Beamion BCGC-1: phase Ib/II trial of zongertinib for advanced HER2-positive breast or gastroesophageal cancers

Background: Overexpression and/or amplification of human epidermal growth factor receptor 2 (HER2) is a recognized oncogenic driver in metastatic breast cancer (mBC) and metastatic gastric, gastroesophageal junction, or esophageal adenocarcinomas (mGEAC). Although HER2-directed monoclonal antibodies, antibody–drug conjugates (ADCs), and tyrosine kinase inhibitors (TKIs) have revolutionized the treatment of HER2-positive tumors, additional combination regimens and/or novel agents are needed to expand sequential therapy options and improve patient outcomes–particularly following treatment with trastuzumab deruxtecan (T-DXd). Zongertinib is a novel, irreversible, HER2-selective TKI that spares EGFR. Study design: Here, we detail the rationale and design of Beamion BCGC-1 (NCT06324357), an international Phase Ib/II open-label trial in which patients with previously treated HER2-positive mBC or mGEAC will receive zongertinib alone or in combination. Phase Ib (dose escalation) will determine the maximum tolerated dose of zongertinib plus trastuzumab emtansine (T-DM1), T-DXd, or trastuzumab ± capecitabine, in patients with HER2-positive mBC, and plus T-DXd in patients with HER2-positive mGEAC. Phase II (dose optimization) will assess two doses of zongertinib in combination regimens, or as monotherapy, in patients with mBC or mGEAC. The trial is actively recruiting in six countries globally. Clinical trial registration: www.clinicaltrials.gov identifier is NCT06324357.