Clinical Trials Penny Hogarth, MD OHSU Department of Neurology April 6th, 2007

Clinical Trials

Penny Hogarth, MD

OHSU Department of Neurology

April 6th, 2007

What is a clinical trial?

• A clinical trial is a tool for testing a drug, device or technique

Why do a clinical trial?

• To answer a clinical problem

• To gain new knowledge about a new or established treatment

• To support an application for government regulatory approval

• To support the marketing of a drug, device, or technique

Guiding Principles

• Ethics

• Scientific validity & integrity

• Medical relevance

• Regulatory & medico-legal considerations

• Cost

Guiding Principles

• Start with a hypothesis– Put in the form of a statement

• Turn it into a question– The question must be “answerable”– This forms the basis of the study’s “objectives”

Observational studies

• Case reports

• Case-control studies

• Cohort studies

Case-control studies

• Retrospective• Subjects classified on basis of outcome,

with prior exposure status determined after outcome

• Case = those with outcome of interest• Control = those without outcome of interest

Cohort studies

• Prospective / longitudinal / concurrent

• Subjects classified on basis of exposure to some risk factor of interest and followed to determine outcome

• Most rigorous of observational studies

Interventional studies

• Cross-over trials– Subject acts as own control– Decreases variability

• Parallel group trials

Study population

Active treatment

Control treatment

Control treatment

Active treatment

Random assignment

washout

Study population

Active treatment

Control treatment

YES YES

Random assignment

NO NOOutcome of interest

Follow-up period

Phase I studies

• Early human use of drug• Often in normal subjects, rather than those

with disease of interest• Mainly aimed at establishing tolerated dose

range, PK / PD, acute toxicity of compound• Usually open-label, no control groups• Small number of subjects: usually 10-100• Days to weeks long

Phase II studies

• In human subjects with disease of interest

• Establishing safety, tolerability of compound

• Preliminary measures of efficacy

• Usually controlled, randomized, blinded

• Larger numbers of subjects: ~100-300

• Weeks to months long

Phase III studies

• In subjects with disease of interest• Establishing efficacy, long-term safety and

tolerability• Raandomized, controlled, blinded• Comparator may be placebo, or standard

treatment• Large numbers of subjects: 100s - 1000s• Months to years long

Phase IV studies

• “Post-marketing” studies

• Long-term risks, benefits, optimal use

Anatomy of a study protocol

• Introduction and study rationale

• Study objectives

• Overall study design / study flowsheet

• Eligibility criteria

• Specific study procedures

• Sample size calculations / data analysis plan

• Ethical considerations

Common errors in trial design

• Question to be answered unclear

• Population too broadly or narrowly defined

• Outcome measures not quantifiable, or not relevant

• Controls inadequate

• Measures to protect against bias inadequate

• Study inadequately powered

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From genetics to treatments

• Recognize and describe the phenotype• Identify the gene• Make an animal model• Use the model to understand the pathophysiology

of the disease• Develop rational therapeutics based on the

pathophysiology• Test in animal models• Test in humans

From genetics to treatments

• Recognize and describe the phenotype• Identify the gene• Make an animal model• Use the model to understand the pathophysiology

of the disease• Develop rational therapeutics based on the

pathophysiology• Test in animal models• Test in humans

“There are three marked peculiarities of this disease: its hereditary nature, a tendency to insanity and suicide, and its manifesting itself as a grave disease only in adult life…..” George Huntington, 1872

Huntington Disease

• Progressive neurodegenerative disorder– Movement disorder– Cognitive decline– Psychiatric, behavioral disturbances

• Average age of onset ~ 38 yo• < 10% juvenile onset < 20 yo• Late onset cases probably under-recognized

From genetics to treatments

• Recognize and describe the phenotype

• Identify the gene• Make an animal model• Use the model to understand the pathophysiology

of the disease• Develop rational therapeutics based on the

pathophysiology• Test in animal models• Test in humans

Gene discovery: Venezuela 1993

Genetics of HD

• Autosomal dominant inheritance• Expanded and unstable trinucleotide repeat

(CAG) on short arm of chromosome 4 expanded polyglutamine tract in mutant protein

• Age dependent penetrance

From genetics to treatments

• Recognize and describe the phenotype• Identify the gene

• Make an animal model• Use the model to understand the pathophysiology

of the disease• Develop rational therapeutics based on the

pathophysiology• Test in animal models• Test in humans

Animal models: 1996

• Transgenic mice• Drosophila • C. elegans

From genetics to treatments

• Recognize and describe the phenotype• Identify the gene

• Make an animal model• Use the model to understand the pathophysiology

of the disease• Develop rational therapeutics based on the

pathophysiology• Test in animal models• Test in humans

gln-gln-gln-gln

• Transcriptional dysregulationTranscriptional dysregulation

• Mitochondrial dysfunctionMitochondrial dysfunction

• Proteasome dysfunctionProteasome dysfunction

Aggregate formationAggregate formation

caspasescaspases

gln-gln-gln

From genetics to treatments

• Recognize and describe the phenotype• Identify the gene• Make an animal model• Use the model to understand the pathophysiology

of the disease

• Develop rational therapeutics based on the pathophysiology

• Test in animal models• Test in humans

From genetics to treatments

• Recognize and describe the phenotype• Identify the gene• Make an animal model• Use the model to understand the pathophysiology

of the disease• Develop rational therapeutics based on the

pathophysiology

• Test in animal models• Test in humans

HDAC inhibitors in Drosophila

Drosophila HD model treated with HDAC inhibitors SAHA and butyrate show rescue of neurodegenerative process

