The most commonly targeted checkpoints in dual therapy are PD-1/PD-L1 and CTLA-4. PD-1 (Programmed Death-1) is found on T-cells, and its ligand PD-L1 is often expressed on tumor cells. CTLA-4 (Cytotoxic T-Lymphocyte Associated Protein 4) is another checkpoint protein that downregulates immune responses. Drugs like nivolumab and ipilimumab are examples of inhibitors for these checkpoints.
