Structural design of engineered costimulation determines tumor rejection kinetics and persistence of CAR T cells

The choice of costimulatory domain in CAR design dictates the kinetics of in vivo anti-tumor responses, affecting potency, quality and durability. We show that 1928z results in more vigorous effector functions, whereas 19BBz design compensates for their lesser cytotoxic potency by steadily building up their numbers. Therapeutic function can be further improved by combining CD28 and 4-1BB costimulation. 1928z-41BBL was revealed to provide optimal combined costimulation, exhibiting highly therapeutic efficiency with balanced T cell effector function and accumulation. Endogenous IFN-β/IRF7 pathway activation was found in 1928z-41BBL T cell and is required for effector function acquisition. The role of the IFN-β/IRF7 pathway provides a novel mechanism through which engineering T cells improve therapeutic effect by self-providing ‘signal 3’. In order to understand the molecular mechanisms underlying the improved anti-tumor function induced by 1928z-41BBL, we performed genome wide gene expression profile of CD4 and CD8 1928z-41BBL CAR T cells and compared it to 19z1, 19z1-41BBL and 1928z, which represent the individual signaling modalities within the design.