Why is it in the news?

• The UK drug regulator approved Casgevy, marking a significant breakthrough in the treatment of sickle cell disease and thalassaemia.
• It’s the first licensed therapy in the world based on the Crispr-Cas9 gene editing technology, which won the Nobel Prize in 2020.

About Casgevy

• Casgevy works by editing the faulty gene responsible for these blood disorders. Both sickle cell disease and thalassaemia result from errors in the gene for haemoglobin, a protein in red blood cells that carries oxygen.
• Casgevy uses the patient’s own blood stem cells, which are precisely edited using Crispr-Cas9. The therapy targets a gene called BCL11A, which is crucial for switching from foetal to adult haemoglobin. By increasing the production of foetal haemoglobin, which lacks the abnormalities of adult haemoglobin, Casgevy alleviates the symptoms of these conditions.

• Casgevy is a one-time treatment. It involves collecting blood stem cells from the patient’s bone marrow through a process called These cells are then sent to a manufacturing site, where they are edited and tested, a process taking approximately six months.
• Before the transplant with the edited cells, the patient undergoes conditioning medication to clear the bone marrow of other cells that will be replaced by the modified cells. The patient typically stays in the hospital for at least a month to allow the edited cells to take up residence in the bone marrow and start producing red blood cells with normal haemoglobin.
• Side effects are similar to those associated with autologous stem cell transplants and include nausea, fatigue, fever, and an increased risk of infection.
• One of the significant challenges of this therapy is its potential cost. While the exact price hasn’t been announced, estimates suggest it could be as high as $2 million per patient. This high cost could limit accessibility, especially in lower-income countries where a significant portion of the affected population resides.