Cytolytic Activity of CAR T Cells and Maintenance of Their CD4+ Subset Is Critical for Optimal Antitumor Activity in Preclinical Solid Tumor Models

Correlative studies of clinical for hematological malignancies have implicated that less differentiated, CD8+-dominant CAR T cell products greater antitumor activity. Here, we investigated whether the differentiation status affects their activity in preclinical models solid tumors. We explored if different activation/expansion protocols, as well co-stimulatory domains construct, influence short- and long-term efficacy cells against HER2-positive generated range from most differentiated (CD28.z; OKT3-antiCD28/RPMI expansion) to least (41BB.z; OKT3-RetroNectin/LymphoONE expansion), judged by surface expression markers CCR7 CD45RA. While effect was variable with regard antigen-specific cytokine production, CD28.z products, which were enriched effector memory cells, had greatest target-specific cytolytic vitro. These also a proliferative capacity maintained CD4+ upon repeated stimulation In vivo, activity, resulting complete response. Our results highlight it is critical optimize production optimal product characteristics might depend on targeted antigen and/or cancer.