Plasma Protein Binding Methods in Drug Discovery and Development: Bioanalysis

Abstract

AbstractThis chapter provides an overview of both conventional and unconventional methods to determine plasma protein binding. Experiments using plasma protein binding advance our understanding of ADME properties to aid in drug candidate selection and development by determination of the unbound drug blood concentrations as well as (potentially) drug concentration at the site of action. Recent progress in automation as well as increased routine performance of the analytical instrumentation has enabled a greater number of compounds to be assayed earlier in discovery, and often with high enough quality to obviate the need for repeat studies during development. Significant effort has been invested to search for high throughput screening methods that reliably and accurately determine protein binding in early drug discovery. The development of 96‐well formats for equilibrium dialysis, ultrafiltration and ultracentrifugation, combined with liquid handling automation have transformed a formerly tedious, labor‐intensive assay into a process that can now be swiftly conducted. In addition, new approaches, referred to as emerging techniques, are also under investigation including chromatographic methods such as the human serum albumin column, spectroscopic methods including surface plasma resonance, solid phase microextraction, Transil™ membrane screening, and capillary electrophoresis methods. Several challenges still remain unsolved, particularly in cases of high protein binding with low exposure levels that fall below the normal limit of quantitation. This chapter describes the impact of high (>99%), undeterminable protein binding on compound developability as well as possible solutions including plasma dilution techniques.