The present disclosure provides compositions that inhibit microsatellite promoted expression of deleterious expansions by targeting expanded CTG DNA as well as methods using such compositions for use in treating or ameliorating the effects of a medical condition involving trinucleotide repeats in a subject. In embodiments, the present disclosure provides a method for treating a medical condition involving trinucleotide repeats, including a disease such as DM1, in a subject in need thereof by administering to the subject an effective amount of a modified polycyclic compound of the present disclosure. Processes for synthesizing modified polycyclic compounds that rescue mis-splicing at low nanomolar concentration with negligible toxicity are also disclosed.