Gene Therapy May Be Effective for Younger Pediatric Patients With SCD, TDT

Exagamglogene autotemcel gene therapy (Casgevy) may be associated with freedom from vaso-occlusive crises (VOCs) in pediatric patients with sickle cell disease (SCD), as well as periods of transfusion independence among pediatric patients with transfusion-dependent beta thalassemia (TDT), according to new data from Vertex Pharmaceuticals. Representatives from the company presented the data at the American Society of Hematology’s 2025 Annual Meeting, held this week in Orlando, Fla.

In the phase 3 CLIMB-151 study, 11 patients (ages 5-11) with SCD received exagamglogene autotemcel. Among the four patients with sufficient follow-up, all had at least 12 consecutive months free from VOCs, with the longest reported duration approaching two years. No patient experienced a VOC following infusion during the follow-up period.

In the phase 3 CLIMB-141 study, 13 patients (aged 5-11 years) with TDT received the therapy. All six evaluable patients achieved at least 12 consecutive months of transfusion independence while maintaining a weighted average hemoglobin of at least 9 g/dL. Overall, 12 of 13 patients were transfusion-free following infusion, with the longest duration reported at just under two years. One patient died from pneumonia in the setting of multi-organ failure related to severe veno-occlusive disease from busulfan conditioning.

The company noted that children treated with exagamglogene autotemcel had durable increases in fetal hemoglobin and stable allelic editing, consistent with studies in older patients.

Exagamglogene autotemcel is currently approved for the treatment of SCD and TDT in people aged 12 years and older. Vertex plans to initiate global regulatory filings for patients aged 5-11 years in the first half of 2026.