Before a company can commence with clinical trial studies, they must first carry out thorough preclinical studies. These involve both in vitro tests as well as in vivo tests in animal species. The purpose of these studies is to determine how safe it is to proceed to trialling the drug on humans. It is thought that the data generated will provide adequate information on the safety and efficacy of the active substance.
Preclinical studies include Pharmacology (looking at pharmacokinetic and pharmacodynamic properties of a drug) and Toxicology studies. Only once a new drug molecule passes the pre-clinical phase can it enter the clinical trial phases. These studies aim to limit the risk to human patients.