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FDA approves two gene therapy treatments for sickle cell disease

Avery Bleichfeld
FDA approves two gene therapy treatments for sickle cell disease
Vertex Pharmaceuticals in Boston developed Casgevy, one of the FDA-approved sickle cell disease treatments. PHOTO: VERTEX PHARMACEUTICALS

Two new gene therapies to treat sickle cell disease were approved by the U.S. Food and Drug Administration Dec. 8.

The treatments, both produced by Boston-area companies, join 32 other approved gene therapies and are approved to treat the disease in the United States.

Experts say the developments are a major move forward in treating the disease, which has an outsized impact on Black patients.

“This is a disease that we all know has been largely ignored, with huge challenges to access to equitable care. Now, really for the first time, there are approaches that are definitive one-time therapies,” said Dr. Bill Hobbs, vice president of clinical development for hematology at Vertex Pharmaceuticals in Boston, which developed Casgevy, one of the treatments. Casgevy is the first approved treatment in the United States to use CRISPR gene editing technology.

A spokesperson for bluebird bio, a Somerville-based pharmaceutical company, noted that sickle cell disease was the first disease to be examined on a molecular level. The company developed the other treatment, Lyfgenia, that was recently approved by the FDA.

“Sickle cell disease was … the first disease to have a known genetic cause, and that was nearly a century ago,” said Jess Rowlands, bluebird bio’s head of corporate communications. “To now have not just one, but two gene therapies come to this community where there’s been so little investment and not a lot of progress after nearly a century of waiting is really remarkable, and something we’re very proud to be part of.”

Jacqueline Haley, executive director of Massachusetts Sickle Cell Association, said the approvals were “really exciting news” for the sickle cell disease community.

The disease, which affects an estimated 100,000 Americans, predominantly impacts people of African descent. A 2023 study that considered patient database records from 2016 to 2018 found that of the nearly 75,000 people hospitalized for the disease, over 93% were Black. Just under 2% were white.

The two new treatments take different approaches to addressing the disease.

Bluebird bio’s Lyfgenia adds a working copy of the gene that creates the sickled red blood cells when mutated. The new, working copy produces healthy red blood cells and intervenes in the sickling process.

Vertex’s Casgevy treatment uses CRISPR-Cas9, a technique that can cut genes in specific spots to edit the genetic information. In the treatment, the CRISPR technology is used to reactivate fetal hemoglobin, which is produced by the body as a fetus is developing but is eventually shut off. Fetal hemoglobin is unaffected by the mutation that causes adult red blood cells to sickle.

Even as the approval of the two treatments represents exciting news for those struggling with sickle cell disease, questions and concerns remain around what’s next as they’re rolled out, Haley said.

The treatments, without insurance coverage, won’t come cheap. Casgevy will be available at a list price of $2.2 million; Lyfgenia is set at $3.1 million.

Those numbers don’t include the cost of a hospital stay, nor the chemotherapy treatments that are needed as part of the treatments.

Vertex’s Hobbs said he thinks that cost should be considered in relation to the cost patients have to pay to manage sickle cell disease throughout their life. He said beyond the impact on a patient’s day-to-day activities and quality of life, the lifetime cost of care for patients is $4 to $6 million, though other studies have put the estimate closer to $1.7 million.

“We think that there’s enormous value in a treatment like Casgevy, and … we’re excited to be working with insurers and physicians and institutions to be able to bring this to patients as quickly as possible,” Hobbs said.

The price may be especially prohibitive for families of color who not only are more likely to be impacted by the disease, but who often bear the brunt of wealth inequities.

“As we look at cost, will our families be priced out?” Haley said.

Both Hobbs and bluebird bio’s spokesperson said the companies are working with insurers as part of next steps as they roll the treatments out.

Haley also pointed to concerns around infertility, which can be a side effect of the treatment process for genetic therapies, which include chemotherapy to clear out bone marrow for a transplant of stem cells that were removed and edited.

Bone marrow stem cell transplants are already used to treat sickle cell disease, but, in the absence of gene therapies, require finding a close match in a donor.

During clinical trials, Hobbs said, Vertex offered patients fertility preservation in recognition of that issue.

According to a company statement, Vertex has also developed a program to offer support to commercially-insured patients. The federal government has not issued a favorable advisory opinion of the program, so it will not be offered to patients insured under Medicaid or Medicare.

The treatment will involve weeks spent in the hospital, but Dr. Jean-Antoine Ribeil, clinical director of the Center of Excellence in Sickle Cell Disease at Boston Medical Center, said he thinks the benefits of the treatments outweigh the challenges and side effects of the process.

“While these treatments are by no means simple or easy, they present our patients with the opportunity to drastically increase their quality of life and live without the chronic pain and worry from the disease,” he said in an email.

Boston Medical Center said in a press release Dec. 8 that they plan to offer both treatments to their patients. Ribeil said in an email that the plan is to start with a small group of eligible patients and build from there.

Casgevy’s use of CRISPR-Cas9 technology is also pushing boundaries as the first gene therapy approved by the FDA that uses CRISPR.

Ribeil called the approval, which comes only 10 years after the discovery of the technique was published, “groundbreaking for the scientific and medical community.”

Hobbs said the approval might open a door for other opportunities to treat rare diseases.

“I think what Casgevy has shown is that it actually works,” he said. “If you follow the biology and choose the appropriate specific target, in the right context, that you can have an outcome that does fundamentally alter the course of disease.”

Hobbs said he also sees broader promise in the first approval of a CRISPR treatment being used to treat a disease that predominantly affects Black patients.

“This is a turning point, that we are no longer going to be in the era where we ignore these diseases because the patient population isn’t a common one that we often think about or spend resources on,” Hobbs said. “The meaning of this one for the broader African American community is huge.”

bluebird bio, Casgevy, CRISPR, FDA, gene therapy, health, Sickle cell disease, Vertex Pharmaceuticals