Exploring the Potential of Small Molecule-Based Therapeutic Approaches for Targeting Trinucleotide Repeat Disorders

In recent years, neurological disorders have globally become a leading cause of disability and death. Neurological disorders are very common in both high- and low-income countries, and the number of patients is predicted to increase in the coming decades. Disorders caused by the expanded trinucleotide repeats (CAG, CGG, CCG, CTG, CUG, GAA, and GCN) in the genome, also described as trinucleotide repeat expansion disorders (TREDs), comprise of the major class of neurological diseases. Various TREDs have different modes of pathogenesis, but the severity and time of onset of disease depends on the trinucleotide repeat numbers. Numerous therapeutic strategies, including symptomatic treatment, blockage of mutant protein synthesis, targeting the toxic protein aggregates and degradation of RNA transcripts have been developed for the treatment of these diseases. However, various limitations to these therapeutic strategies have been reported, and therefore, researchers are exploring different avenues of therapeutics development. One of the recent developments include targeting the expanded repeats with small molecules. Small molecule binds with the secondary/tertiary structure of RNA (like bulges, loops, and hairpins) irrespective of its sequences. Altogether, small molecule-based therapeutics may have the advantage over others to be able to overcome the hurdles of the blood-brain barrier, poor absorption, and allergic reactions. In this review, we have summarized various TREDs and envisage the potential of small molecule-based therapeutics for targeting these hitherto incurable neurological disorders.