The document discusses extrapolating data from preclinical in vitro and in vivo animal studies to humans in clinical trials. It provides information on different types of studies and explains how data from animal models is used to estimate safe starting doses for human subjects. The key points are: 1) Preclinical studies test drugs in animal and cell models before human trials to evaluate toxicity and effects. Data from these studies is extrapolated using mathematical processes to estimate appropriate human doses. 2) The no-observed-adverse-effect level (NOAEL) from animal studies is used to calculate a human equivalent dose (HED) based on body surface area, accounting for differences between species. 3) Additional safety factors are applied

1. Extrapolation of in vitro data
to preclinical and preclinical
humans.
Arshi khanam
M.PHARMA(cology)
1st sem
Kurukshetra university

2. In-vitro and in-vivo studies
 in vivo are those in which the effects of various biological
entities are tested on whole, living organisms or cells, usually
animals, including humans, and plants, as opposed to a
tissue extract or dead organism.
 In vitro studies are performed with microorganisms, cells, or
biological molecules outside their normal biological context.
Colloquially called "test-tube experiments", these studies in
biology and its sub disciplines are traditionally done in lab
ware such as test tubes, flasks, Petri dishes, and microliters
plates.

3. In vitro toxicology
 In vitro toxicology consists of using cells or tissues
maintained or grown in controlled laboratory conditions to
examine the toxic properties of compounds and mixtures.
This allows us to examine the toxicity of xenobiotics at the
fundamental level of the cell without the interplay of complex
physiological systemic effects that are often observed in
whole organisms. However, specific cellular functions could
be examined with primary cultures of cells from specific
tissues such as the liver for xenobiotic biotransformation,
kidney or gills for ionic homeostasis, and the nerve cells
for neurotransmitter signaling effects.

4. The main advantages of in
vitro tests are as follows:
 (1) reduction of animal sacrifice during toxicity screening of
various chemicals,
 (2) more controlled exposure conditions (hormonal and
cofactor make-up of the exposure media),
 (3) increased precision of the response (less biological
variation than with in vivo systems)
 (4) high bioanalytical throughput for rapid screening
investigations.

5. What is extrapolation
 Extrapolation can be defined as estimate or arrive at a
conclusion based on known facts or conclusions.
 In other words Extrapolation is defined as an estimation of a
value based on extending the known series or factors beyond
the area that is certainly known. In other words, extrapolation
is a method in which the data values are considered as
points such as x1, x2, ….., xn. It commonly exists in statistical
data very often, if that data is sampled periodically and it
approximates the next data point. One such example is when
you are driving, you usually extrapolate about road conditions
beyond your sight. In short understanding the unknown data
from the known data.
 In preclinical studies we use mathematical process
extrapolation to estimate the conclusions of preclinical drug
testing data to human drugs. This make us understood that
how a drug dose and data can be correlated of estimated to
get the same effect in higher mammals.

6. Preclinical studies
 Preclinical studies refer to the testing of a drug, procedure or
other medical treatment in animals before trials may be
carried out in humans. During preclinical drug development,
the drug’s toxic and pharmacological effects need to be
evaluated through in vitro and in vivo laboratory animal
testing. The FDA requires sponsoring companies to develop
a pharmacological profile, determine toxicity in at least two
species of animals and conduct short-term toxicity studies.
Various preclinical requirements exist for different kinds of
laboratory animals. Information gathered in preclinical studies
are used as evidence and support in FDA applications for the
approval of new drugs and medical procedures.

7. Preclinical stages

8. Extrapolation of preclinical data
Preclinical in vivo and in vitro studies are fundamental to the
safe and effective development of new drugs. Preclinical
research is essential to a better understanding of the
pharmacological and toxicological activities of drugs and their
metabolites. Data generated by animal models and alternative
methods can be used and extrapolated to improve clinical
trials, particularly those for anticancer drugs.
Estimation the first human dose is the first step in clinical trial
or clinical development of the drug molecule, it has to go
through the successfully through all of the hurdles of preclinical
studies.
 A dose response curve must be obtained to check the
therapeutic dose and the toxic dose.
 Adverse drug response must be estimated to nullify the
consequences.

9. Dose response curve

10.  The minimum anticipated biological effect level (MABEL)-
for selection of first human dose in clinical trials with
monoclonal antibodies.
 The no-observed-adverse-effect-level (NOAEL) is an
important part of the non-clinical risk assessment. It is a
professional opinion based on the design of the study,
indication of the drug, expected pharmacology, and spectrum
of off-target effects. The common definition of NOAEL, "the
highest experimental point that is without adverse effect,"
 The lowest observed adverse effect level LOAEL -- Lowest
dose at which there was an observed toxic or adverse effect.

