Tim Ashwood

Animal models of stroke: do they have value for discovering neuroprotective agents?

There has been a series of high-profile failures of drugs in clinical trials of acute ischaemic stroke that were designed to meet criteria necessary for drug regulatory approval. This has, again, called into question the value of animal models for identifying effective neuroprotective agents. Here, we review evidence that physiological changes (reperfusion, hyperglycaemia, hypothermia and blood pressure) produce comparable changes in outcome in both animal models and human stroke patients, which indicates that the models should identify clinically effective neuroprotective agents. We suggest that most clinical failures have occurred because compounds were administered differently in animal and clinical studies. We review earlier guidelines on the information that is necessary from preclinical studies before a compound enters clinical trials, and propose modifications to these guidelines.

Safety and Tolerability of NXY-059 for Acute Intracerebral Hemorrhage The CHANT Trial

Background and Purpose— NXY-059 is a free radical-trapping neuroprotectant developed for use in acute ischemic stroke. To facilitate prompt administration of treatment, potentially before neuroimaging, we investigated the safety of NXY-059 in patients with intracerebral hemorrhage (ICH). Methods— We randomized 607 patients within 6 hours of acute ICH to receive 2270 mg intravenous NXY-059 over 1 hour and then up to 960 mg/h over 71 hours, or matching placebo, in addition to standard care. The primary outcome was safety: the mortality and the frequency of adverse events, and the change from baseline for a variety of serum, imaging, and electrophysiological measurements. We also studied the overall distribution of disability scores on the modified Rankin Scale (mRS) and the Barthel index. Results— We treated 300 patients with NXY-059 and 303 with placebo. Treatment groups were well matched for prognostic variables including Glasgow Coma Scale, risk factors, and age. The mean National Institute of Health Stroke Scale score on admission was 14 in both groups. The baseline hemorrhage volume was 22.4±20.1 mL in the NXY-059 group and 23.3±22.8 mL in the placebo group (mean±SD). Most hemorrhages were related to hypertension or anticoagulant use. Mortality was similar in both groups: 20.3% for NXY-059 and 19.8% for placebo-treated patients. The proportion of patients who experienced an adverse event was the same for both groups, whereas for serious adverse events the proportion was slightly higher in the NXY-059 group. However, no pattern emerged to indicate a safety concern. Serum potassium fell transiently in both groups, lower in the NXY-059 group. There were no differences in 3-month function, disability, or neurological deficit scores. The odds ratio for an improved outcome in 3-month mRS scores in the NXY-059 group was 1.01 (95% CI 0.75, 1.35). Conclusions— NXY-059 given within 6 hours of acute ICH has a good safety and tolerability profile, with no adverse effect on important clinical outcomes.

Additional Outcomes and Subgroup Analyses of NXY-059 for Acute Ischemic Stroke in the SAINT I Trial

Background and Purpose— NXY-059 is a free radical-trapping neuroprotectant demonstrated to reduce disability from ischemic stroke. We conducted analyses on additional end points and sensitivity analyses to confirm our findings. Methods— We randomized 1722 patients with acute ischemic stroke to a 72-hour infusion of placebo or intravenous NXY-059 within 6 hours of stroke onset. The primary outcome was disability at 90 days, as measured by the modified Rankin Scale (mRS), a 6-point scale ranging from 0 (no residual symptoms) to 5 (bed-bound, requiring constant care). Additional and exploratory analyses included mRS at 7 and 30 days; subgroup interactions with final mRS; assessments of activities of daily living by Barthel index; and National Institutes of Health Stroke Scale (NIHSS) neurological scores at 7 and 90 days. Results— NXY-059 significantly improved the distribution of the mRS disability score compared with placebo at 7, 30, and 90 days (Cochran-Mantel-Haenszel test P=0.002, 0.004, 0.038, respectively; 90-day common odds ratio 1.20; 95% CI, 1.01 to 1.42). The benefit was not attributable to any specific baseline characteristic, stratification variable or subgroup interaction. Neurological scores were improved at 7 days (odds ratio [OR], 1.46; 95% CI, 1.13, 1.89; P=0.003) and the Barthel index was improved at 7 and 30 days (OR, 1.55; 95% CI, 1.22, 1.98; P<0.0001; OR, 1.27; 95% CI, 1.01, 1.59; P=0.02). Conclusions— NXY-059 within 6 hours of acute ischemic stroke significantly reduced disability. Benefit on neurological scores and activities of daily living was detectable early but not significant at 90 days; however, our trial was underpowered to measure effects on the neurological examination. The benefit on disability is not confounded by interactions and is supported by other outcome measures.

