One possibility is that the disabled virus used to deliver the gene therapy treatment damaged crucial DNA in blood-forming cells in the patients’ bone marrows. Busulfan is known to confer a blood cancer risk, Dr. Tisdale noted. The disabled lentivirus that Bluebird uses to deliver its gene therapy was designed with safety features. A lentivirus is also being used in a gene therapy trial for sickle cell disease at Boston Children’s Hospital. The first patient in Bluebird’s trial also developed myelodysplastic syndrome about three years after receiving gene therapy, Dr. Tisdale said.
Source: New York Times February 22, 2021 23:38 UTC