Hagiwara Kenji, Honma Masakazu, Harumoto Toshimasa, Harada Kenji, Sawada Takashi, Yamamoto Junichiro, Shinohara Fumikazu
Nucleic Acid Medicine Research Laboratories and Research Functions Unit, R&D Division, Kyowa Kirin Co., Ltd., Tokyo, Japan.
Management Office, Research Functions Unit, R&D Division, Kyowa Kirin Co., Ltd., Tokyo, Japan.
Nucleic Acid Ther. 2020 Dec;30(6):346-364. doi: 10.1089/nat.2020.0894. Epub 2020 Oct 5.
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 , as well as pharmacokinetics, accumulation, knockdown activity, and safety . Our circular siRNA exhibited higher stability against serum and exonucleases, increased cellular uptake, and stronger knockdown activity without transfection reagent 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.
小干扰RNA（siRNAs）正被开发为一种新型治疗方式；然而，阻碍其在肝外组织中应用的问题依然存在，包括在生物环境中稳定性不足以及靶向组织的药物递送系统效率低下。因此，需要进行技术改进，以实现肝外组织中靶信使核糖核酸（mRNA）的有效沉默。我们开发了前药型共价闭合siRNA（环状siRNA）作为一种新型核酸药物，通过全身给药在无药物递送成分的情况下敲低肝外组织中的靶基因。环状siRNA可通过化学合成，利用其可裂解连接子形成高效敲低的最佳结构；即在细胞外和细胞内环境中分别呈环状和线性结构。在本研究中，我们研究了环状siRNA的物理化学性质、敲低机制及特征，以及药代动力学、蓄积、敲低活性和安全性。与线性siRNA相比，我们的环状siRNA对血清和核酸外切酶表现出更高的稳定性，细胞摄取增加，且在无转染试剂的情况下具有更强的敲低活性。此外，对小鼠进行全身给药后，环状siRNA显示出循环时间延长，在肝脏、肾脏和肌肉中的敲低活性提高，且未引起不良反应。环状siRNA可能代表RNA干扰疗法的另一个平台，为疾病治疗提供替代解决方案。
