Gene therapy Casgevy approved for NHS use

The gene therapy Casgevy is now available on the NHS in England for people living with severe forms of beta-thalassaemia and sickle cell disease

As we reported in a previous article, in November 2023 the Medicines and Healthcare products Regulatory Agency (MHRA) approved the CRISPR-based gene therapy Casgevy for use in treating sickle cell disease and transfusion-dependent beta-thalassaemia in the UK. However, several months later (in March 2024), NICE withheld approval for use in the NHS: in its draft guidance, it stated that more information was needed before a decision could be made.

Since our previous post, NICE has further considered the use of Casgevy in the NHS – taking into account the evidence for the effectiveness of the treatment, as well as its cost. In September 2024 it approved its use to treat beta-thalassaemia; later, in February 2025, it extended its approval to include the treatment of sickle cell disease.

Across the NHS in England, people of 12 years and over with a severe form of sickle cell disease or transfusion-dependent beta-thalassaemia, for whom a stem cell transplant donor cannot be found, will now be eligible for treatment with Casgevy. The gene therapy has a list price of £1.65 million per patient; however, the NHS has reportedly negotiated a confidential discount, and the treatment will be offered through the Innovative Medicines Fund, which fast-tracks funding for new medicines.

How can Casgevy help patients?

Beta-thalassaemia and sickle cell disease are inherited blood disorders caused by different variants in a single gene that codes for haemoglobin, an essential blood protein that carries oxygen around the body. Currently, the main treatment for both conditions is stem cell transplantation; however, as with all transplants, it can be difficult to find a donor.

During Casgevy treatment, blood stem cells are taken from the patient and edited outside the body: CRISPR/Cas9 genome editing is used to precisely cut a strand of DNA at a specific site on BCL11A, the faulty adult haemoglobin gene. Modification of BCL11A results in the reactivation of fetal haemoglobin production. The patient undergoes chemotherapy and radiotherapy to wipe out their immune system; then, through a single-dose infusion of Casgevy – that is, their own modified stem cells – the production of a functioning haemoglobin gene is enabled and their immune system is rebuilt.

• To learn more about how Casgevy works, see our previous blog article.

Initial reports from the NHS front line have been positive. Beta-thalassaemia patient Tim Chronis, who was the first person to receive Casgevy on the NHS, has said, “My check-ups so far have been very encouraging. I’ve seen my blood counts increasing on their own for the first time ever… It’s quite a privilege. I feel very lucky.”

A short history of Casgevy

Casgevy is the brand name for exagamglogene autotemcel (exa-cel), formerly known as CTX00. It was developed by Vertex Pharmaceuticals in Boston, Massachusetts, USA, in partnership with CRISPR Therapeutics in Zug, Switzerland.

Preclinical development validated CRISPR/Cas9 genome editing as an approach to target the BCL11A gene, which led to Casgevy advancing to human trials. In June 2020, two patients with beta-thalassaemia and one with sickle cell disease received the gene therapy. The two beta-thalassaemia patients were transfusion independent at five and 15 months after treatment, and the sickle cell patient was free from painful crises at nine months after treatment.

Further clinical trials provided more evidence that Casgevy was effective, and the trials achieved their primary outcomes: a year after treatment, 39 of 42 beta-thalassaemia patients no longer needed blood transfusions. The remaining three had their need for blood transfusions reduced by over 70%. In addition, 28 of 29 sickle cell disease patients were free of severe pain.

Casgevy has been authorised in countries all over the world – including the US, Austria, Germany, Italy and Saudi Arabia. Here in the UK, Vertex Pharmaceuticals plans to follow up with patients for 15 years to collect more data on the treatment’s safety – and experts hope that its positive effect on patients’ lives will continue to be felt in the long term. As Tim Chronis says, “It would be fantastic if I could just live the rest of my life without having to worry…”