Four seriously ill Chinese boys who would almost certainly have died in their twenties from a rare inherited disease received the same highly anticipated gene-editing drug.
More than a year later, a set of cruel and contradictory data emerged.
Two boys gained the strength to walk farther. One boy showed no improvement in gait and subsequently withdrew from the trial. And the fourth boy’s heart stopped beating 81 hours after receiving the medication intravenously, owing to a severe systemic immune storm and respiratory failure.