Cell therapy using regulatory T cells (Tregs) has demonstrated therapeutic potential in treating several immune diseases in both preclinical and clinical studies. While CD4+ Tregs have been well characterized, CD8+ Tregs are gaining increasing attention for their emerging roles in immune regulation. We have shown that CD8+ Treg cell therapy is effective in preclinical models but has never been evaluated in a clinical trial. We designed a phase 1/2a clinical trial of cell therapy using GMP manufactured autologous polyclonal CD8+ Tregs to treat kidney transplanted patients from living donors.

First, we set up a method for the isolation of CD8+Tregs from peripheral blood of healthy individuals using positive magnetic selection and flow cytometry in a safe closed system. We determined optimal clinical-grade culture conditions to preserve high proliferation rate, baseline phenotypic profile, and suppressive function in vitro and in vivo in a model of acute GVHD in NSG mice. We verified that they were resistant to classic maintenance immunosuppressive drugs, persistent and efficient in vivo but not cytotoxic. The method was validated on cells from patients with renal insufficiency, then transferred in the GMP facility with 3 validation runs demonstrating the phenotypic and functional stability of CD8+ Treg, meeting quality controls and release criteria.

The clinical study is a first-in-human, one-arm, open-label, prospective trial in patients with end-stage chronic renal failure requiring primary kidney transplantation, with 3 escalating doses of CD8+ Tregs administered the day before the transplantation without induction treatment and associated with classic maintenance immunosuppression. Patients are monitored for long-term safety, immunosuppression burden and occurrences of infections. Transcriptomic and proteomic analyses on blood, biopsy, and urine samples will inform on persistence and migration of Tregs to the graft. Recruitment has started.