Sickle Cell Disease: FDA approves first CRISPR gene therapies

Casgevy, one of these treatments, is the first FDA-approved medication to make use of a revolutionary form of genome editing technique

Casgevy and Lyfgenia, two ground-breaking medications that constitute the first cell-based gene therapies for treating sickle cell disease (SCD) in individuals 12 years of age and older, were authorized by the U.S. Food and Drug Administration (FDA). Moreover, Casgevy, one of these treatments, is the first FDA-approved medication to make use of a revolutionary form of genome editing technique, indicating a significant breakthrough in the area of gene therapy.

Red blood cells are impacted by sickle cell disease (SCD), an inherited condition. The HBB gene, which codes for the production of hemoglobin, the protein that delivers oxygen in red blood cells, is mutated, which causes it. Under some circumstances, the mutant hemoglobin, known as hemoglobin S (HbS), can cause red blood cells to become stiff and appear like a sickle or crescent.1

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.

Gene therapy holds the promise of delivering more targeted and effective treatments, especially for individuals with rare diseases where the current treatment options are limited.

Nicole Verdun, M.D., director of the Office of Therapeutic Products

For individuals with sickle cell disease who have repeated vaso-occlusive crises and are 12 years of age or older, the cell-based gene therapy casgevy is licensed. The first treatment using CRISPR/Cas9, a kind of genome editing technology, to receive FDA approval is called Casgevy. Hematopoietic (blood) stem cells from patients are altered by CRISPR/Cas9 genome editing.

Targeted DNA cuts may be made with CRISPR/Cas9, making it possible to precisely alter (delete, add, or replace) the DNA that has been cut. When the patient receives the modified blood stem cells back, they engraft—attach and multiply—within the bone marrow, increasing the synthesis of fetal hemoglobin (HbF), a form of hemoglobin that helps carry oxygen to the body’s tissues. Elevated HbF levels in sickle cell disease patients stop red blood cells from sickling.

Lyfgenia is a cell-based gene therapy. It is licensed for the treatment of sickle cell disease individuals 12 years of age and older with a history of vaso-occlusive episodes. It modifies genetic material using a lentiviral vector, a gene delivery vehicle. In the case of Lyfgenia, the patient’s blood stem cells undergo genetic modification to provide HbAT87Q, a hemoglobin created via gene therapy that works similarly to hemoglobin A, the typical adult hemoglobin produced in people without sickle cell disease. HbAT87Q-containing red blood cells are less likely to sickle and obstruct blood flow. The patient is subsequently given these altered stem cells.

During a hematopoietic stem cell transplant, the patient’s modified blood stem cells are used to make both products, which are then administered as a single-dose infusion once. A patient’s stem cells must be extracted before treatment, and high-dose chemotherapy known as myeloablative conditioning is required to eliminate bone marrow cells and replace them with the altered cells seen in Casgevy and Lyfgenia. Long-term research will monitor patients who have either Lyfgenia or Casgevy to assess each medication’s efficacy and safety.

These approvals represent an important medical advance with the use of innovative cell-based gene therapies to target potentially devastating diseases and improve public health.

Today’s actions follow rigorous evaluations of the scientific and clinical data needed to support approval, reflecting the FDA’s commitment to facilitating development of safe and effective treatments for conditions with severe impacts on human health.

Peter Marks, M.D., Ph.D., director of the FDA’s Center for Biologics Evaluation and Research.

Source: FDA Press release

Reference: 1. Chat GPT/Sickle Cell Diseases

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