Description
Book SynopsisDrug Bioavailability In order to reach its intended site of action, the drug molecules in every pill that we swallow must first be absorbed, transported via the bloodstream and evade various mechanisms that eliminate drugs from the body. Those drug properties that determine, for example, its stability in the gut or its ease of uptake into the bloodstream, are therefore of central importance in drug development. In fact, many potentially useful drugs fail because of insufficient availability at the biological target site.
This second edition of the gold standard for industrial research is thoroughly revised in line with current trends in the field, with all contributions extensively updated or rewritten. No other publication offers the same level of treatment on this crucial topic.
In 22 chapters readers can benefit from the key working knowledge of today’s leading pharmaceutical companies, including Pfizer, AstraZeneca, and Roche. Drug developers from industry and academia present all the factors governing drug bioavailability, complete with practical examples and real-life data.
Part I focuses on solubility and gastrointestinal absorption, while the second discusses in vitro and in vivo measurements of physicochemical properties, such as membrane permeability and solubility. Part III is devoted to metabolism and excretory mechanisms. The much revised and expanded Part IV surveys current in silico approaches to predict drug properties needed to estimate the bioavailability of any new drug candidate. The final part shows new drug development approaches as well as delivery strategies.
Indispensable for all those working in the pharmaceutical industry, pharmaceutical and medicinal chemists, and toxicologists.
Trade Review"The book covers a wide range of topics and, as such, it will serve as a valuable reference for pharmaceutical scientists, toxicologists, academicians, and the graduate students." (
Doody's, May 2009)
Table of ContentsList of Contributors XIX
Preface XXIII
A Personal Foreword XXV
1 Introduction: The Why and How of Drug Bioavailability Research 1
Han van de Waterbeemd and Bernard Testa
1.1 Defining Bioavailability 1
1.1.1 The Biological Context 1
1.1.2 A Pharmacokinetic Overview 3
1.1.3 Specific Issues 3
1.2 Presentation and Layout of the Book 4
References 6
Part One Physicochemical Aspects of Drug Dissolution and Solubility 7
2 Aqueous Solubility in Drug Discovery Chemistry, DMPK, and Biological Assays 9
Nicola Colclough, Linette Ruston, and Kin Tam
2.1 Introduction 10
2.1.1 Definition of Aqueous Solubility 11
2.1.2 Aqueous Solubility in Different Phases of Drug Discovery 12
2.2 Aqueous Solubility in Hit Identification 12
2.2.1 Aqueous Solubility from DMSO Solutions 13
2.2.1.1 Turbidimetric Methods 14
2.2.1.2 UV Absorption Methods 15
2.2.1.3 Alternative Detection Methodology 17
2.2.1.4 Application of DMSO-Based Solubility Assays 18
2.3 Aqueous Solubility in Lead Identification and Lead Optimization 18
2.3.1 Dried-Down Solution Methods 20
2.3.2 Solubility from Solid 21
2.3.3 Thermodynamic Solubility Assays with Solid-State Characterization 22
2.3.4 Solubility by Potentiometry 24
2.3.5 Application of Thermodynamic Solubility Data in LI and LO 26
2.4 Conclusions 28
References 28
3 Gastrointestinal Dissolution and Absorption of Class II Drugs 33
Arik S. Dahan and Gordon L. Amidon
3.1 Introduction 33
3.2 Drug Absorption and the BCS 34
3.3 Class II Drugs 36
3.4 GI Physiological Variables Affecting Class II Drug Dissolution 38
