Can CSF biomarkers or pre-treatment progression rate predict response to cholinesterase inhibitor treatment in Alzheimer's disease?

Relationship between the response to donepezil and plasma amyloid beta oligomers in patients with Alzheimer's disease

AIM

To date, there is no reported effective biomarker that can predict which Alzheimer's disease (AD) patients will respond to donepezil and which will not. This study aimed to investigate whether baseline values of Aβ oligomers (AβOs), measured by the Multimer Detection System-Oligomeric Aβ (MDS-OAβ), can be used to predict responders after 6 months of donepezil medication.

METHODS

The study enrolled 104 patients diagnosed with probable AD. After 6 months of donepezil medication, the response to treatment was evaluated by re-assessing the Korean version of the Mini-Mental State Examination (K-MMSE) and Clinical Dementia Rating scale-Sum of Box (CDR-SB) scales conducted at baseline. The patients were categorized into two groups according to the baseline MDS-OAβ values known as the cut-off for AD diagnosis: a group with values below 0.78 and another group with values equal to or above 0.78.

RESULTS

After 6 months of medication, the number of responders was 50 (49.5%). Responders exhibited significantly worse baseline CDR, CDR-SB, K-MMSE, and Barthel index compared with non-responders. There was a significantly higher number of responders among patients with MDS-OAβ values below the cut-off of 0.78 compared with those with values equal to or above this threshold. Furthermore, there was a significant improvement in the K-MMSE and CDR-SB after 6 months of donepezil medication in patients with MDS-OAβ values below 0.78 compared with those with values equal to or above 0.78.

CONCLUSIONS

Baseline MDS-OAβ values might constitute a novel biochemical marker for the efficacy of 6 months of donepezil treatment in AD. Geriatr Gerontol Int 2024; ••: ••-••.

Predictors of response to acetylcholinesterase inhibitors in dementia: A systematic review

Background

The mainstay of therapy for many neurodegenerative dementias still relies on acetylcholinesterase inhibitors (AChEI); however, there is debate on various aspects of such treatment. A huge body of literature exists on possible predictors of response, but a comprehensive review is lacking. Therefore, our aim is to perform a systematic review of the predictors of response to AChEI in neurodegenerative dementias, providing a categorization and interpretation of the results.

Methods

We conducted a systematic review of the literature up to December 31st, 2021, searching five different databases and registers, including studies on rivastigmine, donepezil, and galantamine, with clearly defined criteria for the diagnosis of dementia and the response to AChEI therapy. Records were identified through the string: predict * AND respon * AND (acetylcholinesterase inhibitors OR donepezil OR rivastigmine OR galantamine). The results were presented narratively.

Results

We identified 1,994 records in five different databases; after exclusion of duplicates, title and abstract screening, and full-text retrieval, 122 studies were finally included.

Discussion

The studies show high heterogeneity in duration, response definition, drug dosage, and diagnostic criteria. Response to AChEI seems associated with correlates of cholinergic deficit (hallucinations, fluctuating cognition, substantia innominate atrophy) and preserved cholinergic neurons (faster alpha on REM sleep EEG, increased anterior frontal and parietal lobe perfusion after donepezil); white matter hyperintensities in the cholinergic pathways have shown inconsistent results. The K-variant of butyrylcholinesterase may correlate with better response in late stages of disease, while the role of polymorphisms in other genes involved in the cholinergic system is controversial. Factors related to drug availability may influence response; in particular, low serum albumin (for donepezil), CYP2D6 variants associated with reduced enzymatic activity and higher drug doses are the most consistent predictors, while AChEI concentration influence on clinical outcomes is debatable. Other predictors of response include faster disease progression, lower serum cholesterol, preserved medial temporal lobes, apathy, absence of concomitant diseases, and absence of antipsychotics. Short-term response may predict subsequent cognitive response, while higher education might correlate with short-term good response (months), and long-term poor response (years). Age, gender, baseline cognitive and functional levels, and APOE relationship with treatment outcome is controversial.

