Gene therapy for treating Sickle Cell Disease

Context

Recently, the UK drug regulator approved a gene therapy for the cure of sickle cell disease and thalassaemia.

More about the news

1. The first therapy based on gene editing technology Crispr-Cas9 for sickle cell disease and thalassaemia has been approved in the UK.
2. The “genetic scissors” that became available for the first time in 2012 have revolutionised the field of biotechnology.
3. The therapy is called as 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.

How does the therapy work?

1. Both sickle cell disease and thalassaemia are caused by errors in the gene for haemoglobin.

• Haemoglobin is a protein in the red blood cells that carries oxygen to organs and tissues.

2. The therapy uses the patient’s own blood stem cells, which are precisely edited using Crispr-Cas9.
3. A gene called BCL11A, which is crucial for switching from foetal to adult haemoglobin, is targeted by the therapy.
4. 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.

Challenges of this treatment

1. High Cost: Although the price of the therapy hasn’t been announced, it is likely to be very high. Estimates suggest it could be as much as $2 million per patient, which is in line with other gene therapies.
2. Absence of local manufacturing facilities: Another limitation is the absence of local manufacturing facilities, which means that the harvested blood stem cells have to be sent across countries.

CRISPR Technology

1. CRISPR stands for Clustered Regularly Interspaced Short Palindromic Repeats and was developed in the year 2012.
2. CRISPRs are specialised stretches of DNA.

Cas9:

1. The protein Cas9 (or “CRISPR-associated”) is an enzyme that acts like a pair of molecular scissors, capable of cutting strands of DNA.
2. It allows researchers to easily alter DNA sequences and modify gene function.

Treatment:

1. CRISPR-Cas9 technology was set to revolutionise medicine in the treatment of diseases such as sickle cell anaemia, for instance, and agriculture.

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