CRISPR Gene-Editing Patients Treated for Sickle Cell Disease Still Going Strong A Year Later

During the recently concluded American Society for Hematology (ASH) meeting, researchers reported the most recent results from the first patients treated for sickle cell anemia and beta-thalassemia. Ten patients received treatment using CRISPR gene-editing technology in the research study to make precise changes to their DNA. The treatment was so successful, with minimal side effects, that a year later, the patients are still doing well and continue to improve.

The treatment consists of doctors removing stem cells from the patients’ bone marrow and using CRISPR to edit a gene in the cells, activating fetal hemoglobin production. Fetuses produce this protein in the womb, but it usually shuts off shortly after birth. The scientists believe that the fetal hemoglobin counteracts the defective adult hemoglobin they were born with. The patients then undergo rigorous chemotherapy to destroy most of their current bone marrow to replace it with the gene-edited cells, billions of which are then infused into their bodies.

Bone marrow cell samples from patients six months, then one-year post-treatment, showed the gene-edited cells had continued the full year, an encouraging indication that the approach has permanently altered their DNA and could last a lifetime.

The sickle cell patients haven’t had any disease complications since getting the treatment, including any pain attacks or hospitalizations. One has even been able to step down off the powerful pain medications she’s needed the greater part of her life. Similarly, the beta-thalassemia patients have not required their regular blood transfusions previously needed to keep them alive. “This gives us great confidence that this can be a one-time therapy that can be a cure for life,” says Samarth Kulkarni, the CEO of CRISPR Therapeutics.

“It is opening the door for us to show that this therapy can not only be used in sickle cell and thalassemia but potentially can be used in other disorders,” says Dr. Haydar Frangoul of the Sarah Cannon Research Institute in Nashville and who is helping run the study

“I’m very excited to see these results,” said Jennifer Doudna of the University of California, Berkeley, who was one of the winners of the Nobel Prize this year for her role in CRISPR’s development. “Patients appear to be cured of their disease, which is simply remarkable.”

Another nine patients were also treated according to CRISPR Therapeutics in Cambridge, Massachusetts, and Vertex Pharmaceuticals in Boston, co-sponsors of the research. Those individuals, however, haven’t been followed long enough to post any results, officials report. But the results from the first ten patients “represent an important scientific and medical milestone,” says Dr. David Altshuler, Vertex’s chief scientific officer.

The researchers stress that they still have to follow patients for a lot longer to ensure the treatment is safe and that it continues to work. But they remain optimistic that it will.