Novel Protein Engineered Drug Conjugates Targeting Phosphatidylserine for the Treatment of Breast Cancer

7.项目总结/摘要 仍然迫切需要推动高度选择性和有效的 用于治疗转移性和三阴性乳腺癌的治疗剂。该提案提出了一个 创新和有前途的战略，重点是第一次合成和评价betabody-药物缀合物 在一些实施方案中，靶向磷脂酰丝氨酸（PS）的工程化蛋白质（称为β抗体）是BDC的特征。PS 选择性地暴露在癌细胞和内皮细胞的质膜的外叶上， 肿瘤微环境中，但限于正常细胞的质膜的内叶。这 为选择性靶向有效的小分子抗癌有效载荷（KGP 18）提供了极好的机会 和KGP 156）对肿瘤微环境的影响。β抗体更小，允许更好的肿瘤穿透 与先前评估的PS选择性抗体相比，其表现出在 脉管系统BDC被设计为通过酶选择性地在细胞外释放KGP 18和KGP 156 （组织蛋白酶B、尿激酶型纤溶酶原激活物和纤溶酶），其被上调和/或显示 乳腺癌细胞和相关肿瘤血管系统的活性增强。KGP 18和KGP 156是有效的 微管蛋白聚合的抑制剂，并显示出双重作用机制， 抗增殖剂（细胞毒性在低nM至pM范围内）和作为深刻有效的血管破坏剂， 药物，其对肿瘤相关的脉管系统造成不可逆的损伤，最终导致肿瘤坏死。 这些合成的基于苯并环戊二烯的有效载荷（KGP 18和KGP 156）将在比较研究中进行评估 到单甲基-澳瑞他汀E（MMAE），其是许多临床相关抗体-药物组合物中的选择的有效载荷。 共轭应该注意的是，VDA在机制上不同于研究充分的血管生成 抑制剂。将研究两种单独的交付策略。KGP 18和KGP 156将被合成 用不同的、基于蛋白酶选择性肽的接头官能化， 在被肿瘤微环境中高水平存在的特异性蛋白酶切割之前是生物惰性的， 从而选择性地释放有效载荷（KGP 18或KGP 156）。在第二个战略中，将准备BDC， 从最好的药物-蛋白酶选择性接头构建体。假设是适当设计的药物连接体 构建体及其相应的与这些高效有效载荷（KGP 18或KGP 156）连接的BDC将 显示出对肿瘤血管和肿瘤细胞的高选择性。药代动力学研究将评估 从其相应的构建体和缀合物中释放效应药物。的功效和选择性， 这些药物-接头构建体和BDC将使用基于细胞的研究和建立的鼠模型进行评估。 原位乳腺癌模型（MDA-MB-231人异种移植物和同基因4 T1肿瘤）。概括起来就是 预期每种策略将导致肿瘤特异性药物递送和有效的抗肿瘤活性。

7. Project Summary/Abstract There remains an urgent, and largely unmet need for the advancement of highly selective and effective therapeutic agents for the treatment of metastatic and triple negative breast cancer. This proposal advances an innovative and promising strategy focused on the first time synthesis and evaluation of betabody-drug conjugates (BDCs), which feature engineered proteins (referred to as betabodies) that target phosphatidylserine (PS). PS is selectively exposed on the outer leaflet of the plasma membrane of cancer cells and endothelial cells in the tumor microenvironment, but is confined to the inner leaflet of the plasma membrane of normal cells. This provides an exquisite opportunity for selective targeting of potent small-molecule anticancer payloads (KGP18 and KGP156) to the tumor microenvironment. Betabodies are smaller allowing for better tumor penetration compared with previously evaluated PS-selective antibodies, which demonstrated poor distribution beyond the vasculature. BDCs are designed to selectively release KGP18 and KGP156 extracellularly by enzymes (cathepsin B, urokinase-type plasminogen activator, and plasmin) that are upregulated and/or demonstrate enhanced activity by breast cancer cells and associated tumor vasculature. KGP18 and KGP156 are potent inhibitors of tubulin polymerization and demonstrate dual mechanism of action functioning as remarkably active antiproliferative agents (cytotoxicity in low nM to pM range) and as profoundly effective vascular disrupting agents, which impart irreversible damage to tumor-associated vasculature ultimately leading to tumor necrosis. These synthetic benzosuberene-based payloads (KGP18 and KGP156) will be evaluated in comparative studies to monomethyl-auristatin E (MMAE), which is a payload of choice in many clinically relevant antibody-drug conjugates. It should be noted that VDAs are mechanistically distinct from the well-studied angiogenesis inhibiting agents. Two individual delivery strategies will be investigated. KGP18 and KGP156 will be synthetically functionalized with distinct, protease-selective peptide-based linkers rendering the drug-linker prodrug constructs biologically inert until cleaved by specific proteases that are present at high levels in the tumor microenvironment, thus selectively releasing the potent payload (KGP18 or KGP156). In a second strategy, BDCs will be prepared from the best drug-protease selective linker constructs. The hypothesis is that appropriately designed drug-linker constructs and their corresponding BDCs tethered to these highly potent payloads (KGP18 or KGP156) will demonstrate high selectivity for tumor vasculature and tumor cells. Pharmacokinetic studies will evaluate the release of the effector drugs from their corresponding constructs and conjugates. The efficacy and selectivity of these drug-linker constructs and BDCs will be evaluated using cell-based studies and established murine orthotopic breast cancer models (MDA-MB-231 human xenografts and syngeneic 4T1 tumors). In summary, it is expected that each strategy will result in tumor-specific drug delivery and potent anti-tumor activity.