3. Preclinical Safety & Toxicity Testing
Aims at discovering complications or sequelae
arising from the pharmacological actions of
drug and any unexpected side-effects.
4. Primary Goals
Estimate safe starting dose for clinical studies &
subsequent dose escalation schemes in humans.
Identify potential target organs for toxicity and study
whether such toxicity is reversible.
Assess dose dependence & relationship to exposure
Assess hazards that cannot be evaluated in clinical trials
(e.g. carcinogenicity and teratogenicity)
Identify hazards and estimate safe dose range
5. Necessity of toxicity studies
Completely novel compound of unique action under
consideration
Any chemical modification made to a known drug
Formulations of a compound are considered
( Separately as well as formulated form)
Novel combination of drugs made available as a single
formulation
Veterinary drugs → if treatment is given to animals
intended for human food
7. Materials: Animals
Species:
Species difference → single largest difficulty in
interpretation of toxicity studies
Species →health, behaviour, endemic disease and
reaction to well studied toxic agent is familiar
Two different species(Rodent & Non Rodent) used
Should differ phylogenetically as widely as possible
8. Materials: Animals
Species:
Species in which test material is pharmacologically active
due to presence of receptor should be used
Ex. Avoid dogs for studying toxic effects of
sulphonamides, monkeys are better
Strains:
Use either animals derived from random breeding in
a closed colony or hybrids of two inbred lines
9. Materials: Animals
Number, age and sex:
Should be sufficient
Long term experiments i.e. Carcinogen testing, large
number may be necessary to detect relatively low
incidence of the reactions
Young immature animals are preferred generally → rapid
growth, but for detection of actions on endocrine and
reproductive systems, sexually mature animals are
required
Should include groups of both males and females
10. Route / Frequency of administration
Two routes to be used, one should be which is
intended for clinical use
Aim should be to maintain the appropriate blood and
tissue level of the compound under consideration for
test duration
11. Duration
Depends on type of the test (acute, sub-acute, chronic)
All the important toxic effects of test substances can
probably predicted from experiments lasting no more
than three months
In the absence of any rational basis for choosing a period,
a duration of twice the maximum exposure likely for
the human beings is convenient guide. 2 yrs. max
15. Single-dose (Acute) Toxicity Studies
Dose – toxicity relationship
Specific toxic effects
Mode of toxic action
Median Lethal dose (LD 50)
Route dependent toxicity
Sex dependent toxicity
16. Single-dose (Acute) Toxicity Studies
Rodent species (mice and rats)
Use the same route as intended for humans
Use at least one more route in one of the species. This
Ensures systemic absorption of the drug
(unless the intended route in humans is only intravenous)
Recommended limit for oral dosing : Higher value of
either
2000 mg/kg or
10 times the normal dose that is intended in humans
17. Single-dose (Acute) Toxicity Studies
At least 5 animals / sex / group
At least 4 graded doses (4 dose-groups)
Observation for toxic effects (if any) : 14 days
Obsevation for mortality :
7 days [parenteral administration]
14 days [oral administration]
18. Up and down procedure (Guideline 425)
(End point: mortality)
Preliminary study : 1 animal per step
Starting dose : just below expected LD 50
Dose stepped up / down by a factor of 3.2
Continued till outcome reversed, i.e. mortality
<=> survival
Reduction of the number of animals, use of single sex
Preliminary studies, followed by main test (Limit test)
Fixed dose procedure (Guideline 420)
(End point: Evident toxicity)
Sighting study : 1 animal per step
Starting dose : expecting some toxicity
Fixed doses of 5, 50, 300 and 2000 mg/kg
Dose stepped up / down till end-point achieved
Acute toxic class (Guideline 423)
