Bispecific Immunotherapy Beats Standard-of-Care in Advanced Biliary Tract Cancer, Phase 3 Trial Shows

What This Article Covers

On August 25–26, 2026, Akeso Inc. and its U.S. partner Summit Therapeutics announced that the Phase 3 HARMONi-GI1 trial met its primary endpoint: previously untreated patients with advanced biliary tract cancer who received the bispecific antibody ivonescimab plus chemotherapy lived statistically significantly longer than patients who received durvalumab (Imfinzi) plus the same chemotherapy — durvalumab being the internationally recognized preferred first-line immunotherapy regimen for this disease. Biliary tract cancers (gallbladder and bile duct cancers) are rare, aggressive, and had seen essentially no change in first-line standard of care for more than a decade before durvalumab's own approval. This piece explains what ivonescimab is, what HARMONi-GI1 actually showed, how it fits against the durvalumab benchmark it beat, and — importantly — what has not yet been disclosed and why that matters before anyone calls this practice-changing.

The Disease and Why the Comparator Matters

Biliary tract cancer carries a poor prognosis, and until recently the backbone regimen — gemcitabine plus cisplatin chemotherapy — had gone unchanged for over ten years. That changed with durvalumab, an anti-PD-L1 checkpoint inhibitor, which in the pivotal TOPAZ-1 trial improved 24-month overall survival to 24.9% versus 10.4% for chemotherapy alone (hazard ratio 0.80), establishing durvalumab plus chemotherapy as the modern first-line standard. Any therapy that beats that bar on overall survival — the gold-standard endpoint in oncology — in a head-to-head randomized trial is a meaningful development, not an incremental one.

What Ivonescimab Is

Ivonescimab (also known as AK112 in China and SMT112 in the West) is a bispecific antibody engineered to bind two different targets at once: PD-1, which it uses to help the immune system recognize and attack cancer cells, and VEGF, which it uses to choke off the blood vessel growth tumors depend on. That dual mechanism is the therapy's core selling point over single-target checkpoint inhibitors like durvalumab, which blocks only PD-L1. Ivonescimab is already approved and commercially available in China for certain non-small cell lung cancer indications; it remains investigational — not yet approved — in the United States and Europe. Notably, the FDA has already accepted a Biologics License Application for ivonescimab in a different indication (EGFR-mutated NSCLC after prior TKI therapy), with a decision expected around November 2026 — a signal that U.S. regulators are actively reviewing the drug, separate from this new biliary tract cancer data.

What the HARMONi-GI1 Data Actually Shows

HARMONi-GI1 was a randomized, double-blind Phase 3 trial enrolling 682 patients with unresectable, locally advanced, or metastatic biliary tract cancer who had not yet received treatment for advanced disease. Patients were randomized to ivonescimab plus gemcitabine/cisplatin or durvalumab plus the identical chemotherapy backbone, with overall survival as the primary endpoint. At a prespecified interim analysis, ivonescimab's arm showed a statistically significant overall survival advantage over the durvalumab arm, and it also cleared the secondary endpoints of progression-free survival and objective response rate. Trade press covering the announcement called it the first Phase 3 trial to demonstrate statistically significant overall survival superiority over an anti-PD-(L)1-plus-chemotherapy regimen in advanced biliary tract cancer — a real milestone given how entrenched the durvalumab backbone has become internationally since TOPAZ-1. The news moved markets: Summit Therapeutics' shares jumped roughly 15% in premarket trading the day of the announcement.

The Important Caveats

This is genuinely encouraging news, but it is not yet a complete picture, and readers should hold two things in mind. First, only topline results have been disclosed. Neither company has released the actual survival numbers — no median overall survival figures, no hazard ratio, no confidence intervals, and no detailed safety data. Both companies say the full efficacy and safety results will be presented at an upcoming medical congress and published in a peer-reviewed journal; until that happens, the size of the benefit (and the price paid in side effects) can't be independently assessed. Second, and just as important, HARMONi-GI1 was conducted exclusively at sites in China, enrolling a China-based patient population. Ivonescimab's prior lung cancer data has shown a meaningfully smaller survival benefit in Western patient cohorts than in Chinese cohorts in past trials, so it is not guaranteed this biliary tract cancer result will translate identically to patients in the U.S. or Europe — a gap that will only be answered by future trials enrolling outside China, or by regulatory review of this specific dataset. Ivonescimab is not FDA-approved for any indication in the United States, and biliary tract cancer is not among the indications currently under FDA review.

What Happens Next

Watch for two things: the full presentation of HARMONi-GI1's efficacy and safety data at a major oncology congress, which will let clinicians actually evaluate the magnitude of the survival benefit and its toxicity profile; and Summit Therapeutics' regulatory strategy for bringing ivonescimab's biliary tract cancer data to U.S. and European regulators, which has not yet been announced. Separately, the FDA's pending November 2026 decision on ivonescimab for EGFR-mutated NSCLC (an unrelated indication) will be an early read on how U.S. regulators view the drug's data package generally.

Bottom Line

A large, randomized Phase 3 trial has shown that a next-generation bispecific immunotherapy can beat the current international gold-standard treatment on overall survival in a hard-to-treat cancer — a genuinely hopeful signal for a disease that saw little progress for a decade. But the actual size of that benefit isn't public yet, the trial was conducted only in China, and the drug remains unapproved anywhere outside China for this use, so patients and clinicians elsewhere should treat this as an important development to watch closely rather than a new treatment option available today.