CD4 depletion enhances the efficacy of Super2 IL-33 armored CAR T cell against solid tumors and leads memory formation of both endogenous and CAR T cells

Abstract Chimeric antigen receptor (CAR) T cells exhibit tremendous efficacy in patients with relapsed and recurrent liquid cancers. However, CAR T cells fail to control solid tumors because of their inability to infiltrate the suppressive tumor environment and their poor persistence in vivo. The development of 4 thgeneration armored CAR T cells that employ direct tumor killing and release cytokines that can modulate the immune response to enhance tissue/tumor infiltration may improve CAR T cell persistence. Our lab has developed Super2 and IL-33 (S233) armored CAR T cells that significantly delayed B16F10 melanoma tumor growth and enhanced tumor infiltration of CARs and endogenous immune cells. Combination therapy of S233 CAR T Cells with anti-CTLA4 or anti-CD4 further enhanced this phenotype. S233 CAR T cells and anti-CD4 combination therapy promoted Melanoma-associated vitiligo (MAV), which correlates with development of tumor protective Tissue Resident Memory (TRM) cells. To assess whether CAR T cells differentiate into memory T cells, we treated tumor-bearing mice with S233 CAR T Cells with or without anti-CD4, resected their residual tumors and tracked memory T cell responses. We found that S233 CAR T cells persisted longer in the tumor draining lymph node and developed accelerated MAV when combined with anti-CD4. Both CAR T cells and endogenous T cells differentiated into central and effector memory but only endogenous T cells in the CD4 depleted group became TRM cells. While these findings provide insights on strategies to enhance long-term persistence of CAR T cells, additional studies are needed to induce CAR TRM cells and assess the durability of anti-tumor responses. NIH grant T32-AI007363 NIH grant P30-CA023108