Various Techniques and Methods for screening of new chemical entities in preclinical aspects (both invitro & invivo) for effective and safe clinical usage.

1. Preclinical evaluation of drug
Pharmacology and Toxicology
Pharmacological Screening
of Drugs
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S K Kanthlal
Amrita School of

2. Drug Development process
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3.  Preclinical trial - a laboratory test of a new drug
or a series of chemicals, usually done on animal
subjects, to see if the hoped-for treatment really
works and if it is safe to test on humans.
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4. File for approval as an Investigational New Drug
(IND)5
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Establish Effective and Toxic Doses
Screen the Drug in the Assay
Develop a Bioassay
Indentify a Drug Target
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5. Get idea for drug target
Develop a bioassay
Screen chemical compounds in assay
Establish effective and toxic amounts
File for approval as an Investigational New Drug
(IND) (leads to clinical trials)
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6. Screening of drugs
A thorough investigation to
 Get pharmacological activity of new/chemically undefined
substances
 Investigate the functions of endogenous mediators
 Measure/ define the toxicity and/or unwanted actions
• A test or group of test believed to permit
the detection of physiological activityScanning
• To reduce the uncertainty
of scanning
Evaluation
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7. Programmed
Blind
Simple
Is the substance active?
(1/2 similar testing)
Is there any
Biological activity ?
In what ways compound(s) acts ?
Main activity ?.,,,,, Subsidiary activity?
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8. SIMPLE SCREENING
◦ One or 2 similar test to find substances having a
particular property
◦ To find the substance are active in a single way
◦ No need for battery/ series of test
◦ Inexpensive and less time consuming
◦ Select only suitable method
◦ Not Sufficiently accuracy in results
Eg. Hypoglycemic testing: Ability of a compound to
diminish the Blood glucose levels.
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9. BLIND SCREENING
◦ Only for the series of new chemical substances with no
prior pharmacological history.
◦ New chemical entity or isolated naturals
◦ Provides a road towards fields of activity if they exists
◦ To demonstrate whether new group of substances is worthy
for further attention?
◦ Point out the most potent chemical with interesting
pharmacological activity
◦ Requires planning and skillful execution of test (Nature,
economical, time & money)
◦ Toxicological pathway is essential for every library of
compounds
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10. PROGRAMMED SCREENING
◦ Provide information “what compounds are active in what
ways?”
◦ A new drug of specific type (known) and/or series of
chemicals is to be investigated for some particular
pharmacological activity.
 Eg. System or organ specific
◦ A series of testing program is required to provide
information on the compounds on specific targets
◦ Explores main activity and subsidiary activity
◦ Potency can be compared with known compounds which
lead the investigator to proceed or to terminate.
◦ More limited than blind, precision is expected
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11. Preclinical Studies
Invitro Invivo
Pharmacological
Studies
Toxicological
studies
SafetyEfficacy
Dose conversion
Determination of
starting dose
Receptor Characterization
 Receptor binding assay
Enzyme inhibition
20 Messenger analysis
Cytotoxic activity
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12. METHODS OF SCREENING
• Invitro :
▫ Experimental process in a given procedure which is mainly
done outside the body in a controlled condition
 Activity assays (screen the activity)
 Bioassays (define the molecular mechanism)
 Toxicity assays (Toxicity of chemicals)
Types: Biological assay using isolated tissues/organs
(skeletal/smooth muscles, aorta, heart etc.,)
Chemical Assay using regents
Cell culture studies
Antioxidant assays
Xanthine oxidase activity
Antiglycation activity
DNA, protein, RNA level
assays
Immunological assays
Toxicity(cyto) assays
Immunological assays
Cancer cell line studies
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13. • Exvivo:
▫ Experimental process which is performed outside the living
body in an ‘artificial invivo environment’
▫ This usually lasting up to 24 hrs
• In vivo
▫ Experimental process which is performed in the living body
using laboratory animals
• Insilico
▫ Process which is performed on computer or via computer
simulator
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14.  Techniques employed for the determination of the potency of
chemical and biological agents like drugs, hormones, ions,
etc., by means of biological indicators using whole animals,
isolated organs and tissues or using cell lines
Biological Indicators:
Body temperature
Blood glucose level
Behavioral responses
Serum parameters
Contraction/relaxation
Growth/inhibition of cells
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15.  STEP I
◦ Toxicological assessment of chemicals
◦ LD50 estimation
Using Acute/sub-acute, chronic etc., studies
 STEP II (
◦ Evaluation of 10 & 20Pharmacological activity
◦ Animal models of induced disease and injury
 STEP III
◦ ADME Studies
 Absorption studies
 Tissue/organ/fluid conc. estimation
 Histopathological studies
 Serum estimation of biological indicators for drug & metabolites
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Factors:
Species
Strains
Sex
Age
Disease
Induction
Environmental

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•In Vitro Toxicology
•In Vivo Toxicology
AT PRESANT

17. What is Toxicology?
 Toxicology is the study of the adverse /unwanted
effects of chemical, physical, or biological agents on
people, animals, and the environment
Why Do Toxicology Testing?
 Need to prove new drugs are safe:
 Before first administration to humans
 Before later clinical trials 17

18. InVitroToxicology In vitro toxicology
 The bridge exists between new drug discovery and drug
development.
 Provide information on mechanism(s) of action of a drug
 Provides an early indication of the potential for some kinds of
toxic effects, allowing a decision to terminate or to proceed
further.
In vitro methods are widely used for:
 Screening and ranking chemicals
 Get a platform for animal studies for physiological actions
 Studying cell, tissue, or target specific effects
 Improve subsequent study design
Advs & Disadvs.
 Faster than in vivo studies
 Less expensive to run
 Less predictive of toxicity in intact organisms
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19.  Cytotoxicity
◦ Toxicity to cells
◦ Liver cells, blood cells, bacteria, fungi, yeast
 Structural – e.g., effects on membrane integrity
 Functional – e.g., effects on mitochondrial function
 Cell proliferation – decreases or increases
 Protein binding
◦ Receptor/enzyme interactions
 CYP inhibition/induction
◦ Using hepatic enzymatic reaction
 Membrane permeability
 Immunotoxicity
◦ Drug induced cytokine, histamine release etc.,
 Metabolism and Kinetics
◦ Information about pathways and metabolites (toxic nature)
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20. Invivo Toxicological studies
Expected results should, at a minimum:
 Establish a safe starting dose for clinical studies
 To determine the dose levels for future prospects
 Provide information on a drug-therapy regimen that
would produce the least toxicity
 Assess target organ toxicity and its reversibility
 Provide insight into biomarkers for clinical
monitoring
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21. Studies to be performed before
clinical trials
 Pharmacodynamics
 Pharmacokinetics
 Single dose toxicity in two species
 Repeated dose toxicity in two species,
 Chronic Toxicity/Carcinogenicity
 Safety Pharmacology
 Local tolerance
 Genotoxicity
 Reproductive Toxicity/ Teratogenicity study
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