Just a few weeks after a promising gene therapy for sickle cell disease, it seemed that there was an outcry on the road, the treatment possibilities now looked better. Preliminary data suggests that it may not be the cause of cancer.
In gene therapy, scientists insert a common gene into patients’ DNA to help cure sickle cell disease, which is caused by a devastating mutation. State-of-the-art treatment may prove to be a cure, and a company that is testing the treatment, Bluebird Bio, was on track to apply to the Food and Drug Administration for approval next year.
But on 16 February, Bluebird Bio announced that a sickle cell patient had undergone a clinical trial five years earlier. Had developed acute myeloid leukemia. Another patient received acute myeloadsplastic syndrome, a form of cancer that is often a precursor to leukemia.
The company discontinued its tests for sickle cell patients and another blood disorder, beta thalassemia, while its researchers tried to understand if there was a mistake in gene therapy.
On Wednesday, Bluebird Bio reported that it had not found evidence that gene therapy caused the sickle cell patient’s leukemia.
The gene inserted into the patient’s DNA does not disrupt the functioning of other genes, the company said. And the gene was not inserted near any other in the genome involved in leukemia.
Bluebird Bio is still investigating whether its treatment may be associated with acute myeloidesplastic syndrome, but officials have asked the Food and Drug Administration to allow it to continue its clinical trials.
A separate sickle cell test at Boston Children’s Hospital also ceased when Bluebird Bio announced two cancers at the request of the National Institutes of Health, which is paying for the test.
Dr. The researchers are seeking permission from the NIH to resume their work, said David Williams, a hematologist at Boston Children’s and a lead investigator of the trial.
Like Bluebird Bio’s investigators, Drs. Williams and his colleagues are using an incompetent lentavirus to distribute a gene to sickle cell patients. Lentiviruses are considered safe – hundreds of patients have been treated with them in other gene therapy trials, and no blood cancer was reported. The possibility that lentiviruses may not be safe was a matter of serious concern.
In the Bluebird Bio trial, a leukemia patient adopted genetic abnormalities associated with leukemia, which may explain why it developed.
The company’s chief scientific officer Philip Gregory said it was not yet clear whether the patient had myeloidoplastic syndrome. Until now, Bluebird Bio has not been able to find any cancer cells in its bone marrow.
“He may have been diagnosed prematurely,” Dr. Gregory said. If cancer cells are found in the patient’s marrow, Drs. The company will move forward with the same detailed molecular analysis that it did for the leukemia patient, Gregory said.
The head of the cellular and molecular therapeutic branch at the National Heart, Lung, and Blood Institute, Drs. John Tisdale was cautiously optimistic.
“These data actually point as far away from the vector,” he wrote in an email. But, he said, researchers still have a better need to understand the diseases in trial participants before they can breathe a sigh of relief.