In Vivo Monitoring and Magnetically‐Enhanced Delivery of CAR T‐Cells to Solid Tumor

Abstract Chimeric antigen receptor (CAR) T‐cell therapy demonstrates efficacy for the treatment of hematologic cancers, but remains challenging in solid tumors because of the hostile tumor microenvironment and heterogeneity that restrict the infiltration and activity of CAR T‐cells. The lack of clinical imaging methods to monitor CAR T‐cell therapy in patients limits the potential to enhance the therapeutic approach and predict patient response. Here, a straightforward, non‐invasive method for Magnetic Resonance Imaging (MRI) tracking and magnetic targeting of CAR T‐cells to enhance T‐cell trafficking to solid tumors, in a setting that can be deployed in clinics, is reported. Iron oxide nanoparticles are loaded into T‐cells, allowing MRI detection and magnetic cell guidance, while preserving T‐cell viability, functions, and CAR specificity to target epidermal growth factor receptor (EGFR)‐expressing tumors. Longitudinal MRI monitoring of T‐cells over 14 days reveals differences in tumor infiltration rates and antitumor efficacy between EGFR‐targeted CAR T‐cells and non‐transduced T‐cell. Moreover, an external magnet placed over the tumor enhances the infiltration of CAR T‐cells and increases their antitumor effect. MRI monitoring and magnetic guidance represent a dual‐pronged clinically feasible therapeutic strategy to control and promote CAR T‐cells delivery into solid tumors, thereby improving the precision, efficacy, and safety of the treatment.