Regulated Expansion and Survival of Chimeric Antigen Receptor-Modified T Cells Using Small Molecule-Dependent Inducible MyD88/CD40

Abstract

Anti-tumor efficacy of T cells engineered to express chimeric antigen receptors (CARs) is dependent on their specificity, survival, and in vivo expansion following adoptive transfer. Toll-like receptor (TLR) and CD40 signaling in T cells can improve persistence and drive proliferation of antigen-specific CD4 and CD8 T cells following pathogen challenge or in graft-versus-host disease (GvHD) settings, suggesting that these costimulatory pathways may be co-opted to improve CAR-T cell persistence and function. Here, we present a novel strategy to activate TLR and CD40 signaling in human T cells using inducible MyD88/CD40 (iMC), which can be triggered in vivo via the synthetic dimerizing ligand, rimiducid, to provide potent costimulation to CAR-modified T cells. Importantly, the concurrent activation of iMC (with rimiducid) and CAR (by antigen recognition) is required for interleukin (IL)-2 production and robust CAR-T cell expansion and may provide a user-controlled mechanism to amplify CAR-T cell levels in vivo and augment anti-tumor efficacy.

Sensitive and adaptable pharmacological control of CAR T cells through extracellular receptor dimerization

“…Several other regulatable CAR approaches have been described, including variants that have dimerizable subunits and systems using universal adapter CARs (22,24,32,38). Lim and colleagues designed a system that also uses the FKBP12 and FRB components to regulate CAR activity (22).…”

Programming CAR-T cells to kill cancer

“…In this context, a small molecule that brings together the ζ -chain and CAR to modulate CAR activation (Fig. 3a) 76 and another similar model involving a MyD88/CD40 inducible costimulatory molecule 49,77 have been reported.…”

Adoptive Cell Therapy—Harnessing Antigen-Specific T Cells to Target Solid Tumours

“…Using distinct co-stimulatory molecules for CD4+ and CD8+ T cell subsets (i.e., CD4.ICOS-CAR T cells and CD8.41BB-CAR T cells) [33] Addition of a second, independent co-stimulatory molecule, i.e., 4-1BB ligand, CD40L [34,35] Addition of inducible MyD88/CD40 (iMC), to activate downstream toll-like receptor (TLR) and CD40 signalling pathways using a small molecule ligand, rimiducid [36,37] Constitutive expression of a cytokine that is bound to cell membrane of CAR T cell or secreted by the cell, i.e., interleukin (IL) 15, IL-12 [38][39][40] Constitutive activation of intracellular IL-7 cytokine receptor triggering IL-7 axis without stimulating bystander lymphocytes [41] Limited tumour specificity and off-target effects…”