CTLA4 and melanoma: Using the solid B16-OVA melanoma tumor model, we have previously demonstrated a synergy between MS–OVA (enc) and CPI therapy (anti-PD-1, anti-programmed death-ligand 1 (anti-PD-L1) and anti-CTLA-4) in promoting long-term tumor-free survival in C57BL/6 mice [15].