The US Food and Drug Administration (FDA) has approved expanded use of Vertex Pharmaceuticals’ Casgevy (exagamglogene autotemcel) in children with one of two types of inherited blood disorders, marking the first such treatment authorised in this age group.
Vertex’s gene therapy was already approved in patients aged 12 years and over for the treatment of either sickle cell disease (SCD) with recurrent vaso-occlusive crises (VOCs) or transfusion-dependent beta thalassemia (TDT). With the FDA label expansion, Casgevy can now be given to children as young as two years for either blood disorder.
Expanding patient use continues a positive commercial journey for Casgevy, a product Vertex co-developed with biotech CRISPR Therapeutics. When the gene therapy was first approved by the FDA in adults in December 2023, it became the first approved medicine to use the CRISPR/Cas9 genome editing technology. The one-time therapy works by using CRISPR to edit genetic material, thereby modifying haematopoietic stem cells from the patient so that more foetal haemoglobin (HbF) is produced, which enhances oxygen delivery. The edited cells are then engrafted into the patient’s bone marrow.
SCD is caused by a mutation in the HBB gene that causes red blood cells to become rigid and sticky, which blocks delivery of oxygen to tissue. Thalassemia causes the body to have an abnormally low level of haemoglobin, also resulting in reduced oxygen delivery.
“With today’s decision, paediatric patients as young as two years of age can now access a critical additional treatment option to treat these debilitating, life-threatening diseases,” said Karim Mikhail, acting director of the FDA’s Center for Biologics Evaluation and Research (CBER).
For SCD, a Phase III clinical trial (NCT05329649) of 11 patients demonstrated Casgevy’s safety and effectiveness in younger age groups. All eight patients who were evaluable for efficacy were free from VOCs for at least a year.
The efficacy and safety of Casgevy in patients five years to less than 12 years of age with TDT were evaluated in a Phase III trial (NCT05356195) of 15 patients. Eight of the nine efficacy evaluable patients with TDT achieved transfusion independence for 12 consecutive months.
Vertex’s CEO Reshma Kewalramani said: “The remarkable consistency of results across age groups reinforces the potential of Casgevy to deliver durable, transformative benefits to those who have historically had limited options.”
For many in the industry, Casgevy is credited with ushering in a new era of precise and curative advanced therapies. It has also signalled the significance of reimbursement structures across healthcare systems. The list price of the drug in the UK, for example, is £1.65m per patient, but England’s NHS has negotiated a reimbursement agreement with Vertex to offer the gene therapy for free to eligible patients.
Casgevy generated global revenue of $116m in 2025, representing 64 patients receiving infusions. According to the company, around 90% of US patients had reimbursed access to the gene therapy.
Casgevy’s label expansion comes as the FDA pledges to advance more gene therapies for rare diseases. In December 2025, the agency’s leaders outlined a new pathway to expedite personalised therapies to market that can bypass certain requirements.