Acute response to cholinergic challenge predicts long-term response to galantamine treatment in patients with Alzheimer's Disease

BACKGROUND

Cholinesterase inhibitors (CEIs) have been shown to improve cognitive functioning in Alzheimer's Disease (AD) patients, but are associated with multiple side effects and only 20-40% of the patients clinically improve. In this study, we aimed to investigate the acute pharmacodynamic (PD) effects of a single dose administration of galantamine on CNS functioning in mild to moderate AD patients and its potential to predict long-term treatment response.

METHODS

This study consisted of a challenge and treatment phase. In the challenge phase, a single dose of 16 mg galantamine was administered to 50 mild to moderate AD patients in a double-blind, placebo-controlled cross-over fashion. Acute PD effects were monitored up to 5 hours after administration with use of the NeuroCart CNS test battery and safety and pharmacokinetics were assessed. In the treatment phase, patients were treated with open-label galantamine according to regular clinical care. After 6 months of galantamine treatment, patients were categorized as either responder or as non-responder based on their MMSE, NPI and DAD scores. An analysis of covariance was performed to study the difference in acute PD effects during the challenge phase between responders and non-responders.

RESULTS

A single dose of galantamine significantly reduced saccadic reaction time (-0.0099; 95%CI=-0.0195,-0.0003; p=.0430), absolute frontal EEG parameters in alpha (-14.9; 95%CI=-21.0,-8.3; p=.0002), beta (-12.6; 95%CI=-19.4,-5.3; p=.0019) and theta (-17.9; 95%CI=-25.0,-10.0; p=.0001) frequencies. Relative frontal (-1.669; 95%CI=-2.999,-0.339; p=.0156) and occipital (-1.856; 95%CI=-3.339,-0.372; p=.0166) EEG power in theta frequency and relative occipital EEG power in the gamma frequency (1.316; 95%CI=0.158,2.475; p=.0273) also increased significantly compared to placebo. Acute decreases of absolute frontal alpha (-20.4; 95%CI=-31.6,-7.47; p=.0046), beta (-15.7; 95% CI=-28.3,-0.93; p=.0390) and theta (-25.9; 95%CI=-38.4,-10.9; p=.0024) EEG parameters and of relative frontal theta power (-3.27%; 95%CI=-5.96,-0.58; p=.0187) on EEG significantly distinguished responders (n=11) from non-responders (n=32) after 6 months.

CONCLUSIONS

This study demonstrates that acute PD effects after single dose of galantamine are correlated with long-term treatment effects and that patients who demonstrate a reduction in EEG power in the alpha and theta frequency after a single administration of galantamine 16 mg will most likely respond to treatment.

Cerebrospinal Fluid Biomarker Levels as Markers for Nursing Home Placement and Survival Time in Alzheimer's Disease

BACKGROUND

Cerebrospinal fluid (CSF) biomarkers are associated with conversion from mild cognitive impairment to Alzheimer's disease (AD), but their predictive value for later end-points has been less evaluated with inconsistent results.

OBJECTIVE

We investigated potential relationships between CSF amyloid-β1-42 (Aβ42), phosphorylat- ed tau (P-tau), and total tau (T-tau) with time to nursing home placement (NHP) and life expectan- cy after diagnosis.

METHODS

This prospective observational study included 129 outpatients clinically diagnosed with mild-to-moderate AD who underwent a lumbar puncture. The CSF biomarkers were analysed with xMAP technology. Dates of institutionalisation and death were recorded.

RESULTS

After 20 years of follow-up, 123 patients (95%) were deceased. The participants with ab- normal P-tau and T-tau (A+ T+ (N)+) died earlier than those with normal P-tau/abnormal T-tau (A+ T- (N)+) (mean, 80.5 vs. 85.4 years). Linear associations were demonstrated between lower Aβ42 and shorter time to NHP (p = 0.017), and higher P-tau and younger age at death (p = 0.016). No correlations were detected between survival after AD diagnosis and CSF biomarkers. In sex- and-age-adjusted Cox regression models, higher P-tau and T-tau were independent predictors of shorter lifespan after diagnosis. In multivariate Cox models, older age and lower baseline cognitive status, but not elevated tau, significantly precipitated both institutionalisation and death.

CONCLUSION

These findings suggest that CSF biomarker levels plateau in the dementia phase of AD, which may limit their possible relationships with clinical end-points, such as NHP and survi- val time. However, the biomarkers reflect the central pathophysiologies of AD. In particular, patho- logic tau is associated with more advanced disease, younger age at onset, and earlier death.

