Summit Therapeutics and ECOG-ACRIN Cancer Research Group Enter into Phase II / III Clinical Trial Collaboration to Evaluate Ivonescimab in First-Line Biliary Tract Cancer

Clinical Trial Site Activations in the United States Expected to Begin Q4 2026

MIAMI, October 21, 2026--Summit Therapeutics Inc. (NASDAQ: SMMT) today announced a clinical trial collaboration with the ECOG-ACRIN Cancer Research Group (ECOG-ACRIN) to evaluate ivonescimab, a novel, potential first-in-class investigational bispecific antibody, in a registration-enabling Phase II/III study in biliary tract cancer (BTC). The new study, EA2251 (NCT07765433), is designed to evaluate the safety and efficacy of ivonescimab with chemotherapy compared to pembrolizumab or durvalumab plus chemotherapy in the first-line treatment of patients with advanced BTC.

"Biliary tract cancer is often diagnosed at an advanced stage, and despite recent progress, there is a need for more effective first-line options that can extend survival and improve disease control," said lead investigator Deirdre J. Cohen, MD, MS, Associate Professor of Medicine at the Icahn School of Medicine at Mount Sinai, Director of the Gastrointestinal Oncology Program for the Mount Sinai Health System and Co-Director of the Center of Excellence for Pancreatic Cancer at the Mount Sinai Tisch Cancer Center. "EA2251 will explore a novel therapeutic approach in the front-line setting by evaluating ivonescimab with chemotherapy against current immunotherapy-based standards of care."

The open-label Phase II/III EA2251 study plans to enroll patients in the U.S. who will be randomized to receive ivonescimab in combination with gemcitabine and cisplatin, or pembrolizumab or durvalumab in combination with gemcitabine and cisplatin as the established standard-of-care comparator regimen. The primary endpoint for the study is overall survival (OS). Activation of clinical trial sites is expected to begin in the fourth quarter of 2026.

"We are honored to collaborate with ECOG-ACRIN on EA2251 as we continue to expand the development program for ivonescimab in areas of meaningful unmet need," said Dr. Maky Zanganeh, President and Co-Chief Executive Officer of Summit Therapeutics. "The sponsorship and conduct of this registration-enabling study by a leading cooperative oncology group underscores the scientific interest in evaluating ivonescimab in difficult-to-treat cancers, including BTC, and supports Summit's commitment to building a robust body of clinical evidence across multiple tumor types and treatment settings."

For additional information on EA2251, please see ECOG-ACRIN's accompanying press release.

EA2251 is the second Phase III study of ivonescimab in BTC; the first is HARMONi-GI1. In August 2026, Akeso Inc. announced the randomized Phase III HARMONi-GI1 study (AK112-309) evaluating ivonescimab plus chemotherapy compared with durvalumab plus chemotherapy as a first-line treatment for patients with BTC achieved statistically significant and clinically meaningful superiority in the primary endpoint of OS compared to the durvalumab-based regimen at a pre-specified interim analysis.