Engineered Transfer RNA Therapy Restores Proteins in Genetic Disease Models, Study Finds

Researchers at the University of Toronto reported in Science on August 27 that engineered transfer RNA molecules can restore full-length, functional proteins in cells carrying premature stop signals, offering a single therapeutic strategy for thousands of genetic diseases. The work, led by Bowen Li with Haissi Cui and Jingan Chen as co-leads, targets nonsense mutations that account for about 11 percent of inherited disorders, including subsets of cystic fibrosis, muscular dystrophy, and neurological conditions.

The Approach

Nonsense mutations insert a premature termination codon into a gene's instructions, causing cells to stop protein synthesis early and produce truncated or absent proteins. The team engineered suppressor tRNAs that recognize these premature stop codons and insert the intended amino acid, letting the ribosome read through and build the full-length protein. Two innovations made it work: a specific natural chemical modification that made the tRNA substantially more active and longer-lasting, and a lipid nanoparticle delivery system redesigned for tRNA and administered by inhalation to the lungs.

Results

In human airway cells carrying two common cystic fibrosis mutations, the CFTR protein returned and functioned properly for more than 40 days. The approach also worked in mouse models and in patient-derived organoids from a cystic fibrosis patient with a complex four-mutation genotype who was unresponsive to existing drugs. Neither the modified tRNA nor the CFTR modulator Trikafta worked effectively alone in those patient cells, but the combination restored full-length CFTR production and function.

Why It Matters

Because nonsense mutations always produce one of only three possible stop codons, a single engineered tRNA could treat the same type of mutation across many different genes and diseases, a one-size-fits-many strategy. Roughly 1 in 10 cystic fibrosis patients have nonsense mutations and do not benefit from existing modulators, which repair misshapen protein but cannot fix protein that was never built. The team is now expanding testing to Duchenne muscular dystrophy and Rett syndrome, and aims to bring the inhalable therapy to clinical trials within two to three years.