(End point: mortality)
3 animals of one sex / step
Initial dose: expecting mortality in some
animals
Fixed doses of 5, 50, 300 and 2000 mg/kg
Dose stepped up / down till end point achieved
Modifications
(OECD guidelines: 420, 423, 425; yr 2000)
19. Other parameters :
Symptoms, signs and mode of death
LD 10 and LD 50 values, preferably with 95 % CI
Genetic effects if any
Establish the:
Minimum lethal dose (MLD)
Maximum tolerated dose (MTD)
Target organ of toxicity (if possible)
20. Cytotoxic anticancer agents
MTD determined first in Mice
Findings in Rat confirmed to establish a linear
relationship between toxicity and body surface area
MTD can be established in non-rodent species, if:
Predictability is known to be poor in Rodents
(e.g. Antifolates)
Drug has a novel mechanism of action
21. Toxicokinetic studies
Generation of pharmacokinetic data (ADME):
• A part of non-clinical toxicity studies or
• A separate supportive study
Purpose:
• Assessment of systemic exposure of test substance
• Relationship of toxicology to dose and time course
• Choose species & regimen in subsequent toxicity studies
• Designing of subsequent non-clinical toxicity studies
22. Rodents
• One rodent species (preferably rat)
• At least 4 graded doses including control
• Minimum of 5 animals of each sex
• Proposed clinical route of administration
• Test substance given daily for 10 consecutive days
Non-Rodents
• One male and one female (Dogs > Primates)
• Starting dose (3 or 5 x extrapolated effective dose) or
MTD
(whichever is less)
• Dose escalation every 3rd day, lowered if toxicity seen
• Then test substance given daily for 10 consecutive days
Dose-ranging study
Establishment of MTD for repeated dose studies
Identification of Target organ of toxicity
23. Repeated-dose Toxicity Studies
Duration depends on proposed clinical trial
At least 2 species, one non-rodent
Species-specific pharmacokinetics, if any, should
preferably resemble human beings
Route intended for human clinical use
24. Repeated-dose Toxicity Studies
Wherever applicable, include a Control group
3 other groups are formed, as:
Highest dose Observable toxicity [MTD]
Lowest dose No observable toxicity
[NOAEL]
intended therapeutic dose or
multiple of it
Intermediate dose Some symptoms ; not gross
toxicity or death placed
logarithmically betn doses
26. In all cases:
Behavioural : General appearance, activity,
behaviour
Physiological : Body weight, food intake
Biochemical : Hematology, serum and urine
analysis
Pathological : Organ weights, gross & microscopic
study of viscera & tissues
Parameters to be monitored
•If parenteral drug administration:
Injection site : Gross and Microscopic
examination
•In non-rodent species:
Electrocardiogram : Initial and Final
Fundus examination
28. Reproductive Toxicity
Male Fertility
Female Reproduction & Developmental toxicity
Female Fertility
Teratogenicity
Perinatal development
29. Male Fertility Study
One rodent species (preferably rat)
3 dose groups and a control group :
Dose selection : results of previous 14 or 28-day toxicity
study
Highest dose : showing minimal toxicity in systemic
studies
6 adult male animals per group
30. Test substance by intended route of use
for :
• minimum 28 days
• maximum 70 days
Paired with female animals of proven
fertility in a ratio of 1:2
Drug treatment of male animals continues
during pairing
Pairing continued till detection of Sperm
in vagina or 10 days, whichever is earlier
31. Pregnant females examined after day 13
of gestation
Males sacrificed at the end of the study
Weights of each testis and epididymis
recorded
Sperms from one epididymis examined
for motility and morphology
Other epididymis and both testes
examined for histology
32. Female Reproduction and
Developmental Toxicity Studies
For all drugs proposed for women of child bearing age
• Segment I : Female fertility
• Segment II : Teratogenicity
• Segment III : Perinatal development
Segment I, II and III studies in albino mice or rats, and
Segment II study also in albino rabbits as a second test
