Summit Therapeutics Inc.

1. Organization

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 a Collaboration and License Agreement (the “License Agreement”) with Akeso, Inc. and its affiliates (collectively, “Akeso”) pursuant to which the Company has in-licensed intellectual property related to ivonescimab, as further described in Note 4. 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 an amendment to the License Agreement (the “Second Amendment”) with Akeso to expand its territories covered under the License Agreement to also include the Latin America, Middle East and Africa regions (collectively, and as expanded, the “Licensed Territory”). The Company’s operations are focused on the development of ivonescimab and other future activities, as the Company determines.

Basis of Presentation

The accompanying unaudited condensed consolidated financial statements have been prepared in accordance with accounting principles generally accepted in the United States (“U.S. GAAP”) and pursuant to the rules and regulations of the SEC. Accordingly, certain information and disclosures required by U.S. GAAP for complete consolidated financial statements are not included herein. All intercompany accounts and transactions have been eliminated in consolidation. The interim financial data as of September 30, 2025 and for the three and nine months ended September 30, 2025 are unaudited; however, in the opinion of management, the interim data includes all adjustments, consisting of normal recurring adjustments, necessary for a fair statement of the results for the interim periods. The condensed consolidated balance sheet presented as of December 31, 2024 has been derived from the consolidated audited financial statements as of that date. The results of the period are not necessarily indicative of full year results or any other interim period. These unaudited interim condensed consolidated financial statements should be read in conjunction with the audited financial statements and notes thereto of the Company which are included in the Company’s Annual Report. The financial results of the Company’s activities are reported in United States Dollars.

Certain reclassifications have been made to the prior years’ financial statements to conform to current year presentation.

Use of Estimates

The preparation of these unaudited condensed consolidated financial statements requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities at the date of the unaudited condensed consolidated financial statements and the reported amounts of incomes and expenses during the reporting period. On an on-going basis, management evaluates its estimates and judgments, including those related to accrued research and development expenses, stock-based compensation, other long-lived assets and income taxes. Management bases its estimates and judgments on historical experience and on various other factors that are believed 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.

Liquidity and Capital Resources

During the three and nine months ended September 30, 2025, the Company incurred a net loss of $231,793 and $860,414, respectively, and cash used in operating activities for the nine months ended September 30, 2025 was $220,992. As of September 30, 2025, the Company had an accumulated deficit of $2,074,987 and cash and cash equivalents of $238,554. The Company expects to continue to generate operating losses for the foreseeable future.

The Company’s cash and cash equivalents are not sufficient to fund the Company’s planned operations for a period of at least one year from the date these unaudited condensed consolidated financial statements are issued.

Until the Company can generate substantial revenue and achieve profitability, the Company will need to raise additional capital to fund its ongoing operations and capital needs. The Company continues to evaluate options to further finance its operating cash needs for its 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 management of the Company will be able to obtain financing on terms acceptable to the Company. If the Company is unable to obtain funding when required in the future, the Company could be required to delay or reduce research and development programs, product portfolio expansion, or future commercialization efforts, which could adversely affect its business prospects. These conditions raise substantial doubt about the Company’s ability to continue as a going concern.

The accompanying unaudited condensed consolidated financial statements have been prepared assuming the Company will continue as a going concern, which contemplates the realization of assets and satisfaction of liabilities in the normal course of the business. The unaudited condensed consolidated financial statements do not include any adjustments relating to the recoverability and classification of recorded asset amounts or the amounts and classifications of liabilities that might result from the outcome of this uncertainty.

2. Summary of Significant Accounting Policies and Recent Accounting Pronouncements

Significant Accounting Policies

There have been no significant changes to the Company’s significant accounting policies used in the preparation of these unaudited condensed consolidated financial statements for the nine months ended September 30, 2025 as compared with those discussed in Note 4 to the consolidated financial statements in the Company's Annual Report.

Recently Issued Accounting Pronouncements

In December 2023, the Financial Accounting Standards Board (“FASB”) issued Accounting Standards Update “ASU” No. 2023-09, “Improvements to Income Tax Disclosures”, which requires disclosure of disaggregated income taxes paid, prescribes standard categories for the components of the effective tax rate reconciliation, and modifies other income tax-related disclosures. ASU No. 2023-09 is effective for fiscal years beginning after December 15, 2024 and allows for adoption on a prospective basis, with a retrospective option. Early adoption is permitted. The Company adopted ASU 2023-09 on January 1, 2025. The adoption of ASU-2023-09 did not have a material impact on the Company’s unaudited condensed consolidated financial statements.

