New FDA-Approved Gene-Editing Therapies for Sickle Cell Disease are ‘Game Changers’

By Steve Blanchard - December 22, 2023

Earlier this month, the U.S. Food and Drug Administration approved two gene-editing therapies for patients 12 years and older with severe sickle cell disease.

The disease involves a mutation in hemoglobin, a protein in red blood cells that provides oxygen to tissues. The mutation leads red blood cells to develop a crescent or sickle shape, which can restrict blood flow and cause severe pain and organ damage. 

The newly approved therapies have been dubbed “milestone treatments” and mark the first cell-based gene therapies for this debilitating and potentially life-threatening blood disorder that affects about 100,000 people in the U.S.

Casgevy is the first new therapy to use the gene-editing tool CRISPR. Lyfgenia is a second therapy that uses a different gene-editing tool called lentiviral vector.

graphic illustration normal red blood cells and sickle cell disease

Both could be game changers for those with sickle cell disease, according to Dr. Hany Elmariah of Moffitt Cancer Center’s Department of Blood and Marrow Transplant and Cellular Immunotherapy.

“There are some medications that can control the symptoms of sickle cell, but you want to cure it and get rid of it completely,” he said. “Before gene therapy, the only way to do that was with an allogeneic bone marrow transplant.”

An allogeneic bone marrow transplant involves replacing the patient’s blood and marrow with someone else’s who doesn’t have sickle cell. However, the procedure has risks such as graft-versus-host disease (GVHD), where the transplanted blood cells attack the patient’s body.

It’s a risk that can likely be avoided with the new FDA approvals, which will allow a patient’s own blood to be genetically modified and then re-infused into their body.

portrait of blockquote author

"The big advantage to this is there is no risk of GVHD."

- Dr. Hany Elmariah, Blood and Marrow Transplant and Cellular Immunotherapy Program

“The big advantage to this is there is no risk of GVHD,” Elmariah said. “The downside is gene therapy requires more intensive chemotherapy. We have to completely wipe out their bone marrow and blood to successfully infuse the genetically engineered cells.”

Side effects from chemotherapy are more likely with this new procedure, Elmariah said, but ultimately patients stop having symptoms of sickle cell.

The new treatment appears to be very effective in its first year and has shown an approximately 90% success rate in patients older than 12. However, there is a caveat to the new technology, Elmariah said, as there is not a lot of long-term data.

“We’re not sure what happens to the genetically modified cells after many years,” he said.

Sickle cell disease mostly impacts Black and non-white Hispanic people. Because it is a genetic disease, patients have it from birth and typically live to 50 to 60 years old.

Even though sickle cell disease is not cancer, Elmariah and his colleagues perform transplants for this group of patients at Moffitt. He said he hopes that Moffitt will one day offer this new gene-modifying therapy to patients in Florida.

“This is very exciting news, and this is one of the most impressive studies I’ve seen,” Elmariah said. “This is a real game-changer for sickle cell patients.”

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