3.4.1 Bile Salts 38
3.4.2 GI pH 39
3.4.3 GI Transit 39
3.4.4 Drug Particle Size 40
3.4.5 Volume Available for Dissolution 41
3.5 In Vitro Dissolution Tests for Class II Drugs 41
3.5.1 Biorelevant Media 41
3.5.2 Dynamic Lipolysis Model 42
3.6 BCS-Based FDA Guidelines: Implications for Class II Drugs 43
3.6.1 Potential of Redefining BCS Solubility Class Boundary 43
3.6.2 Biowaiver Extension Potential for Class II Drugs 44
3.7 Conclusions 45
References 45
4 In Silico Prediction of Solubility 53
Andrew M. Davis and Pierre Bruneau
4.1 Introduction 54
4.2 What Solubility Measures to Model? 54
4.3 Is the Data Set Suitable for Modeling? 56
4.4 Descriptors and Modeling Methods for Developing Solubility Models 58
4.5 Comparing Literature Solubility Models 59
4.6 What Is the Influence of the Domain of Applicability? 63
4.7 Can We Tell when Good Predictions Are Made? 65
4.8 Conclusions 65
References 66
Part Two Physicochemical and Biological Studies of Membrane Permeability and Oral Absorption 69
5 Physicochemical Approaches to Drug Absorption 71
Han van de Waterbeemd
5.1 Introduction 73
5.2 Physicochemical Properties and Pharmacokinetics 74
5.2.1 DMPK 74
5.2.2 Lipophilicity, Permeability, and Absorption 74
5.2.3 Estimation of Volume of Distribution from Physical Chemistry 76
5.2.4 Plasma Protein Binding and Physicochemical Properties 76
5.3 Dissolution and Solubility 76
5.3.1 Calculated Solubility 78
5.4 Ionization (pKa) 78
5.4.1 Calculated pKa 79
5.5 Molecular Size and Shape 79
5.5.1 Calculated Size Descriptors 79
5.6 Hydrogen Bonding 80
5.6.1 Calculated Hydrogen-Bonding Descriptors 80
5.7 Lipophilicity 81
5.7.1 log P and log D 81
5.7.2 Calculated log P and log D 83
5.8 Permeability 84
5.8.1 Artificial Membranes and PAMPA 84
5.8.1.1 In Silico PAMPA 85
5.8.2 IAM, ILC, MEKC, and BMC 85
5.8.3 Liposome Partitioning 86
5.8.4 Biosensors 86
5.9 Amphiphilicity 86
5.10 Drug-Like Properties 87
5.11 Computation Versus Measurement of Physicochemical Properties 88
5.11.1 QSAR Modeling 88
5.11.2 In Combo: Using the Best of Two Worlds 89
5.12 Outlook 89
References 89
6 High-Throughput Measurement of Physicochemical Properties 101
Barbara P. Mason
6.1 Introduction 102
6.2 Positioning of Physicochemical Screening in Drug Discovery 102
6.3 ‘‘Fit for Purpose’’ Versus ‘‘Gold Standard’’ 103
6.4 Solubility 104
6.4.1 ‘‘Thermodynamic’’ Versus ‘‘Kinetic’’ 104
6.4.2 Methods of Measuring High-Throughput Solubility 106
6.4.3 Supernatant Concentration 106
6.4.4 Measuring Solubility Across a pH Range 107
6.4.5 Supernatant Concentration Methods from Solid Material 109
6.4.6 Precipitate Detection 109
6.4.7 Other Methods of Measuring Solubility 110
6.5 Dissociation Constants, pKa 110
6.5.1 Measuring pKa 111
6.5.2 pKa Measurements in Cosolvent Mixtures 112
6.5.3 pKa Measurements based on Separation 113
6.6 Lipophilicity 115
6.6.1 log P Versus log DpH 115
6.6.2 Measuring Lipophilicity 116
6.6.3 High-Throughput log D7.4 Measurements 117
6.6.4 High-Throughput log D7.4 Versus Shake-Flask log D7.4 117
6.6.5 Alternative Methods for Determining High-Throughput log DpH 118
6.7 Permeability 119
6.7.1 Permeability and Lipophilicity 121
6.7.2 Cell-Based Assays 121
6.7.3 Noncell-Based Assays: Chromatographic Methods 122
6.7.4 Noncell-Based Assays: Parallel Artificial Membrane Permeability Assay 122
6.7.4.1 Membrane Composition 123
6.7.4.2 Suggestions for PAMPA 123
6.7.4.3 Considerations in the Calculation of Permeability from PAMPA Data 124
6.7.5 Sink Conditions 125
6.7.6 Unstirred Water Layer 126
