Regorafenib and Pembrolizumab in Treating Participants With Advanced or Metastatic Colorectal Cancer

This phase I/II studies the side effects and best dose of regorafenib when given together with pembrolizumab in treating participants with colorectal cancer that has spread to other places in the body. Drugs used in chemotherapy, such as regorafenib, work in different ways to stop the growth of tumor cells, either by killing the cells, by stopping them from dividing, or by stopping them from spreading. Monoclonal antibodies, such as pembrolizumab, may interfere with the ability of tumor cells to grow and spread. Giving regorafenib and pembrolizumab may work better at treating colorectal cancer.