Original: However , in response to the Elixir Sulfanilamide disaster of 1937 in which the eponymous drug killed more than 100 users , the U.S. congress passed laws that required safety testing of drugs on animals before they could be marketed .
Simplified: Drugs did not have to be checked for safety . But in 1937 , a drug called Elixir Sulfanilamide killed more than 100 people .