How did CRISPR enable the first approved gene therapy for sickle cell disease?

The answer

In December 2023, the FDA approved Casgevy (exagamglogene autotemcel), the first CRISPR-based gene therapy, for sickle cell disease. Developed by Vertex Pharmaceuticals and CRISPR Therapeutics, it works by extracting a patient's bone marrow stem cells, using CRISPR-Cas9 to disable the BCL11A gene that suppresses fetal hemoglobin production, then reinfusing the edited cells. Fetal hemoglobin doesn't sickle like adult hemoglobin. In clinical trials, 29 of 31 patients were free of vaso-occlusive crises for at least 12 months post-treatment. The one-time treatment costs approximately $2.2 million. Sickle cell disease affects roughly 100,000 Americans and 20 million people worldwide, predominantly of African descent.