Autologous Lentiviral Vector LVFOXP3 CD4 T Cells for IPEX Syndrome

A first-in-human (FIH) Phase 1 clinical trial with a novel regulatory T (Treg) cell therapy product to treat IPEX syndrome is ongoing (NCT05241444) at our center. We administer autologous engineered CD4LVFOXP3 Treg-like cells, lentiviral vector (LV)-transduced CD4+ T cells expressing wild-type human FOXP3. Primary objectives include feasibility and safety. Our secondary objective is to assess the impact of CD4LVFOXP3 infusion on clinical manifestations. The study is a 2 + 4 dose escalation trial design with 3 doses in two different age cohorts. A total of six patients have been treated. The first two patients in the >12-year-old cohort received the lowest dose (1 × 106/kg) and the second two received the intermediate dose (3 × 106/kg). Two patients <12 yrs of age received the intermediate dose. Feasibility of GMP manufacturing of high-purity CD4LVFOXP3 cells was met. There have been no safety concerns. CD4LVFOXP3 expresses membrane tNGFR (CD271) from the same LV construct that expresses the FOXP3 cDNA, facilitating ex vivo purification during manufacturing and in vivo traceability. Pharmacokinetics shows that CD4LVFOXP3 are detectable in blood and tissue; their phenotypic and functional stability has been confirmed at the single-cell level by CITEseq on the drug substance and ex vivo. We found that CD4LVFOXP3 maintain the T helper subsets’ heterogeneity of the parental cells but express the transgene FOXP3-lv and Treg marker genes, including CCR4, CTLA4, and IL2RA and low IL7R. There was lower expression of the inflammatory cytokines IL17A, IL17F, IL22, IL15, IFNg, constrained TCR clone expansion, and cycling status. More intriguingly, we found that the most dominant subset of CD4 LV-FOXP3 cells have stem cell memory features, most likely derived from naïve CD4+ T cells. We also found that CD4LVFOXP3 cells can survive over one year in small proportion. Thus, these findings reveal that CD4LVFOXP3 products preserve their Treg-like signatures, maintain their stemness from naïve cells, and keep their identity in vivo. Successful completion of this trial will address a significant unmet medical need while also providing proof of safety and feasibility of this novel therapy. These data could expand the application of autologous CD4LVFOXP3 to additional autoimmune disorders. Figure 1. Features of 20 CCSs with persistent cytopenia (A), cumulative incidence of autoimmune phenomena (B), and lymphocyte subpopulations (C).