In November 2024, the FASB issued ASU 2024-03, Disaggregation of Income Statement Expenses (“ASU 2024-03”) which requires disclosures about specific types of expenses included in the expense captions presented on the face of the income statement as well as disclosures. The guidance is to be applied prospectively, with the option for retrospective application and is effective for public business entities for fiscal years beginning after December 15, 2026, and interim periods beginning after December 15, 2027. Early adoption is permitted. The Company is currently evaluating the impact of the adoption of this standard on the Company’s consolidated financial statements and related disclosures.

In July 2025, the One Big Beautiful Bill Act (“OBBBA”) was enacted in the U.S. The OBBBA includes significant provisions, such as the permanent extension of certain expiring provisions of the Tax Cuts and Jobs Act, modifications to the international tax framework and the restoration of favorable tax treatment for certain business provisions. The legislation has multiple effective dates, with certain provisions effective in 2025 and others implemented through 2027. The Company is currently evaluating the impact of the OBBBA on the Company’s consolidated financial statements and related disclosures.

Other recent authoritative guidance issued by the FASB (including technical corrections to the FASB ASC), the American Institute of Certified Public Accountants, and the SEC did not or are not expected to have a material impact on the Company’s consolidated financial statements and related disclosures.

3. Segment Reporting

The Company’s chief operating decision makers (the “CODM function”), which are the Company’s Co-Chief Executive Officers, Mr. Duggan and Dr. Zanganeh, and Chief Operating Officer and Chief Financial Officer, Mr. Soni, utilize consolidated net loss that is reported on the unaudited condensed consolidated statement of operations and comprehensive loss to make decisions about allocating resources and assessing performance for the entire Company. The CODM function approves key operating and strategic decisions, including key decisions in clinical development and clinical operating activities, entering into significant contracts, such as revenue contracts and collaboration agreements and approves the Company’s consolidated operating budget. The CODM function views the Company's operations and manages its business on a consolidated basis and as a single reportable operating segment. The CODM function is regularly provided with the following significant segment expenses:

(1) Other expenses include general and administrative expenses excluding compensation and stock-based compensation.

As of September 30, 2025 and December 31, 2024, substantially all of the Company’s long-lived assets are located in the United States.

4. Akeso License and Collaboration Agreement

On December 5, 2022, the Company entered into the License Agreement with Akeso pursuant to which the Company is in-licensing its breakthrough bispecific antibody, ivonescimab. The License Agreement and transaction closed in January 2023 following customary waiting periods.

Ivonescimab, known as AK112 in China and Australia, and also as SMT112 in the United States, Canada, Europe, and Japan, is a novel, potential first-in-class bispecific antibody intending to combine the effect of immunotherapy via a blockade of PD-1 with the anti-angiogenesis effects of an anti-VEGF into a single molecule. Ivonescimab was engineered to bring two well established oncology targeted mechanisms together. Ivonescimab is currently in clinical development and, pursuant to the terms of the License Agreement, Summit will design and conduct the clinical trial activities to support regulatory filings in the Licensed Territory that Summit will submit.

Pursuant to the terms of the License Agreement, Summit will have final decision-making authority with respect to clinical development strategy and execution in the Licensed Territory. For co-joined studies in which both Summit and Akeso participate, mutual agreement is required for material decisions; Summit retains the exclusive decision making with respect to participating in, and continuing its participation in, co-joined studies. Pursuant to the terms of the License Agreement, Summit will have final decision-making authority with respect to commercial strategy, pricing and reimbursement and other commercialization matters 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. Summit is not assuming any liabilities (including contingent liabilities), acquiring any physical assets or trade names, or hiring or acquiring any employees from Akeso in connection with 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.

In exchange for the rights obtained, the Company made an upfront payment of $500,000 to Akeso, of which $274,900 was paid in cash and, pursuant to the License Agreement and Issuance Agreement, Akeso elected to receive 10,000,000 shares of the Company’s common stock, par value $0.01 per share (“common stock”) in lieu of $25,100 in cash. The remaining $200,000 amount of the upfront payment was paid on March 6, 2023.

Effective June 3, 2024, the Company and Akeso entered into the Second Amendment to the License Agreement to expand the Company’s territories covered under the License Agreement to include the Latin America, Middle East and Africa regions. Pursuant to the Second Amendment, the Company paid an upfront payment to Akeso of $15,000 in the third quarter of 2024. Akeso will also be eligible to receive up to an additional $55,000 upon the achievement of certain commercial milestones. Except as specifically modified by the Second Amendment, the terms and conditions of the License Agreement remain in full force and effect.

