A Study of ZW25 (Zanidatamab) in Subjects With Advanced or Metastatic HER2-Amplified Biliary Tract Cancers

Inclusion Criteria: * Histologically- or cytologically-confirmed BTC, including ICC, ECC or GBC. * Locally advanced or metastatic BTC and not eligible for curative resection, transplantation, or ablative therapies. * Received at least 1 prior gemcitabine-containing systemic chemotherapy regimen for advanced disease, and experienced disease progression after or developed intolerance to the most recent prior therapy. For subjects who received gemcitabine in prior adjuvant or neoadjuvant treatment, if progression occurred \< 6 months from the latter of primary surgical resection or completion of gemcitabine-containing adjuvant therapy, they will be considered as having received 1 prior line of therapy for advanced disease. * Subjects must test positive for HER2 amplification by ISH-assay at a central laboratory on a new biopsy or archival tissue. Note that fine needle aspirates (FNAs; cytology samples) and biopsies from sites of bone metastases are not acceptable. Testing may occur at any time after diagnosis of advanced or metastatic disease and before study enrollment. * Male or female, ≥18 years of age (or the legal age of adulthood per country-specific regulations). * Eastern Cooperative Oncology Group (ECOG) performance status ≤ 1. * Adequate organ function. * Adequate cardiac function, as defined by left ventricular ejection fraction ≥ 50%. Exclusion Criteria: * Received systemic anti-cancer therapy within 3 weeks of the first dose of ZW25. Received radiotherapy within …