Chemically enhanced suppressor tRNAs combined with a lung-targeted delivery system can restore production of a critical protein in models of cystic fibrosis caused by nonsense mutations, according to a new study. “Translating these effects to the amelioration of respiratory function in cystic fibrosis patients will require further work, including characterization of side effects, especially given dose-dependent inflammation noted both by [the current study] in mice and in prior animal studies of inhaled [lipid nanoparticle] delivery,” write Jacob Myerson and Drew Weissman in a related Perspective. Nonsense mutations introduce premature stop signals in messenger RNA, causing protein production in cells to halt early, often resulting in truncated, nonfunctional proteins. Because these mutations account for ~11% of human genetic disorders, there is considerable interest in developing therapies that can restore production of full-length proteins. Suppressor tRNAs (sup-tRNAs) offer a promising approach. By modifying their anticodons to recognize premature stop codons, engineered sup-tRNAs can insert the appropriate amino acid and allow the cell to resume translation of full-length, functional proteins. Yet the clinical potential of sup-tRNAs has been constrained by inefficient readthrough, immunogenicity, and difficulty in delivering them into the body.
To address this, Jingan Chen and colleagues chemically modified sup-tRNAs and engineered lipid nanoparticles (LNPs) for delivery into the lungs via inhalation, looking to see if they could repair the nonsense mutations in the cystic fibrosis transmembrane conductance regulator (CFTR) gene responsible for cystic fibrosis. Chen et al. tested the approach in bronchial epithelial cells, mouse models, and patient-derived cystic fibrosis organoids and found that the chemical modifications increased the readthrough of premature termination codons and tRNA aminoacylation, prolonged the tRNAs' functional activity, and reduced innate immune activation. Moreover, the approach restored CFTR protein production and function across cell, animal, and patient-derived organoid models.
