AstraZeneca (LSE:AZN) has agreed to invest $2 billion in newly issued equity of Summit Therapeutics, alongside a clinical collaboration to test Summit's cancer drug ivonescimab in combination with AstraZeneca's antibody drug conjugates (ADCs).
The investment buys AstraZeneca preferred stock convertible into common shares at a 1:1,000 ratio, equivalent to approximately 12% of Summit's outstanding common stock, or 10.6% on a fully diluted basis, with closing expected within a week.
Ivonescimab is a bispecific antibody targeting PD-1 and VEGF, engineered by China's Akeso, with Summit holding development and commercial rights outside China; it is already approved for certain lung cancer patients in China, and a US approval application is under FDA review.
The first study under the new collaboration will pair ivonescimab with sonesitatug vedotin (Sone-Ve), AstraZeneca's Claudin-18.2-targeting ADC, in gastrointestinal cancers, with trials due to start imminently; each company retains rights to its own drug and contributes to trial costs.
AstraZeneca licensed Sone-Ve globally from KYM Biosciences in March 2023, and recently reported that the drug showed a statistically significant survival benefit in a Phase III gastric cancer trial, data due for presentation at the European Society for Medical Oncology Congress 2026.
The companies also signed a non-binding memorandum of understanding to pursue a broader global programme combining ivonescimab with AstraZeneca's wider ADC portfolio.
"Bispecifics targeting PD-1 and VEGF are rapidly advancing in development and have the potential to improve on current immunotherapies, particularly in lung, breast and gastrointestinal cancers," said Susan Galbraith, AstraZeneca's oncology haematology R&D chief.
Conversion of AstraZeneca's preferred stock into common shares remains subject to regulatory clearances.