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）和阿尔茨海默病病理学的重要驱动因素 相关性痴呆（ADRD）在AD/ADRD患者和动物模型中的多条证据表明， 血管失调和脑和脑血管中纤维蛋白（FN）沉积是重要来源 这种炎症。在AD/ADRD患者中，局部BBB破坏是早期事件， 疾病进展。血管破裂导致血蛋白外渗，包括纤维蛋白原 (FGN)在脑实质和脑血管中形成FN凝块， Aβ斑块和炎性免疫细胞。在FGN转化为FN的过程中，隐藏表位暴露在 FN γ链该序列（Fibγ377-395，也称为FN P2）是CD 11b/CD 18受体的配体 对巨噬细胞和小胶质细胞，触发激活这些先天免疫细胞和分泌炎性 调解员FGN的遗传或化学缺失或FN P2内6个关键氨基酸的遗传取代， AD的5xFAD小鼠模型显著降低了它们的炎性细胞因子水平， 认知能力下降小鼠单克隆抗体（mAb），5 B8，由Katerina Akassoglou博士（创始人）发现 Therini Bio Inc.）结合该隐蔽表位并重现遗传FN P2缺失的活性。5 B8是 对FN的选择性高于FGN，不干扰正常凝血。Therini生物公司人性化了 5 B8，并证明了称为THN 227的前导人源化抗FN P2 mAb保留了选择性结合 FN优于FGN，并且不干扰正常FN介导的功能，如止血。在体内 THN 227的静脉内给药的神经炎症的阿托洛尔（gen）诱导的脑脊髓炎模型 减少小胶质细胞活化、巨噬细胞浸润和氧化应激。在这个提议中， 抗FN P2 mAb将在几项关键临床前和非临床安全性研究中进行检测，以确保抗体 在人体临床试验中是安全和可耐受的。在启动拟议研究之前，我们将测试 THN 227和几种备用人源化或全人抗FN P2 mAb在免疫原性的离体测定中的应用 以及啮齿动物PK和剂量范围探索研究。在本提案中，我们将首先测试我们的铅抗FN P2 mAb在转基因AD小鼠模型中诱导微囊化。这是一个重要的安全测试，因为几个 抗A β单克隆抗体诱导的淀粉样蛋白相关影像学异常伴出血（ARIA-H）亚组 AD患者在以前的临床试验。我们还将确定非人灵长类动物（NHP）的安全剂量范围 并评估短期和长期重复给药方案的安全性。这些关键的安全研究将推动 我们新的抗FN P2 mAb方法的临床前开发，建立了重要的安全性限制， 支持IND申请并为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.