TL;DR
For the first time, a single infusion carried a complete CRISPR gene editor into the muscles of boys with Duchenne muscular dystrophy, the inherited disease that slowly destroys muscle, and the edit took. In three boys it restored a small amount of the muscle protein they are born without. That is proof that a gene can be rewritten inside human muscle with one dose, which opens the door to one-time treatments for muscle diseases that today have none. The cost was severe: a fourth boy died about three and a half days after his infusion, from an immune reaction blamed on the virus-based carrier rather than the editor, and the trial stopped enrolling. The road ahead is clearer for it. The editing works; the delivery has to get safer, and the protein levels have to climb much higher before this changes the disease.
Below the line, for paid subscribers: The full story: where it stands, how we got here and what's dated next; our Odds board on 4 milestones, starting with "A one-time CRISPR treatment for Duchenne muscular dystrophy is available to patients by 2036"; our labeled speculation on what it adds up to; and every source.