Przybilla Michael J, Stewart Christine, Carlson Timothy W, Ou Li, Koniar Brenda L, Sidhu Rohini, Kell Pamela J, Jiang Xuntian, Jarnes Jeanine R, O'Sullivan M Gerard, Whitley Chester B
Gene Therapy Center, Department of Pediatrics, University of Minnesota, Minneapolis, MN, USA.
Research Department, Tanabe Research Laboratories U.S.A., Inc, San Diego, CA, USA.
Mol Genet Metab Rep. 2021 Mar 25;27:100748. doi: 10.1016/j.ymgmr.2021.100748. eCollection 2021 Jun.
GM1-gangliosidosis is a lysosomal disease resulting from a deficiency in the hydrolase β-galactosidase (β-gal) and subsequent accumulation of gangliosides, primarily in neuronal tissue, leading to progressive neurological deterioration and eventually early death. Lysosomal diseases with neurological involvement have limited non-invasive therapies due to the inability of lysosomal enzymes to cross the blood-brain barrier (BBB). A novel fusion enzyme, labeled mTfR-GLB1, was designed to act as a ferry across the BBB by fusing β-gal to the mouse monoclonal antibody against the mouse transferrin receptor and tested in a murine model of GM1-gangliosidosis (β-gal). Twelve hours following a single intravenous dose of mTfR-GLB1 (5.0 mg/kg) into adult β-gal mice showed clearance of enzyme activity in the plasma and an increase in β-gal enzyme activity in the liver and spleen. Long-term efficacy of mTfR-GLB1 was assessed by treating β-gal mice intravenously twice a week with a low (2.5 mg/kg) or high (5.0 mg/kg) dose of mTfR-GLB1 for 17 weeks. Long-term studies showed high dose mice gained weight normally compared to vehicle-treated β-gal mice, which are significantly heavier than heterozygous controls. Behavioral assessment at six months of age using the pole test showed β-gal mice treated with mTfR-GLB1 had improved motor function. Biochemical analysis showed an increase in β-gal enzyme activity in the high dose group from negligible levels to 20% and 11% of heterozygous levels in the liver and spleen, respectively. Together, these data show that mTfR-GLB1 is a catalytically active β-gal fusion enzyme that is readily taken up into tissues. Despite these indications of bioactivity, behavior tests other than the pole test, including the Barnes maze, inverted screen, and accelerating rotarod, showed limited or no improvement of treated mice compared to β-gal mice receiving vehicle only. Further, administration of mTfR-GLB1 was insufficient to create measurable increases in β-gal enzyme activity in the brain or reduce ganglioside content (biochemically and morphologically).
GM1神经节苷脂贮积症是一种溶酶体疾病，由水解酶β-半乳糖苷酶（β-gal）缺乏以及随后神经节苷脂主要在神经组织中蓄积所致，会导致进行性神经功能恶化并最终过早死亡。由于溶酶体酶无法穿过血脑屏障（BBB），累及神经系统的溶酶体疾病的非侵入性治疗方法有限。一种新型融合酶，标记为mTfR-GLB1，通过将β-gal与抗小鼠转铁蛋白受体的小鼠单克隆抗体融合而设计，用作穿过血脑屏障的载体，并在GM1神经节苷脂贮积症（β-gal）的小鼠模型中进行了测试。对成年β-gal小鼠单次静脉注射mTfR-GLB1（5.0mg/kg）12小时后，血浆中的酶活性清除，肝脏和脾脏中的β-gal酶活性增加。通过每周两次静脉注射低剂量（2.5mg/kg）或高剂量（5.0mg/kg）的mTfR-GLB1，对β-gal小鼠进行17周的治疗，评估mTfR-GLB1的长期疗效。长期研究表明，与接受赋形剂治疗的β-gal小鼠相比，高剂量组小鼠体重正常增加，而接受赋形剂治疗的β-gal小鼠明显比杂合子对照重。在6个月大时使用杆试验进行行为评估，结果显示接受mTfR-GLB1治疗的β-gal小鼠运动功能有所改善。生化分析表明，高剂量组肝脏和脾脏中的β-gal酶活性分别从可忽略不计的水平增加到杂合子水平的20%和11%。总之，这些数据表明mTfR-GLB1是一种具有催化活性的β-gal融合酶，很容易被组织摄取。尽管有这些生物活性指标，但除杆试验外的其他行为测试，包括巴恩斯迷宫试验、倒屏试验和加速转棒试验，结果显示与仅接受赋形剂的β-gal小鼠相比，治疗小鼠的改善有限或没有改善。此外，给予mTfR-GLB1不足以使大脑中的β-gal酶活性产生可测量的增加，也无法降低神经节苷脂含量（生化和形态学方面）。
