And frankly, it's easier than having to purify the protein from another source, figure out injection conditions/strengths, etc
I see where you're going, but you don't avoid a lot of that work with gene therapy. You still need to produce and the test the virus, and then scale up product along with all the purification needed. The FDA will also ask you to test various doses to provide you're giving the right amount need for the desired efficacy.
In addition, gene therapy requires additional tests to prove that the inserted genes don't end up in some weird place that causes even more issues. Not a huge cost driver, but a concern that small molecules don't have (admitting they still need carcinogenicity testing).
I see where you're going, but you don't avoid a lot of that work with gene therapy. You still need to produce and the test the virus, and then scale up product along with all the purification needed. The FDA will also ask you to test various doses to provide you're giving the right amount need for the desired efficacy.
In addition, gene therapy requires additional tests to prove that the inserted genes don't end up in some weird place that causes even more issues. Not a huge cost driver, but a concern that small molecules don't have (admitting they still need carcinogenicity testing).