No matter what vetting is done before hand, the first time it's used on a human is the equivalent to human testing. That's why we came up with animal testing in the first place - to try to make it the least damaging to humans as possible.

And they won't know all the possible issues until whatever they've created is used by a living being. Until then, it's an educated guess as to how anything effects living beings.

with chronic pain than to try to develop drugs that do the same thing marijuana does, but with the risk of serious or lethal side effects?

A huge, centuries (even millenia) long drug trial has already been done, and marijuana has been proven safer and more effective even than aspirin, and certainly more than prescription opioid pain relievers.

Someone once said that if aspirin were discovered today it would be recognized as a miracle drug. Probably it would by msny--but the government would either make it illegal and attach severe penalties to its use or would make it prescription only.

If mj were not so easily grown, and if it had not already been "discovered" by millions of ordinary people, it would probably be an expensive prescription drug and used for a lot of different conditions.

They have been focused on taking nature's plants and extracting the ingredient they think will make an effective drug.
Problem is, as has been shown with pot, natural plants have dozens of chemicals which interact with one another to produce the desired effect.

and it is widely expressed and regulated by estrogen. Sometimes I think they should just read the literature a little more carefully before designing these studies.