siRNAs are being developed as a novel therapeutic modality; however, problems impeding their application in extrahepatic tissues persist, including inadequate stability in biological environments and inefficient drug delivery system to target tissues. Thus, technological improvements that enable robust silencing of target messenger RNA (mRNA) in extrahepatic tissues are necessary. We developed prodrug type covalently closed siRNA (circular siRNA) as a novel nucleic acid agent to knockdown target genes in extrahepatic tissues by systemic administration without drug delivery components. Circular siRNA, which is chemically synthesizable, can assume optimal structures for efficient knockdown using its cleavable linker; namely, circular and linear structure in extracellular and intracellular environment, respectively. In this study, we investigated circular siRNA physicochemical properties, knockdown mechanism, and characteristics in vitro, as well as pharmacokinetics, accumulation, knockdown activity, and safety in vivo. Our circular siRNA exhibited higher stability against serum and exonucleases, increased cellular uptake, and stronger knockdown activity without transfection reagent in vitro than linear siRNA. Furthermore, after systemic administration to mice, circular siRNA showed prolonged circulation and improved knockdown activity in the liver, kidney, and muscle, without causing adverse effects. Circular siRNA may represent an additional platform for RNAi therapeutics, providing alternate solutions for disease treatment.

中文翻译：

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通过全身给药开发用于体内敲低的前药型环状 siRNA

siRNAs 正在被开发为一种新的治疗方式；然而，阻碍它们在肝外组织中应用的问题仍然存在，包括生物环境稳定性不足和靶向组织的药物递送系统效率低下。因此，有必要进行技术改进，以实现肝外组织中目标信使 RNA (mRNA) 的稳健沉默。我们开发了前药型共价闭合 siRNA（环状 siRNA）作为一种新型核酸试剂，通过全身给药而无需药物递送成分来敲低肝外组织中的靶基因。环状 siRNA 是可化学合成的，可以使用其可切割的接头呈现最佳结构以实现有效的敲除；即分别在细胞外和细胞内环境中的圆形和线性结构。在这项研究中，在体外，以及药代动力学，积累，敲低活性和安全性的体内。与线性 siRNA 相比，我们的环状 siRNA 对血清和外切核酸酶表现出更高的稳定性、增加的细胞摄取和更强的体外无转染试剂的敲低活性。此外，在对小鼠全身给药后，环状 siRNA 在肝脏、肾脏和肌肉中显示出延长的循环和改善的敲低活性，而不会造成不良影响。环状 siRNA 可能代表 RNAi 疗法的另一个平台，为疾病治疗提供替代解决方案。