背景:Zolgensma是一种基因替代疗法,已导致脊髓性肌萎缩(SMA)的有希望的治疗方法。然而,Zolgensma的临床试验提出了两个主要问题:治疗效果不足和不良事件.在最近的临床试验中,尽管进行了对症治疗,但仍有30%的患者未能达到运动里程碑。此外,超过20%的患者由于病毒剂量过多而表现出肝毒性,即使在施用免疫抑制剂后。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)相比,SMA的治疗效果有所改善。
方法:严重的SMA小鼠模型,SMA1.5型(Smn-/-;SMN2+/+;SMNΔ7+/-)小鼠,用于比较AAV9-SMNWT和AAV9-SMNK186R之间的疗效差异。所有动物在出生后第(P)1天通过面静脉或脑室注射。
结果:AAV9-SMNK186R治疗的小鼠寿命延长,体重,运动神经元数,与AAV9-SMNWT治疗的小鼠相比,肌肉重量和运动功能的改善。与AAV9-SMNK186R处理的小鼠(26.8±1.41天)相比,AAV9-SMNK186R处理的小鼠(144.8±26.11天)的寿命增加了10倍以上。AAV9-SMNK186R处理的小鼠显示出体重上升的模式,与AAV9-SMNWT处理的小鼠不同,直到P20平均增加到5克。多项运动功能测试显示SMNK186R的治疗效果改善。在负地轴测试中,AAV9-SMNK186R处理的小鼠成功地将身体向上转动,与AAV9-SMNWT处理的小鼠不同,未能从P23左右向上转动。在AAV9-SMNK186R处理的小鼠中很少观察到后肢抱紧表型,与AAV9-SMNWT处理的小鼠不同,该小鼠在30s中表现出超过20的紧握表型。在这一点上,与无显著神经毒性的AAV9-SMNK186R治疗小鼠相比,AAV9-SMNK186R治疗小鼠的运动神经元数量(1.5倍)和肌纤维大小(2.1倍)显著增加.与AAV9-SMNK186R相比,AAV9-SMNWT的肝脏缺陷较少,根据肝细胞增殖增加(P<0.0001)和胰岛素样生长因子-1产生(P<0.0001)判断。尤其是,与SMNWT相比,低剂量AAV9-SMNK186R(9倍)也减少了扣紧时间。
结论:SMNK186R将在治疗效果不足的重度SMA患者中提供改善的治疗效果。AAV9-SMNK186R低剂量治疗SMA患者可以减少Zolgensma的不良事件。总的来说,SMNK186R作为SMA的新疗法具有价值,可以提高治疗效果并同时减少不良事件。
BACKGROUND: Zolgensma 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).
METHODS: A 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.
RESULTS: AAV9-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.
CONCLUSIONS: SMNK186R 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.