gaps between biomarkers and surrogate endpoints: · pdf file1 gaps between biomarkers and...

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Gaps Between Biomarkers andSurrogate Endpoints:

CNS

Hermann FuderTransatlantic Strategies in Early Drug

DevelopmentDüsseldorf, 19-21 February 2006

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Overview

• Definitions Biomarker, Surrogate, ClinicalEndpoint

• Biomarker in Psychiatry• Biomarker in Neurology

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Definition of Biomarker

• A characteristic that is objectively measured andevaluated as an indicator of normal biologicprocesses, pathogenic processes, or pharmacologicresponses to a therapeutic intervention

• FDA Pharmacogenomics Guidance definespossible, probable and known valid biomarkercategories depending on available scientificinformation on the marker

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Unintended effectUnintended effectAffected by interventionAffected by interventionNot affected by interventionNot affected by intervention

Not usefulNot useful

Ideal markerIdeal marker

Partly usefulPartly useful

Confusing markerConfusing marker

Biomarker Validation

WellWellWell DiseaseDiseaseDisease

BiomarkerBiomarkerBiomarker

WellWellWell DiseaseDiseaseDisease

BiomarkerBiomarkerBiomarker

WellWellWell DiseaseDiseaseDisease

BiomarkerBiomarkerBiomarker

WellWellWell DiseaseDiseaseDisease

BiomarkerBiomarkerBiomarker

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Definition ofSurrogate Endpoint

• A biomarker intended to substitute for aclinical endpoint. A surrogate endpoint isexpected to predict clinical benefit (or harm, orlack of benefit) based on epidemiologic,therapeutic, pathophysiologic or otherscientific evidence

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Surrogates

• to increase the likelihood of providing beneficialeffects on clinical efficacy endpoints

• validity for a given treatment not necessarilyapplicable for another treatment with differentmechanism of action

• do in most cases not replace clinical efficacyendpoints in definitive trials (Phase III)

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Definition ofClinical Endpoint

• A characteristic or variable that reflects how apatient feels, functions or survives

• Except for survival, all these involveintermediary measurement

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Clinical Effects of AtypicalAntipsychotics

• Clinical efficacy in schizophrenic patients (acutetreatment of psychotic episodes and relapseprevention)– Positive and Negative Symptoms Scale (PANSS)

• % patients responding by reduction in PANSS by 30%

– Clinical Global Impression (CGI)

• Safety/Tolerability– ESRS, BAS, AIMS, prolactin, QTc, weight, glucose

and lipid metabolism

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Biomarkers for Antipsychotics

• Biomarkers in early clinical development– PET (« local PK in area of interest in CNS »):

• D2 and 5-HT2 receptor blockade for atypicals

– Quantitative EEG– prolactin

• Surrogates– ?

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PET Study for CNSReceptor Occupancy

PET Images with 11C - Raclopride Binding to D2 Receptorsin Human BrainBefore Aripiprazole During Aripiprazole During Aripiprazole

2 mg/day, 14 days 30mg/day, 14 days

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Changes in qEEG by New Atypical

long lasting action

no sedation

rapid onset

rapid onset

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qEEG in Healthy Subjectsand Answers to Questions

• Penetration of blood brain barrier?• Dose response relationship, minimum CNS active dose?• Time course of pharmacodynamic effect?• PK/PD?• Sedation?• Limitations:

– Healthy subjects very sensitive to low doses of antipsychotics– Applicability to patients unclear– Status of validation incomplete– Relevance of qEEG for new modes of actions beyond typical or

atypical antipsychotics unclear

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Prolactin: a Useful Biomarkerfor Antipsychotic Efficacy?

from de Visser et al. 2001

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Clinical AntipsychoticTrials of Intervention

Effectiveness (CATIE)

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CATIE: AntipsychoticsInvestigated and Doses

• Mean modal doses/day(total number of schizophrenic patients:1493)

– olanzapine 20 mg– perphenazine 21 mg– quetiapine 543 mg– risperidone 4 mg– ziprasidone 113 mg

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Outcome CATIE: Time toDiscontinuation of Treatment

longer for olanzapine than for quetiapine, risperidone,perphenazine, and ziprasidone regarding:

• for any cause• for lack of efficacy• owing to patient’s decision

no difference between the drugs:• owing to intolerable side effects

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Other AEs

• Prolactin increase: only with risperidone, notfor other antipsychotics

• Weight gain ≥7%: olanzapine 30%, others 7-16%

• Risk Metabolic Syndrome: more witholanzapine than others, ziprasidone reducedthe risk

• QTc prolongation: no differences

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Prolactin: a Useful Biomarkerfor Antipsychotic Efficacy?

• Apparently not of predictive value for clinicalefficacy under real life conditions of treatmentwith most 2nd generation antipsychotics, at bestperhaps for some D2 receptor blockers

• Indicator for supramaximal doses of someantipsychotics?

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NK1 Antagonists forDepression?

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NK1 Antagonist in CNSIndications

• Aprepitant (MK-0869) successfully registered and launched inUS 2003 against nausea and emesis in cancer patients underemetogenic chemotherapy (Emend™)

• Aprepitant under evaluation for depression in Phase III basedon a large positive Phase II trial and a small negative Phase IItrial with lower dose

• Dosing in Phase III trials based on results from PET studies(determination of CNS NK1 receptor occupancy over time) andPhase II trial with positive outcome

• Expectation/hope: first new antidepression concept/target in 10years

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NK1 ReceptorOccupancy in

CNS:Displacementby Aprepitant

• Frank & Hargreaves 2003

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Aprepitant for Depression

• Nov. 12, 2003--Merck & Co., Inc. announced todaythat it is discontinuing its Phase III clinicaldevelopment program for its substance P antagonistinvestigational product, MK-0869, for the treatmentof depression.

• The Phase III clinical program was halted because thecompound failed to demonstrate efficacy for thetreatment of depression.

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Are NK1 AntagonistsUseful in Depression?

• Effect on development portfolios of a number of otherpharmaceutical companies?

• Potential reasons for negative outcome of Phase III trials withaprepitant:– Unrelated to aprepitant and other NK1 antagonists:

Antidepressant trials frequently negative (up to 50%)– Related to aprepitant: not effective enough or results too

variable?– Related to all other NK1 antagonist: Will one be shown to be

effective in depression in future trials?• If not: Are CNS NK1 receptors an adequate target in

depression?

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Biomarkers in Neurology

• Multiple Sklerosis– MRI (supportive evidence of benefit for registration and

labelling of interferon-1-ß)• Stroke (entry criteria for infarct size and penumbra; potential

endpoints for intervention studies)– diffusion and perfusion MRI,– perfusion CT

• Alzheimer’s Disease– volumetric MRI,– MR spectroscopy,– FDG-PET,– SPECT,– amyloid PET,– microglial tracers, ß-amyloid, Tau-proteins

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Neuroimaging in CNSDrug Development

Uppoor et al. 2005 (CDER, FDA)Neuroimaging studies in CNS drugs approved

from 1995 to 2004• 106 NDAs approved in Neuropharmacology

Division• 15 (out of 106) included neuroimaging studies• 5 (out of 15) receptor occupancy• 2 (out of 15) support POC