This study is for people with a type of cancer called biliary tract cancer (BTC), which affects the tubes that carry bile from the liver. The study will test a new treatment called Zanidatamab combined with common cancer drugs Cisplatin and Gemcitabine. Some participants may also receive another drug like Durvalumab or Pembrolizumab, which help the immune system fight cancer. To join, your cancer must be HER2-positive, meaning it has a protein that makes the cancer grow. You should not have had more than two rounds of certain cancer treatments before. You need to be at least 18, have good organ function, and if you're able to have kids, use birth control.

• Study involves multiple visits for treatment and check-ups.
• Participants may receive Zanidatamab, Cisplatin, Gemcitabine, and possibly Durvalumab or Pembrolizumab.
• There might be risks, including side effects from the drugs.