Ligand-Induced Degradation of a CAR Permits Reversible Remote Control of CAR T Cell Activity In Vitro and In Vivo

Chimeric antigen receptor (CAR)-modified T cells are endowed with novel antigen specificity and are most often administered to patients without an engineered mechanism to control the CAR T cells once infused. “Suicide switches” such as the small molecule-controlled, inducible caspase-9 (iCas9) syste...

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Bibliographic Details
Published in:Molecular therapy 2020-07, Vol.28 (7), p.1600-1613
Main Authors: Richman, Sarah A., Wang, Liang-Chuan, Moon, Edmund K., Khire, Uday R., Albelda, Steven M., Milone, Michael C.
Format: Article
Language:English
Subjects:
engineered cell therapy, CAR T cells, proteasomal degradation, synthetic biology
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Summary:Chimeric antigen receptor (CAR)-modified T cells are endowed with novel antigen specificity and are most often administered to patients without an engineered mechanism to control the CAR T cells once infused. “Suicide switches” such as the small molecule-controlled, inducible caspase-9 (iCas9) system afford the ability to selectively eliminate engineered T cells; however, these approaches are designed for all-or-none, irreversible termination of an ongoing immune response. In order to permit reversible and adjustable modulation, we have created a CAR that is capable of on-demand downregulation by fusing the CAR to a previously developed ligand-induced degradation (LID) domain. Addition of a small molecule ligand triggers exposure of a cryptic degron within the LID domain, resulting in proteasomal degradation of the CAR-LID fusion protein and loss of CAR on the surface of T cells. This fusion construct allowed for reversible and “tunable” inhibition of CAR T cell activity in vitro. Delivery of the triggering molecule in CAR-LID-treated tumor-bearing mice temporarily reduced CAR activity through modulation of CAR surface expression. The ability to more flexibly modulate CAR T cell expression through a small molecule provides a platform for controlling possible adverse side effects, as well as preclinical investigations of CAR T cell biology. [Display omitted] To enable remote control over CAR T cell activity, Richman et al. incorporated a ligand-induced degradation (LID) domain into the CAR. This system created a reversible off switch, depending on the presence or absence of a small molecule ligand, permitting CAR T cell regulation in vitro and in vivo.
ISSN:1525-0016
1525-0024
DOI:10.1016/j.ymthe.2020.06.004