6.7.7 Surface Properties for the Determination of Permeability 126
6.8 Data Interpretation, Presentation, and Storage 126
6.9 Conclusions 127
References 127
7 An Overview of Caco-2 and Alternatives for Prediction of Intestinal Drug Transport and Absorption 133
Anna-Lena Ungell and Per Artursson
7.1 Introduction 134
7.2 Cell Cultures for Assessment of Intestinal Permeability 134
7.2.1 Caco-2 135
7.2.2 MDCK Cells 136
7.2.3 2/4/A1 Cells 137
7.2.4 Other Cell Lines 139
7.3 Correlation to Fraction of Oral Dose Absorbed 140
7.4 Cell Culture and Transport Experiments 141
7.4.1 Quality Control and Standardization 143
7.4.2 Optimizing Experimental Conditions: pH 144
7.4.3 Optimizing Experimental Conditions: Concentration Dependence 144
7.4.4 Optimizing Experimental Conditions: Solubility and BSA 145
7.5 Active Transport Studies in Caco-2 Cells 145
7.6 Metabolism Studies using Caco-2 Cells 146
7.7 Conclusions 147
References 148
8 Use of Animals for the Determination of Absorption and Bioavailability 161
Chris Logan
8.1 Introduction 162
8.1.1 ADME/PK in Drug Discovery 162
8.1.2 The Need for Prediction 163
8.2 Consideration of Absorption and Bioavailability 163
8.3 Choice of Animal Species 167
8.4 Methods 168
8.4.1 Radiolabels 169
8.4.2 Ex Vivo Methods for Absorption 169
8.4.2.1 Static Method 169
8.4.2.2 Perfusion Methods 170
8.4.3 In Vivo Methods 170
8.5 In Vivo Methods for Determining Bioavailability 171
8.5.1 Cassette Dosing 171
8.5.2 Semisimultaneous Dosing 172
8.5.3 Hepatic Portal Vein Cannulation 173
8.6 Inhalation 173
8.7 Relevance of Animal Models 174
8.7.1 Models for Prediction of Absorption 174
8.7.2 Models for Prediction of Volume 175
8.8 Prediction of Dose in Man 176
8.8.1 Allometry 176
8.8.2 Physiologically Based Pharmacokinetics 176
8.8.3 Prediction of Human Dose 177
8.9 Conclusions 179
References 179
9 In Vivo Permeability Studies in the Gastrointestinal Tract of Humans 185
Niclas Petri and Hans Lennernäs
9.1 Introduction 185
9.2 Definitions of Intestinal Absorption, Presystemic Metabolism, and Absolute Bioavailability 188
9.3 Methodological Aspects of In Vitro Intestinal Perfusion Techniques 190
9.4 Paracellular Passive Diffusion 193
9.5 Transcellular Passive Diffusion 196
9.6 Carrier-Mediated Intestinal Absorption 199
9.7 Jejunal Transport and Metabolism 202
9.8 Regional Differences in Transport and Metabolism of Drugs 208
9.9 Conclusions 209
References 210
Part Three Role of Transporters and Metabolism in Oral Absorption 221
10 Transporters in the Gastrointestinal Tract 223
Pascale Anderle and Carsten U. Nielsen
10.1 Introduction 223
10.2 Active Transport Along the Intestine and Influence on Drug Absorption 228
10.2.1 Peptide Transporters 232
10.2.2 Nucleoside Transporters 233
10.2.3 Amino Acid Transporters 234
10.2.4 Monosaccharide Transporters 234
10.2.5 Organic Cation Transporters 235
10.2.6 Organic Anion Transporters 235
10.2.7 Monocarboxylate Transporters 235
10.2.8 ABC Transporters 235
10.2.9 Bile Acid Transporters 237
10.3 Transporters and Genomics 237
10.3.1 Introduction to Genomics Technologies 237
10.3.2 Gene Expression Profiling Along the Intestine and in Caco-2 Cells 238
10.3.2.1 Profiling of the Intestinal Mucosa 238
10.3.2.2 Profiling of Caco-2 Cells 240
10.3.3 Intestinal Transporters and the Influence of Genotypes 242
10.4 Structural Requirements for Targeting Absorptive Intestinal Transporters 245
10.4.1 Strategies for Increasing Drug Absorption Targeting Transporters 245
10.4.2 Changing the Substrate: SAR Established for PEPT1 247
