capecitabine + S-1

Capecitabine + S-1 is an investigational combination of two oral fluoropyrimidine prodrugs, both of which are metabolized to 5-fluorouracil (5-FU) in the body. Capecitabine is a carbamate derivative that is selectively activated in tumor tissue, while S-1 consists of tegafur (a prodrug of 5-FU), gimeracil (a dihydropyrimidine dehydrogenase inhibitor), and oteracil (which reduces gastrointestinal toxicity). Both drugs act as antimetabolites by interfering with DNA synthesis and inhibiting tumor cell proliferation. This combination has been explored for synergistic or additive effects in gastrointestinal cancers, but most clinical studies compare these agents rather than combine them directly[3][4][5]. The primary indications for each drug individually include gastric cancer, colorectal cancer, and other solid tumors.