Structural Design of Engineered Costimulation Determines Tumor Rejection Kinetics and Persistence of CAR T Cells

Abstract

Summary T cell engineering is a powerful means to rapidly generate anti-tumor T cells. The costimulatory properties of second-generation chimeric antigen receptors (CARs) determine the overall potency of adoptively transferred T cells. Utilizing an in vivo “stress test” to challenge CD19-targeted T cells, we studied the functionality and persistence imparted by 7 different CAR structures providing CD28 and/or 4-1BB costimulation. One configuration, which utilizes two signaling domains (CD28 and CD3ζ) and the 4-1BB ligand, provided the highest therapeutic efficacy, showing balanced tumoricidal function and increased T cell persistence accompanied by an elevated CD8/CD4 ratio and decreased exhaustion. Remarkably, induction of the IRF7/IFNβ pathway was required for optimal anti-tumor activity. Thus, 1928z-41BBL T cells possess strikingly potent intrinsic and immunomodulatory qualities.

Enhancing CAR T cell persistence through ICOS and 4-1BB costimulation

“…Initial attempts to increase T cell persistence in vivo with third-generation CARs have focused primarily on combined CD28 and 4-1BB signaling. Using a different strategy, Zhao et al examined the effects of using actual ligands for different costimulatory receptors to identify the optimal combination of signals to support the persistence and function of engineered CD19 CAR T cells (47). Here, we found that combination of ICOS and 4-1BB in a third-generation CAR showed enhanced antitumor effects and synergistic effects on T cell in vivo survival but only when ICOS is placed proximal to the membrane.…”

Blockade of CD7 expression in T cells for effective chimeric antigen receptor targeting of T-cell malignancies

“…43 To this end, a recent study reported an anti-CD7 CAR that was expressed in T cells with CD7 gene deletion by CRISPR/Cas9. 44 Besides differences in costimulatory molecules (our CAR has 4-1BB instead of CD28), which may have clinical impact, 45,46 the high specificity and practical nature of the PEBL strategy make it particularly attractive for current clinical use. This method requires a simple transduction with the same viral vector carrying the CAR, either as 2 sequential transductions or a single transduction with a bicistronic vector carrying both constructs.…”

A Multifunctional Role for Adjuvant Anti-4-1BB Therapy in Augmenting Antitumor Response by Chimeric Antigen Receptor T Cells

“…Another interesting approach to provide 4-1BB costimulation has involved the overexpression of the 4-1BB ligand (4-1BBL) on the surface of CD3z-CD28 CAR T cells targeting the CD19 antigen (39). Data from this study indicated that CD28 contained within the CAR construct was a strong driver of the antitumor response.…”

“…Data from this study indicated that CD28 contained within the CAR construct was a strong driver of the antitumor response. In contrast, 4-1BB signaling was more effectively delivered following coexpression of 4-1BBL and the CD3z-CD28 CAR compared with 4-1BB signaling provided through a third-generation CD3z-4-1BB-CD28 CAR, owing to its ability to provide trans-costimulation to other T cells and potentially recruit host immune cells (39). This supports our hypothesis that unlike having the 4-1BB domain incorporated into the CAR, exogenous a-4-1BB mAb may additionally provide stimulation to not only the host endogenous T cells, but also other 4-1BB-expressing cells, such as NK cells, DCs, and neutrophils (12), potentially resulting in a multipronged immune attack against the tumor.…”