I was actually referring to ASO, siRNA, and other direct oligonucleotide therapeutics. These are viable right now, safe and effective. Gene therapy is kind of "next in line" as it were, but as you implied still has some major kinks to be worked out. Though I believe it will be relatively figured out given time. I'm pretty excited to see what the next decade holds for the field at large.

That method generally stops being efficient as you get to the higher double digits, but you can stitch those double digit length pieces together after they've been synthesized using a different chemical process. That makes the manufacture of these 40Kmers or really any conceivable length possible - though certainly not practical or economical.

Manufactured oligonucleotide material is very expensive relative to small molecule or even antibody medicines. The industry is working to solve that, as it's a relatively newer type of medicine, but whoever can figure that out will dramatically open up treatments for rare disease and personalized medicine, as well as bringing the cost down for tons of quality of life treatments that exist and are great, but are cost prohibitive vs standard treatments that work but only ok, or have side effects that suck but aren't bad enough to justify a treatment that's 50x more expensive.