Bridging study of S12024 in 53 in-patients with Alzheimer's disease

Practice effects due to serial cognitive assessment: Implications for preclinical Alzheimer's disease randomized controlled trials

Introduction

Practice effects are characteristic of nearly all standard cognitive tasks when repeated during serial assessments and are frequently important confounders in clinical trials.

Methods

We summarize evidence that gains in neuropsychological test performance scores associated with practice effects occur as artifactual changes associated with serial testing within clinical trials. We identify and emphasize such gains in older, non–cognitively impaired individuals and estimate an effect size of 0.25 for composite cognitive measures in older populations assessed three times in a 6- to 12-month period.

Results

We identified three complementary approaches that can be used to attenuate practice effects: (1) massed practice in a prebaseline period to reduce task familiarity effects; (2) tests designed to reduce practice-related gains so that item-specific driven improvements are minimized by using tasks that minimize strategy and/or maximize interitem interference; and (3) well-matched alternate forms.

Discussion

We have drawn attention to and increased awareness of practice effect–related gains that could result in type 1 or type 2 errors in trials. Successfully managing practice effects will eliminate a large source of error and reduce the likelihood of misinterpretation of clinical trials outcomes.

Therapeutic approaches to age-associated neurocognitive disorders

The United Nations projects that the number of individuals with dementia in developed countries alone will be approximately 36,7 million by the year 2050. International recognition of the significant emotional and economic burden of Alzheimer's disease has been matched by a dramatic increase in the development of pharmacological and nonpharmacological approaches to this illness in the past decade. Changing demographics have underscored the necessity to develop similar approaches for the remediation of the cognitive impairment associated with more benign syndromes, such as mild cognitive impairment (MCI) and age-associated cognitive decline (AACD). The present article aims to provide an overview of the most current therapeutic approaches to age-associated neurocognitive disorders. Additionally, it discusses the conceptual and methodological issues that surround the design, implementation, and interpretation of such approaches.

The evaluation of cognitive function in the dementias: methodological and regulatory considerations

Impairment of cognitive function is the central feature of dementia. Although, clinically, the cognitive deficit most often manifests itself as memory problems, a number of other areas of cognition are affected, and memory is but one of the cognitive skills compromised in dementia. Dementia with Lewy bodies, for example, accounts for 15% to 25% of all dementias and does not have memory deficits as a core feature. Our cognitive facilities underlie our abilities to engage successfully in the activities of daily living (ADL) and it follows thai enhancement of cognitive function will facilitate performance of ADL The assessment and understanding of these impairments are crucial to any treatment of the disorder. Unfortunately, the principal instrument used to assess cognitive function in most of the major clinical trials of Alzheimer's disease in recent years, the Alzheimer's Disease Assessment Scale-Cognitive Subsection (ADAS-COG), primarily assesses aspects of memory, which has resulted in other important cognitive deficits in dementia being overlooked. Automated cognitive tests are now available that can identify an earlier onset of improvements in dementia in smaller samples than the ADAS, Regulatory authorities should encourage - or even require - the use of automated procedures alongside the ADAS in pivotal trials to help determine the relative utility of the instruments in the fairest way possible. Whatever the outcome, this will be of long-term benefit to patients, carers, drug developers, clinicians, and regulators in this important area.

Computerized cognition assessment during acetylcholinesterase inhibitor treatment in Alzheimer's disease

OBJECTIVES

Alzheimer's disease assessment scale-cognitive subscale (ADAS-Cog) has become a standard clinical trials outcome for cognition, but has been recognized as deficient in areas including coverage of cognitive domains, sensitivity and standardization. Computerized test batteries may address some of these issues. The cognitive drug research computerized assessment (CDR) system is validated in Alzheimer's disease (AD). This study was designed to further evaluate validity in relation to ADAS-Cog, mini mental state examination (MMSE) and cerebrospinal fluid (CSF) biomarkers and psychometric properties, in a population of Alzheimer's patients on stable anticholinesterase treatment.

MATERIALS AND METHODS

Patients completed cognition assessments, CSF and blood sampling at baseline and 6 months later. Data for 65 patients were evaluated.

RESULTS

The CDR system demonstrated good psychometric properties in this population. Measures of psychomotor speed showed possible sensitivity to decline over 6 months.

