U.K. regulators on Thursday approved a therapy that uses CRISPR gene editing technology to treat two blood disorders. U.S. federal regulators are poised to approve that same treatment in December.
The exa-cel therapy, which goes by the brand name Casgevy, is the world’s first CRISPR therapy for humans to be approved for the market.
CRISPR is a gene editing technology that acts as a pair of “genetic scissors,” allowing scientists to edit sections of DNA by “snipping” specific portions of it and replacing them with new segments. First announced in a 2012 paper, CRISPR is celebrated as a cheap and easy way to edit genes.
Its inventors won the Nobel Prize in chemistry in 2020. In recent years, applications in plant manipulation and research on possible use in humans have proliferated as the technology has been promoted as a potential solution to problems running from disease, to food security to climate change.
But that research has been highly controversial, and a long series of papers has been published detailing the unintended effects of CRISPR gene editing, which has been found to produce many types of serious unintended DNA damage.
Casgevy is designed to treat two blood conditions: sickle cell disease and beta thalassemia. Sickle cell disease, also known as sickle cell anemia, most commonly occurs in people of African or Caribbean descent. It can cause debilitating pain.
People with beta thalassemia, which can cause mild or severe anemia, can require regular blood transfusions.
Both genetic conditions are caused by errors in the genes for hemoglobin, a protein that lets red blood cells transport oxygen around the body — and both conditions can be fatal.
The therapy, developed by Vertex Pharmaceuticals and CRISPR Therapeutics, was approved after a sickle cell trial that followed only 29 out of a total of 45 participants for 16 months. Twenty-eight of those followed had no pain after one year, Nature reported.
In the clinical trial for beta thalassemia, 39 of the 42 trial participants did not need to have a red blood cell transfusion for at least 12 months after receiving Casgevy. They typically need blood transfusions every three to five weeks.
For both diseases, the treatment is administered by taking blood-producing stem cells out of the patient’s bone marrow and editing the genes using CRISPR, also known as CRISPR/Cas9, named for the protein used to cut the DNA.
The technology targets a gene called BCL11A that typically disrupts the production of a kind of hemoglobin typically made only by fetuses.
The Cas9 locates the gene and cuts the DNA strands to make the gene stop working. In the process, it unleashes the production of fetal hemoglobin, which doesn’t have the same abnormalities as adult hemoglobin in people with those blood disorders.
Prior to treatment, patients undergo an intense and risky treatment called “myeloablative conditioning,” which prepares their body to receive the gene-edited cells. The gene-edited cells are then infused back into the body after they are edited. Patients may need to spend months in the hospital before and after the treatment.
The treatment will likely be very expensive — roughly $2 million — as we enter the so-called “era of one-shot, multimillion-dollar genetic cures,” although the companies have not named the price.
