Drug development is the process of bringing a new pharmaceutical drug to the market once a lead compound has been identified through the process of drug discovery. It includes pre-clinical research (microorganisms/animals) and clinical trials (on humans) and may include the step of obtaining regulatory approval to market the drug. Clinical trials involves three or four steps: • Phase I trials, usually in healthy volunteers, determine safety and dosing. • Phase II trials are used to get an initial reading of efficacy and further explore safety in small numbers of sick patients. • Phase III trials are large, pivotal trials to determine safety and efficacy in sufficiently large numbers of patients. • (Phase 4): These are post-approval trials that are sometimes a condition attached by the FDA, also called post-market surveillance studies.