convertibleCARs: A chimeric antigen receptor system for flexible control of activity and antigen targeting

Abstract

We have developed a chimeric antigen receptor (CAR) platform that functions as a modular system to address limitations of traditional CAR therapies. An inert form of the human NKG2D extracellular domain (iNKG2D) was engineered as the ectodomain of the CAR to generate convertibleCAR TM-T cells. These cells were specifically directed to kill antigenexpressing target cells only in the presence of an activating bispecific adapter comprised of an iNKG2D-exclusive ULBP2-based ligand fused to an antigen-targeting antibody (MicAbody TM). Efficacy against Raji tumors in NSG mice was dependent upon doses of both a rituximab-based MicAbody and convertibleCAR-T cells. We have also demonstrated that the exclusive ligand-receptor partnering enabled the targeted delivery of a mutant form of IL-2 to selectively promote the expansion of convertibleCAR-T cells in vitro and in vivo. By altering the Fv domains of the MicAbody or the payload fused to the orthogonal ligand, con-vertibleCAR-T cells can be readily targeted or regulated.

CAR T Cell Therapy for Solid Tumors: Bright Future or Dark Reality?

“…Examples include (1) avidin-CARs/biotin-labeled scFvs, (2) CD16-CAR/mAbs, (3) anti-fluorescein isothiocyanate (FITC)-CARs/FITC-labeled scFvs, (4) coiledcoil CARs (SUPRA CARs), (5) anti-PNE-CARs/PNE-scFvs, and (6) NKG2D-CARs/ULBP2-mAbs. [153][154][155][156][157][158][159] Lastly, bispecific T cell engagers (BiTEs) have been expressed in T cells, 160,161 and more recently adapted to CAR T cells, opening up the opportunity to target multiple antigens and redirecting bystander T cells to tumor cells. 162 In addition to designing CAR T cells to target multiple antigens, strategies are being pursued to engineer T cells to activate bystander T cells to recognize tumor cells (aka induce antigen/epitope spreading).…”

Modular Chimeric Antigen Receptor Systems for Universal CAR T Cell Retargeting

“…This modular CAR T cell variant, termed convertible CAR T cells, uses an inert form of the NKG2D extracellular domain as the ectodomain of the CAR [ 30 ] ( Figure 2 E). NKG2D, an activating receptor expressed on NK cells and some myeloid and T cells, was mutated in its ectodomain such that it cannot engage naturally occurring ligands.…”

Leveraging Immunotherapy with Nanomedicine

“…[175][176][177] 7) Finally, immune cells receptors can be genetically engineered to provide an exclusive orthogonal ligand-receptor interaction. [181,182] vivo shear stress exposure in the systemic circulation or endothelial diapedesis. More specific and robust interactions have thus been designed.…”

“…Thus, stable and controlled cell-NPs interactions have been sought. Immune cells naturally express receptors at their surface which can be genetically engineered to provide an exclusive orthogonal ligand-receptor interaction [181] ( Figure 3B). NK cells, T cells, and some macrophages present the NKG2D receptors on their surfaces that recognize the MHC class I polypeptide-related sequences (MIC) ligands family overexpressed on cells stressed by viral infection or cancer transformation.…”

“…Leveraging the natural 1− 2 binding domain of these ligands through protein engineering allows to develop an exclusive orthogonal ligandreceptor interaction to generate the components of a universal CAR T cell platform. [181] The engineered extracellular domain of the inert NKG2D receptors (iNKG2D) is fused to the intracellular 4-1BB and CD3 co-signaling domains to generate the CAR while the mutant ligand domains that specifically bind to the iNKG2D are fused to intact human antibodies. Up to now, efficacy of rituximab-based convertible CAR T cells has been investigated in NSG (NOD scid gamma) mice bearing Burkitt lymphoma and demonstrated dose-dependent control of tumor mass.…”