PDCD1 and neoplasm: 1-Methyl-DL-tryptophan (1-MT, an indoleamine 2,3-dioxygenase (IDO, an immunosuppressive enzyme) inhibitor) was covalently conjugated with hyaluronic acid to form an amphiphilic structure (m-HA), which self-assembled into nanoparticles and encapsulated antibodies (aPD1, anti-programmed cell death protein 1 (PD1, an immunosuppressive receptor on tumor lymphocytes)).