Safety and Tolerability Studies for an Anti-Fibrin P2 Monoclonal Antibody for the Treatment of Alzheimer's Disease

摘要 神经炎症是阿尔茨海默病(AD)和阿尔茨海默病的重要病理驱动因素 相关痴呆症(ADRD)。在AD/ADRD患者和动物模型中的多条证据表明 脑血管内纤维蛋白(FN)的沉积和血管调节失调是其重要来源 这种炎症的症状。在AD/ADRD患者中，局限性的BBB破坏是一个早期事件，并随着 疾病的发展。血管破裂导致血液蛋白质外溢，包括纤维蛋白原。 (FGN)，进入脑内并在脑实质和脑血管形成FN凝块符合 Aβ斑块和炎性免疫细胞。在FGN到FN的转换中，一个隐秘的表位暴露在 Fn CD11b链这个序列(γ377-395，也称为FN P2)是CD11b/CD18R的配体 在巨噬细胞和小胶质细胞上，触发这些天然免疫细胞的激活和炎症的分泌 调解人。FGN的遗传或化学耗竭或FN P2中6个关键氨基酸的遗传替代 5xFAD小鼠模型显著降低其炎性细胞因子水平和 认知能力下降。由Katerina Akassoglou博士(创始人)发现的鼠单抗5B8 (Therini Bio Inc.)结合这个神秘的表位，并概括了遗传的FN P2缺失的活性。5B8是 对FN的选择性高于FGN，不会干扰正常的凝血。Therini Bio Inc.将人性化 5B8，证明了铅人源化抗FN P2单抗THN227保留了选择性结合 对于FN，而不是FGN，并且不干扰FN介导的正常功能，如止血。在活体内 静脉注射THN227诱导神经炎性脑脊髓炎模型的建立 减少小胶质细胞活化、巨噬细胞渗透和氧化应激。在这项提议中，主角变得人性化 抗FN P2单抗将在几项关键的临床前和非临床安全性研究中进行测试，以确保抗体 对人体临床试验是安全和可耐受的。在启动拟议的研究之前，我们将测试 THN227和几种人源化或全人化抗FN P2单抗的体外免疫原性检测 以及在啮齿动物PK和剂量范围寻找研究中。在这项提案中，我们将首先测试我们的领先抗FN P2 单抗在转基因AD小鼠模型中诱导微出血。这是一项重要的安全测试，因为有几项 抗A-β单抗诱导的出血相关淀粉样蛋白相关影像异常(ARIA-H) 在之前的临床试验中，阿尔茨海默病患者的比例很高。我们还将建立非人类灵长类动物(NHP)的安全剂量范围。 并评估重复短期和长期给药方案的安全性。这些关键的安全研究将推动 我们新的抗FN P2单抗方法的临床前开发，建立了重要的安全限制， 支持IND应用，并为AD/ADRD早期临床试验的合理设计提供信息。

ABSTRACT Neuroinflammation is a significant driver of pathology in Alzheimer’s disease (AD) and Alzheimer’s disease related dementia (ADRD). Multiple lines of evidence in patients and in animal models of AD/ADRD point to vascular dysregulation and deposits of fibrin (FN) in the brain and cerebral blood vessels as significant sources of this inflammation. In AD/ADRD patients localized BBB breakdown is an early event and increases with disease progression. Vascular breakdown leads to the extravasation of blood proteins, including fibrinogen (FGN), into the brain and the formation of FN clots in brain parenchyma and cerebral vasculature coincident with Aβ plaques and inflammatory immune cells. In the conversion of FGN to FN a cryptic epitope is exposed on the FN  chain This sequence (Fibγ377-395, also known as FN P2) is a ligand for the CD11b/CD18 receptor on macrophages and microglia, triggering activation of these innate immune cells and secretion of inflammatory mediators. Genetic or chemical depletion of FGN or genetic substitution of 6 key amino acids within FN P2 in the 5xFAD mouse model of AD considerably reduces their level of inflammatory cytokines and the rate of cognitive decline. A mouse monoclonal antibody (mAb), 5B8, discovered by Dr. Katerina Akassoglou (founder of Therini Bio Inc.) binds this cryptic epitope and recapitulates the activity of the genetic FN P2 deletion. 5B8 is highly selective for FN over FGN and does not interfere with normal coagulation. Therini Bio Inc. has humanized 5B8 and demonstrated that the lead humanized anti-FN P2 mAb, termed THN227, retains the selective binding for FN over FGN and does not interfere with normal FN-mediated functions such as hemostasis. In an in vivo fibrino(gen)-induced encephalomyelitis model of neuroinflammation, intravenous administration of THN227 reduced microglial activation, macrophage infiltration, and oxidative stress. In this proposal the lead humanized anti-FN P2 mAb will be tested in several key preclinical and nonclinical safety studies to ensure that the antibody is safe and tolerable for human clinical trials. Prior to the initiation of the proposed studies, we will have tested THN227 and several back-up humanized or fully human anti-FN P2 mAbs in ex vivo assays of immunogenicity and in rodent PK and dose range finding studies. In this proposal, we will first test whether our lead anti-FN P2 mAb induces microhemorrhages in a transgenic AD mouse model. This is an important safety test, as several anti-Aβ mAbs induced amyloid related imaging abnormalities associated with hemorrhage (ARIA-H) in a subset of AD patients in previous clinical trials. We will also establish the safe dose range in nonhuman primates (NHPs) and assess the safety or repeated short-term and chronic dose regimens. These key safety studies will drive the preclinical development of our novel anti-FN P2 mAb approach, establish important safety limitations, supporting an IND application and informing the rational design of early stage clinical trials in AD/ADRD.