Phase 0 studies

1. MICRODOSING

2. OVERVIEW
1. INTRODUCTION
2. DEFINITION
3. GOALS OF PHASE 0
4. DESIGN OF PHASE 0 STUDY
5. MICRODOSING AND TECHNICAL ADVANCES
6. MICRODOSING AND REGULATORY ADVANCES
7. ETHICAL , STATISTICAL AND LOGICAL CONSIDERATIONS
8. ADVANTAGES
9. LIMITATIONS
10. CONCLUSION

3. INTRODUCTION
• Human drug development is a dynamic process that
keeps pace with the recent advances within the
pharmaceutical analytical labs, combined with a precise
understanding of the integrated pharmacokinetic,
pharmacodynamic and pharmacogenomic drug profiles.
• New drugs are a great need for many clinical conditions
but, development costs are rising and the number of
drugs receiving marketing approval has fallen.
• Further, drug development is a long, complex and
expensive activity. It typically involves a total cost of US$
500 million to 1 billion per marketed drug and is spread
over 10-15 years.

4. • By early 2000s, the attrition rate of clinical trials was
highest (62%) during Phase II, 45% during phase III and
significant (23%) at the time of registration.
• Suboptimal pharmacokinetics, lack of efficacy and
lack of safety are stated to be the prime reasons for
failures during drug development.
• This situation prompted the FDA to publish the document
‘CRITICAL PATH’, highlighting the problems in drug
development and encouraging novel approaches to be
incorporated into the current drug development paradigm.
• Thus, a new experimental approach was developed,
known as Phase 0 or Microdosing studies, to address
issues pertaining to drug metabolism and
pharmacokinetics.

5. DEFINITION
• In microdosing, extremely low, nonpharmacologically
active doses of a drug are used to define the drug's
pharmacokinetic profile in humans.
• Thus, by definition, microdosing means use of ‘less than
1/100th of the dose calculated to yield a
pharmacological effect of the test substance to a
maximum dose of < 100 micrograms’.
• However, in addition to this, the US FDA suggests a
maximum microdose of < 30 nanomoles for protein
products.

6. • Phase 0 trials are first-in-human clinical trials performed
under the Exploratory IND [Investigational New Drug]
Guidance of the US Food and Drug Administration.
• Unlike traditional phase I trials, these studies have no
therapeutic or diagnostic intent but instead aim to
provide only pharmacokinetic and/or pharmacodynamic
data to inform the next step in developing an agent.
• Microdosing allows not only for the selection of the drug
candidates more likely to be developed successfully, but
also for the determination of the first dose for the
subsequent Phase I clinical trial.

8. COMPARISON OF MICRODOSING STRATEGY AND
CONVENTIONAL PHASE 1 STUDIES
VARIABLE PHASE 1 TRIALS PHASE 0 TRIALS
Primary
endpoint
Establish the maximum
tolerated dose
Target modulation or ability to
image the target of interest
Dose
escalation
Determine safety and
toxicities
Achieve desired systemic
exposure or target modulation,
enabling dose selection for future
studies
Preclinical
biomarker
studies
Not consistently performed
before the trial
Required to have plasma drug
(PK) and preclinical biomarker
(PD) assay development and
assay qualification before the
initiation of the clinical trial
Biomarker
assays
Not performed consistently,
most phase 1 trials do not
emphasize
pharmacodynamic markers
Biomarker assays and/or imaging
studies are integrated to establish
the mechanism of action in actual
patient samples
Number of
patients
Usually >20 10–15

9. COMPARISON OF MICRODOSING STRATEGY AND
CONVENTIONAL PHASE 1 STUDIES
VARIABLE PHASE 1 TRIALS PHASE 0 TRIALS
Dosing Multiple Limited
Therapeutic
benefit
None expected; however,
tumour response is
evaluated to enable
continued dosing in case
evidence of clinical benefit is
found
None
Tumour
biopsies
Optional
Serial tumour biopsies required to
evaluate the effect of the drug on
its target(s)
Pharmacokin
etic/pharmac
odynamic
analysis
Samples are usually batched
and analysed at a later time
Real time

10. GOALS OF A PHASE 0 TRIAL
1) Provide human PK-PD relationship data for a drug prior
to Phase 1 testing.
2) Determine a dose range and sequence of
administration of a biomodulator to be used in
combination.
3) Determine whether a mechanism of action defined in
non-clinical models can be achieved in humans.
4) Refine a biomarker assay using human tissue.
5) Develop a novel imaging probe and evaluate in humans
the drug’s PK & PD effects.
6) Increase chance of success of subsequent
development of the agent.

