I don’t have the best answer for you, but there are a number of considerations apart from the synthesis of the active molecule itself. Delivery vehicle can alter the physiological impact of the active substantially, and so the overall “package” needs to be tested even though the active is already approved.
To my knowledge, generic trials aren’t as involved as their non-generic counterparts for obvious reasons. But they are still non-trivial logistical undertakings.
That makes sense! This is where I feel like I have a disconnect between what I think applied science is and what it looks like in practice. It seems like they should know enough about the molecule, delivery vehicle, etc, to know that it will work the same. A medical "proof" if you will. I guess we're not quite there yet? Is there work pushing in this direction?
To my knowledge, generic trials aren’t as involved as their non-generic counterparts for obvious reasons. But they are still non-trivial logistical undertakings.