Compounds that emerge from the process of drug discovery are called new chemical entities (NCEs). They will have some promising activity against a biological target, in a certain disease. However, little is known about the safety, toxicity, pharmacokinetics and metabolism of this compound in humans. Hence, these parameters will need to be assessed prior to human clinical trials. The dose and frequency of dosing will also need to be determined. The physicochemical properties of this new chemical entity (its chemical makeup, stability, solubility) will need to be established. Production on a large scale to different pharmaceutical formulations (known as chemistry, manufacturing and control [CMC]) will also need to be performed.

Many aspects of drug development are to satisfy regulatory requirements of drug licensing authorities to ensure safety. A number of tests need to be conducted to determine major organ toxicities of the new compound prior to its use in humans. Some tests can be performed using in vitro methods. However, many tests still require the use of experimental animals, to examine the complex interplay of metabolism and effects of exposure to toxicity.

Information obtained from the pre-clinical phase and CMC is submitted to regulatory authorities as an Investigational New Drug (IND) application. If the new drug is approved, development moves to the clinical phase assessing the efficacy and safety of the drug.

The process of drug development continues even in human clinical trials (Table 8.1). Long-term or chronic toxicities are determined, as well as its effects on fertility, reproduction and other systems, and its cancer causing effects if any. If the compound has an acceptable toxicity and safety profile, and the desired effect in clinical trials, it will be submitted for marketing approval. The drug then becomes ready for registration and distribution to pharmacies. However, most new compounds fail these tests. The success rate for a new chemical entity to successfully complete Phase I-III clinical trials to the point of registration is low.