Vertex CASGEVY Breakthrough: First Data in Children 5-11 at ASH 2025, Global Submissions Planned

Vertex Pharmaceuticals unveiled pivotal new data on CASGEVY (exagamglogene autotemcel), a CRISPR-based gene therapy, at the American Society of Hematology (ASH) Annual Meeting, marking the first clinical results in children ages 5-11 with severe sickle cell disease (SCD) or transfusion-dependent beta thalassemia (TDT).

Efficacy and safety profiles in this younger group align with the established benefits seen in patients 12 years and older, showing sustained fetal hemoglobin production and reduced disease crises.

Carmen Bozic, M.D., Executive Vice President, Global Medicines Development and Medical Affairs, and Chief Medical Officer at Vertex, said that these first-ever gene therapy data in children 5–11 with SCD underscore the transformative potential of CASGEVY. She added that with dosing completed in this age group and a Commissioner’s National Priority Voucher secured, Vertex plans to begin global regulatory filings in the first half of next year to bring this therapy to eligible children as soon as possible.

Pediatric Clinical Outcomes

In the Phase 3 CLIMB SCD-151 trial for SCD, all four evaluable children ages 5-11 achieved vaso-occlusive crisis (VOC)-free status for at least 12 consecutive months, with no VOCs post-infusion and follow-up durations up to 24.1 months.

For TDT in the Phase 3 CLIMB TDT-141 trial, all six evaluable patients reached transfusion independence for at least 12 months, sustaining hemoglobin levels above 9 g/dL on average. Safety remained consistent with older cohorts, including myeloablative conditioning effects, stable allelic editing, and elevated fetal hemoglobin.

Long-Term Data in Older Patients

Updated results from patients 12 years and older, as of April 2025, confirm enduring benefits: 100% (45/45) in SCD achieved VOC-free for 12+ months, averaging 35.3 months VOC-free duration. These findings from CLIMB-121 and long-term follow-up studies strengthen CASGEVY’s transformative potential in reducing crises and transfusions. No new safety signals emerged and it is aligned with prior approvals.

Regulatory and Access Expansion

CASGEVY, co-developed with CRISPR Therapeutics, is approved for ages 12+ in regions including the U.S., EU, UK, Canada, and several Middle East countries. Enrollment and dosing are complete for the 5-11 cohort, accelerating submissions to broaden access for younger patients facing early organ damage.

Haydar Frangoul, M.D., M.S., Medical Director of Pediatric Hematology and Oncology at Sarah Cannon Research Institute and HCA Healthcare’s TriStar Centennial Children’s Hospital, said he has witnessed the transformative impact of CASGEVY in patients 12 years and older in both trials and early commercial use. He expressed excitement about potentially offering this option to younger patients soon, early in life, before the most serious consequences of SCD or TDT develop.

About CASGEVY

CASGEVY uses ex vivo CRISPR/Cas9 editing of patients’ hematopoietic stem cells at the BCL11A enhancer to boost fetal hemoglobin, countering defective adult hemoglobin in SCD and TDT. This one-time autologous therapy could prevent cumulative damage in children if approved. Vertex’s ASH presentation positions CASGEVY as a leader in gene-edited treatments for hemoglobinopathies.

For full details on CASGEVY’s CRISPR mechanism, treatment process, safety, and prior approvals, see our March 2025 article: “CASGEVY: Revolutionizing Gene Therapy with CRISPR Technology to Treat Transfusion-Dependent Beta Thalassemia.”