From therapeutic mechanisms to unraveling the pathophysiology of MS

从治疗机制到揭示多发性硬化症的病理生理学

• 批准号: 8158239
• 负责人: Bibiana Bielekova
• 金额: $ 136.63万
• 依托单位: NATIONAL INSTITUTE OF NEUROLOGICAL DISORDERS AND STROKE
• 依托单位国家: 美国
• 资助国家: 美国
• 起止时间: 至
• 项目状态: 未结题
• 来源: https://reporter.nih.gov/project-details/8158239
• 关键词: Functional disorder; Therapeutic

Multiple Sclerosis (MS) is an inflammatory, demyelinating disorder of the central nervous system (CNS). The etiology of MS remains unclear, but the disease develops in genetically susceptible individuals exposed to environmental triggers. The long favored hypothesis in MS implicates autoreactive T cells generated in the periphery that access the CNS, where they induce injury of previously normal neural tissues. However, in contrast to the animal model experimental autoimmune encephalomyelitis (EAE), neither the target(s) of the immune response nor the cells responsible for CNS damage have been identified in MS. Furthermore, the failure of some MS treatments targeting processes that underlie the development of CNS tissue destruction in EAE (e.g. IFN-g, TNF-a inhibitors) indicates that different mechanisms may cause the development of disability in MS versus EAE. Therefore, there is a need to identify pathophysiological mechanisms that are specific for MS, but may not be predicted from EAE. Therapeutic trials, especially those that investigate novel therapeutic agents, represent a unique opportunity to investigate how specific perturbations of the biological system affect MS disease process. The goal of this project is to carefully study the biological perturbations induced by the application of novel therapeutic agents in Phase I/II clinical trials in MS in order to define mechanisms of CNS tissue injury, but also those that underlie beneficial immunoregulation and immune-mediated neuroprotection. By correlating changes measured in the biological system (e.g. different functions of the T cells or other immune cell subsets) with structural changes of CNS destruction or repair (measured by neuroimaging modalities), and with clinical outcomes, we can understand which biological processes are beneficial and which are harmful in the MS pathogenesis. Additionally, understanding which effects of applied therapies underlie their therapeutic benefit will allow us to define biomarkers that are indicative, and ideally also predictive of the full therapeutic response. We are currently studying immunomodulatory properties of three therapeutic agents: daclizumab, idebenone and rituximab in 3 investigator-initiated Phase I/II clinical trials performed under Investigational New Drug (IND) application (PI, Bibiana Bielekova). Our results are briefly summarized below: Daclizumab is a humanized monoclonal Ab against CD25, which is the alpha chain of the IL-2 receptor (IL-2R). CD25 is highly upregulated on activated T cells and contribution of CD25 to high-affinity IL-2 signaling was believed to be paramount for expansion of effector T cells. Thus, it was expected that daclizumab therapy will result in inhibition of T cell functions. Previously we have demonstrated that daclizumab is highly effective in suppressing MS-related inflammatory activity. However, this therapeutic effect was not paralleled by inhibition of T cells. Instead, we determined that daclizumab selectively expands