Pharmacology. New drug development.

1. New drug development
Dr KG Bandekar
14 Jan 2017

2. Introduction
• Developing a new drug from original idea to
the launch of a finished product is a complex
process which can take 12–15 years and cost
in excess of $1 billion.
• The idea for a target can come from a variety
of sources including academic and clinical
research.

3. Why new drug?
• A drug discovery programme is initiated
because -
 There is a disease or clinical condition for
which suitable drug is not available or
 Current drug is less effective or
 Current drug has more side effects or
 Current drug is expensive

4. Hit
• A “hit” is colloquial term used for a compound
whose biological activity exceeds a predefined,
statistically relevant threshold or a molecule with
robust dose response activity in a primary screen
and with known confirmed structure.
• “ A compound which has the desired activity in a
‘compound screen’ and whose activity is
confirmed upon retesting
(http://www.hull.ac.uk/php/chsanb/teaching )

5. Lead discovery
• Process of identifying active New chemical entities
(NCEs), which by subsequent modification/s may be
transformed into a clinically useful drug.

6. Lead compound
• A lead compound is a representative of a
compound series with sufficient potential (as
measured by potency, selectivity,
pharmacokinetics, physicochemical
properties, absence of toxicity) to progress to
a full drug development programme.

7. Lead optimization
Synthetic modification of a biologically active
compound, to fulfill physicochemical,
pharmacokinetic and toxicological properties
required for clinical usefulness.

8. Drug development phases
• Drug discovery phase
• Preclinical phase
• Clinical trial phase

9. Drug discovery phase

10. Hit and Target identification and target validation (TV) #
Assay development
High-throughput screening
Hit to lead (H2L)
Lead optimization (LO)
Preclinical drug development
Clinical drug development

11. Hit identification
• Candidate molecules are chosen on the basis
of pharmacological properties
• Approaches –
1. Random screening
2. Serendipity
3. Rational drug designing

12. Random screening
• Blind hitting procedure
• Pharmacological screening procedures on new
chemical entities (natural / synthetic)
• To explore biological activities
• Methods –
Animal models of disease
Isolated tissues
Animal behaviour studies
contd…

13. Random screening contd…
• Time consuming and expensive
• e.g.
Morphine
Digitalis
Quinidine
Cyclosporine

14. Serendipity
(Observation by chance)
• New use of old drug/its side effect is used in
treatment in other condition
e.g.
Lignocaine local anaesthetic used as
antiarrhythmic drug
Cyclophoshamide, cytotoxic drug used in
preventing transplant rejection

15. • Rational drug designing
• Two strategies
Compound-centered approach
Target-centered approach

16. Compound-centered approach
• Development from Structure activity relationship
(SAR) of known drug
e.g.
Beta blocker drugs
• Disadvantage
Difficulty in obtaining lead compounds from
natural sources as they are complex molecules –
difficult to synthesize

17. Target-centered approach
• Known biochemical or molecular targets
e.g. ACE inhibitors

18. Target identification
• Understand pathophysiology/molecular basis
of the disease
• Identification of therapeutic ‘target’ involved
(e.g gene, key enzyme, receptor, ion-channel,
nuclear receptor etc.)
contd…

19. Target identification contd…
• broad term which can be applied to a range of
biological entities which may include enzymes,
receptors, proteins, genes and RNA.
• A good target needs to be ‘druggable’.
contd…

20. Target identification contd…
• A ‘druggable’ target -
accessible to the proposed drug molecule
upon binding elicits a biological response
which may be measured both in vitro and in
vivo.
(JP Hughes1, S Rees2, SB Kalindjian3 and KL Philpott3
1MedImmune Inc, Granta Park, Cambridge, UK, 2GlaxoSmithKline, Gunnels Wood Road, Stevenage, Hertfordshire, UK,
and 3King’s College, Guy’s Campus, London, UK)

21. Target identification
1. Use of a bioinformatics approach - help in
identifying and selecting and prioritizing
potential disease targets (Yang et al., 2009)
2. Examining mRNA/protein levels to determine
whether they are expressed in disease and if
they are correlated with disease exacerbation
or progression.

22. Target identification contd.
3. Genetic associations - e.g. Familial
Alzheimer's Disease (AD) - mutations in the
amyloid precursor protein or presenilin genes
which lead to the production and deposition
in the brain of increased amounts of the
Abeta peptide, characteristic of AD (Bertram
and Tanzi, 2008).
4. Phenotypic screening .

