FDA approves nation's 1st CRISPR gene therapy to treat sickle cell disease: Experts react

On Dec. 8, the FDA approved the nation's first medicine based on CRISPR gene-editing technology to be used as a treatment for patients with sickle cell disease, a major scientific advancement that opens the door for future gene therapy approvals for inherited disorders. 

The FDA approved exagamglogene autotemcel, or exa-cel, marketed as Casgevy, to treat sickle cell disease in patients 12 and older. The medicine is made by Vertex Pharmaceuticals and CRISPR Therapeutics. It's meant as a one-time therapy that works by using CRISPR technology to remove the disease-causing gene from a patient's stem cells. 

"As scientists, the fact that we have arrived at a potential curative treatment for sickle cell disease in a relatively brief period is a testament to the power of resolute researchers in this field who have never stopped," Eric Kmiec, PhD, founder and executive director of the Christiana Care Gene Editing Institute in Newark, Del., told Becker's. "For the first time, we have what appears to be a safe and curative treatment for one of the most painful diseases that cuts life short." 

A months-long process is required before a patient actually gets modified stem cells reinfused, experts told NBC News. The process starts with a series of blood transfusions over several months. From there, stem cells are extracted from a patient's bone marrow and sent off to a lab where they are edited. Physicians must then ensure no flawed stem cells remain, so patients undergo chemotherapy to destroy their bone marrow before the gene-edited stem cells are reinfused.  

About 100,000 Americans, the majority of whom are Black, are estimated to have sickle cell disease, an inherited blood disorder. Previously, the only known cure for the disease was a bone marrow transplant from a donor. Experts are not yet calling Casgevy a cure, given questions that remain about potential long-term effects.

The data is promising and Casgevy has shown to be effective, though its $2.2 million price tag may keep it out of reach for many patients, experts say. Forty-four patients in a clinical trial, including 30 who had at least 18 months of follow-up care. Of those, the treatment has been successful in 29 and met the primary efficacy outcome — freedom from severe pain and organ damage, known as vaso-occlusive crises. 

"I think I've been cautiously optimistic about this intervention," Sharl Azar, MD, medical director of the comprehensive sickle cell disease treatment center at Massachusetts General Hospital, told Becker's. "I [am] absolutely excited by this," but he added, "the next question immediately on my mind is, what is Medicare and Medicaid going to cover? Then we can sort of begin to set the criteria for how this falls into our algorithm of management overall." 

When considering the amount of money the healthcare system spends on the care for a single sickle cell patient annually, Casgevy's price does start to balance out, Dr. Azar said. However, the price doesn't include costs associated with the treatment, such as a hospitalization. 

"It is remarkable that finally we are focusing on the Black population first, who are most affected by his disease," Dr. Kmiec said. "This priority is long, long overdue," he said, echoing Dr. Azur's same concerns around pricing and access. 

"We must work with the healthcare industry and pharmaceutical companies who will market, produce and deliver the treatments to make sure that all people can get access" Dr. Kmiec said. "What can they do to make treatments more affordable and more available? What can they do to support continued research to assess the long-term effects this treatment may have? And how can we make this easier to deliver?"

Because administration of the therapy requires specialized experience in stem cell transplantation, only nine hospitals have so far been authorized to offer it, including Boston Medical Center and the University of Chicago/Comer Children's Hospital. 

The FDA on Dec. 8 also approved a second gene therapy for sickle cell disease from drugmaker Bluebird Bio. The cell-based gene therapy, Lyfgenia, was approved to treat patients aged 12 and older. 

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