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PREFACE
Drug Discovery
Abstract
INTRODUCTION
Introduction to Drug Discovery
Target Identification
Lead Generation
Lead Optimization
Preclinical Development
Clinical Development
Regulatory Approval
Post-Marketing Surveillance
Challenges and Advancements
Target and Lead Identification: Unveiling the Path to Therapeutic Success
Target Identification
Genetic Approaches
Proteomic Approaches
Chemical Biology Approaches
Lead Identification
High-Throughput Screening (HTS)
Virtual Screening
Natural Product Screening
Challenges and Advancements
Drug Solubility: Unlocking Formulation Challenges for Effective Therapeutics
Importance of Drug Solubility
Bioavailability
Formulation Development
Drug Delivery Systems
Factors Affecting Drug Solubility
Drug Properties
pH and Ionization
Solvent Selection
Strategies to Enhance Drug Solubility
Salt Formation
Particle Size Reduction
Solubilization Techniques
Prodrug Design
Drug Likeness: Guiding Principles in Drug Design and Discovery
Importance of Drug Likeness
Factors Influencing Drug Likeness
Physicochemical Properties
Structural Characteristics
Pharmacokinetic Considerations
Drug Likeness Evaluation Tools
Balancing Drug Likeness and Target Specificity
Drug Databases: Empowering Drug Discovery and Knowledge Integration
Importance of Drug Databases
Drug Discovery
Drug Development
Clinical Decision-Making
Key Components of Drug Databases
Chemical Information
Pharmacological Data
ADME Profiles
Safety and Toxicity Information
Clinical Usage and Guidelines
Impact of Drug Databases
Accelerating Drug Discovery
Enhancing Drug Safety and Efficacy
Facilitating Knowledge Integration
Supporting Personalized Medicine
Drug ADME: Understanding the Journey of a Drug in the Body
Absorption
Distribution
Metabolism
Excretion
Implications for Drug Development
Bioavailability and Efficacy
Safety and Toxicity
Drug-Drug Interactions
Conclusion
References
Molecular Dynamics in Computer-Aided Drug Discovery: Unveiling Insights into Biomolecular Interactions
Abstract
Introduction
Principles of Molecular Dynamics Simulations
Newton's equations of motion
Newton's First Law of Motion (Law of Inertia)
Newton's Second Law of Motion
Newton's Third Law of Motion
Force Fields and Potential Energy Functions
Integration Algorithms
Ensemble Methods and Sampling Techniques
Methodologies and Techniques
System Setup and Preparation
System Definition
Force Field Selection
Initial Conditions
Simulation Box and Boundary Conditions
Solvent or Environment Setup
Energy Minimization and Equilibration
Solvent Models and Boundary Conditions
Solvent Models
Boundary Conditions
Treatment of Long-range Electrostatics
Force Field Parameterization and Validation
Force Field Parameterization
Force Field Validation
Applications of Molecular Dynamics in Drug Discovery
Protein-ligand Binding and Stability
Protein-protein Interactions
System Setup
Force Field Selection
Simulation Protocol
Binding Mechanism and Recognition
Allosteric Effects and Conformational Changes
Role of Water and Solvent Effects
Protein Dynamics and Conformational Changes
Membrane Protein Simulations
Membrane Model Selection
Force Field Selection
System Setup
Simulation Protocol
Lipid Dynamics and Protein-Lipid Interactions
Protein Conformational Changes and Function
Membrane Protein Dynamics and Allosteric Communication
Solvent Effects and Drug Permeability
Solvent Representation
Drug-Solvent Interactions
Membrane Permeability Studies
Free Energy Calculations
Transporter and Channel Interactions
Solvent Effects on Drug Binding
Enhanced Sampling Methods
Importance of Enhanced Sampling Techniques
Replica Exchange Molecular Dynamics (REMD)
Meta-dynamics and Biasing Potentials
Markov State Models (MSMs)
Allosteric Modulation and Binding Site Identification
Allosteric Modulation of Protein Function
Allosteric Site Identification and Characterization
Drug Design Targeting Allosteric Sites
Drug Optimization and Binding Free Energy Calculation
Free Energy Calculations in Drug Discovery
Ligand Binding Affinity Estimation
Free Energy Perturbation (FEP) and Thermodynamic Integration (TI)
