a20260223q4fy2025earning

Summit Therapeutics Q4 & FY 2025 Earnings Call February 23, 2026 4:30pm ET

Forward Looking Statement Any statements in this presentation about 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., 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, statements about the previously 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, 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. Ivonescimab is an investigational therapy not presently approved by any regulatory authority other than China’s National Medical Products Administration (NMPA). Summit Therapeutics and the Summit Therapeutics logo are trademarks of Summit Therapeutics Inc. Copyright 2026, Summit Therapeutics Inc. All Rights Reserved.2 Summit Proprietary Information - Do Not Copy or Distribute Q4 & YE 2025 Earnings Presentation | 2/2026

Ivonescimab is an investigational therapy not presently approved by any regulatory authority other than China’s National Medical Products Administration (NMPA). HARMONi-3 Clinical Trial Update ⚫ HARMONi-3: ◼ Phase III multi-regional clinical study in 1L NSCLC comparing ivonescimab + chemo vs. pembrolizumab + chemo ◼ For two separate cohorts, squamous and non-squamous histologies, statistical analyses for PFS and OS will be conducted separately (two separate ITT populations) ⚫ February 2026 HARMONi-3 Updates: ◼ HARMONi-3 squamous cohort: patient screening completed Q1 2026 ◼ Statistical plan amended to include interim PFS analysis of HARMONi-3 squamous cohort ◼ Note: OS is expected to be immature at time of this interim PFS analysis ⚫ Timing Expectations: ◼ Q2 2026: interim PFS analysis expected for HARMONi-3 squamous cohort ◼ H2 2026: final PFS & interim OS data for HARMONi-3 squamous cohort expected ◼ H2 2026: expected completion of enrollment for HARMONi-3 non-squamous cohort ◼ H1 2027: final PFS in HARMONi-3 non-squamous cohort Summit Sponsored Trial 3 Summit Proprietary Information Do Not Copy or Distribute Q4 & YE 2025 Earnings Presentation | 2/2026 Abbreviations: 1L=first-line; chemo=chemotherapy; vs.=versus; PFS=progression-free survival; OS=overall survival; ITT=intention-to-treat; Q[X]=quarter number of a fiscal year; H[X}=half number of a fiscal year;

Ivonescimab is an investigational therapy not presently approved by any regulatory authority other than China’s National Medical Products Administration (NMPA). Data generated and analyzed by Akeso. z 4 1 Q4 2025 & Current Highlights BLA Filed; PDUFA Nov 14, 2026 Enrollment progressing Squam. Interim PFS Q21 Squam. Final PFS, Int. OS H2 20261 Non-Squam. Final PFS H1 20271 Ivonescimab is an investigational therapy not presently approved by any regulatory authority other than China’s National Medical Products Administration (NMPA). Studies starting mid-2026 GSK: GORTEC: Groupe d'Oncologie Radiothérapie Tête Et Cou or Head and Neck Oncology and Radiotherapy Group; RevMed: Revolution Medicines PDUFA: Prescription Drug User Fee Act; OS: overall survival; PFS: progression-free survival; HR: hazard ratio; PD-1=programmed cell death protein 1; References: 1. Summit Therapeutics Press Release February 23, 2026; Studies conducted by Akeso are single-region studies conducted in China. Summit Collaborations: First patient dosed Q1 2026 RevMed: Enrollment initiated 2L+ EGFRm NSCLC ivonescimab + chemo stat sig OS vs. chemo OS HR 0.74 (p=0.19) 1L Squamous NSCLC ivonescimab + chemo stat sig PFS vs. PD-1 + chemo PFS HR 0.60 (p<0.0001) Phase III ILLUMINE study in HNSCC, expect FPI Q2 2026 GORTEC: Summit Proprietary Information - Do Not Copy or Distribute Q4 & YE 2025 Earnings Presentation | 2/2026

