World-first gene-editing treatment for blood disorders including sickle cell disease approved for use in the NHS

The National Institute for Health and Care Excellence (NICE) has today approved a gene-editing treatment for use with NHS patients over the age of 12 with a severe form of sickle cell disease. 

Clinical trials of the treatment in the UK have been led by researchers at Imperial College Healthcare NHS Trust, as part of an international collaboration between academic researchers, industry partners and patients. 

The gene therapy, known as exa-cel or ‘Casgevy’ (exagamglogene autotemcel) is based on CRISPR gene editing. It was developed through a partnership between Vertex Pharmaceuticals and CRISPR Therapeutics and is based on the innovative gene-editing tool CRISPR – technology that led its inventors to win a Nobel prize in 2020.  

Exa-cel was also approved by NICE from August 2024 for people over the age of 12 with a severe form of thalassaemia, known as transfusion-dependent beta thalassaemia. The Trust is the UK’s leading arm for global clinical trials in both diseases. 

Both sickle cell disease and beta thalassaemia are genetic conditions caused by errors in the genes for haemoglobin, which are essential for carrying oxygen to all organs and tissues of the body. Sickle cell disease can cause severe pain, organ damage and shortened life span due to misshapen or “sickled” blood cells. Around 15,000 people in the UK have sickle cell disease and it is particularly common in people with African or Caribbean family background. 

Clinical trials suggest exa-cel can stop painful and unpredictable sickle cell crises – the most common symptom of sickle cell disease, where blood vessels become blocked causing severe pain.  

Beta thalassaemia affects red blood cells and can lead to severe anaemia. At the moment, patients with beta thalassaemia often need a blood transfusion every few weeks of their lives and complex medication to remove excess iron from their blood. 

To date, the only long-term cure option for the two blood conditions is a bone marrow transplant but optimal outcomes are only achieved from a closely matched donor. Transplants also carry a risk of rejection and complications and are only available to a small fraction of people living with the conditions. 

The treatment will be offered at specialist NHS centres in London, Manchester and Birmingham, and will be available for eligible patients over the age of 12 who experience recurrent sickle cell crises and would be suitable for a stem cell transplant but where a donor is not available. It is estimated that around 50 such patients will receive the cutting-edge treatment each year. A similar number of children and adults with sickle cell disease receive a stem cell transplant on the NHS each year. 

Professor Bob Klaber, director of strategy, research and innovation at Imperial College Healthcare NHS Trust said: "Together with patients and industry partners, we are proud to be part of the ground-breaking research and international academic collaboration that has made this treatment possible. 

“The treatment is an example of true medical innovation and will provide patients with no other options a potential cure for the painful, debilitating symptoms of their diseases. It also offers promising research avenues for other genetic diseases. 

"Sickle cell disease is more common in people from certain ethnic backgrounds and treatments have historically been lacking despite the global burden of disease. While we know there is much more work to be done to tackle health inequalities, it is a pivotal moment to see a curative treatment for sickle cell become available to NHS patients." 

How the gene editing treatment works  

Casgevy is designed to work by precisely editing the genes in a patient’s bone marrow stem cells to enable the production of a functioning haemoglobin.  

The treatment involves mobilising stem cells out of bone marrow and collecting them from patient’s blood. CRISPR gene editing technology is then used in a laboratory - a pair of molecular scissors cuts a strand of DNA at a specific site, essentially disabling the faulty gene. The edited cells are then infused back into the patient, allowing the body to produce functioning haemoglobin.  

In the two global clinical trials, 28 out of 29 sickle cell patients were free of severe pain and 39 of 42 beta thalassaemia patients no longer needed blood transfusions for at least a year. According to NHS data, there were just over 32,000 hospital admissions in England in 2023-24 for sickle cell disorders, of these admissions, almost 14,000 were admissions for sickle cell anaemia crises. 



Clinical trials at Imperial College Healthcare are supported by funding from the National Institute for Health and Care Research (NIHR) Imperial Biomedical Research Centre (BRC), a translational research partnership between Imperial College Healthcare NHS Trust and Imperial College London, which was awarded £95m in 2022 to continue developing new experimental treatments and diagnostics for patients.  

Vertex are one of the founding members of Paddington Life Sciences Partners. This partnership group is a key driver of the Trust’s Paddington Life Sciences development, which aims to create a thriving ecosystem for life sciences research and innovation in north west London.