Clinical trials are the cornerstone of the FDA approval process. They are conducted in multiple phases, each designed to answer specific questions about the drug's safety and efficacy, while involving increasing numbers of human participants.

Phase I trials typically involve a small group of healthy volunteers and focus on assessing safety, dosage, and potential side effects. If deemed safe, the drug progresses to Phase II trials, where its efficacy in treating the targeted condition is evaluated in a larger group of patients.

Phase III trials further confirm the drug's efficacy, monitor side effects, and compare it with existing treatments or placebos.