Health

FDA approves two gene therapies for sickle cell, bringing hope to thousands with the disease

By CNN

December 8, 2023 9:47 AM

Published December 8, 2023 7:15 AM

CNN

By Meg Tirrell, CNN

(CNN) — The US Food and Drug Administration approved two gene-based treatments for sickle cell disease Friday, including the first therapy that uses the gene-editing technique CRISPR, opening a new era of treatments for genetic conditions.

The medicines, called Casgevy and Lyfgenia, are potential cures for people with sickle cell, a debilitating and life-shortening inherited red blood cell disorder that disproportionately affects African Americans.

Casgevy is the CRISPR-based treatment, made by Vertex Pharmaceuticals and Crispr Therapeutics; Lyfgenia, made by bluebird bio, uses an older gene therapy approach. Both were cleared for people 12 and older with histories of vaso-occlusive crises, painful events caused by the disease.

“Sickle cell disease is a rare, debilitating and life-threatening blood disorder with significant unmet need,” said Dr. Nicole Verdun, director of the FDA’s Office of Therapeutic Products within its Center for Biologics Evaluation and Research. “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.”

Casgevy will cost $2.2 million for the one-time treatment, Vertex said in a regulatory filing, while Lyfgenia will cost $3.1 million, bluebird said in a news release.

A drug pricing analysis group, the Institute for Clinical and Economic Review, had suggested that a price of $1.35 million to $2.05 million for each therapy would have made them cost-effective and encouraged the companies to consider pricing the medicines at the lower end of that range to enable broader access.

For many in the sickle cell community, the approvals have been a long time coming. The disease afflicts about 100,000 people in the US, including an estimated 1 of every 365 Black babies born, according to the US Centers for Disease Control and Prevention, and has long been considered neglected by the pharmaceutical industry. About 20,000 people in the US are thought to have a severe enough form of the disease to potentially qualify for a treatment like this.

“To have sickle cell suddenly be the focus of this dramatic new approach to therapy development is, on the one hand, great, because hopefully it will undo some of that history of neglect and really give the sickle cell community the attention that is always needed,” Mayo Clinic bioethicist Megan Allyse said. She notes, however, that access to such a cutting-edge treatment, which now carries a price of more than $2 million, remains a major question.

The first ‘molecular disease’

The underpinnings of sickle cell have been understood for almost three-quarters of a century; in 1949, chemist Linus Pauling published a paper in the journal Science describing how the oxygen-carrying protein hemoglobin is different in people with sickle cell, declaring the malady the first “molecular disease.” That was four years before the famous double-helical structure of DNA was proposed.

“We’ve kind of been waiting for this ever since DNA was first discovered,” said Dr. Lewis Hsu, chief medical officer for the Sickle Cell Disease Association of America and a physician who treats kids with sickle cell. “It’s been a long, long time coming.”

Sickle cell is caused by a genetic mutation that leads red blood cells, which contain hemoglobin and ferry oxygen around the body, to be misshapen, like crescents or sickles. These misshapen cells can get stuck in vessels, causing organ damage and – a hallmark of sickle cell – horrible bouts of pain that can last days, called vaso-occlusive, or pain crises.

Johnny Lubin is one of the youngest people to have had the CRISPR treatment, as part of a clinical trial. Before he went through it, he recalls, he had one main concern.

“I was worrying that I might get, like, superpowers,” said Johnny, now 15, who lives in Trumbull, Connecticut, about 60 miles north of New York City.

Before he had the treatment, “it was kind of hard for me to do things like have fun and stuff, because I’d always have to be worried about if I’d have a pain crisis,” Johnny said. The pain “would mostly be in my lower back, and it would always be like a pounding pain. … It hurt a lot.”

Until now, the only hope for a cure for people with sickle cell was with a bone marrow, or stem cell, transplant. But Johnny, like more than 80% of patients with sickle cell, couldn’t find a donor that matched.

For the first 13 years of his life, Johnny was hospitalized every few months because of pain crises and other complications from the disease. His parents had to stock opioid pain medicines and always had a “go bag” with them in case they needed to go to the hospital on short notice.

But since October 2021, when Johnny received a one-time infusion of his own gene-edited cells, he hasn’t had another crisis.

“He’s been like a normal child,” said Johnny’s mother, Fabienne Desir. “It’s life-changing for us.”

A new tool for editing genes

CRISPR is a gene editing technique that enables scientists to make precise cuts in DNA. The first scientific paper about it was published in 2012, and its development – by Jennifer Doudna and Emmanuelle Charpentier – won the Nobel Prize in chemistry just eight years later.

For sickle cell, patients’ cells are removed from the body and CRISPR is used to make an edit that turns back on production of fetal hemoglobin, a form of the protein that babies make in the womb. Once the edited cells are returned, the fetal hemoglobin can make up for the mutated hemoglobin that causes sickle cell, explained Dr. Monica Bhatia, chief of pediatric stem cell transplantation at NewYork-Presbyterian/Columbia University Irving Medical Center, who helped run the trial Johnny participated in.

“Fetal hemoglobin, we know, has a higher oxygen-carrying capacity than adult hemoglobin or sickle hemoglobin,” Bhatia said.

Making fetal hemoglobin along with sickle hemoglobin renders a patient similar to someone with sickle cell trait, Bhatia explained; that’s when someone inherits one sickle cell gene and one normal gene, and they “do not have any of the complications of the disease,” she said. “It is more than good enough.”

