Dramatic Improvement in down Syndrome—Associated Cognitive Impairment with Donepezil

New therapies for treating Down syndrome require quality of life measurement

Down syndrome (DS) is the most common genetic cause of cognitive deficits. Using mouse models and therapies for Alzheimer disease, researchers are exploring therapies that may improve cognitive function in people with DS. These developments shift the health economic paradigm of understanding DS from determining the appropriate screening tool to the effect of therapy on quality of life in those with DS. To date, there are no validated quality of life instruments for DS. Research should begin to develop instruments that can evaluate changes in quality of life in therapeutic trials and beyond.

Donepezil significantly improves abilities in daily lives of female Down syndrome patients with severe cognitive impairment: a 24-week randomized, double-blind, placebo-controlled trial

OBJECTIVE

Down syndrome (DS) patients share certain neuropathological features with Alzheimer disease patients. A randomized, double-blind, placebo-controlled study was performed to investigate the efficacy and safety of donepezil, an Alzheimer disease drug, for DS patients.

METHOD

Twenty-one DS patients with severe cognitive impairment were assigned to take donepezil (3 mg daily) or a placebo for 24 weeks, and evaluated for activities in daily lives by concisely modified International Classification of Functioning, Disability and Health (ICF) scaling system.

RESULTS

ICF scores significantly increased without any adverse effects in the donepezil group in comparison to those in the placebo control. Among the individual functions tested, there was a dramatic improvement in the global mental functions and in specific mental functions.

CONCLUSIONS

Donepezil may effectively and safely improve overall functioning of DS patients with severe cognitive impairment.

Synthesis and in vitro and in vivo evaluation of 18F-labeled positron emission tomography (PET) ligands for imaging the vesicular acetylcholine transporter

A new class of vesicular acetylcholine transporter inhibitor that incorporates a carbonyl group into the benzovesamicol structure was synthesized, and analogues were evaluated in vitro. (+/-)-trans-2-Hydroxy-3-(4-(4-[(18)F]fluorobenzoyl)piperidino)tetralin (9e) has K(i) values of 2.70 nM for VAChT, 191 nM for sigma(1), and 251 nM for sigma(2). The racemic precursor (9d) was resolved via chiral HPLC, and (+/-)-[(18)F]9e, (-)-[(18)F]9e, and (+)-[(18)F]9e were respectively radiolabeled via microwave irradiation of the appropriate precursors with [(18)F]/F(-) and Kryptofix/K(2)CO(3) in DMSO with radiochemical yields of approximately 50-60% and specific activities of >2000 mCi/micromol. (-)-[(18)F]9e uptake in rat brain was consistent with in vivo selectivity for the VAChT with an initial uptake of 0.911 %ID/g in rat striatum and a striatum/cerebellum ratio of 1.88 at 30 min postinjection (p.i.). MicroPET imaging of macaques demonstrated a 2.1 ratio of (-)-[(18)F]9e in putamen versus cerebellum at 2 h p.i. (-)-[(18)F]9e has potential to be a PET tracer for clinical imaging of the VAChT.

Donepezil for dementia in people with Down syndrome

BACKGROUND

Alzheimer's dementia (AD) is the most common form of dementia in people with Down Syndrome [DS]. Acetylcholine is a chemical found in the brain that has an important role in memory, attention, reason and language. Donepezil a reversible inhibitor of acetylcholinesterase, which is thought to maintain levels of acetylcholine, and is reported to have some benefits for people with AD in the general population. It is important to note that people with DS tend to present with AD at a much younger age than the normal population as well as having subtle differences in physiology (e.g. metabolism and heart rate) and may therefore have different requirements from the general population.

OBJECTIVES

To determine the effectiveness and safety of donepezil for people with DS who develop AD.

SEARCH STRATEGY

CENTRAL, MEDLINE, EMBASE, CINAHL, PsycINFO, BIOSIS, SCI, SSCI and the NRR were searched up to October 2008. We contacted the manufacturers of donepezil as well as experts in the field, to ask about reports of unpublished or ongoing trials.

SELECTION CRITERIA

Randomised controlled trials of participants with DS and AD in which treatment with donepezil was administered compared with a placebo group.

DATA COLLECTION AND ANALYSIS

Data were extracted from the published reports of the one relevant study identified.

MAIN RESULTS

The one study included in this review is a small (n=30) randomised controlled trial lasting 24 weeks. It was followed-up by an open label study with a crossover design.No significant differences were found on any four validated outcomes including global functioning and three measures of cognitive abilities and behavioural problems. 6 out of 16 carers (37%) of participants on donepezil and 2 out of 15 (13%) on placebo reported improvement. No data were available for day to day skills, institutionalisation, reduction in carers' stress or economic outcomes. Half the intervention group and 20% of the placebo group reported adverse events; two participants left because of adverse events.

AUTHORS' CONCLUSIONS

To date there is only one small randomised controlled study on the effect of donepezil. This shows, at best, a modest, non statistically significant trend in favour of people with Down syndrome and Alzheimer's dementia who are able to tolerate donepezil (this drug is currently only dispensed in relatively large doses and is contraindicated for those with cardiac and respiratory problems).This study does not provide good evidence on which to base practice. Findings in an open-label follow up to this study suggest possible benefit in some individuals. Further, larger randomised controlled studies with longer-term follow up are required.

