US FDA approves two gene therapies to treat patients with sickle cell disease

WASHINGTON DC: The US Food and Drug Administration approved two gene therapies for the treatment of sickle cell disease (SCD) in patients aged 12 years and above. Casgevy, a cell-based gene therapy, is approved for the treatment of sickle cell disease in patients 12 years of age and older with recurrent vaso-occlusive crises, the FDA announced in a statement. Casgevy is the first FDA-approved therapy utilising CRISPR/Cas9, a type of genome editing technology.

Lyfgenia is a cell-based gene therapy that uses a lentiviral vector for genetic modification and is approved for the treatment of patients aged 12 years and above with sickle cell disease and a history of vaso-occlusive events, according to FDA statement. In the statement, FDA stated, "With Lyfgenia, the patient's blood stem cells are genetically modified to produce HbAT87Q, a gene-therapy-derived haemoglobin that functions similarly to haemoglobin A, which is the normal adult haemoglobin produced in persons not affected by sickle cell disease."

"Red blood cells containing HbAT87Q have a lower risk of sickling and occluding blood flow. These modified stem cells are then delivered to the patient," it added. Peter Marks, MD, PhD, director of the FDA's Center for Biologics Evaluation and Research, called these approvals an important medical advance. The FDA granted approval of Casgevy to Vertex Pharmaceuticals Inc and approval of Lyfgenia to Bluebird Bio Inc.

In the statement, Peter Marks said, "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." He added, "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."

Sickle cell disease is a group of inherited blood disorders affecting approximately 100,000 people in the US. It is most common in African Americans and, while less prevalent, also affects Hispanic Americans, according to the FDA. The primary problem in sickle cell disease is a mutation in haemoglobin. This mutation causes red blood cells to develop a crescent or "sickle" shape.

These sickled red blood cells restrict the flow in blood vessels and restrict oxygen delivery to the tissues of the body, leading to severe pain and organ damage called vaso-occlusive events (VOEs) or vaso-occlusive crises (VOCs), FDA said in a statement. The recurrence of these events or crises can cause life-threatening disabilities and/or early death, according to the FDA.