REGIMEN STATUS Approved PHASE 1 2 3 These ivonescimab clinical studies are being conducted in China and/or Australia and are fully sponsored and managed by Akeso. Approvedivonescimab + chemo vs. placebo + chemoAdvanced EGFRm+ NSCLC Post-TKI Lung Cancer Approvedivonescimab vs. pembrolizumab1L metastatic NSCLC (PD-L1 positive) Active, Not Recruitingivonescimab + chemo vs. tislelizumab + chemo1L advanced or metastatic squamous NSCLC Recruiting ivonescimab + docetaxel vs. placebo + docetaxel 2L advanced or metastatic NSCLC progressed on or after PD-L1 therapy Recruitingivonescimab vs. placebo Consolidation treatment SCLC not progressed after chemoradiation Active, Not Recruitingivonescimab vs. ivonescimab + chemo Resectable NSCLCAK112-205 Active, Not Recruiting ivonescimab + cadonilimab ± chemo1L advanced or metastatic NSCLC AK112-208 Recruiting ivonescimab + nab-paclitaxel vs. placebo + nab-paclitaxel 1L inoperable locally advanced / metastatic TNBC (PD-L1 CPS<10) Breast Cancer Recruiting ivonescimab ± chemo ± cadonilimab2L OCAK104-221 Gynecologic Cancer Recruiting ivonescimab ± chemo ± olaparib1L platinum-sensitive OCAK112-211 Recruiting ivonescimab + AK117 vs. placebo + pembrolizumab 1L recurrent or metastatic HNSCC with PD-L1 positive (CPS ≥1) Head and Neck Cancer Active, Not Recruiting ivonescimab + chemo vs. durvalumab + chemo 1L unresectable locally advanced or metastatic BTC Gastrointestinal Cancer Recruiting ivonescimab + chemo ± AK117 vs. placebo + chemo 1L metastatic PDAC Recruiting ivonescimab + chemo vs. bevacizumab + chemo 1L metastatic CRC Recruiting ivonescimab ± anti-TIGIT antibody ± cadonilimab ± anti-TIGIT/TGF-β vs. sintilimab + bevacizumab 1L advanced HCCAK112-209 Active, Not Recruiting anti-CD73 mAb + ivonescimab ± chemo1L or 2L microsatellite stable CRCAK119-202 Recruiting ivonescimab ± anti-TIGIT/TGF-β or ivonescimab 2L advanced BTCAK130-201 Completedivonescimab + ligufalimab ± chemo 1L or 2L advanced or metastatic NSCLC, GEJ, BTC, PDAC AK117-202 Various Cancers Active, Not Recruiting ivonescimab + anti-TIGIT antibody1L advanced malignant tumorsAK127-104 Active, Not Recruitingivonescimab + chemo vs. placebo + chemoAdvanced EGFRm+ NSCLC Post-TKI Lung Cancer Recruiting ivonescimab + chemo vs. pembrolizumab + chemo1L metastatic NSCLC Recruiting ivonescimab vs. pembrolizumab1L metastatic PD-L1 high (≥50%) NSCLC Recruitingivonescimab + chemo vs. bevacizumab + chemo1L metastatic CRCColorectal Cancer Supportive Phase 1 and 2 clinical studies are sponsored by our partner Akeso. Recruitingivonescimab ± ligufalimab vs. pembrolizumab 1L recurrent or metastatic PD-L1 positive HNSCC (CPS ≥1) ILLUMINE (GORTEC 2024-04) Head and Neck Cancer Cooperative Group Study* A d d it io n a l O p p o rt u n it y G lo b a ll y Ivonescimab is an investigational therapy not presently approved by any regulatory authority other than China’s National Medical Products Administration (NMPA). Ivonescimab is an investigational therapy not presently approved by any regulatory authority other than China’s National Medical Products Administration (NMPA).4 Summit Proprietary Information - Do Not Copy or Distribute Q2 2026 Earnings Presentation | 7/2026

