  In recent years there have been a lot of interest to test for similarity
between biological drug products, commonly known as biologics. Biologics are
large and complex molecule drugs that are produced by living cells and hence
these are sensitive to the environmental changes. In addition, biologics
usually induce antibodies which raises the safety and efficacy issues. The
manufacturing process is also much more complicated and often costlier than the
small-molecule generic drugs. Because of these complexities and inherent
variability of the biologics, the testing paradigm of the traditional generic
drugs cannot be directly used to test for biosimilarity. Taking into account
some of these concerns we propose a functional distance based methodology that
takes into consideration the entire time course of the study and is based on a
class of flexible semi-parametric models. The empirical results show that the
proposed approach is more sensitive than the classical equivalence tests
approach which are usually based on arbitrarily chosen time point. Bootstrap
based methodologies are also presented for statistical inference.
