Biologics have to go through large, randomized clinical trials to ascertain whether they can be used in a new indication. This is not true for biosimilars. We are used to measuring differences, not sameness, and relying on clinical trials to demonstrate a significant improvement in outcomes. This approach is not suitable for measuring sameness. Once we’ve established sameness and safety in the most complicated disease population, then analytic studies are enough to allow approval in other indications. Paul Cornes Paul Cornes, MD from the University Hospital Bristol NHS Foundation Trust, Bristol, UK takes us through the journey of extrapolation for biosimilars.