Maturing Data Reinforces Regional Consistency of Ivonescimab Efficacy • Efficacy is consistent across geographic regions with longer follow-up • OS HR continues to improve with longer follow-up for Western patients • Consistent safety profile with previous Phase III results of ivonescimab + chemo Asian pts, N=273Western pts, N=165 ITT, N=438 32.7 months29.2 months29.7 months Analysis: Apr 2025, mFU time 0.760.980.79 (0.62-1.01) , p=0.057 0HR (95% CI) , p-value 32.7 months213.7 months29.7 months Analysis: Sep 2025, mFU time 0.760.840.78 (0.62-0.98), p=0.0332 (nominal)HR (95% CI) , p-value 32.7 months223.2 months329.9 months3Analysis: Jun 2026, mFU time 0.760.7630.763HR1 References: 1. Additional details intended to be provided at a medical meeting, including confidence intervals, median OS, and p-value for the ITT population. 2. Data cut-off for Asian pts locked at April 2025 for each analysis. 3. Summit press release, July 22, 2026. Note: All p values are two-sided. Abbreviations: mFU = median follow-up, CI = confidence interval, HR = hazard ratio, ITT = intention-to-treat, pts = patients. Summit Proprietary Information - Do Not Copy or Distribute Q2 2026 Earnings Presentation | 7/2026 5

China Ivonescimab Clinical Questions Answered Global References: 1. Goldman J, et al. HARMONi. Presented at WCLC 2025.; 2. Zhang L, et al. Final OS Analysis: HARMONi-A. Presented at SITC 2025.; 3. Summit Press Release. April 25, 2025.; 4. Lu S, et al. HARMONi-6. Presented at ESMO 2025.; 5. Chen Z, et al. Lancet. 2025;406(10515):2078-2088. Abbreviations: 1L=first-line; 2L=second-line; Chemo=chemotherapy; EGFRm+=epidermal growth factor receptor mutant positive; NSCLC=non-small-cell lung cancer; HR=hazard ratio; OS=overall survival; PFS=progression-free survival; vs.=versus. Reference: ClinicalTrials.gov Positive China PFS Translates to RoW PFS Ivonescimab + Chemo vs. Chemo in EGFRm NSCLC Post-TKI 1 Significant OS data achieved in China studies Strong OS Trends, HR <0.80 Ivonescimab + Chemo vs. Chemo in EGFRm NSCLC Post-TKI 2 Ivonescimab + Chemo vs. Tislelizumab + Chemo in 1L NSCLC 4,5 Ivonescimab is an investigational therapy not presently approved by any regulatory authority other than China’s National Medical Products Administration (NMPA). Ivonescimab is an investigational therapy not presently approved by any regulatory authority other than China’s National Medical Products Administration (NMPA).6 Summit Proprietary Information - Do Not Copy or Distribute Q2 2026 Earnings Presentation | 7/2026

Ivonescimab Development Plan Ivonescimab Development: Summit Pipeline References: 1. In Summit license territories, Data on File 55. Summit Therapeutics Inc. Supported = at a minimum, a notification of support communicated to PI; 2. Publications available at smmttx.com, Accessed on July 22, 2026. Abbreviations: 1L=first-line; 2L=second-line; ADC=antibody drug conjugate; ccRCC=clear cell renal cell carcinoma; Chemo=chemotherapy; CRC=colorectal cancer; EGFRm+=epidermal growth factor receptor mutation positive; ISTs=Investigator Sponsored Trials; HNSCC=head and neck squamous cell carcinoma; NSCLC=non- small-cell lung cancer; PDAC=pancreatic ductal adenocarcinoma; PD-L1=programmed cell death-ligand 1; RAS=rat sarcoma; RASi=RAS inhibitor; RAS(ON)i=RAS inhibitor to RAS proteins in ON state (revmed.com/science, Accessed July 22, 2026); SCLC=small cell lung cancer; incl.=including; vs.=versus; Ph=Phase. Reference: ClinicalTrials.gov Arcus: with HIF-2⍺ in ccRCC 24 Currently Enrolling Ivonescimab Publications2 Ivonescimab Collaborations >65 ISTs1 >50 Ivonescimab is an investigational therapy not presently approved by any regulatory authority other than China’s National Medical Products Administration (NMPA). Ivonescimab is an investigational therapy not presently approved by any regulatory authority other than China’s National Medical Products Administration (NMPA). EGFRm NSCLC post-TKI Ivonescimab + chemo vs. placebo + chemo BLA Submitted EnrollingEnrollingSQ: Enrollment Complete nSQ: Enrollment Complete 1L CRC Ivonescimab + chemo vs. bevacizumab + chemo 1L NSCLC: PD-L1 High Ivonescimab vs. pembrolizumab 1L NSCLC Ivonescimab + chemo vs. pembrolizumab + chemo 7 GORTEC: Ph III Study +/- CD47 in HNSCC Additional future collaborations with ADCs and other novel targets may be planned GSK: with Novel B7-H3 ADC in NSCLC, SCLC, CRC RevMed: with Novel RAS(ON) in NSCLC, PDAC, CRC Summit Proprietary Information - Do Not Copy or Distribute Q2 2026 Earnings Presentation | 7/2026

