gemcitabine + oxaliplatin + tislelizumab + regorafenib

This is a combination regimen consisting of four drugs: **gemcitabine** (a nucleoside analog chemotherapy), **oxaliplatin** (a platinum-based chemotherapy), **tislelizumab** (a monoclonal antibody targeting PD-1 immune checkpoint), and **regorafenib** (a small molecule multikinase inhibitor). This combination aims to synergistically enhance antitumor efficacy by combining cytotoxic chemotherapy (gemcitabine, oxaliplatin), immune checkpoint blockade (tislelizumab), and angiogenesis/kinase inhibition (regorafenib). Clinical studies have explored similar combinations for aggressive cancers such as advanced or metastatic biliary tract cancer (BTC), aiming to improve response rates and survival outcomes. The regimen has shown promising efficacy and manageable toxicities in studies of related triplet and quadruplet combinations, though data specifically on all four together are emerging.