Tu116 - Base Editing Treg Cells to Avoid Teplizumab Binding to Enable Combination Therapy

Abstract Text: Type 1 Diabetes (T1D) is an autoimmune condition characterized by immune destruction of beta cells leading to low insulin levels. Normally, immune tolerance results from depleting autoreactive immune cells and inducing regulatory immune cells, which suppress unwanted immune activation. We hypothesize that mimicking this process, inactivating effector T cells while enhancing regulatory T cells (Tregs), will lead to durable disease remission in T1D patients. Teplizumab, an FDA-approved treatment that slows the onset of T1D in high-risk individuals, is a humanized monoclonal anti-CD3 antibody which binds CD3ε and preferentially inhibits activated T cells. Thus, combining teplizumab with Treg is an attractive concept for restoring tolerance. However, Tregs are also targeted by teplizumab, making this therapy less synergistic. In this study, we used CRISPR-Cas9 base editors to edit CD3e and confer teplizumab resistance to Tregs. A pooled gRNA library spanning the extracellular domain of hCD3ε was used to identify targets that remove teplizumab binding while retaining the TCR-CD3 complex. The selected gRNAs were assessed for their ability to remove the Teplizumab epitope without loss of function. Successfully edited human T cells had no impairment in their responses to alloantigens in vitro. Their ability to induce xenogeneic graft-versus-host disease in NSG mice are being evaluated. We have shown it is feasible to edit CD3e removing Teplizumab epitope without negatively impacting T cell function. Future work will evaluate edited Tregs and teplizumab in appropriate T1D mouse models, to provide important pre-clinical proof of concept for combination tolerogenic therapy for T1D and other autoimmune diseases.