Safety and antitumor activity of the first-in-class EGFR-HER3 bispecific antibody-drug conjugate iza-bren (BL-B01D1) in patients with pretreated locally advanced or metastatic breast cancer: a phase Ib study.

Iza-bren (BL-B01D1) showed clinically meaningful antitumor activity in heavily pretreated metastatic breast cancer, with confirmed objective response rates of 46.3% in HER2-positive patients.

• Why it matters: Monospecific ADCs can be limited, so a bispecific ADC approach is needed to improve outcomes for patients with locally advanced or metastatic breast cancer after multiple prior therapies.
• What they did: In a multicenter phase Ib study, pretreated patients were assigned to HER2-positive (n = 41), HR-positive/HER2-negative (n = 75), or TNBC (n = 46) and received iza-bren 2.5 mg/kg i.v. on days 1 and 8 every 21-day cycle. Safety was the primary endpoint.
• The result: Treatment-related adverse events occurred in 99.4% of patients, with grade ≥3 events in 77.8% and mainly hematological toxicities (neutropenia 55.6%, anemia 42.0%); two treatment-related deaths occurred, and no interstitial lung disease was reported.

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