The clinical trial process in the U.S. evaluates a drug candidate's safety and effectiveness. To begin a clinical trial, a company must submit an Investigational New Drug Application (IND) including all relevant preclinical testing results, to the FDA. The agency reviews the data, communicates its concerns or questions to the submitting company, and either allows the drug into Phase I testing or asks for further preclinical testing.

Phase I trials evaluate the safety and pharmacokinetics of a drug candidate in man. Depending on the drug's preclinical profile, the potential drug is administered to a sick patient population or healthy volunteers. The FDA evaluates this data and then may allow further clinical testing.

Phase II and Phase III clinical trials are designed to further corroborate safety data and determine how effective a drug is in a specific indication. The drug, or placebo, is given to a patient population for whom the drug is expected to be effective. The number of patients and time period of treatment varies for each drug in the clinical trial process. After the clinical trials are complete and results demonstrate that the drug is safe and efficacious, a New Drug Application (NDA) is usually submitted for FDA review.