High-throughput pKa screening and prediction amenable for ADME profiling

Abstract

Recent technological advances have made it possible for several new pKa assays to be used in drug screening. In this review, a critical overview is provided of current new methodologies for high-throughput screening and prediction of pKa. Typical applications of using pKa constants and charge state for absorption, distribution, metabolism and excretion (ADME) profiling and quantitative structureactivity relationship modelling complements the methodological comparisons and discussions. The experimental methods discussed include high-throughput screening of pKa by multiplexed capillary with ultraviolet absorbance detection on a 96-capillary format instrument, capillary electrophoresis and mass spectrometry (CEMS) based on sample pooling, determination of pKa by pH gradient high-performance liquid chromatography, and measurement of pKa by a mixed-buffer liner pH gradient system. Comparisons of the different experimental assays are made with emphasis on the newly developed CEMS method. The current status and recent progress in computational approaches to pKa prediction are also discussed. In particular, the accuracy limits of simple fragment-based approaches as well as quantum mechanical methods are addressed. Examples of pKa prediction from in-house drug candidates as well as commercially available drug molecules are shown and an outline is provided for how drug discovery companies can integrate experiments with computational approaches for increased applications for ADME profiling.