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

Kyle E Landgraf,David W Martin,Steven R Williams,Dana Gebhart,Kaman Chan Kim,Kole T Roybal,Daniel Steiger,Stephen Lok

doi:10.1038/s42003-020-1021-2

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 convertibleCARTM-T cells. These cells were specifically directed to kill antigen-expressing 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 (MicAbodyTM). 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, convertibleCAR-T cells can be readily targeted or regulated.

Highlights

We have developed a chimeric antigen receptor (CAR) platform that functions as a modular system to address limitations of traditional chimeric antigen receptors (CARs) therapies
We have described the engineering of a privileged receptor-ligand pairing comprising human components b
After the contraction of T cells at 14 days, mice were injected with 30 μg ULBP2-S3 variant (U2S3)-hFc-mutations in IL-2 (mutIL2) or phosphatebuffered saline (PBS) once per week—indicated by red triangles—and T cell dynamics monitored by flow cytometry

Summary

Introduction

An inert form of the human NKG2D extracellular domain (iNKG2D) was engineered as the ectodomain of the CAR to generate convertibleCARTM-T cells These cells were 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 (MicAbodyTM). We have determined that U2S3 can be used as a means of addressing molecules for delivery to iNKG2Dexpressing cells and that this feature can target the iNKG2D-CAR cells for complement-mediated killing or drive their expansion in vitro and in vivo with a mutant cytokine fusion This highly modular convertibleCAR system leverages the body of information behind antibody discovery, development, and manufacturing and nimbly integrates it with the tremendous potential of adoptive cell therapies

Methods

Results

Conclusion