The gene-editing therapy Casgevy delivered two milestones in one week. Daniel Cressy, a 23-year-old Louisiana man, became the first person in the Gulf South to be declared functionally cured of sickle cell disease after receiving the CRISPR-based treatment, announced on June 22. Meanwhile, the FDA expanded Casgevy’s approval to children as young as 2 for severe sickle cell disease and transfusion-dependent beta thalassemia — the first CRISPR therapy approved for that age group. In the...