The Company has accounted for the License Agreement and Second Amendment to acquire therights to develop and commercialize ivonescimab as the acquisition of an asset. All of the consideration relates to ivonescimab and technological feasibility of the asset has not yet been established since ivonescimab is in clinical development. As such, the Company has expensed the consideration as acquired in-process research and development upon closing of the transaction in the unaudited condensed consolidated statement of operations and comprehensive loss. Acquired in-process research and development expense for the three and nine months ended September 30, 2025 wasnil. Acquired in-process research and development expense for the three and nine months ended September 30, 2024 wasnil and $15,007, respectively, which is comprised of the upfront payment of $15,000 andimmaterial transaction costs.

In addition to the payments already made to Akeso, under the License Agreement and Second Amendment, there are additional potential milestone payments of up to $4,555,000, as Akeso will be eligible to receive regulatory milestones of up to $1,050,000 and commercial milestones of up to $3,505,000. In addition, Akeso will be eligible to receive low double-digit royalties on net sales.

5. Other Income, net

The following table sets forth the components of other income:

(1)Investment income relates to the Company’s money market funds and short-term investments in U.S. treasury securities. Refer to Note 7 for details.

6. Net Loss per Share

The following table sets forth the computation of basic and diluted net loss per share:

Basic net loss per share is computed by dividing the net loss by the weighted-average number of common shares outstanding for the period. Diluted net loss per share is computed by dividing the diluted net loss by the weighted-average number of common shares outstanding for the period, including potentially dilutive common shares. Since the Company was in a loss position for all periods presented, basic net loss per share is the same as diluted net loss per share for all periods, as the inclusion of all potential common share equivalents outstanding would have been anti-dilutive.

The following potentially dilutive securities were excluded from the computation of the diluted net loss per share of common stock for the periods presented because their effect would have been anti-dilutive:

Stock options that are outstanding and contain improbable vesting criteria are excluded from the presentation of common stock equivalents outstanding in the table above.

7. Fair Value Measurements and Short-Term Investments

In accordance with the provisions of fair value accounting, a fair value measurement assumes that the transaction to sell an asset or transfer a liability occurs in the principal market for the asset or liability or, in the absence of a principal market, the most advantageous market for the asset or liability and defines fair value based on the exit price model.

The fair value measurement guidance establishes a fair value hierarchy, which requires an entity to maximize the use of observable inputs and minimize the use of unobservable inputs when measuring fair value. The guidance describes three levels of inputs that may be used to measure fair value:

Level 1

Quoted prices in active markets for identical assets or liabilities as of the reporting date. Active markets are those in which transactions for the asset or liability occur in sufficient frequency and volume to provide pricing information on an ongoing basis.

Level 2

Observable inputs other than Level 1 prices, such as quoted prices for similar assets or liabilities; quoted prices in markets that are not active; or other inputs that are observable or can be corroborated by observable market data for substantially the full term of the assets or liabilities. Level 2 assets and liabilities include debt securities with quoted prices that are traded less frequently than exchange-traded instruments or securities or derivative contracts that are valued using a pricing model with inputs that are observable in the market or can be derived principally from or corroborated by observable market data.

Level 3

Unobservable inputs that are supported by little or no market activity and that are significant to the fair value of the assets or liabilities. Level 3 assets and liabilities include financial instruments whose value is determined using pricing models, discounted cash flow methodologies, or similar techniques, as well as instruments for which the determination of fair value requires significant management judgment or estimation.

In certain cases, the inputs used to measure fair value may fall into different levels of the fair value hierarchy. In such cases, the Company categorizes such assets and liabilities based on the lowest level input that is significant to the fair value measurement in its entirety. The Company’s assessment of the significance of a particular input to the fair value measurement in its entirety requires judgment and considers factors specific to the asset.

The following tables sets forth the Company’s fair value hierarchy for its assets and liabilities that are measured at fair value on a recurring basis as of September 30, 2025 and December 31, 2024:

The tables above do not include cash at September 30, 2025 and December 31, 2024 of $4,870 and $16,263, respectively.

The Company believes that the carrying amounts of prepaid expenses, other current assets, accounts payable, and accrued expenses approximates their fair values due to the short-term nature of those instruments.

