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

interventions in experimental stroke

interventions in experimental stroke Tested in focal ischaemia

interventions in experimental stroke Effective in focal ischaemia

interventions in experimental stroke Tested in clinical trial

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 modelInterventionsPublicationsExperimentsAnimals Focal cerebral ischaemia Intracerebral Haemorrhage Experimental Allergic Encephalomyelitis 36 (1717)123 (1152) Transgenic models of AD Parkinsons Disease Spinal Cord Injury Total

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

Publication Bias

External validity NXY-059 Normal BP Efficacy tPA Normal BP Efficacy

External validity – good practice

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 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 outcomes Drug Group

Raw correlation Raw correlation coefficient = adjusted r 2 =0.301 Functional outcome Structural outcome Better Worse

Structural Outcome Coefficient95% CI Constant (tPA) Other lytics FK Tirilazad Nicotinamide Hypothermia NXY Delay to assessment (days) % improvement (SO) = f(drug) -0.01*(days to assessment) Adjusted r 2 = 0.24

Functional Outcome Coefficient95% CI Structural outcome (Infarct Volume) to 0.56 Stem cells to 18.1 Hypothermia to 19.9 FK to 32.6 Minocycline to 31.9 Nicotinamide to 29.7 NOS Inhibitors to 30.9 Tirilazad to 37.9 Delay to assessment (days) to 0.82 Delay to treatment (hours) to % improvement (FO) = 0.47*SO + f(drug) *(days to assessment) – 0.96*(hours to drug administration) Adjusted r 2 = 0.56

Summary Structural OutcomeFunctional OutcomeIndependent effects on both tPAStem cellsFK506 Other lyticsMinocyclineTirilazad NXY 059NOS InhibitionNicotinamide Hypothermia Delay to treatment (-ve) Delay to assessment (-ve SO, +ve FO) Lesion Structural Outcome Functional Outcome

Summary Structural OutcomeFunctional OutcomeIndependent effects on both tPAStem cellsFK506 Other lyticsMinocyclineTirilazad NXY 059NOS InhibitionNicotinamide Hypothermia Delay to treatment (-ve) Delay to assessment (-ve SO, +ve FO) Lesion Structural Outcome Functional Outcome

Summary Structural OutcomeFunctional OutcomeIndependent effects on both tPAStem cellsFK506 Other lyticsMinocyclineTirilazad NXY 059NOS InhibitionNicotinamide Hypothermia Delay to treatment (-ve) Delay to assessment (-ve SO, +ve FO) Lesion Structural Outcome Functional Outcome

Summary Structural OutcomeFunctional OutcomeIndependent effects on both tPAStem cellsFK506 Other lyticsMinocyclineTirilazad NXY 059NOS InhibitionNicotinamide 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