FDA Expands Casgevy Label to Children as Young as 2, Broadening Access to First CRISPR Gene Therapy for Sickle Cell Disease

The FDA has approved a supplemental biologics license application (sBLA) expanding the indicated age range for exagamglogene autotemcel; exa-cel (brand name Casgevy), the world's first approved CRISPR/Cas9-based gene therapy, to include patients as young as 2 years old with severe sickle cell disease (SCD).¹ The previous label restricted Casgevy's use to patients aged 12 and older. The expansion, granted to Vertex Pharmaceuticals and CRISPR Therapeutics, significantly broadens the eligible patient population for a one-time therapy that offers the prospect of functional cure in a disease that causes lifelong suffering beginning in infancy. The approval represents a continued evolution of CRISPR-based gene editing from milestone approval to clinical maturation across an expanding set of patient populations.

Why does early intervention in sickle cell disease make a clinical difference?

Sickle cell disease is an inherited hemoglobinopathy caused by a point mutation in the beta-globin gene, resulting in production of abnormal hemoglobin S (HbS) that polymerizes under low-oxygen conditions, deforming red blood cells into a characteristic sickle shape.² These sickled cells are rigid, sticky, and short-lived — they obstruct small blood vessels, triggering vaso-occlusive crises characterized by severe acute pain, and cause cumulative organ damage over time, including stroke, acute chest syndrome, renal failure, and cardiopulmonary complications.² End-organ damage accrues from early childhood, with stroke risk beginning as early as age two and increasing sharply through the teenage years.³

Intervening earlier in life offers the prospect of preventing this cumulative damage before it becomes irreversible. The label expansion to age 2 reflects both the clinical urgency of early treatment and the accumulating safety data supporting Casgevy's use in younger patients — a population in whom the benefit-risk profile must be carefully characterized given the intensity of the required conditioning regimen.¹

How does Casgevy work?

Casgevy is an autologous, ex vivo cell therapy in which the patient's own hematopoietic stem and progenitor cells (HSPCs) are harvested, edited using CRISPR/Cas9 technology at the erythroid-lineage-specific enhancer of the BCL11A gene, and reinfused following myeloablative conditioning with busulfan.² The BCL11A edit silences a transcriptional repressor, reactivating fetal hemoglobin (HbF) production — fetal hemoglobin does not sickle, and its re-expression at sufficient levels effectively suppresses HbS-driven disease pathology.²

As Tedd Elich, chief scientific officer at Life Edit Therapeutics, noted in a recent BioPharm International feature on CRISPR gene editing: "The approval of Casgevy for sickle cell disease is a significant milestone for the industry and paves the way for a wave of gene-edited therapies, including those that leverage next-generation CRISPR-based technologies with potentially more efficient and precise genome editors."

Casgevy is a one-time treatment — unlike chronic disease-modifying therapies such as hydroxyurea or voxelotor (now withdrawn), which require lifelong administration and provide incomplete disease control, a single infusion of exa-cel aims to produce durable HbF induction and sustained clinical benefit.

What clinical data support the pediatric expansion?

The original FDA approval of Casgevy in December 2023 was based on the pivotal CLIMB SCD-121 trial (NCT03745287), which enrolled patients aged 12 and older with severe SCD — defined by a history of vaso-occlusive crises.⁴ In that trial, 29 of 30 evaluable patients (97%) achieved freedom from severe vaso-occlusive crises for at least 12 consecutive months. Updated data presented in 2025 demonstrated durable responses and improvements in health-related quality of life across the treated population.⁵

The label expansion to age 2 draws on additional safety and efficacy data in younger patients, as well as the established pharmacology and mechanism supporting HbF induction across age groups. Vertex has not disclosed the specific dataset underpinning the pediatric expansion in its press materials, but the move follows a regulatory trajectory common to pediatric rare disease approvals — initial approval in older patients, with subsequent label expansion supported by smaller, age-appropriate datasets and pharmacokinetic modeling.¹

What does this mean for the sickle cell disease treatment field?

Casgevy's label expansion to age 2 positions it alongside Lyfgenia (lovotibeglogene autotemcel; lovo-cel), bluebird bio's lentiviral gene therapy also approved for SCD in December 2023, in an emerging field of one-time genomic medicines for this indication. Lovo-cel is currently indicated for patients aged 2 and older — meaning Casgevy's expansion now brings the two approved gene therapies into direct age-range alignment for the first time.¹

Access and affordability remain the most pressing challenges for both therapies. Casgevy is listed at approximately $2.2 million per treatment in the US. The manufacturing complexity of autologous cell therapy — which requires individual patient cell collection, shipment to a central manufacturing facility, editing, quality release, and reinfusion — limits treatment capacity and creates logistical barriers for younger, smaller patients whose HSPC mobilization and apheresis procedures require specialized pediatric expertise.

Lonza is manufacturing commercial supply of Casgevy at its facility in Geleen, the Netherlands, with plans to expand manufacturing to Portsmouth, New Hampshire, in the United States — a capacity build that will be essential as the eligible patient population grows with this label expansion.

References

1. Tirrell M. F(2026 Jul 6). FDA deepens Vertex's Casgevy label, opening treatment for patients as young as 2. Fierce Pharma. https://www.fiercepharma.com/pharma/fda-expands-use-vertexs-casgevy-patients-age-2-and-older
2. Sharma A, Boelens JJ, Cancio M, et al. (2023 Aug 31). CRISPR-Cas9 editing of the HBG1 and HBG2 promoters to treat sickle cell disease. N Engl J Med. https://pubmed.ncbi.nlm.nih.gov/37646679/
3. Leonard A, Kanter J. (2025 Dec 8). Clinical data comparison for FDA-approved gene therapies in sickle cell disease. Exp Biol Med (Maywood). https://pubmed.ncbi.nlm.nih.gov/41439171/
4. A Safety and Efficacy Study Evaluating CTX001 in Subjects With Severe Sickle Cell Disease. ClinicalTrials.gov. https://clinicaltrials.gov/study/NCT03745287
5. Sharma A, Locatelli F, Bhatia M, et al. (2025 Dec 23). Improvements in health-related quality of life in patients with severe sickle cell disease after exagamglogene autotemcel. Blood Adv. https://pubmed.ncbi.nlm.nih.gov/40857358/
6. Mirasol F. (2024 Feb 1). Milestone Approval to Steady Stream, Gene Editing Revs Up. BioPharm International. https://www.biopharminternational.com/view/milestone-approval-to-steady-stream-gene-editing-revs-up
7. Mirasol F. (2024. Sep 24). Lonza to Manufacture Commercial Supply of Vertex's Sickle Cell Disease Gene-Edited Cell Therapy, CASGEVY. BioPharm International. https://www.biopharminternational.com/view/lonza-to-manufacture-commercial-supply-of-vertex-s-sickle-cell-disease-gene-edited-cell-therapy-casgevy