Preclinical Testing

Laboratory and animal studies are performed to determine if the compound is active against the targeted disease. Preclinical tests offer the first look at the compound's safety. These tests take one to two years.

Investigational New Drug Application (IND)

Following preclinical testing, an IND is filed with the Food and Drug Administration (FDA) for permission to test the drug in people. The IND documents results of previous experiments, explains the chemical structure of the compound and how it works in the body, details any toxic effects seen in animal studies, and outlines how the compound is manufactured.

Clinical Trials, Phase I

Approximately 50 normal, healthy volunteers are administered the drug. The tests study the compound's safety profile, including the safe dosage range. The trials also determine how a drug is absorbed, distributed in the body, metabolized and excreted. The duration of its action is also measured. Normally, this phase takes nearly one year.

Clinical Trials, Phase II

The agent is tested in controlled studies of approximately 100 to 300 volunteer patients who suffer from the target disease. This is usually the first phase in which the drug's effectiveness is measured. On average, phase II takes approximately two years.

Clinical Trials, Phase III

Now the compound is tested in a relatively large population, usually involving 1,000 to 3,000 patients in clinics and hospitals. Physicians monitor patients closely to determine efficacy and identify adverse reactions. This stage can take as long as three years.

New Drug Application (NDA)

Following the successful completion of all three clinical trial phases, the company files an NDA with the FDA. The NDA contains all the scientific information that has been gathered. NDAs typically run 100,000 pages or more and takes an average of 19 months for the FDA to review.

Expedited Process

Under a plan implemented by the FDA early in 1989, clinical trial phases II and III can be combined to reduce the development process by two to three years. Expedited Process is limited to medicines that show sufficient promise in early testing for serious and life-threatening diseases, such as cancer and AIDS.


Once the FDA approves the NDA, the new medicine is made available for physicians to prescribe. The pharmaceutical company must continue to submit periodic reports to the FDA, including all recorded cases of adverse effects and quality-control measures. Sometimes, the FDA requires additional Phase IV studies to evaluate long-term effects or gather other data.

Note: Outside the U.S., timing may vary for each clinical phase described above. In addition, once approval (or registration) of a drug is obtained, many countries require the manufacturer to negotiate price with the government before marketing the product.

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