species
33. Female Fertility Study (Segment I)
One rodent species (rat preferred)
3 graded doses
Highest dose : doesn’t affect general health of parent
animals
(usually the MTD from previous systemic studies)
At least 15 males and 15 females per dose group
Route of administration same as intended for therapeutic
use
34. Pups : Physiology, Behaviour, Pathology (sex-wise distribution
noted)
Body weight
Food intake
Clinical signs
of intoxication
Reproduction
and
Parturition
Pathology
Gross &
Micro
Females allowed to litter,
medication continued till weaning of pups
Drug treatment continued during mating and gestation period
Drug administration : 28 days (males) & 14 days (females) before
mating
35. Teratogenicity Study (Segment II)
Rodent (preferably rat) and Non-rodent (rabbit)
Drug administered throughout organogenesis
3 dose levels and a Control group:
Highest dose : minimum maternal toxicity
Lowest dose : as proposed clinical dose or its multiple
Route of administration : same as intended for humans
At least 20 pregnant rats (or mice) and 12 rabbits, for
each dose
37. Perinatal Study (Segment III)
Specially if
→ Drug to pregnant / nursing mothers for long periods
→ Indications of possible adverse effects on foetus
One rodent species (preferably rat)
Dosing comparable to multiples of human dose and route
At least 4 groups (including control), 15 females / group
Drug throughout last trimester (from day 15 of gestation)
Dose causing low foetal loss continued throughout weaning
38. F1 litter
1 male and 1 female from each group
Test substance given
Throughout growth to sexual life
Mating performance and fertility of F1 :
F2 generation
F2 generation
growth parameters monitored till
weaning
41. Local Toxicity
If intended for special route (other than oral) in humans
Appropriate site (e.g., skin or vaginal mucous membrane)
in a suitable species
Preferably use of 2 species
3 dose levels and untreated and / or vehicle Control
If the drug is absorbed systemically, appropriate systemic
toxicity studies also required
42. Dermal Toxicity
As cutaneous contamination is always a possibility
Rabbit and Rat
Applied on shaved skin
Concentrations 7 fold higher than the clinical doses
Period of application : 7 to 90 days
Evaluation
› Local signs (erythema, oedema and eschar formation)
› Histological examination of sites of application
43. Ocular toxicity studies
2 species, including an albino rabbit with a large
conjunctival sac
Initial single dose application:
To decide exposure concentrations for repeated-dose
studies
Repeated dose study :
Duration subject to clinical use (Maximum of 90 days)
2 different concentrations exceeding human dose
In acute studies, one eye kept as control. A separate control
group should be included in repeated-dose studies.
44. Ocular toxicity studies
Evaluation
Slit-lamp examination
To detect the changes in cornea, iris and aqueous
humor.
Fluorescent dyes (sodium fluorescein, 0.25 to 1.0%)
To detect defects in surface epithelium
Intra-ocular tension monitored by a tonometer
Histological examination (fixation in Davidson’s or
Zenker’s fluid)
45. Vaginal Toxicity Test
Rabbit or Dog
Topical application (vaginal mucosa) as pessary, cream or
ointment
6-10 animals per dose group
Higher concentrations / several daily applications (in
multiples of daily human dose)
7-30 days, as per clinical use
Observation parameters :
General : swelling, closure of introitus
Histopathology of vaginal wall
46. Rectal Tolerance Test
Preparations meant for rectal administration
In rabbits or dogs
6-10 animals per dose group
Volume comparable to human dose (or the maximum possible
volume) to achieve administration of multiples of daily human dose
7-30 days, as per clinical use
Observation parameters
Clinical signs :- signs of pain, blood and/or mucus in faeces,
condition of anal region/sphincter
Gross examination and (if required)
Histological examination of rectal mucosa
47. Parenteral Drugs
Intravenous/ intramuscular/ subcutaneous/ intradermal
inj.
