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Britain Approves World’s First Gene Therapy for Sickle Cell Disease

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Britain's medicines regulator has authorized the world's first gene therapy treatment for sickle cell disease, offering hope to thousands of people in the U.K. suffering from this debilitating disease. The treatment, called Casgevy, is the first medicine licensed using the gene editing tool CRISPR, which won its makers a Nobel prize in 2020.

Relief for Patients with Sickle Cell Disease and Thalassemia

The Medicines and Healthcare Regulatory Agency approved Casgevy for patients with sickle cell disease and thalassemia who are 12 years old and over. Previously, bone marrow transplants were the only long-lasting treatment option, but they are arduous and come with unpleasant side effects.

Targeting the Genetic Mutation

Sickle cell disease and thalassemia are caused by genetic mutations that affect the protein in red blood cells responsible for carrying oxygen. People with sickle cell disease experience crescent-shaped blood cells that can block blood flow and cause excruciating pain, organ damage, and other serious health issues. Patients with thalassemia have severe anemia and often require regular blood transfusions.

Casgevy works by targeting the problematic gene in a patient's bone marrow stem cells, allowing the body to produce properly functioning hemoglobin. The treatment involves a course of chemotherapy, followed by taking stem cells from the patient's bone marrow and using genetic editing techniques in a laboratory to fix the gene. The altered cells are then infused back into the patient, providing a permanent treatment.

Promising Results

The decision to authorize gene therapy for sickle cell disease was based on a study of 29 patients, with 28 of them reporting no severe pain problems for at least one year after treatment. In a separate study for thalassemia, 39 out of 42 patients who received the therapy did not require a red blood cell transfusion for at least a year afterwards.

Affordability Concerns

Gene therapy treatments can be extremely costly, raising concerns about accessibility for those who would benefit the most. Vertex Pharmaceuticals, the maker of Casgevy, has not yet established a price for the treatment in Britain. However, in the U.S., experts estimate that prices up to around $2 million would be cost-effective. By comparison, current sickle cell treatments can cost up to $1.7 million for men and $1.6 million for women over their lifetime.

Next Steps

Casgevy is currently being reviewed by the U.S. Food and Drug Administration, with a decision expected early next month. If approved, it would be the second gene therapy for sickle cell disease considered by the agency.

Gene therapies in Britain must be recommended by a government watchdog before they are made available to patients in the national healthcare system. Vertex Pharmaceuticals is working with health authorities to secure reimbursement and access for eligible patients as quickly as possible.

Millions of people worldwide, including about 100,000 in the U.S., have sickle cell disease. It is more prevalent in places where malaria is or was common, such as Africa and India, and among certain ethnic groups, including people of African, Middle Eastern, and Indian descent.

AP Science Writer Laura Ungar in Louisville, Kentucky contributed to this report.

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