<p>1. Introduction<br>1.1. Overview<br>1.2. Drugs Discovered without Rational Design<br> 1.2.1. Medicinal Chemistry Folklore<br> 1.2.2. Discovery of Penicillins<br> 1.2.3. Discovery of Librium<br> 1.2.4. Discovery of Drugs through Metabolism Studies<br> 1.2.5. Discovery of Drugs through Clinical Observations<br>1.3. Overview of Modern Rational Drug Design<br> 1.3.1. Overview of Drug Targets<br> 1.3.2. Identification and Validation of Targets for Drug Discovery<br> 1.3.3. Alternatives to Target-Based Drug Discovery<br> 1.3.4. Lead Discovery<br> 1.3.5. Lead Modification (Lead Optimization)<br> 1.3.5.1. Potency<br> 1.3.5.2. Selectivity<br> 1.3.5.3. Absorption, Distribution, Metabolism, and Excretion (ADME)<br> 1.3.5.4. Intellectual Property Position<br> 1.3.6. Drug Development<br> 1.3.6.1. Preclinical Development<br> 1.3.6.2. Clinical Development (Human Clinical Trials)<br> 1.3.6.3. Regulatory Approval to Market the Drug<br>1.4. Epilogue<br>1.5. General References<br>1.6. Problems<br>References<br>2. Lead Discovery and Lead Modification<br>2.1. Lead Discovery<br> 2.1.1. General Considerations<br> 2.1.2. Sources of Lead Compounds<br> 2.1.2.1. Endogenous Ligands<br> 2.1.2.2. Other Known Ligands<br> 2.1.2.3. Screening of Compounds<br> 2.1.2.3.1. Sources of Compounds for Screening<br> 2.1.2.3.1.1. Natural Products<br> 2.1.2.3.1.2. Medicinal Chemistry Collections and Other "Handcrafted" Compounds<br> 2.1.2.3.1.3. High-Throughput Organic Synthesis<br> 2.1.2.3.1.3.1. Solid-Phase Library Synthesis<br> 2.1.2.3.1.3.2. Solution-Phase Library Synthesis<br> 2.1.2.3.1.3.3. Evolution of HTOS<br> 2.1.2.3.2. Drug-Like, Lead-Like, and Other Desirable Properties of Compounds for Screening<br> 2.1.2.3.3. Random Screening<br> 2.1.2.3.4. Targeted (or Focused) Screening, Virtual Screening, and Computational Methods in Lead Discovery<br> 2.1.2.3.4.1. Virtual Screening Database<br> 2.1.2.3.4.2. Virtual Screening Hypothesis<br> 2.1.2.3.5. Hit-To-Lead Process<br> 2.1.2.3.6. Fragment-based Lead Discovery<br>2.2. Lead Modification<br> 2.2.1. Identification of the Active Part: The Pharmacophore<br> 2.2.2. Functional Group Modification<br> 2.2.3. Structure–Activity Relationships<br> 2.2.4. Structure Modifications to Increase Potency, Therapeutic Index, and ADME Properties<br> 2.2.4.1. Homologation<br> 2.2.4.2. Chain Branching<br> 2.2.4.3. Bioisosterism<br> 2.2.4.4. Conformational Constraints and Ring-Chain Transformations<br> 2.2.4.5. Peptidomimetics<br> 2.2.5. Structure Modifications to Increase Oral Bioavailability and Membrane Permeability<br> 2.2.5.1. Electronic Effects: The Hammett Equation<br> 2.2.5.2. Lipophilicity Effects<br> 2.2.5.2.1. Importance of Lipophilicity<br> 2.2.5.2.2. Measurement of Lipophilicities<br> 2.2.5.2.3. Computer Automation of log P Determination<br> 2.2.5.2.4. Membrane Lipophilicity<br> 2.2.5.3. Balancing Potency of Ionizable Compounds with Lipophilicity and Oral Bioavailability<br> 2.2.5.4. Properties that Influence Ability to Cross the Blood–Brain Barrier<br> 2.2.5.5. Correlation of Lipophilicity with Promiscuity and Toxicity<br> 2.2.6. Computational Methods in Lead Modification<br> 2.2.6.1. Overview<br> 2.2.6.2. Quantitative Structure–Activity Relationships (QSARs)<br> 2.2.6.2.1. Historical Overview. Steric Effects: The Taft Equation and Other Equations<br> 2.2.6.2.2. Methods Used to Correlate Physicochemical Parameters with Biological Activity<br> 2.2.6.2.2.1. Hansch Analysis: A Linear Multiple Regression Analysis<br> 2.2.6.2.2.2. Manual Stepwise Methods: Topliss Operational Schemes and Others<br> 2.2.6.2.2.3. Batch Selection Methods: Batchwise Topliss Operational Scheme, Cluster Analysis, and Others<br> 2.2.6.2.2.4. Free and Wilson or de Novo Method<br> 2.2.6.2.2.5. Computational Methods for ADME Descriptors<br> 2.2.6.3. Scaffold Hopping<br> 2.2.6.4. Molecular Graphics-Based Lead Modification<br> 2.2.7. Epilogue<br>2.3. General References<br>2.4. Problems<br>References<br>3. Receptors<br>3.1. Introduction<br>3.2. Drug–Receptor Interactions<br> 3.2.1. General Considerations<br> 3.2.2. Important Interactions (Forces) Involved in the Drug–Receptor Complex<br> 3.2.2.1. Covalent Bonds<br> 3.2.2.2. Ionic (or Electrostatic) Interactions<br> 3.2.2.3. Ion–Dipole and Dipole–Dipole Interactions<br> 3.2.2.4. Hydrogen Bonds<br> 3.2.2.5. Charge–Transfer Complexes<br> 3.2.2.6. Hydrophobic Interactions<br> 3.2.2.7. Cation–π Interaction<br> 3.2.2.8. Halogen Bonding<br> 3.2.2.9. van der Waals or London Dispersion Forces<br> 3.2.2.10. Conclusion<br> 3.2.3. Determination of Drug–Receptor Interactions<br> 3.2.4. Theories for Drug–Receptor Interactions<br> 3.2.4.1. Occupancy Theory<br> 3.2.4.2. Rate Theory<br> 3.2.4.3. Induced-Fit Theory<br> 3.2.4.4. Macromolecular Perturbation Theory<br> 3.2.4.5. Activation–Aggregation Theory<br> 3.2.4.6. The Two-State (Multistate) Model of Receptor Activation<br> 3.2.5. Topographical and Stereochemical Considerations<br> 3.2.5.1. Spatial Arrangement of Atoms<br> 3.2.5.2. Drug and Receptor Chirality<br> 3.2.5.3. Diastereomers<br> 3.2.5.4. Conformational Isomers<br> 3.2.5.5. Atropisomers<br> 3.2.5.6. Ring Topology<br> 3.2.6. Case History of the Pharmacodynamically Driven Design of a Receptor Antagonist: Cimetidine<br> 3.2.7. Case History of the Pharmacokinetically Driven Design of Suvorexant<br>3.3. General References<br>3.4. Problems<br>References<br>4. Enzymes<br>4.1. Enzymes as Catalysts<br> 4.1.1. What are Enzymes?<br> 4.1.2. How do Enzymes Work?<br> 4.1.2.1. Specificity of Enzyme-Catalyzed Reactions<br> 4.1.2.1.1. Binding Specificity<br> 4.1.2.1.2. Reaction Specificity<br> 4.1.2.2. Rate Acceleration<br>4.2. Mechanisms of Enzyme Catalysis<br> 4.2.1. Approximation<br> 4.2.2. Covalent Catalysis<br> 4.2.3. General Acid–Base Catalysis<br> 4.2.4. Electrostatic Catalysis<br> 4.2.5. Desolvation<br> 4.2.6. Strain or Distortion<br> 4.2.7. Example of the Mechanisms of Enzyme Catalysis<br>4.3. Coenzyme Catalysis<br> 4.3.1. Pyridoxal 5′-Phosphate<br> 4.3.1.1. Racemases<br> 4.3.1.2. Decarboxylases<br> 4.3.1.3. Aminotransferases (Formerly Transaminases)<br> 4.3.1.4. PLP-Dependent β-Elimination<br> 4.3.2. Tetrahydrofolate and Pyridine Nucleotides<br> 4.3.3. Flavin<br> 4.3.3.1. Two-Electron (Carbanion) Mechanism<br> 4.3.3.2. Carbanion Followed by Two One-Electron Transfers<br> 4.3.3.3. One-Electron Mechanism<br> 4.3.3.4. Hydride Mechanism<br> 4.3.4. Heme<br> 4.3.5. Adenosine Triphosphate and Coenzyme A<br>4.4. Enzyme Catalysis in Drug Discovery<br> 4.4.1. Enzymatic Synthesis of Chiral Drug Intermediates<br> 4.4.2. Enzyme Therapy<br>4.5. General References<br>4.6. Problems<br>References<br>5. Enzyme Inhibition and Inactivation<br>5.1. Why Inhibit an Enzyme?