Reversing T Cell Dysfunction to Boost Glioblastoma Immunotherapy by Paroxetine-Mediated GRK2 Inhibition and Blockade of Multiple Checkpoints through Biomimetic Nanoparticles

T cell dysfunction-induced tumor immune escape is particularly severe in glioblastoma (GBM), and significantly affects the efficacy of immunotherapy. It is crucial to innovatively reverse the T cell dysfunction for improving GBM immunotherapy. Herein, T cell dysfunction is remarkably reversed and immunotherapy of GBM is boosted by repurposing the U. S. Food and Drug Administration-approved antidepressant paroxetine (PX) with biomimetic nanoparticles (CS-J@CM/6 NPs). The PX is successfully applied to abrogate T cell sequestration in the bone marrow of GBM-bearing mice and increase their infiltration in tumor. The biomimetic NPs are composed of ultrasmall Cu_{2- x} Se NPs, JQ1, and tumor cell membrane modified with CD6, and are efficiently delivered into tumor through the specific interactions between CD6 and activated leukocyte cell adhesion molecule. They ameliorate the T cell dysfunction through the double roles of loaded JQ1, which simultaneously decreases the expression of PD-1 and TIM-3 on T cells, and the expression of PD-L1 on tumor cells. The NP also induces the immunogenic cell death of tumor cells to activate immune response. The synergistic roles of PX and biomimetic CS-J@CM/6 NPs notably enhance the survival of GBM-bearing mice. This work provides new insights into tumor immunotherapy by repurposing "old drugs" with advanced NPs.