Download Tumor Biopsies

Why do we conduct biological correlative studies
for targeted agents?
1. We often have difficulty in determining the optimal
dose/schedule in phase 1 to take forward to Phase 2
• Standard cytotoxic drugs lead to predictable effects
on proliferating tissues (neutropenia, mucositis,
diarrhea), thus enabling dose selection via MTD and
confirming MOA- not necessarily true for targeted
agents
2. A toxicity-based MTD may not represent the optimal
biological dose
3. These agents can be associated with absent or lowlevel tumor regression as single agents- we need to
know that we are doing something prior to phase 2/3!
A biological correlate can be:
1. Mechanism-based toxicity
2. Biological effects on tumor or
surrogate tissue
3. Clinical efficacy
Pharmacodynamic (PD) biomarker: Associated with drug
exposure- so that’s what most of your protocols contain.
Example: Reduction in p-ERK in PBMCs post-MEK
inhibitor
Predictive biomarker: Predicts outcome to therapy- most
useful ones are used before treatment to select patients.
Example: KRAS mutation, Her2/Neu, ER/PR
Prognostic biomarker: Associated with outcome,
independent of therapy- often discovered retrospectively in
phase III trials.
Example: Ki67 index
Biomarkers: Clarifications
• Pharmacodynamic (PD) biomarkers can also be
predictive
• Mechanism-based toxicity is toxicity attributable to MOA
and is a type of PD biomarker
• Prognostic biomarkers can also be predictive and
vice versa, but a classic prognostic biomarker must
be assessed in untreated patients
• Just because a biomarker is prognostic, does not mean
that it will be predictive for an agent that targets that
pathway (VEGF is a classic example)
How Biomarkers are Used in
Early Clinical Development
Single-agent activity (in unselected patients) can be
limited with targeted agents, thus biomarkers– May be used to effectively screen numerous
agents in phase I for biological activity
– To prioritize agents going into phase II, and
– To enhance activity through patient selection
Increasingly the pharmaceutical industry is using
biomarkers to make go/no-go decisions
Few of them are validated preclinically prior to phase I
trials- and this is a problem (and common in Vail
protocols!)
Biological Correlative Studies:
Definitions
• Target tissue: tumor!
• Surrogate marker, tissue: feasible tumor
substitute!
• Mechanism-based toxicity: toxicity attributable to
MOA (for cytotoxic agent- NTP)
• Bioassay, biomarker, correlative assay, biological
correlative assay, PD marker- different terms for
the same thing
Mechanism-Based Toxicity as a
Biological Correlate
• With drugs that interact with a target on normal tissues,
mechanism-based toxicity is a type of biomarker:
o skin rash, diarrhea- EGFR agents
o hypertension, proteinuria- VEGF agents
• Overall, not unlike the myelosuppression and GI effects
(mucositis, diarrhea) observed with traditional cytotoxic
agents
• If a tissue-based biomarker is difficult to obtain,
mechanism based toxicity may establish biological
activity- and you don’t need to biopsy the patient!
Decrease in Ki67 (top) and pERK1/2 (bottom) in skin biopsies
following PF299804 (pan-EGFR TKI) treatment.
Jänne P A et al. Clin Cancer Res 2011;17:1131-1139
©2011 by American Association for Cancer Research
Skin changes with EGFR-targeted agent
So- if you establish that normal tissue (like skin) is a relevant biological
target, then the presence of skin rash may substitute for a skin biopsy
However, this will primarily indicate drug exposure, but not intended
antitumor effects
What are Commonly Used Biological Assays?
Typical surrogate assays that are feasible:
•
Plasma or serum-based (usually ELISA)
•
PBMCs: immunoblotting/ IHC/flow cytometry/ELISAs
•
Normal skin/ buccal mucosa/hair: IHC
•
Circulating endothelial cells
Tumor-based assays:
•
IHC/immunoblotting (proteins, phosphorylation, apoptosis)
•
Microvessel density (has not been useful in patients)
•
Gene expression (RT-PCR)/mutation/sequencing
•
Also consider circulating tumor cells
Radiological: PET, DCE-MRI, CT, ultrasound
How Do You Select an Assay?
•
First, if the drug has been used before- in humans or animalsobtain information. What has been done previously? Learn from
others!
•
If it’s a brand-new target, search the literature for information
about target – where expressed (normal tissue)- and how
measured- protein? gene? activation status? cytokine?
