REVIEW

Integrated Strategies for Drug DiscoveryUsing Mass SpectrometryMike S. Lee, EditorWiley-InterscienceHoboken, NJ 07030, USAISBN 0-471-46127-XJune 2005, Hardcover, $115 U.S., 568 pp.

Reviewed by Ray BakhtiarMerck and Co.Rahway, NJ 07065, USA

This book is edited by Dr. Mike S. Lee, who is currentlythe President of Milestone Development Services. Ac-cording to the Preface, the book is based on a specialissue of Curr. Top. Med. Chem., which was published inJanuary 2002 (Volume 2, Number 1). The book consistsof 18 chapters written by respected colleagues in thefield and covers a compendium of useful topics with anemphasis on industrial applications of MS. Citations inmost chapters are relatively recent and the subjectindexing is adequate. There is something in this bookfor everyone interested in industrial applications ofbiological MS in drug discovery. This book will beparticularly beneficial to the new MS users (non-ex-perts), presenting them an introductory and easy-to-read, yet broad and not superficial, overview of thefield.

Chapter 1 discusses the low flow rate ESI for minia-turized applications in small and large molecule analy-sis. Brief discussions on static and on-line nanosprayapproaches, sample injection, mobile phase delivery,and MS interface are provided. Topics such asbottom-up and top-down protein analysis in localiza-tion of posttranslational modifications are mentioned.In this section, I would have liked to see a briefdiscussion on top-down fragmentation and an exampleof an ECD-FT-ICR-MS experiment from the authors’laboratory.

Chapter 2 gives a general survey of MS-based drugdiscovery screening assays with a focus on gas-phasenoncovalent analysis with examples on protein-drug,RNA-drug, and DNA-drug complexes. ESI-MS basedcondensed phase screening studies using frontal affin-ity chromatography, affinity centrifugal ultrafiltration,pulsed ultrafiltration, ultracentrifugation, gel perme-ation chromatography, and affinity CE are discussed.The chapter also describes the applications ofMALDI-MS using affinity probes, in conjunction withflow cytometry, and a brief reference to H/D exchangescreening of protein-ligand complexes using MALDI.The conclusion segment of this chapter outlines theadvantages and disadvantages (e.g., false positives dur-

Published online December 15, 2005

© 2005 American Society for Mass Spectrometry. Published by Elsevie1044-0305/06/$32.00doi:10.1016/j.jasms.2005.10.001(J Am Soc Mass Spectrom 2006, 17, 108–110)

ing screening) of using a MS-based approach for inves-tigation of specific noncovalent complexes.

Chapter 3 covers the applications of ESI-FT-ICR-MSusing multitarget affinity/specificity screening (MASS)for the analysis of RNA-drug noncovalent complexes.Small RNA sub-domains that mimic the active (func-tional) domain of ribosomal RNA are constructed andanalyzed using MASS in two fashions. Initially, high-throughput MS screening of naturally or syntheticcombinatorial libraries is performed to fish out thecompounds that bind to the target rRNA. Subsequently,the dissociation constants of the lead candidates aredetermined for SAR evaluations. This chapter containsa number of examples, clear descriptions on the exper-imental procedures, and their corresponding algo-rithms for data reporting.

Chapter 4 deals with the “emerging” topic ofproteomics-based biomarker discovery for disease di-agnosis. Recent advancements in genomics and pro-teomics have generated considerable interest in discov-ery and validation of biomarkers in the mechanism-based drug development. The main focus of thischapter is the utility of protein chip arrays in SELDI-TOF-MS, followed by several clinical examples usingthe PBS-II (low-resolution) and Qq-TOF mass spectrom-eters (high-resolution). Authors conclude the chapterwith advantages and pitfalls of the proteomics-basedbiomarker discovery. Issues such as specificity andsensitivity warrant additional improvement before theMS-based proteomic screening can be considered a“routine” tool in diagnostic medicine.

Chapter 5 is in some aspects complementary toChapter 4 and covers metabonomic applications intoxicity screening and disease diagnosis. The chapter isnicely organized and discusses the use of NMR andmagic-angle spinning (MAS) NMR spectroscopy inconjunction with principal components analysis (PCA)to characterize metabolic markers in urine and intact ratrenal papilla samples, respectively. Several multivariatemodels and their applications in data mining andinterpretation are discussed, with associated figuresand plots. Table 5.1 is particularly useful in capturingsome of the current metabolic markers associated withvarious toxins, identified via metabonomic analysis.

Chapter 6 describes the applications of MS in naturalproduct discovery and the complexity of biologicallyactive compound identification in complex mixtures.The utility of automated purification approaches suchas SepBox (HPLC/SPE/HPLC/SPE) in combinationwith MS-based screening are discussed. Authorspresent examples on data-dependent MSn, LC-MS/NMR, and high-resolution MS (e.g., Q-TOF and FT-ICR-MS), for structure elucidation.

Chapters 7 and 8 discuss, at length, the role of MS in

combinatorial chemistry. The two chapters complement

r Inc.

109J Am Soc Mass Spectrom 2006, 17, 108–110 REVIEW

each other and are well-written. Chapter 7 reviews anumber of topics such as library purification, flow-injection analysis MS, open-access MS, fast LC-MS,parallel runs (e.g., multiple columns, multiple spray-ers), SFC-MS, and CE-MS approaches. Chapter 7 couldhave been more educational to nonspecialists if it hadcontained some diagrams, figures, or tables to conveythe technical aspects of its theme. Chapter 8 describesthe construction of combinatorial library and mass-tagging techniques for encoding/decoding. To this end,a number of useful figures and diagrams on mass-encoding, “split-mix-recombine”, photo-cleavable link-ers, and the use of stable isotope for MS signatureconstruct are presented. Several pages at the end of thechapter are devoted to statistical decoding and datamining with relevant illustrations.

