Britain’s drugs regulator has approved a groundbreaking treatment for two painful and debilitating lifelong blood disorders, which works by “editing” the gene that causes them.
The Medicines and Healthcare products Regulatory Agency (MHRA) has given the green light for Casgevy to be used to treat sickle cell disease and beta thalassemia.
It is the first medicine licensed anywhere that works by deploying gene editing that uses the “genetic scissors”, known as CRISPR, for which its inventors won the Nobel prize for chemistry.
Casgevy’s developers hope the pioneering treatment could banish the pain, infections and anaemia sickle cell disease brings and the severe anaemia experienced by those with beta thalassemia.
About 15,000 people in the UK, almost all of African or Caribbean heritage, have sickle cell disease. About 1,000 – mainly of Mediterranean, south Asian, south-east Asian and Middle Eastern background – have beta thalassemia and need regular blood transfusions to treat their anaemia.
Experts in the illnesses hope Casgevy may be a cure, making it no longer necessary for people with the conditions to have a bone marrow transplant. Until now this has been the only treatment available, even though the body can reject the donor marrow.
The Sickle Cell Society welcomed the MHRA’s decision as a “historic moment for the sickle cell community” which “offers [them] newfound hope and optimism”.
The charity added that the approval of Casgevy, made by Vertex Pharmaceuticals, was “empowering the NHS to employ it as a groundbreaking therapeutic intervention for those grappling with this condition, [which is] marked by chronic anaemia, recurrent episodes of intense pain requiring hospitalisation, organ damage, an elevated risk of stroke and premature mortality”.
Sickle cell disease and beta thalassemia are genetic, or inherited, conditions caused by errors in the genes for haemoglobin, a protein that lets red blood cells transport oxygen around the body. Both conditions can be fatal.
The MHRA said: “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 lifelong.”
During that process, laboratory staff use the “genetic scissors” to edit, or cut, the DNA of the cells from the patient’s bone marrow, before the treated cells are put back through infusion.
The MHRA said patients may need to spend at least a month in hospital while the treated cells “take up residence in the bone marrow and start to make red blood cells with the stable form of haemoglobin”.
In a clinical trial of Casgevy for sickle cell disease, 28 of the 29 patients experienced no episodes of major pain – which can lead to them being hospitalised – for at least a year afterwards.
When the treatment was used for those with beta thalassemia, 39 of the 42 trial participants did not need to have a red blood cell transfusion for at least 12 months after receiving Casgevy.
Dr Sara Trompeter, a consultant haematologist at University College hospital London and expert in sickle cell disease, said: “Whilst curative treatments may not be suitable for all, gene therapy offers a real chance of cure for those who are not eligible for bone marrow transplants and so we are delighted that it has been approved by MHRA.”