CONCLUSIONS

There are a number of methodological problems with current cognition assessment methodology for clinical trials. Computerized measures and in particular millisecond reaction time measures, may address many of these issues.

Reliable diagnoses of dementia by the naive credal classifier inferred from incomplete cognitive data

Dementia is a serious personal, medical and social problem. Recent research indicates early and accurate diagnoses as the key to effectively cope with it. No definitive cure is available but in some cases when the impairment is still mild the disease can be contained. This paper describes a diagnostic tool that jointly uses the naive credal classifier and the most widely used computerized system of cognitive tests in dementia research, the Cognitive Drug Research system. The naive credal classifier extends the discrete naive Bayes classifier to imprecise probabilities. The naive credal classifier models both prior ignorance and ignorance about the likelihood by sets of probability distributions. This is a new way to deal with small and incomplete datasets that departs significantly from most established classification methods. In the empirical study presented here, the naive credal classifier provides reliability and unmatched predictive performance. It delivers up to 95% correct predictions while being very robust with respect to the partial ignorance due to the largely incomplete data. The diagnostic tool also proves to be very effective in discriminating between Alzheimer's disease and dementia with Lewy bodies.

Automatic attentional shifts induced by a noradrenergic drug in Alzheimer's disease: evidence from evoked potentials

Prior research showed that attentional deficits are observed in Alzheimer's disease (AD). These deficits can further impair other cognitive processes. The present experiment was designed to study the shifts in attention induced by a noradrenergic drug (S 12024-2) through their electrophysiological correlates in 12 outpatients with mild AD, using an auditory oddball paradigm. The P3a component, known to be related to automatic attentional processing, was increased by the drug, whereas no changes occurred either in PN or in P3b, which are considered to reflect conscious processing. These results point to an involvement of the noradrenergic system in the modulation of automatic attentional processing, and provide evidence for weakening of the orienting reflex in AD, due to a possible noradrenergic deficit in patients with mild AD.

Experimental and clinical methods in the development of anti-Alzheimer drugs

Methodology used for the development of anti-Alzheimer's disease (AD) drugs raises specific problems which are rarely examined in the literature. While the general development scheme is similar to that required for most drugs, some specific aspects must be analyzed, highly dominated by the dual goal of pharmacology, i.e., to obtain both symptomatic and etiopathogenic drugs. During preclinical studies, aged or lesioned animals are mainly useful for symptomatic drugs, whereas transgenic models or neurodegeneration-induced techniques would probably lead to etiopathogenic drugs potentially slowing down the process of AD. The first administrations of a new compound to human beings raise the question of the activity measurement techniques. Psychometry remains the most informative procedure to detect and analyze the activity of the drugs on the different components of cognition. Electrophysiology and neuroimaging need some complementary studies before they can be proposed as surrogate criteria in phase III trials. At this stage of development, American and the recently published European guidelines are of great help while insisting on long-term (6 months) placebo controlled trials with the use of the triple efficacy criterion: an objective cognition scale, a global assessment, and the opinion of the caregiver. In the long term, pharmacoepidemiology and pharmacoeconomy will have to confirm the rationale of this recent progress in the methodology of anti-AD drug development.

Application of population pharmacokinetics to the phase II development of an anti-Alzheimer's disease compound, S12024

Steady-state concentrations of S12024, a novel compound for treatment of Alzheimer's disease, were studied to determine the pharmacokinetic parameters of S12024 in Phase IIa patients and to assess the effect of patient characteristics on those pharmacokinetics. A prospective sparse sampling strategy was used to obtain oral repeated data (n = 285) from 89 patients, which were analyzed using a one-compartment model and the NONMEM computer program. The model suggested that apparent clearance of S12024 was influenced by the study and by patient age. In the Spanish study, apparent clearance was increased by 68% and 26% for doses of 100 mg and 300 mg, respectively, and patient age decreased oral clearance by approximately 10% per decade in the patient age range (50 to 90 years). Data from only a few patients in the Spanish study were probably responsible for the observed study influence on apparent clearance of S12024, and no measured covariates could explain this effect. The model provided an excellent characterization of the observed data and it predicted correctly the plasma concentrations from an earlier Phase I trial and a subsequent Phase IIb study. The present model, built from Phase IIa data, provides a basis for examining the influence of patient covariates and the magnitude of their effects on the pharmacokinetics of S12024. The study effect is probably an artefact that will disappear by further expanding of the population model in the future.