and in Exhibit 99.1 shall not be deemed “filed” for purposes of Section 18 of the Securities Exchange Act of 1934, as amended (the “Exchange Act”), or otherwise subject to the liabilities of that section, nor shall it be deemed incorporated by reference in any filing under the Securities Act of 1933, as amended, or the Exchange Act, except as expressly set forth by specific reference in such filing.

Entry into a Material Definitive Agreement. On July 23, 2026, Summit Therapeutics Inc. (the “Company”) entered into a distribution agreement (the “Distribution Agreement”) with J.P. Morgan Securities LLC (“Sales Agent”), as sales agent, pursuant to which the Company may offer and sell, from time to time, through the Sales Agent, shares of the Company’s common stock, par value $0.01 per share, having an aggregate offering price of up to $380,000,000 (the “Shares”). The Company is not obligated…

and in Exhibit 99.1 shall not be deemed “filed” for purposes of Section 18 of the Securities Exchange Act of 1934, as amended (the “Exchange Act”), or otherwise subject to the liabilities of that section, nor shall it be deemed incorporated by reference in any filing under the Securities Act of 1933, as amended, or the Exchange Act, except as expressly set forth by specific reference in such filing.

and in Exhibit 99.1 shall not be deemed “filed” for purposes of Section 18 of the Securities Exchange Act of 1934, as amended (the “Exchange Act”), or otherwise subject to the liabilities of that section, nor shall it be deemed incorporated by reference in any filing under the Securities Act of 1933, as amended, or the Exchange Act, except as expressly set forth by specific reference in such filing.

as if fully set forth herein. On January 12, 2026, the Company issued a press release announcing the submission of a Biologics License Application to U.S. Food and Drug Administration seeking approval for ivonescimab in combination with chemotherapy in second line or later treatment of patients with epidermal growth factor receptor-mutated locally advanced or metastatic non-squamous non-small cell lung cancer. A copy of the press release is attached as Exhibit 99.2 to this Current Report on F…

Results of Operations and Financial Conditions. As of December 31, 2025, the preliminary unaudited balance of cash, cash equivalents, and short-term investments of Summit Therapeutics Inc. (the “Company”) was approximately $710 million. This amount is preliminary and is subject to completion of financial closing procedures. As a result, this amount may differ materially from the amount that will be reflected in the Company’s consolidated financial statements for the year ended December 31, 20…

Unregistered Sales of Equity Securities. The information contained in

Entry into a Material Definitive Agreement. On October 21, 2025, Summit Therapeutics Inc. (the “Company”) entered into securities purchase agreements (the “Purchase Agreements”) with multiple leading biotech institutional and individual accredited investors (the “Investors”), for the sale by the Company in a private placement (the “Private Placement”) of an aggregate of 26,682,846 shares (the “Shares”) of the Company’s common stock, par value $0.01 per share (the “Common Stock”), at purchase…

and in Exhibit 99.1 shall not be deemed “filed” for purposes of Section 18 of the Securities Exchange Act of 1934, as amended (the “Exchange Act”), or otherwise subject to the liabilities of that section, nor shall it be deemed incorporated by reference in any filing under the Securities Act of 1933, as amended, or the Exchange Act, except as expressly set forth by specific reference in such filing.

Entry into a Material Definitive Agreement. On August 11, 2025, Summit Therapeutics Inc. (the “Company”) entered into an amendment (the “Amendment”) to the distribution agreement with J.P. Morgan Securities LLC (“Sales Agent”), as sales agent, which amended that certain distribution agreement, dated May 13, 2024, by and between the Company and the Sales Agent (the “Original Distribution Agreement” and, as amended by the Amendment, the “Distribution Agreement”). Pursuant to the Amendment, the…

and in Exhibit 99.1 shall not be deemed “filed” for purposes of Section 18 of the Securities Exchange Act of 1934, as amended (the “Exchange Act”), or otherwise subject to the liabilities of that section, nor shall it be deemed incorporated by reference in any filing under the Securities Act of 1933, as amended, or the Exchange Act, except as expressly set forth by specific reference in such filing.

