cisplatin + irinotecan + oxaliplatin + pemetrexed

This is a combination chemotherapy regimen consisting of four cytotoxic agents: cisplatin, irinotecan, oxaliplatin, and pemetrexed. Each drug has a distinct mechanism of action targeting cancer cell proliferation and survival: - **Cisplatin** is a platinum-based compound that forms DNA crosslinks, leading to apoptosis in rapidly dividing cells. - **Irinotecan** is a topoisomerase I inhibitor that prevents DNA unwinding and replication. - **Oxaliplatin** is another platinum-based agent that induces DNA crosslinking and inhibits DNA synthesis. - **Pemetrexed** is an antifolate antineoplastic agent that inhibits multiple folate-dependent enzymes involved in the synthesis of nucleotides required for DNA replication. These drugs are individually approved for various solid tumors (notably lung cancers), but there are no standard regimens or clinical trial data supporting the use of all four together as a single combination therapy. Each component has established efficacy in certain cancers—cisplatin/irinotecan combinations are used for small-cell lung cancer[1][2][3][4], while pemetrexed (often with cisplatin) is used for non-small cell lung cancer and mesothelioma[5][6][7][8]. The rationale behind combining these agents would be to exploit their complementary mechanisms to maximize tumor cell kill; however, such multi-agent regimens may also increase toxicity.