Cerebro-spinal fluid biomarker levels: phosphorylated tau (T) and total tau (N) as markers for rate of progression in Alzheimer's disease

Background

We investigated the potential associations between cerebro-spinal fluid (CSF) levels of phosphorylated tau (P-tau) and total tau (T-tau) with short-term response to cholinesterase inhibitor (ChEI) treatment, longitudinal outcome and progression rates in Alzheimer’s disease (AD).

Methods

This prospective, observational study included 129 participants clinically diagnosed with mild-to-moderate AD, who underwent a lumbar puncture. The CSF biomarkers amyloid-β_1–42 (Aβ₄₂), P-tau and T-tau were analysed with xMAP technology. Cognitive, global, instrumental and basic activities of daily living (ADL) capacities at the start of ChEI therapy and semi-annually over 3 years were evaluated.

Results

All patients had abnormal Aβ₄₂ (A+). Fifty-eight individuals (45%) exhibited normal P-tau and T-tau (A+ T– (N)–), 12 (9%) abnormal P-tau/normal T-tau (A+ T+ (N)–), 17 (13%) normal P-tau/abnormal T-tau (A+ T– (N)+) and 42 (33%) abnormal P-tau and T-tau (A+ T+ (N)+). The participants with A+ T+ (N)+ were younger than A+ T– (N)+ at the estimated onset of AD and the initiation of ChEIs. The proportion of 6-month responders to ChEI and deterioration/year after start of treatment did not differ between the AT(N) profiles in any scales. A higher percentage of globally improved/unchanged patients was exhibited in the A+ T– (N)– group after 12, 30 and 36 months of ChEI therapy but not at other assessments. In apolipoprotein E (APOE) ε4-carriers, linear relationships were found between greater cognitive decline/year and higher tau; Mini-Mental State Examination score – T-tau (r_s = − 0.257, p = 0.014) and Alzheimer’s Disease Assessment Scale–cognitive subscale – P-tau (r_s = − 0.242, p = 0.022). A correlation between faster progression in instrumental ADL (IADL) and higher T-tau was also detected (r_s = − 0.232, p = 0.028). These associations were not demonstrated in non-ε4-carriers.

Conclusions

Younger age and faster global deterioration were observed in AD patients with pathologic tau and neurodegeneration, whereas more rapid cognitive and IADL decline were related to higher P-tau or T-tau in APOE ε4-carriers only. The results might indicate an association between more pronounced tau pathology/neuronal injury and the APOE ε4-allele leading to a worse prognosis. Our findings showed that the AT(N) biomarker profiles have limited utility to predict AD progression rates and, thus, measure change and interpreting outcomes from clinical trials of future therapies.

[Neuroimaging and molecular biomarkers of dementia]

Development of laboratory diagnosis and neuroimaging revealed a number of biomarkers for in vivo diagnosis of the most common forms of dementia (Alzheimer's disease, Lewy body dementia and vascular dementia). Currently, the highest diagnostic sensitivity and specificity of molecular biomarkers in the cerebrospinal fluid are detected for Alzheimer's disease. At the same time, the changes according to the magnetic resonance imaging are more prognostically significant for future cognitive decline than cerebrospinal fluid biomarkers. Cerebral microbleeds are an available adjuvant diagnostic marker, which increases the diagnostic value of leukoaraiosis that suggests the development of cerebral amyloid angiopathy or hypertensive microangiopathy, especially in cases of mixed pathology and severe cognitive deficits.

Prediction of Treatment Response to Donepezil using Automated Hippocampal Subfields Volumes Segmentation in Patients with Mild Alzheimer's Disease

Previous studies reported some relationships between donepezil treatment and hippocampus in Alzheimer's disease (AD). However, due to methodological limitations, their close relationships remain unclear. The aim of this study is to predict treatment response to donepezil by utilizing the automated segmentation of hippocampal subfields volumes (ASHS) in AD. Sixty four AD patients were prescribed with donepezil and were followed up for 24 weeks. Cognitive function was measured to assess whether there was a response from the donepezil treatment. ASHS was implemented on non-responder (NR) and responder (TR) groups, and receiver operator characteristic (ROC) analysis was conducted to evaluate the sensitivity, specificity, and accuracy of hippocampal subfields in predicting response to donepezil. The left total hippocampus and the CA1 area of the NR were significantly smaller than those of the TR group. The ROC curve analysis showed the left CA1 volumes showed highest area under curve (AUC) of 0.85 with a sensitivity of 88.0%, a specificity of 74.0% in predicting treatment response to donepezil treatment. We expect that hippocampal subfields volume measurements that predict treatment responses to current AD drugs will enable more evidence-based, individualized prescription of medications that will lead to more favorable treatment outcomes.

