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。细胞因子还调节免疫稳态、耐受性和记忆力。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Haman 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靶向JAK3作为新型免疫抑制/免疫调节药物基础的专利，并与辉瑞建立了CRADA，以产生第一代JAK3拮抗剂。一种名为他索替尼(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。该药物目前正在类风湿性关节炎、牛皮癣和移植排斥反应的第三阶段研究中进行测试，似乎是有效的。今年与辉瑞公司续签了CRADA，旨在更好地了解该药物的作用机制。 我们首先评估了CP 690,550对IL-2激活的生化途径的影响。多年来，关于细胞因子信号的JAK依赖和独立方面一直存在争议。然而，到目前为止，我们已经发现，所有对IL-2反应的底物都被他索替尼所废除。其中包括MAPK和AKT的激活，以及STAT的激活。我们还确定他西替尼对T细胞的增殖和活性有显著影响。 接下来，我们评估了JAK3抑制剂对CD4+辅助细胞分化的影响。CD4+T细胞有许多潜在的命运。除了众所周知的辅助性T细胞命运，T辅助者1和T辅助者2细胞，其他命运现在被识别。调节性T细胞(Treg细胞)是维持外周耐受的重要亚群。Tregs在胸腺中由CD4+T细胞(天然Treg细胞或nTregs)产生，并可在外周(iTreg细胞)中诱导。NTreg和iTreg细胞都表达转录因子叉头盒蛋白3(FOXP3)。在小鼠模型和人类中，缺乏Foxp3会导致致命性自身免疫；人类的这种疾病被称为IPEX。最近发现的一个更新的CD4+T细胞亚群是优先产生细胞因子IL-17(Th17细胞)的细胞。IL-17是一种主要的炎性细胞因子，在类风湿性关节炎、脊柱关节病、多发性硬化症和炎症性肠病等多种自身免疫性和自身炎症性疾病的发病机制中起重要作用。有趣的是，Th17细胞被认为与调节性T细胞(Tregs)发育相关，因为这两个亚群都可以在不同细胞因子的背景下，在转化生长因子-β(TGFb-1)的存在下从原始的CD4+T细胞诱导而来。我们发现CP Tasocitinib抑制了Th1和Th2的分化。后者可以通过对IL-4信号的影响来解释，这依赖于GC/JAK3。我们发现前者也被阻断，这是因为tasocitinib通过对JAK1的作用而阻断了IFNG信号。他西替尼还被发现可以阻断依赖IL-23的Th17细胞的产生。Tasocitinib对体内自身免疫模型的影响我们发现CP 690,550在减轻关节炎模型中的疾病方面非常有效。重要的是，我们还发现他索替尼的作用超出了对GC细胞因子的影响。具体地说，我们研究了这种药物对先天性免疫反应的影响，发现他西替尼可以抑制急性脓毒症模型中的炎症。我们认为，这些作用代表了该药物治疗类风湿性关节炎和其他自身免疫性疾病疗效的重要方面。 在最近与NCI合作进行的研究中，我们调查了他西替尼作为免疫毒素治疗癌症的辅助药物的疗效。在小鼠模型中，我们发现他索替尼非常有效地阻断了对免疫毒素的免疫反应。这是最近提交的一项专利的主题。

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. Cytokines also regulate immune homeostasis, tolerance, and memory. 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 haman 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 CRADA with Pfizer to generate a the first generation Jak3 antagonists. One compound, tasocitinib (CP 690,550), was produced by Pfizer and found to be effective in preclinical models. The drug is being tested presently in Phase III studies in rheumatoid arthritis, psoriasis and transplant rejection, where it appears to be efficacious. The CRADA with Pfizer was renewed this year and was directed at better understanding the mechanisms of action of this drug. We began by assessing the effect of CP 690,550 on biochemical pathways activated by IL-2. There has been debate over the years regarding Jak-dependent and independent aspects of cytokine signaling. However, to date, we have found that all substrates phosphorylated in response to IL-2 are abrogated by tasocitinib. These include MAPK and AKT activation, as well as STAT activation. We have also determined that tasocitinib has dramatic effects on T cell proliferation and viability. We next assessed the effect of the Jak3 inhibitor on CD4+ helper cell differentiation. CD4+ T cells have a number of potential fates. In addition to the well-known helper T cell fates, T helper 1 and T helper 2 cells, other fates are now recognized. Regulatory T cells (Treg cells) are an essential subset that maintains peripheral tolerance. Tregs are generated in the thymus from CD4+ T cells (natural Treg cells or nTregs) and can be induced in the periphery (iTreg cells). Both nTreg and iTreg cells express a transcription factor, forkhead box protein 3 (Foxp3). Deficiency of Foxp3 results in lethal autoimmunity in mouse models and in humans; the disease in humans is termed IPEX. An even more recently recognized subset of CD4+ T cells is cells that preferentially produce the cytokine IL-17 (Th17 cells). IL-17 is a major inflammatory cytokine, which appears to contribute to the pathogenesis of many autoimmune and autoinflammatory disorders including rheumatoid arthritis, spondyloarthropathy, multiple sclerosis and inflammatory bowel disease. Of interest is that Th17 cells are thought to be developmentally related to regulatory T cells (Tregs) as both subsets can be induced from naive CD4+ T cells in the presence of transforming growth factor-beta (TGFb-1) in the context of different cytokines. We found that CP tasocitinib blocked Th1 and Th2 differentiation. The latter can be explained by effects on IL-4 signaling, which is dependent upon gc/Jak3. We found that the former was also blocked and this was because tasocitinib blocked IFNg signaling via effects on Jak1. Tasocitinib was also found to block IL-23-dependent generation of Th17 cells. The effects on tasocitinib on in vivo models of autoimmunity where also examined We have found that CP 690,550 is very effective in attenuating disease in arthritis models. Importantly, we have also found that tasocitinib has actions beyond effects on gc cytokines. Specifically, we investigated the effect of this drug on innate immune responses and found that tasocitinib blocks inflammation in an acute sepsis model. We believe that these effects represent important aspects of the efficacy of this drug in rheumatoid arthritis and other autoimmune disorders. In more recent studies done in collaboration with NCI, we have investigated the efficacy of tasocitinib as an adjunct in immunotoxin therapy for the treatment of cancer. In a mouse model, we have found that tasocitinib very effectively blocks immune responses to immunotoxins. This is the subject of a recently submitted patent.