Chapter 9 covers the methodological advances indrug metabolism (ADME) studies. The authors presentan updated, clear overview of hardware and softwareapplications including LC-NMR, accelerated mass spec-trometry (AMS), microfluidic devices, and linear iontrap MS platforms. This chapter would have been evenbetter than its current form if it had contained figuresand/or tables on some of the techniques (i.e., fieldasymmetric-waveform ion-mobility spectrometry, SciexQtrap, LC-NMR, lab-on-a-chip) discussed therein.

Chapter 10 focuses on characterization of reactiveintermediates (this topic is of relevance in investigationof drug elicited toxicity) using a combination of site-specific chemical trapping (e.g., GSH, Lys-Phe, dansy-laziridine) in conjunction with LC-MS/MS at the earlystages of drug discovery screening (without the use ofradiolabeled compounds). Test cases using loxapine,diclofenac, quinidine, ticlopidine, and troglitazone arepresented with a number of educational figures (prod-uct ion spectra) and mechanistic schemes. Topics suchas acyl glucuronide (AG) reactivity/rearrangement,glutathione trapping, solution deuterium exchange ex-periments, and protein covalent binding are discussedin a succinct fashion. A number of product ion spectraare shown with their corresponding structural assign-ments.

Chapters 11 and 12 are well written with a number ofpractical discussions (kitchen tricks) on quantitativebioanalysis in drug discovery. In Chapter 11, the readeris methodically introduced to ionization schemes, massanalyzers, on-line sample analysis, off-line samplepreparation, fast gradient, monolithic columns, ioniza-tion suppression, metabolite interference, and cross-talk. The text is written well with more than 130citations and a number of illustrations and schematics.Chapter 12 is a continuation of a similar theme but witha focus on pharmacokinetic applications and typicalissues encountered during lead optimization. Ap-proaches such as cassette-accelerated rapid rat screen(CARRS) and dosing vehicle mediated ionization sup-pression are presented. I would have liked to see a littlemore depth and discussions on the latter subject matter

involving the “dosing vehicle” mediated ionization

suppression. This topic is becoming an important issue(i.e., based on several recent published reports), whichat times leads to dramatic masking effects on thepost-dose pharmacokinetics samples when using theso-called low k= LC-ESI-MS runs.

Chapter 13 contains LC-MS based strategies forpharmaceutical profiling purposes. A host of topicsincluding chemical stability, purity, and in vitro meta-bolic stability using LC-MS and LC/UV/MS with soft-ware illustrations are covered. The application ofLC-MS in studies using the parallel artificial membranepermeability assay (PAMPA) to possibly predict thepassive intestinal permeability is discussed. Metabolicstability studies using liver microsomal (rat, human,and mouse) assays in a 96-well plate format concludethis chapter.

High-throughput screening (HTS) studies specific tomedicinal chemistry needs are the focus of Chapter 14.Highly hyphenated techniques (e.g., LC/UV/MS/NMR, LC/UV/CLND/MS, SFC-MS) for sample char-acterization and impurity identification are discussedalong with two related tables that capture the pros andcons of each experiment. Examples, on the Symyxautomated workstation and supercritical fluid chroma-tography are presented for solubility (solubility pro-files, polymorph forms, and salt formulations) andpurification purposes, respectively. The chapter con-cludes with a brief reference to the newly introducednanostream microfluidic cartridge with 24 LC separa-tion channels.

Chapter 15 is another segment focusing on pharma-ceutical profiling, which contains informative tableswith an overall presentation on determination of mul-tivariate property at early and mid stages of drugdiscovery. This chapter is useful to the readers whowould prefer to become familiar with pharmaceuticalprofiling and hit optimization without going into in-strumental and other technical details. To this end,several informative tables summarize the applications,hurdles, and relevant assay attributes.

Chapter 16 deals with mass spectrometry applica-tions in organ perfusion studies (the vascularly per-fused intestine, liver, kidney, etc.). Clear and concisediscussions on the gut model (absorption into blood),liver (first pass clearance), kidney (renal clearance),lung (absorption from airways), and brain (uptake fromblood) are presented with relevant citations. Fortu-nately, the focus on the LC-MS platforms is confined toa minimum, to avoid redundancy and overlap withother chapters.

Chapter 17 complements Chapter 11 on sample prep-aration strategies including protein precipitation, liquid-liquid extraction, solid-phase extraction, restricted-accessmedia, and turbulent flow chromatography.

The book concludes with Chapter 18 on automa-tion, briefly covering a host of topics such as barcoding for sample tracking (DataMatrix), data acqui-sition, data archiving (with consideration to FDA’s

CFR Part 11), scripting robotics, LIMS, Microsoft.Net,

110J Am Soc Mass Spectrom 2006, 17, 108–110

and specific tasks performed using Visual Basic pro-gramming.

Overall, this textbook is easy-to-read, clearly orga-nized, and well written by established colleagues in thefield. In most cases, authors’ bias toward the subjectmatter was minimal. Therefore, throughout the book,pitfalls and advantages are brought to the reader’sattention. In retrospect, if space were not an issue, twomore chapters would have made this collection com-plete. One chapter could have dealt with the opera-

tional basics (without going into design and mathemat-

ical details) of linear ion traps, LTQ-FT-ICR-MS,Orbitrap, TOF-TOF, and any other relatively recentmass analyzer. The other chapter would have focusedon assay development and important issues in samplepreparation, mobile phase, column, and MS ionizationselection in chiral (enantiomeric) LC-MS in support ofdrug development. Nonetheless, I highly recommendthis book as a supplement in a graduate course onbioanalytical chemistry, in a Pharmacy/Pharmaceuticscurriculum, and for use by industrial scientists who are

“new” to the field.