11. DESIGN OF PHASE 0 STUDY
• Phase 0 trials involve a seamless, rational transition from
preclinical to clinical development.
• This requires close collaboration between laboratory, drug
development, and clinical scientists.

13. TYPES OF PHASE 0 STUDIES
• As supported by the US FDA Exploratory IND Studies
Guidelines.
1) Pharmacokinetics or Imaging studies:
2) Pharmacologically relevant dose studies:
3) Pharmacodynamic Endpoint studies:

14.  Pharmacokinetics or Imaging studies:
• To evaluate human bio-distribution and target binding
characteristics.
• Preclinical toxicology studies should demonstrate that a
dose 100 times the proposed human dose does not
induce adverse effects.

15.  Pharmacologically relevant dose studies:
• Evaluate human PK of two or more analogues to select a
lead agent.
• Preclinical toxicology studies must establish the no
observed adverse effect level (NOAEL) in a rodent two-
week toxicology study.
• The clinical starting dose is generally 1/50th of this dose
(not a microdose).

16.  Pharmacodynamic Endpoint studies:
• To evaluate whether the new molecular entity modulates
it’s intended target.
• Supporting preclinical toxicology studies are generally
short-term, modified-toxicity or safety studies in two
species.
• Dosing levels for these studies are not specified.

17. MICRODOSING PROCEDURE
• Once the cohort of compounds for candidate selection has
been determined, animal PK data and allometric scaling
methodology should be used to determine the possible
human therapeutic dose.
• A 14-day single-dose toxicity study should be carried out in
one animal species to meet regulatory toxicology
requirements for human microdosing.
• A microdosing CTA or exploratory IND should be submitted. If
required, 14C-labeled drug may be obtained.
• Dosing and bioanalytical methods should be standardized
and validated.
• The study should be meticulously designed to dose and
obtain bioanalytical samples for appropriately screened and
consented volunteers.
• And, finally, samples should be analyzed and the results

19. MICRODOSING AND TECHNICAL ADVANCES
• Ultrasensitive and specific analytical methods capable of
measuring drug and metabolite concentrations in the low
picogram to femtogram range are required.
• Most common of these are:
1) Liquid chromatography coupled with tandem mass
spectrometry (LC-MS-MS)
2) Accelerator Mass Spectrometry (AMS)
3) Positron Emission Tomography (PET)
• The choice of analytical technique is largely driven by the
expected plasma-drug concentrations and the limit of
quantification of the analytical method.
• AMS is used for determining PK data.
• PET provides PD data through real time imaging.

20. MEASURING TECHNIQUES USED FOR MICRODOSING
MEASURING
METHOD
LABELING OF
TESTING MATERIAL
CHARACTERISTICS
Accelerator Mass
Spectrometry (AMS)
Radioactive isotopes
with a long half life,
such as 14C
*Extremely high sensitivity
*Capable of constructive
analysis of the metabolites of
the compound *Requires large
facilities and equipment
Liquid Chromatograph
Mass Spectrometer
(LC/MS/MS)
No labeling required *Capacity for profile prediction
of the properties of a
compound
*Suitable for cassette dose test
Positron Emission
Tomography (PET)
Positron-emitting
nuclide with a short
half life, such as 11C,
13N, 18F, 15O
*Capacity to measure
distribution and concentration
of the compound in the body
*Requires large facilities and
equipment

21. CHOICE OF THE ANALYTICAL METHOD
• AMS Highly Sensitive (used for drugs with low
bioavailability and/or high volume of distribution)
• However, there is a growing use of LC-MS in microdosing as
it can offer certain advantages over AMS. They are:
1) In LC-MS, several candidate drugs could be tested in a
single dosing (cassette dosing).
2) LC-MS reveals structural information and resolves
compounds based on molecular weight.
3) AMS cannot distinguish parent drug from metabolites.
Hence an additional HPLC step is required to determine
the parent to metabolite ratio, which makes the process
complex.
4) AMS analysis involves a degree of sample processing
after chromatographic separation, which demands the
accurate addition of an isotopic dilutor.