Challenges and Limitations of Binding Free Energy Calculations
Drug Resistance and Target Flexibility
Understanding Drug Resistance Mechanisms
Simulating Drug-resistant Mutants
Flexibility in Target Proteins and its Implications
Flexible Docking and Hybrid Approaches
Integration with Experimental Techniques
MD Simulations and Experimental Validation
NMR Spectroscopy and MD Simulations
X-ray Crystallography and MD Simulations
Advancements and Future Directions
Accelerating MD Simulations with GPU Computing
Hybrid Methods: QM/MM and MD Simulations
Challenges and Outlook
Computational Cost and Scalability
Accuracy and Limitations of Force Fields
Conclusion
References
Pharmacophore Modelling and Virtual Screening
Abstract
Introduction
Pharmacophore Modelling: Unveiling the Key to Drug Design
Understanding Pharmacophore Modelling
Process and Techniques
Significance in Drug Design
Applications in the Pharmaceutical Industry
Recent Advancements
Virtual Screening
Principles of Virtual Screening
Virtual Screening Approaches
Applications of Virtual Screening in Drug Discovery
Challenges in Virtual Screening
Integration of Virtual Screening with Experimental Approaches
Advancements in Virtual Screening
Future Perspectives
QSAR Methods in Computer-Aided Drug Discovery
Principles of QSAR
Development of QSAR Models
Applications of QSAR in Drug Discovery
Challenges and Limitations
Future Perspectives
3D QSAR: Enhancing Drug Discovery through Three-Dimensional Quantitative Structure-Activity Relationship Analysis
Importance of 3D QSAR
Structure-Activity Relationship Exploration
Ligand-Based Drug Design
Scaffold Hopping and Analog Synthesis
Principles of 3D QSAR
Molecular Alignment
Grid Generation
Descriptor Calculation
Statistical Analysis
Applications of 3D QSAR
Lead Optimization
Virtual Screening
Toxicity Prediction
Force Fields in Computer-Aided Drug Discovery: Unleashing the Power of Molecular Simulations
Understanding Force Fields
Force Field Components
Parameterization and Validation
Applications in Computer-Aided Drug Discovery
Molecular Docking
Molecular Dynamics Simulations
Solvation and Solvent Effects
Quantum Mechanical/Molecular Mechanical (QM/MM) Simulations
Challenges and Future Perspectives
Conclusion
References
Molecular Docking in Computer-Aided Drug Discovery: A Powerful Tool for Targeted Therapeutics
Abstract
Introduction
Principles of Molecular Docking
Protein-ligand Interaction
Docking Algorithms
Rigid-body Docking
Flexible Docking
Ligand-Based Docking
Structure-Based Docking
Hybrid Docking
Scoring Functions
Scoring Functions can be Categorized into Two Main Types
Empirical Scoring Functions
Van der Waals Interactions
Electrostatic Interactions
Hydrogen Bonding
Hydrophobic Interactions
Desolvation Energy
Physics-Based Scoring Functions
Validation and Accuracy Assessment
Experimental Validation
Redocking and Cross-docking
Decoy Set Analysis
Scoring Function Analysis
Blind Docking and Prospective Studies
Community-wide Challenges and Benchmarks
Methodologies and Techniques
Structure-based Drug Design
Target Selection
Protein Structure Determination
Ligand Design and Selection
Molecular Docking
Analysis and Optimization
Experimental Validation
Iterative Design
Ligand-based Drug Design
Activity Data Collection
Ligand Representation
Similarity Searching
Pharmacophore Modeling
Quantitative Structure-Activity Relationship (QSAR)
Molecular Docking
Optimization and Synthesis
Experimental Validation
Virtual Screening
Target Selection
Preparation of Protein and Ligand
Docking Algorithm Selection
Compound Library Preparation
Virtual Screening
Scoring and Ranking
Hit Selection
Experimental Validation
Applications of Molecular Docking
Target Identification and Validation
Target Identification
Genomics and Proteomics
Data Mining and Literature Review
Biological Assays
Molecular Docking
Target Validation
Binding Assays
Cellular Assays
Animal Models
Clinical Studies
Lead Optimization and Hit-to-Lead Development
Hit-to-Lead Development
Structural Analysis
Lead Identification
Structure-Guided Design
Synthesis and Testing
Lead Optimization
Iterative Design and Synthesis
