AstraZeneca Investment in Summit Therapeutics Sets Stage

AstraZeneca investment in Summit Therapeutics, announced Sept. 28, 2026, will support a clinical collaboration combining a PD-1/VEGF bispecific with a Claudin-18.2 antibody-drug conjugate (ADC), accelerating Summit’s ADC combination program and altering its shareholder structure.

Deal Terms and Ownership

AstraZeneca agreed to invest $2.0 billion in Summit Therapeutics through newly issued convertible preferred shares. Summit said AstraZeneca will purchase about 108,955 preferred shares convertible into common stock at a 1:1,000 ratio, implying an effective common-stock price of $18.36 per share. This price was calculated as the prior week’s five-day volume-weighted average price plus 10%.

The investment will give AstraZeneca rights equivalent to roughly 12.0% of Summit’s outstanding common stock, or about 10.6% on a fully diluted basis. Summit expected the preferred-share transaction to close within a week of the announcement, subject to customary closing conditions. Any later conversion of the preferred shares into common stock will require customary regulatory clearances.

Clinical Collaboration Plans

The companies will evaluate sonesitatug vedotin in combination with ivonescimab in multiple gastrointestinal cancers and plan to begin trials under the collaboration imminently. Ivonescimab is an investigational PD-1/VEGF bispecific antibody described as first-in-class, while sonesitatug vedotin is an investigational Claudin-18.2-targeting ADC carrying a monomethyl auristatin E payload.

Each company will supply its respective medicine and share trial costs. Both will retain development and commercial rights to their own products. The companies also signed a memorandum of understanding to pursue a global development program combining ivonescimab with AstraZeneca cancer medicines, including additional ADCs. This broader program is an intended future agreement rather than a completed partnership.