A Phase 2 Neoadjuvant Study of Zanidatamab in Combination With Chemotherapy in Participants With HER2-positive Breast Cancer

Inclusion criteria

• Has newly diagnosed Stage II or III histologically confirmed invasive breast carcinoma.
• Has histologically confirmed HER2-positive breast cancer
• Has a known hormone receptor (HR) status of the primary tumor
• Participants with multifocal or multicentric disease are eligible if the largest tumor (which must be larger than or equal to 2 cm in diameter) is HER2-positive, and the treating physician has determined the participant should be treated as HER2-positive.
• Agrees to undergo a mastectomy or breast conserving surgery (BCS) after neoadjuvant therapy.
• Has an Eastern Cooperative Oncology Group (ECOG) performance status of 0 or 1.
• Adequate organ function
• Has an LVEF ≥ 50% as determined by either ECHO or MUGA obtained within 6 weeks prior to randomization.
• Adequate contraceptive precautions
• Participants with known HIV are eligible unless:
• CD4+ T Cell count is less than or equal to 350 microliters (uL)
• Detectable viral load, or
• Receiving protease inhibitors or cobicistat

Exclusion criteria

• Has Stage IV (metastatic) breast cancer.
• Has bilateral breast cancer.
• Has a history of any severe and/or uncontrolled medical conditions or other conditions that, in the opinion of the investigator, could affect the participant's involvement in the study.
• Has uncontrolled hypertension
• Has significant symptoms from peripheral neuropathy
• Has an active uncontrolled infection
• Has a history of life-threatening hypersensitivity to monoclonal antibodies or to recombinant proteins or excipients in the drug formulation of zanidatamab or other study interventions.
• Known active hepatitis B or C infection.
• Has another malignancy diagnosed within the last 5 years. Exceptions include previously treated non melanomatous skin cancers, carcinoma in-situ, and melanoma in-situ. Participants with prior ipsilateral ductal carcinoma in situ (DCIS) or invasive breast cancer are not eligible.
• Was treated with surgery, chemotherapy, anti-HER2 therapy, radiation therapy, endocrine therapy, or experimental therapy for invasive breast cancer
• Is planning to receive concurrent therapy with any other investigational agent or anti-cancer therapy not specified in the protocol
• Receipt of a live vaccine within 4 weeks prior to enrollment
• Has a known hypersensitivity to any components of the study interventions, including chemotherapy