Characterization of engineered CAR-Treg cells to induce immune tolerance in liver transplanted patients

Abstract

Background & Aim

Regulatory T (Treg) cells play a critical role in maintaining immune tolerance and controlling inflammatory responses. Adoptive cell therapy with Tregs has been an exciting prospect for the modulation of immune responses in the clinic, indicating the feasibility and safety of this approach in multiple autoimmune and transplantation settings. However, the implementation of engineering tools to confer antigen-specificity and phenotypic stability is expected to enhance the effectiveness observed from previous Treg products.

Methodology

LIBERATE is a first-in-human Phase I/IIa clinical trial designed to evaluate the safety and activity of autologous CAR-Tregs in promoting liver transplantation tolerance in HLA-A2-negative patients who have received a graft from an HLA-A2-positive donor. A proprietary GMP manufacturing process has been developed to engineer recipient-derived QEL-001 cell products that express an anti-HLA-A2 targeted CAR, with a FOXP3 phenotype lock, and a safety switch. An extensive characterization of QEL-001 CAR-Treg products has demonstrated the maintenance of phenotypic and functional characteristics of unmodified Tregs.

Results

A safety cohort consisting of three patients found QEL-001 to be well tolerated within the protocol-defined dose range, with no serious adverse events or dose-limiting toxicities. No treatment related adverse events were reported during the 4-week post-dose follow-up. Analysis of blood samples by FACS and scRNAseq showed persistence of CAR-Tregs in circulation for up to 12 months post-infusion and maintenance of canonical markers of stable and effective Tregs. Liver biopsies collected post-infusion demonstrated phenotypic stability and evidence of graft trafficking, leading to substantial enrichment of CAR-Tregs in the liver compared to the periphery.

An expansion cohort is currently being conducted with the addition of lymphodepletion by low-dose rATG previous to QEL-001 infusion. Active ATG was cleared from circulation prior cell infusion and mediated a significant reduction in T-cell frequencies. QEL-001 CAR-Treg engraftment levels in circulation was improved compared to the safety cohort who did not receive rATG conditioning, and the Treg/Teff ratio increased favoring immunoregulation.

Conclusion

This study provides pioneering data to evaluate the phenotype and homeostasis of engineered Tregs in the clinic, supporting further investigation of these therapies in a broad range of inflammatory, autoimmune and transplantation applications.