Izalontamab brengitecan breast cancer: 59% lower risk of progression
October 27, 2026
Izalontamab brengitecan breast cancer data from the phase 3 PANKU-Breast01 study show a 59% reduction in the risk of disease progression or death compared with chemotherapy. The interim analysis was reported by Sichuan Biokin Pharmaceutical, Ltd. (Biokin), the sponsor in mainland China. The data are a late-breaking oral at ESMO 2026 in Madrid and appear simultaneously in The Lancet.
Izalontamab brengitecan breast cancer trial results
Iza-bren is a potentially first-in-class, dual-targeting EGFRxHER3 bispecific antibody-drug conjugate (ADC). The trial enrolled patients with unresectable, locally advanced, recurrent or metastatic HR-positive, HER2-negative breast cancer who had failed at least one prior line of chemotherapy: 190 received iza-bren and 193 received chemotherapy. Median progression-free survival (PFS) by Blinded Independent Central Review (BICR) was 8.2 months with iza-bren versus 4.0 months with chemotherapy, at a median follow-up for PFS of 15.2 months (HR: 0.41; 95% CI: 0.33-0.53, p<0.0001). Overall survival, a key secondary endpoint, was immature at the interim analysis.
Confirmed objective response rate by BICR was 40.5% with iza-bren versus 20.2% with chemotherapy, and median duration of response was 6.9 months versus 4.2 months. The safety profile was manageable, with no new safety signals. Grade ≥3 treatment-related adverse events were mostly hematologic, and 1.6% of patients discontinued iza-bren because of treatment-related adverse events. Adjudicated interstitial lung disease occurred in two patients (1.1%), all at Grade 1 or 2.
“The 59% reduction in progression or death we see with iza-bren represents a substantial advance for patients who have limited treatment options after prior chemotherapy,” said Dr. Jonathan Cheng, Chief Medical Officer of SystImmune.
Why it matters
Professor Binghe Xu said options “can become increasingly limited” as patients progress, “with most ultimately relying on chemotherapy.” For a reimbursement review, the PFS gain of 8.2 months versus 4.0 months would need to be read alongside overall survival, which is not yet mature. Outside China, SystImmune and Bristol Myers Squibb develop iza-bren jointly, and the release gives no dates for regulatory submissions or decisions.
Source: Bristol Myers Squibb and SystImmune press release (Business Wire)
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