10.4.3 Methods for Investigating Affinity and Translocation 248
10.4.4 Quantitative Structure–Activity Relations for Binding of Drug to Transporters 249
10.5 Transporters and Diseased States of the Intestine 251
10.5.1 Intestinal Diseases 251
10.5.2 Basic Mechanisms in Cancer and Specifically in Colon Carcinogenesis 252
10.5.2.1 Basic Mechanisms 252
10.5.2.2 Colon Cancer 253
10.5.3 Transporters and Colon Cancer 253
10.5.3.1 Transporters as Tumor Suppressor Genes 255
10.5.3.2 Role of Transporters in the Tumor–Stroma Interaction 255
10.5.3.3 Role of Transporters in Intestinal Stem Cells 258
10.5.4 Role of PEPT1 in Inflammatory Bowel Disease 259
10.6 Summary and Outlook 260
References 261
11 Hepatic Transport 277
Kazuya Maeda, Hiroshi Suzuki, and Yuichi Sugiyama
11.1 Introduction 278
11.2 Hepatic Uptake 278
11.2.1 NTCP (SLC10A1) 279
11.2.2 OATP (SLCO) Family Transporters 279
11.2.3 OAT (SLC22) Family Transporters 281
11.2.4 OCT (SLC22) Family Transporters 284
11.3 Biliary Excretion 284
11.3.1 MDR1 (P-glycoprotein; ABCB1) 287
11.3.2 MRP2 (ABCC2) 287
11.3.3 BCRP (ABCG2) 289
11.3.4 BSEP (ABCB11) 290
11.3.5 MATE1 (SLC47A1) 290
11.4 Sinusoidal Efflux 290
11.4.1 MRP3 (ABCC3) 291
11.4.2 MRP4 (ABCC4) 291
11.4.3 Other Transporters 293
11.5 Prediction of Hepatobiliary Transport of Substrates from In Vitro Data 294
11.5.1 Prediction of Hepatic Uptake Process from In Vitro Data 294
11.5.2 Prediction of the Contribution of Each Transporter to the Overall Hepatic Uptake 295
11.5.3 Prediction of Hepatic Efflux Process from In Vitro Data 298
11.5.4 Utilization of Double (Multiple) Transfected Cells for the Characterization of Hepatobiliary Transport 299
11.6 Genetic Polymorphism of Transporters and Its Clinical Relevance 301
11.7 Transporter-Mediated Drug–Drug Interactions 305
11.7.1 Effect of Drugs on the Activity of Uptake Transporters Located on the Sinusoidal Membrane 305
11.7.2 Effect of Drugs on the Activity of Efflux Transporters Located on the Bile Canalicular Membrane 308
11.7.3 Prediction of Drug–Drug Interaction from In Vitro Data 309
11.8 Concluding Remarks 309
References 311
12 The Importance of Gut Wall Metabolism in Determining Drug Bioavailability 333
Christopher Kohl
12.1 Introduction 334
12.2 Physiology of the Intestinal Mucosa 334
12.3 Drug-Metabolizing Enzymes in the Human Mucosa 336
12.3.1 Cytochrome P450 336
12.3.2 Glucuronyltransferase 337
12.3.3 Sulfotransferase 337
12.3.4 Other Enzymes 337
12.4 Oral Bioavailability 341
12.4.1 In Vivo Approaches to Differentiate Between Intestinal and Hepatic First-Pass Metabolism 342
12.4.2 In Vitro Approaches to Estimate Intestinal Metabolism 344
12.4.3 Computational Approaches to Estimate and to Predict Human Intestinal Metabolism 345
12.5 Clinical Relevance of Gut Wall First-Pass Metabolism 347
References 347
13 Modified Cell Lines 359
Guangqing Xiao and Charles L. Crespi
13.1 Introduction 359
13.2 Cell/Vector Systems 360
13.3 Expression of Individual Metabolic Enzymes 363
13.4 Expression of Transporters 365
13.4.1 Efflux Transporters 365
13.4.2 Uptake Transporters 367
13.5 Summary and Future Perspectives 368
References 368
Part Four Computational Approaches to Drug Absorption and Bioavailability 373
14 Calculated Molecular Properties and Multivariate Statistical Analysis 375
Ulf Norinder
14.1 Introduction 377
14.2 Calculated Molecular Descriptors 377
14.2.1 2D-Based Molecular Descriptors 377
14.2.1.1 Constitutional Descriptors 378
14.2.1.2 Fragment- and Functional Group-Based Descriptors 378