12.  Extrapolation to humans is achievable only when effects produced
in appropriately qualified laboratory animals are relevant to
humans. The exposure of experimental animals to high doses is
necessary to discover possible hazards to humans. However,
species differences, different physiology, metabolism,
organography (e.g., GI tract in dogs), and the setting of “healthy
animal versus human patient” often make an extrapolation of data
to humans very difficult.
 Human and animal in vitro models are potentially powerful
preclinical tools in the prediction of the pharmacological behavior
of drugs; the selection of the animal species most closely related
to humans on the basis of metabolic pattern; the assessment of
the duration of drug action, particularly those drugs exhibiting
different metabolic clearances; the understanding and prediction
of drug interactions; and the explanation of the metabolic origins
of interindividual variability in pharmacological activity. The
ultimate challenge remains the extrapolation of preclinical data to
clinical reality

13. Estimation for maximum
recommended starting dose (MRS)
Aim of MSRD:
• Avoid toxicity at initial dose
• Dose needs to be high enough to allow reasonably rapid
attainment of phase I trial objectives.
Not applicable to:
• Endogenous hormones and proteins (i.e. recombinant clotting
factors) used at physiological concentrations
• Vaccines
Limitations:
• Does not address dose escalation or maximum allowable
doses in clinical trials

14. MRSD estimation methods
 1) NOAEL Method
 2) MABEL Method
 3) Similar Drug Comparison Method
 4) Pharmacokinetic Guided Approach
 5) PK/PD Modelling Guided

15. 1. NOAEL METHOD
 The NOAEL(NO OBSERVED ADVERSE EFFECT LEVEL)
method is based on selecting a dose with minimal risk of
toxicity, rather than selecting one with minimal pharmacologic
activity in humans. This approach works well with new
molecules that act on established targets and/or have the
pharmacology that is more or less understood.
 5 Steps using animal toxicology data:
 1) Determine No Observed Adverse Effect Level (NOAEL) ‰
 2) Convert NOAEL to Human Equivalent Dose (HED) ‰
 3) Select most appropriate species ‰
 4) Apply Safety Factor ‰
 5) Consider Pharmacologically Active Dose

16.  STEP 1: NO OBSERVED ADVERSE EFFECT LEVEL
DETERMINATION
 The NOAEL is a generally accepted benchmark for safety
when derived from appropriate animal studies.
 The available animal toxicology data is reviewed and
evaluated so that a NOAEL can be determined for each
study.
 While reviewing the animal toxicology data, the adverse
effects that are statistically significant and adverse effects
that may be clinically significant (even if they are not
statistically significant) should be considered in the
determination of the NOAEL.

17.  STEP 2: HUMAN EQUIVALENT DOSE CALCULATION
Conversion Based on Body Surface Area
 • After the NOAELs in the relevant animal studies have been
determined, they are converted to human equivalent doses
(HEDs) using appropriate scaling factors.
 • The most appropriate method for extrapolating the animal
dose to the equivalent human dose should be decided.
 • Toxic endpoints for therapeutics administered systemically
to animals, such as the MTD or NOAEL, are usually
assumed to scale well (doses scaled 1:1) between species
when doses are normalized to body surface area (mg/m2)
 • The basis for this assumption: Doses lethal to 10% of
rodents (LD10) and MTDs in non-rodents both correlated
with the human MTD when the doses were normalized to the
same administration schedule and expressed as mg/m2.

18.  • Correcting for body surface area increases clinical trial safety
by resulting in a more conservative starting dose estimate.
 • Hence, it was concluded that the approach of converting
NOAEL doses to an HED based on body surface area
correction factors (i.e., W0.67) should be maintained for
selecting starting doses for initial studies in adult healthy
volunteers.
 CONVERSION FACTORS:
 • These are recommended as the standard values to be used
for interspecies dose conversions for NOAELs.
 • Since surface area varies with W0.67, the conversion factors
are therefore dependent on the weight of the animals in the
studies.
 • These factors may also be applied when comparing safety
margins for other toxicity endpoints (e.g., reproductive toxicity
and carcinogenicity) when data for comparison, (i.e., AUCs)
are unavailable or are otherwise inappropriate for comparison.

19.  HED = Animal NOAEL x (W (animal)/W( human)(1-b)
 Conversion factors = (W animal/W human)(1-b)
 Conventionally, for a mg/m2 normalization b would be 0.67,
but studies have shown that MTDs scale best across species
when b=0.75.
 Conversion factors are calculated over a range of animal and
human weights using (W animal/W human)0.33 or (W
animal/W human)0.25 to assess the effect on starting dose
selection of using b = 0.75 instead of b = 0.67.
 However, converting doses based on an exponent of 0.75
would lead to higher, more aggressive and potentially more
dangerous starting doses.
 Nonetheless, use of a different dose normalization
approach, such as directly equating the human dose to the
NOAEL in mg/kg, may be appropriate in some
circumstances.

21. Here Km is value unique to each species and
expressed by weight *K

22.  After dose calculation most appropriate species is selected
with reference to pharmacological and therapeutically
references.
 Then after species selection the application of safety factor is
done to making sure that the drug is being used is safe as
the human subject is receiving the first clinical dose. It is a
very essential steps for the clinical studies.
 After that the pharmacological active dose is considered and
then taken to the further new drug file procedures starts.

24. Thank you