Steffan et al., Nature (2001) 413:739

HD Normal Tx HD

HDAC Inhibitor SPB ameliorates R6/2 HD mouse phenotype

• Extended survival in dose-dependent fashion

• Improved motor performance

• Delayed neuropath sequelae

Ferrante et al. J. Neuroscience 23(28):94

From genetics to treatments

• Recognize and describe the phenotype• Identify the gene• Make an animal model• Use the model to understand the pathophysiology

of the disease• Develop rational therapeutics based on the

pathophysiology• Test in animal models

• Test in humans

SPB in HD

• Dose-finding study of SPB completed here at OHSU

• Pilot study of promising gene expression biomarker

• Multi-center phase II study just comleted

Clinical trial design in HD

• Individuals carrying HD gene spend ~2/3 life pre-symptomatic, ~1/3 symptomatic

• If neuroprotective treatment identified, when should it be started?

• How can we measure efficacy of putative neuroprotective treatment in pre-symptomatic individuals?

Clinical trial design in HD

• HD gene is perfect “trait” marker• Current clinical measures are imperfect “state”

markers• “Delay of symptom onset” as trial outcome

measure inaccurate and expensive

• Search for biomarkers, surrogate markers a high priority

What is a clinical endpoint?

• A measure that reflects how a subject feels, functions or survives

• Distinct measures used in a clinical trial that reflect the effect of a therapeutic intervention– death, BP reduction, self-report of pain

– In pre-sx HD, onset of signs / sx

What is a biomarker?

“A characteristic that is objectively measured and evaluated as an indicator of normal biologic processes, pathogenic processes, or pharmacologic responses to a therapeutic intervention.” (Downing, 2000)

“Marker of disease severity that reflects underlying pathogenesis and predicts clinical events in the absence of treatment, thus establishing the biological plausibility of the marker.” (Mildvan, 2000)

What is a surrogate endpoint?

Characterization of a biomarker as a surrogate endpoint requires it to be “reasonably likely, based on epidemiologic therapeutic, pathophysiologic, or other evidence to predict clinical benefit.” (FDA, 1997)

Examples: ↑ CD4 Cell Count in HIV

MRI Scans in HD

Normal Subject: Age 38 HD Subject: Age 31

Globus Pallidus

PutamenCaudate

Can we use striatal volume as biomarker / surrogate endpoint in HD?

Can be objectively measured– High inter- intra-rater reliability

• Reflects pathogenic process– Striatal volume decreased in pre-sx subjects– Striatal volume decreases as approach onset sx– Longitudinal change can be detected over relatively

short time

• Predicts clinical events– Rate of change significant 10-12 years prior to sx onset– Striatal volume can predict incident cases

Striatal volume decreases as onset approaches

+1 s.d. for 19 controls

-1 s.d. for 19controls

Mean Volume for 19 controls

Caudate volume

Putamen volume

< 10 10-15 15-20 20-25 >25(N = 67) (N = 67) (N = 42) (N = 22) (N = 16) Years to Onset (current estimate)

Mean caudate volume for controls

Mean putamen volume for controls

Striatal volume predicts clinical events

• Putamen and caudate volumes are about ½ of normal volume at the time of diagnosis

• Functioning can remain normal even as basal ganglia volumes are declining

• All subjects with caudate volume < 4.6 cc were symptomatic; all with caudate volume > 5.3cc were presymptomatic

• All subjects with putamen volume < 3.3cc were symptomatic; all with putamen > 5.1cc were asymptomatic

Application of striatal volume as biomarker

““may be applied as a stratification variable in controlled may be applied as a stratification variable in controlled trials, distinguishing populations with varying degrees of risk trials, distinguishing populations with varying degrees of risk of disease.”of disease.”(Mildvan, 2000)(Mildvan, 2000)

Biomarkers have several valuable applications, including:Biomarkers have several valuable applications, including: use as a diagnostic tooluse as a diagnostic tool use as a tool for staging diseaseuse as a tool for staging disease use as an indicator of diseaseuse as an indicator of disease use to predict and monitor clinical response to inuse to predict and monitor clinical response to in

intervention (Downing, 2000) intervention (Downing, 2000)

Striatal volumes as surrogate endpoint

• No existing good clinical measures for pre-sx subjects

• Can be used in far-from-onset subjects, for whom onset is not feasible measure

• Can use data from all subjects, not just incident cases

• No practice effects, no placebo effects• Relatively small study sample sizes needed

Striatal volumes as surrogate endpoint

• Assume for sample size calculation:– Treatment effective in reducing atrophy by one-half– Trial included only those subjects whose estimated

onset was <12 years from the initiation of the trial– Trial would be approximately 30 months duration

• Would need approximately 84 presymptomatic subjects per group

– MRI striatal volumes can be considered a biomarker

– MRI striatal volumes can be used • to select cases for future clinical trial• to determine when the first neurobiological changes of

HD begin

– More evidence needed to consider MRI striatal volume as a surrogate endpoint???

– Need to be ready with a cost-effective method that is reliable and valid for future clinical trials

– Would likely be used in combination with other proposed biomarkers / surrogate markers

Acknowledgement

Elizabeth Aylward, PhD

University of Washington

Seattle, WA