Alzheimer's disease: The right drug, the right time Golde, Todd E; DeKosky, Steven T; Galasko, Douglas
Science (American Association for the Advancement of Science),
12/2018, Letnik:
362, Številka:
6420
Journal Article
Recenzirano
Lessons from failed clinical trials can improve the development of Alzheimer's disease–modifying therapies
Alzheimer's disease (AD) is an age-associated neurodegenerative disease that is reaching ...epidemic proportions as a result of the aging of the world's population. Impressive gains in our understanding of AD pathogenesis have not yet translated into disease-modifying therapies that benefit patients. Is this because the knowledge that guides target identification and, hence, therapeutics, is insufficient? Are current clinical trial designs not optimal? Or are other factors contributing? Here, we highlight the challenges of developing effective AD therapies and discuss how lessons learned from failed trials must be implemented to increase the likelihood of success.
Summary Alzheimer's disease (AD) is classically defined as a dual clinicopathological entity. The recent advances in use of reliable biomarkers of AD that provide in-vivo evidence of the disease has ...stimulated the development of new research criteria that reconceptualise the diagnosis around both a specific pattern of cognitive changes and structural/biological evidence of Alzheimer's pathology. This new diagnostic framework has stimulated debate about the definition of AD and related conditions. The potential for drugs to intercede in the pathogenic cascade of the disease adds some urgency to this debate. This paper by the International Working Group for New Research Criteria for the Diagnosis of AD aims to advance the scientific discussion by providing broader diagnostic coverage of the AD clinical spectrum and by proposing a common lexicon as a point of reference for the clinical and research communities. The cornerstone of this lexicon is to consider AD solely as a clinical and symptomatic entity that encompasses both predementia and dementia phases.
Over the past decade, public awareness of the long-term pathological consequences of traumatic brain injury (TBI) has increased. Such awareness has been stimulated mainly by reports of progressive ...neurological dysfunction in athletes exposed to repetitive concussions in high-impact sports such as boxing and American football, and by the rising number of TBIs in war veterans who are now more likely to survive explosive blasts owing to improved treatment. Moreover, the entity of chronic traumatic encephalopathy (CTE)--which is marked by prominent neuropsychiatric features including dementia, parkinsonism, depression, agitation, psychosis, and aggression--has become increasingly recognized as a potential late outcome of repetitive TBI. Annually, about 1% of the population in developed countries experiences a clinically relevant TBI. The goal of this Review is to provide an overview of the latest understanding of CTE pathophysiology, and to delineate the key issues that are challenging clinical and research communities, such as accurate quantification of the risk of CTE, and development of reliable biomarkers for single-incident TBI and CTE.
Summary The NINCDS–ADRDA and the DSM-IV-TR criteria for Alzheimer's disease (AD) are the prevailing diagnostic standards in research; however, they have now fallen behind the unprecedented growth of ...scientific knowledge. Distinctive and reliable biomarkers of AD are now available through structural MRI, molecular neuroimaging with PET, and cerebrospinal fluid analyses. This progress provides the impetus for our proposal of revised diagnostic criteria for AD. Our framework was developed to capture both the earliest stages, before full-blown dementia, as well as the full spectrum of the illness. These new criteria are centred on a clinical core of early and significant episodic memory impairment. They stipulate that there must also be at least one or more abnormal biomarkers among structural neuroimaging with MRI, molecular neuroimaging with PET, and cerebrospinal fluid analysis of amyloid β or tau proteins. The timeliness of these criteria is highlighted by the many drugs in development that are directed at changing pathogenesis, particularly at the production and clearance of amyloid β as well as at the hyperphosphorylation state of tau. Validation studies in existing and prospective cohorts are needed to advance these criteria and optimise their sensitivity, specificity, and accuracy.
Alzheimer's disease (AD) is the major cause of late-life brain failure. In the past 25 years, autosomal dominant forms of AD were found to be primariy attributable to mutations in one of two ...presenilins, polytopic proteins that contain the catalytic site of the γ-secretase protease that releases the amyloid beta (Aβ) peptide. Some familial AD is also due to mutations in the amyloid precursor protein (APP), but recently a mutation in APP was discovered that reduces Aβ generation and is protective against AD, further implicating amyloid metabolism. Prion-like seeding of amyloid fibrils and neurofibrillary tangles has been invoked to explain the stereotypical spread of AD within the brain. Treatment trials with anti-Aβ antibodies have shown target engagement, if not significant treatment effects. Attention is increasingly focused on presymptomatic intervention, because Aβ mismetabolism begins up to 25 years before symptoms begin. AD trials deriving from new biological information involve extraordinary international collaboration and may hold the best hope for success in the fight against AD.
