Gene Editing Therapy Shows Early Benefit for Patients With SCD and Beta Thalassemia

CRISPR Therapeutics and Vertex Pharmaceuticals have reported that the first two patients to receive an experimental gene editing treatment for SCD and beta thalassemia have experienced clinical benefit, with treatable, temporary AEs.

The treatment, called CTX001, might have the potential to cure both forms of anemia by reactivating the body’s ability to produce fetal hemoglobin (HbF). CTX001 uses CRISPR to edit the BCL11A gene, which modulates HbF, thereby increasing HbF production. Following busulfan treatment, the edited cells are infused into the patient’s bloodstream, engrafting in the bone marrow to ideally produce HbF.

Victoria Gray, the patient with SCD who received the CRISPR treatment in July, has not experienced a vaso-occlusive crisis since infusion. In the two years before treatment, she had suffered about seven crises per year. Four months after the therapy, her blood tests showed normal hemoglobin levels, 46.6% of which was HbF. AEs related to her treatment included sepsis, gallstones, and abdominal pain.

The other patient, who had beta thalassemia major that required approximately 16 transfusions per year, also became transfusion-independent after receiving CTX001. Nine months after the treatment, her total hemoglobin – 99.8% of which was HbF – reached near-normal levels. She experienced AEs including pneumonia, neutropenia, and jaundice.

The trial of CTX001 for SCD will eventually include 45 patients from the U.S., Europe, and Canada, while the beta thalassemia trial will involve 45 patients in the U.K., Canada, and Germany. Researchers will follow up with the patients for 15 years after treatment.

Sources: STAT, November 19, 2019; NPR, November 19, 2019.