Ivonescimab Beats Imfinzi on Overall Survival in Biliary Tract Cancer

Summit Therapeutics (SMMT) partner Akeso just delivered the first Phase 3 win for a checkpoint combination in biliary tract cancer, and the fifth positive Phase 3 result overall for ivonescimab. In the China-only HARMONi-GI1 trial, ivonescimab plus chemotherapy beat durvalumab plus chemotherapy on overall survival in first-line advanced biliary tract cancer, meeting the primary endpoint at a pre-specified interim analysis. The trial also hit its secondary endpoints of progression-free survival and objective response rate.

The readout matters because the comparator is the global standard of care. Durvalumab (AstraZeneca’s Imfinzi) plus chemotherapy became the preferred first-line biliary regimen after the TOPAZ-1 trial, so beating it on overall survival is a genuine bar to clear. Biliary tract cancer is aggressive and hard to treat, with median survival under two years even on the best regimens. Ivonescimab is a PD-1/VEGF bispecific antibody that blocks the PD-1 immune checkpoint and traps VEGF, the protein that feeds tumor blood vessels, in a single molecule.

But investors should separate signal from catalyst. HARMONi-GI1 is a single-region trial run by Akeso in China, and Summit, which holds ex-China rights to the drug, has no US filing for biliary tract cancer. A China-only Phase 3 does not directly support a US approval, which typically requires registrational data from trials that include US sites. This readout validates the molecule’s reach beyond lung cancer, where its first four positive Phase 3 results came; it does not add near-term US revenue.

Ivonescimab has now gone five for five in Phase 3, across HARMONi, HARMONi-A, HARMONi-2, and HARMONi-6 in lung cancer plus this first gastrointestinal result. The breadth supports Summit’s thesis that one bispecific antibody can work across many solid tumors through a single mechanism. Ivonescimab is already approved in China for first-line squamous non-small cell lung cancer, and this readout gives Akeso a filing-ready dataset for the NMPA in biliary tract cancer.

Summit’s actual near-term event remains the November 14 PDUFA date for ivonescimab in EGFR-mutant NSCLC (the FDA’s deadline to decide on the drug application). The stock rose 4.95% to $13.36 on the news, and at a roughly $11 billion market cap, most of that valuation still hangs on the lung cancer decision. Summit has been expanding ivonescimab aggressively, including the HARMONi-GU1 bladder cancer trial. What to watch next: the detailed HARMONi-GI1 data at an upcoming conference, which will show the size of the survival benefit, and whether Akeso files for approval in China.

Source: Akeso press release