Sirna Therapeutics, a wholly owned subsidiary of Merck and Co., San Francisco, California, USA.
Mol Ther Nucleic Acids. 2012 Jan 24;1(1):e5. doi: 10.1038/mtna.2011.4.
Current modifications used in small interfering RNAs (siRNAs), such as 2'-methoxy (2'-OMe) and 2'-fluoro (2'-F), improve stability, specificity or immunogenic properties but do not improve potency. These modifications were previously designed for use in antisense and not siRNA. We show, for the first time, that the siRNA-optimized novel 2'-O modifications, 2'-O-benzyl, and 2'-O-methyl-4-pyridine (2'-O-CH2Py(4)), are tolerated at multiple positions on the guide strand of siRNA sequences in vivo. 2'-O-benzyl and 2'-O-CH2Py(4) modifications were tested at each position individually along the guide strand in five sequences to determine positions that tolerated the modifications. The positions were combined together and found to increase potency and duration of siRNAs in vivo compared to their unmodified counterparts when delivered using lipid nanoparticles. For 2'-O-benzyl, four incorporations were tolerated with similar activity to the unmodified siRNA in vivo, while for 2'-O-CH2Py(4) six incorporations were tolerated. Increased in vivo activity was observed when the modifications were combined at positions 8 and 15 on the guide strand. Understanding the optimal placement of siRNA-optimized modifications needed for maximal in vivo activity is necessary for development of RNA-based therapeutics.
目前用于小干扰 RNA（siRNA）的修饰，如 2'-甲氧基（2'-OME）和 2'-氟（2'-F），可以提高稳定性、特异性或免疫原性，但不能提高效力。这些修饰以前是为反义寡核苷酸而不是 siRNA 设计的。我们首次表明，siRNA 优化的新型 2'-O 修饰物，2'-O-苄基和 2'-O-甲基-4-吡啶（2'-O-CH2Py(4)），在体内 siRNA 序列的向导链上的多个位置是可以耐受的。在五个序列的向导链上的每个位置单独测试 2'-O-苄基和 2'-O-CH2Py(4)修饰物，以确定可以耐受修饰的位置。将这些位置组合在一起，与未修饰的 siRNA 相比，当使用脂质纳米粒递送至体内时，siRNA 的效力和持续时间都有所增加。对于 2'-O-苄基，有四个位置可以耐受修饰，其体内活性与未修饰的 siRNA 相似，而对于 2'-O-CH2Py(4)，有六个位置可以耐受修饰。当修饰物被组合在向导链上的第 8 位和第 15 位时，观察到体内活性的增加。了解用于最大体内活性的 siRNA 优化修饰的最佳位置对于开发基于 RNA 的治疗方法是必要的。
