Integrated Approach to Determine Equivalence in Complex Drug Mixtures

Heterogeneity and complexity of biopharmaceutical agents developed over the past decade or so can be defined at two levels. First, in the case of protein systems such as monoclonal antibodies, the primary source of heterogeneity arises from glycosylation post‐translational modifications mainly at the conserved N‐linked glycosylation sites in the constant (Fc) region of the heavy chain.

The Fc glycosylation plays a role in maintaining antibody stability and also contributes to binding with Fc gamma receptor isoforms that in turn mediate effector functions such as antibody dependent cellular cytotoxicity (ADCC). Second, in the case of complex drugs such as heparin or low molecular weight heparin (LMWH) etc. the main component of the drug is a heterogeneous mixture of linear (in the case of heparin) or branched glycan polymers with a molecular weight and anionic charge distribution. Developing follow‐on (or generic) versions of such complex biopharmaceutical mixtures is therefore in constant need for new technologies to define and characterize these mixtures as comprehensively as possible from the standpoint of chemical and biological equivalence. Despite these advances, there remain gaps in linking glycosylation heterogeneity with antibody efficacy and adverse effects such as those related to host immune response to a human antibody generated in a non‐human cell line.

In the case of complex glycan drugs such as heparin and LMWH, there is a larger gap in linking mixture properties with biological action of the drug. For example, despite the fact that heparin has been quality controlled and used in clinic for several decades, a serious global health crisis associated with administration of heparin emerged in early March 2008 which was later identified by us and others to be associated with an unnatural glycosaminoglycan contaminant species. We have extensive experience in characterizing complex biopharmaceutical mixtures in terms of their structural attributes and how these attributes impinge on their function.

A central component of our approach is the ability to employ a computational framework that we had built over the past decade or so in integrating diverse datasets pertaining to complex glycan mixtures. This framework permitted us to incorporate orthogonal datasets including analytical and functional data to get to the bottom of structure‐function relationships of complex glycan mixtures. In this proposal we seek to build on this computational platform and our extensive experience to build a robust set of integrated tools and algorithms to determine the extent of characterization required for establishing equivalence for therapeutics that are used in the clinic. Through the studies proposed here, we believe that we will make a contribution towards determining criteria for sufficiency in characterization of complex therapeutic agents in establishing equivalence.