pembrolizumab + pemetrexed + gemcitabine + cisplatin + carboplatin

This is a combination regimen consisting of five antineoplastic agents: - **Pembrolizumab** is a monoclonal antibody that targets the programmed cell death protein 1 (PD-1) receptor, acting as an immune checkpoint inhibitor to enhance anti-tumor immune responses. - **Pemetrexed** is an antifolate chemotherapy agent that inhibits multiple folate-dependent enzymes involved in nucleotide synthesis, thereby disrupting DNA and RNA synthesis in rapidly dividing cells. - **Gemcitabine** is a nucleoside analog that inhibits DNA synthesis by incorporation into DNA and inhibition of ribonucleotide reductase. - **Cisplatin** and **Carboplatin** are platinum-based chemotherapeutic agents that form DNA crosslinks, leading to apoptosis in cancer cells. This specific five-drug combination does not have regulatory approval as a single regimen but includes components used together or separately for the treatment of various cancers such as non-small cell lung cancer (NSCLC), biliary tract cancer, and others. Pembrolizumab plus pemetrexed with either cisplatin or carboplatin is approved for metastatic non-squamous NSCLC; pembrolizumab plus gemcitabine and cisplatin is approved for advanced biliary tract cancer[1][2][4][5][9]. The use of all five drugs together would be investigational.