Pharmacotherapy for Dementia: A Practical Approach to the Use of Cholinesterase Inhibitors and Memantine

Cholinesterase inhibitors and memantine are the only classes of drugs approved for the treatment of dementia due to Alzheimer's disease. This article provides evidence-based recommendations to address the issues regarding the use of cholinesterase inhibitors and memantine in clinical practice. It includes their efficacy, timing, assessment, use in institutionalized patients, combined use, and use in other dementia types. However, most of the studies are of short duration (<1 year) and are mainly focused on cognitive and global improvement, whereas the practical issue of their use in daily practice such as optimal duration of treatment, long-term efficacy and delaying institutionalization are limited.

Initial cognitive response to cholinesterase inhibitors and subsequent long-term course in patients with mild Alzheimer's disease

BACKGROUND

Some guidelines recommend to discontinue treatment with cholinesterase inhibitors (ChEIs) in patients with Alzheimer's disease (AD) without an initial response to ChEI treatment. Evidence supporting this recommendation, however, is limited. This study aimed to investigate the relation between the initial cognitive response to ChEI treatment and the subsequent long-term course of cognition of AD patients.

METHODS

The Frisian Alzheimer's Disease Cohort study is a retrospective longitudinal study of 576 community-dwelling AD patients treated with ChEIs in a "real-life" setting at a large memory clinic. A repeated measures analysis using a marginal model (population based averaged model) was applied to investigate whether there is a difference in the subsequent long-term course of cognition (Mini-Mental State Examination (MMSE)) between initial non-responders and responders. Absence of an initial response was defined as a lower MMSE score after the first six months of treatment compared to baseline, a positive response as the same or a higher MMSE score.

RESULTS

At baseline, median age was 80 years and the median MMSE score 23. Non-responders showed a slower rate of cognitive decline in the three subsequent years than responders, with a mean annual MMSE decline of 0.9 points versus 1.2 points, respectively (p < 0.0001).

CONCLUSIONS

Our results suggest that it is not appropriate to discontinue ChEI treatment solely based on the absence of an initial cognitive response.

Evaluating Response to High-Dose 13.3 mg/24 h Rivastigmine Patch in Patients with Severe Alzheimer's Disease

AIMS

To identify factors predicting improvement/stabilization on the Alzheimer's Disease Cooperative Study-Clinical Global Impression of Change (ADCS-CGIC) and investigate whether early treatment responses can predict long-term outcomes, during a trial of 13.3 mg/24 h versus 4.6 mg/24 h rivastigmine patch in patients with severe Alzheimer's disease (AD).

METHODS

Logistic regression was used to relate Week 24 ADCS-CGIC score to potential baseline predictors. Additional analyses based on receiver-operating characteristic curves were performed using Week 8/16 ADCS-CGIC scores to predict response (13.3 mg/24 h patch) at Week 24. ADCS-CGIC score of (1) 1-3 = "improvement," (2) 1-4 = "improvement or no change".

RESULTS

"Treatment" (13.3 mg/24 h patch) and increased age were significant predictors of "improvement" (P = 0.01 and P = 0.003, respectively), and "treatment" (P = 0.001), increased age (P = 0.002), and prior AD treatment (P = 0.03) for "improvement or no change". At Week 8 and 16, ADCS-CGIC scores of 4 and 5 were optimal thresholds in predicting "improvement," and "improvement or no change," respectively, at Week 24.

CONCLUSIONS

A significant therapeutic effect of high-dose rivastigmine patch on ADCS-CGIC response was observed. The 13.3 mg/24 h patch was identified as a predictor of "improvement" or "improvement or no change". Patients with minimal worsening/improvement/no change after treatment initiation may be more likely to respond following long-term therapy.

