HPLC for Pharmaceutical Scientists 2007 (Part 11)

Great efficiencies have been achieved in the drug discovery process as a result of technological advances in target identification, high-throughput screening, high-throughput organic synthesis, just-in-time in vitro ADME (absorption, distribution, metabolism, and excretion), and early pharmacokinetic screening of drug leads. These advances, spanning target selection all the way through to clinical candidate selection, have placed greater and greater demands on the analytical community to develop robust high-throughput methods. This review highlights the various roles of high-performance liquid chromatography/mass spectrometry (HPLC/MS) in drug discovery and how the field has evolved over the past several years since the introduction of myriad...
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HPLC for Pharmaceutical Scientists 2007 (Part 11)11THE EXPANDING ROLE OF HPLCIN DRUG DISCOVERYDaniel B. Kassel11.1 INTRODUCTIONGreat efficiencies have been achieved in the drug discovery process as a resultof technological advances in target identification, high-throughput screening,high-throughput organic synthesis, just-in-time in vitro ADME (absorption,distribution, metabolism, and excretion), and early pharmacokinetic screeningof drug leads. These advances, spanning target selection all the way throughto clinical candidate selection, have placed greater and greater demands onthe analytical community to develop robust high-throughput methods. Thisreview highlights the various roles of high-performance liquid chromatogra-phy/mass spectrometry (HPLC/MS) in drug discovery and how the field hasevolved over the past several years since the introduction of myriad high-throughput drug discovery technologies. Included are significant develop-ments in HPLC/MS to support target selection (proteomics), biologicalscreening and assay development, high-throughput compound analysisand characterization, UV- and mass-directed fractionation for unattended,automated compound purification, and high-throughput in vitro ADMEscreening. Focus within the pharmaceutical industry has been to increase the likeli-hood of successfully developing clinical candidates by optimizing the compo-nents of the discovery process (i.e., spanning target identification → chemicalHPLC for Pharmaceutical Scientists, Edited by Yuri Kazakevich and Rosario LoBruttoCopyright © 2007 by John Wiley & Sons, Inc. 535536 THE EXPANDING ROLE OF HPLC IN DRUG DISCOVERYdesign → synthesis → compound analysis and purification → registration →biological and ADME screening. By optimizing each step in the iterative dis-covery process, it is expected that the compound attrition rate will be reduceddramatically as compounds advance into preclinical development. Both HPLCand LC/MS enjoy important roles throughout the discovery process, as will behighlighted in detail in this review. Once considered primarily an enabling toolfor medicinal chemists, HPLC and LC/MS are now key technologies incorpo-rated at just about every stage of the drug discovery process. Drug discoveryprograms typically initiate, as follows. Assuming that the relevant therapeuticarea (e.g., oncology, metabolic diseases, inflammation, pain, CNS, etc.) has beenselected, the next step is to identify a biological target relevant to the disease.As will be discussed shortly, numerous technological advances in the fieldof analytical chemistry (e.g., nanocolumn HPLC/MS/MS) that have greatlyfacilitated protein/target identification have been made since the humangenome initiative was launched. Following on the heels of target selection isthe requirement to establish tools for “just-in-time” high-throughput screen-ing of compound repositories (so-called corporate collections) and syntheticlibraries as a means for identifying initial hits/actives. In combinationwith structure–activity relationship (SAR) data generated from these high-throughput screens, chemists incorporate knowledge of protein three-dimensional structures and utilize computational tools (i.e., in silico methodsthat measure diversity and “drug-likeness” as well two-dimensional and three-dimensional pharmacophore models [descriptors] that predict biological activ-ity) to support iterative compound design, synthesis, and biological testing.Once the hits or actives have been identified, the process of hit refinement andlead optimization is initiated. At this stage, a chemistry team is established andboth parallel synthesis and more traditional medicinal chemistry strategies areincorporated to rapidly converge on qualified leads (so-called hit-to-leadstage). HPLC and LC/MS play an extremely important role in the hit-to-leadstage of discovery, providing key enabling analysis and purification capabili-ties to the medicinal chemist. Furthermore, activities that were traditionallyrelegated to drug metabolism and pharmacokinetics departments withindevelopment organizations are now integrated into early discovery so as toprovide early measurements and predictions of in vivo properties. Again,LC/MS has played an extremely important role in enhancing the drug devel-opability of these hits and leads. All of these advances have helped to stream-line the discovery phase of pharmaceutical drug discovery and developmentand are presented within.11.2 APPLICATIONS OF HPLC/MS FOR PROTEINIDENTIFICATION AND CHARACTERIZATIONThe human genome initiative that took a stronghold on biotechnology com-panies in the early 1990s through the first few years of the twenty-first centuryAPPLICATIONS OF HPLC/MS 537spa ...