Metabolite Safety in Drug Development

Suzanne L. Iverson, PhD, ERT, earned her PhD studying reactive drug metabolites and idiosyncratic drug reactions (University of Toronto, Dr. Jack Uetrecht supervisor) and has worked in the pharmaceutical industry for over 14 years as principal scientist and manager of development in vitro/in vivo metabolism and distribution imaging as well as functional project leader for both DMPK and safety assessment functions. Since 2011, she has served on the management committee of the Drug Metabolism Discussion Group, UK, and the Board of the PK–Metabolism subcommittee of the Swedish Pharmaceutical Society.Dennis A. Smith, PhD, currently holds part-time advisory and academic positions and, previously, worked in the pharmaceutical industry for 32 years. He has coauthored over 150 publications, including Attrition in the Pharmaceutical Industry (Wiley, 2016), Reactive Drug Metabolites (Wiley, 2012), and three editions of the book Pharmacokinetics and Metabolism in Drug Design (Wiley, 2012).

"Written by individuals who collectively possess hundreds of years of experience within the drug metabolism field, the wealth of information and insight contained is amazing. The purpose of the tome is to provide the reader with, �... a comprehensive overview of why and how metabolites are studied during drug development in the pharmaceutical industry� (page 13). This objective is certainly achieved in a lucid, scholarly and engaging manner. I would not hesitate to recommend this book to anyone interested in this subject and also for those who may wish to delve into this area." (ISSX Newsletter, April 2017)

