Metachromatic Leukodystrophy Enzyme Drug Development

描述(申请人提供)：异染性脑白质营养不良(MLD)是一种遗传性疾病，由编码溶酶体酶芳基硫酸酯酶A(ASA)的基因突变引起。包括神经退化和智力低下在内的症状会在婴儿期或儿童期出现；早期死亡可能是由于大脑中的器官损伤。酶替代疗法(ERT)不能治疗大脑，因为重组ASA不能越过血脑屏障(BBB)。因此，对患有MLD和重组ASA的儿童的临床试验已被放弃。目前的工作将重新设计人类ASA，以使用分子特洛伊木马技术实现跨血脑屏障的传输。分子特洛伊木马是一种针对内源性BBB多肽受体(如人胰岛素受体(HIR))的基因工程模拟肽单抗(MAb)。人的AsA与HIRMAb的重链融合，产生一种新的化学实体，称为HIRMAb-AsA融合蛋白。HIRMAb-ASA融合蛋白的可行性研究是在克隆了一个高产、稳定转染的宿主细胞系之后进行的。HIRMAb-AsA融合蛋白具有较高的AsA酶活性和与HIR的高结合力。这项I期SBIR工作将使用AsA酶活性分析和共聚焦显微镜进一步验证HIRMAb-ASA融合蛋白在MLD成纤维细胞中的药理活性。HIRMAb-ASA融合蛋白在体内对血脑屏障的渗透将在恒河猴身上得到证实。这项工作为未来的第二阶段研究提供了理论基础，这些研究为后续的GMP/GLP工作提供了桥梁，支持使用HIRMAb-ASA融合蛋白治疗MLD的IND。 公共卫生相关性：异色性脑白质营养不良症(MLD)是一种遗传性疾病，由编码溶酶体酶A(AsA)的基因突变引起。酶替代疗法不能治疗大脑，因为重组的ASA不能越过血脑屏障。目前的工作将重新设计人类ASA，以使用分子特洛伊木马技术实现跨血脑屏障的传输。

DESCRIPTION (provided by applicant): Metachromatic leukodystrophy (MLD) is an genetic disease caused by mutations in the gene encoding the lysosomal enzyme, arylsulfatase A (ASA). Symptoms including neurodegeneration and mental retardation appear during infancy or childhood; and early death can occur due to organ damage in the brain. Enzyme replacement therapy (ERT) cannot treat the brain, since recombinant ASA does not cross the blood-brain barrier (BBB). Accordingly, clinical trials of children with MLD and recombinant ASA have been abandoned. The present work will re-engineer human ASA to enable transport across the BBB using a molecular Trojan horse technology. A molecular Trojan horse is a genetically engineered peptidomimetic monoclonal antibody (MAb) against an endogenous BBB peptide receptor, such as the human insulin receptor (HIR). The human ASA is fused to the heavy chain of the HIRMAb to create a new chemical entity, called the HIRMAb-ASA fusion protein. Feasibility studies with the HIRMAb-ASA fusion protein were enabled following the cloning of a high producing, stably transfected host cell line. The HIRMAb-ASA fusion protein retains high ASA enzyme activity and high binding to the HIR. This phase I SBIR work will further validate the pharmacologic activity of the HIRMAb-ASA fusion protein in MLD fibroblasts, using ASA enzyme activity assays and confocal microscopy. The HIRMAb-ASA fusion protein penetration of the BBB in vivo will be confirmed in the Rhesus monkey. This work provides the rationale for future phase II studies that provide the bridge to subsequent GMP/GLP work that supports an IND for treatment of MLD with the HIRMAb-ASA fusion protein. PUBLIC HEALTH RELEVANCE: Metachromatic leukodystrophy (MLD) is an genetic disease caused by mutations in the gene encoding the lysosomal enzyme, arylsulfatase A (ASA). Enzyme replacement therapy cannot treat the brain, since recombinant ASA does not cross the blood-brain barrier. The present work will re- engineer human ASA to enable transport across the BBB using a molecular Trojan horse technology.