High-Throughput Chromatographic Approaches to Assess Drug Partition into Biomembranes
Modern drug design and discovery not only focus on the pharmacological activity of a compound, but also take its pharmacokinetic behavior into account. The prediction of in vivo barrier permeation, particularly intestinal absorption and blood-brain barrier passage, are substantial concerns in the development of new drug compounds. For several decades, lipophilicity expressed as n-octanol/water partition coefficient (log Poct) dominated absorption prediction schemes, since partitioning in this solvent system is traditionally accepted as an informative model of membrane partitioning. Recent advances in automated synthesis and combinatorial chemistry result in a vast number of potential drug candidates, and thus the demand for fast and reliable methods to measure this parameter has grown rapidly in recent years. However, in many relevant cases especially for the structurally unrelated or ionized compounds, log Poct can not give a good estimate of a drug´s absorption or permeation. Indeed, the isotropic n-octanol/water system can only roughly mimic natural membrane barriers, which are made of ordered and anisotropic lipid membranes. Therefore bio-mimicking artificial membrane systems have been developed for a better prediction of drug absorption. The objective of this work is to further develop the present high-throughput techniques to measure relevant lipophilicity indices, and more importantly to understand the structural properties encoded in lipophilicity indices derived from different systems. This is important for designing better-suited drugs for medical therapy by improving the biopharmaceutical properties of the drugs via their chemical structure modifications. Chapter 1 gives a brief description of drug permeation and lipophilicity, and the relationship between them. Chapter 2 reviews the high-throughput chromatographic approaches to assess drug partition into biomembranes.