Of Mice and Men: How Temporal and Other Biological Factors Affect Interpretability of Animal Models

March 1, 2013Gene G. Kinney, Ph.D.Prothena Biosciences

American Society for Experimental NeuroTherapeutics | 15th Annual Meeting

Disclosure

Name of Commercial Interest

• Bristol-Myers Squibb; Merck & Co.; Elan Pharmaceuticals; Janssen Alzheimer Immunotherapy

• Prothena Biosciences, Inc.

American Society for Experimental NeuroTherapeutics | 15th Annual Meeting

Type of Financial Relationship

• Former employee and current shareholder (Elan and Bristol-Myers Squibb)

• Current employee and shareholder

Learning Objectives• Using animal models of Alzheimer’s disease and

anti-Aβ immunotherapy as a case study, illustrate:

• The strengths and limitations of animal model results for predicting clinical efficacy

• The importance of iterative translation during clinical development

American Society for Experimental NeuroTherapeutics | 15th Annual Meeting

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Exemplifying the obvious• Most cases of Alzheimer’s disease

are diagnosed§ at age ≥ 65 yrs with a median survival of 4-8 years post-diagnosis

• It is generally believed that Alzheimer’s disease pathology can begin ≥ 20 yrs prior to diagnosis

• In a “modestly aggressive” mouse model of AD (PDAPP) the average age for onset of pathology is ~12 months of age*

• The average lifespan of a PDAPP mouse is ~18-32 mos

* some deficits generally attributable to soluble Aβ aggregates are observed pre-pathology

§Traditionally a differential diagnosis based on dementia. Recent move to more biologically-based definitions.

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Alzheimer’s disease biology• First identified in 1907 by Alois Alzheimer

based on post-mortem evaluation of demented patients– Extracellular plaques and intracellular tangles;

but cause or consequence?

Amyloid β

Tau

plaques

tangles Kinase inhibitors (phosphorylation)Microtubule stabilization

Production inhibitorsImmunotherapeuticsClearance enhancersAnti-aggregate and “plaque buster”

Brunden et al., Nature Reviews Drug Discovery 8, 783-793 (October 2009)

Auguste D

Alois Alzheimer

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Development of the PDAPP mouse model enabled initial immunotherapy studies

• Focus on pathological contributions to disease

• Development of the first plaque forming mouse model was enabling for the testing of putative therapeutic approaches designed to be “disease modifying”

Plaque formation

Loss of synaptic integrity

Non-Tg PDAPP

Loss of neuronal integrity

Games et al., Nature, 373:523, 1995

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Anti-Aβ immunotherapy: Background• Anti-Aβ immunotherapy proposed as a therapeutic approach for the

removal of Aβ from the CNS (Schenk et al, Nature, 400:173, 1999)

UTC = untreated controlsSAP = immunization with serum amyloid PPDAPP mice immunized between 6 wks and 13 mos

ImmunizedVehicle

Reductions in dystrophic neurites and astrogliosis also observed following immunization

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Translational aspects of anti-Aβ immunotherapy

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Anti-Aβ immunotherapy: Background• Elan/Wyeth anti-Aβ vaccine (AN-1792) demonstrated activity

on some endpoints in clinical trials– Reduction of senile plaque and cognitive benefit on NTB

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Anti-Aβ immunotherapy: Background

• AN-1792 trials were discontinued following reports of meningoencephalitis in ~6% of the active treatment group– T-cell mediated response to the self-antigen is a likely cause

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Translational aspects of anti-Aβ immunotherapy

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Next generation approaches include passive and active immunization

Schenk, Nature Reviews Neuroscience 3, 824-828 (October 2002)

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TY11/15

3D6

Median Aβ burden values following passive immunization: 6 mo treatment

10.23%

0.69%

Treatment % control

TY11/15 100

3D6 7

PDAPP mice (N>30/group) treated with 3 or 10mg/kg/week at 12-18 months of age

Similar effects on:• Neuritic dystrophy• Brain Aβ levels (ELISA)

Seubert et al., Neurodegenerative Dis, 5:65, 2008

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The discovery of the Pittsburgh Compound-B (PiB) tracer allowed for PET imaging of amyloid deposition in AD

patients

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Bapineuzumab decreases amyloid burden in human subjects using [11C] PiB PET imaging

Rinne JO et al., Lancet Neurol., 9:363, 2010

• N=28 patients with mild to moderate AD

• Randomized to intravenous bapineuzumab (N=20) or placebo (N=8) in three ascending dose cohorts (0.5, 1.0, or 2.0 mg/kg)

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MRI observations consistent with transient edemic events were observed following Bapineuzumab treatment

Salloway, S. et al. Neurology 2009;73:2061-2070

• 69-year-old APOE ε4 homozygote Female• Treated with bapineuzumab 1.0 mg/kg IV. Remained asymptomatic despite the

appearance of multiple areas of ARIA evident on MRI. Patient was redosed at 0.5 mg/kg and followed for over 2 years without recurrence of ARIA

