CD98hc Brain Shuttles for Delivering Off-the-shelf Neuroprotective Antibodies in Alzheimer's Disease

阿尔茨海默病(AD)是最常见的与年龄相关的神经退行性疾病。具有潜力的生物制品 影响潜在的病理生理学，在临床上未能显示出显著的治疗效果。这个 生物制剂无法穿透血脑屏障(BBB)是其临床疗效的最大障碍。 解决这一挑战的一个有希望的策略是将IGGS融合到第二个亲和配体上，该配体与 脑血管内皮细胞靶向并诱导跨血脑屏障转运。虽然几乎所有先前的努力都已经 集中在转铁蛋白受体(TFR-1)作为典型的内皮靶标，尽管固有的递送和 安全挑战，我们已经开发出一种双特异性抗体穿梭载体，它与CD98hc重链结合 大的中性氨基酸转运体(LAT-1)。值得注意的是，我们的初步数据显示， 我们第一代CD98hc双特异性航天飞机高级大脑中整合的现成免疫球蛋白的特异性 与TFR-1相比，保留通过CD98hc穿梭的IgG，并保留CD98hc和TFR-1的内皮水平 饱和CD98hc穿梭剂量后的脑摄取。这项提议的总体目标是进一步 CD98hc BBB穿梭机的研制：I)确定最大免疫球蛋白脑的最佳特性 实质转运；ii)评估年龄和疾病对CD98hc介导的转运的影响；以及iii) 使用激动剂(抗TrkB)和拮抗剂(抗TrkB)在AD小鼠模型中生成概念验证有效性数据 磷酸)抗体单独和组合。我们的中心假设是免疫球蛋白通过CD98hc转运 航天飞机将增加实质的输送，并实现大脑集中和目标参与 可与病毒传递相媲美，在tau小鼠模型中产生强大的神经保护，包括潜在的添加剂 或通过针对两种不同的神经保护途径发挥协同神经保护作用。因此，我们建议 目的1优化第二代CD98hc抗体穿梭载体的脑实质递送。我们将测试 CD98hc相互作用的价态、亲和力和表位对脑摄取和实质递送的影响。 用成年小鼠确定的最佳剂量和结构将在老年野生型和PS19(Tau P301S)中进行测试 以评估小鼠转运途径的完整性。接下来，在目标2中，我们将评估个人的效能 神经保护性抗体/CD98hc在PS19小鼠体内穿梭。经验证的TrkB抗体(C20，激动剂)和 磷酸化tau(PHF1)将通过我们最好的CD98hc航天飞机单独运送。疗效结果将是 磷酸化和不溶性tau的水平，神经元和突触丢失，以及认知缺陷。功效将是 在三种治疗模式下进行测试，从AD进展的早期、中期和晚期开始 病理学和认知功能衰退。最后，在目标3中，抗体穿梭靶向组合的有效性 将对PS19小鼠的多种神经保护途径进行评估。这些研究有望提供新的 与CD98hc转运通路相关的基础知识和双特异性AD的临床前数据 治疗学，包括针对机械上独特的神经保护途径的联合疗法。

Alzheimer’s disease (AD) is the most common age-related neurodegenerative disease. Biologics with potential to affect underlying pathophysiology have failed to display significant therapeutic benefits in the clinic. The inability of biologics to penetrate the blood-brain barrier (BBB) represents their biggest hurdle to clinical efficacy. A promising strategy to address this challenge is to fuse IgGs to a second affinity ligand that engages a cerebrovascular endothelial target and induces transport across the BBB. While nearly all prior efforts have focused on the transferrin receptor (TfR-1) as the prototypical endothelial target despite inherent delivery and safety challenges, we have developed a bispecific antibody shuttle that engages CD98hc, the heavy chain of the large neutral amino acid transporter (LAT-1). Notably, our preliminary data show preserved affinity and specificity of off-the-shelf IgGs incorporated into our first-generation CD98hc bispecific shuttle, superior brain retention of IgGs shuttled via CD98hc as compared to TfR-1, and preserved endothelial levels of CD98hc and brain uptake after saturating CD98hc shuttle doses.The overall objective of this proposal is to further the development of the CD98hc BBB shuttle by: i) defining the optimal characteristics for maximal IgG brain parenchymal delivery; ii) evaluating age- and disease-dependent effects on CD98hc-mediated transport; and iii) generating proof-of-concept efficacy data in an AD mouse model using agonist (anti-TrkB) and antagonist (anti- phospho-tau) antibodies alone and in combination. Our central hypothesis is that IgG transport via the CD98hc shuttles will increase parenchymal delivery and achieve brain concentrations and target engagement comparable to viral delivery, generating robust neuroprotection in a tau mouse model, including potential additive or synergistic neuroprotective effects by targeting two different neuroprotective pathways. Therefore, we propose in Aim 1 to optimize brain parenchymal delivery of a second-generation CD98hc antibody shuttle. We will test the impact of the valency, affinity, and epitope of CD98hc interaction on brain uptake and parenchymal delivery. The optimal dose and construct identified using adult mice will be tested in aged wild-type and PS19 (tau P301S) mice to evaluate the integrity of the transport pathway. Next, in Aim 2, we will assess the efficacy of individual neuroprotective antibody/CD98hc shuttles in PS19 mice. Validated antibodies against TrkB (C20, agonist) and phosphorylated tau (PHF1) will be individually delivered via our best CD98hc shuttle. Efficacy outcomes will be levels of phosphorylated and insoluble tau, neuronal and synaptic loss, and cognitive deficits. Efficacy will be tested in three modes of treatment, beginning at early, intermediate, and late stages of progression of AD pathology and cognitive decline. Finally, in Aim 3, the efficacy of combinations of antibody shuttles targeting multiple neuroprotective pathways in PS19 mice will be evaluated. These studies are expected to provide new fundamental knowledge related to the CD98hc transport pathway and preclinical data for bispecific AD therapeutics, including combination therapies that target mechanistically unique neuroprotective pathways.