It’s another CRISPR first: fixing a hereditary disease in utero. Scientists from Pennsylvania University and the Children’s Hospital of Philadelphia used a base editor to rescue tyrosinemia in fetal mice. “The results of this proof-of-concept work demonstrate the possibility of efficiently performing gene editing before birth, pointing to a potential new therapeutic approach for selected congenital disorders,” Avery C. Rossidis and colleagues write in Nature Medicine. 

The team is now considering delivery methods alternative to adenovirus vectors, such as lipid nanoparticles, and plan to investigate the approach’s suitability to further diseases, in organs beyond the liver. Much work is still needed before trying prenatal editing in the human fetus, but optimism is growing. Gene therapy experiments in fetal mice for Gaucher’s disease and beta thalassemia were reported earlier this year in Nature Medicine and Nature Communications. Researchers however used different approaches, supplying normal copies of the faulted gene or employing peptide nucleic acids to perform gene-editing.