The remarkable timeline of a custom gene-editing therapy to save a newborn

In the boy's fourth month, researchers were meeting with the Food and Drug Administration to discuss regulatory approval for a clinical trial—a trial where KJ would be the only participant. They were also working with the institutional review board (IRB) at Children’s Hospital of Philadelphia to go over the clinical protocol, safety, and ethical aspects of the treatment. The researchers described the unprecedented speed of the oversight steps as being "through alternative procedures." In month five, they started toxicology testing in mice. In the mice, the experimental therapy corrected KJ's mutation, replacing the errant A-T base pair with the correct G-C pair in the animals' cells. The first dose provided a 42 percent whole-liver corrective rate in the animals. At the start of KJ's sixth month, the researchers had results from safety testing in monkeys: Their customized base-editing therapy, delivered as mRNA via a lipid nanoparticle, did not produce any toxic effects in the monkeys ... Read full article.