two quick points -
The farther up the chain of biological action/reaction you go, the more specific you get in your effect.
Proteins, which are pretty much exclusively the targets of 99.99% of the medicines out there, are way down the line, and tend to have multiple functions.
mRNA's, on the other hand, are doing just one job at a time, and we can target one mRNA at a time. Like say, the one that tells your cell to stop sending bits of viral protein to the surface so your immune system can't see the virus and kill it (that's the new one we're working on for herpes).
And the leukemia cases - that's gene therapy, and we don't do that. We don't actually mess with the genome and add or delete DNA sequences. What we do is interfere with a very specific cellular process AFTER the DNA transcribes an mRNA, and we do it transiently.
Look up post transcriptional gene silencing (PSGS) for a better understanding of a large part of our science. That will tell you basically how we're different from gene therapy.
Th