Izalontamab brengitecan (iza‑bren) extended survival in Phase 3 trials for triple‑negative breast cancer and esophageal squamous cell carcinoma, with consistent benefit across three tumor types. Data presented at ASCO 2026 highlight the EGFR×HER3 bispecific ADC’s potential as a new treatment option in aggressive solid cancers.
Written By: Dr. Preethi Putti, PharmD
Reviewed By: Pharmacally Editorial Team
SystImmune and Bristol Myers Squibb reported positive interim Phase 3 results for izalontamab brengitecan (iza-bren), demonstrating significant improvements in overall survival (OS) and progression-free survival (PFS) in advanced triple-negative breast cancer (TNBC) and recurrent or metastatic esophageal squamous cell carcinoma (ESCC).
Presented at the 2026 ASCO Annual Meeting, the data mark the third successful Phase 3 study for the EGFR×HER3 bispecific antibody-drug conjugate (ADC), following positive results in nasopharyngeal carcinoma.
Mechanism of Action: Dual Targeting with Cytotoxic Activity
Iza-bren targets both epidermal growth factor receptor (EGFR) and human epidermal growth factor receptor 3 (HER3), two proteins commonly overexpressed in epithelial cancers. The bispecific antibody blocks signaling through both pathways while delivering a topoisomerase I inhibitor payload into tumor cells, triggering DNA damage and cell death. This dual mechanism may help address treatment resistance across multiple solid tumors.
PANKU-Breast02: Survival Gains in TNBC
The Phase 3 PANKU-Breast02 study (NCT06382142) enrolled patients with unresectable locally advanced or metastatic TNBC whose disease progressed after one or two prior systemic regimens, including taxane therapy. Patients received either iza-bren or physician’s choice chemotherapy.
Iza-bren delivered clinically meaningful efficacy benefits across all major endpoints. Median overall survival improved to 15.9 months compared with 12.5 months for chemotherapy (HR 0.60; p=0.0019), while median progression-free survival increased to 8.5 months from 3.1 months (HR 0.29; p<0.0001). The treatment also more than doubled objective response rates, achieving 51.7% compared with 20.5% in the chemotherapy arm.
Grade ≥3 adverse events were mainly hematologic and consistent with the known safety profile. Interstitial lung disease occurred in 1.4% of patients, while treatment discontinuation due to adverse events remained low at 1.9%. Investigators noted this is the first Phase 3 bispecific ADC study in TNBC to demonstrate improvements in both OS and PFS.
PANKU-Esophagus01: Improved Outcomes in ESCC
The Phase 3 PANKU-Esophagus01 trial (NCT06304974) evaluated patients with recurrent or metastatic ESCC whose disease progressed after PD-1/PD-L1 inhibitor and platinum-based chemotherapy. Patients received iza-bren or physician’s choice chemotherapy.
Iza-bren also demonstrated significant efficacy in ESCC, extending median overall survival to 9.8 months compared with 7.2 months for chemotherapy (HR 0.64; p=0.0004). Median progression-free survival doubled from 2.0 months to 4.2 months (HR 0.50; p<0.0001), while objective response rates improved from 13.1% to 35.3%, highlighting consistent antitumor activity across key clinical endpoints.
Grade ≥3 treatment-related adverse events occurred in 85.1% of patients receiving iza-bren versus 60.2% with chemotherapy. However, treatment discontinuation and treatment-related death rates remained comparable between treatment arms. The study represents the first Phase 3 bispecific ADC trial to achieve positive OS and PFS results in ESCC.
Regulatory Outlook and Future Development
A New Drug Application for recurrent or metastatic ESCC has been accepted by China’s National Medical Products Administration and granted priority review. Outside China, SystImmune and Bristol Myers Squibb continue to advance a global development program across multiple tumor types and treatment settings.
Expanding the Role of Bispecific ADCs
With positive Phase 3 results in TNBC, ESCC, and nasopharyngeal carcinoma, iza-bren has emerged as one of the most advanced EGFR×HER3 bispecific ADCs in development. If confirmed through regulatory review, the therapy could expand treatment options for patients with several aggressive cancers and further validate the growing role of bispecific ADCs in oncology.
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About the Writer
Dr.Preethi Putti, PharmD (LinkedIn) is a pharmaceutical researcher with experience in healthcare and pharmaceutical market research and competitive intelligence. She specializes in analyzing drug pipelines, clinical data, and industry trends and translating complex scientific data into clear and structured medical content. Strong foundation in clinical research, data interpretation, and evidence-based healthcare analysis. Committed to advancing a global career in clinical research and healthcare innovation.