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 Q4 & YE 2025 Earnings Presentation | 2/20266 Abbreviations: 1L=first-line; 2L=second-line; AG=albumin-bound paclitaxel plus gemcitabine; BTC=biliary tract cancer; Chemo=chemotherapy; CPS=combined positive score; CRC=colorectal cancer; EGFRm+=epidermal growth factor receptor mutant positive; GEJ=gastroesophageal junction; 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; TIGIT=T cell immunoreceptor with Ig and ITIM domains; TNBC=triple negative breast cancer; vs.=versus. Reference: ClinicalTrials.gov These ivonescimab clinical trials are being conducted in China and/or Australia and are fully sponsored and managed by Akeso. TUMOR TYPE STUDY LINE & INDICATION REGIMEN STATUS Approved PHASE 1/1b 2 3 Lung 2L advanced EGFRm+ NSCLC ivonescimab + chemo vs. placebo + chemo Active, Recruiting Complete 1L metastatic NSCLC (all PD-L1 levels) ivonescimab vs. pembrolizumab Active, Recruiting Complete 1L advanced or metastatic NSCLC ivonescimab + chemo vs. tislelizumab + chemo Active, Recruiting Complete 2L advanced or metastatic NSCLC progressed on or after PD-L1 therapy ivonescimab + docetaxel vs. placebo + docetaxel Not Yet Recruiting Consolidation treatment SCLC not progressed after chemoradiation ivonescimab vs. placebo Recruiting AK112-208 1L advanced or metastatic NSCLC ivonescimab + cadonilimab ± chemo Recruiting Breast 1L inoperable locally advanced/ metastatic TNBC ivonescimab + nab-paclitaxel vs. placebo + nab-paclitaxel Recruiting AK117-203 1L metastatic TNBC ivonescimab + chemo Recruiting Gynecologic AK104-221 2L OC ivonescimab ± chemo ± cadonilimab Recruiting AK112-211 1L platinum-sensitive OC ivonescimab ± chemo ± olaparib Recruiting Head and Neck 1L recurrent or metastatic HNSCC with PD-L1 positive (CPS ≥1) ivonescimab + AK117 vs. placebo + pembrolizumab Recruiting Gastrointestinal 1L unresectable locally advanced or metastatic BTC ivonescimab + chemo vs. durvalumab + chemo Active, Recruiting Complete 1L metastatic PDAC ivonescimab + chemo ± AK117 vs. placebo + chemo Recruiting 1L metastatic CRC ivonescimab + chemo vs. bevacizumab + chemo Recruiting AK112-209 1L advanced HCC ivonescimab ± anti-TIGIT antibody ± cadonilimab ± anti-TIGIT/TGF-β vs. sintilimab + bevacizumab Recruiting AK112-210 1L metastatic PDAC ivonescimab ± cadonilimab ± AG vs. AG Recruiting AK119-202 1L or 2L microsatellite stable CRC ivonescimab + anti-CD73 mAb ± chemo Recruiting AK130-201 2L advanced BTC ivonescimab ± anti-TIGIT/TGF-β or ivonescimab Not yet recruiting Various Cancers AK117-202 1L or 2L advanced or metastatic NSCLC, GEJ, BTC, PDAC ivonescimab + ligufalimab ± chemo Active, Not Recruiting AK127-104 1L advanced malignant tumors ivonescimab + anti-TIGIT antibody Not yet recruiting Lung 2L advanced EGFRm+ NSCLC ivonescimab + chemo vs. placebo + chemo Active, Recruiting Complete 1L metastatic NSCLC ivonescimab + chemo vs. pembrolizumab + chemo Recruiting 1L metastatic PD-L1 high (≥50%) NSCLC ivonescimab vs. pembrolizumab Recruiting Gastrointestinal 1L metastatic CRC ivonescimab + chemo vs. bevacizumab + chemo Recruiting Ivonescimab Development: Summit + Akeso Pipelines Phase I and II trials completed by Akeso.

