Targeting Jak3 in the treatment of autoimmune disease

细胞因子包括调节许多类型细胞的细胞生长和分化的分泌蛋白的大家族。这些因子在调节免疫和炎症反应、调节淋巴发育和分化中特别重要。 细胞因子还调节免疫稳态、耐受性和记忆。毫不奇怪，细胞因子在自身免疫性疾病如类风湿性关节炎、系统性红斑狼疮、炎症性肠病和银屑病的发病机制中至关重要。 了解细胞因子作用的分子基础为免疫介导疾病的发病机制提供了重要的见解，并提供了新的治疗靶点。 我们发现了Jak 3，这是一种通过结合常见γ链gc（IL-2、IL-4、IL-7、IL-9、IL-15和IL-21）的细胞因子进行信号传导所必需的激酶。我们发现Jak 3突变导致一种原发性免疫缺陷疾病，称为严重联合免疫缺陷（SCID）。我们获得了靶向Jak 3的专利，作为一类新的免疫抑制剂药物的基础，并与辉瑞公司建立了CRADA，以产生第一代Jak 3拮抗剂。一种化合物CP 690，550由辉瑞公司生产，并在临床前模型中有效。该药目前正在类风湿性关节炎、银屑病和移植排斥的II期研究中进行测试，在这些研究中它似乎是有效的。 与辉瑞的CRADA今年更新，旨在更好地了解该药物的作用机制。 我们首先评估CP 690，550对IL-2激活的生化途径的影响。 多年来，关于细胞因子信号传导的Jak依赖性和独立性方面一直存在争议。 然而，到目前为止，我们已经发现，响应于IL-2而磷酸化的所有底物都被CP 690，550废除。 这些包括MAPK和AKT激活，以及STAT激活。我们还确定了CP 690，550对T细胞增殖和活力具有显著的影响。 我们接下来评估了Jak 3抑制剂对CD 4+辅助细胞分化的影响。 CD 4 + T细胞具有许多潜在的命运。除了众所周知的辅助性T细胞命运，T辅助1和T辅助2细胞，现在还认识到其他命运。调节性T细胞（Treg细胞）是维持外周耐受的重要亚群。T细胞在胸腺中由CD 4 + T细胞（天然Treg细胞或nT细胞）产生，并且可以在外周（iTreg细胞）中诱导。nTreg和iTreg细胞均表达转录因子叉头盒蛋白3（Foxp 3）。Foxp 3的缺乏导致小鼠模型和人类中的致命自身免疫;人类中的疾病被称为IPEX。最近认识到的CD 4 + T细胞亚群是优先产生细胞因子IL-17的细胞（Th 17细胞）。IL-17是一种主要的炎性细胞因子，其似乎有助于许多自身免疫性和自身炎性疾病的发病机制，包括类风湿性关节炎、脊柱关节病、多发性硬化症和炎性肠病。令人感兴趣的是，Th 17细胞被认为与调节性T细胞（TCLs）在发育上相关，因为在不同细胞因子的情况下，在转化生长因子-β（TGFb-1）的存在下，这两个亚群都可以从初始CD 4 + T细胞诱导。我们发现CP 690，550阻断Th 1和Th 2分化。后者可以通过对IL-4信号传导的影响来解释，IL-4信号传导依赖于gc/Jak 3。 我们发现前者也被阻断，这是因为CP 690，550通过对Jak 1的影响阻断了IFNg信号传导。 还检查了CP 690，550对自身免疫的体内模型的作用。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CP 690，550具有超出对gc细胞因子的作用的作用。我们发现关节炎关节中IL-17的表达减少。我们认为，这些影响是这种药物疗效的一个重要方面。 在与NIDDK和NHGRI的合作中，我们还研究了CP 690，550的立体化学，发现只有CP 690，550的3R，4 R异构体有效抑制Jak 3。

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 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 received a patent for targeting Jak3 as the basis for a new class of immunosuppressant drugs and established a CRADA with Pfizer to generate a the first generation Jak3 antagonists. One compound, CP 690,550, was produced by Pfizer and found to be effective in preclinical models. The drug is being tested presently in Phase II 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 CP 690,550. These include MAPK and AKT activation, as well as STAT activation. We have also determined that CP 690,550 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 690,550 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 CP 690,550 blocked IFNg signaling via effects on Jak1. The effects on CP 690,550 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 CP 690,550 has actions beyond effects on gc cytokines. , we found reduced expression of IL-17 in arthritic joints. We believe that these effects are an important aspect of the efficacy of this drug. In a collaboration with NIDDK and NHGRI, we also investigated the stereochemistry of CP 690,550 and found that only the 3R, 4R isomer of CP 690,550 potently inhibited Jak3.