14.2.1.3 Topological Descriptors 379
14.2.2 3D Descriptors 381
14.2.2.1 WHIM Descriptors 381
14.2.2.2 Jurs Descriptors 382
14.2.2.3 VolSurf and Almond Descriptors 383
14.2.2.4 Pharmacophore Fingerprints 384
14.2.3 Property-Based Descriptors 385
14.2.3.1 log P 385
14.2.3.2 HYBOT Descriptors 386
14.2.3.3 Abraham Descriptors 386
14.2.3.4 Polar Surface Area 386
14.3 Statistical Methods 387
14.3.1 Linear and Nonlinear Methods 388
14.3.1.1 Multiple Linear Regression 388
14.3.1.2 Partial Least Squares 389
14.3.1.3 Artificial Neural Networks 390
14.3.1.4 Bayesian Neural Networks 390
14.3.1.5 Support Vector Machines 390
14.3.1.6 k-Nearest Neighbor Modeling 392
14.3.1.7 Linear Discriminant Analysis 392
14.3.2 Partitioning Methods 393
14.3.2.1 Traditional Rule-Based Methods 393
14.3.2.2 Rule-Based Methods Using Genetic Programming 394
14.3.3 Consensus and Ensemble Methods 395
14.4 Applicability Domain 396
14.5 Training and Test Set Selection and Model Validation 398
14.5.1 Training and Test Set Selection 398
14.5.2 Model Validation 399
14.6 Future Outlook 400
References 401
15 Computational Absorption Prediction 409
Christel A.S. Bergström, Markus Haeberlein, and Ulf Norinder
15.1 Introduction 410
15.2 Descriptors Influencing Absorption 410
15.2.1 Solubility 411
15.2.2 Membrane Permeability 412
15.3 Computational Models of Oral Absorption 413
15.3.1 Quantitative Predictions of Oral Absorption 413
15.3.1.1 Responses: Evaluations of Measurement of Fraction Absorbed 417
15.3.1.2 Model Development: Data sets, Descriptors, Technologies, and Applicability 419
15.3.2 Qualitative Predictions of Oral Absorption 420
15.3.2.1 Model Development: Data sets, Descriptors, Technologies, and Applicability 420
15.3.2.2 An Example Using Genetic Programming-Based Rule Extraction 426
15.3.3 Repeated Use of Data Sets 427
15.4 Software for Absorption Prediction 427
15.5 Future Outlook 428
References 429
16 In Silico Prediction of Human Bioavailability 433
David J. Livingstone and Han van de Waterbeemd
16.1 Introduction 434
16.2 Concepts of Pharmacokinetics and Role of Oral Bioavailability 437
16.3 In Silico QSAR Models of Oral Bioavailability 438
16.3.1 Prediction of Human Bioavailability 438
16.3.2 Prediction of Animal Bioavailability 441
16.4 Prediction of the Components of Bioavailability 441
16.5 Using Physiological Modeling to Predict Oral Bioavailability 443
16.6 Conclusions 445
References 446
17 Simulations of Absorption, Metabolism, and Bioavailability 453
Michael B. Bolger, Robert Fraczkiewicz, and Viera Lukacova
17.1 Introduction 454
17.2 Background 454
17.3 Use of Rule-Based Computational Alerts in Early Discovery 456
17.3.1 Simple Rules for Drug Absorption (Druggability) 456
17.3.2 Complex Rules That Include Toxicity 473
17.4 Mechanistic Simulation (ACAT Models) in Early Discovery 474
17.4.1 Automatic Scaling of k’a 0 as a Function of Peff, pH, log D, and GI Surface Area 477
17.4.2 Mechanistic Corrections for Active Transport and Efflux 478
17.4.3 PBPK and In Silico Estimation of Distribution 481
17.5 Mechanistic Simulation of Bioavailability (Drug Development) 481
17.5.1 Approaches to In Silico Estimation of Metabolism 484
17.6 Regulatory Aspects of Modeling and Simulation (FDA Critical Path Initiative) 484
17.7 Conclusions 485
References 485
18 Toward Understanding P-Glycoprotein Structure–Activity Relationships 497
Anna Seelig
18.1 Introduction 498
18.1.1 Similarity Between P-gp and Other ABC Transporters 498
18.1.2 Why P-gp Is Special 500
18.2 Measurement of P-gp Function 500
