CD274 and Patent ductus arteriosus: As opposed to the success experienced in other solid tumors, ICI has shown limited efficacy in advanced PDA, wherein single agent treatment with anti-CTLA4 (cytotoxic T-lymphocyte-associated protein 4) (2) and anti-PDL1 (Programmed death-ligand 1) (3, 4) achieved zero percent response, and combined treatment, less than five percent response (4).