Ibrutinib treatment ameliorates murine chronic graft-versus-host disease.

Chronic graft-versus-host disease (cGVHD) is a life-threatening impediment to allogeneic hematopoietic stem cell transplantation, and current therapies do not completely prevent and/or treat cGVHD. CD4+ T cells and B cells mediate cGVHD; therefore, targeting these populations may inhibit cGVHD pathogenesis. Ibrutinib is an FDA-approved irreversible inhibitor of Bruton's tyrosine kinase (BTK) and IL-2 inducible T cell kinase (ITK) that targets Th2 cells and B cells and produces durable remissions in B cell malignancies with minimal toxicity. Here, we evaluated whether ibrutinib could reverse established cGVHD in 2 complementary murine models, a model interrogating T cell-driven sclerodermatous cGVHD and an alloantibody-driven multiorgan system cGVHD model that induces bronchiolar obliterans (BO). In the T cell-mediated sclerodermatous cGVHD model, ibrutinib treatment delayed progression, improved survival, and ameliorated clinical and pathological manifestations. In the alloantibody-driven cGVHD model, ibrutinib treatment restored pulmonary function and reduced germinal center reactions and tissue immunoglobulin deposition. Animals lacking BTK and ITK did not develop cGVHD, indicating that these molecules are critical to cGVHD development. Furthermore, ibrutinib treatment reduced activation of T and B cells from patients with active cGVHD. Our data demonstrate that B cells and T cells drive cGVHD and suggest that ibrutinib has potential as a therapeutic agent, warranting consideration for cGVHD clinical trials.

Epigenetic repolarization of T lymphocytes from chronic lymphocytic leukemia patients using 5-aza-2'-deoxycytidine.

T cell immune dysfunction has an important role in the profound immune suppression that characterizes chronic lymphocytic leukemia (CLL). Improper polarization of T cells has been proposed as one of the mechanism involved. Mounting data implicates chromatin regulation, namely promoter methylation, in the plasticity of naïve human T cells. Recent in vitro evidence indicates that this plasticity may be phenotypically altered by using methylation inhibitors which are approved for clinical use in certain types of cancer. These results beg the question: can the ineffective polarization of T lymphocytes in the context of CLL be effectively modulated using methylation inhibitors in a sustainable therapeutic fashion? To answer this question our laboratory has studied the effects of 5-aza-2'-deoxycytidine (5A2) in helper and cytotoxic T lymphocytes from healthy donors and CLL patients in well characterized molecular and epigenetic signaling pathways involved in effective polarization. Moreover, we sought to investigate the consequences of methylation inhibitor treatment on lymphocyte survival, activation intensity, and naïve cell polarization. Our data indicates that 5A2 treatment can depolarize Th2 cells to effectively secrete interferon gamma, signal via T-bet, and achieve demethylation of critical Th1 specific promoters. Moreover, we demonstrate that 5A2 can force Th1 polarization of naïve T cells despite a strong IL-4 stimuli and a lack of IL-12. In conclusion our data seeks to define a modality in which improper or ineffective T cell polarization can be altered by 5AZA and could be incorporated in future therapeutic interventions.