Goldman et al WCLC 2025 Abbreviations: 1L=first-line; chemo=chemotherapy; CI=confidence interval; EGFR+=epidermal growth factor receptor positive; HR=hazard ratio; NSCLC=non-small cell lung cancer; PD-1=programmed cell death protein 1; PD- L1=programmed cell death-ligand 1; TRAE=treatment-related adverse event. References: 1. Summit Press Release, Jul 22, 2026. Three NSCLC Settings: Four Phase III Studies with OS Results HR<0.80 V PD-1 (tislelizumab) + chemo (N=265) Ivonescimab + chemo (N=266) HARMONi-6 263 (99.2%)264 (99.2%)TRAEs 91 (34.3%)110 (41.4%)Serious TRAEs 12 (4.5%)14 (5.3%)TRAEs Leading to Discontinuation 11 (4.2%)10 (3.8%)TRAEs Leading to Death Placebo + chemo (N=218) Ivonescimab + chemo (N=218) HARMONi 203 (93.1%)207 (95.0%)TRAEs 33 (15.1%)61 (28.0%)Serious TRAEs 11 (5.0%)16 (7.3%)TRAEs Leading to Discontinuation 5 (2.3%)4 (1.8%)TRAEs Leading to Death Placebo + chemo (N=161) Ivonescimab + chemo (N=161) HARMONi-A 152 (94.4%)159 (98.8%)TRAEs 29 (18.0%)78 (32.3%)Serious TRAEs 10 (6.2%)18 (11.2%)TRAEs Leading to Discontinuation 1 (0.6%)0 (0%)TRAEs Leading to Death HR=0.78 (95% CI: 0.62-0.98, nominal p=0.0332) HR=0.66 (95% CI: 0.46-0.78, p<0.0017) HR=0.74 (95% CI: 0.58-0.95, p=0.019) Ivonescimab is an investigational therapy not presently approved by any regulatory authority other than China’s National Medical Products Administration (NMPA). HR=0.78 (no confidence intervals or p-value provided publicly) PD-1 (pembrolizumab) (N=199) Ivonescimab (N=197)HARMONi-2 32 (16.1%)41 (20.8%)Serious TRAEs 6 (3.0%)3 (1.5%)TRAEs Leading to Discontinuation 2 (1.0%)1 (0.5%)TRAEs Leading to Death Le et al SITC 2025 Zhiwei et al ASCO 2026 (1L, PD-L1+) Ivonescimab label, China Ivonescimab is an investigational therapy not presently approved by any regulatory authority other than China’s National Medical Products Administration (NMPA). Tislelizumab + Chemotherapy 8 (EGFR+, post-3rd Gen TKI) (1L, squamous)(EGFR+, post-TKI) Updated HR = 0.76 in updated OS analysis (DCO: June 2026). Additional details to be provided at upcoming medical conference.1 Summit Proprietary Information - Do Not Copy or Distribute Q2 2026 Earnings Presentation | 7/2026

9 The Next Exciting Steps for Summit & Ivonescimab 2H26 HARMONi-3 SQ: - Events reached for PFS analysis expected - Corresponding look at OS with PFS HARMONi: - Updated conference presentation (OS) - BLA PDUFA Date November 14, 2026 New Clinical Trials 1H27 HARMONi-3 SQ: - Events reached for interim OS analysis (independent of a PFS analysis) HARMONi-3 nSQ: - Events reached for PFS analysis expected New Clinical Trials Anti-VEGF Anti-PD-1 Abbreviations: BLA=Biologics License Application; nSQ=non-squamous; OS=overall survival; PDUFA= Prescription Drug User Fee Act; PFS=progression-free survival; SQ=squamous. Continued Acceleration of Clinical Development Ivonescimab is an investigational therapy not presently approved by any regulatory authority other than China’s National Medical Products Administration (NMPA).9 Summit Proprietary Information - Do Not Copy or Distribute Q2 2026 Earnings Presentation | 7/2026

2028 PD-(L)1 Addressable Market2 Approved Anti PD-(L)1 & Anti-VEGF Therapies Approved Anti PD-(L)1 Therapies Approved Anti-VEGF Therapies 50+ Approved Indications for PD-(L)1 & VEGF Therapies1 $90B+ 2028 VEGF Addressable Market2 $20B+ Where Summit is currently exploring globally 1. KEYTRUDA® USPI, OPDIVO® USPI, LIBTAYO® USPI, IMFINZI® USPI, BAVENCIO® USPI, JEMPERLI® USPI, TECENTRIQ® USPI, ZYNYZ® USPI, AVASTIN® USPI, CYRAMZA® USPI, LENVIMA® USPI, INLYTA® USPI, SUTENT® USPI. 2. IQVIA MIDAS Disease, Dec 2023; IQVIA Institute Apr 2024; TD Cowen and IQVIA estimates. Abbreviations: PD-1=programmed cell death protein 1; PD-L1=programmed cell death-ligand 1; VEGF=vascular endothelial growth factor 10 Ivonescimab Revenue Potential by 2033 $15B+ Summit Proprietary Information - Do Not Copy or Distribute Q2 2026 Earnings Presentation | 7/2026

