AstraZeneca Invests $2 Billion in Summit's Ivonescimab ADC Combo

AstraZeneca will invest $2 billion in newly issued equity of Summit Therapeutics Inc. and has entered a clinical collaboration to test ivonescimab, Summit's first-in-class programmed cell death protein 1 (PD-1)/vascular endothelial growth factor (VEGF) bispecific antibody, in combination with AstraZeneca's antibody-drug conjugates (ADCs) across multiple tumor types, the companies announced September 28, 2026.¹

What does the equity investment involve?

AstraZeneca will purchase approximately 109,000 shares of Summit preferred stock, convertible into common stock at a 1:1,000 ratio.¹ Once complete, AstraZeneca will hold rights equivalent to approximately 12.0% of Summit's outstanding common stock, or about 10.6% on a fully diluted basis.¹ Closing is expected within 1 week. Converting the shares into common stock will require regulatory clearances, AstraZeneca said in a company press release.¹

"A core pillar of our oncology strategy is to broaden the reach of our ADC portfolio as the backbone of treatment across tumour types with combinations alongside next-generation immunotherapies," said Susan Galbraith, PhD, AstraZeneca's executive vice president of oncology hematology R&D, in the release.¹ "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."

What will the sonesitatug vedotin-ivonescimab collaboration study?

AstraZeneca and Summit also signed a clinical collaboration agreement to evaluate sonesitatug vedotin (Sone-Ve), an investigational claudin-18.2 (CLDN18.2)-targeted ADC carrying a monomethyl auristatin E payload, in combination with ivonescimab. The companies intend to initiate trials in gastrointestinal cancers under the agreement imminently, contributing their own medicines and sharing trial costs while retaining commercial rights to each.¹

The companies also signed a memorandum of understanding outlining intent to launch a broader global development program pairing ivonescimab with additional AstraZeneca cancer medicines, including other ADCs. Maky Zanganeh, DDS, Summit's president and co-CEO, said in the release that the agreements broaden ivonescimab's development plan and open trials combining it with novel anti-cancer compounds, including ADCs.¹

What clinical evidence supports pairing the 2 drugs?

AstraZeneca has reported that sonesitatug vedotin met its primary endpoint in the phase 3 CLARITY-Gastric01 trial, showing a statistically significant and clinically meaningful overall survival improvement among patients with 2nd- and later-line claudin18.2-positive advanced gastric or gastroesophageal junction cancer, versus investigator's choice of therapy. Full results are expected at the European Society for Medical Oncology Congress 2026.¹ A fuller company update on that trial specified dual primary endpoints were met, though progression-free survival by independent central review did not reach statistical significance.²

Ivonescimab, engineered by Akeso and licensed to Summit outside China, is approved in China for certain non-small cell lung cancer (NSCLC) patients. Its activity already has peer-reviewed backing. In the phase 3 HARMONi-2 trial published in The Lancet, ivonescimab nearly doubled median progression-free survival versus pembrolizumab (11.1 vs 5.8 months; hazard ratio, 0.51) in 398 patients with programmed cell death ligand 1-positive NSCLC.³

Ivonescimab is separately under FDA review for epidermal growth factor receptor-mutated NSCLC. The agency accepted Summit's biologics license application (BLA) for that indication in January 2026, with a Prescription Drug User Fee Act goal date of November 14, 2026, based on the phase 3 HARMONi trial.⁴ The biologic is also in phase 3 trials for small cell lung cancer, biliary tract cancer, bladder cancer, triple-negative breast cancer, head and neck squamous cell carcinoma, colorectal cancer, and pancreatic cancer.¹

What are the limitations?

The memorandum of understanding for a broader ivonescimab–ADC program reflects intent rather than a signed agreement, and its terms could change before a final deal is reached. FDA’s acceptance of Summit's BLA for ivonescimab in NSCLC does not necessarily guarantee approval, and the November 14, 2026, goal date could be extended. The CLARITY-Gastric01 results remain topline data that have not been peer-reviewed or presented in full.² The gastrointestinal-cancer trials combining sonesitatug vedotin and ivonescimab have not yet begun.

References

1. AstraZeneca. AstraZeneca announces strategic equity investment and clinical collaboration with Summit Therapeutics to advance leading ADC combination strategy in cancer. Press release. Published September 28, 2026. Accessed September 29, 2026. https://www.astrazeneca.com/media-centre/press-releases/2026/astrazeneca-announces-equity-investment-summit.html
2. AstraZeneca. Sonesitatug vedotin demonstrated a statistically significant and highly clinically meaningful improvement in overall survival in 2nd and later-line CLDN18.2-positive advanced gastric/GEJ cancers. Press release. Published July 27, 2026. Accessed September 29, 2026. https://www.astrazeneca.com/media-centre/press-releases/2026/sone-ve-improved-survival-in-gastric-cancers.html
3. Xiong A, Wang L, Chen J, et al. Ivonescimab versus pembrolizumab for PD-L1-positive non-small cell lung cancer (HARMONi-2): a randomized, double-blind, phase 3 study in China. Lancet. 2025;405(10481):839-849. doi:10.1016/S0140-6736(24)02722-3
4. Summit Therapeutics. Summit Therapeutics announces US FDA acceptance of biologics license application (BLA) seeking approval for ivonescimab in combination with chemotherapy in treatment of patients with EGFRm NSCLC post-TKI therapy. Press release. Published January 29, 2026. Accessed September 29, 2026. https://smmttx.com/news/press-releases/news-details/2026/Summit-Therapeutics-Announces-U-S--FDA-Acceptance-of-Biologics-License-Application-BLA-Seeking-Approval-for-Ivonescimab-in-Combination-with-Chemotherapy-in-Treatment-of-Patients-with-EGFRm-NSCLC-Post-TKI-Therapy/default.aspx