State-of-the-art small interfering RNA (siRNA) therapeutics such as givosiran and fitusiran are constructed from three variable components: a fully-modified RNA core that conveys metabolic stability, a targeting moiety that mediates target-cell uptake, and a linker. This structural complexity poses challenges for metabolite characterization and risk assessment after long-term patient exposure. In this study, we show that basic phosphorothioate modification of a siRNA targeting the oncoprotein Lin28B provides a useful increase in metabolic stability, without greatly compromising potency. We found that its stability in vitro matched that of nanoparticle-free patisiran in serum and surpassed it in liver tritosome extracts, although it did not reach the stability of the fitusiran siRNA core structure. Liver and kidney were the main sites of accumulation after its subcutaneous administration in mice. Despite the lack of a delivery agent-free antitumor effect, we anticipate our study to be a starting point to develop alternative siRNA scaffolds that can be degraded into naturally-occurring metabolites and help alleviate the aforementioned challenges. Furthermore, Lin28B is a promising target for cancers, and the development of such simplified siRNA analogs, possibly together with novel targeting units, holds potential.

中文翻译：

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用于体内基因沉默的全硫代磷酸酯小干扰 RNA 的药效学和药代动力学特性

最先进的小干扰 RNA (siRNA) 疗法，例如 givosiran 和 fitusiran，由三个可变成分构成：传递代谢稳定性的完全修饰的 RNA 核心、介导靶细胞摄取的靶向部分和接头. 这种结构复杂性对长期患者暴露后的代谢物表征和风险评估提出了挑战。在这项研究中，我们表明，针对癌蛋白 Lin28B 的 siRNA 的基本硫代磷酸酯修饰可有效提高代谢稳定性，而不会大大影响效力。我们发现它在体外的稳定性与血清中不含纳米颗粒的patisiran相匹配，并在肝脏三​​体提取物中超过它，尽管它没有达到fitusiran siRNA核心结构的稳定性。在小鼠皮下给药后，肝脏和肾脏是主要的蓄积部位。尽管缺乏不含递送剂的抗肿瘤作用，但我们预计我们的研究将成为开发可降解为天然代谢物并有助于缓解上述挑战的替代 siRNA 支架的起点。此外，Lin28B 是一种很有前途的癌症靶点，这种简化的 siRNA 类似物的开发，可能与新的靶向单元一起，具有潜力。