A series of 2′-deoxy and novel 2′-O-methyl and 2′-O-(2-methoxyethyl) (2′-MOE) oligonucleotides with internucleotide methanesulfonyl (mesyl, μ) or 1-butanesulfonyl (busyl, β) phosphoramidate groups has been synthesized for evaluation as potential splice-switching oligonucleotides. Evaluation of their splice-switching activity in spinal muscular atrophy patient-derived fibroblasts revealed no significant difference in splice-switching efficacy between 2′-MOE mesyl oligonucleotide and the corresponding phosphorothioate (nusinersen). Yet, a survival study with model neonatal mice has shown the antisense 2′-MOE mesyl oligonucleotide to be inferior to nusinersen at the highest dose of 40 mg/kg. A reason for their lower activity in vivo as ascertained by cellular uptake study by fluorescent confocal microscopy in HEK293 cell line could possibly be ascribed to compromised endosomal release and/or nuclear uptake of the 2′-OMe or 2′-MOE μ- and β-oligonucleotides compared to their phosphorothioate analog.

中文翻译：

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Mesyl Phosphoramidate 寡核苷酸作为潜在的剪接转换剂：主链结构对活性和细胞内定位的影响

一系列 2'-脱氧和新型 2'- O-甲基和 2' - O- (2-甲氧基乙基) (2'-MOE) 寡核苷酸与核苷酸间甲磺酰基（甲磺酰基，μ）或 1-丁磺酰基（busyl，β）氨基磷酸酯基团已被合成用于评估作为潜在的剪接转换寡核苷酸。评估它们在脊髓性肌萎缩症患者来源的成纤维细胞中的剪接转换活性显示 2'-MOE 甲磺酰寡核苷酸和相应的硫代磷酸酯 (nusinersen) 之间的剪接转换功效没有显着差异。然而，对模型新生小鼠的生存研究表明，在 40 mg/kg 的最高剂量下，反义 2'-MOE 甲磺酰寡核苷酸不如 nusinersen。它们在体内活性较低的原因 正如通过荧光共聚焦显微镜在 HEK293 细胞系中的细胞摄取研究所确定的，可能归因于与硫代磷酸酯类似物相比，2'-OMe 或 2'-MOE μ-和 β-寡核苷酸的内体释放和/或核摄取受损。