The prediction of response to galantamine treatment in patients with mild to moderate Alzheimer's disease

The prediction of efficacy in long-term treatment of acetylcholinesterase inhibitors (AChEIs) is a major clinical issue, although no consistently strong predictive factors have emerged thus far. The present analyses aimed to identify factors for predicting long-term outcome of galantamine treatment. Analyses were conducted with data from a 24 weeks randomized, double-blind, placebo controlled trial to evaluate the efficacy and the safety of galantamine in the treatment of 303 patients with mild to moderate AD. Patients were divided into responders (4 or more point improvement of ADAS-cog scores at 24 weeks of treatment) and non-responders. We explored whether patients’ background (e.g. sex, age, and duration of disease) and scores of cognitive scales at early stage, are relevant to the long-term response to AChEIs. Predictive values were estimated by the logistic regression model. The responder rate was 31.7 %. We found that changes in scores of ADAS-J cog subscales between week 4 and baseline, especially word recognition, can be a good variable to predict subsequent response to galantamine, with approximately 75% of predictive performance. Characteristics of patients, including demographic characteristics, severity of disease and neuropsychological features before treatment were poorly predictive. The present study indicate that initial response to galantamine administration in patients with mild to moderate AD seems to be a reliable predictor of response of consequent galantamine treatment. Patients who show improvement of episodic memory function during the first 4 weeks of galantamine administration may be likely to particularly benefit from galantamine treatment.

Biomarkers in Alzheimer's disease analysis by mass spectrometry-based proteomics

Alzheimer’s disease (AD) is a common chronic and destructive disease. The early diagnosis of AD is difficult, thus the need for clinically applicable biomarkers development is growing rapidly. There are many methods to biomarker discovery and identification. In this review, we aim to summarize Mass spectrometry (MS)-based proteomics studies on AD and discuss thoroughly the methods to identify candidate biomarkers in cerebrospinal fluid (CSF) and blood. This review will also discuss the potential research areas on biomarkers.

Clinical utility of cerebrospinal fluid biomarkers in the diagnosis of early Alzheimer's disease

Several potential disease-modifying drugs for Alzheimer's disease (AD) have failed to show any effect on disease progression in clinical trials, conceivably because the AD subjects are already too advanced to derive clinical benefit from treatment and because diagnosis based on clinical criteria alone introduces a high misdiagnosis rate. Thus, well-validated biomarkers for early detection and accurate diagnosis are crucial. Low cerebrospinal fluid (CSF) concentrations of the amyloid-β (Aβ1-42) peptide, in combination with high total tau and phosphorylated tau, are sensitive and specific biomarkers highly predictive of progression to AD dementia in patients with mild cognitive impairment. However, interlaboratory variations in the results seen with currently available immunoassays are of concern. Recent worldwide standardization efforts and quality control programs include standard operating procedures for both preanalytical (e.g., lumbar puncture and sample handling) and analytical (e.g., preparation of calibration curve) procedures. Efforts are also ongoing to develop highly reproducible assays on fully automated instruments. These global standardization and harmonization measures will provide the basis for the generalized international application of CSF biomarkers for both clinical trials and routine clinical diagnosis of AD.

Preoperative cerebrospinal fluid β-Amyloid/Tau ratio and postoperative delirium

Objective

The neuropathogenesis of postoperative delirium remains unknown. Low cerebrospinal fluid (CSF) β-amyloid protein (Aβ) and high CSF Tau levels are associated with Alzheimer's disease. We, therefore, assessed whether lower preoperative CSF Aβ/Tau ratio was associated with higher incidence and greater severity of postoperative delirium.

Methods

One hundred and fifty-three participants (71 ± 5 years, 53% men) who had total hip/knee replacement under spinal anesthesia were enrolled. CSF was obtained during initiation of spinal anesthesia. The incidence and severity of postoperative delirium were determined by Confusion Assessment Method (CAM) and Memorial Delirium Assessment Scale (MDAS) on postoperative day 1 and 2. Aβ40, Aβ42, and Tau levels in the CSF were measured by enzyme-linked immunosorbent assay. The relationships among these variables were determined, adjusting for age and gender.

