PDCD1 and cancer: Hollow Fe3O4-NPs develop by loading BMS-202, a small molecule PD-1/PD-L1 inhibitor and pH-sensitive sodium bicarbonate (NaHCO3) into their inner cavity and then encapsulating it with MΦM to form biomimetic nano-systems (FBN@M) that target the tumor site based on MΦM innate inflammation directed chemotaxis, transform TME from immunosuppression to immunostimulant, and effectively block the PD-1/PD-L1 pathway to strengthen cancer immunotherapy 52.