Targeting Jak3 in the treatment of autoimmune disease

细胞因子组成一个分泌蛋白大家族，调节细胞生长和多种类型细胞的分化。这些因子在调节免疫和炎症反应、调节淋巴样细胞的发育和分化方面尤为重要。毫不奇怪，细胞因子在类风湿性关节炎、系统性红斑狼疮、炎症性肠病和牛皮癣等自身免疫性疾病的发病机制中起着关键作用。了解细胞因子作用的分子基础有助于深入了解免疫介导性疾病的发病机制，并提供新的治疗靶点。 我们发现了人类JAK3，一种通过结合共同伽马链的细胞因子GC(IL-2、IL-4、IL-7、IL-9、IL-15和IL-21)进行信号传递所必需的激酶。我们发现JAK3的突变会导致一种称为严重联合免疫缺陷(SCID)的原发性免疫缺陷疾病。我们已经获得了两项与将JAK3作为新型免疫抑制/免疫调节药物基础的专利，并与辉瑞公司建立了合作研究和开发协议(CRADA)，以产生第一代JAK3拮抗剂。一种名为tofacitinib(CP 690,550)的化合物由辉瑞公司生产，并被发现在临床前模型中有效。该药物在类风湿性关节炎的第三阶段研究中进行了测试，现在已被批准用于这一适应症。托法替尼还被用于治疗牛皮癣、牛皮癣关节炎、强直性脊柱炎、青少年关节炎和移植排斥反应。其他几种JAK抑制剂已经开发出来，也在进行临床试验。 今年与辉瑞公司续签了CRADA，旨在更好地了解tofacitinib和相关抑制剂的作用机制。在考虑Jakinibs可能有用的临床情况时，我们认为移植物抗宿主病可能是这种药物有效的环境。这对我们来说是一个重要的问题，因为异基因造血干细胞移植的应用往往受到移植物抗宿主病(GVHD)的限制，GVHD是导致发病率和死亡率的一个重要原因。移植物抗宿主病患者的皮肤表现以界面性皮炎和硬皮病样改变为组织学特征。我们发现，托法替尼的应用阻止了CD8T细胞介导的GVHD样病的过继转移模型。疗效表现为全身疾病的减少和体重的减轻，以及粘膜皮肤病变的改善。更重要的是，托法替尼在逆转既定疾病方面也是有效的。托法替尼抑制小鼠CD8T细胞的增殖和活化，对IL-2刺激的人CD8T细胞也有类似的作用。托法替尼还抑制角质形成细胞表达干扰素诱导的趋化因子和干扰素诱导的角质形成细胞死亡。托法替尼可能是治疗GVHD患者CD8T细胞介导的黏膜皮肤病的有效药物。 今年，我们还研究了Jakinibs在癌症治疗中的应用。具体地说，我们试图确定tofacitinb是否可以限制宿主对免疫毒素的反应，这可能会限制后者的疗效。我们发现，用tofacitinib(JAK抑制剂)单一治疗小鼠，可以抑制对来自细菌蛋白假单胞菌外毒素A的免疫毒素的抗体反应，以及对模型Ag锁孔帽状血蓝蛋白的抗体反应。我们发现，在免疫后第21天，两种抗原的IgG1滴度都下降了1000倍。事实上，对所有的Ig G亚型和Ig M都有明显的抑制。不依赖胸腺的II型抗原也能减少IgG3的产生。机制研究显示，托法替尼治疗导致CD127+Pro-B细胞数量减少。此外，我们观察到托法替尼治疗的小鼠生发中心B细胞较少，生发中心形成受阻。由于在tofacitinib治疗期间仍存在正常的Ig水平，这种药物特别减少了从头开始的抗药抗体，从而保留了生物疗法的潜在疗效，包括那些用于癌症治疗的药物。 我们也一直在研究托法替尼对T细胞代谢的影响。T细胞的激活与糖酵解代谢的转换有关。我们发现托法替尼抑制了许多关键的糖酵解酶的诱导。干扰细胞因子调节的代谢变化可能是JAK抑制剂作用机制的一个重要方面。在相关研究中，我们检测了托法替尼对活化T细胞进化增强子景观的影响。我们发现，与典型的促进剂相比，托法替尼对拉伸/超级促进剂有选择性作用

Cytokines comprise a large family of secreted proteins that regulate cell growth and differentiation of many types of cells. These factors are especially important in regulating immune and inflammatory responses, regulating lymphoid development and differentiation. Not surprisingly, cytokines are critical in the pathogenesis of autoimmune diseases such as rheumatoid arthritis, systemic lupus erythematosus, inflammatory bowel disease and psoriasis. Understanding the molecular basis of cytokine action provides important insights into the pathogenesis of immune-mediated disease and offers new therapeutic targets. We discovered human Jak3, a kinase essential for signaling by cytokines that bind the common gamma chain, gc (IL-2, IL-4, IL-7, IL-9, IL-15 and IL-21). We found that mutation of Jak3 results in a primary immunodeficiency disorder termed severe combined immunodeficiency (SCID). We have received two patents related to targeting Jak3 as the basis for a new class of immunosuppressant/immunomodulatory drugs, and established a Cooperative Research and Development Agreement (CRADA) with Pfizer to generate the first-generation Jak3 antagonists. One compound, tofacitinib (CP 690,550), was produced by Pfizer and found to be effective in preclinical models. The drug was tested in Phase III studies in rheumatoid arthritis, and has now been approved for this indication. Tofacitinib is also being studied in psoriasis, psoriatic arthritis, ankylosing spondylitis, juvenile arthritis and transplant rejection. Several other Jak inhibitors have been developed and are also in clinical trials. The CRADA with Pfizer was renewed this