Structural and functional outcomes in animal models of stroke: What do they measure?

Malcolm MacleodUniversity of Edinburgh

The problem …

• The failure of successful translation from animal studies to clinical trials

• Primary endpoint in animal studies is usually a structural outcome

• Primary endpoint in clinical trials is usually a functional outcome

• Is there a relationship, in animals, between structural and functional outcome?

1026

1026 interventions in experimental stroke

1026603

1026 interventions in experimental stroke

Tested in focal ischaemia

1026883374

1026 interventions in experimental stroke

Effective in focal ischaemia

1026883550

97 18

1026 interventions in experimental stroke

Tested in clinical trial

1026883550

97 171 3

1026 interventions in experimental stroke

Effective in clinical trial

Progress to date:

• Better understanding of the limited internal validity of animal studies

• Better understanding of publication bias

• Better understanding of the limited external validity of animal studies

Methodological approach

• Written review protocol – hypothesis, inclusion and exclusion criteria, analyses prespecified

• Standardised search strategy – 3 online databases, conference abstracts, dual screening

• Data extraction to bespoke database/analysis tool

• Random effects weighted mean difference stratified meta-analysis or meta-regression

• Publication bias by Funnel plot, Egger regression, Trim and Fill

CAMARADES

Disease model Interventions

Publications Experiments Animals

Focal cerebral ischaemia

17 556 1439 20690

Intracerebral Haemorrhage

62 97 407 3647

Experimental Allergic Encephalomyelitis

36 (1717) 123 (1152) 438 7224

Transgenic models of AD

207 612 1794 22000

Parkinson’s Disease

28 57 303 2245

Spinal Cord Injury

34 69 331 3596

Total 2543 4712 59402

Internal validity

9 publications, 29 experiments, 408 animals 44% (35-53%) improvement in outcome

Publication Bias

External validity

NXY-059

“Normal”BPEffi

cacy

tPA

“Normal”BP

Effi

cacy

External validity – good practice

Surrogate outcomes and biomarkers

Surrogate outcomes and biomarkers

Surrogate outcome

Functional outcome

Can animal models help?

• In animal studies– Does structural outcome predict functional

outcome?– Does this relationship hold across interventions?

• Inclusion criteria: – Reports of the efficacy of a candidate stroke

drug in an animal model of focal cerebral ischaemia

– Structural and functional outcome reported from the same cohort of animals

– Simultaneous measurement of structural and functional outcome

Data

1047

257

16

71

131

71

21

25

110

13

110

12

24

18

26

9

Experiments reporting any

outcome

299TOTAL

58Stem Cells

11Other Thrombolytics

20Nicotinamide

54Thrombolytics

16NOS Inhibitors

8FK506

0NOS Donors

42Hypothermia

4Melatonin

51Growth Factors

3NXY-059

7Enriched Environment

16Tirilazad

8Minocycline

1IL1-RA

Experiments reporting structural and

functional outcomesDrug Group

Raw correlation

Raw correlation coefficient = 0.439

adjusted r2=0.301

∆ F

un

ctio

nal

ou

tco

me

∆ Structural outcome

Better

Better

Worse

Structural Outcome

Coefficient 95% CI

Constant (tPA) 23.9 17.1-30.7

Other lytics 19.3 2.93-35.7

FK506 19.9 1.62-38.1

Tirilazad 21.4 7.91-34.9

Nicotinamide 23.4 6.75-40.2

Hypothermia 26.1 15.9-36.4

NXY 059 29.1 0.43-57.8

Delay to assessment (days) -0.01 -0.02-0.00

% improvement (SO) = 23.9 + f(drug) -0.01*(days to assessment)

Adjusted r2 = 0.24

Functional Outcome

Coefficient 95% CI

Structural outcome (Infarct Volume) 0.47 0.37 to 0.56

Stem cells 10.0 1.9 to 18.1

Hypothermia 11.2 2.4 to 19.9

FK506 18.4 4.2 to 32.6

Minocycline 18.5 5.1 to 31.9

Nicotinamide 19.9 10.1 to 29.7

NOS Inhibitors 20.7 10.4 to 30.9

Tirilazad 22.9 8.1 to 37.9

Delay to assessment (days) 0.58 0.36 to 0.82

Delay to treatment (hours) -0.96 -1.44 to -0.48

% improvement (FO) = 0.47*SO + f(drug) + 0.58*(days to assessment) – 0.96*(hours to drug administration)

Adjusted r2 = 0.56

Summary

Structural Outcome Functional Outcome Independent effects on both

tPA Stem cells FK506

Other lytics Minocycline Tirilazad

NXY 059 NOS Inhibition Nicotinamide

Hypothermia

Delay to treatment (-ve)Delay to assessment

(-ve SO, +ve FO)

Lesion Structural Outcome Functional Outcome

Summary

Structural Outcome Functional Outcome Independent effects on both

tPA Stem cells FK506

Other lytics Minocycline Tirilazad

NXY 059 NOS Inhibition Nicotinamide

Hypothermia

Delay to treatment (-ve)Delay to assessment

(-ve SO, +ve FO)

Lesion Structural Outcome Functional Outcome

Summary

Structural Outcome Functional Outcome Independent effects on both

tPA Stem cells FK506

Other lytics Minocycline Tirilazad

NXY 059 NOS Inhibition Nicotinamide

Hypothermia

Delay to treatment (-ve)Delay to assessment

(-ve SO, +ve FO)

Lesion Structural Outcome Functional Outcome

Summary

Structural Outcome Functional Outcome Independent effects on both

tPA Stem cells FK506

Other lytics Minocycline Tirilazad

NXY 059 NOS Inhibition Nicotinamide

Hypothermia

Delay to treatment (-ve)Delay to assessment

(-ve SO, +ve FO)

Lesion Structural Outcome Functional Outcome

DISCUSSION

• Structural outcome explains around 30% of the variation in functional outcome

• Crucially, this relationship is different for different interventions

• Surrogate outcome measures in Phase II are likely to be intervention specific rather than disease specific

• Nonetheless, this approach might help with rational selection of combination therapies

Acknowledgements

• CAMARADES collaborators– Bart van der Worp (Hypothermia)– Philip Bath (NOS Inhibitors)– Jen Lees/ David Howells/ Simon Koblar

(Stem cells)

• NHS Lothian R&D Infrastructure Funding

• Edinburgh MRC Trials Methodology Hub