In a historic decision, the FDA approved the first Crispr based treatment for sickle cell disease, which is the first gene editing treatment for sickle cell to ever be approved in the United States.
Sickle cell disease is a group of inherited blood disorders affecting approximately 4.4 million people worldwide with approximately 80% from sub saharan africa. This disease affects approximately 100,000 people in the U.S. and it is most common amongst African Americans.
It is a genetic disease whereby the hemoglobin which is a protein in red blood cells that carries oxygen gets mutated and twists the red blood cells into a crescent or sickle shape, hence the name sickle cell disease. As a result, these new sickle shaped red blood cells cause blockages that prevent the flow of blood and oxygen to the body which leads to intense pain and other serious health complications.
While there are treatments that are currently used for sickle cell disease such as multiple prescription drugs, blood transfusions, stem cell/bone marrow transplants, the advantage of this Crispr based treatment is that it uses the patient's own blood stem cells rather than having to find a donor match which can be a very difficult process.
The Crispr Cas 9 system is a gene editing technique for which Jennifer Doudna and Emmanuelle Charpentier won the 2020 Nobel Prize in Chemistry for their pioneering work in advancing this technology. The Crispr system works by using an enzyme called Cas9 to essentially cut the DNA at specific places.
The name of this gene editing sickle cell treatment is called Casgevy and it's being made available by Vertex Pharmaceuticals and Crispr Therapeutics.
Essentially it works by obtaining a sample of the patient's blood, isolating the stem cells from the sample of blood collected, then using the Crispr Cas9 system to cut the part of the gene in the cells that would normally stop the production of fetal hemoglobin. Fetal hemoglobin is a healthy form of hemoglobin that carries oxygen, and is naturally produced during fetal development but typically stops shortly after birth. The idea behind this therapy is that they are telling the cells that they should continue making the fetal hemoglobin that would have otherwise stopped being made after birth. Finally, they grow these cells that are producing this fetal hemoglobin and then infuse it back into the patient.
While this is a monumental step for the sickle cell disease community, this treatment is said to cost around 2.2 million dollars, it does requires chemotherapy, patients could possibly have to stay in the hospital for many months and the potential off target effects that occur when using the Crispr Cas 9 system is also something to keep in mind. Although this is extremely exciting and a big step towards treating genetic diseases, the question then becomes how can we ensure that the availability of this treatment will be equitable and accessible for those that truly need it.
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