I thought that gene therapy, when performed on target cells that regenerate themselves constantly, can be effective for a limited time only. I.e., the effect gradually wears off after a while, depending on how fast the target cells renew themselves. In other words, the patient needs to continue receiving gene therapy every so often to keep getting desired effect.
On the other hand, when targeting cells that do not divide/renew, such as an eye, gene therapy can and actually did cure blindness once and for all, and the patient no longer needs gene therapy injections.
So what about the other diseases that gene therapy allegedly cured? I think they include blood disorders like hemophilia and some serious immune system disorders? I thought they mainly involved cells that do regenerate, like bone marrow and liver?