FDA Clears First CRISPR Gene Therapy for Children as Young as 2 After Trials Free Kids of Disease

The Food and Drug Administration has cleared the CRISPR gene-editing therapy exagamglogene autotemcel, sold as Casgevy, for children as young as 2 with severe sickle cell disease or transfusion-dependent beta thalassemia, extending a treatment that had been limited to patients 12 and older. The decision, granted July 1, makes exa-cel the first gene therapy approved for young children with sickle cell disease and the first CRISPR-based therapy to reach this age group in either condition.

The expansion followed results from two Phase 3, open-label studies that tested the therapy in children ages 5 to 11, published in The New England Journal of Medicine. In the trials, the treatment produced dramatic outcomes: children with beta thalassemia no longer required the regular blood transfusions their survival had depended on, while those with sickle cell disease became free of the excruciating vaso-occlusive crises that had repeatedly sent them to the hospital. Participants were followed for at least 16 months.

Exa-cel works by harnessing the same gene-editing tools that earned their inventors a Nobel Prize. Doctors collect a patient's own blood-forming stem cells and use CRISPR-Cas9 to make a precise cut in a region of DNA called the BCL11A erythroid enhancer. That edit switches back on the production of fetal hemoglobin, a form of the oxygen-carrying protein that is normally silenced after birth but can compensate for the defective adult hemoglobin behind both diseases.

Sickle cell disease and beta thalassemia are inherited blood disorders that disproportionately affect people of African, Mediterranean, Middle Eastern and South Asian descent. In sickle cell disease, misshapen red blood cells clog small vessels, causing bouts of severe pain, organ damage and strokes. In transfusion-dependent beta thalassemia, patients cannot make enough healthy hemoglobin and rely on lifelong transfusions that carry their own risks, including dangerous iron overload.

Because the therapy is made from each patient's own cells and edited outside the body before being reinfused, it is a one-time, personalized treatment rather than a drug taken repeatedly. The process is arduous — it requires harvesting stem cells and a round of chemotherapy to clear the bone marrow before the edited cells are returned — but for families who have spent years managing crises and transfusions, the prospect of a functional cure is transformative.

Doctors cautioned that access will remain a challenge. The therapy carries a list price in the millions of dollars, requires specialized medical centers, and demands months of treatment and monitoring, raising questions about how widely it can reach the children who might benefit most, particularly in lower-income countries where these blood disorders are most common. Still, physicians hailed the approval as a milestone, saying that curing children of diseases once considered lifelong marks a turning point for the young field of gene editing.