GEN-001 Plus Pembrolizumab for Patients With Advanced Refractory Biliary Tract Cancer

Inclusion Criteria: * The patient (or legally acceptable representative if applicable) provides written informed consent for the trial. * Be ≥19 years of age on day of signing informed consent. * Patient with histologically or cytologically confirmed diagnosis of unresectable, recurrent, or metastatic advanced biliary tract adenocarcinoma of the gallbladder or biliary tree (either intrahepatic or extrahepatic cholangiocarcinoma) Exclusion Criteria: * A WOCBP who has a positive urine pregnancy test (within 72 hours) prior to treatment. If the urine test is positive or cannot be confirmed as negative, a serum pregnancy test will be required. * Has received prior therapy with an anti-PD-1, anti-PD-L1, or anti-PD-L2 agent or with an agent directed to another stimulatory or co-inhibitory T-cell receptor (Cohort 1 only), and was discontinued from the previous IO therapy due to a Grade 3 or higher immune-related AE (irAE) (Cohort 2 and Cohort 3). * Is currently participating and receiving study treatments or has participated in a study of an investigational agent and received the study therapy or has used an investigational device within 4 weeks prior to the first dose of study treatment. * Has had an allogeneic tissue/solid organ transplan