Ivonescimab Plus Chemotherapy Demonstrates Statistically Significant Overall Survival Benefit Compared to Durvalumab Plus Chemotherapy in First-Line Advanced Biliary Tract Cancer in Single-Region Trial Conducted by Akeso in China

HARMONi-GI1 Conducted in China by Akeso Is First Known Phase III Study in Advanced BTC to Demonstrate OS Superiority vs. Anti-PD-(L)1 Plus Chemotherapy

First Phase III Ivonescimab Readout beyond NSCLC Demonstrates Significant OS Benefit

MIAMI, August 25, 2026--Summit Therapeutics Inc. (NASDAQ: SMMT) today noted that its partner Akeso Inc. announced positive topline results from 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 advanced biliary tract cancer (BTC). HARMONi-GI1 is a single-region, multi-center, Phase III study conducted in China and sponsored by Akeso, with all relevant data exclusively generated, managed, and analyzed by Akeso.

Akeso reported that, at a pre-specified interim analysis, the ivonescimab-based regimen achieved statistically significant and clinically meaningful superiority in the primary endpoint of overall survival (OS) compared to the durvalumab-based regimen. The study also met the key secondary endpoints of progression-free survival (PFS) and objective response rate (ORR). Detailed results from this first readout of HARMONi-GI1, including safety and efficacy data, are expected to be presented at an upcoming medical congress and published in a peer-reviewed journal.

Akeso's press release announcing these results can be found here.

The HARMONi-GI1 study was conducted by Akeso in China, where ivonescimab is approved and commercially available for indications in non-small cell lung cancer (NSCLC). Ivonescimab remains investigational and is not approved by any regulatory authority in Summit's license territories, including the United States and Europe.

About Ivonescimab

Ivonescimab, known as SMT112 in Summit's license territories, North America, South America, Europe, the Middle East, Africa, and Japan, and as AK112 outside of Summit's license territories, is a novel, potential first-in-class investigational bispecific antibody combining the effects of immunotherapy via a blockade of PD-1 with the anti-angiogenesis effects associated with blocking VEGF into a single molecule. By design, ivonescimab displays unique cooperative binding to each of its intended targets with multifold higher affinity to PD-1 when in the presence of VEGF.

This design is intended to differentiate ivonescimab as there is potentially higher expression (presence) of both PD-1 and VEGF in tumor tissue and the tumor microenvironment (TME) as compared to normal tissue in the body. Summit believes ivonescimab's specifically engineered tetravalent structure (four binding sites) enables higher avidity (accumulated strength of multiple binding interactions) in the TME (Zhong, et al, iScience, 2025). This tetravalent structure, the intentional novel design of the molecule, and bringing these two targets into a single bispecific antibody with cooperative binding qualities have the potential to direct ivonescimab to the tumor tissue versus healthy tissue. The intent of ivonescimab's design, together with a half-life of 6 to 7 days after the first dose (Zhong, et al, iScience, 2025) increasing to approximately 10 days at steady state dosing, is to improve upon previously established efficacy thresholds, side effects, and safety profiles associated with prior approved drugs to these targets.