Chemical approaches for generating blood-brain barrier-permeable antibody conjugates

1.摘要 血脑屏障(BBB)限制生物分子从血管系统流入大脑 薄壁组织。这会降低大脑对全身用药的暴露水平，特别是大剂量药物。 确定抗体等分子的大小。这一问题也使得系统治疗胶质母细胞瘤(GBM)成为最 毁灭性的脑癌，在大多数情况下无效。最近的临床研究表明， 存在可测量数量的基底膜细胞，特别是浸润性肿瘤区域生长边缘附近的细胞。 在一个完好无损的血脑屏障后面。总体而言，血脑屏障的特点为有效治疗红斑狼疮创造了特殊的挑战。 中枢神经系统(CNS)疾病，包括脑癌，使用已被证明对其他疾病有效的药物 疾病。 抗体-药物结合物是一类新兴的药物，具有显著的靶向性、耐受性。 治疗效果，在药物开发中具有高度的可译性。虽然前景看好，但ADC的临床好处 脑部疾病的治疗，特别是基底膜的治疗，仍然没有得到证实。不幸的是，最近的中期分析 在使用抗EGFRvIII ADC的3期研究中，Depatux-M(以前称为ABT-414)显示没有存活 对接受此ADC的新诊断的GBM患者的好处。因此，血脑屏障渗透性的改善 ADC是推动这种有前景的分子形式向真正有效和安全的系统发展的关键 中枢神经系统疾病的治疗。 我们开发了新的ADC链接器技术，包括：1)针对特定部位和 同时将两个不同的分子安装到单个抗体和2)酶可切割的连接物上 具有极佳的循环稳定性。使用这些技术，我们成功地构建了 均相结合的多肽通过受体介导促进血脑屏障的穿透 细胞穿透。一种均相多肽结合物，与传统的多相多肽结合物相比 变种，在健康小鼠(2.7倍)和原位GBM中显示更多的积聚到脑实质中 异种移植小鼠模型中的肿瘤(3.6倍)。基于这些发现，我们假设同质的 设计合理的BBB穿透性多肽与ADC的偶联将是一种很有前途的方法 全身性药物输送到大脑。在这个项目中，我们将制备各种穿透血脑屏障的多肽和 构建具有不同连接方式(连接物连接部位、连接物结构和 多肽和有效载荷的化学计量)。所有的结合物都将在体外和体内进行血浆检测。 稳定性、受体介导的细胞穿透效率、药代动力学、生物分布、耐受性和 免疫原性图谱。然后，我们将评估一组血脑屏障通透性ADC的肿瘤靶向效率 以及对基于细胞系和患者来源的异种小鼠原位移植模型的治疗效果 GBM。我们还将进行活体荧光显微镜检查，以评估动力学和动力学 健康和荷瘤小鼠模型中的渗出。 该项目的成功完成将阐明多肽结构和结合方式的影响 对抗体结合物的血脑屏障穿透性以及其他药物性质的影响。我们还希望确定理性的 分子设计以充分释放单抗和ADC对脑的治疗潜力 靶向，这最终可能导致新的药物开发战略，以治愈难以治疗的疾病 中枢神经系统疾病，如GBM。

1. ABSTRACT The blood-brain barrier (BBB) restricts the influx of biomolecules from the vasculature to the brain parenchyma. This attenuates exposure levels of the brain to systemically administered drugs, especially large- size molecules such as antibodies. This issue also makes systemic treatment of glioblastoma (GBM), the most devastating brain cancer, ineffective in most cases. Recent clinical studies have demonstrated that a measurable number of GBM cells, in particular cells near the growing edge of the infiltrative tumor area, exist behind an intact BBB. Collectively, the features of the BBB create a special challenge for effective treatment of central nervous system (CNS) diseases, including brain cancer, using drugs that have proven efficacy in other diseases. Antibody-drug conjugates (ADCs) are an emerging drug class with prominent target specificity, durable therapeutic efficacy, and high translatability in drug development. While promising, clinical benefits of ADCs in the treatment of brain diseases, in particular GBM, remain unconfirmed. Unfortunately, recent interim analysis in a Phase 3 study using the anti-EGFRvIII ADC Depatux-M (formerly called ABT-414) revealed no survival benefit for patients with newly diagnosed GBM receiving this ADC. Thus, improvement in BBB penetrability for ADCs is critically needed to advance this promising molecular format toward truly effective and safe systemic therapy for CNS diseases. We have developed novel ADC linker technologies, including: 1) branched linkers for site-specific and simultaneous installation of two distinct molecules onto a single antibody and 2) enzymatically cleavable linkers with exceptional circulation stability. Using these technologies, we have successfully constructed homogeneous conjugates appended with peptides that facilitate traversing the BBB through receptor-mediated transcytosis. One of the homogeneous peptide conjugates, as compared to a conventional heterogeneous variant, showed greater accumulation into the brain parenchyma in healthy mice (2.7-fold) and orthotopic GBM tumors in a xenograft mouse model (3.6-fold). Based on these findings, we hypothesize that homogeneous conjugation of properly designed BBB-penetrating peptides with ADCs will be a promising approach for systemic drug delivery to the brain. In this project, we will prepare a variety of BBB-penetrating peptides and construct antibody conjugates with various conjugation modalities (linker attachment site, linker structure, and stoichiometry of the peptides and payloads). All conjugates will be evaluated in vitro and in vivo for plasma stability, receptor-mediated transcytosis efficiency, pharmacokinetics, biodistribution, tolerability, and immunogenicity profiles. We will then evaluate a panel of BBB-permeable ADCs for tumor targeting efficiency as well as therapeutic efficacy in cell line-based and patient-derived xenograft mouse models of orthotopic GBM. We will also perform intravital fluorescence microscopy to evaluate kinetics and dynamics of extravasation in both healthy and tumor-bearing mouse models. Successful completion of this project will clarify the effect of the peptide structure and conjugation modality on BBB penetrability of antibody conjugates as well as other drug properties. We also expect to identify rational molecular design to unleash the full therapeutic potential of monoclonal antibodies and ADCs for brain targeting, which may ultimately lead to novel drug development strategies toward a cure for difficult-to-treat CNS diseases, such as GBM.