2′-Ribose-modified nucleotides: A strategy for reducing off-target effects of oligonucleotide drugs

Necessary chemical modifications can enhance the metabolic stability and therapeutic efficacy of oligonucleotide-based drugs. Herein, a series of mononucleotides with different functional group modifications at the ribose 2'-position were designed and synthesized for reducing off-target effects of oligonucleotide drugs. After incorporating them into the antisense strand of small interfering RNAs (siRNAs), we assessed their biophysical and biological properties. The results revealed that, following the substitution of the conventional 2'-O-methyl or 2'-O-fluoro ribose modifications with our newly designed functional groups, although the thermal stability of the duplexes decreased, the <i>in vitro</i> silencing activity against proprotein convertase subtilisin/kexin type 9 (PCSK9) gene was significantly enhanced and the off-target effects of specific genes could be effectively mitigated. These data prove that 2'-ribose-modified nucleotides can be effectively utilized in preclinical and clinical disease model studies for gene silencing and reducing off-target effects.