Realized gains on short-term investments for the three and nine months ended September 30, 2025 and 2024 were immaterial, respectively.

8. Research and Development Prepaid Expenses and Accrued Liabilities

Included within prepaid expenses and other current assets at September 30, 2025 and December 31, 2024 is $5,204 and $8,338, respectively, of prepayments relating to research and development expenditures. Included within accrued liabilities at September 30, 2025 and December 31, 2024 is $24,590 and $17,441, respectively, relating to research and development expenditures.

These amounts are determined based on the estimated costs to complete each study or activity related to the ongoing clinical trials for ivonescimab, the estimation of the current stage of completion and the invoices received, as well as predetermined milestones which are not reflective of the current stage of development for prepaid expenses. However, accrued liabilities increase as the activities progress. The key sensitivity is the estimated current stage of completion of each study or activity, which is based on information received from the supplier and the Company’s operational knowledge of the work completed under those contracts.

9. Promissory Note Payable to Related Parties

December 2022 Promissory Notes

On December 6, 2022, the Company entered into a Note Purchase Agreement (the “Note Purchase Agreement”), with Mr. Duggan and Dr. Zanganeh, pursuant to which the Company agreed to sell to each of Mr. Duggan and Dr. Zanganeh unsecured promissory notes in the aggregate amount of $520,000. Pursuant to the Note Purchase Agreement, the Company issued to Mr. Duggan and Dr. Zanganeh unsecured promissory notes in the amount of $400,000 (the “Duggan February Note”) and $20,000 (the “Zanganeh Note”), respectively, which matured and became due on February 15, 2023 and an unsecured promissory note to Mr. Duggan in the amount of $100,000 (the “Duggan September Note” and together with the Duggan February Note and the Zanganeh Note, the “December 2022 Notes”), which was originally due on September 15, 2023. The maturity dates of the December 2022 Notes could have been extended one or more times at the Company’s election, but in no event to a date later than September 6, 2024. In addition, if the Company consummated a public offering, then upon the later to occur of (i)five business days after the Company receives the net cash proceeds therefrom or (ii) May 15, 2023, the Duggan February Note and the Zanganeh Note were to be prepaid by an amount equal to the lesser of (a)100% of the amount of the net proceeds of such offering and (b) the outstanding principal amount on such Notes.

On January 19, 2023, the Company provided notice to extend the term of the Duggan February Note and Duggan September Note to a maturity date of September 6, 2024. Furthermore, on January 19, 2023, the Company and Mr. Duggan rectified the Duggan February Note and Duggan September Note in order to correctly reflect the parties’ intent that the Company may only prepay (i) the Duggan February Note following the completion of a public rights offering to be conducted by Summit in the approximate amount of $500,000, or a similar capital raise, in an amount equal to the lesser of (x) the net proceeds of the rights offering or such capital raise or (y) the full amount outstanding of the Duggan February Note, and (ii) Duggan September Note following the completion of a capital raising transaction subsequent to the rights offering in an amount equal to the lesser of (A) the net proceeds of such capital raise or (B) the full amount outstanding of the Duggan September Note. Following the issuance of thetwo new Promissory Notes (the “Revised Duggan February Note” and the “Revised Duggan September Note”, respectively), the Duggan February Note and Duggan September Note were marked as “cancelled” on their face and replaced in their entirety by the Revised Duggan February Note and the Revised Duggan September Note (together with the Zanganeh Note, the “Notes”).

On February 15, 2023, the $20,000 Zanganeh Note matured and the Company repaid the outstanding principal balance. In connection with the closing of the rights offering in 2023 (the “2023 Rights Offering”), the $400,000 Revised Duggan February Note matured and became due, and the Company repaid all principal and accrued interest thereunder using a combination of a portion of the cash proceeds from the 2023 Rights Offering and the extinguishment of a portion of the amount due equal to the subscription price of shares subscribed by Mr. Duggan in the 2023 Rights Offering.

The Notes accrued interest at an initial rate of 7.5%. All interest on the Notes was paid on the date of signing for the period through February 15, 2023. Such prepaid interest was paid in a number of shares of the Company’s common stock equal to the dollar amount of such prepaid interest, divided by $0.7913 (the consolidated closing bid price immediately preceding the time the Company entered into the Note Purchase Agreement, plus $0.01), which was 9,720,291 shares. For all applicable periods following February 15, 2023, interest accrued on the outstanding principal balance of the Notes at the U.S. prime interest rate, as reported in the Wall Street Journal, plus 50 basis points, as adjusted monthly, for three months immediately following February 15, 2023, and thereafter at the U.S. prime rate plus 300 basis points, as adjusted monthly. Accrued interest was paid in cash, quarterly in arrears, on each of March 31, June 30, September 30 and December 31. Debt issuance costs associated with the Notes were $44 and were capitalized as part of the carrying value of the promissory notes payable to related parties.

