CTLA4 and cancer: Immune checkpoint inhibitors (ICIs) are a class of medications (monoclonal antibodies) that block the binding of immune checkpoint proteins (e.g., CTLA-4, PD-1, and LAG-3) on T-cells with their partner proteins (e.g., PD-L1) on cancer or antigen-presenting cells, preventing a downregulation in the activity of T-cells and increasing their cancer killing activity [1].