Nature of Business and Operations and Recent Events	12 Months Ended
Nature of Business and Operations and Recent Events	Dec. 31, 2023
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Nature of Business and Operations and Recent Events	Nature of Business and Operations and Recent Events Nature of Business and Operations 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 (“Akeso”) pursuant to which the Company has in-licensed ivonescimab. Through the License Agreement (as defined in Note 6), the Company obtained the rights to develop and commercialize ivonescimab in the United States, Canada, Europe, and Japan (the “Licensed Territory”). The License Agreement and transaction closed in January 2023 following customary waiting periods. The Company’s operations will be focused on the development of ivonescimab and other future activities, as the Company determines. The Company has begun its development for ivonescimab in non-small cell lung cancer (“NSCLC”), specifically launching Phase III clinical trials in the following indications: a) ivonescimab combined with chemotherapy in patients with epidermal growth factor receptor (“EGFR”)-mutated, locally advanced or metastatic non-squamous NSCLC who have progressed after treatment with a third-generation EGFR tyrosine kinase inhibitor (“TKI”) (“HARMONi”); and b) ivonescimab combined with chemotherapy in first-line metastatic squamous NSCLC patients (“HARMONi-3”) As of the date of these financial statements, both studies are enrolling patients. The entry into the License Agreement with Akeso represents a significant change in the Company’s strategy and its future operations will be focused on the development of ivonescimab and other future activities as the Company determines. The Company’s portfolio includes ridinilazole, a product candidate for treating patients suffering from Clostridioides difficile infection, also known as C. difficile infection, or CDI. All prior development and marketing activities related to ridinilazole have been terminated. The Company’s anti-infectives portfolio includes SMT-738, the first of a novel class of precision antibiotics for combating multidrug resistant infections, specifically carbapenem-resistant Enterobacteriaceae (“CRE”) infections. The Company will continue to pursue partnerships for further development of SMT-738. Recent Events In addition to the events detailed in the Company Overview section above, the following other recent developments have occurred. As noted above, on December 5, 2022, the Company entered into a Collaboration and License Agreement (the “License Agreement”) with Akeso pursuant to which the Company is in-licensing breakthrough bispecific antibody, ivonescimab (Note 6). On December 6, 2022, the Company entered into a Note Purchase Agreement (the “Note Purchase Agreement”), with Mr. Robert Duggan and Dr. Maky 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 (Note 18). On January 19, 2023, the Company filed Amendment No. 2 to the Restated Certificate of Incorporation (the “Amendment No. 2”) with the Secretary of State of the State of Delaware to increase the number of authorized shares of its common stock by 650,000,000 (from 350,000,000 to 1,000,000,000), which became effective on such date. On February 7, 2023, the Company commenced its previously announced rights offering (“2023 Rights Offering”). On March 1, 2023, the Company closed the 2023 Rights Offering, which was fully subscribed. The Company received aggregate gross proceeds from the 2023 Rights Offering of $500,000 from the sale of 476,190,471 shares of its common stock at a price per share of $1.05. Issuance costs associated with the 2023 Rights Offering were approximately $619. In connection with the closing of the 2023 Rights Offering, $400,000 of the unsecured promissory notes, issued by the Company to Mr. Duggan, matured and became due and the Company repaid the principal amount and all outstanding accrued interest thereunder using a portion of the proceeds from this 2023 Rights Offering (Note 18). On February 15, 2023, $20,000 of the unsecured promissory notes, issued by us to Dr. Zanganeh, matured and the Company repaid the outstanding principal balance. On March 17, 2023, the Company filed a registration statement on Form S-3 to register for resale the following shares of its common stock at $0.01 par value: (i) 10,000,000 shares of Common Stock issued on January 17, 2023 in connection with the License Agreement with Akeso pursuant to which the Company issued Akeso such shares; and (ii) the 9,346,434 and 373,857 shares of common stock issued in December 2022 to its Chief Executive Officers, Mr. Robert Duggan and Dr. Mahkam Zanganeh, respectively, as payment of prepaid interest in connection with the Note Purchase Agreement dated December 6, 2022 between Mr. Duggan, Dr. Zanganeh and the Company (Note 18). On April 27, 2023, the SEC issued a Notice of Effectiveness for the registration statement on Form S-3 filed with the SEC. On October 12, 2023, the Company held a Special Meeting of Stockholders (the “October Special Meeting”) whereby an amendment to the Summit Therapeutics Inc. 2020 Stock Incentive Plan (the “Plan”) to increase the number of shares of the Company’s common stock issuable under the Plan by 70,000,000 shares was approved by a vote of the Company’s stockholders at the Special Meeting and subsequently ratified by the Board of Directors. On October 16, 2023, the Company announced the appointment of Mr. Manmeet Soni as its Chief Operating Officer, effective immediately. Mr. Soni has been a part of the Company’s Board of Directors since 2019. He will remain a member of the Board of Directors. In conjunction with his appointment, Mr. Soni entered into a share purchase agreement with the Company to purchase $5,000 of its common stock via a private placement. The transaction was effective October 13, 2023 with a closing price of $1.68, resulting in the purchase of 2,976,190 shares of the Company’s common stock. On February 17, 2024 the 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 shall accrue on the outstanding principal balance at the greater of 12% or the US prime interest rate, as reported in the Wall Street Journal plus 350 basis points, as adjusted monthly, compounded quarterly (Note 18). Interest shall be paid upon maturity of the loan.