Entry into a Material Definitive Agreement. Effective June 16, 2025, Summit Therapeutics Inc. (the “Company”) entered into a sub-sublease between Ascendis Pharma, Inc., dated June 2, 2025, for 36,406 square feet of office space in Palo Alto, California (the “Sub-Sublease Agreement”). The effectiveness of the Sub-Sublease Agreement was conditioned upon obtaining the consent of the landlord and the sublandlord to the Sub-Sublease Agreement. The term of the Sub-Sublease Agreement commences on Ja…

and in Exhibit 99.1 shall not be deemed “filed” for purposes of Section 18 of the Securities Exchange Act of 1934, as amended (the “Exchange Act”), or otherwise subject to the liabilities of that section, nor shall it be deemed incorporated by reference in any filing under the Securities Act of 1933, as amended, or the Exchange Act, except as expressly set forth by specific reference in such filing.

and in Exhibit 99.1 shall not be deemed “filed” for purposes of Section 18 of the Securities Exchange Act of 1934, as amended (the “Exchange Act”), or otherwise subject to the liabilities of that section, nor shall it be deemed incorporated by reference in any filing under the Securities Act of 1933, as amended, or the Exchange Act, except as expressly set forth by specific reference in such filing.

The filing details compensation adjustments, including bonuses and salary increases for the CEO and CFO.

Results of Operations and Financial Conditions. As of December 31, 2024, the preliminary unaudited balance of cash, cash equivalents, and short-term investment of Summit Therapeutics Inc. (the “Company”) was no less than $410 million. This included the repayment of outstanding principal and interest totaling $31.8 million from a related party loan that was previously outstanding, as disclosed in the Company’s Form 10-Q for the quarter ended September 30, 2024, filed on October 30, 2024. This…

and in Exhibit 99.1 shall not be deemed “filed” for purposes of Section 18 of the Securities Exchange Act of 1934, as amended (the “Exchange Act”), or otherwise subject to the liabilities of that section, nor shall it be deemed incorporated by reference in any filing under the Securities Act of 1933, as amended, or the Exchange Act, except as expressly set forth by specific reference in such filing.

Unregistered Sales of Equity Securities. The information contained in

Entry into a Material Definitive Agreement. On September 11, 2024, Summit Therapeutics Inc. (the “Company”) entered into securities purchase agreements (the “Purchase Agreements”) with multiple leading biotech institutional and individual accredited investors (the “Investors”), for the sale by the Company in a private placement (the “Private Placement”) of an aggregate of 10,352,418 shares (the “Shares”) of the Company’s common stock, par value $0.01 per share (the “Common Stock”), at purchas…

Regulation FD Disclosure. Summit Therapeutics Inc. (the “Company”) announced data relating to the HARMONi-2 trial, conducted in China and sponsored by our collaboration partner, Akeso, Inc. (Akeso, HKEX Code: 9926.HK) (“Akeso”), with data generated and analyzed by Akeso. The data was presented as part of the Presidential Symposium at the International Association for the Study of Lung Cancer’s (“IASLC”) 2024 World Conference on Lung Cancer (“WCLC 2024”) by Dr. Caicun Zhou, Chief Physician and…

and in Exhibit 99.1 shall not be deemed “filed” for purposes of Section 18 of the Securities Exchange Act of 1934, as amended (the “Exchange Act”), or otherwise subject to the liabilities of that section, nor shall it be deemed incorporated by reference in any filing under the Securities Act of 1933, as amended, or the Exchange Act, except as expressly set forth by specific reference in such filing.

Director — Jeff Huber: Jeff Huber was elected as a director and appointed to the Audit Committee.

Entry into a Material Definitive Agreement. As previously disclosed, on January 8, 2024, Summit Therapeutics Inc. (the “Company”) entered into a lease agreement (the “Lease Agreement”) with Brickell Key Centre, LLC (“Landlord”), pursuant to which the Company leased office space for its Miami, Florida headquarter location ("Miami HQ"). The Lease Agreement commenced on February 1, 2024 and has a term of 64 months. The Lease Agreement permitted the Company to sublet any part of the premises with…

Director — Ujwala Mahatme: Resigned to focus on her increasing professional commitments outside the Company.

Entry into a Material Definitive Agreement. Private Placement On June 3, 2024, Summit Therapeutics Inc. (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”), for the sale by the Company in a private placement (the “Private Placement”) of 22,222,222 shares (the “Shares”) of the Company’s common stock, par value $0.01 per share (the “Common Stock”)…