Cell Delivery Agent as Drug. A Multitarget Agent Delivers an Antisense Oligonucleotide for Synergistic Activity in Myotonic Dystrophy Type 1

Drug delivery vehicles are hoped to be inert, although many suffer toxicity issues that limit their use. In developing potential agents to treat myotonic dystrophy type 1 (DM1), we wondered if a delivery vehicle might be designed to be a direct acting drug. DM1 is an incurable neurodegenerative disease that originates from expanded (CTG)·(CAG) repeats in the 3'-UTR of the DMPK gene. The majority of drug discovery efforts have been focused on development of small molecules that inhibit MBNL1 protein sequestration by the expanded RNA transcript, r(CUG)exp. Antisense oligonucleotides (ASOs) have also been utilized to treat DM1. However, ASOs normally exhibit poor cell penetration so considerable effort has focused on their delivery. Herein, we report a series of multitargeting oligomeric ligands that have been developed to serve both as drug molecules and as antisense delivery vehicles for DM1. As a result of multivalency, the longer oligomers bound the target DNA and RNA with nanomolar affinities, in vitro, and exhibited improved disease outcomes in DM cell culture model and DM1 patient myotubes. The oligomers form polyplexes with a locked nucleic acid (LNA) CAG16 gapmer, facilitating its cell uptake in both HeLa cells and DM1 patient myotubes decreasing the level of toxic r(CUG)exp significantly. RNA-seq analysis indicated that the oligomeric ligand and its polyplex can rescue DM1 associated splicing defects and gene expression changes transcriptome-wide in DM1 patient myotubes.