In a groundbreaking decision, the FDA has given the green light to two new drugs for treating sickle cell disease in patients aged 12 and above. Among them is Vertex’s Casgevy, a significant milestone as it marks the first approved application of the CRISPR genome editing technology in the United States. Bluebird Bio’s Lyfgenia, another approved drug, is a cell-based gene therapy utilizing a distinct gene modification technique to deliver modified stem cells to patients.
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These approvals open up novel avenues for sickle cell disease treatment, an inherited blood disorder characterized by red blood cells unable to effectively carry oxygen, resulting in painful vaso-occlusive crises (VOCs) and organ damage. The disease disproportionately affects African Americans and, to a lesser extent, Hispanic Americans. While bone marrow transplants remain the sole cure for sickle cell disease, their success depends on well-matched donors and often involves complications.
Despite both drugs utilizing gene editing techniques, Casgevy’s CRISPR/Cas9 genome editing involves cutting out or splicing in DNA in specific areas. Patients undergo a process where their blood is drawn for the isolation and editing of their own stem cells using CRISPR. Subsequently, they undergo a form of chemotherapy to remove some bone marrow cells, allowing the edited stem cells to be transplanted back in a single infusion.
Both drug approvals are grounded in studies evaluating the efficacy and safety of these innovative therapies in clinical patients. Participants in the Casgevy study reported the absence of “severe VOCs” for at least 12 consecutive months during the 24-month follow-up. Similarly, Lyfgenia patients did not experience a “pain crisis” for six to 18 months post-therapy.
The FDA’s decision closely follows approvals from UK regulators and Bahrain’s National Health Regulatory Authority for Vertex’s Casgevy. The approval of a CRISPR-based treatment not only signifies a major advancement in sickle cell disease treatment but also opens the door to further innovation in the gene editing realm. Nicole Verdun, the director of the Office of Therapeutic Products at the FDA’s Center for Biologics Evaluation and Research, emphasized the promise of gene therapy in delivering more targeted and effective treatments, particularly for individuals with rare diseases where current options are limited. Casgevy is currently under review by the European Medicines Agency.
