In a landmark decision, the US Food and Drug Administration has approved two gene therapies for sickle cell disease, including the first treatment ever approved that uses the gene-editing technology called CRISPR, in patients 12 years and older.
About 50 lakh to 77.4 lakh people worldwide are living with sickle cell disease. It is more prevalent in Africa and India.
Sickle cell disease is an inherited disorder that causes a mutation in haemoglobin, a protein found in red blood cells, causing it to become crescent or sickle shaped and prevent blood from flowing easily to the rest of the body. This blockage can lead to serious problems, including stroke, organ damage, excruciating pain, and potentially early death.
Exa-cel, developed by Vertex and CRISPR Therapeutics, edits the defective gene that causes the development of crescent-shaped blood cells using CRISPR technology and the modified blood stem cells are transplanted back into the patient.
The second treatment, Lyfgenia, uses a common gene therapy method to add a functional gene that enables production of adult haemoglobin that does not form into the crescent shape associated with the disease.
Both gene therapies can take several months and use the patients’ own blood stem cells, which are modified, and are given back as a one-time, single-dose infusion as part of a blood stem cell transplant. After the stem cells are collected, the patient must undergo high-dose chemotherapy that removes cells from the bone marrow so they can be replaced with the modified cells. Both therapies are intended to be a one-time treatment that will alleviate symptoms for a lifetime.
But both therapies are extremely expensive, costing more than $2.2 million per patient, which may be out of reach for most patients.
CRISPR technology that involves repairing DNA mutations will potentially lead to more innovative therapies for inherited and chronic diseases.