•
Consider a research collaboration with a lab/investigator that is
familiar/interested in the target to potentially design the best
assay and test it preclinically in in vitro or in vivo models.
•
Make sure you understand why you are doing the assay- at the
end of the study, how will this assay facilitate clinical
development? What hypothesis is being tested?
Some Considerations When Selecting an Assay
1.
Patient acceptance: Is obtaining the sample painful to the
patient? Is a separate consent form or check box required.
2.
Feasibility: How easy is it to obtain samples? Is the assay one
that can be “banked”- or does it have to be run same-day?
3.
Cost: This relates to #2 and also dictates frequency of sampling
and how much grant funding is required.
4.
Who will perform and where will assay be run? Will there be a
central site or lab performing it?
5.
Reproducibility/ validation/ quality control: Its best to have this
done and figured out prior to trial- either using preclinical models
or normal volunteer samples.
Pros and Cons of Commonly Used Assays
Assay
Pro
Con
Plasma/Serum
Easy to collect, non-invasive
Only reflects what is
circulating- does not sample
tissue compartment
PBMCs
Relatively easy to collect, but Often require ex vivo
requires special processing
“stimulation” to see markerand storage
which leads to variability
Skin biopsy
Can be done in clinic without
imaging
Invasive and may not
express target
Tumor biopsy
Is the real target
Invasive, expensive and
often requires imaging
Functional Imaging:
PET/MRI
Non-invasive and may
demonstrate changes when
tumor size does not change
Expensive, should be
validated in preclinical
models
What is the Appropriate Sampling Schedule?
o
Plasma/blood sampling: Baseline, and potentially at times that
correspond to PKs, at steady-state, then periodically after C1
(weekly, monthly).
o
PBMCs: Require more processing, so usually feasible to obtain
at baseline, 1-3 time points around PK samples, at steady-state,
then perhaps once a course.
o
Tumor tissue/skin biopsy: Baseline, and then usually only
feasible to obtain once more- either at a “kinetic” time point (peak
drug concentration, steady-state) or “efficacy” time point (end of
C1 or C2, with imaging).
o
Imaging: Similar to tumor tissue, but since non-invasive, can
perform at “kinetic” and “efficacy” time points.
Example:
Preclinical-to Clinical Application
of Biological Correlative Studies with MEK
Inhibitor
Figure 2">
Yeh, T. C. et al. Clin Cancer Res 2007;13:1576-1583
Copyright ©2007 American Association for Cancer Research
Selumetinib Part B: Percentage change in pERK
19 of 34 paired
biopsies (56%)
evaluable
*
*
Overall mean
inhibition of
pERK of 84%
compared to predose
* 200mg patients
Patient 0255 (Melanoma, 100 mg BID)
Pre-Dose CT Scan
Post - Dose CT Scan
Completed 3 Cycles
70% reduction of target lesions
– Although non target lesion
progression in brain
08-17-2005
01-05- 2006
Tumor
– 100 % inhibition of pERK
– 97% inhibition of Ki67
pERK
Nras mutation
Ki-67
Pre-Dose
Post-Dose
What Did We Learn
from the Biological Assays in this Trial?
• The preclinical PBMCs and tumor tissue were useful in designing the
assays used in the first-in-man phase I trial.
• Inhibition of p-ERK in PBMCs is observed at all dose levels and thus,
although useful in establishing that the oral drug penetrates into
tissue, is less useful for establishing dose-schedule.
• Skin rash also occurred at all dose levels, was dose-limiting, and thus
was the predominant factor in establishing the MTD. This is thought
to be mechanism-based, thus precluding the need skin biopsies.
• Tumor tissue reliably demonstrated a reduction in p-ERK which did
not correlate to response.
• Therefore, the drug is biologically active and can (and has) proceed
to phase II/III, but will need other predictive and/or PD biomarkers for
selecting patients and/or indicating clinical benefit.
Tumor Biopsies: Lessons Learned
•
Tumor biopsies are feasible to obtain in patients enrolling on
phase I trials, but should be restricted to motivated sites with
adequate infrastructure.
•
Post-treatment biopsies can be missed due to clinical
deterioration and other problems, so enrollment must always
exceed the “n” needed for statistical purposes.
•
Regardless of the sample size, most assays exhibit substantial
inter- and intra-tumor variability.
•
Avoid the temptation to link outcome with post-treatment
changes in phase I- the sample sizes are too small to assess
predictive markers.