On February 17, 2024, the Revised Duggan February Note was amended to extend the maturity date from September 6, 2024 to April 1, 2025. For all applicable periods commencing February 17, 2024, interest accrued on the outstanding principal balance at the greater of 12% or the U.S. prime interest rate, as reported in the Wall Street Journal plus 350 basis points, as adjusted monthly, and compounded quarterly. Interest was paid upon maturity of the loan. The debt discount was amortized to interest expense using an effective interest rate method. The effective interest rate of the Revised Duggan February Note and Zanganeh Note was 8.9% and the effective interest rate of the Revised Duggan September Note was 11.3%.

On September 16, 2024, the Company used some of the proceeds raised from the September 2024 Private Placement (see Note 10 for further details) to repay $75,500 in principal on the Revised Duggan September Note. On October 1, 2024, the Company repaid the remaining outstanding balance of the Revised Duggan September Note in full, resulting in principal payments of $24,500 and accrued cash interest of $7,305.

As of September 30, 2025 and December 31, 2024, the Company hadno debt. During the three and nine months ended September 30, 2025, the Company incurredno interest expense. During the three and nine months ended September 30, 2024, the Company incurred interest expense of $2,455 and $8,677, respectively, related to the Revised Duggan September Note.

10. Stockholders' Equity

Preferred Stock

As of September 30, 2025 and December 31, 2024, the Company had 20,000,000 shares of preferred stock, par value $0.01, authorized andno shares issued and outstanding.

Common Stock

As of September 30, 2025 and December 31, 2024, the Company had authorized 1,000,000,000 shares of common stock.

June 2024 Private Investment in Public Equity (PIPE)

On June 3, 2024, the Company entered into a securities purchase agreement (the “Purchase Agreement”) with 667, L.P. and Baker Brothers Life Sciences, L.P., affiliates of Baker Bros. Advisors, L.P. (the “Investors”), whereby the Company sold 22,222,222 shares of common stock, at a purchase price of $9.00 per share, for an aggregate purchase price of approximately $200,000 in a private placement.

In connection with the Purchase Agreement, the Company entered into a Registration Rights Agreement with the Investors (the “Registration Rights Agreement”). The Registration Rights Agreement provides, among other things, that the Company will as soon as reasonably practicable, file with the SEC a registration statement registering the resale of the Shares. The Company agreed to use its reasonable best efforts to have such registration statement declared effective as soon as practicable after the filing thereof. The Company filed the registration statement on August 6, 2024, which was automatically effective upon filing.

September 2024 PIPE

On September 11, 2024, the Company entered into securities purchase agreements (the “September 2024 Purchase Agreements”) with multiple leading biotech institutional investors and individual accredited investors (the “September 2024 Private Placement”). In connection with the September 2024 Private Placement, the Company sold an aggregate of 10,352,418 shares of common stock, at purchase price of $22.70 per share (the closing price on September 11, 2024), for aggregate gross proceeds to the Company of approximately $235,000, with offering costs of $140.

All of the Company's Section 16 officers participated in the capital raise. A total of $79,000 was raised by the Company's Co-Chief Executive Officer (“CEO”), Chairman of the Board and majority stockholder, its Co-CEO and the President and member of the Company’s Board of Directors (the “Board”), its Chief Operating Officer (“COO”), Chief Financial Officer (“CFO”), and member of the Board, its Chief Accounting Officer (“CAO”), and a member of the Board of Directors, who invested via a controlled entity. The remaining $156,000 was raised with multiple leading biotech institutional investors. Refer to Note 12 Related Party Transactions for further details regarding related parties' participation.

On September 11, 2024, in connection with the September 2024 Purchase Agreements, the Company entered into Registration Rights Agreements with the Investors (the “September 2024 Registration Rights Agreements”). The September 2024 Registration Rights Agreements provide, among other things, that the Company will as soon as reasonably practicable file with the SEC a registration statement registering the resale of the Shares. The Company filed the registration statement on September 19, 2024, which was automatically effective upon filing.

