Promising gene therapy for sickle cell disease seems to be blocking the road a few weeks later, and treatment prospects are now better. Preliminary data suggesting that it may cause cancer have not been preserved.
In gene therapy, scientists insert a normal gene into a patient’s DNA to help correct sickle cell disease caused by a destructive mutation. Primary treatment may prove to be a cure և The treatment testing company, Bluebird Bio, was on track to apply to the Food and Drug Administration next year for approval.
But on February 16, Bluebird Bio announced that a myeloid patient treated in clinical trials five years ago had developed acute myeloid leukemia. Another patient developed acute myelodysplastic syndrome, a type of cancer that often precedes leukemia.
The company stopped testing sickle cell patients with another blood disorder, beta thalassemia, while its researchers were trying to figure out if gene therapy was to blame.
On Wednesday, Bluebird Bio said it had found no evidence that gene therapy was causing sickle cell leukemia.
According to the company, the gene inserted into the patient’s DNA did not disrupt the activity of other genes. And the gene was not implanted in anyone in the genome known as leukemia.
Bluebird Bio is still investigating whether its treatment could be linked to acute myelodysplastic syndrome, but officials have asked the Food and Drug Administration to allow it to continue its clinical trials.
A separate mangosteen trial at Boston Children’s Hospital was also adjourned when Bluebird Bio announced two cancers at the request of the National Institutes of Health, which is paying for the trial.
Dr David Williams, a Boston Children hematologist and lead investigator at the trial, said researchers were allowing the NIH to allow them to resume work.
Like the Bluebird Bio investigators, Dr. Williams և and his colleagues use a disabled lintivirus to transmit cranial cells to patients. Lentiviruses are supposed to be safe. Hundreds of patients in other gene therapy trials have been treated with them, and no blood cancer has been reported. The possibility that Lens viruses may not be safe was a matter of great concern.
In a Bluebird Bio test, a patient with leukemia had genetic abnormalities associated with leukemia, which may explain why it developed.
Philip Gregory, the company’s chief scientific officer, said it was unclear whether the patient diagnosed with myelodysplastic syndrome actually had it. So far, Bluebird Bio has not been able to find any bone marrow cancer cells.
“She may have been diagnosed early,” said Dr. Gregory. If cancer cells are found in a patient’s bone, Dr. Gregory added, the company will continue the same detailed molecular analysis that it did for a leukemia patient.
Dr. John von Tisdale, director of the Cellular-Molecular Therapeutic Unit at the National Heart, Lung, and Blood Institute, was cautiously optimistic.
“This data is really far from vector as a reason,” he wrote in the e-mail. But, he added, researchers still need to better understand the illnesses of the test participants before they can breathe final relief.