22. MICRODOSING AND THE REGULATORY GUIDELINES
• Position paper from European Medicines Agency in 2004.
• Guidelines from the FDA in 2006.
• Guidelines from Japan in 2008.
• The ICH M3 international guideline in 2009.
• The latest ICH M3 guideline allows a microdose to be
administered to human subjects based on a single-dose
toxicity study (usually in the rat), followed by 14 days
observation, using the intended route of administration (or
via the intravenous route), plus some in vitro target
receptor data.
• The dose administered in the toxicity study should be 1000
times (EMEA) or 100 times (FDA) the human microdose.
The safety data thus obtained can be used to justify the
administration of a maximum of 100 µg of drug, either as a

23. MICRODOSING AND REGULATORY ADVANCES
• Accurate characterization of the kinetics of a drug over
time, after administration, is an important regulatory
requirement. This can be achieved by administration of
radio-labeled drug to the subject and following its fate in
plasma and excreta.
• Although regulatory authorities may not make
microdosing a mandatory requirement as the data can
be obtained by other methods, they may provide approval
or incentives for companies bringing certain drugs like life-
saving medications to the development and
commercialization stages more rapidly.

24. PHASE 0 : ETHICAL CONSIDERATIONS
Potential barriers to enrollment to be considered are (risk to
benefit ratio of the phase 0 trial ):
1) No therapeutic intent or benefit
2) Risk from research-related interventions, such as serial
tumour biopsies (in cancer studies) and computed
tomography scans
3) Fear in patients for delayed participation in or exclusion
from other clinical trials that would otherwise provide
therapeutic benefit
4) Opinion of primary physician
5) Lack of participant’s understanding of the informed
consent document

25. ETHICS: INFORMED CONSENT PROCESS
1) Need to clearly explain the rationale for the study
2) Difference between therapeutic trial and experimental
research needs to be explained
3) Need to clearly state that there is absolutely no
anticipated clinical benefit to the participant
4) Participants understanding is vital & measurement of
patient’s understanding is required.

26. PHASE 0: STATISTICAL ISSUES
• Following aspects should be considered:
1) Sample size should be generally limited to 6-15 patients.
2) Primary endpoint(s) should be defined prospectively.
3) Measure of intra-patient variability for the pre-treatment
endpoint values should be obtained, if possible.
4) The thresholds for declaring treatment effect on
efficacy(biomarker) for an individual patient, for a given
dose, based on both biological and statistical criteria
should be defined .
5) A reasonable false positive rate (10%) with high power
(90%) should be maintained across dose levels.

27. PHASE 0: LOGISTICAL CONSIDERATIONS
• Mechanism for selecting and prioritizing candidate agents.
• Dedicated Labs:
1) Non-clinical PD assay labs
2) Non-clinical animal models
3) Human tissue PD laboratory, capable of real-time analysis
4) PK lab capable of real-time analysis
• Research teams:
1) Clinical team with expertise in conduct of early phase trials
2) PK/PD scientists
3) Biospecimen procurement and processing staff
4) Interventional radiologists
5) Special imaging and nuclear medicine staff
6) Statisticians
• Willing patient participants

28. ADVANTAGES OF MICRODOSING
1) Reduces the unnecessary exposure of the participants to
the non-potential compounds, which can be rejected
earlier
2) Microdosing requires minute quantities of the drug for
safety testing. Hence, the risk of adverse events is less.
3) Lesser preclinical safety information is required. Thus,
further animal studies can be avoided with compounds
having unsuitable pharmacokinetic profiles.
4) From preliminary toxicology data of animals,
pharmacokinetic data for the initial dose selection can be
obtained in a short time of 4-6 months, whereas in Phase
I studies it takes 12-18 months.
5) Microdosing offers the potential to aid in early candidate
selection.

