Just a few weeks after a promising gene therapy for sickle cell disease seemed to have hit a roadblock, prospects for the treatment now look better. Preliminary data suggesting that it might cause cancer have not held up.

In the gene therapy, scientists insert a normal gene into patients’ DNA to help correct sickle cell disease, which is caused by a devastating mutation. The cutting-edge treatment may prove to be a cure, and a company that is testing the treatment, Bluebird Bio, had been on track to apply to the Food and Drug Administration for approval next year.