Iirc it’s a copyright on either an improved process or an improved variation of the original manufactured insulin. I’ve heard some say that the “cheap stuff” doesn’t work as well as the expensive stuff. I haven’t looked into it very deep but iirc the super basic insulin, ie the one under the original open anti-patent is typically pretty cheap but it’s overall less effective or not as long lasting.

I’d love for a diabetic Comrade to step in and explain this better.