This study is about giving a medicine called zanidatamab to patients who have a type of colon or rectal cancer. Their cancer is HER2 positive, meaning it has too much of a protein called HER2 that helps cancer grow. Zanidatamab is a monoclonal antibody, a special protein that can latch onto cancer cells and stop them from growing.

Before surgery, patients will receive zanidatamab through an intravenous (IV) line over 90-150 minutes. Patients will have cycles of treatment every 14 days, with colon cancer patients receiving up to 4 cycles and rectal cancer patients up to 12 cycles. After treatment, patients will have surgery or be observed, depending on their type of cancer.

• Participation involves multiple visits for IV treatment and tests like scans and blood samples.
• The study lasts up to 2 years, with follow-up visits every 12 weeks after treatment.
• Risks may include side effects from the medicine, which will be monitored closely.

Patients must be at least 18 years old and meet specific health criteria to join the study. After the study, participants are followed up at 30 days and then every 12 weeks for up to 2 years.