Phosphodiesterases and Their Inhibitors

Description

Written by the pioneers of Viagra, the first blockbuster PDE inhibitor drug.

Beginning with a review of the first wave of phosphodiesterase (PDE) inhibitors, this book focuses on new and emerging PDE targets and their inhibitors. Drug development options for all major human PDE families are discussed and cover diverse therapeutic fields, such as neurological/psychiatric, cardiovascular/metabolic, pain, and allergy/respiratory diseases. Finally, emerging chemotherapeutic applications of PDE inhibitors against malaria and other tropical diseases are discussed.

Table of Contents

List of Contributors
Preface
A Personal Foreword

1 Introduction 1
Andrew S. Bell and Spiros Liras

2 Toward a New Generation of PDE5 Inhibitors through Advances in Medicinal Chemistry 9
Dafydd R. Owen

• 2.1 Introduction 9
• 2.2 The First-Generation Agents 10
• 2.3 PDE5 as a Mechanism and Alternative Indications Beyond MED 11
• 2.4 A Summary of PDE5 Chemotypes Reported Post-2010 11
• 2.5 Second-Generation PDE5 Inhibitors from Pfizer: Pyrazolopyrimidines 12
• 2.6 Second-Generation PDE5 Inhibitors from Pfizer: Pyridopyrazinones 18
• 2.7 Conclusions 25
• References 25

3 PDE4: New Structural Insights into the Regulatory Mechanism and Implications for the Design of Selective Inhibitors 29
Jayvardhan Pandit

• 3.1 Introduction 29
• 3.2 Isoforms, Domain Organization, and Splice Variants 30
• 3.3 Structural Features of the Catalytic Site 31
• 3.4 Regulation of PDE4 Activity 32
• 3.5 Crystal Structure of Regulatory Domains of PDE4 33
• 3.6 UCR2 Interaction and Selectivity 38
• 3.7 Conclusions 39
• References 40

4 PDE4: Recent Medicinal Chemistry Strategies to Mitigate Adverse Effects 45
Etzer Darout, Elnaz Menhaji-Klotz, and Thomas A. Chappie

• 4.1 Introduction 45
• 4.2 Brief Summary of pan-PDE4 Inhibitors 46
• 4.2.1 Rolipram 47
• 4.2.2 Roflumilast 48
• 4.2.3 Cilomilast 48
• 4.2.4 Apremilast 49
• 4.3 PDE4 Strategies to Avoid Gastrointestinal Events 49
• 4.3.1 Allosteric Modulation 49
• 4.3.2 PDE4D Selectivity 53
• 4.3.3 Pfizer 53
• 4.3.4 Novartis 54
• 4.3.5 Merck-Frosst 54
• 4.3.6 GEBR-7b 55
• 4.3.7 PDE4B Selectivity 55
• 4.3.8 Asahi Kasei 56
• 4.3.9 GlaxoSmithKline 56
• 4.3.10 Pfizer 57
• 4.3.11 Tissue Targeting 57
• 4.3.12 Polypharmacology 58
• 4.3.13 Olanzapine Derivatives 58
• 4.4 Conclusions 59
• References 60

5 The Function, Enzyme Kinetics, Structural Biology, and Medicinal Chemistry of PDE10A 65
Thomas A. Chappie and Patrick Verhoest

• 5.1 Enzymology and Protein Structure 66
• 5.2 Papaverine-Related PDE10A Inhibitors 69
• 5.3 MP-10/PF-2545920 Class of Inhibitors 72
• 5.4 PF-2545920/MP-Inspired Inhibitors 74
• 5.5 PF-2545920/Papaverine/Quinazoline Hybrid Series of Inhibitors 75
• 5.6 PET Ligand Development 77
• 5.7 Summary and Future 79
• References 79

6 The State of the Art in Selective PDE2A Inhibitor Design 83
Christopher W. am Ende, Bethany L. Kormos, and John M. Humphrey

• 6.1 Introduction 83
• 6.2 Selective PDE2A Inhibitors 84
• 6.2.1 Bayer 84
• 6.2.2 Altana AG 85
• 6.2.3 Biotie Therapies 87
• 6.2.4 Boehringer Ingelheim 88
• 6.2.5 Janssen 89
• 6.2.6 Lundbeck 92
• 6.2.7 Merck 93
• 6.2.8 Neuro3d 95
• 6.2.9 Pfizer 95
• 6.3 Methods 100
• 6.4 Conclusions 100
• References 101

7 Crystal Structures of Phosphodiesterase 9A and Insight into Inhibitor Discovery 105
Hengming Ke, Yousheng Wang, Yiqian Wan, and Hai-Bin Luo

• 7.1 Introduction 105
• 7.2 Subtle Asymmetry of the PDE9 Dimer in the Crystals 105
• 7.3 The Structure of the PDE9 Catalytic Domain 107
• 7.4 Interaction of Inhibitors with PDE9 108
• 7.5 Implication on Inhibitor Selectivity 110
• References 114

8 PDEs as CNS Targets: PDE9 Inhibitors for Cognitive Deficit Diseases 117
Michelle M. Claffey, Christopher J. Helal, and Xinjun Hou

