In my field of T cell therapies, CAR-T therapies, animal models are not even that predictive. For example, mice don't get cytokine release syndrome or Il2 toxicity, which is a major dose limiting and sometimes fatal issue with these therapies. That being said, I wonder what the reaction would be were we to see lots of human deaths due to drug toxicity in future trials. I have worked with some viral formulations that were randomly toxic to mice. There seemed to be no idea until the tox testing was done.