This is the first licensed therapy in the world based on thegene editing technology Crispr-Cas9 that earned its innovators a Nobel Prize in 2020.
About Casgevy
- The therapy edits the faulty gene that leads to these blood disorders, potentially curing the person for life. So far, the only permanent treatment has been a bone marrow transplant, for which a closely matched donor is needed.
- The “genetic scissors” that became available for the first time in 2012 have revolutionised the field of biotechnology.
Working of Therapy
● Both sickle cell disease and thalassaemia are caused by errors in the gene for haemoglobin, a protein in the red blood cells that carry oxygen to organs and tissues.
● The therapy uses the patient’s own blood stem cells, which are precisely edited using Crispr-Cas9. A gene called BCL11A, which is crucial for switching from foetal to adult haemoglobin, is targeted by the therapy.
● Foetal haemoglobin, which is naturally present in everyone at birth, does not carry the same abnormalities as adult haemoglobin. The therapy uses the body’s own mechanisms to start producing more of this foetal haemoglobin, alleviating the symptoms of the two conditions.
Sickle cell disease and Thalassemia
- The genetic error in sickle cell disease leads to red blood cells assuming a crescent shape. Unlike the disc shaped normal cells, the sickle-like cells cannot move around easily in the vessels, resulting in blocked blood flow. This can lead to episodes of severe pain, life-threatening infections, anaemia, or a stroke.
- An estimated 30,000-40,000 children in India are born with the disorder every year.
- The symptoms manifest in people who inherit a pair of damaged genes from both parents. Those who carry only one copy of the gene from one parent can lead a normal life. This is the same as thalassaemia, in which people who inherit a pair of genes from both parents experience symptoms like severe anaemia.
- Thalassaemia leads to low levels of haemoglobin, leading to fatigue, shortness of breath, and irregular heartbeats. People with the condition need blood transfusions throughout their life. The transfusions also lead to accumulation of excess iron in the body, for which they need chelation.
- India also has the largest number of children with thalassaemia major in the world — about 1-1.5 lakh.