Increased Foxp3(+)Helios(+) Regulatory T Cells and Decreased Acute Graft-Versus-Host Disease after Allogeneic Bone Marrow Transplantation in Patients Receiving Sirolimus and RGI-2001, an Activator of Invariant Natural Killer T Cells.

Publication Type:

Journal Article

Source:

Biology of blood and marrow transplantation : journal of the American Society for Blood and Marrow Transplantation (2017)

Abstract:

Regulatory T (Treg) cells play a central role in immune tolerance and prevention of aberrant immune responses. Several studies have suggested that the risk of GVHD after allogeneic hematopoietic cell transplantation (HCT) can be ameliorated by increasing Tregs. We have developed an approach of in vivo expansion of Tregs with RGI-2001, a novel liposomal formulation of a synthetic derivative of alpha-galactosylceramide, a naturally occurring ligand that binds to CD1 and activates and expands invariant natural killer cells. In preclinical studies, a single intravenous infusion of RGI-2001 expanded Treg and could ameliorate GVHD in a mouse model of allogeneic HCT. To explore the role of RGI-2001 in clinical HCT, we initiated a Phase IIa clinical trial (n=29), testing two different doses of RGI-2001 administered as a single infusion on day 0 of allogeneic HCT. RGI-2001 was well tolerated and without infusion reactions or cytokine release syndrome. A subset of patients (8/29, 28%) responded to RGI-2001 by inducing a markedly increased number of cells with a Treg phenotype. The Treg had a high Ki-67 index and were almost exclusively Helios(+) and Foxp3(+), indicating that their accumulation was due to expansion of natural Treg. Notably, the incidence of grade 2-4 GVHD in the eight patients who responded to RGI-2001 was 12.5%, compared to 52.4% in the 21 patients who did not respond. No grade 3-4 GVHD was observed in the responder group, compared to a 9.5% incidence among non-responders. Immunosuppression with sirolimus was also associated with a low incidence of GVHD, suggesting that RGI-2001 may have synergized with sirolimus to promote Treg expansion.