Indeed, Dr. David Altshuler, chief scientific officer at drugmaker Vertex, pointed out that some people naturally have genetic mutations that keep fetal hemoglobin high, “and they don’t have symptoms, even if they have the disease.”

“So it was like a physiologic, demonstrated approach that would work if you could turn on fetal [hemoglobin],” he said.

Clinical trial results, including Johnny’s, bear that out. In data cited by the FDA ahead of an advisory committee meeting on the therapy in October, 29 of 30 patients reached the trial’s main goal: freedom from a pain crisis for at least 12 months after treatment. The longest time without a crisis was 45.5 months, almost four years, and researchers will continue to follow the patients.

The hope is that the effects could last their entire lives.

“We don’t have as much long-term data as we do for stem cell transplant,” Bhatia said. “But that would be the hope, is that this would be comparable to a transplant and it would be sustained.”

The second therapy approved on Friday, Lyfgenia, was expected to be approved a few weeks later. It involves an older technology, using a virus to deliver a healthy copy of the gene that produces adult hemoglobin to make up for the one producing the sickled form. It also involves removing the patient’s cells and then returning them. It’s shown similarly encouraging results.

“These both bring tremendous benefit to the patients,” bluebird CEO Andrew Obenshain said.

Multimillion-dollar price tags

Whether people will be able to afford and access these treatments, though, is a key question. In addition to the multimillion-dollar price tags of the treatments themselves, they require the infrastructure of large medical systems.

“I don’t know whether it will get covered and paid for,” Hsu said.

Bluebird said Friday that it’s in “advanced discussions” with the largest commercial health insurance providers in the US, as well as more than 15 Medicaid agencies, representing 80% of people with sickle cell in the country. The company noted that it has designed “outcomes-based” contract options for insurers that tie payment for the therapy to how well it works over time.

The drug will start to be available early next year, bluebird said.

Hsu noted another factor influencing how easily people will be able to access these new treatments is where they’re offered: typically at academic medical centers in larger cities.

“I’m in Illinois, and they’re basically concentrated in Chicago, which leaves the entire rest of the state kind of bare, and so people would have to travel a very long distance to be able to get to this,” he said. “And then some states, there just isn’t anything.”

And the treatments aren’t simple; they require a lot of additional care around them that adds to the cost. For the CRISPR treatment, patients typically stay in the hospital for about a month to prepare for the re-infusion of gene-edited cells, first going through what’s known as “conditioning”: several days of chemotherapy to wipe out their bone marrow, which makes blood cells and platelets, so they’re ready to receive the new cells. The bluebird gene-editing treatment requires the same chemotherapy conditioning.

After the infusion, “it takes a period of time for those cells to kind of take up residence in the bone marrow and grow,” Bhatia said.

That period around the infusion can be very difficult for patients and their families; Johnny’s mom described how Johnny’s “whole GI tract was inflamed; he couldn’t swallow. That was really painful. It was hard to watch.”

And that chemotherapy conditioning carries risks, including the possibility of infertility, Hsu noted. He pointed out there are methods of trying to preserve fertility before the treatment, but coverage for that can vary by state as well. And more than half of people with sickle cell in the US depend on Medicaid for their primary insurance, according to the advocacy organization Sick Cells.

The conditioning treatment also carries a potential risk of cancer; two patients in earlier stages of bluebird’s trial died after developing leukemia, which the company suggested was unlikely to be related to the gene therapy itself but potentially from the chemotherapy needed to prepare for it.

The FDA included its strongest warning, put in a black box on the drug’s label, about the potential risk of blood cancer with Lyfgenia, noting “patients receiving this product should have lifelong monitoring for these malignancies.”

The FDA didn’t include a similar warning for Casgevy. Regulators said Friday that was because Vertex hadn’t seen cases of cancer in its clinical trials.

Vertex’s Altshuler said his company is working on improving the conditioning process to make it gentler, to “create the opportunity for the new cells to go in without any other damage to the body,” although he noted that it’s still in the research phase.

Scientists also are vigilant about potential off-target effects of the CRISPR gene-editing approach – meaning DNA could be cut in an unintended place – and the FDA convened a full-day meeting in October to assess those risks. Many experts there expressed confidence that those risks were “relatively small.”

To Altshuler, the bigger deal in an approval of Casgevy is that there’s such an advancement for sickle cell disease, not that it’s the first CRISPR therapy.

“We’re not about a tool; we’re about the disease,” Altshuler said. “Once we found the way in, and now we’ve shown you can treat this disease very effectively if you can increase fetal [hemoglobin], we’re going to drive on that.”

The company is in the very early stages of researching how to achieve an increase in fetal hemoglobin using a pill, so patients wouldn’t need to go through the conditioning and gene editing process, Altshuler said.

He noted that it’s very early days but said that kind of approach could be the answer to the “very valid” question of “how are we going to help people around the world with this therapy?”

The majority of patients with sickle cell live in Africa and India, and bluebird’s Obenshain said the company doesn’t have plans to introduce “this version” of its gene therapy there, noting that it’s too expensive to manufacture.

“Basically, for every patient, we manufacture one drug lot,” Obenshain said.

For Johnny and his family, the effects of his treatment have been so transformative they now celebrate the day he got the infusion of gene-edited cells as his second birthday. He can go swimming – previously an activity guaranteed to trigger a pain crisis – without fear and spent all of last summer in the pool, his family says.

And although he didn’t gain the superpowers he worried about, he got something potentially even better: the chance to be a normal kid.

“I’m starting to teach him how to drive,” said Johnny’s dad, JR Lubin. “So we’re stepping into the regular worry of, you know, raising a teenager.”