Targeting Expanded CUG and CTG Repeats as a Therapeutic Approach for Myotonic Dystrophy Type 1 (DM1)

Myotonic dystrophy type 1 (DM1) is caused by expanded CTG repeats, d(CTG)^exp, transcribed into toxic r(CUG)^exp RNA repeats that sequester splicing regulator MBNL1, leading to its loss-of-function. An emerging therapeutic strategy toward DM1 treatment relies on the inhibition of MBNL1 sequestration by using small molecules, oligomers, peptides, engineered proteins, or synthetic oligonucleotides that interact with CUG repeats at the RNA level and/or CTG repeats at the DNA level. This review covers ∼18 years of research in the field of CUG and CTG ligands that were identified or rationally designed as DM1 drug candidates, with an emphasis on their chemical structures, molecular design, RNA- or DNA-binding modes, in vitro affinities and specificities, molecular mechanisms of action, and biological activity in DM1 models.