Without animal testing, drugs trials would go straight from testing on cells to testing on humans.
Would you really want to be given a drug that had only been tested on some practically inert skin
cells?
Unfortunately, this does happen, drug test on animals that fail, for what the drug industry has tested, are quietly put away. Tests that show positive for the drug are shown to the FDA and people are allowed to take them. This is why diet pills that cause cancer come out and other drugs with horrible side affects come and go on the market. This doesn't even count, people being prescribed 10 or 15 drugs at a time, that no doctor on earth can tell you what the interactions may cause.