Molecular Docking for Optimization
ADME/Toxicity Profiling
Clinical Candidate Selection
De Novo Drug Design
Target Selection
Virtual Library Generation
Compound Generation
Conformational Sampling
Molecular Docking
Scoring and Selection
Lead Optimization
Experimental Validation
Advancements in Molecular Docking
Enhanced Scoring Functions
Force Field-Based Energy Terms
Solvation Models
Scoring Terms for Protein Flexibility
Knowledge-Based Potentials
Empirical Scoring Functions
Water-Mediated Interactions
Consensus Scoring
Free Energy Perturbation (FEP)
Fragment-based Docking
Fragment Library Generation
Fragment Screening
Scoring and Ranking
Fragment Growing/Linking
Iterative Optimization
Lead Optimization
Experimental Validation
Solvent Effects and Explicit Water Modeling
Solvent Effects in Molecular Docking:
Solvation Energy
Hydration Shell
Desolvation Penalty
Explicit Water Modeling in Molecular Docking:
Water Placement
Water-Mediated Interactions
Solvation Energy Calculation
Flexibility and Dynamics
Challenges and Limitations
Future Perspectives and Outlook
Integration of Machine Learning and AI
Multi-Target Docking and Polypharmacology
Incorporation of Dynamics and Flexibility
Improved Scoring Functions and Binding Free Energy Calculations
Integration of Structural and Experimental Data
Application to New Therapeutic Areas and Target Classes
Combination with Experimental High-Throughput Screening
Conclusion
References
The Use of Density Functional Theory in Computer-Aided Drug Discovery
Abstract
Introduction
Principles of Density Functional Theory
Electron Density
Hohenberg-Kohn Theorems
Kohn-Sham Equations
Exchange-Correlation Functional
Approximations
Energy and Property Calculations
Applications
Application of Density Functional Theory in Drug Discovery
Molecular Structure and Conformation
Electronic Properties and Spectroscopy
Reaction Energetics and Mechanisms
Binding Affinity and Drug-Receptor Interactions
Solvation Effects
Quantum Mechanical/Molecular Mechanical (QM/MM) Simulations
Virtual Screening and Drug Design
Force Field Parameterization and Validation Using Functional Density Theory
Force Fields in Molecular Dynamics
Limitations of Force Fields
Parameterization Process
Non-Bonded Parameters
Bonded Parameters
Validation
Iterative Refinement
Transferability and Limitations
Solvent Effects and Continuum Solvation Models
Solvent Effects in DFT
Continuum Solvation Models
Dielectric Continuum Models
Polarizable Continuum Models
Solvent Accessible Surface Area (SASA)
Implicit vs. Explicit Solvent Models
Applications
Challenges and Future Directions in DFT for Drug Discovery
Accuracy of Exchange-Correlation Functionals
Treatment of Solvation Effects
Time-Scale Limitations
Treatment of Excited States
Incorporating Quantum Effects
Data Availability and Integration
High-Throughput Screening and Virtual Screening
Multiscale Modeling and Integration
Conclusion
References
Software in Computer-Aided Drug Discovery: Empowering Scientific Exploration and Innovation
Abstract
Introduction
Molecular Modeling and Visualization Software
Schrödinger Suite
PyMOL
Discovery Studio
Molecular Docking and Virtual Screening Software
Autodock
Gold (Genetic Optimization for Ligand Docking)
Dock
Molecular Dynamics Simulation Software
Gromacs
Amber (Assisted Model Building with Energy Refinement)
Namd
Cheminformatics and Drug Design Software
RDKit
Openeye
Moe (Molecular Operating Environment)
Data Analysis and Machine Learning Software
KNIME
TensorFlow
ChemMine Tools
Hardware in Computer-Aided Drug Discovery: Empowering Computational Exploration and Accelerating Drug Development
High-Performance Computing (HPC) Systems
Multi-Core Processors
Distributed Memory
Cluster Computing
Graphics Processing Units (GPUs) and Field-Programmable Gate Arrays (FPGAs)
GPUs
FPGAs
Cloud Computing Platforms
Scalability
Accessibility
Cost Efficiency
Big Data Storage and Management
High-Capacity Storage Systems
Data Transfer and Network Infrastructure
The Role of Artificial Intelligence in Computer-Aided Drug Discovery: Revolutionizing Therapeutic Development
Data Analysis and Integration
