Novel JAK Inhibitors to Reduce Graft-Versus-Host Disease after Allogeneic Hematopoietic Cell Transplantation in a Preclinical Mouse Model.

Allogeneic hematopoietic cell transplantation (allo-HCT) is a highly effective, well-established treatment for patients with various hematologic malignancies and non-malignant diseases. The therapeutic benefits of allo-HCT are mediated by alloreactive T cells in donor grafts. However, there is a significant risk of graft-versus-host disease (GvHD), in which the donor T cells recognize recipient cells as foreign and attack healthy organs in addition to malignancies. We previously demonstrated that targeting JAK1/JAK2, mediators of interferon-gamma receptor (IFNGR) and IL-6 receptor signaling, in donor T cells using baricitinib and ruxolitinib results in a significant reduction in GvHD after allo-HCT. Furthermore, we showed that balanced inhibition of JAK1/JAK2 while sparing JAK3 is important for the optimal prevention of GvHD. Thus, we have generated novel JAK1/JAK2 inhibitors, termed WU derivatives, by modifying baricitinib. Our results show that WU derivatives have the potential to mitigate GvHD by upregulating regulatory T cells and immune reconstitution while reducing the frequencies of antigen-presenting cells (APCs) and CD80 expression on these APCs in our preclinical mouse model of allo-HCT. In addition, WU derivatives effectively downregulated CXCR3 and T-bet in primary murine T cells. In summary, we have generated novel JAK inhibitors that could serve as alternatives to baricitinib or ruxolitinib.

Modeling Chronic Graft Versus Host Disease in Mice Using Allogeneic Bone Marrow and Splenocyte Transfer.

This unit describes a method for allogeneic bone marrow and splenocyte transfer for the modeling of chronic graft versus host disease (cGVHD) in mice. Preclinical models provide clinically relevant platforms for mechanistic and therapeutic studies that may inform the treatment of patients suffering from cGVHD, a common and potentially severe complication of allogeneic hematopoietic stem cell transplantation (alloHSCT). Most murine models of cGVHD depend on the transfer of major histocompatibility complex (MHC)-mismatched bone marrow and whole splenocytes (or purified T cells) into an irradiated recipient. The bone marrow contains hematopoietic stem and progenitor cells necessary to reconstitute the irradiated host hematopoietic system, while splenocytes contain T cells that mediate cGVHD. Of note, specific mouse strains, splenocyte dose, bone marrow quantity, and irradiation doses vary widely across different cGVHD models. Here we describe donor bone marrow and splenocyte preparation, recipient irradiation and intravenous injection of donor cells, and clinical monitoring for disease emergence and progression. © 2018 by John Wiley & Sons, Inc.

Baricitinib-induced blockade of interferon gamma receptor and interleukin-6 receptor for the prevention and treatment of graft-versus-host disease.

The therapeutic benefits of allogeneic hematopoietic stem cell transplantation (allo-HSCT) are derived from the graft-versus-leukemia (GvL) effects of the procedure. There is a strong association between the GvL effects and graft-versus-host disease (GvHD), a major life-threatening complication of allo-HSCT. The limiting of GvHD while maintaining the GvL effect remains the goal of allo-HSCT. Therefore, identifying optimal therapeutic targets to selectively suppress GvHD while maintaining the GvL effects represents a significant unmet medical need. We demonstrate that the dual inhibition of interferon gamma receptor (IFNγR) and interleukin-6 receptor (IL6R) results in near-complete elimination of GvHD in a fully major histocompatibility complex-mismatched allo-HSCT model. Furthermore, baricitinib (an inhibitor of Janus kinases 1 and 2 (JAK1/JAK2) downstream of IFNγR/IL6R) completely prevented GvHD; expanded regulatory T cells by preserving JAK3-STAT5 signaling; downregulated CXCR3 and helper T cells 1 and 2 while preserving allogeneic antigen-presenting cell-stimulated T-cell proliferation; and suppressed the expression of major histocompatibility complex II (I-Ad), CD80/86, and PD-L1 on host antigen-presenting cells. Baricitinib also reversed established GvHD with 100% survival, thus demonstrating both preventive and therapeutic roles for this compound. Remarkably, baricitinib enhanced the GvL effects, possibly by downregulating tumor PD-L1 expression.