Allele-specific antisense oligonucleotide therapy for dominantly inherited hearing impairment DFNA9.

The c.151C>T founder mutation in COCH is a frequent cause of late onset, dominantly inherited hearing impairment and vestibular dysfunction (DFNA9) in the Dutch/Belgian population. The initial clinical symptoms only manifest between the 3rd and 5th decade of life, which leaves ample time for therapeutic intervention. The dominant inheritance pattern and established non-haploinsufficiency disease mechanism indicate that suppressing translation of mutant COCH transcripts has high therapeutic potential. Single-Molecule Real-Time (SMRT) sequencing resulted in the identification of 11 variants with a low population-frequency (< 10%), that are specific to the c.151C>T mutant COCH allele. Proof of concept was obtained that gapmer antisense oligonucleotides (AONs), directed against the c.151C>T mutation or mutant allele-specific intronic variants, are able to specifically induce mutant COCH transcript degradation when delivered to transgenic cells expressing COCH minigenes. Sequence optimization of the AONs against the c.151C>T mutation resulted in a lead molecule that reduced the levels of mutant COCH transcripts by ~60% in a transgenic cell model, without affecting wildtype COCH transcript levels. With the proven safety of AONs in humans, and rapid advancements in inner ear drug delivery, our in-vitro studies indicate that AONs offer a promising treatment modality for DFNA9.