Predictive Modeling and Virtual Screening
De Novo Drug Design
Drug Repurposing and Combination Therapy
Conclusion
References
Success Stories in Computer-Aided Drug Discovery
Abstract
Introduction
Development of Imatinib for Chronic Myeloid Leukemia
Target Identification
Virtual Screening
Structure-Based Drug Design
Pharmacophore Analysis
Clinical Validation and Success
Development of Pembrolizumab for Cancer Immunotherapy
Target Identification
Virtual Screening and Ligand Design
Molecular Docking and Binding Affinity Optimization
Predictive Modeling and Clinical Validation
Clinical Success and Impact
Development of Sovaldi for Hepatitis C
Target Identification
Structure-Based Drug Design
Virtual Screening and Drug Optimization
Pharmacokinetic Modeling
Clinical Success and Impact
Development of Osimertinib for Non-Small Cell Lung Cancer
Target Identification
Structure-Based Drug Design
Virtual Screening and Hit Optimization
Pharmacokinetic and Pharmacodynamic Modeling
Clinical Success and Impact
Example of a Veterinary Drug Developed with Computer-Aided Drug Discovery, Galliprant (laropiprant), Used to Treat Pain and Inflammation Associated with Osteoarthritis in Dogs
Virtual Screening and Ligand Design
Molecular Docking and Binding Analysis
Pharmacokinetic Modeling
Safety and Toxicity Prediction
The Role of Computer-Aided Drug Discovery Techniques in the COVID-19 Pandemic: Accelerating Therapeutic Development and Understanding Viral Mechanisms
Virtual Screening and Repurposing of Existing Drugs
Structure-Based Drug Design
Molecular Dynamics Simulations
Artificial Intelligence and Machine Learning
Conclusion
References
The Future of Computer-Aided Drug Discovery Methods: Advancements and Opportunities
Abstract
Introduction
Integration of Artificial Intelligence (AI)
High-Performance Computing (HPC)
Integration of Multi-Omics Data
Repurposing and Drug Combination Strategies
Quantum Computing
Integration of Blockchain Technology
Nanotechnology and Drug Delivery Systems
Conclusion
References
Computer-Aided Drug Discovery Methods: A Brief Introduction
Authored by
Manos C. Vlasiou
School of Veterinary Medicine
University of Nicosia
Nicosia, Cyprus
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PREFACE
In the ever-evolving landscape of pharmaceutical research and development, the convergence of computational science and medicinal chemistry has ushered in a new era of innovation: Computer-Aided Drug Discovery (CADD). This exciting and rapidly advancing field represents a paradigm shift in identifying, designing, and optimizing novel therapeutics.
The journey from molecular target identification to clinical drug candidates is intricate and challenging, marked by complicated molecular interactions, complex biological systems, and an unyielding quest for efficacy and safety. In this intricate relationship between science and technology, CADD emerges as a guiding light, illuminating previously obscured pathways and accelerating drug discovery.
In this comprehensive volume, we embark on an exploration of the multifaceted world of Computer-Aided Drug Discovery. The chapters herein span a spectrum of methodologies, each contributing to our understanding of molecular interactions, predictive modeling, and rational design. From virtual screening and molecular docking to molecular dynamics simulations and machine learning algorithms, the tools at our disposal are diverse and robust.
Through the pages of this book, we delve into the intricacies of ligand-receptor interactions, binding free energy calculations, and the role of quantum mechanics in drug discovery. We examine the nuances of structure-based and ligand-based approaches while uncovering the potential of artificial intelligence and deep learning in unraveling the mysteries of molecular recognition.
However, as we navigate this fascinating domain, it is crucial to remember that CADD is not a panacea but a complementary force that enhances the ingenuity of medicinal chemists and biologists. The synergy between computational methods and experimental validation is the cornerstone of successful drug discovery.
