Phase I, II and III Trials in Inflammatory Bowel Diseases: A Practical Guide for the Non-specialist

In the last few decades several new molecules have been developed in the field of inflammatory bowel diseases. However, the process that leads to the approval and use of a new drug is very long, expensive and complex, consisting of various phases. There is a pre-clinical phase that is performed on animals and a clinical phase that is directed to humans. Each research phase aims to evaluate different aspects of the drug and involves a specific target group of subjects. In addition, many aspects must be considered in the evaluation of a clinical trial: randomization, presence of a control group, blind design, type of data analysis performed, and patient stratification. The objective of this review is to provide an overview of the clinical trial phases of a new drug in order to better understand and interpret their results.