DataSheet_1_Inhibition of Bromodomain and Extra Terminal (BET) Domain Activity Modulates the IL-23R/IL-17 Axis and Suppresses Acute Graft-Versus-Host Disease.pdf

Acute graft-versus-host disease (GVHD) is the leading cause of non-relapse mortality following allogeneic hematopoietic cell transplantation. The majority of patients non-responsive to front line treatment with steroids have an estimated overall 2-year survival rate of only 10%. Bromodomain and extra-terminal domain (BET) proteins influence inflammatory gene transcription, and therefore represent a potential target to mitigate inflammation central to acute GVHD pathogenesis. Using potent and selective BET inhibitors Plexxikon-51107 and -2853 (PLX51107 and PLX2853), we show that BET inhibition significantly improves survival and reduces disease progression in murine models of acute GVHD without sacrificing the beneficial graft-versus-leukemia response. BET inhibition reduces T cell alloreactive proliferation, decreases inflammatory cytokine production, and impairs dendritic cell maturation both in vitro and in vivo. RNA sequencing studies in human T cells revealed that BET inhibition impacts inflammatory IL-17 and IL-12 gene expression signatures, and Chromatin Immunoprecipitation (ChIP)-sequencing revealed that BRD4 binds directly to the IL-23R gene locus. BET inhibition results in decreased IL-23R expression and function as demonstrated by decreased phosphorylation of STAT3 in response to IL-23 stimulation in human T cells in vitro as well as in mouse donor T cells in vivo. Furthermore, PLX2853 significantly reduced IL-23R+ and pathogenic CD4+ IFNγ+ IL-17+ double positive T cell infiltration in gastrointestinal tissues in an acute GVHD murine model. Our findings identify a role for BET proteins in regulating the IL-23R/STAT3/IL-17 pathway. Based on our preclinical data presented here, PLX51107 will enter clinical trial for refractory acute GVHD in a Phase 1 safety, biological efficacy trial.

急性移植物抗宿主病（GVHD）是异基因造血干细胞移植后非复发死亡的首要诱因。一线糖皮质激素治疗无应答的患者，其预估总体2年生存率仅为10%。溴结构域和额外末端结构域（BET）蛋白可调控炎症基因转录，因此有望成为缓解急性GVHD发病机制核心炎症反应的潜在靶点。本研究使用强效选择性BET抑制剂Plexxikon-51107与-2853（PLX51107和PLX2853），证实BET抑制可显著改善急性GVHD小鼠模型的存活情况并延缓疾病进展，且不会损害有益的移植物抗白血病效应。体外与体内实验均表明，BET抑制可降低T细胞同种异体反应性增殖、减少炎症细胞因子生成，并损伤树突状细胞成熟过程。对人类T细胞的RNA测序研究显示，BET抑制会影响炎症相关IL-17与IL-12基因的表达特征；染色质免疫沉淀（ChIP）测序则证实BRD4可直接结合于IL-23R基因位点。体外实验中，人类T细胞与体内实验中小鼠供体T细胞经IL-23刺激后，STAT3磷酸化水平均出现下降，表明BET抑制可降低IL-23R的表达与功能。此外，在急性GVHD小鼠模型中，PLX2853可显著减少胃肠道组织中IL-23R+与致病性CD4+ IFNγ+ IL-17+双阳性T细胞的浸润。本研究明确了BET蛋白在调控IL-23R/STAT3/IL-17通路中的作用。基于本文展示的临床前数据，PLX51107将进入难治性急性GVHD的Ⅰ期安全性与生物学效应临床试验。