Injection sites in systemic toxicity studies examined
grossly and microscopically
If needed, reversibility of adverse effects may be
determined on a case to case basis
48. Inhalation toxicity studies
1 rodent and 1 non-rodent species
Acute, subacute and chronic toxicity studies according to
the intended duration of human exposure
Gases and vapors given in whole body exposure
chambers; aerosols are given by nose-only method
Dose (limit dose of 5mg/l) in multiples of human
exposure
Particle size of 4 micron (especially for aerosols) with not
less that 25% being 1 micron
49. Inhalation toxicity studies
3 dose groups and a control
Duration of exposure : maximum of 6 hr/day & 5
days/week
Evaluation :
Respiratory rate, BALF examination, histological
examination of respiratory passages and lung tissue
Regular parameters of systemic toxicity studies or
assessment of margin of safety
51. Allergenicity / Hypersensitivity
Any one of the standard tests:
Guinea pig :
Maximization test (GPMT)
Mouse :
Local lymph node assay (LLNA)
52. Guinea Pig Maximization Test
Challenge
(skin reaction
appears)
Induction : Minimum irritant dose (intradermal
injection)
Challenge : Maximum nonirritant dose (topical
application)
Doses are determined by a preliminary study
Induction
(immune response
develops)
53. Main test
A minimum of 6 male and 6 female animals per group
One test group
One control group
One positive control group (preferable)
If no response : re-challenge 7-30 days after primary
challenge
54. Induction (Day 0)
3 pairs of intradermal injections on either shoulders :
• 0.1 ml Freund’s adjuvant alone
• 0.1 ml test material (lowest irritant dose)
• 0.1 ml test material in Freund’s adjuvant
Day 7 : Topical patch at prepared shoulders (lowest irritant dose)
Challenge (Day 21)
Topical patch at prepared flanks (highest non-irritant dose)
• Left side: Test agent
• Right side: Vehicle
Evaluation [Edema and Erythema] after 48 hr.
55. Local Lymph Node Assay
Mice of the same sex, either only males or only females
Drug treatment given on ear skin
3 graded doses (the highest being maximum nonirritant
dose) plus vehicle control
A minimum of 6 mice per group
Test material applied on ear skin on 3 consecutive days
On day 5, i.v. 3H-thymidine / bromo-deoxy-uridine (BrdU)
Draining auricular lymph nodes dissected after 5 hrs
Evaluation : Increase in 3H-thymidine or BrdU
incorporation
57. Genotoxic compounds are presumed to be trans-species
carcinogens, need not require long-term carcinogenicity
studies
If intended for chronic administration, a chronic toxicity
study (up to one year) to detect early tumorigenic effects
ICH Standard Tests are generally conducted
• In vitro test for gene mutation in bacteria
• In vitro cytogenetic evaluation of chromosomal
damage :
• Mammalian cells or
• Mouse lymphoma tk assay
• In vivo test for chromosomal damage using rodent
hematopoietic cells
58. Ames’ Test
( Bacterial Reverse Mutation Assay )
S. typhimurium tester strains TA98, TA100, TA102,
TA1535, TA97 or
Escherichia coli WP2 uvrA or Escherichia coli WP2 uvrA
In-vitro exposure at a minimum of 5 log dose levels
“Solvent” and “positive control”
2.5 fold (or more) increase in number of revertants in
comparison to spontaneous revertants are considered
positive
59. In-vitro cytogenetic assay
Performed in CHO cells or on human lymphocyte in
culture
In-vitro exposure using a minimum of 3 log doses
“Solvent” and “positive control”
[Positive control : Cyclophosphamide / Mitomycin C
gives a reproducible and detectable increase in
clastogenic effect]
> 50% inhibition of cells is considered significant
60. Mammalian cell test systems
Division stimulated with phytohemagglutin
Division arrested in metaphase using a spindle inhibitor
Evaluation by light microscopy
Increased number of aberrations in metaphase chromosomes
61. In Vitro Mouse Lymphoma TK Assay
Mouse TK lymphoma cells
Thymidine kinase (TK) enzyme involved in salvage pathway
