BackgroundZolgensma is a gene‐replacement therapy that has led to a promising treatment for spinal muscular atrophy (SMA). However, clinical trials of Zolgensma have raised two major concerns: insufficient therapeutic effects and adverse events. In a recent clinical trial, 30% of patients failed to achieve motor milestones despite pre‐symptomatic treatment. In addition, more than 20% of patients showed hepatotoxicity due to excessive virus dosage, even after the administration of an immunosuppressant. Here, we aimed to test whether a ubiquitination‐resistant variant of survival motor neuron (SMN), SMNK186R, has improved therapeutic effects for SMA compared with wild‐type SMN (SMNWT).MethodsA severe SMA mouse model, SMA type 1.5 (Smn−/−; SMN2+/+; SMN∆7+/−) mice, was used to compare the differences in therapeutic efficacy between AAV9‐SMNWT and AAV9‐SMNK186R. All animals were injected within Postnatal Day (P) 1 through a facial vein or cerebral ventricle.ResultsAAV9‐SMNK186R‐treated mice showed increased lifespan, body weight, motor neuron number, muscle weight and functional improvement in motor functions as compared with AAV9‐SMNWT‐treated mice. Lifespan increased by more than 10‐fold in AAV9‐SMNK186R‐treated mice (144.8 ± 26.11 days) as compared with AAV9‐SMNWT‐treated mice (26.8 ± 1.41 days). AAV9‐SMNK186R‐treated mice showed an ascending weight pattern, unlike AAV9‐SMNWT‐treated mice, which only gained weight until P20 up to 5 g on average. Several motor function tests showed the improved therapeutic efficacy of SMNK186R. In the negative geotaxis test, AAV9‐SMNK186R‐treated mice turned their bodies in an upward direction successfully, unlike AAV9‐SMNWT‐treated mice, which failed to turn upwards from around P23. Hind limb clasping phenotype was rarely observed in AAV9‐SMNK186R‐treated mice, unlike AAV9‐SMNWT‐treated mice that showed clasping phenotype for more than 20 out of 30 s. At this point, the number of motor neurons (1.5‐fold) and the size of myofibers (2.1‐fold) were significantly increased in AAV9‐SMNK186R‐treated mice compared with AAV9‐SMNWT‐treated mice without prominent neurotoxicity. AAV9‐SMNK186R had fewer liver defects compared with AAV9‐SMNWT, as judged by increased proliferation of hepatocytes (P < 0.0001) and insulin‐like growth factor‐1 production (P < 0.0001). Especially, low‐dose AAV9‐SMNK186R (nine‐fold) also reduced clasping time compared with SMNWT.ConclusionsSMNK186R will provide improved therapeutic efficacy in patients with severe SMA with insufficient therapeutic efficacy. Low‐dose treatment of SMA patients with AAV9‐SMNK186R can reduce the adverse events of Zolgensma. Collectively, SMNK186R has value as a new treatment for SMA that improves treatment effectiveness and reduces adverse events simultaneously.

中文翻译：

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通过泛素化抗性运动神经元存活变异改进脊髓性肌萎缩症的治疗方法

背景Zolgensma 是一种基因替代疗法，为脊髓性肌萎缩症 (SMA) 的治疗带来了前景。然而，Zolgensma 的临床试验引起了两个主要担忧：治疗效果不足和不良事件。在最近的一项临床试验中，尽管进行了症状前治疗，仍有 30% 的患者未能达到运动里程碑。此外，即使在服用免疫抑制剂后，仍有超过20%的患者因病毒剂量过多而表现出肝毒性。在这里，我们的目的是测试存活运动神经元（SMN）的泛素化抗性变体，SMNK186R，与野生型 SMN（SMNWT).方法重度SMA小鼠模型，SMA 1.5型(斯姆恩−/−;SMN2+/+;SMNΔ7+/-）小鼠，用于比较 AAV9-SMN 之间的治疗效果差异WT和 AAV9-SMNK186R。所有动物均在出生后第 1 天（P）内通过面静脉或脑室注射。 结果 AAV9-SMNK186R‐与 AAV9‐SMN 相比，治疗小鼠的寿命、体重、运动神经元数量、肌肉重量和运动功能都有所改善WT‐治疗小鼠。 AAV9-SMN 的寿命增加了 10 倍以上K186R‐与 AAV9‐SMN 相比，接受治疗的小鼠（144.8 ± 26.11 天）WT‐治疗小鼠（26.8 ± 1.41 天）。 AAV9-SMNK186R‐与 AAV9‐SMN 不同，治疗小鼠表现出体重上升模式WT‐接受治疗的小鼠，直到 P20 体重才平均增加 5 克。多项运动功能测试显示SMN治疗效果提高K186R。在负趋地性测试中，AAV9-SMNK186R‐与 AAV9‐SMN 不同，接受治疗的小鼠成功地将身体转向向上方向WT‐接受治疗的小鼠，未能从 P23 左右向上转变。 AAV9-SMN 中很少观察到后肢紧握表型K186R‐治疗小鼠，与 AAV9‐SMN 不同WT‐接受治疗的小鼠在 30 秒内有超过 20 秒表现出紧握表型。此时，AAV9-SMN 中运动神经元的数量（1.5 倍）和肌纤维的大小（2.1 倍）显着增加K186R‐治疗小鼠与 AAV9‐SMN 相比WT‐治疗小鼠没有明显的神经毒性。 AAV9-SMNK186R与 AAV9-SMN 相比，肝脏缺陷较少WT，根据肝细胞增殖增加来判断（磷< 0.0001) 和胰岛素样生长因子-1 的产生 (磷< 0.0001)。特别是低剂量 AAV9-SMNK186R与 SMN 相比，（九倍）还减少了握紧时间WT.结论SMNK186R将为治疗效果不足的严重 SMA 患者提供改善的治疗效果。 AAV9-SMN SMA 患者的低剂量治疗K186R可以减少Zolgensma的不良事件。统称为SMNK186R作为 SMA 的新治疗方法具有价值，可提高治疗效果并同时减少不良事件。