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red blood cells

Photo by Paweł Czerwiński on Unsplash

Gene therapy researchers are breathing easier after a company reported today that the modified virus it used to treat sickle cell disease in a person who later developed leukemia was very unlikely to have caused the cancer.

The leukemia case, which Bluebird Bio disclosed on 16 February, led the company to halt its two sickle cell disease trials and suspend sales of a similar treatment for beta-thalassemia. The following week, the U.S. Food and Drug Administration (FDA) put a hold on the company’s two sickle cell disease trials and two beta-thalassemia trials.

But the company has now done various lab tests and found “important evidence demonstrating that it is very unlikely our BB305 lentiviral vector played a role in this case,” said Chief Scientific Officer Philip Gregory in a press release. The company is now in discussions with FDA about lifting the trial hold.

The studies use a modified virus called a lentivirus to insert a curative gene into the chromosomes of patients’ blood stem cells. About 2 decades ago, a different... see more