At-the-Market Offering (ATM Offering)

On May 13, 2024, the Company entered into an at-the-market (“ATM”) sales agreement (the “Original Distribution Agreement”) pursuant to which the Company may, subject to the terms and conditions set forth in the agreement offer and sell, from time to time, through or to the agents, acting as agents or principal, shares of common stock, having an aggregate offering price of up to $90,000. On August 11, 2025, the Company entered into an amendment to the Original Distribution Agreement (as amended, the “Distribution Agreement”), which among other things, increased the aggregate offering price of common stock that the Company may offer and sell from time to time through the sales agent under the Distribution Agreement by an additional $360,000.

As of September 30, 2025, the Company sold 3,129,886 shares of common stock under the Distribution Agreement at a weighted-average price of $24.53 per share, for gross proceeds of $76,781. The Company received net proceeds of $74,796, which was net of commissions and other offering costs of approximately $1,985. The remaining gross proceeds available under the Distribution Agreement as of September 30, 2025 was approximately $373,219. The Company plans to use the net proceeds from this offering for working capital and general corporate purposes.

Warrants

As of September 30, 2025 the Company hadno outstanding warrants. As of December 31, 2024, the Company had outstanding and exercisable warrants of 4,629,988 with a weighted average exercise price of $1.58. During the nine months ended September 30, 2025,4,629,988 warrants were exercised with a weighted average exercise price of $1.58. During the three months ended September 30, 2025, no warrants were exercised.

11. Stock-Based Compensation

The Company currently grants stock options to employees and directors under the 2020 Stock Incentive Plan (the “2020 Plan”) and formerly, the Company granted stock options under the 2016 Long Term Incentive Plan. The 2020 Plan is administered by the Compensation Committee of the Company’s Board of Directors. The 2020 Plan is intended to attract and retain employees and directors and provide an incentive for these individuals to assist the Company to achieve long-range performance goals and to enable these individuals to participate in the long-term growth of the Company.

Based on the provisions of the 2020 Plan, the number of shares of common stock available for issuance under the 2020 Plan increased by 6,400,000 shares on January 1, 2025. On September 18, 2025, the Board approved an increase of 8,000,000 shares of common stock available for issuance under the 2020 Plan (the “Incremental Pool”), subject to the approval of the holders of a majority of the shares voting at the Company’s stockholder meeting. As of September 30, 2025, the Company granted 3,400,000 time-based stock options under the Incremental Pool, included in the table below. The Company’s unaudited condensed consolidated financial statements have treated the grant date of such stock options as the date Board approval was obtained.

On May 3, 2024, the Board adopted the 2024 Inducement Pool (the “Inducement Pool”), which mirrors the terms of the 2020 Plan, with a total of 2,000,000 shares of common stock reserved for issuance under the Inducement Pool. Effective January 22, 2025, the number of shares of common stock available under the Inducement Pool increased by 2,000,000 shares.

The following table summarizes the Company’s stock option activity for the nine months ended September 30, 2025.

• The stock option activity in the table above includes performance-based options outstanding as of December 31, 2024 of

48,220,320 of which 39,013,976 options were unvested and converted to time-based vesting. During the three months ended March 31, 2025, the company granted 5,475,000 performance-based options which were modified to time-based vesting during the three months ended June 30, 2025.

During the second quarter of 2025, the Compensation Committee of the Board of Directors approved a modification to the Company's outstanding unvested performance-based stock option awards for certain employees and executives that will require only the service-based vesting requirements to continue to be satisfied in order to become fully vested, subject to employee consent. The Company accounted for this change as a Type III modification (improbable-to-probable) in accordance with the requirements of Accounting Standards Codification Topic 718 (ASC 718). As a result,44,488,976 options were valued on the modification date. The Company will recognize the newly assessed measurement date fair value of the awards as compensation expense over the remaining vesting period. During the three and nine months ended September 30, 2025, the Company recognized expense of $111,446 and $578,088 associated with the modification, respectively. As of September 30, 2025, the unrecognized compensation cost associated with the modification was $273,391 and is expected to be expensed over a weighted-average recognition period of approximately 1.6 years.

The total stock-based compensation expense included in the Company’s unaudited condensed consolidated statements of operations and comprehensive loss was as follows:

The following summarizes stock-based compensation expense associated with each of the Company’s stock-based compensation arrangements:

12. Related Party Transactions

Leases

July 25, 2022 First Amendment to Sublease Agreement with Maky Zanganeh and Associates, Inc.