Ivonescimab 1L NSCLC Ivonescimab vs. Anti-PD-1 +/- chemo Presented at WCLC 2024 Presidential Symposium1 The Lancet2 Approved indication in China Awaiting data maturation for OS Squamous, PD-L1 All-Comers Ivonescimab + chemo vs. tislelizumab (PD-1) + chemo Presented at ESMO 2025 Presidential Symposium3 The Lancet4 sNDA pending in China Awaiting data maturation for OS EGFRm NSCLC Post-TKI Ivonescimab + Chemo vs. Placebo + Chemo EGFRm after a TKI Ivonescimab + chemo vs. placebo + chemo Presented at ASCO 20245 OS Update: SITC Nov. 20257 JAMA6 Approved indication in China EGFRm after a 3rd-gen TKI Ivonescimab + chemo vs. placebo + chemo Presented at WCLC 2025 Presidential Symposium8 US BLA submitted Q4 2025 Ivonescimab is an investigational therapy not presently approved by any regulatory authority other than China’s National Medical Products Administration (NMPA). 8 PD-L1 Positive, Monotherapy Ivonescimab vs. pembrolizumab References: 1. Wang C, et al. HARMONi-2. Presented at WCLC 2024.; 2. Xiong A, et al. Lancet. 2025;405(10481):839-849; 3. Lu S, et al. HARMONi-6. Presented at ESMO 2025.; 4. Chen Z, et al. Lancet. 2025;406(10515):2078-2088.; 5. Zhang L, et al. HARMONi-A study. Presented at ASCO 2024.; 6. Fang W, et al. JAMA. 2024;332(7):561-570.; 7. Zhang L, et al. Final OS Analysis: HARMONi-A. Presented at SITC 2025.; 8. Goldman J, et al. HARMONi. Presented at WCLC 2025. Abbreviations: 1L=first-line; 2L=second-line; ASCO=American Society of Clinical Oncology; chemo=chemotherapy; EGFRm=epidermal growth factor receptor mutation; ESMO=European Society for Medical Oncology; gen=generation; JAMA=The Journal of the American Medical Association; NSCLC=non-small cell lung cancer; OS=overall survival; PD-1=programmed cell death protein 1; PD-L1=programmed cell death-ligand 1; SITC=The Society for Immunotherapy of Cancer; sNDA=Supplemental New Drug Application (for marketing authorization); TKI=tyrosine kinase inhibitor; VEGF=vascular endothelial growth factor; vs.=versus; WCLC=World Conference on Lung Cancer. Four Phase III Clinical Studies with Positive Results Summit Proprietary Information - Do Not Copy or Distribute Q4 & YE 2025 Earnings Presentation | 2/2026

Financial Summary Q4’25 vs. Q3’25 (1) Excludes stock-based compensation December 31, 2025 September 30, 2025 Total GAAP Operating Expenses $ 225.0 $ 234.2 Research and development 147.3 131.1 General and administrative 77.7 103.1 Non-GAAP Operating Expenses $ 113.3 $ 103.4 Non-GAAP Research and Development (1) 102.0 90.5 Non-GAAP General and Administrative (1) 11.3 12.9 GAAP Net Loss $ (219.2) $ (231.8) Non-GAAP Net Loss $ (107.5) $ (101.0) 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). 12 Summit Proprietary Information - Do Not Copy or Distribute Q4 & YE 2025 Earnings Presentation | 2/2026 (1) Excludes stock-based compensation Refer to the next slides for reconciliations between Generally Accepted Accounting Principles (GAAP) and Non-GAAP financial measures.

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. December 31, 2025 September 30, 2025 Reconciliation of GAAP to Non-GAAP Research and Development Expense GAAP Research and development $ 147.3 $ 131.1 Stock-based compensation (Note 1) (45.3) (40.6) Non-GAAP Research and Development $ 102.0 $ 90.5 Reconciliation of GAAP to Non-GAAP General and Administrative Expenses GAAP General and administrative $ 77.7 $ 103.1 Stock-based compensation (Note 1) (66.4) (90.2) Non-GAAP General and Administrative $ 11.3 $ 12.9 Reconciliation of GAAP to Non-GAAP Operating Expenses GAAP Operating expenses $ 225.0 $ 234.2 Stock-based compensation (Note 1) (111.7) (130.8) Non-GAAP Operating Expense $ 113.3 $ 103.4 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). 13 Summit Proprietary Information - Do Not Copy or Distribute Q4 & YE 2025 Earnings Presentation | 2/2026

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. December 31, 2025 September 30, 2025 Reconciliation of GAAP Net Loss to Non-GAAP Net Loss GAAP Net Loss $ (219.2) $ (231.8) Stock-based compensation (Note 1) 111.7 130.8 Non-GAAP Net Loss $ (107.5) $ (101.0) Reconciliation of GAAP EPS to Non-GAAP EPS GAAP Loss Per Share $ (0.29) $ (0.31) Stock-based compensation (Note 1) 0.15 0.18 Non-GAAP Loss Per Share $ (0.14) $ (0.13) Basic and Diluted Weighted Average Shares Outstanding 766.4 743.4 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). 14 Summit Proprietary Information - Do Not Copy or Distribute Q4 & YE 2025 Earnings Presentation | 2/2026