Anti-HER2 Bispecific Antibody Zanidatamab (ZW25) Activity in Combination With Chemotherapy With/Without Tislelizumab

Inclusion Criteria

• •1. Disease diagnosis and prior treatment:
• •1. Cohort 1 (the first-line breast cancer treatment cohort):
• •* Female participants with histologically or cytologically confirmed unresectable, locally advanced, recurrent or metastatic adenocarcinoma of the breast and candidate for chemotherapy. Locally recurrent disease must not be amenable to resection with curative intent.
• •* Human epidermal growth factor receptor 2 (HER2) IHC 3+ or in situ hybridization positive on the archival tumor tissue or fresh biopsy sample.
• •* Have not received previous systemic anticancer therapy for locally advanced unresectable or metastatic disease.
• •2. Cohort 2 (the first-line gastric/gastroesophageal junction adenocarcinoma treatment cohort):
• •* Histologically or cytologically confirmed unresectable, locally advanced, recurrent or metastatic adenocarcinoma of the stomach or gastroesophageal junction
• •* HER2 IHC 3+ or HER2 IHC 2+ together with in situ hybridization positive on the archival tumor tissue or fresh biopsy sample.
• •* Have not received previous systemic anticancer therapy for locally advanced unresectable or metastatic disease, including any approved or investigational estimated glomerular filtration rate (EGFR) or anti-HER2 agents or vaccines, cytotoxic chemotherapy or checkpoint inhibitors
• •2. At least 1 measurable lesion as defined per RECIST Version 1.1
• •3. Eastern Cooperative Oncology Group (ECOG) Performance Status ≤ 1
• •4. Adequate organ function
• •5. Left ventricular ejection fraction (LVEF) ≥ 50% at baseline as determined by either echocardiogram or multigated acquisition scan (MUGA) (echocardiogram is the preferred method) within 28 days before the first dose of study drug