Homology-Directed Repair-Developed TCR Therapy Shows Potential in Type 1 Diabetes

A homology-directed repair (HDR)-based approach has improved efficiency and modulation of T-cell receptor (TCR) therapies for the treatment of type 1 diabetes (T1D).

The novel approach was presented at the American Society for Gene and Cell Therapy 25th Annual Meeting, May 16-19, 2022, in Washington DC, by Martina S. Hunt, research scientist, Seattle Children's Hospital.

“Adoptive regulatory T-Cell (Treg) therapies represent a potentially transformative cell-based therapy to promote immune tolerance following stem cell or solid organ transplantation, and in autoimmune diseases including T1D. Key technical hurdles, however, may limit broad clinical application including the rarity of natural Treg, the requirement for antigen-specificity to modulate tissue-specific disorders, and requirement to compete in vivo for engraftment and survival,” Hunt and colleagues, including first author, Peter J. Cook, PhD, research scientist, Seattle Children's Hospital.

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The investigators developed an approach that simultaneously induces constitutive expression of FOXP3, a Treg master transcriptional regulator, with the MND promoter to stabilize Treg phenotype and function while replacing the endogenous TCR with a tissue-specific TCR. They also designed donor cassettes with a heterodimeric, chemically-induced signaling complex (CISC) to mimic IL-2 signaling in response to an exogenous dimerizer.

Hunt and colleagues used this approach to generate engineered Treg (EngTregs) products for the prevention and/or treatment of T1D with a TCR specific for the islet antigen IGRP. They observed initial FOXP3/TRAC dual-editing rates ranging from 2% to 15% in healthy donor derived CD4+ T cells with use of CRISPR-based tools. They confirmed positive selection for on-target editing events and negative selection for low-frequency chromosomal translocations following expansion and enrichment.

These cells continued to demonstrate a robust Treg immunophenotype after cryopreservation as well as a secretome switch from pro-inflammatory to immunosuppressive cytokines. Altogether, the investigators concluded that these dual-edited Ag-specific EngTregs had strong suppression activity toward activation and proliferation of effector T cells (Teff) cells, including those expressing a different islet TCR, which demonstrates their significant ability for bystander suppression.

“Dual-edited, Ag-specific, CISC expressing EngTregs represent a promising cell-based therapy for T1D simultaneously predicted to mediate tissue-specific bystander suppression and CISC-mediated enhanced in vivo survival and engraftment. Finally, this dual-editing platform is readily adaptable for use with alternative TCR (or CAR) cassettes designed to target a range of tissue-specific autoimmune or inflammatory diseases,” Cook and colleagues wrote.

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REFERENCE

Cook PJ, Hunt MS, Yang SJ, et al. Generation of islet-specific engineered regulatory T cells (EngTregs) for immune tolerance induction in type 1 diabetes using a novel dual-editing strategy. Presented at: ASGCT 25th Annual Meeting, May 16-19, 2022; Washington DC. Abstract #810