Summit Therapeutics shares rose 16.99% in premarket trading after AstraZeneca agreed to invest $2 billion in newly issued Summit equity and expand a collaboration around cancer drug ivonescimab. AstraZeneca shares rose 1.22% in London trading, though its U.S.-listed shares later fell about 0.7% to $164.95 at 9:55 a.m. EST on Tuesday. AstraZeneca will acquire about 109,000 convertible preferred shares, each exchangeable for 1,000 Summit common shares, at roughly $18.35 per common-share equivalent. The investment would give AstraZeneca rights to about 12.0% of Summit's outstanding common stock, or 10.6% on a fully diluted basis. Closing is expected within a week, while conversion requires regulatory clearance. The companies will initially test ivonescimab, a first-in-class bispecific antibody targeting PD-1 and VEGF, with AstraZeneca's Claudin-18.2 antibody-drug conjugate sonesitatug vedotin in gastrointestinal cancers. They will share trial costs while retaining rights to their own medicines, and have signed a memorandum of understanding for a broader global program combining ivonescimab with additional AstraZeneca antibody-drug conjugates. Ivonescimab is approved in China for certain lung cancer patients and is under FDA review for EGFR-mutated non-small cell lung cancer.