On July 25, 2022 the Company entered into a first amendment, dated July 19, 2022, to its existing sublease agreement with Maky Zanganeh and Associates, Inc. (“MZA”), an entity owned by Maky Zanganeh, consisting of 4,500 square feet of office space at 2882 Sand Hill Road, Menlo Park, California. The existing sublease term, which was set to expire on September 30, 2022, was extended for a period ofthirty-nine months from October 1, 2022 through December 31, 2025. The rent payable under the terms of the sublease is equivalent to the proportionate share of the net payable by MZA to the third-party landlord, based on the square footage of office space sublet by the Company, and no mark-up has been applied. The agreement was further amended to include additional space, as noted below under the August 2, 2024 Third Amendment to Sublease Agreement with Maky Zanganeh and Associates, Inc. During the three and nine months ended September 30, 2025, payments of $207 and $621, respectively, were made pursuant to the first and third amendments to the Sublease Agreement. During the three and nine months ended September 30, 2024, payments of $199 and $588, respectively, were made pursuant to the first amendment to the Sublease Agreement.

July 29, 2022 Second Amendment to Sublease Agreement with Maky Zanganeh and Associates, Inc.

On July 29, 2022, the Company entered into a second amendment to its existing sublease agreement with MZA, described above. The second amendment was effective as of August 1, 2022 and expires on December 31, 2025. The second amendment includes an additional 1,277 square feet of office space at 2882 Sand Hill Road, Menlo Park, California. The rent payable under the terms of the sublease is equivalent to the proportionate share of the net payable by MZA to the third-party landlord, based on the square footage of office space sublet by the Company, and no mark-up has been applied. During the three and nine months ended September 30, 2025, payments of $59 and $173, were made pursuant to the second amendment to the Sublease Agreement. During the three and nine months ended September 30, 2024, payments of $57 and $167, were made pursuant to the second amendment to the Sublease Agreement.

April 1, 2024 Miami Sublease Agreements

On April 1, 2024, the Company entered intotwo sublease agreements of its Miami headquarters location, one with Genius 24C Inc. (“Genius”), an affiliate of the Company’s Co-CEO, Robert W. Duggan (the “Genius Sublease Agreement”) andone with Duggan Investments Research LLC (“Investments Research”), also an affiliate of the Company's Co-CEO, Robert W. Duggan (the “Investments Research Sublease Agreement”). Pursuant to the Genius Sublease Agreement, Genius sublet from the Company 848 square feet of office space in the Miami HQ for asixty-two month term for total rental payments of approximately $446. Pursuant to the Investments Research Sublease Agreement, Investments Research sublet from the Company 848 square feet of office space in the Miami HQ for asixty-two month term for total rental payments of approximately $446. For the three and nine months ended September 30, 2025, the Company recognized sublease income of $46 and $140, respectively, which was recorded net of operating lease expenses. For the three and nine months ended September 30, 2024, the Company recognized $57 and $105, respectively, of sublease income recorded net of operating lease expenses, and recorded $90 in other receivables on the unaudited condensed consolidated balance sheet as of September 30, 2024.

August 2, 2024 Third Amendment to Sublease Agreement with Maky Zanganeh and Associates, Inc.

On August 2, 2024, the Company entered into a third amendment to its existing sublease agreement with MZA. The third amendment was effective August 1, 2024 and included an additional space of 145 square feet of office space located at 2882 Sand Hill Road, Menlo Park, California. The Company continues to be obligated to pay its proportionate share of the net payable by MZA to the third-party landlord, which is revised to 93.6% as of the effective date, based on the square footage of office space sublet by the landlord.

Promissory Note Payable to Related Parties

Refer to Note 9 for disclosure of the promissory note payable to related parties issued December 6, 2022 and fully repaid as of October 1, 2024.

Akeso Agreements

Upon the closing of the License Agreement, the Board appointed Dr. Yu (Michelle) Xia to serve as a member of the Board pursuant to the terms of the License Agreement. Dr. Xia is the founder of Akeso, and has been the chairwoman, president and CEO of Akeso since its inception in 2012. Furthermore, in connection with the License Agreement, the Company also entered into a Supply Agreement with Akeso, pursuant to which Summit agreed to purchase a certain portion of drug substance for clinical and commercial supply (the “Supply Agreement”). Refer to Note 4 for details on the License Agreement and Second Amendment. In addition to the License and Second Amendment and supply agreements, the Company also entered into various clinical services agreements with Akeso. During the three and nine months ended September 30, 2025, the Company paid $9,885 and $28,628 to Akeso. For the three and nine months ended September 30, 2024, the Company paid $18,551 and $28,674 to Akeso. As of September 30, 2025 and December 31, 2024, the Company included in accrued expenses, related to Akeso, $1,278 and $3,956, respectively.

