The authors have previously demonstrated that synthetic antisense oligonucleotides or duplex RNAs that are complementary to the expanded AAG repeat can activate expression of FXN and return levels of FXN protein to near normal. The potency of these compounds, however, was too low to encourage vigorous pre-clinical development. The authors now report testing of "gapmer" oligonucleotides consisting of a central DNA portion flanked by chemically modified RNA that increases binding affinity. This study finds that gapmer antisense oligonucleotides are several fold more potent activators of FXN expression relative to previously tested compounds. The potency of FXN activation is similar to a potent benchmark gapmer targeting the nuclear noncoding RNA MALAT-1, suggesting that this approach has potential for developing more effective compounds to regulate FXN expression in vivo.
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