Phase 0 trials: expediting the development of chemoprevention agents.

Phase 0 trials are first-in-human clinical trials performed under the Exploratory IND [investigational new drug] Guidance of the U.S. Food and Drug Administration. Unlike traditional phase I trials, these studies have no therapeutic or diagnostic intent but instead aim to provide only pharmacokinetic and/or pharmacodynamic data to inform the next step in developing an agent. We discuss the role that such trials, including one reported by Reid and colleagues (beginning on page 347 in this issue of the journal), can play in expanding the number of drugs that are evaluated for chemoprevention while compressing the drug-development timeline.