As we venture further into the frontiers of drug discovery, the collective efforts of researchers, practitioners, and pioneers in CADD are reshaping the landscape of pharmaceutical science. The promise of more efficient, cost-effective, and targeted therapies is becoming a reality driven by the fusion of human intellect and computational power.
This book serves as both a reference and an inspiration, guiding us toward a future where Computer-Aided Drug Discovery is an essential pillar of modern healthcare, enhancing our ability to alleviate suffering and improve the human condition.
Onward to the future of drug discovery.
Manos C. Vlasiou
School of Veterinary Medicine
University of Nicosia
Nicosia, Cyprus
Drug Discovery
Manos C. Vlasiou1
Abstract
Drug discovery is a complex process involving target identification, lead generation, and clinical development. Recent breakthroughs in genomics and AI-driven approaches have expedited target identification. Rational drug design and advanced chemistry techniques have improved lead compound optimization—preclinical testing benefits from organ-on-a-chip systems and 3D cell culture models. Clinical development is enhanced by personalized medicine and innovative trial designs. Across all stages, big data, machine learning, and AI play pivotal roles in data analysis and candidate selection. Collaboration between academia, industry, and regulators fosters a more efficient drug development ecosystem. These advancements offer promising prospects for tackling challenging diseases and enhancing global healthcare.
Keywords: Computer-aided drug discovery, Drug discovery methods, Drug-likeness, Solubility, Target identification.
INTRODUCTION
Drug discovery is a complex and dynamic process involving identifying and developing novel therapeutic agents to combat human diseases. It encompasses a multidisciplinary approach, integrating biology, chemistry, pharmacology, and computational sciences [1]. Here, we explore the stages of drug discovery, including target identification, lead generation, lead optimization, and preclinical and clinical development, and highlight the challenges and advancements in this field. Target and lead identification are critical stages in drug discovery, laying the foundation for developing novel therapeutic agents. Target identification involves identifying and validating a specific molecule or pathway implicated in a disease.
In contrast, lead identification focuses on discovering compounds that interact with the target and show potential therapeutic activity [2]. We will now explore the methodologies, challenges, and advancements in target and lead identification, highlighting their importance in pursuing effective treatments.
Drug solubility is crucial in pharmaceutical development, directly influencing drug bioavailability, formulation, and therapeutic efficacy. Poor solubility remains
a significant challenge in drug discovery and formulation, limiting the successful delivery of many potential therapeutic agents. We will shed some light on the significance of drug solubility, the factors affecting solubility, and the strategies employed to enhance solubility and improve drug formulations.
Drug likeness is a concept that serves as a guiding principle in drug design and discovery, aiming to identify compounds with properties favourable for their development into safe and effective medications. It involves the evaluation of a molecule's physicochemical and structural characteristics against a set of desirable attributes to assess its potential as a drug candidate [3]. The significance of drug-likeness, the factors influencing it, and its role in optimizing the success of drug development will be discussed.
Drug databases are pivotal in pharmaceutical research and development, providing comprehensive and structured repositories of drug-related information [4]. They are invaluable resources for drug discovery, development, and clinical decision-making.
ADME is an acronym that represents the four essential processes a drug undergoes within the body: absorption, distribution, metabolism, and excretion [5]. These processes collectively determine a drug's pharmacokinetic profile, influencing its bioavailability, distribution to target tissues, metabolism, and elimination. We will also explore the significance of the drug ADME, the critical processes involved, and their implications for drug development and therapeutic outcomes [6].
Introduction to Drug Discovery
Target Identification
The first crucial step in drug discovery is identifying a target, a specific protein, enzyme, receptor, or genetic component involved in a disease pathway. Advances in genomics, proteomics, and bioinformatics have revolutionized target identification, enabling researchers to uncover new therapeutic targets and understand disease mechanisms at a molecular level [7]. Target validation, utilizing various experimental and computational techniques, is essential to establish the significance and feasibility of the target for drug intervention.
Lead Generation
Once a target is identified, the next step is to find lead compounds that interact with the target and exhibit potential therapeutic activity. Lead generation involves screening large libraries of compounds, either through high-throughput screening (HTS) or virtual screening methods. HTS involves testing thousands or even millions of combinations for their ability to bind to the target and elicit the desired biological response [8]. Virtual screening, on the other hand, employs computational techniques to screen and prioritize compounds based on their predicted interactions with the target.
