Very interesting. Am I understanding this correctly: it's an insulin replacement? Those treated would have effectively no insulin in their blood stream?

If so, wouldn't those treated by this gene therapy still suffer a persistent hormone imbalance? Hormones are complicated. Insulin (and the lack thereof) is tied in up-down regulation of lots of other hormones. Glucagon, for one, would always be higher in your body meaning you'd be prone to break down your body's fat stores. While that might actually be a positive side effect, I wouldn't be surprised if there were many negative side effects too.

Still, the side effects from this hypothetical hormone imbalance is very likely a huge improvement over constantly having advanced glycation end-products slowly destroying your body (which is what slowly happens to us type 1 diabetics).