AstraZeneca Makes $2 Billion Strategic Equity Investment in Summit Therapeutics

Investment in Preferred Shares Convertible to Common Equity, Equivalent to a Per-Share Price of Summit's Common Stock of $18.36, Representing a Premium over Today's Closing Trading Price

Summit Also Enters into Clinical Trial Collaboration with AstraZeneca to Evaluate Ivonescimab in Combination with Sonesitatug Vedotin in Multiple Gastrointestinal Cancers

Summit & AstraZeneca Plan to Enter into a Clinical Trial Collaboration Combining Ivonescimab with Multiple AstraZeneca ADCs and Other Cancer Medicines

MIAMI, September 28, 2026--Summit Therapeutics Inc. (Nasdaq: SMMT) today announced key developments important to the company's progress towards achieving its goal of making a significant difference in the lives of patients with cancer. Specifically, Summit has established agreements with AstraZeneca (LSE/STO/NYSE: AZN) for a strategic equity investment in Summit and a clinical collaboration focused on ivonescimab and sonesitatug vedotin (sone-ve). Moreover, Summit and AstraZeneca intend to evaluate ivonescimab with an additional set of AstraZeneca's cancer medicines, including other antibody drug conjugates (ADCs). Ivonescimab is a novel, potential first-in-class investigational PD-1 / VEGF bispecific antibody.

AstraZeneca Equity Investment in Summit

Summit and AstraZeneca have entered into an agreement whereby AstraZeneca will make an equity investment of $2.0 billion in convertible preferred shares. At the conversion ratio, the investment represents a common stock price equal to $18.36 representing a premium over today's closing price.

"This significant investment, as well as the collaboration, is a powerful validation of the potential of ivonescimab," said Robert W. Duggan, Chairman and Co-Chief Executive Officer of Summit Therapeutics. "We are proud to welcome AstraZeneca as a strategic investor as we continue to work with purposeful urgency to make a significant difference for patients with cancer by improving outcomes."

Summit – AstraZeneca Clinical Trial Collaboration: Ivonescimab and Sone-Ve

Summit entered into a clinical collaboration agreement with AstraZeneca to evaluate sonesitatug vedotin in combination with ivonescimab with the intent to start studies in certain gastrointestinal (GI) cancer settings imminently. Sone-ve is a potential global first-in-class Claudin 18.2-targeting ADC with several ongoing trials underway in GI cancers.

Under the terms of the clinical collaboration agreement, each company will contribute their respective compound for the combination studies to be conducted, and the parties will jointly contribute to the costs of such studies, which are intended to be sponsored by AstraZeneca. Each company will retain development and commercial rights to their respective molecules.