What is Phase 1

Phase 1 is the initial introduction of an experimental drug or therapy to humans. This phase is the first step in the clinical research process involved in testing new or experimental drugs. The Center for Drug Evaluation and Research, or CDER, a division of the U.S. Food and Drug Administration, oversees these clinical trials.


Phase 1 clinical studies or clinical trials are focused on the safety aspect of the new drug, rather than its efficacy in treating a disease. Phase 1 trials typically involve 20 to 100 people, a combination of healthy volunteers and patients or people with the condition. If the new drug is intended to treat a form of cancer, the research will involve patients with that type of cancer.

The main goal of Phase 1 studies is to establish the new drug’s side effects, as well as its metabolic and pharmacologic action. This is achieved by administering increasing doses of the experimental drug to trial participants. Researchers subsequently perform detailed research and analysis on various aspects of the drug, including the body’s response to it, method of absorption, how it is metabolized and excreted, and safe dosage levels.

Phase 1 and the clinical trial process

The Phase 1 clinical trial or study is the first phase in the long and grueling process of drug development. While the primary objective of Phase 1 studies is to establish the safety profile of the investigational drug, these studies also enable vital information about the drug’s effects and chemistry to be collated. This information can be used to facilitate the design of well-controlled and scientifically valid Phase II studies, the next step in the drug development process. 

Evidence of early effectiveness in Phase 1 trials, while a relative rarity, would be an added bonus and can result in significant price appreciation for the stock of the company developing the drug. In most cases, however, the effect of a successful Phase 1 trial on stock price is rather muted. This is because although approximately 70 percent of Phase 1 trials proceed to Phase 2, only 10 to 15 percent of Phase 1 drug candidates eventually make it to market. Phase 1 studies can be stopped by the CDER either at the outset or even after the trials have commenced, for safety reasons or because the sponsor failed to disclose certain risks of the drug candidate to investigators.

During Phase 1, researchers try to learn how effective the drug is in specific formats and determine the best dosages. This information is helpful to them in then formulating the trials for Phase 2.