Testing the Addition of an Anti-Cancer Drug, ZEN003694, to the Usual Chemotherapy Treatment (Capecitabine) for Metastatic or Unresectable Cancers

This phase I trial tests the safety, side effects, and best dose of ZEN003694 in combination with the usual treatment with capecitabine in treating patients with cancer that has spread from where it first started (primary site) to other places in the body (metastatic) or cannot be removed by surgery (unresectable) and that it has progressed on previous standard treatment. ZEN003694 is an inhibitor of a family of proteins called the bromodomain and extra-terminal (BET). It may prevent the growth of tumor cells that over produce BET protein. Capecitabine is in a class of medications called antimetabolites. It is taken up by cancer cells and breaks down into fluorouracil, a substance that kills cancer cells. Giving ZEN003694 in combination with capecitabine may be safe in treating patients with metastatic or unresectable solid tumors.