OP02 IL23R-CAR-Tregs: creating a therapeutic breakthrough for Crohn’s Disease

Abstract Background Regulatory T cells (Tregs) are key immunomodulators to maintain immune homeostasis and self-tolerance, including in the intestine. Disrupted immune homeostasis is associated with Crohn’s Disease (CD) pathogenesis. As a living drug, Treg therapy is a promising treatment for restoring immune balance and achieving durable tissue tolerance in the diseased intestine. By targeting a disease-relevant protein, Interleukin-23 receptor (IL23R), we engineered Tregs expressing IL23R-chimeric antigen receptor (CAR) to create IL23R-CAR-Tregs for treating CD. Methods IL23R protein expression in CD intestine was verified by immunohistochemical analysis. Tonic signaling and CAR-specific activation were quantified during the IL23R-CAR screening. The IL23R-CAR-Treg phenotype was assessed by monitoring the expression of FoxP3 and Helios transcription factors, and the demethylation status of FoxP3 Treg-specific demethylated region (TSDR). The suppressive function of IL23R-CAR-Tregs was evaluated using in vitro assays and a colitis mouse model. The functionality of IL23R-CAR-Tregs were further assessed using intestinal biopsy-derived cells from CD patients in an in vitro activation assay. Transcriptomic and proteomic analyses were performed to associate molecular profiles with IL23R-CAR-Treg activation. Results Our highly potent IL23R-CAR lead candidate displays negligible tonic signalling and a strong signal-to-noise ratio. The resulting IL23R-CAR-Tregs maintain their regulatory phenotype with high FoxP3 and Helios expression and TSDR demethylation during in vitro expansion, CAR-specific stimulation, and in the presence of proinflammatory cytokines. In accordance with their regulatory phenotype, IL23R-CAR-Tregs exhibit CAR-dependent suppressive activity, promote a tolerogenic environment, and protect mice from colitis. The expression of IL23R was also confirmed in the intestinal mucosa from CD patients. Importantly, IL23R-CAR-Tregs elicit activation following exposure to intestinal biopsy-derived cells from CD, demonstrating the engagement and potency of IL23R-CAR towards their target in CD. We also identified molecular profiles that correlated with IL23R-CAR activation and, more broadly, showed their potential to monitor IL23R-CAR-Treg activity in CD patients. Conclusion Our results demonstrate that an IL23R-CAR-Treg product could be a promising therapy for CD patients, with the potential long-term benefits of immune tolerance.