PANKU-Breast01 trial

Background

Randomised, open-label, multicentre phase 3, 72 hospitals in China. N=383 treated (all female, Chinese). HR+/HER2- breast cancer progressing after endocrine therapy, CDK4/6 inhibitor and 1-2 lines of chemotherapy. Iza-bren is a bispecific EGFR x HER3 ADC.

Results

Interventions and follow up: Arm A: iza-bren 2.5 mg/kg IV D1 and D8 q3w (n=190)
Arm B: physician's choice chemotherapy: eribulin, vinorelbine, gemcitabine or capecitabine (n=193)
Primary endpoint: PFS by BICR (RECIST 1.1, mITT)
mFollow up: 15.2 mo (95% CI 13.9-16.8) for PFS
Results: PFS (BICR): 8.2 mo (95% CI 6.9-8.6) vs 4.0 mo (2.9-4.3), HR 0.41 (95% CI 0.33-0.53), P<.0001
OS: immature, benefit not established

Adverse events

Grade ≥3 TRAE: 85% vs 66%, mainly hematologic
Supportive measures (iza-bren arm): platelet-elevating agents 73%, platelet transfusion 15%, blood transfusion 10%
Treatment-related deaths: 2 vs NR

Conclusions

Iza-bren significantly prolonged PFS vs chemotherapy in heavily pretreated HR+/HER2- breast cancer, but with substantial hematologic toxicity and no demonstrated OS benefit yet.

Key Limitations

Open-label; China-only population; OS immature; high grade ≥3 toxicity needing frequent platelet support; comparator chemotherapy options heterogeneous and does not include TROP2 ADCs; authors call for global and earlier-line evaluation.

Clinical Context

Heavily pretreated HR+/HER2- disease currently relies on sequential chemotherapy and ADCs. This trial uses single-agent chemotherapy as comparator, not a TROP2 ADC; regulatory status not stated in the publication.

References