Lead Optimization
After obtaining promising lead compounds, the focus shifts to lead optimization, which aims to enhance the compounds' potency, selectivity, and pharmacokinetic properties. Medicinal chemists modify the chemical structure of lead compounds through iterative rounds of synthesis, testing, and structure-activity relationship (SAR) studies [9]. The goal is to optimize the balance between efficacy, safety, and drug-like properties, guided by insights gained from molecular modelling, QSAR methods, and computational chemistry tools.
Preclinical Development
In the preclinical development stage, lead compounds undergo rigorous testing to assess their safety, efficacy, and pharmacokinetic profiles before progressing to clinical trials. Preclinical studies involve in vitro experiments, animal models, and toxicology assessments to evaluate the compound's pharmacological effects, potential side effects, and overall toxicity profile [10]. These studies provide crucial data for determining the candidate compound's dosage range, formulation, and possible therapeutic indications.
Clinical Development
If a lead compound successfully passes the preclinical evaluation, it progresses to clinical development, which involves testing the combination in humans through clinical trials. Clinical trials are conducted in phases, starting with Phase I, which focuses on safety and dosage determination, followed by Phase II and Phase III trials that assess efficacy, side effects, and comparative effectiveness against existing treatments [11]. These trials involve large patient populations and are tightly regulated to ensure patient safety and ethical conduct.
Regulatory Approval
The drug development process enters the regulatory phase upon completion of clinical trials. Pharmaceutical companies compile extensive data from preclinical and clinical studies and information on manufacturing processes, quality control, and safety measures to submit a New Drug Application (NDA) or equivalent to regulatory authorities such as the Food and Drug Administration (FDA) [12]. Regulatory agencies review the data and decide on the drug's approval, labelling, and post-marketing surveillance requirements.
Post-Marketing Surveillance
Once a drug is approved and enters the market, post-marketing surveillance becomes crucial to monitor the drug's safety and effectiveness in real-world patient populations. Adverse events and unexpected side effects may surface, necessitating continuous monitoring, pharmacovigilance, and periodic reassessment of the drug's risk-benefit profile. Post-marketing studies and ongoing clinical trials further contribute to understanding the drug's long-term effects and potential new indications.
Challenges and Advancements
Drug discovery faces numerous challenges, including a high failure rate, lengthy timelines, and escalating costs. Researchers constantly strive to overcome these challenges through technological advancements, automation, data analysis, and collaboration [13]. Emerging fields such as pharmacogenomics, artificial intelligence, and personalized medicine offer new avenues for targeted and efficient drug discovery [14]. Additionally, repurposing existing drugs and exploring natural products and biologics provide alternative strategies for identifying therapeutics.
Target and Lead Identification: Unveiling the Path to Therapeutic Success
Target Identification
Target identification involves identifying and validating a specific molecule or pathway that plays a crucial role in the development or progression of a disease. This stage relies on a multidisciplinary approach, integrating genomics, proteomics, bioinformatics, and systems biology. Several strategies are employed in target identification:
Genetic Approaches
Genetic approaches involve studying genetic variations and mutations associated with diseases. Genome-wide association studies (GWAS), next-generation sequencing, and functional genomics provide insights into disease-related genes and their impact on disease pathogenesis. By focusing on genes directly implicated in disease phenotypes, researchers can identify potential drug targets through these approaches.
Proteomic Approaches
Proteomic approaches aim to understand the functions and interactions of proteins within cellular pathways. Techniques such as mass spectrometry, protein-protein interaction studies, and protein profiling enable the identification of disease-associated proteins [15]. Researchers can uncover potential drug targets and gain insights into disease mechanisms by investigating protein expression patterns and post-translational modifications.
Chemical Biology Approaches
Chemical biology approaches make use of small molecules, probes, and chemical libraries to study biological systems. Chemical screenings, high-throughput (HTS), and fragment-based screening identify molecules interacting with specific targets or pathways [16]. These approaches can reveal new drug targets by identifying compounds that modulate disease-relevant phenotypes or protein activities.
Lead Identification