• 8.1 PDE9A Enzymology and Pharmacology 117
• 8.2 Crystal Structures of PDE9A Inhibitors 119
• 8.3 Medicinal Chemistry Efforts toward Identifying PDE9A Inhibitors for Treating Cognitive Disorders 120
• 8.3.1 Bayer 120
• 8.3.2 Pfizer 125
• 8.3.3 Boehringer Ingelheim 129
• 8.3.4 Sun Yat-Sen University, China 132
• 8.3.5 Envivo Pharmaceuticals 133
• 8.4 Analysis of CNS Desirability of PDE9A Inhibitors 135
• 8.5 Conclusions 135
• References 137

9 Phosphodiesterase 8B 141
Stephen W. Wright

• 9.1 Introduction 141
• 9.2 Identification 141
• 9.3 Properties 142
• 9.4 Expression and Tissue Distribution 143
• 9.5 Functions of PDE8B 143
• 9.5.1 Thyroid 144
• 9.5.2 Adrenal Gland 144
• 9.5.3 Pancreatic Islets 144
• 9.6 Inhibitors and Potential Therapeutic Uses 145
• References 150

10 Selective New Small-Molecule Inhibitors of Phosphodiesterase 1 155
John M. Humphrey

• 10.1 Introduction 155
• 10.2 PDE1 Enzymology 155
• 10.3 PDE1 Inhibitors 156
• 10.3.1 Non-Selective PDE1 Inhibitors 156
• 10.3.2 Selective PDE1 inhibitors 158
• 10.4 Conclusion 161
• References 163

11 Recent Advances in the Development of PDE7 Inhibitors 165
Nigel A. Swain and Rainer Gewald

• 11.1 Introduction 165
• 11.1.1 PDE7: Subtypes and Distribution 165
• 11.1.2 Rationale for PDE7 as a Therapeutic Target 166
• 11.2 Historical Development of PDE7 Inhibitors 166
• 11.2.1 Early Examples of Nonselective and Selective Lead Matter 166
• 11.2.2 Developing Selective Lead Matter from Nonselective Hits 167
• 11.2.3 Targeting PDE4/7 Dual Inhibitors 168
• 11.3 Recent Advances in the Discovery of PDE7 Inhibitors for Peripheral Therapeutic Benefit 169
• 11.3.1 PDE7 Inhibitors for the Treatment of T Cell-Related Disorders 169
• 11.3.1.1 Developments in PDE7 Inhibitors for the Treatment of Airway-Related Disorders 170
• 11.3.1.2 Developments in PDE7 Inhibitors for the Treatment of Nonairway-Related Disorders 171
• 11.3.1.3 Summary of T-Cell-Related Research 171
• 11.3.2 PDE7 Inhibitors for the Treatment of Neuropathic Pain 172
• 11.4 Recent Advances in the Discovery of PDE7 Inhibitors for CNS-Related Disorders 173
• 11.4.1 Creating PDE7 Inhibitors by Ligand-Based Virtual Screening Methods 173
• 11.4.2 Repositioning PDE7 Inhibitors Designed for the Treatment of Peripheral Diseases 176
• 11.5 Recent Advances in the Discovery of Dual PDE7 Inhibitors 178
• 11.5.1 Dual PDE4/7 Inhibitors 178
• 11.5.2 Dual PDE7/8 Inhibitors 180
• 11.6 Identifying Next-Generation PDE7 Inhibitors 181
• 11.6.1 Emerging Chemotypes as Novel PDE7 Inhibitors 181
• 11.6.2 Novel Methods to Identify PDE7 Inhibitors 182
• 11.6.2.1 Computational Methods to Identify New PDE7 Inhibitors 182
• 11.6.2.2 Fission Yeast-Based HTS to Identify New PDE7 Inhibitors 183
• 11.7 Summary 184
• References 185

12 Inhibitors of Protozoan Phosphodiesterases as Potential Therapeutic Approaches for Tropical Diseases 191
Jennifer L. Woodring and Michael P. Pollastri

• 12.1 Introduction 191
• 12.2 Malaria 192
• 12.2.1 PfPDE Inhibition Studies 193
• 12.3 Chagas Disease 195
• 12.4 Leishmaniasis 197
• 12.5 Human African Trypanosomiasis 200
• 12.6 Conclusion 205

References 206
Index 211

Author Information

Spiros Liras is the head of the cardiovascular metabolic and endocrine diseases (CVMED) medicinal chemistry department at Pfizer R&D in Groton (USA). Previously, he was Senior Director of medicinal chemistry in Neuroscience at Pfizer, working on treatments for addiction, depression, schizophrenia, cognition and Alzheimer's disease. Dr. Liras obtained a Ph.D. in organic chemistry in 1989 from Iowa State University. Subsequently, he joined the group of Professor Stephen F. Martin at the University of Texas at Austin as a postdoctoral fellow. He is the author or coauthor of more than 50 publications and patents.

Andrew Bell has been with Pfizer for over 30 years, following studies at York University (UK). He spent the first 9 years of his career working on PDE inhibitors leading to the inotrope/vasodilator (PDE3) candidate, nanterinone, and the PDE5 inhibitor, sildenafil (Viagra, Revatio). Soon after the discovery of sildenafil in 1989, he moved to antifungals research until 1999, when he was given responsibility for File Enrichment, as part of Pfizer's collaborations with ArQule and Tripos. He has subsequently been working in the hit-to-lead arena in Pfizer's Sandwich and Groton Laboratories, making use of the File Enrichment investment to generate new lead series for multiple projects, including novel series of selective PDE inhibitors. Dr. Bell was awarded one of the 2008 Awards for Technical Achievements in Organic Chemistry by the American Chemical Society.