<br>5.2. Reversible Enzyme Inhibitors<br> 5.2.1. Mechanism of Reversible Inhibition<br> 5.2.2. Selected Examples of Competitive Reversible Inhibitor Drugs<br> 5.2.2.1. Simple Competitive Inhibition<br> 5.2.2.1.1. Epidermal Growth Factor Receptor Tyrosine Kinase as a Target for Cancer<br> 5.2.2.1.2. Discovery and Optimization of EGFR Inhibitors<br> 5.2.2.2. Stabilization of an Inactive Conformation: Imatinib, an Antileukemia Drug<br> 5.2.2.2.1. The Target: Bcr-Abl, a Constitutively Active Kinase<br> 5.2.2.2.2. Lead Discovery and Modification<br> 5.2.2.2.3. Binding Mode of Imatinib to Abl Kinase<br> 5.2.2.2.4. Inhibition of Other Kinases by Imatinib<br> 5.2.2.3. Alternative Substrate Inhibition: Sulfonamide Antibacterial Agents (Sulfa Drugs)<br> 5.2.2.3.1. Lead Discovery<br> 5.2.2.3.2. Lead Modification<br> 5.2.2.3.3. Mechanism of Action<br> 5.2.3. Transition State Analogs and Multisubstrate Analogs<br> 5.2.3.1. Theoretical Basis<br> 5.2.3.2. Transition State Analogs<br> 5.2.3.2.1. Enalaprilat<br> 5.2.3.2.2. Pentostatin<br> 5.2.3.2.3. Forodesine and DADMe-ImmH<br> 5.2.3.2.4. Multisubstrate Analogs<br> 5.2.4. Slow, T ight-Binding Inhibitors<br> 5.2.4.1. Theoretical Basis<br> 5.2.4.2. Captopril, Enalapril, Lisinopril, and Other Antihypertensive Drugs<br> 5.2.4.2.1. Humoral Mechanism for Hypertension<br> 5.2.4.2.2. Lead Discovery<br> 5.2.4.2.3. Lead Modification and Mechanism of Action<br> 5.2.4.2.4. Dual-Acting Drugs: Dual-Acting Enzyme Inhibitors<br> 5.2.4.3. Lovastatin (Mevinolin) and Simvastatin, Antihypercholesterolemic Drugs<br> 5.2.4.3.1. Cholesterol and Its Effects<br> 5.2.4.3.2. Lead Discovery<br> 5.2.4.3.3. Mechanism of Action<br> 5.2.4.3.4. Lead Modification<br> 5.2.4.4. Saxagliptin, a Dipeptidyl Peptidase-4 Inhibitor and Antidiabetes Drug<br> 5.2.5. Case History of Rational Drug Design of an Enzyme Inhibitor: Ritonavir<br> 5.2.5.1. Lead Discovery<br> 5.2.5.2. Lead Modification<br>5.3. Irreversible Enzyme Inhibitors<br> 5.3.1. Potential of Irreversible Inhibition<br> 5.3.2. Affinity Labeling Agents<br> 5.3.2.1. Mechanism of Action<br> 5.3.2.2. Selected Affinity Labeling Agents<br> 5.3.2.2.1. Penicillins and Cephalosporins/Cephamycins<br> 5.3.2.2.2. Aspirin<br> 5.3.3. Mechanism-Based Enzyme Inactivators<br> 5.3.3.1. Theoretical Aspects<br> 5.3.3.2. Potential Advantages in Drug Design Relative to Affinity Labeling Agents<br> 5.3.3.3. Selected Examples of Mechanism-Based Enzyme Inactivators<br> 5.3.3.3.1. Vigabatrin, an Anticonvulsant Drug<br> 5.3.3.3.2. Eflornithine, an Antiprotozoal Drug and Beyond<br> 5.3.3.3.3. Tranylcypromine, an Antidepressant Drug<br> 5.3.3.3.4. Selegiline (l-Deprenyl) and Rasagiline: Antiparkinsonian Drugs<br> 5.3.3.3.5. 