Figure 5.

Secondary screen of enhanced selectivity antisense oligonucleotides (ASO). (a) Typical design of a “gapmer” ASO with high affinity, non-RHaseH cleavable wings surrounding a PS, RNaseH cleavable gap. (b) One strategy for increasing selectivity of a potent ASO by shortening the gap: replacing PS nucleosides at minor cleavage sites with RNAseH noncleavable nucleosides thus restricting cleavage to the main site at the single-nucleotide polymorphism (SNP) of interest.²⁸ Modified ASOs were then screened in Hu97/18 mice. (c) Example western blots showing wt and muHTT protein. ASOs in orange contain only 5-9-5 2′-O-methoxyethyl modifications. ASOs in blue contain cEt modifications. (d) Quantitation of HTT protein in both hemispheres of four animals. Errors bars are SEM. **P < 0.01, ***P < 0.001 difference between wt and muHTT by Bonferroni post hoc analysis following two-way analysis of variance. Data from the primary screen for the parent molecule, A3, are included on the graph to allow direct comparison.