erlotinib + tegafur + gimeracil + oteracil

This is a combination of four small molecule drugs: erlotinib, an epidermal growth factor receptor (EGFR) tyrosine kinase inhibitor, and the fixed-dose oral fluoropyrimidine formulation tegafur/gimeracil/oteracil. Erlotinib inhibits EGFR signaling by reversibly binding to its ATP-binding site, blocking downstream pathways involved in cell proliferation and survival. Tegafur is a prodrug of 5-fluorouracil (5-FU), which inhibits thymidylate synthase, disrupting DNA synthesis in rapidly dividing cells. Gimeracil inhibits dihydropyrimidine dehydrogenase (DPD), increasing 5-FU bioavailability by preventing its breakdown. Oteracil reduces gastrointestinal toxicity by inhibiting phosphorylation of 5-FU in the gut[1][2][3][4][5]. This multi-agent regimen would be expected to provide dual antitumor activity through both targeted inhibition of EGFR signaling and cytotoxic effects on DNA synthesis.