Iza-bren (izalontamab brengitecan) significantly extended progression-free survival, reducing the risk of disease progression or death by 59% versus chemotherapy in the Phase 3 PANKU-Breast01 trial for unresectable locally advanced, recurrent or metastatic HR+/HER2- breast cancer after at least one prior chemotherapy line, with a median PFS of 15.2 months versus 8.2 months for iza-bren and 4.0 months for chemotherapy (HR 0.41, p<0.0001).

The trial is sponsored by Sichuan Biokin Pharmaceutical in Mainland China, with outside-China development conducted through a collaboration between SystImmune and Bristol Myers Squibb."

Overall survival data were immature at the interim analysis.

PANKU-Breast01 results are being presented at ESMO 2026 and were published in The Lancet; the interim analysis was prespecified.

The safety profile was manageable with no new safety signals; Grade ≥3 TRAEs were mainly hematologic, and only 1.6% of patients discontinued due to TRAEs; adjudicated ILD occurred in 1.1% (Grade 1/2).

Experts see iza-bren as a potential first-in-class dual-targeting ADC that could become a new standard of care across breast cancer subtypes and possibly beyond.

Iza-bren is a dual-targeting EGFR×HER3 bispecific antibody-drug conjugate delivering a Topo1i payload, designed to block EGFR and HER3 signaling and induce cancer cell death via internalization of the ADC.

Iza-bren has shown clinical benefit in five Phase 3 trials across five indications, including HR+/HER2- breast cancer, EGFR-mutated NSCLC, nasopharyngeal carcinoma, esophageal squamous cell carcinoma, and advanced TNBC; it has FDA Breakthrough Therapy Designation for previously treated advanced EGFR-mutated NSCLC.

Confirmed objective response rate was 40.5% for iza-bren versus 20.2% for chemotherapy, with median duration of response of 6.9 months versus 4.2 months (BICR).