A new study published shows that a small molecule (Potential new treatment) disrupted the long CTG repeats but left short repeats mostly alone.This was tested in mice that had myotonic dystrophy and seemed to work well.  Here is a piece form the journal about the impact of this study

                                                     Significance
Development of small-molecule lead medicines that potently and specifically modulate RNA function is challenging. We designed a small molecule that cleaves r(CUG)exp, the RNA repeat expansion that causes myotonic dystrophy type 1. In cells and in an animal model, the small-molecule cleaver specifically recognizes the 3-dimensional structure of r(CUG)exp, cleaving it more selectively among transcripts containing short, nonpathogenic r(CUG) repeats than an oligonucleotide that recognizes RNA sequence via Watson-Crick base pairing. The small molecule broadly relieves disease-associated phenotype in a mouse model. Thus, small molecules that recognize and cleave RNA structures should be