23. Source of selection of candidate
molecule
• Published literature
• Compound library
• Screening natural products
• Structure-based design (“rational drug
design”)

24. Hit compound discovery process
• Hit - a compound which has the desired
activity in a ‘compound screen’ and whose
activity is confirmed upon retesting.

25. Hit discovery process contd…
• Screening strategies

26. Screen Description Comments
High throughput Large number of compounds are
analysed in assay generally designed
to run in plates of 384 wells and above
Large compound collections
often run by big pharma but
smaller compound banks can
also be run in either pharma
or academia which can help
reduce costs. Companies also
now trying to provide
coverage across a wide
chemical space using
computer assisted analysis to
reduce the numbers of
compounds screened.
Nuclear magnetic
resonance (NMR)
screen
Screen small compounds (fragments)
by soaking into protein targets of
known crystal or NMR structure to
look for hits with low mM activity
which can then be used as building
blocks for larger molecules
Use of NMR as a structure
determining tool

27. Physiological screen A tissue-based approach for
determination of the effects
of a drug at the tissue rather
than the cellular or
subcellular level.
Aim to more closely mimic
the complexity of tissue
rather than just looking at
single readouts. May appeal
to academic experts in
disease area to screen smaller
number of compounds to give
a more disease relevant
readout
Focused screen Compounds previously
identified as hitting specific
classes of targets (e.g. kinases)
and compounds with similar
structures
Can provide a cheaper avenue
to finding a hit molecule but
completely novel structures
may not be discovered and
there may be difficulties
obtaining a patent position in
a well-covered IP area

28. Virtual screen Docking models: interogation
of a virtual compound library
with the X-ray structure of
the protein
Can provide the starting
structures for a focused
screen without the need to
use expensive large library
screens.
Fragment screen Soak small compounds into
crystals to obtain compounds
with low mM activity which
can then be used as building
blocks for larger molecules
Can join selected fragments
together to fit into the
chemical space to increase
potency. Requires a crystal
structure to be available

29. Compound / target validation
• Develop an assay to evaluate activity of
compounds on the target
 in vitro (e.g. enzyme assay)
 in vivo (animal model)

30. • For compound - assay development
Majority of assays depend upon the creation of
stable mammalian cell lines
(Dunne et al.)

31. • Hit to lead (H2L) (= lead generation)
By high throughput screen (HTS) molecules
evaluated to identify promising lead
compounds.
Process of further evaluation of lead
compounds is called lead optimization (LO).

32. Methods for confirmation of hit
• Confirmatory testing
• Dose response curve
• Orthogonal testing
• Secondary screening
• Biophysical testing
• Hit ranking and clustering
contd…

33. Methods for confirmation of hit
contd…
• Confirmatory testing: compounds re-tested
using the same assay conditions used during
the HTS to make sure that the activity is
reproducible.
• Dose response curve: the compound is tested
over a range of concentrations to determine
the concentration that results in half maximal
binding IC50 or activity EC50
contd…

34. Contd..
• Orthogonal testing: confirmed hits are
assayed using a different assay which is
usually closer to the target physiological
condition or using a different technology.
• Secondary screening: tested in a functional
cellular assay to determine efficacy.
contd…

35. Contd…
• Biophysical testing:
Nuclear magnetic resonance (NMR),
Isothermal titration calorimetry (ITC),
Dual polarisation interferometry (DPI)
To assess whether the compound binds effectively
to the target, the kinetics, thermodynamics any
associated conformational change
• Hit ranking and clustering: Confirmed hit
compounds are then ranked according to the
various hit confirmation experiments.

36. An ideal compound cluster
• Following hit confirmation, several ‘compound
clusters’ will be chosen according to their
characteristics in the previously defined tests.
• An Ideal compound cluster must have
following properties -
contd…

37. Characteristics of an ideal compound
cluster
1. High affinity towards the target
2. Selectivity to target
3. Efficacy
4. Druglikeness (moderate molecular weight
and lipophilicity usually estimated as ClogP).
Affinity, molecular weight and lipophilicity
can be linked in single parameter such as
‘ligand efficiency’ and ‘lipophilic efficiency’.

