The linear synthesis of 4'-C-aminoethoxy thymidine (AEoT) nucleoside phosphoramidite was accomplished using deoxythymidine as the starting material. This analog was incorporated into several oligonucleotides, the applicability of which as antisense oligonucleotides (ASOs) was then evaluated. The AEoT-modified DNA/RNA duplex exhibited improved thermal stability compared to unmodified and 4'-C-aminoethyl thymidine (4'-AET) modified heteroduplexes. The serum stability of AEoT-modified DNA was notably increased by several-folds compared to that of unmodified DNA. Furthermore, RNase H-dependent cleavage of the modified-DNA/RNA hybrids was found to be sustained. In addition, the modified antisense and unmodified oligonucleotides also displayed relatively comparable inhibition of the KRAS gene in human lung cancer cells. This study strengthens our understanding of the potential application of 4'-C-aminoethoxy-modified nucleotides as ASO therapeutics.
Keywords: aminoethoxy modification; antisense DNA; gene expression; nuclease resistance; oligonucleotide; thermal stability.
© 2022 Wiley-VHCA AG, Zurich, Switzerland.