Identification of small molecules that enhance aminoglycoside-mediated suppression of CFTR and NF1 nonsense mutations.

Nonsense suppression rescues functional protein from mRNAs containing in-frame premature termination codons (PTCs). This approach employs small molecules that promote insertion of tRNAs at a PTC during translation (called "readthrough"), enabling translation to continue past the PTC to generate a full-length, functional protein. Some aminoglycosides such as G418 promote readthrough; however, their long-term use is thwarted by toxicity and modest potency. ELX-02, a novel synthetic aminoglycoside, was developed to have both enhanced readthrough activity and reduced toxicity in mammalian cells compared to traditional aminoglycosides. Recent studies suggest that at safe doses, aminoglycosides like ELX-02 may not possess sufficient efficacy to provide clinical benefits for most diseases. "Enhancer" molecules have been identified that do not possess readthrough activity themselves but enhance the efficiency of aminoglycoside-mediated readthrough. In this study, three newly identified series of enhancer molecules were tested for the ability to stimulate aminoglycoside-mediated readthrough of PTCs associated with cystic fibrosis and neurofibromatosis type 1. Although none of the enhancers alone induced readthrough, they all significantly increased readthrough via aminoglycosides at low doses (EC(10)). Overall, our results suggest that enhancer compounds may be a viable way to overcome potency issues associated with aminoglycosides, enabling rescue of protein function from nonsense alleles while minimizing toxicity.