5-Fluoro-2′-deoxyuridylate, Floxuridine, and 5-Fluorouracil: Antitumor Drugs<br>5.4. General References<br>5.5. Problems<br>References<br>6. DNA-Interactive Agents<br>6.1. Introduction<br> 6.1.1. Basis for DNA-Interactive Drugs<br> 6.1.2. Toxicity of DNA-Interactive Drugs<br> 6.1.3. Combination Chemotherapy<br> 6.1.4. Drug Interactions<br> 6.1.5. Drug Resistance<br>6.2. DNA Structure and Properties<br> 6.2.1. Basis for the Structure of DNA<br> 6.2.2. Base Tautomerization<br> 6.2.3. DNA Shapes<br> 6.2.4. DNA Conformations<br>6.3. Classes of Drugs that Interact with DNA<br> 6.3.1. Reversible DNA Binders<br> 6.3.1.1. External Electrostatic Binding<br> 6.3.1.2. Groove Binding<br> 6.3.1.3. Intercalation and Topoisomerase-Induced DNA Damage<br> 6.3.1.3.1. Amsacrine, an Acridine Analog<br> 6.3.1.3.2. Dactinomycin, the Parent Actinomycin Analog<br> 6.3.1.3.3. Doxorubicin (Adriamycin) and Daunorubicin (Daunomycin), Anthracycline Antitumor Antibiotics<br> 6.3.1.3.4. Bis-intercalating Agents<br> 6.3.2. DNA Alkylators<br> 6.3.2.1. Nitrogen Mustards<br> 6.3.2.1.1. Lead Discovery<br> 6.3.2.1.2. Chemistry of Alkylating Agents<br> 6.3.2.1.3. Lead Modification<br> 6.3.2.2. Ethylenimines<br> 6.3.2.3. Methanesulfonates<br> 6.3.2.4. (+)-CC-1065 and Duocarmycins<br> 6.3.2.5. Metabolically Activated Alkylating Agents<br> 6.3.2.5.1. Nitrosoureas<br> 6.3.2.5.2. Triazene Antitumor Drugs<br> 6.3.2.5.3. Mitomycin C<br> 6.3.2.5.4. Leinamycin<br> 6.3.3. DNA Strand Breakers<br> 6.3.3.1. Anthracycline Antitumor Antibiotics<br> 6.3.3.2. Bleomycin<br> 6.3.3.3. Tirapazamine<br> 6.3.3.4. Enediyne Antitumor Antibiotics<br> 6.3.3.4.1. Esperamicins and Calicheamicins<br> 6.3.3.4.2. Dynemicin A<br> 6.3.3.4.3. Neocarzinostatin (Zinostatin)<br> 6.3.3.5. Sequence Specificity for DNA-Strand Scission<br>6.4. General References<br>6.5. Problems<br>References<br>7. Drug Resistance and Drug Synergism<br>7.1. Drug Resistance<br> 7.1.1. What is Drug Resistance?<br> 7.1.2. Mechanisms of Drug Resistance<br> 7.1.2.1. Altered Target Enzyme or Receptor<br> 7.1.2.2. Overproduction of the Target Enzyme or Receptor<br> 7.1.2.3. Overproduction of the Substrate or Ligand for the Target Protein<br> 7.1.2.4. Increased Drug-Destroying Mechanisms<br> 7.1.2.5. Decreased Prodrug-Activating Mechanism<br> 7.1.2.6. Activation of New Pathways Circumventing the Drug Effect<br> 7.1.2.7. Reversal of Drug Action<br> 7.1.2.8. Altered Drug Distribution to the Site of Action<br>7.2. Drug Synergism (Drug Combination)<br> 7.2.1. What is Drug Synergism?<br> 7.2.2. Mechanisms of Drug Synergism<br> 7.2.2.1. Inhibition of a Drug-Destroying Enzyme<br> 7.2.2.2. Sequential Blocking<br> 7.2.2.3. Inhibition of Targets in Different Pathways<br> 7.2.2.4. Efflux Pump Inhibitors<br> 7.2.2.5. Use of Multiple Drugs for the Same Target<br>7.3. General References<br>7.4. Problems<br>References<br>8. Drug Metabolism<br>8.1. Introduction<br>8.2. Synthesis of Radioactive Compounds<br>8.3. Analytical Methods in Drug Metabolism<br> 8.3.1. Sample Preparation<br> 8.3.2. Separation<br> 8.3.3. Identification<br> 8.3.4. Quantification<br>8.4. Pathways for Drug Deactivation and Elimination<br> 8.4.1. Introduction<br> 8.4.2. Phase I Transformations<br> 8.4.2.1. Oxidative Reactions<br> 8.4.2.1.1. Aromatic Hydroxylation<br> 8.4.2.1.2. Alkene Epoxidation<br> 8.4.2.1.3. Oxidations of Carbons Adjacent to sp2 Centers<br> 8.4.2.1.4. Oxidation at Aliphatic and Alicyclic Carbon Atoms<br> 8.4.2.1.5. Oxidations of Carbon–Nitrogen Systems<br> 