• Preface xiList of Contributors xiii1 Introduction: History of Metabolite Safety in Drug Development 1Dennis A. Smith and Suzanne L. Iverson1.1 People, Events, and Reaction, 11.2 The Rise of Industrial Drug Metabolism, 21.3 The Appearance of Mist, 41.4 The Journey Triggered by Thalidomide: Would Present Science have Made a Difference?, 51.5 Key Events from Thalidomide to Mist, 81.6 The Purpose of this Book, 13References, 142 “Mist” and other Metabolite Guidelines in the Context of Industrial Drug Metabolism 17Gordon J. Dear and Angus N. R. Nedderman2.1 A Historical Perspective, 172.2 The Emergence of the Regulatory Guidance Documents, 232.3 Impact of the Guidelines, 302.4 Future Directions, 32References, 373 Metabolite Technology: Qualitative and Quantitative 45Gordon J. Dear and Andrew McEwen3.1 Introduction, 453.2 Clinical Samples, 463.3 Preclinical Samples, 483.4 Radiolabeled Test Compounds, 513.5 Mass Spectrometry, 553.6 NMR Spectroscopy, 653.7 Accelerator Mass Spectrometry, 72References, 75Further Reading, 854 In Vitro Methods for Evaluation of Drug Metabolism: Identification of Active and Inactive Metabolites and the Enzymes that Generate them 87R. Scott Obach, Amit S. Kalgutkar, and Deepak K. Dalvie4.1 Introduction, 874.2 In Vitro Methods for Metabolite Profiling and Identification, 884.2.1 In Vitro Systems We Use: Most Complex to Simplest, 884.2.2 Criteria for Selecting the Most Appropriate In Vitro System for In Vitro Metabolite Profiling, 924.3 Application of In Vitro Methods for Metabolite Profiling in Drug Discovery and Development, 964.3.1 In Vitro Metabolite Profiling and Identification in the Early Drug Discovery Stage, 964.3.2 In Vitro Metabolite Profiling and Identification in the Late Drug Discovery Stage: Selection of Candidate Compounds for Further Development, 984.3.3 In Vitro Metabolite Profiling and Identification in the Drug Development Stage: Support of CandidateCompounds for New Drug Registration, 1014.4 How Well Do In Vitro Metabolite Profiles Represent In Vivo Metabolite Profiles?, 1034.5 Pharmacologically Active Metabolites and their Identification, 1044.5.1 When Is a Metabolite Considered Active?, 1044.5.2 Experimental Approaches to Reveal Active Metabolites, 1064.6 Conclusion, 108References, 1085 Integrated Reactive Metabolite Strategies 111J. Gerry Kenna and Richard A. Thompson5.1 Introduction, 1115.2 Role of RMs in Toxicity, 1145.3 Strategies for Predicting, Assessing, and Derisking RM-Mediated Toxicity, 1185.3.1 Assessing RM Hazard: Awareness/Avoidance, 1185.3.2 Assessing RM Risk: Covalent Binding and Dose, 1225.3.3 Integrated Risk Assessments: Integrating RM Assessment and In Vitro Safety Assay Endpoints, 1275.3.4 Integrated RM Risk Assessments: Future Directions, 129References, 1316 Understanding Drug Metabolism in Humans: In Vivo 141Lars Weidolf and Ian D. Wilson6.1 Introduction, 1416.2 Preclinical Animal Studies, 1426.2.1 Whole-Body Autoradiography and Imaging, 1446.3 Early Human In Vivo Metabolism Studies, 1466.3.1 Pre-FTIM Data Acquisition, 1476.3.2 The First Clinical Studies, 1496.3.3 Metabolite Exposure Assessment, 1506.3.4 Exceptions to Regulatory Recommendations, 1536.3.5 Dealing with DHMs, 1536.3.6 The Human ADME Study, 1566.3.7 Early Metabolite Exposure Assessment and Relevance to the Target Patient Population, 1596.3.8 Summary, 1606.4 The “What ifs…?”, 1626.5 Sources of Variability in In Vivo Biotransformation Studies: Species, Strain, Age, and Sex Differences, 1626.6 Extrahepatic Drug Metabolism (Animals and Man), 1646.7 Nonhuman Metabolism in Humans, 1666.8 Nonhuman Models of Human In Vivo Metabolism, 1676.8.1 “Humanized” Transgenic Mice, 1686.8.2 “Chimeric” Humanized Mice, 1696.9 Alternatives to Radiolabels, 1706.10 Conclusions, 171References, 1727 Topical Administration and Safety Testing of Metabolites 177Vibeke Hougaard Sunesen7.1 Introduction, 1777.2 Skin Structure and Function of the Epidermal Layer, 1787.3 Skin Models, 1807.3.1 In Vivo Studies, 1817.3.2 Ex Vivo Skin, 1827.3.3 In Vitro Skin Models, 1827.4 Metabolic Capacity of Human Skin, 1867.4.1 Phase 1 Enzymes, 1867.4.2 Non-CYP Phase 1 Enzymes, 1907.4.3 Phase 2 Enzymes, 1937.5 Species Differences in Metabolic Capacity of the Skin, 1967.6 Metabolic Capacity of Diseased Skin, 1977.7 Soft Drug Approach, 1987.7.1 Soft Corticosteroids, 1997.7.2 PDE4 Inhibitors, 2007.8 Exposure to Metabolites and Risk of Adverse Events, 2027.8.1 Drug Interaction Potential, 2047.8.2 Toxicities and Safety Concerns, 205References, 2068 In Silico Modeling of Metabolite Kinetics 213Lu Gaohua, Howard Burt, Helen Humphries, Amin Rostami-Hodjegan, and Masoud Jamei8.1 Introduction, 2138.1.1 Why Do We Need to Model Metabolite PK?, 2138.1.2 Brief Review of Existing PBPK Models of Metabolites, 2148.2 Simcyp Approach to Modeling Metabolite PBPK, 2158.2.1 Parent/Metabolite PBPK Model Structure, 2158.2.2 Formation/Absorption of the Metabolite, 2178.2.3 Distribution of Metabolite, 2198.2.4 Elimination of Metabolite, 2228.2.5 Interaction of Metabolite, 2228.3 Model Verifications, 2238.3.1 Comparison of Prediction versus Observation, 2238.3.2 What-If Simulation Examples, 2238.4 Discussion, 2308.4.1 Role of M&S in Handling Metabolites, 2308.4.2 How to Deal with Multiple Metabolites, 2318.4.3 Role of M&S of Metabolites in Regulatory Submissions, 2328.5 Concluding Remarks, 2328.5.1 What has been Achieved?, 2328.5.2 Future Works, 232Glossary, 233Superscription, 233Subscription, 234References, 2349 Introduction to Case Studies 239Suzanne L. IversonReferences, 24210 A Mass Balance and Metabolite Profiling Study of Sonidegib in Healthy Male Subjects Using Microtrace Approach 243Piet Swart, Frederic Lozac’h, and Markus Zollinger10.1 Introduction to the Study, 24310.2 Radioactive Dose Limitations, 24510.3 Results, 24610.4 Metabolite Profiling and Identification, 249Acknowledgments, 258References, 25811 Dealing with Reality: When is it Necessary to Qualify and Quantify Metabolites? Some Case Studies 261Deepak K. Dalvie, R. Scott Obach, and Amit S. Kalgutkar11.1 Introduction, 26111.2 Case Study 1, 26111.3 Case Study 2, 26511.4 Case Study 3, 268References, 27112 The Value of Metabolite Identification and Quantification in Clinical Studies. Some Case Studies Enabling Early Assessment of Safety in Humans: GlaxoSmithKline 275Jackie Bloomer, Claire Beaumont, Gordon J. Dear, Stephanie North, and Graeme Young12.1 GW644784: Species-Specific Metabolites, 27612.2 Danirixin: Assessment of Victim Drug Interaction Risk Using Bile Sampling, 27912.3 Sitamaquine: Unique, Active, and Possible Genotoxic Metabolites and Human Radiolabel Study Not Feasible, 28012.4 SB-773812: Concerns Over Long Half-Life Metabolite and Early Employment of Accelerator Mass Spectrometry, 28512.5 GW766994: Consideration of Steady-State Kinetics and Multiple Analytical Methodologies for an Accurate Assessment of Human Metabolism, 288References, 29013 The Importance of Dose- and Time-Dependent Pharmacokinetics During Early Metabolite Safety Assessment in Humans 293Laurent Leclercq, Marc Bockx, Hilde Bohets, Hans Stieltjes, Vikash Sinah, and Ellen ScheersReferences, 30314 Mist and the Future 305B. Kevin Park and Dennis A. Smith14.1 Introduction, 30514.2 Mist and Pharmacology, 30614.3 Reactive Metabolites, Pharmacology, and Mist, 30914.4 Implications of Drug Bioactivation and Covalent Binding for Mist, 30914.5 Drug Bioactivation and Drug Hepatotoxicity, 31114.6 Drug-Conjugate Formation and Drug Hypersensitivity, 31314.7 Drug Bioactivation, Conjugate Formation, and Drug Hypersensitivity, 31514.8 Toward a Mist Strategy for Reactive Metabolites, 317References, 318Index 323