[aptidude187]

Total noob here, is this type of treatment going in the direction of something like in the movie gattaca? Would gene editing also help fully grown adults?

[apathy]

If they have an identifiable deficiency, sure. Sickle cell is a stem cell (erythroblast more precisely) disorder, so fixing the stem cells fixes the disease. If you already have the tissues you want to change, it'll be harder.

[red75prime]

Real life gattaca would be quite boring. Protagonist would have failed practical aptitude tests or some such.

[true_religion]

He cheated. He had a heart condition but faked his heart rate for the testing so he would be allowed to go into space.

Yes, he could run at the same pace as someone with a better heart, but he was predisposed to arrhythmias even at a normal level of effort.