Results

Participants in the lowest quartile of preoperative CSF Aβ40/Tau and Aβ42/Tau ratio had higher incidence (32% vs. 17%, P = 0.0482) and greater symptom severity of postoperative delirium (Aβ40/Tau ratio: 4 vs. 3, P = 0.034; Aβ42/Tau ratio: 4 vs. 3, P = 0.062, the median of the highest MDAS score) as compared to the combination of the rest of the quartiles. The preoperative CSF Aβ40/Tau or Aβ42/Tau ratio was inversely associated with MDAS score (Aβ40/Tau ratio: −0.12 ± 0.05, P = 0.014, adj. −0.12 ± 0.05, P = 0.018; Aβ42/Tau ratio: −0.65 ± 0.26, P = 0.013, adj. −0.62 ± 0.27, P = 0.022).

Interpretation

Lower CSF Aβ/Tau ratio could be associated with postoperative delirium, pending confirmation of our preliminary results in further studies. These findings suggest potential roles of Aβ and/or Tau in postoperative delirium neuropathogenesis.

Biomarkers in amyloid-β immunotherapy trials in Alzheimer's disease

Drug candidates directed against amyloid-β (Aβ) are mainstream in Alzheimer's disease (AD) drug development. Active and passive Aβ immunotherapy is the principle that has come furthest, both in number and in stage of clinical trials. However, an increasing number of reports on major difficulties in identifying any clinical benefit in phase II-III clinical trials on this type of anti-Aβ drug candidates have caused concern among researchers, pharmaceutical companies, and other stakeholders. This has provided critics of the amyloid cascade hypothesis with fire for their arguments that Aβ deposition may merely be a bystander, and not the cause, of the disease or that the amyloid hypothesis may only be valid for the familial form of AD. On the other hand, most researchers argue that it is the trial design that will need refinement to allow for identifying a positive clinical effect of anti-Aβ drugs. A consensus in the field is that future trials need to be performed in an earlier stage of the disease and that biomarkers are essential to guide and facilitate drug development. In this context, it is reassuring that, in contrast to most brain disorders, research advances in the AD field have led to both imaging (magnetic resonance imaging (MRI) and PET) and cerebrospinal fluid (CSF) biomarkers for the central pathogenic processes of the disease. AD biomarkers will have a central role in future clinical trials to enable early diagnosis, and Aβ biomarkers (CSF Aβ42 and amyloid PET) may be essential to allow for testing a drug on patients with evidence of brain Aβ pathology. Pharmacodynamic Aβ and amyloid precursor protein biomarkers will be of use to verify target engagement of a drug candidate in humans, thereby bridging the gap between mechanistic data from transgenic AD models (that may not be relevant to the neuropathology of human AD) and large and expensive phase III trials. Last, downstream biomarker evidence (CSF tau proteins and MRI volumetry) that the drug ameliorates neurodegeneration will, together with beneficial clinical effects on cognition and functioning, be essential for labeling an anti-Aβ drug as disease modifying.

Fluid biomarkers for diagnosing dementia: rationale and the Canadian Consensus on Diagnosis and Treatment of Dementia recommendations for Canadian physicians

Fluid biomarkers improve the diagnostic accuracy in dementia and provide an objective measure potentially useful as a therapeutic response in clinical trials. The role of fluid biomarkers in patient care is a rapidly evolving field. Here, we provide a review and recommendations regarding the use of fluid biomarkers in clinical practice as discussed at the Fourth Canadian Consensus Conference on the Diagnosis and Treatment of Dementia (CCCDTD4) convened in Montreal, 4 to 5 May 2012. At present, there is no consensus regarding the optimal methodology for conducting quantification of plasma amyloid-beta (Aβ) peptides. In addition, since there is insufficient evidence supporting clinical applications for plasma Aβ-peptide measures, the CCCDTD4 does not recommended plasma biomarkers either for primary care or for specialists. Evidence for CSF Aβ1-42, total tau and phosphorylated tau in the diagnosis of Alzheimer pathology is much stronger, and can be considered at the tertiary care level for selected cases to improve diagnostic certainty, particularly in those cases presenting atypical clinical features.

