Reduction of Off-Target Effects of Gapmer Antisense Oligonucleotides by Oligonucleotide Extension

AIM: Antisense oligonucleotide (ASO) has the potential to induce off-target effects by inadvertent binding of ASOs to unintended RNAs that have a sequence similar to the target RNA. In the present study, we focused on the association between oligonucleotide length and off-target effects. Oligonucleotide extension is assumed to have bilateral effects on hybridization-dependent changes in gene expression, i.e., one is the decrease of off-target effects based on the reduced number of off-target candidate genes with perfect matches, and the other is the increase of off-target effects based on the increased binding affinity between the ASO and the complementary RNAs that leads to better tolerability for mismatches. METHODS: To determine the effects of oligonucleotide extension of gapmer ASOs on off-target effects, an extensive microarray analysis was performed using human cells treated with a 14-mer gapmer ASO and the extended 18-mer derivatives with the same core 14-mer region. RESULTS AND DISCUSSION: Our data indicated that change in gene expression in the cells treated with 18-mer ASOs was significantly smaller than those with a 14-mer ASO, showing the decrease of off-target effects by oligonucleotide extension. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1007/s40291-021-00573-z.