First-in-human phase 1 trial of induced regulatory T cells for graft-versus-host disease prophylaxis in HLA-matched siblings

Human CD4(+)25(-) T cells cultured in interleukin 2 (IL-2), rapamycin, and transforming growth factor beta (TGF beta) along with anti-CD3 monoclonal antibody-loaded artificial antigenpresenting cells generate FoxP3(+) induced regulatory T cells (iTregs) with potent suppressive function. We performed a phase 1, single-center, dose-escalation study to determine the safety profile of iTregs in adults with high-risk malignancy treated with reduced-intensity conditioning and mobilized peripheral blood stem cells (PBSCs) from HLA-identical sibling donors. Sixteen patients were enrolled and 14 were treated (2 productions failed to meet desired doses). One patient each received 3.0 x 10(6)/kg, 3.0 x 10(7)/kg, and 3.0 x 10(8)/kg iTregs with corresponding T-conventional-to-iTreg ratios of 86:1, 8:1, and 1:2. After 3 patients received 3.0 x 10(8)/kg in the presence of cyclosporine (CSA) and mycophenolate mofetil (MMF) with no dose-limiting toxicities, subsequent patients were to receive iTregs in the presence of sirolimus/MMF that favors Foxp3 stability based on preclinical modeling. However, 2 of 2 developed grade 3 acute graft-versus-host disease (GVHD), resulting in suspension of the sirolimus/MMF. An additional 7 patients received 3.0 x 10(8)/kg iTregs with CSA/MMF. In the 14 patients treated with iTregs and CSA/MMF, there were no severe infusional toxicities with all achieving neutrophil recovery (median, day 13). Of 10 patients who received 3.0 x 10(8)/kg iTregs and CSA/MMF, 7 had no aGVHD, 2 had grade 2, and 1 had grade 3. Circulating FoxP3(+) iTregs were detectable through day 14. In summary, iTregs in the context of CSA/MMF can be delivered safely at doses as high as 3 x 10(8)/kg.

Automated summary

The study showed that iTregs can be safely delivered at high doses in adults with high-risk malignancy receiving HLA-identical sibling donor PBSCs in the context of CSA/MMF, without severe toxicities.