• Reported by Salloway et al., 2009 (Phase 2 data)• Anti-Aβ edemic events appear sensitive to Bapineuzumab dose and APOE ε4

gene dose• Events were transient in some cases and did not recur following redosing in a

limited data set

Clinical evidence suggests that ARIA may be related to Aβ mobilization

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Translational aspects of anti-Aβ immunotherapy

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Preclinical studies designed to further understand the biology of ARIA

• The brain capillary network appears to be involved in antibody induced amyloid removal

• Aβ deposition on brain vasculature may impair vessel integrity, recovery following removal of vascular Aβ

• Key proteins involved in resolution of edemic events may be modulated during the process of immunotherapy induced clearance of Aβ

C.

PDAPP

Wild-typeWild-type

Vascular Perimeter

PDAPP

Wild-typeWild-type

Vascular Perimeter

A. Wild Type B. PDAPP

PDAPP – TY1115(9 months)

PDAPP – 3D6(9 months)

Wild Type

Zago et al., Alz. & Dement., In Press

Normal Vascular Aβ

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More work to do

– MMSE; ADAS-Cog; CDR-SB etc.

How is the disease defined?– Dementia, Pathology, mix?

Staging of disease

- Spatial reference learning / memory; Episodic memory

Alzheimer’s disease hAPP Tg mouse models

Stage at Diagnosis

Generally believed to be advanced pathology at point of diagnosis

Not applicable; diagnosis based on pathological involvement

Optimal point of intervention

Extensive efforts to identify earlier intervention times

• All currently completed disease modification trials have studied mild/moderate patients

Data suggests that earlier intervention is more effective

• Late intervention may still be effective for some experimental approaches

Alzheimer’s disease hAPP Tg mouse models

DementiaAssessed by broad based cognitive tools that may also incorporate function (e.g., MMSE, ADAS-Cog; CDR-SB); mixed dementia also possible

Models are primarily driven by pathology endpoints; assessment of cognition tends to be very precise (e.g., spatial reference learning/memory; episodic memory, etc.)

Pathology Likely mixed (e.g., tau, α-synuclein, etc)Homogenous population, pathology driven in specific tissues through use of promoters; often involves point mutations for more aggressive phenotype

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Even more work to do

– MMSE; ADAS-Cog; CDR-SB etc.

How do key aspects of intervention therapy translate?– Dementia, Pathology, mix?

- Spatial reference learning / memory; Episodic memory

Alzheimer’s disease hAPP Tg mouse models

Magnitude of insol. Aβ reduction

Modest reduction from baseline in treated patients. Continued accumulation in placebo patients.

~70 to ≥90% reductions depending on time of intervention relative to pathology onset

Dose Level Dose of bapineuzumab (and other agents?) may be limited by ARIA

Clear relationship between dose level, time of intervention and duration of treatment

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Contextual Fear Conditioning has been developed as a sensitive functional cognitive measure

Comery et al., J. Neurosci. 2005;25:8898-8902

1mAmp 1mAmp

120s 2s 120s 2s 30s

Training (Day 1) Context Shock

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Common Clinical Assessment Tools

http://www.mdanderson.org/publications/conquest/issues/2008-fall/old-drugs-new-possibilities-conquest-fall-2008-old-drugs-new-possibilities.htmlhttp://ginny-livingwithlyme.blogspot.com/2012/10/spinal-tap-3.htmlhttp://www.nimh.nih.gov/images/pubs/neuro-pet.jpg

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Summary• Although many (if not most) human diseases cannot be fully recapitulated by

animal models, key aspects of the disease process are reproduced– Key breakthroughs in biological understanding of the disease processes– Useful models for testing interventional therapy

• Animal models are most effectively utilized when there is a full understanding of the limitations around the translation of the models to human disease

– How is “efficacy” defined both pre-clinically and clinically– Clinical trial design limitations must be considered

• Heterogeneity of human subjects• Limitations around invasive endpoint assessment• Potential disconnect between “biological” and “pathological” disease definitions

• Clinical development will often result in unpredicted findings necessitating iterative translational approaches

– AN-1792 immunization in AD patients resulted in meningoencephalitis in ~6% of the active treatment group

• New approaches to avoid Aβ directed T-cell responses are being tested clinically (passive and active immunization)

– Reports of radiologically identified edemic events following passive immunization have led to additional preclinical studies using the PDAPP mouse model

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Acknowledgements

Elan Pharmaceuticals / Prothena Biosciences / Janssen AI

Robin Barbour Bob BrashearManuel Buttini Ming ChenDora Games Henry GrajedaMichael Grundman Terry GuidoStefan Heylen Karen KhanMike Lee Enchi LiuRuth Motter Dale SchenkSally Schroeter Peter SeubertEric Yuen Wagner Zago

Wyeth / PfizerDavinder GillSteven Jacobsen Tom ComeryMenelas Pangalos