A new treatment for sickle-cell disease and transfusion-dependent β-thalassemia has been authorised by the Medicines and Healthcare products Regulatory Agency (MHRA) for patients aged 12 and over after a rigorous assessment of its safety, quality and effectiveness.
Casgevy is the first medicine to be licensed that uses the innovative gene-editing tool CRISPR, for which its inventors were awarded the Nobel Prize in 2020. Both sickle cell disease and β-thalassemia are genetic conditions caused by errors in the genes for haemoglobin, which is used by red blood cells to carry oxygen around the body. Sickle cell disease is particularly common in people with an African or Caribbean family background. β-thalassemia mainly affects people of Mediterranean, south Asian, southeast Asian and Middle Eastern origin.
In people with sickle cell disease, this genetic error can lead to attacks of very severe pain, serious and life-threatening infections, and anaemia (whereby your body has difficulty carrying oxygen). In people with β-thalassaemia, it can lead to severe anaemia. Patients often need a blood transfusion every 3 to 5 weeks, and injections and medicines throughout their lives.
Casgevy is designed to work by editing the faulty gene in a patient’s bone marrow stem cells so that the body produces functioning haemoglobin. To do this, stem cells are taken out of bone marrow, edited in a laboratory and then infused back into the patient after which the results have the potential to be life-long.
Julian Beach, Interim Executive Director of Healthcare Quality and Access at the MHRA said: "Both sickle cell disease and β-thalassemia are painful, life-long conditions that in some cases can be fatal. To date, a bone marrow transplant – which must come from a closely matched donor and carries a risk of rejection – has been the only permanent treatment option.
"I am pleased to announce that we have authorised an innovative and first-of-its-kind gene-editing treatment called Casgevy, which in trials has been found to restore healthy haemoglobin production in the majority of participants with sickle-cell disease and transfusion-dependent β -thalassaemia, relieving the symptoms of disease.
"The MHRA will continue to closely monitor the safety and effectiveness of Casgevy, through real-world safety data and post-authorisation safety studies being carried out by the manufacturer. I would like to thank the patients with lived experiences who engaged with us as part of the assessment process and gave us valuable insight into their lives and the challenges of managing their condition."
John James OBE, Chief Executive of the Sickle Cell Society said: "Sickle cell disorder is an incredibly debilitating condition, causing significant pain for the people who live with it and potentially leading to early mortality. There are limited medicines currently available to patients, so I welcome the news that a new treatment has been judged safe and effective, which has the potential to significantly improve the quality of life for so many."
In the clinical trial for sickle-cell disease, 45 patients have currently received Casgevy but only 29 patients have been in the trial long enough to be eligible for the primary efficacy interim analysis. Of these eligible patients, 28 (97%) were free of severe pain crises for at least 12 months after treatment.
In the clinical trial for transfusion-dependent β-thalassemia, 54 patients have currently received Casgevy but only 42 patients have been in the trial long enough to be eligible for the primary efficacy interim analysis. Of these, 39 (93%) did not need a red blood cell transfusion for at least 12 months after treatment. The remaining three had more than a 70% reduction in the need for red cell transfusions.
Side effects from treatment were similar to those associated with autologous (from a person’s own cells) stem cell transplants, including (but not limited to) nausea, fatigue, fever and increased risk of infection. No significant safety concerns were identified during the trials. Safety continues to be closely monitored by the MHRA and the manufacturer. Both trials are ongoing and further results will be made available in due course.
Casgevy is administered by taking stem cells out of a patient’s bone marrow and editing a gene in the cells in a laboratory. Patients must then undergo conditioning treatment to prepare the bone marrow before the modified cells are infused back into the patient. After that, patients may need to spend at least a month in a hospital facility while the treated cells take up residence in the bone marrow and start to make red blood cells with the stable form of haemoglobin.
The decision to authorise Casgevy has been endorsed by the government’s independent scientific advisory committee, the Commission on Human Medicines, after a robust review of the available evidence.
