The gene editing technique CRISPR promises to treat all kinds of genetically-linked conditions, but it's so far limited to tweaking DNA, not the RNA that does everything from carrying protein sequence info to regulating gene expression. That may change soon, however. Scientists have discovered that a commonplace mouth bacterium (Leptotrichia shahii) can be programmed to break down whatever RNA you want. You could rip apart viruses, which are frequently based solely around RNA, or kill a cancer cell by denying it the chance to make vital proteins.
This isn't a cure-all right now. Researchers have to refine their approach before it works in humans, and it's hard to say whether or not this RNA editing will be as effective in practice. As you might surmise, though, the potential is huge. If this works as well as it suggests, you could fight a wider array of illnesses with gene editing, even those that are notoriously difficult to treat using conventional methods.