Potential Factors Influencing Regional Differences and Similarities in Multiregional Clinical Trials

In a multiregional clinical trial (MRCT), determining whether regional differences occur by chance or whether they are due to differences in pharmacokinetics, pharmacodynamics, or other prognostic factors is important to accurately evaluate the true efficacy of a drug in patients of each region. The general probability that regional results will differ from total results has been studied using statistical simulation. Consideration from the pharmacokinetic perspective is necessary as well to investigate the causes of regional differences. Patient characteristics may vary among regions, and differences in medical environment such as commonly used drugs and treatment guidelines can affect regional efficacy and safety results. Moreover, bias may be introduced in the data collected due to differences such as in diagnosis, assessment criteria, and reporting conditions. In this research, the factors and mechanism potentially influencing results by region in MRCT are examined, referring to the results of MRCTs already published.