Drug Discovery and Development Notes
Sources of New Drugs
Screening of natural products (plants, animals, microbes)
Serendipity
Rational design (QSAR, structure-based design)
Screening of chemical libraries (combinatorial)
Phases of Drug Discovery & Development
Target Identification: Identifying biological targets involved in a disease.
Target Validation: Molecular and animal studies to validate targets.
Lead Discovery: Finding compounds that interact with the target from natural sources, rational drug design, or chemical libraries.
Lead Optimization: Refining compounds to improve efficacy and safety.
Preclinical Research:
In Vitro Studies: Testing compounds in cell cultures.
In Vivo Studies: Testing in animal models.
Clinical Research:
Phase I: Safety and dosage in healthy volunteers.
Phase II: Efficacy and side effects in a larger patient group.
Phase III: Large-scale testing to confirm effectiveness and monitor side effects.
FDA Review: New Drug Application (NDA) submission.
Post-Market Safety Monitoring: Phase IV monitoring in the general population.
Primary Protein Drug Targets
Receptors: Receive and transmit signals within cells.
Enzymes: Catalyze biochemical reactions.
Ion Channels: Allow ions to pass through cell membranes.
Transporters: Move molecules across cell membranes.
Approaches to Identifying Novel Drug Targets
Genomic and Proteomic Approaches: Analyze gene and protein expression.
High-Throughput Screening (HTS): Test large compound libraries.
Computational Approaches: Use AI and machine learning.
Clinical Observations: Identify biomarkers and potential targets.
Validating a Drug Target
Biological Validation: Modulating the target affects disease phenotype.
Pharmacological Validation: Use small molecules or antibodies.
Genetic Validation: RNAi or CRISPR to knock down or edit the target gene.
Functional Assays: Confirm the target's role in disease pathways.
Strategies for Sourcing New Drugs
Internal R&D: Develop drugs within the company.
Partnerships and Collaborations: Partner with other organizations.
Licensing and Acquisitions: Acquire drug candidates.
Crowdsourcing and Open Innovation: Engage the scientific community.
High-Throughput Screening (HTS)
Library Preparation: Creating a large collection of compounds.
Assay Development: Designing assays to test compound-target interaction.
Screening: Using robotics and automation.
Hit Identification: Identifying compounds with desired activity.
Validation: Confirming activity through secondary assays.
Lead Optimization Using Animal Models
Pharmacokinetic Studies: Evaluating ADME properties.
Efficacy Studies: Testing effectiveness in animal models.
Safety Studies: Assessing potential toxicity.
Iterative Refinement: Continuously improving compounds.
Pharmacodynamics in Drug Assessment
Acute Pharmacodynamics: Immediate effects, onset, and peak effect.
Chronic Pharmacodynamics: Long-term effects, tolerance, and resistance.
Safety Assessment: Monitoring for adverse effects.
Efficacy Assessment: Measuring therapeutic effect over time.
Factors Affecting Drug Absorption
Physicochemical Properties: Solubility, ionization, molecular size.
Formulation: Tablet, capsule, liquid.
Route of Administration: Oral, topical, parenteral.
Gastrointestinal Factors: pH, gastric emptying time.
Blood Flow: Increased blood flow enhances absorption.
First-Pass Metabolism: Reduces bioavailability.
Drug Distribution
Blood Flow: Organs with higher blood flow receive drugs more quickly.
Capillary Permeability: Affects drug passage through capillary walls.
Protein Binding: Drugs bound to plasma proteins are not freely distributed.
Lipid Solubility: Lipophilic drugs cross membranes easily.
Volume of Distribution (Vd): Extent of drug distribution in tissues.
Drug Elimination
Renal Excretion: Filtration by kidneys.
Biliary Excretion: Secretion into bile.
Pulmonary Excretion: Exhalation through lungs.
Sweat and Saliva: Minor routes.
Breast Milk: Affects nursing infants.
Drug Elimination Factors
Molecular Size and Charge: Affects renal filtration.
Lipid Solubility: Lipophilic drugs may undergo hepatic metabolism.
Protein Binding: Only unbound drugs are filtered.
Metabolic Stability: Drugs resistant to metabolism are excreted unchanged.
pH and Ionization: Ionized drugs are less likely to be reabsorbed.
Inter-Individual Variation in Drug Responses
Genetic Factors: Polymorphisms affect drug metabolism.
Age: Age-related changes in physiology.
Body Weight and Composition: Affect drug distribution.
Gender: Hormonal differences.
Health Status: Diseases alter pharmacokinetics.
Drug Interactions: Concurrent medications.
Environmental Factors: Diet, lifestyle, toxins.
Pharmacogenomics
Genetic Variations: Differences in genes encoding drug-metabolizing enzymes.
Predicting Drug Response: Guiding personalized treatment plans.
Dosage Adjustments: Optimizing efficacy and minimizing adverse effects.
Drug Selection: Identifying the most effective drug based on genetic profile.
Pharmacokinetic Parameters for Dosing
Absorption: Rate and extent affect drug action.
Distribution: Volume of distribution (Vd) determines loading dose.
Metabolism: Clearance (Cl) and half-life () determine dosing interval.
Elimination: Understanding kinetics helps in designing dosing regimens.
Bioavailability: Influences dosing frequency and amount.
Safety Assessment in Drug Discovery
Purpose: Ensures drugs are safe before clinical trials.
Preclinical Testing: In vitro and in vivo studies.
Risk Identification: Identifies potential adverse effects.
Regulatory Compliance: Meets safety standards.
Decision Making: Informs decisions about drug development.
Toxicity Testing
Acute Toxicity Testing: Short-term, determines immediate toxic effects and LD50.
Chronic Toxicity Testing: Long-term, evaluates cumulative toxicity and carcinogenicity.
Ames Test for Carcinogenicity
Purpose: Detects mutagenic potential.
Procedure: Uses mutant strains of Salmonella.
Interpretation: Higher revertant colonies indicate mutagenicity and potential carcinogenicity.
Clinical Trial Testing (I to IV)
Phase I: Safety, dosage, and side effects in healthy volunteers or patients; determine the drug's safety profile.
Phase II: Efficacy and safety in a larger patient group; determine the optimal dose and treatment regimen.
Phase III: Large-scale testing to confirm effectiveness, monitor side effects, and compare to standard treatments; provide the data needed for regulatory approval.
Phase IV: Post-market monitoring of long-term effects, effectiveness, and safety in the general population.
Accelerating Clinical Drug Development
Streamlined Regulatory Processes: Faster reviews and approvals.
Adaptive Trial Designs: Allow modifications based on interim results.
Use of Biomarkers: Helps in selecting the right patient populations and predicting responses to treatment.
Patient Recruitment Strategies: Effective recruitment and retention strategies speed up trial enrollment.
Technological Advancements: AI, machine learning, and digital health tools can optimize trial design and data analysis.