(S)-5'-C-Aminopropyl-2'-O-methyl nucleosides enhance antisense activity in cultured cells and binding affinity to...

Antisense oligonucleotides (ASOs) are a promising clinical tool that could be applied for unmet medical needs, but there are several limitations for their therapeutic application. Here, we designed and synthesized (S)-5'-C-aminopropyl-2'-O-methylcytidine, and oligonucleotides containing (S)-5'-C-aminopropyl-2'-O-methyluridine and -methylcytidine. We then investigated the properties of ASOs containing these nucleoside analogs. (S)-5'-C-Aminopropyl modifications enhanced the thermal stability of DNA/RNA duplexes when compared to other commercially available 2'-O-methyl modifications. This suggested that the terminal ammonium cation on the alkyl side chains neutralized the negative charge of the phosphates in the duplex. Additionally, the overall conformation of ASO/RNA duplexes was retained with the modified ASOs. Thus, these duplexes exhibited the ability to elicit RNase H activity. Furthermore, we found that ASOs containing the (S)-5'-C-aminopropyl modification exhibited higher antisense potency than those containing the 2'-O-methyl modification in cultured cells. Therefore, the (S)-5'-C-aminopropyl-2'-O-methyl nucleosides synthesized in this study are promising candidates for developing antisense therapeutics.