29. 6) During drug development, when a large number of me-too
compounds are screened and found to have similar or
differing animal pharmacokinetics, comparative human
microdose studies can be done to establish
pharmacokinetics.
7) The cost of conducting a microdose study is phenomenally
less, as compared to a full Phase I study.
8) Microdosing could be useful in the discovery of endogenous
biomarkers, which would assist in the quantitative evaluation
of the in vivo effects of drugs.
9) Use in oncology: Phase 0 studies are designed with the
objective to establish whether an agent is modulating its
target in a tumor, and consequently whether further clinical
development is warranted at the very earliest opportunity
(before a large numbers of patients have been exposed to
potential drug-associated toxicity).
10)Drug can be assessed in vulnerable patients such as
patients with renal impairment, women in their reproductive
age, cancer patients, etc.

30. EMERGING USES OF MICRODOSING
1) To study drug-drug interactions and polymorphisms
(using microdose probes).
2) Measuring drug concentrations at the site of action.
3) Intravenous data: By incorporating an intravenous
microdose study into pharmacokinetic simulations, reliable
values for drug clearance in humans can be obtained.
4) Metabolic profiling: To obtain preliminary data on the
metabolism of a candidate, drug samples from microdose
studies have been metabolically profiled.
5) For early supportive data for drug delivery.
6) Used in synergy with In-silico approaches
7) Used in synergy with Pharmacogenomics and
Metabolomics

31. LIMITATIONS OF MICRODOSING
1) Absence of any therapeutic and/or diagnostic intent
2) Motivating volunteers to become a part of the trial is
difficult as there is no therapeutic intent
3) Very few validated biomarkers are available for
predicting the efficacy of some drugs (anti-cancer
activity).
4) Caution needs to be maintained while administering
drugs demonstrating complex/non-linear kinetics as
microdosing is still in its initial stages
5) Extends the process and increases the expenditure as
Phase 1 still needs to be carried out.

32. LIMITATIONS OF MICRODOSING
6) Microdose activity: There is lack of clarity on whether
the body's reaction to a particular compound is similar,
when used as microdose and in its pharmacological
dose; otherwise, it could lead to false negatives
(compound being rejected) or false positives (compound
acceptable based on microdose data but rejected
subsequently when used in pharmacological doses).
Thus, a microdose may not be able to predict the
behaviour of a clinical dose of the drug.
7) Analytical Methods: AMS (accelerator mass
spectrometry) and PET (positron emission tomography)
are radiotracer assays which have the disadvantages of
short tracer half-life and limited specificity (as assay may
include metabolites also). Also, these are costly and
scarcely available.

33. LIMITATIONS OF MICRODOSING
8) Compound metabolism and solubility of compound:
Many processes within the body involve the use of
specialized transporters, enzymes and binding sites,
which can be saturated such that the pharmacokinetic
profile is very different at the higher therapeutic dose than
seen with the microdose.
9) Solubility of compounds: Most compounds dissolve
rapidly at microdose levels, yielding rapid and often
extensive absorption. However, at higher therapeutic
doses, many compounds exhibit limited solubility. This
means, absorption becomes more dependent on the rate
and extent of dissolution, which cannot be predicted by
microdose. Thus, it has been suggested that the dose of
100 micrograms may be too low to achieve the full

34. STATUS IN INDIA
• There is no concept of Phase 0 or any other equivalent of
an Exploratory IND in Indian regulation.
• In 2007-08 the Indian Society for Clinical Research
(ISCR) proposed a change in regulation that would allow
the regulators to recognize and permit microdosing
studies in India.
• The Drugs Technical Advisory Board (DTAB)
unanimously approved the proposal together with other
far-reaching amendments in regulation.
• The proposals were, nevertheless, disregarded by the
government due to non-technical sensitivities that
surround clinical research and drug development in India.

35. PUBLISHED HUMAN MICRODOSE TRIALS
 CREAM Trial : Consortium for Resourcing and
Evaluating AMS Microdosing. Involved 5 drugs viz.,
Midazolam(high first pass metabolism), Diazepam,
Warfarin(long half life), Erythromycin and ZK-253
 EUMAPP : European Microdosing AMS Partnership
Programme : A study comparing in vitro, in silico,
microdose and pharmacological dose
pharmacokinetics.
 NEDO: New Energy and Industrial Technology
Development Organization (NEDO) research

36. THANK YOU