Early impairment in consciousness predicts mortality after hemispheric ischemic stroke.

ObjectiveEarly predictors of poor outcome after acute ischemic stroke may be useful in selecting patients for potentially beneficial but high-risk interventions. DesignCohort study of patients given placebo in a randomized clinical trial. SettingMulticenter trial at 139 U.S. and 14 Canadian hospitals. PatientsA cohort of 564 placebo-treated patients with major anterior circulation ischemic stroke enrolled in the Clomethiazole in Acute Stroke Study-Ischemic Stroke (CLASS-I) trial. Patients did not have significant impairment in consciousness at baseline and were enrolled within 12 hrs of symptom onset. InterventionsProspective data collection of a number of clinical variables including use of a 6-point level of consciousness scale (1 = awake, 6 = no reaction to pain) to measure patients’ level of consciousness at enrollment and 12 additional times during the first 24 hrs after enrollment. The ability of level of consciousness score and additional clinical data to predict 30-day mortality was assessed. Measurements and Main ResultsAt 1 month, 114 of 564 patients (20%) had died. In univariate analysis, factors significantly associated with mortality included older age, white race, higher National Institutes of Health Stroke Scale score, higher serum glucose, atrial fibrillation, and any impairment in level of consciousness (p < .05). After controlling for these factors, increasing level of consciousness score at 3 hrs after enrollment and at all but one subsequent time point was significantly associated with increased mortality (odds ratio, 1.8 per point; 95% confidence interval, 1.2–2.6; p = .003 at 3-hr time point). Maximum level of consciousness score during the initial 24 hrs of monitoring also predicted mortality (odds ratio, 1.9 per point; 95% confidence interval, 1.4–2.5; p < .001). ConclusionThe development of a decreased level of consciousness within the initial hours after stroke onset, as evaluated by a simple six-point scale, is a powerful independent predictor of mortality after major anterior circulation ischemic stroke.

Rapid decline in episodic memory in healthy older adults with high amyloid-β.

High levels of amyloid-β (Aβ) have been associated with greater rates of decline in episodic memory over 18 months in healthy older adults. Serial assessments over shorter time intervals may facilitate earlier detection of Aβ-related memory decline in healthy older adults. In forty-four healthy older adults enrolled in the Australian Imaging, Biomarkers and Lifestyle Rate of Change Sub-Study, we compared rates of change in cognition over six months in healthy older adults with high and low levels of Aβ. High Aβ was associated with greater decline in episodic memory measures over 6 months in healthy older adults.

Three-month stability of the cogstate brief battery in healthy older adults, mild cognitive impairment, and alzheimer's disease: Results from the Australian imaging, biomarkers, and lifestyle-rate of change substudy (AIBL-ROCS)

