Regulatory density as a means to refine current regulatory approaches for increasingly complex medicines.

The continuous scientific, societal, and technological advancements have shifted drug development toward increasingly complex and ever more targeted treatments. This creates new and unprecedented challenges for global regulatory systems. To address the increased risks and uncertainties of increasingly complex medicine, we advocate for a more tailored and flexible regulatory approach, which is explained here with the concept of 'regulatory density'. In the context of this paper, 'regulatory density' describes the relative amount of obligatory standards, measures and procedures applied to certain medicinal products or product classes and the resources required to meet these requirements. Given that risk and uncertainty are dynamic variables that can change over time, with this paper, we want to stimulate (re)thinking of regulatory approaches for managing the challenges of future complex medicines.