18.2.1 P-gp ATPase Activity Assay 500
18.2.1.1 Quantification of Substrate–Transporter Interactions 503
18.2.1.2 Relationship between Substrate–Transporter Affinity and Rate of Transport 504
18.2.2 Transport Assays 506
18.2.3 Competition Assays 508
18.3 Predictive In Silico Models 508
18.3.1 Introduction to Structure–Activity Relationship 509
18.3.2 3D-QSAR Pharmacophore Models 509
18.3.3 Linear Discriminant Models 510
18.3.4 Modular Binding Approach 511
18.3.5 Rule-Based Approaches 512
18.4 Discussion 513
18.4.1 Prediction of Substrate-P-gp Interactions 513
18.4.2 Prediction of ATPase Activity or Intrinsic Transport 513
18.4.3 Prediction of Transport (i.e., Apparent Transport) 513
18.4.4 Prediction of Competition 514
18.4.5 Conclusions 514
References 514
Part Five Drug Development Issues 521
19 Application of the Biopharmaceutics Classification System Now and in the Future 523
Bertil Abrahamsson and Hans Lennernäs
19.1 Introduction 524
19.2 Definition of Absorption and Bioavailability of Drugs Following Oral Administration 527
19.3 Dissolution and Solubility 528
19.4 The Effective Intestinal Permeability (Peff) 535
19.5 Luminal Degradation and Binding 539
19.6 The Biopharmaceutics Classification System 541
19.6.1 Regulatory Aspects 541
19.6.1.1 Present Situation 541
19.6.1.2 Potential Future Extensions 543
19.6.2 Drug Development Aspects 543
19.6.2.1 Selection of Candidate Drugs 544
19.6.2.2 Choice of Formulation Principle 545
19.6.2.3 In Vitro/In Vivo Correlation 547
19.6.2.4 Food–Drug Interactions 549
19.6.2.5 Quality by Design 552
19.7 Conclusions 552
References 553
20 Prodrugs 559
Bernard Testa
20.1 Introduction 559
20.2 Why Prodrugs? 560
20.2.1 Pharmaceutical Objectives 560
20.2.2 Pharmacokinetic Objectives 561
20.2.3 Pharmacodynamic Objectives 564
20.3 How Prodrugs? 565
20.3.1 Types of Prodrugs 565
20.3.2 Hurdles in Prodrug Research 567
20.4 Conclusions 568
References 568
21 Modern Delivery Strategies: Physiological Considerations for Orally Administered Medications 571
Clive G. Wilson and Werner Weitschies
21.1 Introduction 571
21.2 The Targets 572
21.3 The Upper GI Tract: Mouth and Esophagus 573
21.3.1 Swallowing the Bitter Pill... 575
21.4 Mid-GI Tract: Stomach and Intestine 576
21.4.1 Gastric Inhomogeneity 576
21.4.2 Gastric Emptying 579
21.4.3 Small Intestinal Transit Patterns 581
21.4.4 Modulation of Transit to Prolong the Absorption Phase 582
21.4.5 Absorption Enhancement 582
21.5 The Lower GI Tract: The Colon 583
21.5.1 Colonic Transit 584
21.5.2 Time of Dosing 585
21.5.3 Modulating Colonic Water 586
21.6 Pathophysiological Effects on Transit 587
21.7 Pathophysiological Effects on Permeability 589
21.8 pH 589
21.9 Conclusions 590
References 590
22 Nanotechnology for Improved Drug Bioavailability 597
Marjo Yliperttula and Arto Urtti
22.1 Introduction 597
22.2 Nanotechnological Systems in Drug Delivery 599
22.2.1 Classification of the Technologies 599
22.2.1.1 Nanocrystals 599
22.2.1.2 Self-Assembling Nanoparticulates 600
22.2.1.3 Processed Nanoparticulates 601
22.2.1.4 Single-Molecule-Based Nanocarriers 601
22.2.2 Pharmaceutical Properties of Nanotechnological Formulations 601
22.2.2.1 Drug-Loading Capacity 601
22.2.2.2 Processing 602
22.2.2.3 Biological Stability 602
22.3 Delivery via Nanotechnologies 603
22.3.1 Delivery Aspects at Cellular Level 603
22.3.2 Nanosystems for Improved Oral Drug Bioavailability 606
22.3.3 Nanosystems for Improved Local Drug Bioavailability 606
22.4 Key Issues and Future Prospects 608
References 609
Index 613
