Exa‑cel Posts Complete Primary-End Point Responses in Early Pediatric Trials, With One Fatal Busulfan Event

Overview

• In CLIMB THAL-141, 6 of 13 dosed beta‑thalassemia patients have reached 12 months and all achieved transfusion independence; in CLIMB SCD-151, 4 of 11 dosed sickle cell patients evaluated reached 12 months and all were free of severe vaso-occlusive crises.
• Mean total hemoglobin reached normal levels by month six and remained stable, with increased fetal hemoglobin and no vaso-occlusive crises reported after infusion to date in evaluated sickle cell participants.
• Safety to date appears consistent with adolescent and adult experiences, but one child in THAL-141 died from busulfan-related veno-occlusive disease, a known conditioning risk without a proven prevention strategy.
• The treatment involves harvesting a patient’s blood stem cells, editing them with CRISPR/Cas9, and reinfusing them after chemotherapy-based marrow conditioning.
• Trials continue to accrue participants and extend follow-up, exa‑cel remains approved only for patients 12 and older, and investigators are considering future studies in children as young as two to four years.