Cutting Edge Gene Therapy

Combing through scientific literature, Casgevy’s creators found that adults with genes that would normally produce sickle cell disease (SCD) or transfusion-dependent beta thalassemia (TDT), but who also had higher levels of fetal hemoglobin—produced by babies under 1 year, with a higher affinity for oxygen than adult hemoglobin—didn’t suffer as much from symptoms. For those with no fetal hemoglobin, SCD causes painful blockages and anemia—known as pain crises—while TDT necessitates monthly blood transfusions, costing an estimated $5.4 million over a lifetime. Using CRISPR technology, Casgevy harvests a patient’s blood-forming stem cells, and edits them (outside the body) to spur fetal hemoglobin production. Reinserted in the patient, they work to keep SCD and TDT symptoms at bay. In clinical trials, 93.5% of patients with SCD didn’t experience pain crises for at least a year after infusions. In Dec. 2023, the therapy became the first CRISPR-based therapy to receive FDA approval.