Donepezil: an update

Donepezil hydrochloride is the most widely prescribed drug for Alzheimer's disease (AD). The main mechanism of action through which it influences cognition and function is presumed to be the inhibition of acetylcholinesterase enzyme in the brain; however, donepezil may also impact the pathophysiology of AD at several other points. Officially approved for mild-to-moderate and severe AD, donepezil has also been shown to be effective in early-stage AD, vascular dementia, Parkinson's disease dementia/Lewy body disease and cognitive symptoms associated with multiple sclerosis. In addition, one study suggested that donepezil may delay the onset of AD in subjects with mild cognitive impairment, a prodrome to AD. The pharmacokinetics, pharmacodynamics, safety/tolerability profile and drug interaction properties of donepezil make it an easy and safe agent to use. However, in general, the efficacy of donepezil is limited, and ongoing studies are investigating other agents that may ultimately overtake its present position as the mainstay of anti-AD therapy.

Relevance of Donepezil in Enhancing Learning and Memory in Special Populations: A Review of the Literature

This review discusses the laboratory and clinical research supporting the rationale for the efficacy of donepezil (Aricept USA) in enhancing cognition in autism, Alzheimer disease, Down syndrome, traumatic brain injury, Attention Deficit Hyperactivity Disorder (ADHD), and schizophrenia. While preliminary animal models have shown effective, human studies exclusive of Alzheimer disease are sparse. Although attention and memory are unlikely a sole operation of the cholinergic system, evidence indicates a promising direction for further examination of this hypothesis in autism. Studies that examine changes in operationally defined behaviors and reliable and valid measure of changes in attention and memory are needed.

Safety and efficacy of rivastigmine in adolescents with Down syndrome: a preliminary 20-week, open-label study

Individuals with Down syndrome (DS) exhibit a cholinergic deficiency similar to that found in Alzheimer's disease. Cholinesterase inhibitors, used to treat Alzheimer's disease, may improve cognitive function in individuals with DS. This is the first investigation of the safety and efficacy of rivastigmine (an acetyl and butyryl cholinesterase inhibitor) on specific cognitive domains in pediatric DS. Eleven subjects with DS (ages 10-17 years) were treated with a liquid formulation of rivastigmine. Four subjects experienced no adverse events (AEs). Seven subjects reported AEs that were mild, transient and consistent with adverse events typically noted with cholinesterase inhibitors. Significant improvements were found in overall adaptive function (Vineland Adaptive Behavior Scales and Clinician's Interview-Based Impression of Change), attention (Leiter Attention Sustained tests A and B), memory (NEPSY: Narrative and Immediate Memory for Names subtests) and language (Test of Verbal Expression and Reasoning and Clinical Evaluation of Language Fundamentals-Preschool) domains. Improved language performance was found across all functional levels. These results underscore the need for larger, controlled studies employing a carefully constructed test battery capable of measuring the full scope of performance across multiple domains and a wide range of functional levels.

Reduced short latency afferent inhibition in patients with Down syndrome and Alzheimer-type dementia

OBJECTIVE

Adults with Down syndrome (DS) develop progressive cognitive impairment resembling the cognitive profile of Alzheimer's disease (AD). Although the specific neurobiological correlates of cognitive deficits in DS are still not completely understood, it has been proposed that cholinergic dysfunction may contribute to some of these deficits in DS who develop AD. A recently devised test of motor cortex excitability, the short latency afferent inhibition (SAI), has been proven to be helpful in exploring some cholinergic circuits of the human brain. The authors used this test to assess the involvement of the cholinergic transmission in the DS.

METHODS

We evaluated the SAI in 12 patients with DS and in 15 healthy subjects.

RESULTS

SAI was significantly reduced in DS patients when compared with the controls; the values correlated with the patient's age and the score on Dementia Scale for Down Syndrome. SAI was increased after administration of a single dose of donezepil in a subgroup of 5 patients.

CONCLUSIONS

Our findings suggest that, with respect to this putative marker of central cholinergic activity, dementia in aging DS shares pathophysiological similarities to AD in the general population.

SIGNIFICANCE

This technique may help to clarify the pathophysiological basis of cognitive dysfunction in DS and may represent an additional tool for the diagnosis of Alzheimer-type dementia in subjects with DS.

The cholinergic system in Down's syndrome

The cholinergic system is one of the most important modulatory neurotransmitter systems in the brain. Alterations of the transmission communicators are accompanied by reduction of the cortical activity, which is associated with a learning and memory deficit. Down's syndrome is a pathological condition characterized by a high number of abnormalities that involve the brain. The cholinergic system is involved in alterations of the neurological system such as severe learning difficulties. To explain these alterations, important results are obtained from studies about murine trisomy 16 (animal model of Down's syndrome). The results obtained provide useful elements in the improvement of knowledge about the neurological and neurotransmissional alterations that are responsible for the neurobiological characteristics of Down's syndrome. These data potentially justify, in these patients, the therapeutic use of drugs that are principally administered to improve the severe learning difficulties of people with Alzheimer's disease, and suggest a trend which generates a hypothesis worthy of further exploration.

Pitfalls And Hopes in Down Syndrome Therapeutic Approaches: In the Search for Evidence-Based Treatments

Trisomy 21 or Down syndrome (DS) is a complex syndrome, of genetic origin with multiple and variable neurobiological and neuropsychological manifestations. DS patients have consistent signs of brain damage along their lives, but understanding the biology of DS is complicated due to the extraordinary heterogeneity of the phenotypic signs. Thus, treatment of DS mental retardation poses significant challenges for clinicians and scientists. The review addresses the classical pharmacological and environmental treatments and also critically reviews the new possibilities that are emerging from the exciting advances in gene or cell therapy. We describe some of the most recent developments in the field and give a sense of the prospects for future prevention and therapy.