A Phase II Study of Adjuvant Immunotherapy Targeting KRAS G12D, KRAS G12V, or TP53 R175H for Participants With Advanced Gastrointestinal Malignancies

Background: Gastrointestinal (GI) cancer affects the organs (such as the stomach, large and small intestine, pancreas, colon, liver, and biliary system) of the digestive tract. In some participants who have had surgery for GI cancer, blood tests show that the cancer has spread despite being unable to be identified by scans. Certain gene mutations (changes) in GI cancer (such as KRAS or TP53) can be targeted by T cells, a type of immune cell, in individuals with specific HLA types (genes that help proteins in the body know what is self and non-self). Researchers want to see if they can stop GI cancer from returning or spreading in people with these gene mutations and specific HLA types. Objective: To test therapy with modified T-cells to prevent or delay the return of GI cancer after standard treatment. T-cells play a role in the body s immune system. Eligibility: People aged 18 to 72 years with GI cancer that was treated with standard therapy and is not seen on imaging scans. They must have specific gene mutations and HLA types. They also must have certain clinical or blood tests showing the cancer is spreading (elevating CA19-9 or detectable ctDNA). Design: Participants will be divided into 2 groups. Participants nor the study team can choose what Group to participate in; this is done by randomization , like flipping a coin. Participants will have a 1-to-1 chance of being in Group 1 or Group 2. Group 1 will receive T-cell therapy. Their own T-cells will be collected. In a lab, the cells will be combined with a virus that carries a protein to target cancer cells. Group 1 participants will stay in the hospital for 3 weeks or more. They will have chemotherapy, and their modified T-cells will be infused through a tube attached to a needle inserted into a vein. Group 1 participants will visit the clinic every 3 months for 1 year and then every 6 months for 5 years. Then they will have follow-up visits for another 10 years under a different protocol. Group 2 participants will not receive treatment with T-cells. They will visit the clinic every 3 months for 1 year and then every 6 months for 5 years.