Lately there have been some interesting reports on the success of several gene therapies on trial.

Scientists using gene therapy have managed to turn normal pancreatic cells into insulin-producing cells in mice. If this works for human, we could be looking at a possible cure for diabetes mellitus in the near future. See full story here.

Gene therapy has also been shown to be able to restore hearing in mice, giving new hope for the reversal of hearing loss. (More details here)

It is also potentially possible to restore sight as well, according to this report.