Mnox Nanoenzyme Armed CAR‐NK Cells Enhance Solid Tumor Immunotherapy by Alleviating the Immunosuppressive Microenvironment

Abstract Adoptively transferred cells usually suffer from exhaustion, limited expansion, and poor infiltration, partially attributing to the complicated immunosuppressive microenvironment of solid tumors. Therefore, it is necessary to explore more effective strategies to improve the poor tumor microenvironment (TME) to efficaciously deliver and support extrinsic effector cells in vivo. Herein, an intelligent biodegradable hollow manganese dioxide nanoparticle (MnO X ) that possesses peroxidase activity to catalyze excess H 2 O 2 in the TME to produce oxygen and relieve the hypoxia of solid tumors is developed. MnO X nanoenzymes modified with CD56 antibody could specifically bind CAR‐NK (chimeric antigen receptor modified natural killer) cells. It is demonstrated that CAR‐NK cells incorporated with MnO X nanoenzymes effectively infiltrate into tumor tissues with an improved TME, which results in superior antitumor activity in solid tumor‐bearing mice. The antibody connection between MnO X nanoenzymes and CAR‐NK endows the lowest efficient dosage of MnO X . This study features a smart synergistic immunotherapy approach for solid tumors using MnO X nanoenzyme‐armed CAR‐NK cells, which would provide a valuable tool for immunocyte therapy in solid tumors.