CD56bright natural killer (NK) cells and that this human-specific NK cell population has immunoregulatory function through its ability to kill activated autologous T cells. The expansion of CD56bright NK cells correlated with treatment outcome, suggestive that it can be utilized as biomarker of therapeutic response. This observation has now been fully reproduced in double-blind, placebo-controlled multicenter Phase II trial of daclizumab in MS. We continue to study the mechanism of action (MOA) of daclizumab in MS in new Phase I open label therapeutic trial of DAC-HYP (second generation of daclizumab) in patients with high-inflammatory MS (protocol 10-N-0125), with the goal to determine all effects of daclizumab on human immune system. We determined that daclizumab expands CD56bright NK cells paradoxically in IL-2 dependent manner; because daclizumab prevents consumption of IL-2 by activated T cells, the excess of IL-2 can be utilized by CD56bright NK cells through intermediate-affinity IL-2 receptors. Furthermore, we determined the mechanism of killing of activated T cells by CD56bright NK cells and the paper describing our novel findings is currently in review. We also determined that daclizumab has effects on other cells of the innate immune system, specifically on mature dendritic cells. The paper describing this MOA is also currently in review. Idebenone is a lipid soluble synthetic analogue of coenzyme-Q (CoQ). As such, it both improves mitochondrial metabolism and has an antioxidant effect. Primary-progressive MS (PP-MS) is resistant to therapy by immunomodulatory agents. Mitochondrial dysfunction coupled with oxidative stress has been proposed as one of the top alternative hypotheses underlying pathophysiology of PP-MS. Therefore, we initiated double-blind phase I/II clinical trial of idebenone versus placebo (protocol 09-N-0197) to test the hypothesis whether mitochondrial dysfunction and oxidative stress contribute to development of neurological disability in PP-MS. Efficacy of idebenone in suppressing oxidative stress intrathecally and its unexplored immunomodulatory effects are being measured by ex-vivo analysis of PBMC functions and CSF biomarkers in enrolled patients. Rituximab is a B cell depleting chimeric monoclonal Ab and has inhibitory effect on MS disease activity in patients with evidence of blood-brain barrier (BBB) breakdown. The current leading hypothesis is that B cells collaborate with antigen-specific T cells and support T cell activation through antigen-presentation functions and mutual co-stimulation. Furthermore, there is evidence that in secondary-progressive MS (SP-MS) patients B cells and T cells form tertiary lymphoid follicles deep within the brain sulci. These ectopic lymphoid follicles recapitulate activation of antigen-specific T and B cells within the intrathecal compartment. Unfortunately, because majority of progressive MS patients do not have overt BBB disruption, only about 0.1% of systemically administered rituximab gains access to CNS compartment, which is not sufficient to deplete CNS B cells. Therefore, we are testing the hypothesis that intrathecal administration of rituximab in patients with SP-MS will effectively deplete B cells in the CNS compartment and this will translate into therapeutic effect of rituximab on biomarkers of CNS tissue injury in the