Engineering suppressor tRNAs for effective treatment of Duchenne muscular dystrophy

Duchenne muscular dystrophy (DMD) is a fatal disorder caused by loss of dystrophin, a protein essential for muscle cell integrity. To date, no therapeutic has restored full-length dystrophin. Suppressor transfer RNAs (sup-tRNAs) have the potential to treat the ∼15% of patients with DMD and nonsense mutations. We have evolved highly potent UAA sup-tRNAs through an extensive mutagenesis screening campaign, optimized our adeno-associated virus (AAV) expression vectors, and developed efficient RNA polymerase III promoters. We show that systemic delivery of these sup-tRNAs restores full-length dystrophin and recovers muscle strength and motor function in mice at lower doses than AAV microdystrophin therapies. We see no adverse toxicology and observe proteome-wide reversion of molecular pathophysiology. These data establish sup-tRNAs as a promising therapeutic platform for DMD and other disorders.