Chronic graft-versus-host disease (cGVHD) remains a major complication following allogeneic bone marrow transplantation (BMT). The discovery of novel therapeutics is dependent on assessment in preclinical murine models of cGVHD. Rho-associated kinase 2 (ROCK2) recently was shown to be implicated in regulation of interleukin-21 (IL-21) and IL-17 secretion in mice and humans. Here, we report that the selective ROCK2 inhibitor KD025 effectively ameliorates cGVHD in multiple models: a full major histocompatibility complex (MHC) mismatch model of multiorgan system cGVHD with bronchiolitis obliterans syndrome and a minor MHC mismatch model of sclerodermatous GVHD. Treatment with KD025 resulted in normalization of pathogenic pulmonary function, which correlates with a marked reduction of antibody and collagen deposition in the lungs of treated mice to levels comparable to non-cGVHD controls. Spleens of mice treated with KD025 had decreased frequency of T follicular helper cells and increased frequency of T follicular regulatory cells, accompanied by a reduction in signal transducer and activator of transcription 3 (STAT3) and concurrent increase in STAT5 phosphorylation. The critical role of STAT3 in this cGVHD model was confirmed by data showing that mice transplanted with inducible STAT3-deficient T cells had pulmonary function comparable to the healthy negative controls. The therapeutic potential of targeted ROCK2 inhibition in the clinic was solidified further by human data demonstrating the KD025 inhibits the secretion of IL-21, IL-17, and interferon g along with decreasing phosphorylated STAT3 and reduced protein expression of interferon regulatory factor 4 and B-cell lymphoma 6 (BCL6) in human peripheral blood mononuclear cells purified from active cGVHD patients. Together these data highlight the potential of targeted ROCK2 inhibition for clinical cGVHD therapy.
Bibliographical noteFunding Information:
The authors thank Kadmon Corporation for providing KD025; Drs John J. O'Shea and Yuka Kanno for providing CD4-cre X Stat3fl/fl cells; Dr John Ryan for critical reading of the manuscript; and Randy Donelson for tissue preparation and staining. This study was funded by the National Institutes of Health, National Cancer Institute grants P01 CA142106-06A1 and 5P01-CA047741-20 (B.R.B.) and R01-CA122779 (L.L.); National Institute of Allergy and Infectious Diseases grants P01 AI 056299, T32 AI 007313, and K08HL107756; Leukemia and Lymphoma Society Translational Research grants 6458-15 and 6462-15; and the Kadmon Corporation.
© 2016 by The American Society of Hematology.