placebo-controlled, Phase II trial of rituximab in low-inflammatory SP-MS (protocol T-N-1235). While there are many agents that have biologically plausible MOA for testing their efficacy in progressive MS, the drug development is currently hampered by the fact that we have no sensitive interim outcome measure. Therefore, current Phase II studies in progressive MS require enrollment of hundreds of MS patients and are prohibitively expensive. Both of our double-blind placebo-controlled investigator-initiated Phase II clinical trials (i.e. idebenone and IT rituximab) share identical adaptive trial design focusing on the evaluation of different (mostly novel) quantitative clinical, functional and imaging outcome measures. The hope is that collected data from these 2 studies will help to define new, more effective clinical trial design for future Phase II therapeutic trials in progressive MS.

多发性硬化症 (MS) 是一种中枢神经系统 (CNS) 炎症性脱髓鞘疾病。 多发性硬化症的病因尚不清楚，但这种疾病是在暴露于环境触发因素的遗传易感个体中发生的。 长期以来在多发性硬化症中备受青睐的假设表明，外周细胞产生的自身反应性 T 细胞进入中枢神经系统，在中枢神经系统中它们会引起先前正常神经组织的损伤。 然而，与动物模型实验性自身免疫性脑脊髓炎（EAE）不同，多发性硬化症中既没有识别出免疫反应的靶标，也没有识别出导致中枢神经系统损伤的细胞。此外，一些针对 EAE 中 CNS 组织破坏发展过程的 MS 治疗（例如 IFN-g、TNF-a 抑制剂）的失败表明，不同的机制可能导致 MS 与 EAE 中残疾的发展。因此，需要确定 MS 特有的、但可能无法通过 EAE 预测的病理生理机制。治疗试验，特别是那些研究新型治疗药物的试验，为研究生物系统的特定扰动如何影响多发性硬化症疾病过程提供了独特的机会。该项目的目标是仔细研究多发性硬化症 I/II 期临床试验中应用新型治疗药物引起的生物扰动，以确定中枢神经系统组织损伤的机制，以及有益免疫调节和免疫介导的神经保护的机制。通过将生物系统中测量到的变化（例如 T 细胞或其他免疫细胞亚群的不同功能）与中枢神经系统破坏或修复的结构变化（通过神经影像学方式测量）以及临床结果相关联，我们可以了解哪些生物过程在 MS 发病机制中是有益的，哪些是有害的。此外，了解应用疗法的哪些作用是其治疗益处的基础，将使我们能够定义指示性的生物标志物，并且理想情况下还可以预测完整的治疗反应。我们目前正在研究新药 (IND) 申请（PI，Bibiana Bielekova）下进行的 3 项研究者发起的 I/II 期临床试验中，研究三种治疗药物的免疫调节特性：达克珠单抗、艾地苯醌和利妥昔单抗。我们的结果简要总结如下： Daclizumab 是一种针对 CD25 的人源化单克隆抗体，CD25 是 IL-2 受体 (IL-2R) 的 α 链。 CD25 在活化的 T 细胞上高度上调，并且 CD25 对高亲和力 IL-2 信号传导的贡献被认为对于效应 T 细胞的扩增至关重要。因此，预期达珠单抗治疗将导致T细胞功能的抑制。之前我们已经证明达珠单抗在抑制 MS 相关炎症活动方面非常有效。然而，这种治疗效果与 T 细胞的抑制并不平行。相反，我们确定 daclizumab 选择性扩增 CD56bright 自然杀伤 (NK) 细胞，并且这种人类特异性 NK 细胞群通过其杀死活化的自体 T 细胞的能力而具有免疫调节功能。 CD56bright NK 细胞的扩增与治疗结果相关，表明它可以用作治疗反应的生物标志物。这一观察结果现已在 daclizumab 治疗多发性硬化症的双盲、安慰剂对照多中心 II 期试验中得到充分重现。我们继续在高炎症 MS 患者中进行 DAC-HYP（第二代 daclizumab）新 I 期开放标签治疗试验（方案 10-N-0125）中研究 daclizumab 在 MS 中的作用机制（MOA），目的是确定 daclizumab 对人类免疫系统的所有影响。我们确定 daclizumab 以 IL-2 依赖性方式矛盾地扩增 CD56bright NK 细胞；由于达珠单抗可防止激活的 T 细胞消耗 IL-2，因此 CD56bright NK 细胞可以通过中等亲和力的 IL-2 受体利用过量的 IL-2。此外，我们确定了 CD56bright NK 细胞杀死活化 T 细胞的机制，描述我们新发现的论文目前正在审查中。我们还确定达珠单抗对先天免疫系统的其他细胞有影响，特别是对成熟的树突状细胞。描述该 MOA 的论文目前也在审查中。 艾地苯醌是辅酶 Q (CoQ) 的脂溶性合成类似物。因此，它既可以改善线粒体代谢，又具有抗氧化作用。原发性进行性多发性硬化症 (PP-MS) 对免疫调节剂治疗有抵抗力。线粒体功能障碍与氧化应激相结合已被认为是 PP-MS 病理生理学的最重要的替代假设之一。因此，我们启动了艾地苯醌与安慰剂的双盲 I/II 期临床试验（方案 09-N-0197），以测试线粒体功能障碍和氧化应激是否会导致 PP-MS 神经功能障碍的发生。通过对入组患者的 PBMC 功能和 CSF 生物标志物进行离体分析，测量艾地苯醌鞘内抑制氧化应激的功效及其尚未探索的免疫调节作用。 利妥昔单抗是一种消耗 B 细胞的嵌合单克隆抗体，对有血脑屏障 (BBB) 破坏证据的患者的 MS 疾病活动具有抑制作用。目前的主要假设是 B 细胞与抗原特异性 T 细胞协作，并通过抗原呈递功能和相互共刺激支持 T 细胞激活。此外，有证据表明，在继发性进行性多发性硬化症 (SP-MS) 患者中，B 细胞和 T 细胞在脑沟深处形成三级淋巴滤泡。这些异位淋巴滤泡再现了鞘内腔内抗原特异性 T 细胞和 B 细胞的激活。不幸的是，由于大多数进行性多发性硬化症患者没有明显的 BBB 破坏，因此全身给药的利妥昔单抗中只有约 0.1% 能够进入 CNS 区室，这不足以耗尽 CNS B 细胞。因此，我们正在测试以下假设：SP-MS 患者鞘内注射利妥昔单抗将有效地消耗 CNS 室中的 B 细胞，这将转化为利妥昔单抗在低炎症 SP-MS 中的安慰剂对照 II 期试验中对 CNS 组织损伤生物标志物的治疗效果（方案 T-N-1235）。 虽然有许多药物具有生物学上合理的 MOA 来测试其对进行性多发性硬化症的疗效，但目前药物开发因我们没有敏感的中期结果指标而受到阻碍。因此，目前进行性多发性硬化症的 II 期研究需要招募数百名多发性硬化症患者，而且费用昂贵。我们的两项双盲安慰剂对照研究者发起的 II 期临床试验（即艾地苯醌和 IT 利妥昔单抗）具有相同的适应性试验设计，重点是评估不同（大多是新颖的）定量临床、功能和影像结果指标。希望这两项研究收集的数据将有助于为未来进行性多发性硬化症的 II 期治疗试验定义新的、更有效的临床试验设计。