Chemokine Decoy Receptor for Therapy of Autoimmune Arthritis

描述（由申请人提供）：目前类风湿性关节炎（“RA”）的治疗方法（皮质类固醇、甲氨蝶呤、TNF-中和）依赖于广谱免疫抑制，这种方法不是统一有效，并且经常伴有明显的副作用。为了填补这一市场空白，Radikal Therapeutics （RTX）正在开发一种新的可溶性受体诱饵受体融合蛋白（hR-421），可诱导抗原（Ag）特异性活化t细胞的免疫耐受。hR-421由Ig-Fc和CCR5受体的第二外显子结构域构建，结合并中和所有3个CCR5结合趋化因子配体(MIP-？, MIP - ?并阻止它们结合和激活CCR1、CCR3和CCR5膜受体。与CCR5抑制剂相比，mR-421 （hR-421的小鼠同源物）阻断CCR5不依赖的促炎途径，对CCR5敲除小鼠有效。即使在疾病发作后开始治疗，mR- 421治疗也能显著抑制实验性过敏性脑脊髓炎（EAE），这是一种经典的自身免疫模型系统。此外，从EAE供体中分离的ag特异性效应Th1细胞在体内经mR-421处理后产生的促炎细胞因子显著减少，并在过代转移实验中抑制EAE。后一种效应是由mR-421阻止Th1 CD4+ T细胞上的共刺激信号的能力驱动的。基于这些发现，我们假设R-421会阻止RA中Th1 CD4+细胞的共刺激，从而阻止其下游增殖和活化。我们现在建议将R-421技术的保护作用扩展到已发表的神经炎症研究结果之外，并在RA的临床相关模型中建立其潜在益处。雄性DBA小鼠在CFA中接种胶原蛋白，并在第21天再次刺激诱导自身免疫性关节炎，将在显著疾病（第21天）开始治疗mR-421 (2,4,8 mg/kg)，一种无关的IgG1对照，或依那西普（6.25 mg/kg），其特征是关节炎评分为2（0-16分）。此外，我们将包括一个假对照组，不暴露于胶原/CFA或治疗。在6周的时间内，将监测动物是否有关节炎的临床证据，在对照组中，该时间点的特征是整个爪子（包括手指）出现红斑和水肿（评分=12）。血浆m-R421浓度将与临床结果相关，从而建立药效学曲线，指导未来的临床给药。我们期望mR-421能够以剂量和血浆浓度依赖的方式减少关节损伤，其平均关节炎评分的降低等同于或优于临床批准的金标准药物依那西普的治疗效果。这些发现有望与mR-421对滑膜脂质过氧化、中性粒细胞浸润、促炎基因表达过氧亚硝酸盐产生、聚（adp核糖）聚合酶形成、大体和组织学损伤评分以及Th1和Treg淋巴细胞的引流淋巴结群的影响相平行。

DESCRIPTION (provided by applicant): Current therapeutic approaches to rheumatoid arthritis ("RA") (corticosteroids, methotrexate, neutralization of TNF-?) rely upon broad-spectrum immunosuppression, an approach that is not uniformly effective and is frequently associated with significant side-effects. To address this market gap, Radikal Therapeutics (RTX) is developing a novel soluble receptor decoy receptor fusion protein (hR-421) that induces immune tolerance in antigen (Ag)-specific activated T-cells. Constructed from Ig-Fc and the second ecto domain of the CCR5 receptor, hR-421 binds and neutralizes al 3 CCR5-binding chemokine ligands (MIP-?, MIP-?, RANTES) and prevents their binding and activation of the CCR1, CCR3, and CCR5 membrane receptors. In contrast to CCR5 inhibitors, mR-421 (the murine homologue of hR-421) blocks CCR5-independent pro-inflammatory pathways and is effective in CCR5 knock-out mice. Therapy with mR- 421 profoundly suppresses experimental allergic encephalomyelitis (EAE), a classic autoimmune model system, even when treatment is initiated after disease onset. Moreover, Ag-specific effector Th1 cells isolated from EAE donors treated in vivo with mR-421 produce substantially less pro-inflammatory cytokines and suppress EAE in adoptive transfer experiments. This latter effect is driven by the ability of mR-421 to prevent the co-stimulatory signal on Th1 CD4+ T cells. Based on these findings, we hypothesize that R-421 will prevent co-stimulation and thus the downstream proliferation and activation of Th1 CD4+ cells in RA. We now propose to extend the protective effects of the R-421 technology beyond the published findings in neuroinflammation and establish its potential benefit in a clinically-relevant model of RA. Male DBA mice inoculated with collagen in CFA and rechallenged on Day 21 to induce autoimmune arthritis, will be treated with mR-421 (2, 4, 8 mg/kg), an irrelevant IgG1 control, or etanercept (6.25 mg/kg) beginning at the time of significant disease (Day 21), as characterized by an arthritic score of 2 (scale of 0-16). Additionally, we will include a sham control group not exposed to collagen/CFA or treatment. Animals will be monitored for clinical evidence of arthritis over a period of 6 weeks, a timepoint characterized in controls by erythema and edema of the entire paw including digits (score=12). Plasma m-R421 concentrations will be related to clinical outcome, so as to construct a pharmacodynamic profile that will guide future clinical dosing. We expect mR-421 to reduce joint injury, in a dose and plasma concentration dependent fashion, as defined by a reduction in the mean arthritic score that is equivalent or superior to the treatment effect elicited by the gold-standard clinically-approved agent etanercept. These findings are expected to parallel the effects of mR-421 on synovial lipid peroxidation, neutrophil infiltration, pro-inflammatory gene expression peroxynitrite production, poly(ADP-ribose)polymerase formation, and gross and histologic injury scores, and on draining lymph node populations of Th1 and Treg lymphocytes. PUBLIC HEALTH RELEVANCE: Rheumatoid arthritis is a devastating autoimmune disease characterized by lifelong disability and inexorable progression. Currently approved agents are partially effective and nearly one-third of patients do not obtain adequate relief. We are developing a novel drug that specifically blocks the specific immune disturbance that underlies this condition. We will test this agent in a clinically-relevant small animal model and determine the most effective dose, in anticipation of definitive large animal studies to confirm its efficacy and safety.