Yamada Ken, Hariharan Vignesh N, Caiazzi Jillian, Miller Rachael, Ferguson Chantal M, Sapp Ellen, Fakih Hassan H, Tang Qi, Yamada Nozomi, Furgal Raymond C, Paquette Joseph D, Biscans Annabelle, Bramato Brianna M, McHugh Nicholas, Summers Ashley, Lochmann Clemens, Godinho Bruno M D C, Hildebrand Samuel, Jackson Samuel O, Echeverria Dimas, Hassler Matthew R, Alterman Julia F, DiFiglia Marian, Aronin Neil, Khvorova Anastasia
RNA Therapeutics Institute, University of Massachusetts Chan Medical School, Worcester, MA, USA.
Department of Medicine, University of Massachusetts Chan Medical School, Worcester, MA, USA.
Nat Biotechnol. 2024 Aug 1. doi: 10.1038/s41587-024-02336-7.
Therapeutic small interfering RNA (siRNA) requires sugar and backbone modifications to inhibit nuclease degradation. However, metabolic stabilization by phosphorothioate (PS), the only backbone chemistry used clinically, may be insufficient for targeting extrahepatic tissues. To improve oligonucleotide stabilization, we report the discovery, synthesis and characterization of extended nucleic acid (exNA) consisting of a methylene insertion between the 5'-C and 5'-OH of a nucleoside. exNA incorporation is compatible with common oligonucleotide synthetic protocols and the PS backbone, provides stabilization against 3' and 5' exonucleases and is tolerated at multiple oligonucleotide positions. A combined exNA-PS backbone enhances resistance to 3' exonuclease by ~32-fold over the conventional PS backbone and by >1,000-fold over the natural phosphodiester backbone, improving tissue exposure, tissue accumulation and efficacy in mice, both systemically and in the brain. The improved efficacy and durability imparted by exNA may enable therapeutic interventions in extrahepatic tissues, both with siRNA and with other oligonucleotides such as CRISPR guide RNA, antisense oligonucleotides, mRNA and tRNA.
治疗性小干扰RNA（siRNA）需要对糖基和骨架进行修饰以抑制核酸酶降解。然而，临床上唯一使用的骨架化学修饰——硫代磷酸酯（PS）介导的代谢稳定性，对于靶向肝外组织可能并不充分。为了提高寡核苷酸的稳定性，我们报告了一种扩展核酸（exNA）的发现、合成及表征，该核酸是在核苷的5'-C和5'-OH之间插入一个亚甲基构成。exNA的掺入与常见的寡核苷酸合成方案以及PS骨架兼容，能提供针对3'和5'核酸外切酶的稳定性，并且在多个寡核苷酸位置均可耐受。与传统PS骨架相比，exNA与PS骨架组合可使对3'核酸外切酶的抗性增强约32倍，与天然磷酸二酯骨架相比增强超过1000倍，从而改善了在小鼠体内全身及脑部的组织暴露、组织蓄积及疗效。exNA赋予的更高疗效和耐久性，可能使肝外组织的治疗干预成为可能，无论是使用siRNA还是其他寡核苷酸，如CRISPR引导RNA、反义寡核苷酸、mRNA和tRNA。