38. Characteristics of an ideal compound
cluster contd…
6. Low to moderate binding to human serum
albumin
7. Low interference with P450 enzymes
8. Low cytotoxicity
9. Metabolic stability
10.High cell membrane permeability
11.High water solubility
contd…

39. Characteristics of an ideal compound
cluster contd..
12. Chemical stability
13. Synthetic tractability

40. Lipinski’s Rule of Five
• Lipinski proposed four parameters that define
• the “drug-likeness” of potential drug
candidates based on analysis of existing drug
molecules.
• “The Rule of Five” got its name from the cut-
off values for each of these parameters of
which
• all have values of five or a multiple of five.
Reference: C.A. Lipinski, F. Lombardo, B.W. Dominy, P.J. Feeney “Experimental andcomputational approaches to estimate solubility
and permeability in drug discovery anddevelopment settings”, Adv. Drug Delivery Rev., 1997, 23(1-3), 3-25 (available from
http://www.sciencedirect.com if on campus).

41. • The “rule of 5” - poor absorption or
permeation is more likely when:
A. There are more than 5 H-bond donors
(expressed as the sum of OHs and NHs);
B. The MW is over 500;
C. The LogP is over 5 (or MlogP is over 4.15);
D. There are more than 10 H-bond acceptors
(expressed as the sum of Ns and Os).”

42. • In rule C the parameter P is ‘water - octanol partition
coefficient’.
• A partition coefficient – ratio of equilibrium
concentration of solute in a non-polar solvent and
concentration of the same in a polar solvent
• Measure of hydrophilicity/hydrophobicity of a
molecule.
• Role - determining the bioavailability of a drug
molecule.
(MlogP is a molecule-based descriptor which describes an estimation of the log of the octanol-water partition ratio developed by
Moriguchi (Moriguchi, I. et al. Chem. Pharm Bull. 1992, 40, 127-130).
Reference: C.A. Lipinski, F. Lombardo, B.W. Dominy, P.J. Feeney “Experimental andcomputational approaches to estimate solubility
and permeability in drug discovery anddevelopment settings”, Adv. Drug Delivery Rev., 1997, 23(1-3), 3-25 (available from
http://www.sciencedirect.com if on campus).

43. Thank you!

44. New drug discovery :
Animal studies and clinical trials
Maj KG Bandekar
04 Feb 2017

45. target validation (TV)
assay development
high-throughput screening
hit to lead (H2L)
lead optimization (LO)
preclinical drug development
clinical drug development

46. Preclinical studies
• Compound tested in animals.
• To demonstrate safety of the proposed
medication.
• To estimate dose of new drug to be used in
human for first time

47. Regulatory bodies in India for animal
studies
• Institutional Animal Ethics Committee
• Committee for Purpose of Control and
Supervision of Experiments in Animals
(CPCSEA)
• Drugs & cosmetics Act,1940 and schedule Y
• Dept of Animal Husbandry,Dairying &
Fisheries, Ministry of Agriculture, India

48. Preclinical studies contd…
• Studies conducted –
A. Pharmacodynamic
B. Assessment of safety index and toxicological
studies
C. Pharmacokinetic

49. Studies conducted contd…
A. Pharmacodynamic studies
• Evaluation of proposed therapeutic effect
• If results +ve activity at cellular/receptor
level is studied
• Receptor affinity & selectivity are studied
in vitro
• Graded response assay ED50

50. B. Toxicological studies
1. Acute toxicity
Aim – to find lethal dose to 50% of animals (LD50 )
• Study at least in 2 species
• Given in graded doses to many groups of animals
• At least 2 routes , one of which is proposed in
humans

51. 2) Subacute toxicity
• Aim – to identify target organs susceptible for
toxicity
• 3 doses in 2 species and maximum tolerated dose
is identified
• Dose and duration - maximum tolerated dose for
4 weeks to 3 months – to develop pathology
• Biochemical and hematological parameters
• Animal sacrificed – study histopathological
changes

52. 3) Chronic toxicity
• For proposed drugs intended for long term
use
• 2 species – rodent and non rodent
• Duration – 1-2 years

53. • Parameters monitored during sub acute and
chronic studies
Behavioural
Biochemical
Microscopic examination

54. 4) Special toxicity
i. Effect on reproductive system
ii. Teratogenicity
iii. Carcinogenicity
iv. Mutagenicity
v. Local toxicity

