What is a clinical trial?
Once a candidate drug has been tested and characterized in preclinical studies and appears to be safe, it has to be tested in humans and therefore enters the clinical phase of development. Initial clinical studies are usually performed in healthy volunteers (Phase I clinical trials). Then proof-of-concept studies in patients are conducted to provide the first evidence of the efficacy of the drug in development (Phase II clinical trials). Then large scale clinical trials are performed to confirm the efficacy and safety data in patients (Phase III clinical trials). At all stages of the clinical development, the assessment criteria for the new drug include safety, tolerability, efficacy, pharmacokinetics and patient acceptability. The different phases are described in the picture below.