Large prospective studies of Alzheimers disease (AD) have sought to understand the pathological evolution of AD and factors that may influence the rate of disease progression. Estimates of rates of cognitive change are available for 12 or 24 months, but not for shorter time frames (e.g., 3 or 6 months). Most clinical drug trials seeking to reduce or modify AD symptoms have been conducted over 12- or 24-week periods. As such, we aimed to characterize the performance of a group of healthy older adults, adults with amnestic mild cognitive impairment (aMCI), and adults with AD on the CogState battery of tests over short test-retest intervals. This study recruited 105 healthy older adults, 48 adults with aMCI, and 42 adults with AD from the Australian Imaging, Biomarkers, and Lifestyle study and administered the CogState battery monthly over 3 months. The CogState battery of tests showed high test-retest reliability and stability in all clinical groups when participants were assessed over 3 months. When considered at baseline, the CogState battery of tests was able to detect AD-related cognitive impairment. The data provide important estimates of the reliability, stability, and variability of each cognitive test in healthy older adults, adults with aMCI, and adults with AD. This may potentially be used to inform future estimates of cognitive change in clinical trials.

Effects of AZD3480 on cognition in patients with mild-to-moderate Alzheimer's disease: a phase IIb dose-finding study

AZD3480 is a selective agonist of the central α4β2 and α2β2 neuronal nicotinic cholinergic receptors (NNRs). Its effects on cognition were investigated in 567 patients with mild-to-moderate Alzheimers disease (AD) (Mini Mental State Examination [MMSE] 12-26). Mean baseline MMSE was 21 (SD ± 3.7), with 61% of patients having mild disease (MMSE 21-26). Mean age was 74 (range 58-85) years. Patients were randomized to one of 5 treatment groups: AZD3480 5 mg, 20 mg or 35/100 mg, donepezil 10 mg (active comparator) or placebo, and treated once daily for 12 weeks. The primary outcome measure was change from baseline at Week 12 on the AD Assessment Scale-Cognitive Subscale (ADAS-Cog). Neither AZD3480 nor donepezil showed a statistically significant improvement versus placebo on ADAS-Cog. Improvements in a number of secondary outcome measures (MMSE, AD Cooperative Study-Clinical Global Impression of Change (ADCS-CGIC) and Disability Assessment for Dementia [DAD]) were observed for AZD3480 and for donepezil. A post-hoc analysis on ADAS-Cog, excluding patients with very mild AD (MMSE 25-26) indicated improvement versus placebo for AZD3480 20 mg (-1.4, 95% CI: -3.0; 0.2) and donepezil (-1.0, 95% CI: -2.3; 0.3). AZD3480 was well tolerated. The study did not meet proof of concept criteria: since neither AZD3480 nor donepezil were statistically significantly superior to placebo on ADAS-Cog and was considered to be inconclusive. Further studies are required to determine the therapeutic potential of stimulating α4β2 receptors with NNRs in AD patients.

Brain penetration of the novel free radical trapping neuroprotectant NXY-059 in rats subjected to permanent focal ischemia

The penetration of the free radical trapping neuroprotectant NXY-059 into the brain has been examined in rats subjected to permanent middle cerebral artery occlusion (pMCAO). NXY-059 (125 mg/kg bolus followed by 125 mg/kg/h) was infused for 4 h 45 min starting 15 min after right pMCAO or sham operation. At 5 h, there was a similar plasma total NXY-059 concentration (micromol/L) in both groups [sham: 623 +/- 44 (6); pMCAO: 605 +/- 43 (5)] and a similar drug concentration (nmol/g) in the right cortex [sham: 6.92 +/- 1.05 (6); pMCAO: 6.14 +/- 2.18 (6)]. A subsequent experiment in normal rats, infusing NXY-059 at both a similar and higher concentration (252 mg/kg bolus and 252 mg/kg/h), demonstrated that the concentration of NXY-059 in cortex increased linearly with respect to the plasma concentration. These data demonstrate that NXY-059 does penetrate brain tissue in control animals and ischemic tissue of animals subjected to pMCAO.

