The U.S. Food and Drug Administration (FDA) on Friday approved a new gene therapy for sickle cell disease, following an earlier approval from the U.K. Medicines and Healthcare products Regulatory Agency (MHRA) in November. The approvals mark a significant milestone in developing novel gene-editing therapies.

Casgevy, a gene-based treatment from U.S. Vertex Pharmaceuticals and Swiss CRISPR Therapeutics, was indicated for the treatment of severe sickle cell disease (SCD) in patients aged 12 and older.

“SCD is a rare, debilitating, and life-threatening blood disorder, and we are excited to advance the field, especially for individuals whose lives have been severely disrupted by the disease, by approving the cell-based gene therapy,” said Nicole Verdun, director of the Office of Therapeutic Products within the FDA’s Center for Biologics Evaluation and Research, in a statement.

SCD is a group of inherited blood disorders. The primary problem in the disease is a mutation in hemoglobin, a molecular protein found in red blood cells that delivers oxygen to the body’s tissues.

The mutation causes red blood cells to develop a crescent or “sickle” shape. These sickled red blood cells restrict the flow in blood vessels and limit oxygen delivery to the body’s tissues, leading to severe pain and organ damage.

Bone marrow transplantation has been the only curative option for patients with SCD, but there have been reports of graft rejection caused following the transplantation.

Casgevy is a cell-based gene therapy based on CRISPR/Cas9, a type of gene editing technology that won the Nobel Prize in Chemistry in 2020.

In the therapy using the editing technology, physicians deactivate BCL11A, a gene preventing the body from making a form of hemoglobin found only in the fetus, by cutting its DNA. Following the editing in labs, the edited BCL11A is then reinfused into the patients.

During clinical trials, a total of 54 patients were treated with Casgevy. Of the total, 93 percent met the primary outcome without needing a transfusion for at least one year.

However, the obstacle preventing a broader use of the promising therapy is its high prices. Manufacturers expected Casgevy would be available at a list price of $2 million per patient in the U.S.

By Ko Jae-won and Han Yubin

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