Identification of novel small molecule compounds with readthrough activity in Nagashima-type palmoplantar keratosis

BACKGROUND: Nagashima-type palmoplantar keratosis (NPPK), the most common form of hereditary palmoplantar keratodermas in East Asian populations, is caused by biallelic loss-of-function mutations in SERPINB7 such as p.Arg266Ter (c.796 C>T). This mutation introduces a premature termination codon (PTC). Given the minimal efficacy of current drugs in improving NPPK skin phenotypes, we applied readthrough therapy to enable the production of functional proteins by allowing ribosomes to read through premature stop codons. OBJECTIVE: To discover small molecule compounds with readthrough potency. METHODS: Using high-throughput screening, we initially screened nearly 20,000 small molecule compounds. Using Western blot, we assessed the readthrough effectiveness of shortlisted compounds on the mutant SERPINB7 vector. We identified a promising compound and acquired structurally related compounds, comparing then their potency with that of gentamicin and ataluren. In addition, we evaluated the readthrough capability of the identified compounds on other 11 premature termination codons with different + 4 nucleotides. RESULTS: The identified hit compounds demonstrated superior readthrough efficacy than gentamicin and ataluren. Notably, our compounds were effective in enabling readthrough, particularly on UGAA and UAAG premature stop codons. CONCLUSION: Our research identified new compounds that effectively promote the readthrough of premature stop codons. In vitro, these compounds showed higher readthrough potency than drugs such as gentamicin or ataluren. These results suggest that these compounds could be promising therapeutic agents for genetic diseases caused by nonsense mutations.