Private Placements

September 2024 PIPE

On September 11, 2024, the Company’s Section 16 officers participated in the “September 2024 Purchase Agreements” along with multiple leading biotech institutional investors, whereby the Company sold an aggregate of 10,352,418 shares of common stock, at a price per share of $22.70, which was the closing price of common stock on September 11, 2024, for an aggregate gross proceeds to the Company of approximately $235,000.

The Company’s Co-CEO and Chairman of the Board, Mr. Robert W. Duggan, purchased 3,325,991 shares for an aggregate purchase price of $75,500; Co-CEO, President and member of its Board, Dr. Mahkam Zanganeh, purchased 44,052 shares for an aggregate purchase price of $1,000; COO and CFO, Manmeet S. Soni, purchased 44,052 shares for an aggregate purchase price of $1,000, and member of the Board, Jeff Huber, through his controlled entity, Caspian Capital LLC, purchased 44,052 shares for an aggregate purchase price of $1,000. The Company sold a total of 3,458,147 shares of its common stock to the aforementioned Section 16 officers for an aggregate purchase price of $78,500.

The Company used some of the proceeds raised from the September 2024 Private Placement to repay $75,500 in principal on the Duggan September Note. Refer to Note 9 for additional details regarding the promissory note payable to a related party.

Warrants Exercise

In March 2025, Mr. Duggan, our Co-Chief Executive Officer, exercised 2,936,221 of the 3,985,055 warrants which he received in connection with a private placement completed by the Company with Mr. Duggan and other investors on December 24, 2019, resulting in the purchase of 2,936,221 shares of common stock at an exercise price of $1.58.

On April 8, 2025, Mr. Duggan completed the exercise of the remaining warrants received in the December 24, 2019 private placement, resulting in the purchase of 1,048,834 shares of common stock at an exercise price of $1.58.

Professional Services

During the nine months ended September 30, 2025, the Company engaged the law firm Wilson Sonsini Goodrich & Rosati P.C. (“WSGR”), where Mr. Kenneth A. Clark, a member of the Board, is a partner. Payments to be made by the Company to WSGR were approved by the Audit Committee in accordance with its Related Party Transaction Policy. For the three and nine months ended September 30, 2025, the Company incurred expenses for legal services rendered by WSGR totaling approximately $0.7 million and $1.4 million respectively.

13. Commitments and Contingencies

Lease Commitments

On June 16, 2025, the Company entered into a non-cancelable sub-sublease for 36,406 square feet of office space in Palo Alto, California. As of September 30, 2025, the Company had undiscounted operating lease commitments of $22,336 that have not yet commenced. The operating lease is expected to commence during the first quarter of 2026, with a lease term of 94 months.

Other Commitments

The Company enters into contracts in the normal course of business with various third parties for clinical trials, preclinical research studies and testing, manufacturing and other services and products for operating purposes. Most contracts provide for termination upon notice, and therefore are cancellable contracts. The majority of these commitments are due withinone year. There have been no material changes to the Company’s other contractual commitments that were disclosed in the Company's Annual Report.

The Company has certain commitments under its agreements with Akeso. The License Agreement also contains certain manufacturing and purchase commitments. As of September 30, 2025, the Company is unable to estimate the amount, timing or likelihood of achieving the milestones, making future product sales or assessing estimated forecasts for manufacturing and supplied materials which these contingent payment obligations relate to.

Indemnifications

The Company's certificate of incorporation provides that it will indemnify the directors and officers to the fullest extent permitted by Delaware law. In addition, the Company has entered into indemnification agreements with all of the directors and executive officers. These indemnification agreements may require the Company, among other things, to indemnify each such director or executive officer for some expenses, including attorneys’ fees, judgments, fines, and settlement amounts incurred by him or her in any action or proceeding arising out of his or her service as one of the Company’s directors or executive officers. The Company believes the fair value for these indemnification obligations is minimal. Accordingly, the Company has not recognized any liabilities relating to these obligations as of September 30, 2025 and December 31, 2024.

Legal Proceedings

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. 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. Defendants believe that Plaintiff’s allegations are without merit and plan to vigorously defend against its claims.