CTLA4 and melanoma: Antibodies targeting PDL1 (Programmed death-ligand 1) and CTLA4 (Cytotoxic T-Lymphocyte Associated Protein 4) are important checkpoint inhibitors enhancing T cell killing of tumor cells, making them efficacious treatments in many solid tumors, such as lung cancer, melanoma, renal carcinoma, and others, while some types of solid tumors are resistant to immunotherapy.