First CRISPR Gene Therapy Approved

- The treatment, developed by Vertex Pharmaceuticals and CRISPR Therapeutics, works by editing a patient's own blood stem cells outside the body. These modified cells are then infused back into the patient. - The therapy utilizes CRISPR/Cas9 technology to disable the *BCL11A* gene, which normally switches off the production of fetal hemoglobin shortly after birth. This allows the patient's cells to produce the fetal form of hemoglobin, which does not sickle. - Before receiving the edited cells, patients must undergo a preparatory regimen of high-dose chemotherapy to clear out their existing bone marrow, a process known as myeloablative conditioning. This procedure carries its own risks, including potential infertility. - In clinical trials for sickle-cell disease, 97% of evaluable patients (28 out of 29) were free from the severe pain crises characteristic of the disease for at least one year. For beta-thalassemia, 93% of evaluable patients (39 out of 42) no longer required regular red blood cell transfusions for at least 12 months. - The U.S. Food and Drug Administration (FDA) approved Casgevy on December 8, 2023, shortly after the UK's approval on November 16, 2023. The technology's inventors, Emmanuelle Charpentier and Jennifer Doudna, were awarded the Nobel Prize in Chemistry in 2020. - The list price for the one-time treatment in the United States is $2.2 million, not including the significant costs of hospitalization, cell collection, and chemotherapy. - On the same day it approved Casgevy, the FDA also approved a second gene therapy for sickle cell disease called Lyfgenia, developed by Bluebird Bio. Lyfgenia uses a different technology involving a lentivirus to deliver a functional hemoglobin gene and is priced at $3.1 million.