AstraZeneca is investing $2 billion for roughly a 12% stake in Summit Therapeutics and will launch a new combination trial pairing Summit’s PD-1/VEGF bispecific ivonescimab with AstraZeneca’s CLDN18.2 ADC sonesitatug vedotin in gastrointestinal cancers. The deal follows fresh momentum for ivonescimab, including HARMONi-2 data showing a 27% reduction in risk of death vs. pembrolizumab in PD-L1–positive NSCLC, and sent Summit shares up more than 16% after hours.

Why It Matters To Oncology

• The agreement links one of the most closely watched bispecific immunotherapies with AstraZeneca’s push to make ADCs a treatment backbone across tumor types.

• The first planned study will test ivonescimab plus sonesitatug vedotin in GI cancers, a setting where both agents have shown clinical momentum.

• For drug discovery teams, the move underscores growing interest in combining next-generation IO agents with ADCs to extend efficacy beyond monotherapy.

The Financials

• AstraZeneca will buy about 109,000 Summit shares for $2 billion, equal to roughly 12% of outstanding common stock, or about 10.6% on a fully diluted basis.

• The investment is expected to close within a week.

• Summit shares jumped more than 16% in after-hours trading following the announcement.

• Both companies will contribute their drugs to the initial trial and split study costs, while keeping development and commercial rights to their own products.

What They're Saying

• AstraZeneca’s Susan Galbraith said a core oncology priority is broadening the company’s ADC portfolio through combinations with next-generation immunotherapies.

• She added that PD-1/VEGF bispecifics could improve on current immunotherapies, particularly in lung, breast and GI cancers.

• The companies also signed a memorandum of understanding to explore a broader global development program combining ivonescimab with additional AstraZeneca cancer medicines, including ADCs.

What's Next

• The initial GI cancer combination trial will pair ivonescimab with sonesitatug vedotin.

• AstraZeneca and Summit intend to expand into additional combination studies across the oncology portfolio.

• Upcoming data to watch include AstraZeneca’s planned ESMO presentation of Phase III CLARITY-Gastric01 results for sonesitatug vedotin in advanced gastric cancer.

• Further readouts for ivonescimab in NSCLC and GI tumors could shape how aggressively developers pursue PD-1/VEGF bispecific-plus-ADC strategies.