Home Time Is Extended in Patients With Ischemic Stroke Who Receive Thrombolytic Therapy A Validation Study of Home Time as an Outcome Measure

Background and Purpose— “Home time” (HT) refers to the number of days over the first 90 after stroke onset that a patient spends residing in their own home or a relatives home versus any institutional care. It is an accessible and objective parameter, free from subjective bias, with potential as an outcome measure in acute stroke trials. We sought to validate HT and assess treatment responsiveness using independent data. Methods— We estimated HT in the Stroke Acute Ischemic NXY Treatment (SAINT) I neuroprotection trial. We compared outcomes between thrombolyzed (T) and nonthrombolyzed comparators (C) using HT and the modified Rankin Scale. For our primary analysis, we adjusted for baseline covariates that significantly influence HT and in sensitivity analyses considered all variables that differed between groups at baseline. We report ordinal logistic regression and analysis of covariance with 95% CIs. We describe the relationship of HT with baseline National Institutes of Health Stroke Scale and its components and with Day 90 modified Rankin Scale and Barthel Index. Results— SAINT I included 1699 patients from 23 countries, of whom 28.7% received alteplase. HT correlated with age, baseline severity, alteplase use, side of ischemic lesion, presence of diabetes, and country of patient enrolment (each P<0.05). We found an association between use of alteplase with better adjusted outcomes by either measure (OR for extended HT, 1.36; 95% CI, 1.08 to 1.72; P=0.009; analysis of covariance P=0.007 with a 5.5-day advantage; OR for more favorable modified Rankin Scale, 1.6; 95% CI, 1.28 to 2.00; P<0.0001; Cochran-Mantel-Haenszel P=0.046). HT was significantly associated with baseline National Institutes of Health Stroke Scale and each component of the National Institutes of Health Stroke Scale except level of consciousness, dysarthria, and ataxia. HT was significantly associated with Day 90 modified Rankin Scale and Barthel Index. Conclusions— HT is a responsive measure for use in multinational acute stroke trials. Its inclusion as a complementary outcome is reasonable. We propose treatment effects are adjusted for age, baseline National Institutes of Health Stroke Scale, side of stroke lesion, country of enrollment, and the presence of diabetes.

Psychometric features of the ADAS-Cog: Identifying a potential cognition endpoint for prodromal Alzheimer's disease

cognitive functioning for different stages of AD. Despite the popularity of the ADAS-Cog, few studies have examined its item properties among patients with Mild Cognitive Impairment (MCI) and moderate impairment, and further validation of the ADAS-Cog is needed to substantiate its use at different stages of AD. This study examined whether there are differences in response to a particular item as a function of respondent characteristics (Apolipoprotein E and Impairment level) in the ADAS-Cog.Methods: jMetrik was used to analyse the ADAS-Cog. AD data was obtained from the Critical Path Institute Online Data Repository (CODR). Separate Rasch analyses were conducted comparingApoE carriers (n1⁄4 505) vs non-carriers (n 1⁄4 507), and MCI (MMSE 1⁄4 21 to 26; n 1⁄4 1362) and Moderate impairment (MMSE 14 to 20; n 1⁄4 1211) to examine summary and individual model fit statistics, person separation index (PSI), response format, local dependency, targeting, item bias (or differential item functioning -DIF), and dimensionalityResults:Based on the results of Rasch analyses different approaches can be taken to account measurement bias in properties of the ADAS-Cog post-hoc.Lower item calibration (Delta) reflects items with bias, indicating whether subgroups respond to items differently. The average age of 74.08 years (SD1⁄4 8.15) with 55.7%male patients. Commands (Delta 1⁄4 0.23), Constant Praxis (0.26), Ideational Praxis (0.32), and Naming Objects (0.26) shows ’moderate’ DIF, favoring theModerately impaired group, indicating that this item functions better in this group. Orientation (Delta 1⁄4 1.34) shows ’Large’ DIF, favoring the Moderately impaired group, indicating that this item functions better in this group. Word Recognition (-1.38) and Word Recall (-1.20) shows ’Large’ DIF, favoring the MCI group, indicating that this item functions better in this group. Conclusions: The choices made during analysis will substantially affect the results, and we have described and illustrated that the subgroups may have different impact on different items affecting outcome.