The United Kingdom Medicines and Healthcare products Regulatory Agency ("MHRA") made history today when it approved the medicine "Casgevy" for the treatment of sickle-cell disease and transfusion-dependent β-thalassemia in patients aged 12 and older. As the MHRA announced in a press release,
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.
Here's how Casgevy, developed by Vertex Pharmaceuticals in Boston, Massachusetts, and CRISPR Therapeutics in Zug, Switzerland, works:
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.
Sickle-cell disease and transfusion-dependent β-thalassemia are painful and debilitating conditions that disproportionately afflict the poor. Casgevy marks a landmark, heralding the beginning of CRISPR-based therapeutics approved for the market, and, more importantly, for the treatment of patients.