The research and development of pharmaceutical products up to the point of approval is carried out in three phases: the pre-clinical research, the clinical research and the marketing authorization. In the preclinical research the composition and stability of the active ingredient is first tested in the laboratory, followed by experiments in the animal model in which the drug is tested for effectiveness and to see whether it may be poisonous (toxicity).
 
Clinical studies are divided into four phases. In Phase I the active ingredient is generally tested in healthy volunteers (subjects), in order to determine how it acts inside the body; various dosages are examined. For cancer drugs, these studies may already be carried out on those suffering from the disease.
 
In Phase II a limited group of patients receives the drug in order to determine whether it is effective and well-tolerated. Possible side effects are to be identified, and efforts are made to find a suitable dose. This phase may extend over two, three or more studies.
 
Phase III studies are randomized, controlled and prospective studies that are blinded to both doctors and patients. One group of the patients receive the new drug, the other is treated with an existing therapy or receives placebos or a comparable drug. At the end, the results are compared.
 
Once Phase III has been successfully concluded, authorization is generally given. Subsequently, Phase IV studies are added in order to gather additional information on safety and effectiveness.