Clinically Important Effects in New Drug Development

In new drug development, demonstrating a clinically important effect of the new drug is a key element of efficacy evaluations instead of simply showing a statistical significance. However, approaches to demonstrate clinically important effects are unclear and not well recognized among many investigators and sponsors. The minimal clinically important change from baseline (MCIC) and minimal clinically important difference between groups (MCID) are used to assess the clinically important effect. We state the roles of MCIC and MCID in each phase of new drug development and common approaches to establishing MCIC and MCID. Furthermore, we provide some common approaches on how to practically compare the clinical trial results with the MCIC and MCID and interpret the clinical importance from applications in new drug development. We also suggest incorporating the clinical importance at the planning phase of trials.