We didn't expect the rate of oncogenesis from off-target gene insertion. It's bad news. At the same time, this is a treatment for a terrible, terrible disease

We didn't expect the rate of oncogenesis from off-target gene insertion. It's bad news. At the same time, this is a treatment for a terrible, terrible disease; so far the consequences seem smaller than what cerebral adrenoleukodystrophy would deal out on its own. So it's bad news about something which is probably still a good therapy (but we sure would like a better one).