DNA, protein and nanotech type drugs are so hard to make that from discovery it often takes about 10 years to put them into production. We are at a point right now where we have figured out a way to make something in a lab but not how to make it at an industrial scale. If you lowered patents to 2 years for this stuff you would stop all work on it.
We have also just started using stuff like CRISPR-CAS to do DNA editing on humans. It is likely to take at least 10 years just to get something approved and that does not cover figure out how to actually make it at scale.
I used to think that drugs should have much shorter protections but since actually taking classes in how to make them, how to get them approved etc and how hard they are to make my views have changed. Sure the short molecule drugs that most traditional pharmaceuticals are may be almost trivially easy to make but the newer biotech types ones are HARD. I mean insanely mind mindbogglingly hard. Many of the protein based drugs start with a 10,000L vat and end up at the end with 4 kg of product. Overall to make that 4 kg takes many millions of dollars for each batch and it does not help many people. However if you ever want that technology to improve then the patents on it have to last long enough to justify what it takes to make it.