What about the contrapositive... How many substances fail in mouse studies (and are discarded), yet would have been viable in humans? Any known examples of this?
Not sure if it applies though because it being severly harmful to rodents hasn't prevented us from looking into this substance closely. Quite the opposite.
from your wikipedia link
After an incident in 1951, where a US Army inductee unsuccessfully attempted suicide with multiple doses of warfarin in rodenticide and recovered fully after presenting to a hospital, and being treated with vitamin K (by then known as a specific antidote),[70] studies began in the use of warfarin as a therapeutic anticoagulant. It was found to be generally superior to dicoumarol, and in 1954 was approved for medical use in humans. An early recipient of warfarin was US president Dwight Eisenhower, who was prescribed the drug after having a heart attack in 1955.[70]
My understanding is that the only problem we have with antibiotics is that they breed antibiotic resistant diseases; but that is not really worse than us not having antibiotics at all.
But it's also worth remembering that the trope in fiction of $REALLY_GOOD_THING turning out to be $BAD_THING in disguise is just that, dramatically convenient fiction. There's no natural "game balance" to the universe. Yet popular entertainment is very small-c conservative about human improvement; if vaccines were still the stuff of fiction rather than daily life, a TV drama would show that universal prevention of smallpox has some terrible side effect that turns out to be worse than just letting people get infected and die. Fortunately we know that to be false but it won't stop dramatists and those shaped by them for immediately looking at newer biomedical advances with the most crushing cynicism.
(Not really directed at you, since I take it you're joking a bit, but this was the comment that prompted my thoughts...)