CGT and ACD Inhibitors for SRT Treatment of Krabbe Disease

总结 Krabbe病（KD）是由广泛表达的溶酶体酶缺乏引起的 半乳糖神经酰胺酶（GALC），其负责半乳糖神经酰胺的降解， 半乳糖基鞘氨醇（psychosine）。因为导致精神病碱的合成途径不受 KD，精神病是不断产生和积累在克拉布神经系统。毒性水平 精神病被认为是疾病的主要致病触发因素。目前，KD的护理标准是 造血干细胞移植（HSCT），仅适用于无症状或早期症状 婴儿KD病例和仅延长疾病。使用腺相关病毒的临床前基因治疗研究 (AAV)载体已经显示出巨大的前景，事实上，在生命早期应用AAV基因治疗增加了存活率， 改善生活质量，并减少抽搐（twi）小鼠，KD的自然模型的神经病理学。基于 基于这些重要的成功，基于AAV的基因治疗临床试验仅开始用于婴儿KD。 然而，尽管预防了显著的疾病相关缺陷，但HSCT和临床前AAV-基因表达仍然存在缺陷。 治疗试验显示了不同的长期疗效和神经疾病的复发。 因此，对KD基因治疗的现状、HSCT治疗主要表现为前驱期患儿的局限性、 事实上，青少年和成人发病的KD患者，其中包括一个显着的克拉贝分数， 患者大部分仍然没有得到任何治疗，这凸显了制定额外策略来维持生命的必要性 为KD患者提供长期保护。使用底物减少疗法（SRT）策略，单独或 与KD的当前和新疗法相结合，是实现这一目标的一种潜在方法。在这个应用程序中，我们将 使用两种选择性抑制神经酰胺半乳糖基转移酶（CGT）和酸的小的新化合物， 神经酰胺酶（ACD），通过神经酰胺的半乳糖基化介导精神病肽产生的酶， 鞘氨醇（CGT）和半乳糖基神经酰胺（ACD）的脱酰化。基于这样的前提， 精神分裂素的合成将预防/减少精神分裂素相关的病理学在出生后早期的发展， 哺乳动物大脑，我们将测试CGT和ACD的SRT增强HSCT和AAV-GALC基因的功效 在婴儿KD的小鼠模型（抽搐小鼠）中的治疗和用 CGT或ACD抑制剂改善/预防成人发病KD新模型中的疾病。

SUMMARY Krabbe disease (KD) is caused by the deficiency of the ubiquitously expressed lysosomal enzyme galactosylceramidase (GALC) which is responsible for the degradation of galactosylceramides and galactosylsphingosine (psychosine). Because the synthetic pathway conducing to psychosine is not affected in KD, psychosine is continuously produced and accumulated in the Krabbe nervous system. Toxic levels of psychosine are considered the main pathogenic trigger of disease. Currently, the standard of care for KD is hematopoietic stem cell transplantation (HSCT), which is only applicable to asymptomatic or early symptomatic infantile KD cases and only protracts disease. Pre-clinical gene therapy studies using adeno-associated viral (AAV) vectors have shown great promise and in fact, AAV gene therapy applied early in life increases survival, improves quality of life, and decreases neuropathology in twitcher (twi) mice, the natural model for KD. Based on these important successes, AAV-based gene therapy clinical trials are being started only for infantile KD. However, despite the prevention of significant disease-related deficits, HSCT and pre-clinical AAV-gene therapy trials show varied long-term efficacy and resurgence of neurological disease. Thus, the status of gene therapy for KD, the limitations of HSCT to treat primarily presymptomatic infantile KD and the fact that juvenile and adult onset KD patients, which encompass a significant fraction of Krabbe patients, largely remain without any treatment, highlight the need to develop additional strategies to sustain long-term protection for KD patients. The use of substrate reduction therapies (SRT) strategies, singly or combined with current and new therapies for KD, is one potential way to achieve this. In this application we will use two small new compounds which selectively inhibit ceramide galactosyltransferase (CGT) and acid ceramidase (ACD), enzymes that mediate the production of psychosine via galactosylation of ceramides and sphingosine (CGT) and deacylation of galactosylceramide (ACD). Based on the premise that reducing psychosine synthesis will prevent/reduce psychosine-related pathology at early postnatal development of the mammalian brain, we will test the efficacy of SRT of CGT and ACD to enhance HSCT and AAV-GALC gene therapy in the mouse model of infantile KD (twitcher mouse) and the efficacy of single treatment with CGT or ACD inhibitors to ameliorate/prevent disease in a new model of adult-onset KD.