After 44 days at the Children’s National Hospital in Washington, D.C., Kendric Cromer has left the hospital free of sickle cell disease. Cromer is the first patient to undergo a recently approved gene therapy for this disease.
Sickle cell disease (SCD) is caused by a genetic mutation in hemoglobin and affects roughly 100,000 people in the United States. In people with SCD, the red blood cells, which are typically round and flexible, become crescent-shaped or “sickled.” This is due to abnormal hemoglobin from the genetic mutation. The change in hemoglobin’s shape results in red blood cells becoming rigid and sticky, causing them to clump together and block blood flow to small blood vessels. People with sickle cell disease often experience a variety of symptoms and complications, including anemia, fatigue, swelling in their hands and feet, frequent infections, and delayed growth. Additionally, SCD can lead to serious health complications such as a stroke or organ damage.
Until December of 2023, there was no viable way for people with sickle cell disease to get treatment. That month, the US Food and Drug Administration (FDA) approved two gene therapies: a $3.1 million treatment developed by Bluebird Bio and a $2.2 million therapy from Vertex Pharmaceuticals.
Kendric Cromer, 12, was diagnosed with the disease as a newborn. Over the years, his crises have caused numerous trips to the emergency room and long-term hospital stays. Until now, Cromer was unable to participate in team sports or other common activities without major consequences.
Kendric was part of a medical trial to find a cure for the disease when the FDA approved commercial gene therapies. The treatment’s goal was to genetically modify Kendric’s stem cells, which would cause them to produce normal red blood cells. The reprogrammed, healthy cells would help decrease the number of sickle cells, ending his hospital trips and allowing him to lead a more normal life. Dr. Andrew Campbell, director of the Sickle Cell program at Children’s National Hospital and Kendric’s doctor, explained that Kendric was picked due to his lengthy history of hospital visits during crisis and because eligible patients must be 12 or older.
“It’s a game changer,” Campbell said of the therapy. “They don’t have to take medications anymore because they’re walking around, allowing the stem cell to do the job for them.”
The first phase of Kendric’s treatment was to remove his bone marrow stem cells, where they were then sent to a Bluebird Bio lab for genetic modification. They were returned to his body within three months. For the treatment, doctors needed hundreds of millions of stem cells. One extraction of stem cells generally takes six to eight hours.
“The patient then gets some chemotherapy and that allows the bone marrow to kind of be wiped out and expand to accept the modified stem cells that have the gene therapy,” Campbell said. The process is both painful and costly, but luckily, Kendric’s insurance is covering the costs.
On September 3, Kendric was admitted to the Hospital for this final stage. He underwent intense chemotherapy to clear his bone marrow, allowing the new, modified cells to take over. On September 11, doctors reinfused the modified cells into his body. Of course, the therapy was not easy. Cromer began experiencing symptoms such as mucositis, a painful inflammation that causes sores in the mouth and intestines. His tongue swelled, leaving him unable to speak, and the pain spread to his stomach. Gradually, over the 44-day period, his swelling reduced. Due to the constant blood transfusions, Kendric has to undergo regular bloodletting in order to reduce the amount of iron in his body to prevent organ damage. The chemotherapy also left his immune system weak, requiring Cromer to get re-vaccinated with childhood vaccinations and avoid crowds while he recovers.
Bluebird Bio has estimated that it can only treat between 85 to 105 patients per year. Children’s National Hospital stated that it can only treat 10 patients. Even still, families are lining up for the potential of being sickle cell free.
Deb Cromer, Kendric’s mom, noted, “To see the light at the end of the tunnel and know that our child is the first to experience it outside of research – to know that it’s safe and the doctors here believe in it. I would go to the end of the earth to make sure he was cured. There’s nothing I wouldn’t do for my son, but this makes me proud.”
Kendric has recovered well but will continue to be monitored post-gene therapy.
Photo courtesy of The New York Times
