MEDISEARCHER NEWS
United Kingdom · Gene editing & inherited blood disorders · 31 October 2026
In brief
- The UK has expanded the authorisation of Casgevy, allowing eligible children from age five with severe sickle cell disease or transfusion-dependent beta thalassaemia to receive the CRISPR gene-editing treatment.
- Casgevy was previously authorised in the UK only for patients aged 12 and over.
- Peer-reviewed Phase III studies specifically involving children aged 5 to 11 have produced encouraging early results for both diseases.
- Among children with sufficient follow-up in the published analysis, all eight evaluable beta-thalassaemia patients achieved at least 12 months without transfusions and all eight evaluable sickle-cell patients achieved at least 12 months without severe vaso-occlusive crises.
- Treatment is intensive and requires stem-cell collection, laboratory gene editing and myeloablative conditioning before the modified cells are returned to the patient.
- Serious adverse events occurred in the paediatric studies, including two cases of severe veno-occlusive liver disease attributed to busulfan conditioning, one of which was fatal.
- The UK’s expanded authorisation does not automatically mean Casgevy is immediately available through the NHS to every eligible child aged five and over.
- The current EU authorisation still starts at age 12, meaning the UK now permits Casgevy at a younger age than the European Union.
The UK medicines regulator has approved the gene-editing treatment Casgevy for eligible children as young as five with two serious inherited blood disorders, significantly expanding access to one of the world’s first approved CRISPR-based medicines.
The Medicines and Healthcare products Regulatory Agency (MHRA) announced on 30 October that Casgevy (exagamglogene autotemcel) can now be used in eligible children aged five and over with severe sickle cell disease or transfusion-dependent beta thalassaemia.
Casgevy was previously authorised in the UK for patients aged 12 and over.
The extension is particularly significant because peer-reviewed Phase III evidence is now available specifically in children aged 5 to 11, providing clinical evidence behind the move into younger patients.
What has changed for Casgevy in the UK?
The MHRA granted the marketing-authorisation extension on 29 October 2026 and publicly announced the decision the following day.
The expanded authorisation covers eligible children aged five and over with:
- severe sickle cell disease, an inherited disorder in which abnormal haemoglobin can cause red blood cells to become rigid and sickle-shaped, potentially leading to severe pain episodes, anaemia, infections and organ damage; or
- transfusion-dependent beta thalassaemia, an inherited blood disorder causing severe anaemia that can require blood transfusions every few weeks.
The MHRA estimates that approximately 15,000 people in the UK have sickle cell disorder.
How does Casgevy gene editing work?
Casgevy is fundamentally different from a conventional medicine taken as a tablet or injection.
It is an individualised cell therapy made using a patient’s own blood-forming stem cells.
Stem cells are collected from the patient and genetically edited outside the body using CRISPR/Cas9 technology.
The editing targets a regulatory region of the BCL11A gene, allowing the modified cells to produce increased amounts of fetal haemoglobin.
Fetal haemoglobin is a form of haemoglobin produced naturally before birth and during early infancy. Increasing its production can compensate for the defective adult haemoglobin underlying sickle cell disease and beta thalassaemia.
After the cells have been edited, the patient undergoes conditioning treatment to prepare the bone marrow. The modified stem cells are then infused back into the patient, where they can establish themselves in the bone marrow and produce new blood cells containing functioning haemoglobin.
What did the Phase III trials in children find?
Importantly, the expanded authorisation is supported by clinical evidence specifically involving younger children rather than being extrapolated solely from studies in teenagers and adults.
Peer-reviewed results published in the New England Journal of Medicine in 2026 reported findings from two ongoing Phase III studies of exagamglogene autotemcel in children aged 5 to 11.
At the time of the published analysis, 15 children with transfusion-dependent beta thalassaemia and 11 children with sickle cell disease had received Casgevy.
The primary endpoints were demanding: children with beta thalassaemia had to achieve transfusion independence for at least 12 consecutive months, while children with sickle cell disease had to remain free from severe vaso-occlusive crises for at least 12 consecutive months.
All evaluable children met the primary efficacy endpoints
Among children who had accumulated enough follow-up to be evaluated against the primary endpoints, the results were encouraging.
- 8 of 8 evaluable children with transfusion-dependent beta thalassaemia achieved transfusion independence for at least 12 consecutive months.
- 8 of 8 evaluable children with sickle cell disease remained free from severe vaso-occlusive crises for at least 12 consecutive months.
The remaining treated children had not necessarily failed treatment. Several had simply not yet accumulated the required duration of follow-up to be included in the primary endpoint analysis.
The studies are ongoing, meaning longer-term evidence will continue to accumulate.
Casgevy is not a simple one-shot treatment
Although Casgevy is often described as a one-time gene-editing therapy, receiving it involves a complex and intensive medical process.
A patient’s blood-forming stem cells must first be collected and sent for laboratory gene editing.
Before the edited cells can be returned, patients undergo myeloablative conditioning using chemotherapy to clear space in the bone marrow for the modified stem cells.
The paediatric Phase III studies used busulfan for this conditioning.
After the edited cells are infused, patients require specialist monitoring and may remain in hospital while the cells establish themselves and normal blood-cell production recovers.
What did the paediatric studies show about safety?
The efficacy results need to be considered alongside the risks associated with the overall treatment procedure.
In the published Phase III analysis, all 26 treated children experienced at least one grade 3 or 4 adverse event.
Many adverse events were consistent with the known effects of stem-cell transplantation and myeloablative conditioning rather than the gene-editing mechanism itself.
However, two children with transfusion-dependent beta thalassaemia developed severe hepatic veno-occlusive disease following busulfan conditioning.