for incorporation of thymidine into cells via phosphorylation
Trifluorothymidine (TFT) also phosphorylated by TK
Cells containing TK are sensitive to toxic effects of TFT
Forward mutations from TK+ to TK- result in loss of TK
activity
Quntifiication of mutant cells : Cells with TFT resistance
62. In Vivo Tests for Chromosomal Damage
Mammalian Bone
Marrow
Chromosomal
Aberration Assay
Rodent
Erythrocyte
Micronucleus
Assay
63. In-vivo cytogenetic assay
Clastogenic & Aneugenic effects in metaphase chromosomes (min
100)
Bone marrow : Giemsa staining
Sacrificed 2 hours after colchicine administration
Dosing on day 1 followed by i.p. colchicine administration at 22
hours
• One rodent species (preferably rat)
• Route of administration same as intended for humans
• 5 animals/sex/dose groups
• 3 dose levels, “solvent” and “positive” control (Cyclophosphamide)
64. In-vivo micronucleus assay
↑micronuclei in polychromatic erythrocytes [M-PCE] (min 1000)
Bone marrow : Smeared with May Gruenwald / Giemsa stain
Sacrifice of animals 6 hours after the last injection
Dosing : day 1 and 2 of study
• 1 rodent species (preferably mouse) needed
• Route of administration of test substance same as humans
• 5 animals / sex / dose groups
• At least 3 dose levels, plus “solvent” and “positive” control
• Positive control : mitomycin C or cyclophosphamide
66. Carcinogenicity
For expected clinical use more than 6 months
For drugs used frequently in an intermittent manner
If concern about the carcinogenic potential due to :
Previous demonstration in the product class
Structure-activity relationship suggests carcinogenic
risk
Preneoplastic lesions in repeated dose toxicity studies
Long-term tissue retention results in reactions
67. Carcinogenicity
Where life-expectancy in the indicated population is
short (i.e., less
than 2 - 3 years) - no long-term carcinogenicity studies
Where therapy is generally successful, there may be later
concerns regarding secondary cancers. So
carcinogenicity studies needed
A rodent species (preferably rat). Mouse only if justified
Strain should not have normal incidence of spontaneous
tumors
68. Carcinogenicity
At least 3 dose levels :
Highest dose : sub-lethal, should not reduce life span
of animals by more than 10% of expected normal
Lowest dose : should be comparable to the intended
human therapeutic dose or a multiple of it, e.g. 2.5x; to
make allowance for the sensitivity of the species
Intermediate dose : placed logarithmically between the
other 2
Untreated control and (if indicated) a Vehicle control
group
69. Carcinogenicity
Life span comparable to human’s over which drug use is
intended
Generally, 24 months for rats and 18 months for mice
Atleast 50 animals of each sex
Observation parameters
Physiology, Behaviour, Biochemistry, Pathology
Comprehensive descriptions of benign and malignant
tumour development, time of their detection, site,
dimensions, histological typing etc
72. Clinical trials & marketing- Requirements
Systemic Toxicity Studies -oral/parenteral/
transdermal route
Duration of
proposed
human
administration
Human phases
for which
study is
proposed to be
conducted
Species Long term
toxicity
requirement
Upto 1 week I, II, III 2 2 weeks
1-2 weeks ” ” 4 weeks
2-4 weeks ” ” 12 weeks
> 1 month ” ” 24 weeks
73. Systemic toxicity studies – Inhalational route
Duration of
proposed
human
administration
Human phases for
which study is
proposed to be
conducted
Species Long term
toxicity
requirments
Upto 2 wk I, II, III 2 1 month (exposure
time 3hr/d, 5d/wk)
Upto 4 wk I, II, III 2 3 months (exposure
time 6hr/d, 5d/wk)
> 4 wks I, II, III 2 6 months (exposure
time 6hr/d, 5d/wk)
74. Local Toxicity Studies
Route Duration
of Clinical
trial
Phase Species Duration of
Toxicity
study
Dermal
Ocular
Otic
Nasal
Vaginal
Rectal
Upto 2
weeks
I, II 1 4 wk
III 2 4 wk
> 2 weeks I,II,III 2 12 wk
Hinweis der Redaktion
In case of nonlinearity, a more sensitive species may be used