Gemcitabine, Cisplatin, Nab-paclitaxel (GAP) and Cemiplimab for Locally Advanced Biliary Tract Cancer (BTC)

The purpose of this study is to combine chemotherapy that has previously been shown to have activity in patients with biliary tract cancer with a drug that stimulates the body's immune system against cancer cells (immunotherapy). Previously, the combination of gemcitabine and cisplatin with immunotherapy has been shown to prolong life in patients with advanced biliary tract cancer. Adding nab-paclitaxel, another chemotherapy, to gemcitabine and cisplatin, has also been shown to prolong life in some patients with advanced biliary tract cancer. However, all four of these drugs have not before been combined. Cemiplimab is being used in an investigational manner (not for the purpose that it was approved for) in this research study. This means that cemiplimab has been approved by the Food and Drug Administration (FDA) for use in advanced or metastatic cutaneous squamous cell carcinoma, basal cell carcinoma, and non-small cell lung cancer, but has not been approved for locally advanced biliary tract cancer that cannot be surgically removed. Since surgery is the only way to potentially cure this cancer, new treatments are needed that can shrink inoperable tumors enough to make surgery possible. This is especially important for patients with advanced biliary tract cancer that hasn't spread to other parts of the body.