In the late 1950s, a drug called thalidomide was widely prescribed in Europe and Australia as a highly effective treatment for morning sickness in pregnant women. The manufacturer assured doctors that the drug was completely safe. However, thalidomide is a chiral molecule, meaning it exists in two mirror-image forms. While one form successfully cured nausea, the other was highly teratogenic. The drug crossed the placental barrier and interfered with the development of fetal blood vessels, leading to a global catastrophe. Over 10,000 babies around the world were born with severe limb deformities, often missing their arms and legs entirely. The United States largely avoided this tragedy thanks to an FDA inspector named Frances Kelsey, who famously stonewalled the drug's approval by demanding more safety data, despite facing massive pressure from the manufacturer. This averted disaster directly resulted in the passage of the 1962 Kefauver-Harris Amendment, which fundamentally defined the modern regulatory framework for the FDA. Prior to this amendment, the regulatory bar was essentially just proving that a drug wouldn't acutely kill people (kind of like the current bar for most recreational peptides). The 1962 amendment introduced a much higher standard: pharmaceutical companies were now legally required to conduct controlled clinical trials to prove that their drugs were not only safe, but also actively effective for their intended use. The gap between the old standard and this new requirement was massive. In fact, roughly two-thirds of the drugs that had previously passed the 1938 safety requirements ended up failing the new 1962 efficacy bar. This historical context is often cited by public health experts today when defending the FDA's grueling, multi-phase clinical trial requirements against critics who argue for faster drug approvals or unregulated access to experimental compounds.