New knowledge of the genes that affect sickle cell disease and beta thalassemia has allowed for advances in treatments for these diseases. Advances in technology have also helped with the creation of new treatments. Dr. Mitchell Weiss, who works at St. Jude’s Children’s Research Hospital, has said that genetic correction is necessary for treatment, and advances in knowledge and technology have made that correction possible. This CRISPR/Vertex treatment, called CTX001, has been shown to benefit the two patients who have received it. They experienced temporary, treatable side effects while also being freed from blood transfusions and symptoms for a short time. The outcome of this trial is very promising for the future of treatments for these diseases.
About Sickle Cell Disease
Sickle cell disease is a group of disorders, with the most well-known and severe type of this disease being sickle cell anemia. This disease affects one’s red blood cells, altering their shape so that it resembles a sickle. Hemoglobin, a protein that carries oxygen throughout the body, is affected in this disease. It causes the red blood cells to deform and get caught along the walls of the vessels, which creates blockages and stops blood flow. This condition is recessive, meaning that both parents must pass down the gene in order for a child to have the disease. It disproportionately affects people of African American descent, while also appearing more in those of Hispanic descent.
The symptoms of sickle cell disease include the swelling of hands and feet, symptoms of anemia like fatigue, jaundice, delayed growth, and pain crisis. Children who have this condition often only experience these symptoms while in a pain crisis, whereas adults will constantly feel the symptoms. Along with these symptoms, damage to the organs can occur due to the lack of blood flow to them. The spleen, liver, kidneys, brain, eyes, lungs, heart, joints, skin, and bones are all commonly affected by the lack of blood reaching them. As of now, the only cure for this disease is a blood and bone marrow transplant. The issue with this treatment is that not all people with sickle cell disease qualify for a transplant. Other methods of treatment exist, and they are commonly symptomatic and meant to prolong life.
About Beta Thalassemia
Beta thalassemia, like sickle cell disease, is a blood disease caused by an issue with hemoglobin, which is a deficiency in this case. This disease occurs as three different types, which are minor, intermedia, and major. These types relate to the severity of the symptoms, with people who have minor beta thalassemia often being asymptomatic and those who have major needing lifelong medical care. This disease is caused by a mutation on the hemoglobin beta gene.
Those who have a mutation on one copy of this gene often experience minor beta thalassemia while those who have mutations on both copies experience the intermedia or major types. The symptoms of this disease include fatigue, weakness, shortness of breath, dizziness, headaches, blood clots, pallor, and splenomegaly, which is an enlargement of the spleen. Treatments for beta thalassemia depend on the type one has. Those with major require blood transfusions, which can be harmful if they cause iron overloads. If the spleen is heavily affected, surgery can be done to correct it. There is also an FDA approved treatment called Thiotepa.
About the CRISPR Treatment
Two companies, CRISPR Therapeutics and Vertex Pharmaceuticals, have developed the drug CTX001 in order to combat the issues with hemoglobin. This drug aims to reactivate the hemoglobin that is affected by the mutated gene. By disabling the DNA brake on the production of fetal hemoglobin, the body can then produce healthy amounts of the protein and stop the symptoms of the diseases. It is given through the drawing of blood and blood-producing stem cells, which are then zapped with electricity in order to open the portal that the CRISPR treatment goes through. Busulfan treatment is used to destroy the bone marrow cells that carry the mutation, and cells that have been treated with CRISPR then infuse into the bloodstream and bone marrow to produce healthy red blood cells with the proper amount and form of hemoglobin. In both of the patients who participated in the trial, the treatment successfully grafted to the bone marrow. This treatment frees people from constant transfusions while also building up the hemoglobin levels. The doctors involved with the treatments have found that the side effects come mainly from the busulfan treatment and are typical.
The Future of Treatment
CRISPR Therapeutics and Vertex Pharmaceuticals have competition in the development of this type of treatment, as other companies are pursuing treatments that are based on genome editing and gene therapy. The amount of research being done in this field is very exciting for those who have diseases like sickle cell disease and beta thalassemia, as there are treatments being developed them that show promising results. Research on blood cancers is also being done by CRISPR, meaning that their technology can help more people. While more research needs to be done on this treatment before it can be approved by the FDA and marketed to the masses, this clinical trial brings excitement for those with these diseases.
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