Recombinant Enzyme Fusion Protein for Lysosomal Storage Disorders

摘要溶酶体贮积性疾病有40多种，这些疾病大多对中枢神经系统（CNS）产生不良影响。主要的治疗方法是酶替代疗法（ERT）。然而，ERT对大脑没有效果，因为酶不能穿过脑毛细血管壁，这在体内形成血脑屏障（BBB）。如果不治疗中枢神经系统，年轻患者注定会发生进行性神经变性和死亡。未来治疗这些疾病的限制因素是酶在血脑屏障上的转运。直接注射到大脑的血脑屏障旁路是无效的，因为只有一小部分大脑被经颅输送系统治疗。相反，几乎所有的大脑细胞都可以通过静脉给药的跨血管输送系统来治疗，该系统使酶能够穿过血脑屏障。分子特洛伊木马技术是一种将诸如酶之类的大分子输送到血脑屏障的新方法。通过基因工程，将缺失的重组酶与血脑屏障分子特洛伊木马融合，产生了一种双功能融合蛋白。后者是一种基因工程蛋白，能够通过受体介导的内源性血脑屏障肽转运系统的胞吞作用穿过人血脑屏障。临床前研究表明，一种分子量为10万道尔顿的大酶，可以通过血脑屏障的运输，附着在血脑屏障受体特异性的特洛伊木马上，进入大脑。目前的工作将产生一种新的融合基因编码溶酶体酶和一个基因工程分子特洛伊木马，这将允许生产相应的融合蛋白AGT-180。融合基因将被纳入真核表达载体，然后永久转染细胞。这些II期研究将使主细胞库的生产和融合蛋白的纯化和下游加工的发展成为可能。由血脑屏障靶向抗体和重组酶组成的融合蛋白可用于人脑溶酶体贮积症的治疗。溶酶体贮积症是一种严重的先天性代谢错误，约有75%的溶酶体贮积症影响大脑。主要的治疗方法是酶替代疗法（ERT）。然而，ERT在大脑中无效，因为酶不能穿过血脑屏障（BBB）。目前的工作将产生一种新的重组融合蛋白，它能够(a)结合人类血脑屏障受体触发转运进入大脑，(b)保持高溶酶体酶活性。这种名为AGT-180的新药将成为治疗多种遗传疾病的典范。1

DESCRIPTION (provided by applicant): Zhang, Yun Abstract There are over 40 lysosomal storage disorders, and most of these diseases affect adversely the central nervous system (CNS). The mainstay of treatment is enzyme replacement therapy (ERT). However, ERT is not effective for the brain, because the enzymes do not cross the brain capillary wall, which forms the blood-brain barrier (BBB) in vivo. Without treatment of the CNS, the young patients are destined to progressive neurodegeneration and death. The limiting factor in the future treatment of these diseases is the transport of the enzyme across the BBB. Bypass of the BBB with direct injection into the brain is not effective, because only a small part of the brain is treated with a trans-cranial delivery system. Conversely, virtually all cells of the brain can be treated with a trans-vascular delivery system that enables the enzyme to cross the BBB following intravenous administration. A new approach to the BBB delivery of large molecules such as enzymes is the molecular Trojan horse technology. A bi-functional fusion protein is produced with genetic engineering, wherein the missing recombinant enzyme is fused to a BBB molecular Trojan horse. The latter is a genetically engineered protein that is able to cross the human BBB by receptor- mediated transcytosis on endogenous BBB peptide transport systems. Pre-clinical studies show that a large enzyme with a molecular weight >100,000 Daltons, can be delivered to brain via transport across the BBB, following attachment to a BBB receptor-specific Trojan horse. The present work will produce a novel fusion gene encoding a lysosomal enzyme and a genetically engineered molecular Trojan horse, which will allow the production of the corresponding fusion protein, AGT-180. The fusion gene will be incorporated in a eukaryotic expression vector followed by permanent transfection of cells. These phase II studies will enable production of a master cell bank and development of the purification and downstream processing of the fusion protein. Fusion proteins comprised of BBB targeting antibodies and recombinant enzymes could be therapeutic in the treatment of the brain in human lysosomal storage disorders. 1 Zhang, Yun Project Narrative Lysosomal storage disorders are serious inborn errors of metabolism, and about 75% of the ~40 lysosomal storage disorders affect the brain. The mainstay of treatment is Enzyme Replacement Therapy (ERT). However, ERT is ineffective in the brain, because the enzymes do not cross the blood-brain barrier (BBB). The present work will produce a novel recombinant fusion protein that is able to both (a) bind a human BBB receptor to trigger transport into the brain, and (b) retain high lysosomal enzyme activity. This novel drug, designated AGT-180, will be a model for the treatment of the brain for multiple genetic diseases. 1