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 薄壁组织这减弱了大脑对全身给药药物的暴露水平，特别是大剂量的- 大小分子，如抗体。这一问题也使得胶质母细胞瘤（GBM）的全身治疗成为最重要的治疗方法。 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GBM细胞，特别是浸润性肿瘤区域生长边缘附近的细胞 在一个完好的血脑屏障后面总的来说，血脑屏障的特征对有效治疗脑梗死提出了特殊的挑战。 中枢神经系统（CNS）疾病，包括脑癌，使用在其他疾病中已证明有效的药物 疾病 抗体-药物偶联物（Antibody-drug conjugates，ADC）是一类新兴的药物，具有突出的靶向特异性、持久的生物相容性和生物相容性。 治疗效果和在药物开发中的高可转化性。虽然有希望，但ADC在以下方面的临床益处 脑疾病，特别是GBM的治疗仍然未经证实。不幸的是，最近的中期分析 在一项使用抗EGFRvIII ADC Depatux-M（以前称为ABT-414）的3期研究中， 新诊断的GBM患者接受该ADC治疗获益。因此，改善血脑屏障渗透性， 目前迫切需要ADC将这种有前途的分子形式推向真正有效和安全的系统性治疗。 治疗CNS疾病。 我们已经开发了新的ADC接头技术，包括：1）用于位点特异性的分支接头， 将两个不同的分子同时安装到单个抗体上，和2）酶促可裂解的接头 具有卓越的循环稳定性。利用这些技术，我们成功地建造了 均质缀合物附加有肽，其促进通过受体介导的 转胞吞作用与常规的异质肽缀合物相比， 在健康小鼠（2.7倍）和原位GBM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， 适当设计的BBB穿透肽与ADC的缀合将是一种有前途的方法， 全身药物输送到大脑。本项目将制备多种血脑屏障穿透肽， 构建具有各种缀合模式（接头连接位点、接头结构和接头连接位点）的抗体缀合物。 肽和有效载荷的化学计量）。将在体外和体内评价所有结合物的血浆 稳定性、受体介导的转胞吞作用效率、药代动力学、生物分布、耐受性和 免疫原性特征。然后，我们将评估一组BBB可渗透ADC的肿瘤靶向效率 以及在基于细胞系和患者来源的原位移植瘤小鼠模型中的治疗功效 GBM。我们还将进行活体荧光显微镜检查，以评估 在健康和荷瘤小鼠模型中均观察到外渗。 本项目的成功完成将阐明肽结构和偶联方式的影响 对抗体缀合物的BBB渗透性以及其他药物性质的影响。我们也希望能找出合理的 分子设计，释放单克隆抗体和ADC的全部治疗潜力， 靶向，这可能最终导致新的药物开发策略，以治愈难以治疗的疾病。 CNS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.