cyclophosphamide + folinic acid + methotrexate + tegafur

This drug is a combination chemotherapy regimen consisting of four agents: - Cyclophosphamide is an alkylating agent that interferes with DNA replication and transcription, leading to cell death. - Folinic acid (also known as leucovorin or calcium folinate) is not a chemotherapy drug itself but enhances the efficacy of fluoropyrimidines like 5-fluorouracil (5-FU) by stabilizing the binding of fluorodeoxyuridine monophosphate to thymidylate synthase, increasing cytotoxicity. It also reduces toxicity from high-dose methotrexate by rescuing normal cells. - Methotrexate is an antimetabolite and antifolate agent that inhibits dihydrofolate reductase, blocking tetrahydrofolate synthesis necessary for DNA and RNA synthesis, thus inhibiting cell proliferation. - Tegafur is a prodrug of 5-fluorouracil (5-FU), converted in the liver to active 5-FU which inhibits thymidylate synthase, disrupting DNA synthesis in cancer cells. This combination leverages multiple mechanisms targeting nucleotide synthesis and DNA function to treat various cancers including breast cancer and gastrointestinal cancers. The addition of folinic acid potentiates the effects of tegafur-derived 5-FU while mitigating some toxicities associated with methotrexate[1][2][4][8].