8.4.2.1.6. Oxidations of Carbon–Oxygen Systems<br> 8.4.2.1.7. Oxidations of Carbon–Sulfur Systems<br> 8.4.2.1.8. Other Oxidative Reactions<br> 8.4.2.1.9. Alcohol and Aldehyde Oxidations<br> 8.4.2.2. Reductive Reactions<br> 8.4.2.2.1. Carbonyl Reduction<br> 8.4.2.2.2. Nitro Reduction<br> 8.4.2.2.3. Azo Reduction<br> 8.4.2.2.4. Azido Reduction<br> 8.4.2.2.5. Tertiary Amine Oxide Reduction<br> 8.4.2.2.6. Reductive Dehalogenation<br> 8.4.2.3. Carboxylation Reaction<br> 8.4.2.4. Hydrolytic Reactions<br> 8.4.3. Phase II Transformations: Conjugation Reaction<br> 8.4.3.1. Introduction<br> 8.4.3.2. Glucuronic Acid Conjugation<br> 8.4.3.3. Sulfate Conjugation<br> 8.4.3.4. Amino Acid Conjugation<br> 8.4.3.5. Glutathione Conjugation<br> 8.4.3.6. Water Conjugation<br> 8.4.3.7. Acetyl Conjugation<br> 8.4.3.8. Fatty Acid and Cholesterol Conjugation<br> 8.4.3.9. Methyl Conjugation<br> 8.4.4. Toxicophores and Reactive Metabolites (RMs)<br> 8.4.5. Hard and Soft (Antedrugs) Drugs<br>8.5. General References<br>8.6. Problems<br>References<br>9. Prodrugs and Drug Delivery Systems<br>9.1. Enzyme Activation of Drugs<br> 9.1.1. Utility of Prodrugs<br> 9.1.1.1. Aqueous Solubility<br> 9.1.1.2. Absorption and Distribution<br> 9.1.1.3. Site Specificity<br> 9.1.1.4. Instability<br> 9.1.1.5. Prolonged Release<br> 9.1.1.6. Toxicity<br> 9.1.1.7. Poor Patient Acceptability<br> 9.1.1.8. Formulation Problems<br> 9.1.2. Types of Prodrugs<br>9.2. Mechanisms of Drug Inactivation<br> 9.2.1. Carrier-Linked Prodrugs<br> 9.2.1.1. Carrier Linkages for Various Functional Groups<br> 9.2.1.1.1. Alcohols, Carboxylic Acids, and Related<br> 9.2.1.1.2. Amines and Amidines<br> 9.2.1.1.3. Sulfonamides<br> 9.2.1.1.4. Carbonyl Compounds<br> 9.2.1.2. Examples of Carrier-Linked Bipartite Prodrugs<br> 9.2.1.2.1. Prodrugs for Increased Water Solubility<br> 9.2.1.2.2. Prodrugs for Improved Absorption and Distribution<br> 9.2.1.2.3. Prodrugs for Site Specificity<br> 9.2.1.2.4. Prodrugs for Stability<br> 9.2.1.2.5. Prodrugs for Slow and Prolonged Release<br> 9.2.1.2.6. Prodrugs to Minimize Toxicity<br> 9.2.1.2.7. Prodrugs to Encourage Patient Acceptance<br> 9.2.1.2.8. Prodrugs to Eliminate Formulation Problems<br> 9.2.1.3. Macromolecular Drug Carrier Systems<br> 9.2.1.3.1. General Strategy<br> 9.2.1.3.2. Synthetic Polymers<br> 9.2.1.3.3. Poly(α-Amino Acids)<br> 9.2.1.3.4. Other Macromolecular Supports<br> 9.2.1.4. Tripartite Prodrugs<br> 9.2.1.5. Mutual Prodrugs (also called Codrugs)<br> 9.2.2. Bioprecursor Prodrugs<br> 9.2.2.1. Origins<br> 9.2.2.2. Proton Activation: An Abbreviated Case History of the Discovery of Omeprazole<br> 9.2.2.3. Hydrolytic Activation<br> 9.2.2.4. Elimination Activation<br> 9.2.2.5. Oxidative Activation<br> 9.2.2.5.1. N- and O-Dealkylations<br> 9.2.2.5.2. Oxidative Deamination<br> 9.2.2.5.3. N-Oxidation<br> 9.2.2.5.4. S-Oxidation<br> 9.2.2.5.5. Aromatic Hydroxylation<br> 9.2.2.5.6. Other Oxidations<br> 9.2.2.6. Reductive Activation<br> 9.2.2.6.5. Nitro Reduction<br> 9.2.2.7. Nucleotide Activation<br> 9.2.2.8. Phosphorylation Activation<br> 9.2.2.9. Sulfation Activation<br> 9.2.2.10. Decarboxylation Activation<br>9.3. General References<br>9.4. Problems<br>References<br>Appendix<br>Index</p>