year and was directed at better understanding the mechanisms of action of tofacitinib and related inhibitors. In considering clinical circumstances in which Jakinibs might be useful, we thought a graft-versus-host-disease might be setting in which this agent would be effective. This struck us as an important problem in that the utility of allogeneic hematopoietic stem cell transplantation is often limited by graft-versus-host disease (GVHD), a problem which is a significant cause of morbidity and mortality. Patients with GVHD exhibit cutaneous manifestations with histological features of interface dermatitis followed by scleroderma-like changes. We found that administration of tofacitinib prevented an adoptive transfer model of GVHD-like disease mediated by CD8 T cells. Efficacy was manifested by reduction in systemic disease and weight loss, as well as amelioration of mucocutaneous lesions. More importantly, tofacitinib was also effective in reversing established disease. Tofacitinib diminished the expansion and activation of murine CD8 T cells in this model, and had similar effects on IL-2-stimulated human CD8 T cells. Tofacitinib also inhibited the expression of IFN-γ-inducible chemoattractants by keratinocytes, and IFN-γ-inducible cell death of keratinocytes. Tofacitinib may be an effective drug for treatment against CD8 T-cell-mediated mucocutaneous diseases in patients with GVHD. This year we also investigated the utility of Jakinibs in the setting of cancer therapy. Specifically, we sought to determine whether tofacitinb could limit the host response to immunotoxins, which can limit the efficacy of the latter. We found that monotherapy of mice with tofacitinib (the JAK inhibitor) quells antibody responses to an immunotoxin derived from the bacterial protein Pseudomonas exotoxin A, as well as to the model Ag keyhole limpet hemocyanin. We found that thousand-fold reductions in IgG1 titers to both Ags were observed 21 d post immunization. In fact, suppression was evident for all IgG isotypes and IgM. A reduction in IgG3 production was also noted with a thymus-independent type II Ag. Mechanistic investigations revealed that tofacitinib treatment led to reduced numbers of CD127+ pro-B cells. Furthermore, we observed fewer germinal center B cells and the impaired formation of germinal centers of mice treated with tofacitinib. Because normal Ig levels were still present during tofacitinib treatment, this agent specifically reduced de novo anti-drug Abs, thus preserving the potential efficacy of biological therapeutics, including those used as cancer therapeutics. We have also been studying the effects of tofacitinib on T cell metabolism. T cell activation is associated with a switch to glycolytic metabolism. We have found that tofacitinib inhibits the induction of many key glycolytic enzymes. The interference with cytokine-regulated changes in metabolism may be an important aspect of the mechanism of action of Jak inhibitors. In related studies, we examined the effect of tofacitinib on the evolving enhancer landscapes of activated T cells. We found that tofacitinib has a selective effect on stretch/super enhancers compared to typical enhancers