Study of SMT-NK Inj. Plus Pembrolizumab vs Pembrolizumab Monotherapy in Patients With Advanced Biliary Tract Cancer

This study is comparing a combination treatment — SMT-NK (a type of natural killer cell therapy) plus pembrolizumab (immunotherapy) — against pembrolizumab alone in patients with advanced biliary tract cancer (cancers of the bile ducts or gallbladder) that has not responded to chemotherapy or where chemotherapy is too toxic. **You may be eligible if:** - You are between 19 and 80 years old - You have advanced biliary tract cancer (intrahepatic or extrahepatic cholangiocarcinoma, or gallbladder cancer) confirmed by biopsy - Your cancer has not responded to or you cannot tolerate chemotherapy - Your cancer is measurable on scans - Your general health is adequate (ECOG ≤2) - You are expected to survive at least 3 months **You may NOT be eligible if:** - You have a resectable tumor (surgery is still an option) - Your organ function (blood, kidneys, liver) does not meet the required minimums - You are not expected to survive 3 months or more Talk to your doctor to see if this trial is right for you.