Financial Summary Q2’26 vs. Q1’26 Ivonescimab is an investigational therapy not presently approved by any regulatory authority other than China’s National Medical Products Administration (NMPA). 12 Summit Proprietary Information - Do Not Copy or Distribute Q2 2026 Earnings Presentation | 7/2026 (1) Excludes stock-based compensation Refer to the next slides for reconciliations between Generally Accepted Accounting Principles (GAAP) and Non-GAAP financial measures. June 30, 2026 March 31, 2026 Total GAAP Operating Expenses $220.5 $195.2 Research and development 157.7 132.6 General and administrative 62.8 62.6 Non-GAAP Operating Expenses $151.8 $122.4 Non-GAAP Research and Development (1) 133.6 108.2 Non-GAAP General and Administrative (1) 18.2 14.2 GAAP Net Loss ($215.7) ($189.4) Non-GAAP Net Loss ($147.0) ($116.6) Three Months Ended (in millions)

Schedule Reconciling Selected Non-GAAP Financial Measures Note 1: Stock-based compensation is a non-cash charge and costs calculated for this expense can vary year-over-year depending on the stock price of awards on the date of grant as well as the timing of compensation award arrangements. Ivonescimab is an investigational therapy not presently approved by any regulatory authority other than China’s National Medical Products Administration (NMPA). 13 Summit Proprietary Information - Do Not Copy or Distribute Q2 2026 Earnings Presentation | 7/2026 June 30, 2026 March 31, 2026 Reconciliation of GAAP to Non-GAAP Research and Development Expense GAAP Research and development $157.7 $132.6 Stock-based compensation (Note 1) (24.1) (24.4) Non-GAAP Research and Development $133.6 $108.2 Reconciliation of GAAP to Non-GAAP General and Administrative Expenses GAAP General and administrative $62.8 $62.6 Stock-based compensation (Note 1) (44.6) (48.4) Non-GAAP General and Administrative $18.2 $14.2 Reconciliation of GAAP to Non-GAAP Operating Expenses GAAP Operating expenses $220.5 $195.2 Stock-based compensation (Note 1) (68.7) (72.8) Non-GAAP Operating Expense $151.8 $122.4 Three Months Ended (in millions)

Schedule Reconciling Selected Non-GAAP Financial Measures Note 1: Stock-based compensation is a non-cash charge and costs calculated for this expense can vary year-over-year depending on the stock price of awards on the date of grant as well as the timing of compensation award arrangements. Ivonescimab is an investigational therapy not presently approved by any regulatory authority other than China’s National Medical Products Administration (NMPA). 14 Summit Proprietary Information - Do Not Copy or Distribute Q2 2026 Earnings Presentation | 7/2026 June 30, 2026 March 31, 2026 Reconciliation of GAAP Net Loss to Non-GAAP Net Loss GAAP Net Loss ($215.7) ($189.4) Stock-based compensation (Note 1) 68.7 72.8 Non-GAAP Net Loss ($147.0) ($116.6) Reconciliation of GAAP EPS to Non-GAAP EPS GAAP Loss Per Share ($0.28) ($0.24) Stock-based compensation (Note 1) 0.09 0.09 Non-GAAP Loss Per Share ($0.19) ($0.15) Basic and Diluted Weighted Average Shares Outstanding 778.2 775.5 Three Months Ended (in millions)

Ivonescimab is an investigational therapy not presently approved by any regulatory authority other than China’s National Medical Products Administration (NMPA). Summit Proprietary Information - Do Not Copy or Distribute Q2 2026 Earnings Presentation | 7/202615 Bob Duggan Chairman & Co-Chief Executive Officer Dave Gancarz Chief Business & Strategy Officer Manmeet Soni Chief Operating Officer & Chief Financial Officer Dr. Maky Zanganeh President & Co-Chief Executive Officer Dr. Allen Yang Chief R&D Strategy Officer Dr. Fong Clow Chief Biometrics Officer Dr. Urte Gayko Chief Regulatory, Pharmacovigilance & Quality Officer Dr. Bilal Piperdi Chief Medical Officer