55. i. Effect on reproductive system
• On rats
• Before and after mating
• To evaluate -
Fertility
Parturition and lactation
Perinatal and postnatal effect

56. ii. Teratogenicity
Rat and rabbit
• To study effect on organogenesis
• Given after mating during period of
organogenesis
• Foetus examined for abnormalities

57. iii. Carcinogenicity
• 2 species
• Dose same as used in chronic toxicity study
• For 2 years
• Hematological and histopathological
examination

58. Preclinical studies contd…
• Adhered to ‘Good Laboratory Practices’.
• Reliability and reproducibility of lab data.
• Parameters ( studies ) conducted –
A. Pharmacodynamic
B. Assessment of safety index and toxicological
studies
C. Pharmacokinetic

59. C. Pharmacokinetic
• After toxicity studies
• Many species – rat, dog, cat sometimes
monkey
• Relative bioavailability after oral and
parenteral administration

60. Animal pharmacology :
• To observe effects on various systems
CVS
RS
CNS
Endocrine system

61. Preclinical studies to clinical trial stage
• Promising results of preclinical study
• Preparation of suitable formulation of lead
compound and estimation of FIH (First in
Human Dose)

62. FIH
• Important to calculate optimum dose for
clinical trial as –
Low dose – may not response
High dose – may cause toxicity
• Different methods used to estimate FIH
contd…

63. FIH contd…
• NOEAL ( No observed adverse effect level)
method
• Pharmacokinetic guided method
• Similar drug comparison method
contd…

64. FIH contd…
NOAEL method
• It is the maximum dose that does not produce
any adverse effect in animal studies
• Human equivalent dose (HED) =
Animal NOAEL X (Wt animal ÷ Wt human )(1-b)
(where wt is kg and b = 0.67)
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4804402/#!po=32.7586

65. NOAEL method
• For example, for a newly developed drug
molecule, the NOAEL value in rat weighing
approximately 150 g is 18 mg/kg.
• HED (mg / kg = 18 × (0.15 / 60)(0.33) = 2.5 mg / kg
• Thus, for a 60 kg human, the dose is 150 mg.
• This HED value is further divided by a factor value
of 10@ the initial dose in entry into man
studies is 15 mg.
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4804402/#!po=32.7586

66. NOAEL method
@ 1/10 of the highest no-effect dose in
rodents, 1/6 of the highest no-effect dose
in dogs, or 1/3 of the highest no-effect
dose in monkeys
(Bruno G. Reigner Æ Karen Smith Blesch Estimating the starting dose for entry into
humans: principles and practice)

67. NOAEL method
• Body weight is not the only factor which
influences the scaling for dose calculation.
• Correction factor (Km) is estimated by dividing the
average body weight (kg) of species to its body
surface area (m2).
• For example, the average human body weight is
60 kg, and the body surface area is 1.62 m2.
Therefore, the Km factor for human is calculated
by dividing 60 by 1.62, which is 37
• PubMed Central, Table 1_ J Basic Clin Pharm. March 2016-May 2016; 7(2)_ 27–31.
doi_ 10.4103_0976-0105.pdf

68. NOAEL method
• HED (mg / kg) = Animal does (mg / kg) ×
(Animal Km / Human Km)
• As the Km factor for each species is constant,
the Km ratio is used to simplify calculations.
Hence, it is modified as:
• HED (mg / kg) = Animal does (mg / kg) ×
Km ratio

69. Pharmacokinetic guided FIH dose
• AUC (Area under curve) and clearance in a
species are used to estimate FIH dose.
• Dose = ( AUC Animal X CLHuman ) ÷ Correction factor
• AUC is at NOAEL
• CLHuman predicted human clearance
(Mahmood et al. and
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3326168)

70. Pharmacokinetic guided FIH dose
contd…
• However, a few assumptions are made with
pharmacokinetic-guided approaches:
1. only the parent compound is active
2. given equal plasma concentrations, the drug
shows equal pharmacological activity or
toxicity in human and nonhuman animal
species.
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3326168
contd…

71. Pharmacokinetic guided FIH dose
contd…
3. Only unbound drug is taken into
consideration : -
Interspecies differences in plasma protein
binding is not considered
 e.g drug etoposide (anti cancer drug –
unbound fraction value - 0.63, 0.52, 0.048 in
dog, rat and human respectively)
Bruno G. Reigner Æ Karen Smith Blesch Estimating the starting dose for entry into
humans: principles and practice