Objective
We utilized the amyloid imaging ligand Pittsburgh Compound B (PiB) to determine the presence of Alzheimer's disease (AD) pathology in different mild cognitive impairment (MCI) subtypes and ...to relate increased PiB binding to other markers of early AD and longitudinal outcome.
Methods
Twenty‐six patients with MCI (13 single‐domain amnestic‐MCI a‐MCI, 6 multidomain a‐MCI, and 7 nonamnestic MCI) underwent PiB imaging. Twenty‐three had clinical follow‐up (21.2 ± 16.0 standard deviation months) subsequent to their PiB scan.
Results
Using cutoffs established from a control cohort, we found that 14 (54%) patients had increased levels of PiB retention and were considered “amyloid‐positive.” All subtypes were associated with a significant proportion of amyloid‐positive patients (6/13 single‐domain a‐MCI, 5/6 multidomain a‐MCI, 3/7 nonamnestic MCI). There were no obvious differences in the distribution of PiB retention in the nonamnestic MCI group. Predictors of conversion to clinical AD in a‐MCI, including poorer episodic memory, and medial temporal atrophy, were found in the amyloid‐positive relative to amyloid‐negative a‐MCI patients. Longitudinal follow‐up demonstrated 5 of 13 amyloid‐positive patients, but 0 of 10 amyloid‐negative patients, converted to clinical AD. Further, 3 of 10 amyloid‐negative patients “reverted to normal.”
Interpretation
These data support the notion that amyloid‐positive patients are likely to have early AD, and that the use of amyloid imaging may have an important role in determining which patients are likely to benefit from disease‐specific therapies. In addition, our data are consistent with longitudinal studies that suggest a significant percentage of all MCI subtypes will develop AD. Ann Neurol 2009;65:557–568
Synapse damage and loss are fundamental to the pathophysiology of Alzheimer's disease (AD) and lead to reduced cognitive function. The goal of this review is to address the challenges of forging new ...clinical development approaches for AD therapeutics that can demonstrate reduction of synapse damage or loss. The key points of this review include the following: Synapse loss is a downstream effect of amyloidosis, tauopathy, inflammation, and other mechanisms occurring in AD.Synapse loss correlates most strongly with cognitive decline in AD because synaptic function underlies cognitive performance.Compounds that halt or reduce synapse damage or loss have a strong rationale as treatments of AD.Biomarkers that measure synapse degeneration or loss in patients will facilitate clinical development of such drugs.The ability of methods to sensitively measure synapse density in the brain of a living patient through synaptic vesicle glycoprotein 2A (SV2A) positron emission tomography (PET) imaging, concentrations of synaptic proteins (e.g., neurogranin or synaptotagmin) in the cerebrospinal fluid (CSF), or functional imaging techniques such as quantitative electroencephalography (qEEG) provides a compelling case to use these types of measurements as biomarkers that quantify synapse damage or loss in clinical trials in AD.
A number of emerging biomarkers are able to measure synapse injury and loss in the brain and may correlate with cognitive function in AD. These biomarkers hold promise both for use in diagnostics and in the measurement of therapeutic successes.
The National Institute on Aging and the Alzheimer's Association charged a workgroup with the task of developing criteria for the symptomatic predementia phase of Alzheimer's disease (AD), referred to ...in this article as mild cognitive impairment due to AD. The workgroup developed the following two sets of criteria: (1) core clinical criteria that could be used by healthcare providers without access to advanced imaging techniques or cerebrospinal fluid analysis, and (2) research criteria that could be used in clinical research settings, including clinical trials. The second set of criteria incorporate the use of biomarkers based on imaging and cerebrospinal fluid measures. The final set of criteria for mild cognitive impairment due to AD has four levels of certainty, depending on the presence and nature of the biomarker findings. Considerable work is needed to validate the criteria that use biomarkers and to standardize biomarker analysis for use in community settings.
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