Costimulatory domains direct distinct fates of CAR-drivenT cell dysfunction [RNA-seq]

Chimeric antigen receptor (CAR) engineered T cells often fail to enact effector functions after infusion into patients. Understanding the biological pathways that lead CAR T cells to failure is of critical importance in the design of more effective therapies. We developed and validated an in vitro model that drives T cell dysfunction by chronic CAR stimulation and interrogated how CAR costimulatory domains contribute to T cell failure. We found that dysfunctional CD28-based CARs targeting CD19 bear hallmarks of classical T cell exhaustion while dysfunctional 41BB-based CARs are phenotypically, transcriptionally and epigenetically distinct. We confirmed activation of this unique transcriptional program in CAR T cells that failed to control clinical disease. Further, we demonstrate that 41BB-dependent activation of the transcription factor FOXO3 is a significant contributor to this dysfunction and disruption of FOXO3 significantly improves 41BB-based CAR T cell function. These findings identify that chronic activation of 41BB leads to novel state of T cell dysfunction that can be alleviated by genetic modification of FOXO3. Overall design: Comparative gene expression profiling analysis of RNA-seq data for CD19-directed human CAR T cells with CD28 and 41BB during chronic activation by CD19+ ALL cell line Nalm6. T cells were collected from five different donors and each sample was sequenced in technical triplicate.