Investigational New Drug Application (IND)
- Filed after animal studies are completed
- Approval required before testing in humans can begin

Phase I
- Determine side effects and how drug is metabolized and excreted
- Normally 20-80 patients

Phase II
- Establish Drug's effectiveness in certain disease or condition
- Safety and short term side effects continue to be evaluated
- Greater number of patients studied, range anywhere from 25-300

Phase III
- More safety and efficacy data is gathered
- Dose ranging in different patient populations and interaction with other drugs
- Patients range from several hundred to 3000

Phase IV
- Post marketing study on long term effects and possible new indications
- How patients respond to different dosages