How the FDA Approves Drugs

The Food, Drug, and Cosmetic Act of 1938 required drugs to be shown safe before sale, and the Kefauver-Harris Amendments of 1962, passed after the sedative thalidomide caused thousands of birth defects abroad, required proof that they work. A company first tests a drug in the laboratory and in animals, then files an investigational new drug application to begin human trials: Phase 1 for safety in a small group, Phase 2 for dosing and early evidence of effect, and Phase 3 for confirmation in hundreds or thousands of patients. It then submits a new drug application, or a biologics license application for vaccines and other biologic products, which FDA scientists review, sometimes with advice from outside expert committees.

Under user fee agreements first authorized in 1992 and renewed every five years, companies pay fees and the FDA commits to review standard applications in about ten months and priority applications in about six. Faster routes include accelerated approval based on early signs of benefit, created in 1992, breakthrough therapy designation from 2012, and priority review vouchers, and in 2025 the agency added national priority vouchers promising reviews in one to two months. Generic drugs reach the market through abbreviated applications under the Hatch-Waxman Act of 1984 once patents and exclusivity periods expire, and biosimilars follow a similar route created in 2010. The FDA approves roughly 50 novel drugs a year.

Approval is not the end. Companies must report side effects, the FDA can require warnings or restricted distribution, and it can ask for withdrawal if risks outweigh benefits. In 2025 the agency lost many staff and most of its senior leaders, changed its approach to some vaccines, and promised faster reviews and more transparency, including publishing rejection letters. Supporters of faster approval say patients with serious illnesses cannot wait, while critics warn that speed and political pressure can let ineffective or unsafe products through, and the user fee law comes up for renewal by September 2027.