One of those children died.
The investigators attributed the liver complications to the busulfan conditioning regimen rather than to Casgevy itself, but the events underline an important distinction: gene editing may occur in a patient’s own cells, but the complete treatment remains an intensive stem-cell procedure carrying potentially serious risks.
Long-term monitoring is also important because CRISPR-edited cell therapies remain relatively new and their durability and safety need to be followed over many years.
Is Casgevy a cure for sickle cell disease?
Casgevy is designed as a potentially transformative one-time treatment that addresses the underlying biology of sickle cell disease and beta thalassaemia rather than simply controlling individual symptoms.
For some patients, successful treatment can eliminate severe vaso-occlusive crises or the need for regular blood transfusions for prolonged periods.
However, describing Casgevy as a guaranteed “cure” for every patient would overstate the evidence.
The paediatric studies are still ongoing, the number of younger children treated remains relatively small and longer follow-up is required to determine how durable the benefits remain over decades.
UK now permits Casgevy at a younger age than the EU
The new decision creates an important regulatory difference between the United Kingdom and European Union.
The European Medicines Agency currently authorises Casgevy for eligible patients aged 12 years and older with transfusion-dependent beta thalassaemia or severe sickle cell disease.
The UK’s expanded authorisation now starts at age five for eligible patients.
This means younger children can now fall within the authorised Casgevy indication in the UK while remaining below the currently authorised age threshold in the EU.
The difference could change if European regulators subsequently assess an application to expand the EU indication.
Does MHRA approval mean Casgevy is now available on the NHS to children from age five?
Not automatically.
Medicines authorisation and publicly funded NHS access are separate processes.
The MHRA determines whether a medicine can be marketed for a particular indication based on its quality, safety and effectiveness.
NHS access in England can additionally depend on recommendations from the National Institute for Health and Care Excellence (NICE), commissioning arrangements and the specialist centres capable of delivering treatment.
Existing NICE recommendations for Casgevy were developed for people aged 12 and over.
For severe sickle cell disease, NICE currently recommends Casgevy with managed access for certain patients aged 12 and over who meet specific disease and transplant criteria.
NICE has also recommended Casgevy with managed access for eligible people aged 12 and over with transfusion-dependent beta thalassaemia.
The new MHRA authorisation therefore should not be interpreted as confirmation that every child aged five to 11 who meets the medicine’s regulatory indication can immediately receive NHS-funded treatment.
Why treating children earlier could matter
Both diseases begin early in life and can cause cumulative health damage.
Children with severe sickle cell disease can experience repeated episodes of extreme pain, serious infections, anaemia and progressive organ complications.
Children with transfusion-dependent beta thalassaemia may require regular blood transfusions from a young age, alongside treatment to manage iron accumulation caused by repeated transfusions.
A treatment capable of substantially changing blood-cell production earlier in childhood therefore has the potential to reduce years of disease burden if its benefits prove durable.
But determining which children have an appropriate benefit-risk profile for such intensive treatment remains a specialist clinical decision.
What happens next?
The immediate regulatory change is clear: eligible UK patients can now fall within Casgevy’s authorised indication from age five rather than age 12.
The MHRA says it will continue monitoring the treatment’s safety and effectiveness.
The ongoing paediatric Phase III studies should provide additional information as more children reach the required follow-up periods and existing participants are monitored for longer.
Attention will also turn to how the expanded authorisation translates into practical access for younger patients through the NHS and whether regulators elsewhere, including the European Union, follow the UK in lowering the authorised age.
Why the Casgevy expansion matters
Casgevy was one of the first CRISPR/Cas9 gene-editing treatments to receive regulatory approval, turning a technology once largely associated with laboratory research into a treatment for serious inherited disease.
Extending its UK authorisation from age 12 to age five represents another important step in that transition.
The paediatric Phase III results provide encouraging evidence that the treatment can deliver major clinical benefits in younger children, including sustained freedom from transfusions or severe sickle-cell crises among those evaluable so far.
At the same time, the serious complications associated with the conditioning process demonstrate why Casgevy should not be portrayed as a simple genetic cure.
It is a highly specialised treatment combining gene editing with intensive stem-cell transplantation procedures, and the long-term balance between its potentially transformative benefits and risks will become clearer as more children are treated and followed over time.
Reviewed by: Dr Mattias Hagman, PhD
Editorial review: This article was reviewed for interpretation of the UK Casgevy authorisation extension, the paediatric Phase III efficacy and safety evidence, the distinction between gene-editing treatment and conditioning-related risks, current EU authorisation, and the difference between MHRA approval and NHS-funded access.
Last reviewed: 31 October 2026
Sources and verification
MediSearcher reviewed the following primary and authoritative sources when preparing this article:
- MHRA: Casgevy gene-editing treatment approved for children aged five and over with serious inherited blood disorders
- New England Journal of Medicine: Exa-cel in children with transfusion-dependent β-thalassaemia or sickle cell disease — Phase III paediatric results
- European Medicines Agency: Casgevy European Public Assessment Report and current EU indication
- NICE: Exagamglogene autotemcel for treating severe sickle cell disease in people aged 12 years and over
- NICE: Exagamglogene autotemcel for treating transfusion-dependent beta thalassaemia in people aged 12 years and over
This article is for general informational purposes only and is not medical advice. Casgevy is a highly specialised gene-edited cell therapy requiring conditioning treatment and specialist care. Regulatory authorisation does not mean that every patient with sickle cell disease or beta thalassaemia is eligible for treatment or has immediate access through the NHS. Patients and families should discuss treatment options with an appropriately qualified specialist healthcare team.