The treatment is basically a bone marrow transplant, which would typically use donor cells from another person; CRISPR lets you use the patient's marrow instead

The treatment is basically a bone marrow transplant, which would typically use donor cells from another person; CRISPR lets you use the patient's marrow instead, hopefully reducing rejection and other issues. You extract marrow and CRISPR it to get rid of the problem gene. Then you kill off all of the bone marrow in the patient, and replace it with the new stuff. That's a cure.