FDA approves first use of CRISPR gene editing to treat sickle cell disease


The Food and Drug Administration (FDA) on Friday approved a new therapy for treating sickle cell disease, marking the first instance of CRISPR gene editing receiving approval from federal regulators.

The FDA approved on Friday two new treatments for sickle cell disease (SCD): Casgevy and Lyfgenia.

Casgevy, also known as exa-cel, is developed through a partnership between Vertex Pharmaceuticals and CRISPR Therapeutics. The treatment involves taking a sickle cell patient’s own stem cells, editing them to create more fetal hemoglobin and transplanting them back into the individual.

When more fetal hemoglobin is produced, red blood cells don’t become “sickle” shaped, which is what causes the complications and pain associated with the disease. About 100,000 people in the U.S. have sickle cell disease, which mostly affects Black patients.

“When our company was founded, we had a vision to translate CRISPR technology into multiple breakthrough therapies. So, this U.S. approval of the first-ever medicine using CRISPR gene editing is breathtaking, and a truly humbling moment for me personally and for the whole organization,” CRISPR Therapeutics Chairman and CEO Samarth Kulkarni said in a statement.

The FDA has approved the treatments for sickle cell disease patients 12 years and older.

“Sickle cell disease is a rare, debilitating and life-threatening blood disorder with significant unmet need, and we are excited to advance the field especially for individuals whose lives have been severely disrupted by the disease by approving two cell-based gene therapies today,” Nicole Verdun, director of the FDA’s Office of Therapeutic Products, said in a statement.

A bone marrow transplant has long been the only curative treatment for the disease, with an ideal donor usually being a fully related sibling. There is, however, only a 1-in-4 chance that a sibling will be a match, and most patients don’t have this option. Casgevy essentially makes a patient their own donor.

Lyfgenia is similarly a cell-based gene therapy in which stem cells are also genetically modified to produce HbAT87Q, a type of hemoglobin that also prevents red blood cells from becoming sickle-shaped.

The FDA has attached a black box warning on the label of Lyfgenia due to a risk of blood cancer occurring among patients who receive it. The agency said patients who receive Lyfgenia are advised to undergo lifelong monitoring for this risk.

Peter Marks, director of the FDA’s Center for Biologics Evaluation and Research, said the approval of these treatments marked an “important medical advance” to treat diseases and improve public health.

The safety and effectiveness of both Casgevy and Lyfgenia were demonstrated through months-long studies presented to the FDA. The agency said patients who receive these treatments will also be followed in a long-term study to further determine their safety and effectiveness.

In a briefing on Friday, FDA officials said a black box warning was placed on Lyfgenia due to two fatal cases of acute myeloid leukemia being observed during clinical trials for the drug. One case of myelodysplastic syndromes, a condition where blood-forming cells become abnormal, was also observed. 

“CASGEVY’s approval by the FDA is momentous: it is the first CRISPR-based gene-editing therapy to be approved in the U.S. As importantly, CASGEVY is a first-in-class treatment that offers the potential of a one-time transformative therapy for eligible patients with sickle cell disease,” Vertex CEO Reshma Kewalramani said in a statement.

Andrew Obenshain, CEO of bluebird bio, said in a statement, “Bringing LYFGENIA to people living with sickle cell disease is a milestone that bluebird has been working toward for almost a decade—and one that members of the sickle cell disease community have been waiting on for much longer.”

Though these treatments have the potential to help thousands of patients who would otherwise not have other curative options, the cost is also projected to be immense. In an SEC filing, Vertex put the wholesale cost of Casgevy as $2.2 million.

And concerns over off-target editing and unintended genetic alterations have long followed CRISPR gene editing. While this has not been observed in any of the trials conducted by Vertex, some FDA advisers did call for more inquiries into this potential issue when reviewing Casgevy earlier this year.

Updated: 2:48 p.m.

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