•
Suggestion: Validate the assay in preclinical models and then
restrict to a more homogenous patient population at/around the
recommended phase II dose, in phase I. (“Part B”)
What Biological Assays CAN Do
• Establish that an agent is pharmacologically
active
• Determine whether an agent is inducing the
expected biological effects
• Potentially establish a “threshold” dose or
exposure for activity
• For more toxic agents, define the “biological
index”
What Biological Assays CANNOT Do
(or have not done to date)
• Establish an effective dose independent of
toxicity
• Rescue an otherwise inactive drug or poor
clinical development plan
Phase I Trials
Questions:
• Is biologically active drug circulating in the patient?
• Are the preclinical PK/biological studies recapitulated in
patients?
• What is the dose range of biological activity?
Phase I Trials: “Part A”- Dose Escalation Phase
Tools:
• Pharmacokinetics.
• Bioassays (ex vivo assays using patient serum or
plasma).
• Surrogate tissue assays (PBMCs, buccal mucosa,
skin).
• ? Tumor tissue biopsies
• ? Biological imaging
Design:
• Multiple dose escalations.
• Diverse patient population.
• Standard endpoints (MTD, toxicity).
Phase I Trials: “Part B”-Cohort Expansion Phase
Questions:
• Does the drug interact with the target (tumor) in the
expected manner?
• Is there a dose-response relationship to the effects?
(if Part B has 1-3 dose levels)
• What is the dose that yields adequate drug exposure,
relevant biological effects, and is well tolerated?
Phase I Trials: “Part B”- Dose Expansion Phase
Tools:
• Assays on tumor tissue using the relevant biological
endpoints.
• Biological imaging.
• Pharmacokinetics to assess PK/PD relationships.
Design:
• More focused patient population- maybe even with 1-2
disease-specific arms.
• 1-3 dose levels.
• Tumor tissue available for assessment.
Part B may also be useful for assessing feasibility of
predictive biomarkers
Recommended Algorithm
“Part A”
Dose Seeking Phase I (Toxicity or PK endpoint)
Identify a dose range: Recommend Highest Tolerable Dose
Biomarkers Optional: Best performed on PBMCs/plasma
“Part B”
Define Active Dose Range
Expanded Phase I Cohort (preferable) or Separate Trial
 Patients/ level, Uniform Population (1+ strata)
Final Dose or Active Dose Range Defined
Phase II Trials
Questions:
• Does the drug reproducibly interact with the target in
the expected manner?
• Is there a relationship between the (baseline or posttreatment) biological marker and clinical outcome?
Phase II Trials
Tools:
• Tumor biopsy- if feasible, or baseline tissue (predictive
biomarkers).
• Surrogate tissue assays.
• Biological imaging.
Design:
• Single patient population.
• Fixed dose level (unless randomized phase II
warranted to explore 2 dose levels).
• Relevant clinical endpoints that include disease
stability.
NCI CTEP Biomarker Guidelines
• CTEP has developed a new Biomarker Review Committee
(BRC) that will review all biomarker components of CTEPsponsored clinical trials
• All LOIs will require BRC approval if they have any of the
following:
• Integral and/or integrated biomarkers (definition
coming up)
• Biomarker assays requesting NCI funding
• Biomarkers that request NCI funding for sample
acquisition
Exploratory biomarkers not requesting NCI funding do not
require BRC approval
NCI CTEP Biomarker Guidelines
• Integral biomarkers: essential for conducting the study as
they define eligibility, stratification, disease monitoring or
study endpoints
• Integrated biomarkers: testing a hypothesis based on
preexisting data and not simply generating hypotheses
• Ideally performed on all patients in a trial/assay already
tested in the disease in question with reproducible
analytic qualities.
• Exploratory biomarkers: May not be performed in all
patients on the trial and collection may be voluntary
Website: http://www.cancer.gov/aboutnci/organization/ccct/funding/BIQSFP/2013Updated-BIQSFP-Announcement
What We Have Not Covered
• Preclinical development of predictive and
pharmacodynamic biomarkers
• Details on functional imaging- preclinical and clinical
• All of the useful ways to integrate biomarkers into
biopsy-driven or disease-specific expanded cohorts
• The increasing use and incorporation of nextgeneration sequencing into early phase trials (usually
for prediction of patient outcome)
• Biomarkers of resistance- increasingly important