72. Pharmacokinetic guided FIH dose
contd…
4. Uncertainty in prediction of CLHuman using
allometric scaling
Bruno G. Reigner Æ Karen Smith Blesch Estimating the starting dose for entry into
humans: principles and practice

73. Similar drug comparison method
• When human PK/PD data are available for
similar drug
• Dose of new drug (Dosei ) is calculated from
known similar reference drug dose (Doser) :
Dose i = {Dose r X ( NOAEL i ÷ NOAEL r )} X safety
factor 1/4

74. Clinical trial phase
• “ Systematic study of a lead compound in
human subjects to generate data for
discovering or verifying the clinical claims or
pharmacological effects and adverse effects
with an aim to determine the safety and
efficacy.”

75. Clinical trial phase
• Should comply Good clinical practices (GCP)
• GCPs provide details –
Designing trial
Collection of data
Recording of information
Statistical analysis
Documentation and reporting the results

76. Clinical trial phase
Investigational new drug (IND) application by
manufacturer
Authorized drug control body of the country
(Drug Controller General, Govt. of India)

77. Information required in
IND application
• Chemical structure, source, details of purity
• Preclinical data – PK/PD, toxicological studies
with ED50 and LD50
• Dosage form, dose, route of administration
• Details of institution and infrastructure available
• Details of investigators
• Agreement from sponsors to submit annual
progress report

78. Information required in
IND application contd…
• Certification that “informed consent” will be
obtained from volunteers
• Certification that “ethics of research in human
being” will be followed
• Information to each volunteer

79. Information required in
IND application contd…
• Only after approval from regulatory body
compound can be administered to human
volunteers.

80. Ethics committee
• At institution where trial is to be conducted
• To ensure rights and welfare of participants
• Periodical review of trial and to ensure SOPs
are followed

81. Composition of ethics committee
• At least 7 members
• Member secretary and Chairperson from
outside institution
• Other 5 members – medical / nonmedical
• Members not related to trial and to sponsor
can vote/express opinion officially

82. Human/Clinical Pharmacology trials
(Phase I)
• Objectives -
 maximum tolerated dose (MTD) in humans
 pharmacodynamics
 adverse reactions
 pharmacokinetics.
• Carried out in healthy adult volunteers
• At least 2 subjects should be used on each dose.
• By investigators trained in clinical pharmacology and having
the necessary facilities to closely observe and monitor the
subjects.
• Carried out at one or two centers.
http://www.cdsco.nic.in/html/GCP1.html

83. Exploratory trials (Phase II)
• To determine
– possible therapeutic uses
– effective dose range and
– further evaluation of safety and pharmacokinetics
• 10-12 patients studied at each dose level
• Usually limited to 3-4 centers
• Carried out by clinicians specialized in the
concerned therapeutic areas and having
adequate facilities to perform the necessary
investigations

84. Confirmatory trials (Phase III)
• To obtain sufficient evidence about the efficacy
and safety in a larger number of patients
• Carried out by clinicians in the concerned
therapeutic areas, having facilities appropriate to
the protocol.
• If the drug is already approved/marketed in other
countries, phase III data should generally be
obtained on at least 100 patients distributed over
3-4 centres primarily to confirm the efficacy and
safety of the drug,

85. Confirmatory trials (Phase III) contd…
• Data on ADRs observed during clinical use of
the drug should be reported along with a
report on its efficacy in the prescribed format
• The selection of clinicians for monitoring and
supply of drug to them needs approval of the
licensing authority under Rule 21 of the Act

86. Confirmatory trials (Phase III)
contd…
New drug application
• Satisfactory results from phase 3 trial
• Application by manufacturer with all data to
be submitted to drug control authority
Enter in market with “New drug status”

87. Phase IV
• Studies performed post marketing of
the pharmaceutical product.
• Performance is monitored for few years
• Side effects, drug interactions
evaluation
• To explore new indications, new
methods of administration

88. Phase IV contd…
• Manufacturer needs to report any new
information about safety of the drug
• Periodic safety update report (PSUR) to be
submitted every 6 months for first 2 years and
annually for next 2 years
• New drug status may last for many years till
control authority is confident
Unrestricted marketing

89. Thank you!