Perioperative MVT-5873, a Fully Human Monoclonal Antibody Against a CA 19-9 Epitope, for Operable CA 19-9 Producing Pancreatic Cancers, Cholangiocarcinomas, and Metastatic Colorectal Cancers

Background: Gastrointestinal tumors have a molecule called carbohydrate antigen 19-9 (CA19-9) in the tumors and blood. The agent MVT-5873 was designed to block this molecule. Researchers want to test how safe it is to give this agent to people before and after surgery to remove a tumor. They want to learn the highest dose tolerated. They want to see if getting the agent at surgery helps slow down the disease. Objective: To test the safety of giving MVT-5873 at surgery to remove cancer and see if it slows the progression of the disease. Eligibility: Adults at least 18 years old with certain cancers and certain blood CA19-9 levels Design: Participants will be screened with: * Medical history * Physical exam * Blood and heart tests * Scans * Review of normal activities * Review of tumor sample * Pregnancy test A few days before surgery, participants will get a dose of the study agent. They will get it through a small plastic tube in a vein over about 2 hours. Participants will sign a separate consent and have the surgery. A sample of the tumor and normal liver will be removed for research. For 1-2 weeks after surgery, participants will recover in intensive care then regular care at the hospital. They will be monitored and treated throughout the stay. After leaving the hospital, participants will get the study agent every week for 1 month. Then they will get it every other week for 2 months. They will repeat screening tests at study visits and at a follow-up visit. That will be about 5 weeks after the last dose.