Clinical trials in predementia stages of Alzheimer disease

Effective treatments of Alzheimer disease (AD) dementia are an urgent necessity. There is a growing consensus that effective disease-modifying treatment before the onset of clinical dementia and slowing the progression of mild symptoms are needed after recent setbacks in AD therapeutics. The identification of at-risk and preclinical AD populations is becoming important for targeting primary and secondary prevention clinical trials in AD. This article reviews the strategies and challenges in targeting at-risk and preclinical AD populations for a new generation of AD clinical trials. Design, outcome measures, and complexities in successfully completing a clinical trial targeting this population are reviewed.

Persistence of cholinesterase inhibitor treatment in dementia: insights from a naturalistic study

BACKGROUND

Cholinesterase inhibitors (ChEI) are widely used in dementia, but there is a lack of practice guidelines in case of intolerance or absence of perceived effect.

METHODS

Two hundred and forty patients (mean age 77 years, SD 6.3, 66% female) with Alzheimer's disease or Lewy body dementia were prescribed a ChEI and evaluated annually under conditions of standard practice. Of these, 152 patients maintained, 36 switched, and 52 abandoned ChEI treatment.

RESULTS

Less behavioural disturbance and less cognitive deterioration were observed, respectively, at the 3- and 4-year follow-up assessments in the patients who maintained the first prescribed ChEI (p < 0.05). Cognitive benefits were reinforced in the patients who experienced some adverse event, but no benefits were observed when the patient or caregiver did not perceive an effect.

CONCLUSIONS

Maintenance of the first prescribed ChEI was supported when some benefit was perceived by the patient or caregiver, even in cases of nonserious adverse events.

Functional response to cholinesterase inhibitor therapy in a naturalistic Alzheimer's disease cohort

BACKGROUND

Activities of daily living (ADL) are an essential part of the diagnostic criteria for Alzheimer's disease (AD). A decline in ADL affects independent living and has a strong negative impact on caregiver burden. Functional response to cholinesterase inhibitor (ChEI) treatment and factors that might influence this response in naturalistic AD patients need investigating. The aim of this study was to identify the socio-demographic and clinical factors that affect the functional response after 6 months of ChEI therapy.

METHODS

This prospective, non-randomised, multicentre study in a routine clinical setting included 784 AD patients treated with donepezil, rivastigmine or galantamine. At baseline and after 6 months of treatment, patients were assessed using several rating scales, including the Instrumental Activities of Daily Living (IADL) scale, Physical Self-Maintenance Scale (PSMS) and Mini-Mental State Examination (MMSE). Demographic and clinical characteristics were investigated at baseline. The functional response and the relationships of potential predictors were analysed using general linear models.

RESULTS

After 6 months of ChEI treatment, 49% and 74% of patients showed improvement/no change in IADL and in PSMS score, respectively. The improved/unchanged patients exhibited better cognitive status at baseline; regarding improved/unchanged PSMS, patients were younger and used fewer anti-depressants. A more positive functional response to ChEI was observed in younger individuals or among those having the interaction effect of better preserved cognition and lower ADL ability. Patients with fewer concomitant medications or those using NSAIDs/acetylsalicylic acid showed a better PSMS response.

CONCLUSIONS

Critical characteristics that may influence the functional response to ChEI in AD were identified. Some predictors differed from those previously shown to affect cognitive response, e.g., lower cognitive ability and older age predicted better cognitive but worse functional response.

Fluid biomarkers in Alzheimer disease

Research progress has provided detailed understanding of the molecular pathogenesis of Alzheimer disease (AD). This knowledge has been translated into new drug candidates with putative disease-modifying effects, which are now being tested in clinical trials. The promise of effective therapy has created a great need for biomarkers able to detect AD in the predementia phase, because drugs will probably be effective only if neurodegeneration is not too advanced. In this chapter, cerebrospinal fluid (CSF) and plasma biomarkers are reviewed. The core CSF biomarkers total tau (T-tau), phosphorylated tau (P-tau) and the 42 amino acid form of β-amyloid (Aβ42) reflect AD pathology, and have high diagnostic accuracy to diagnose AD with dementia and prodromal AD in mild cognitive impairment cases. The rationale for the use of CSF biomarkers to identify and monitor the mechanism of action of new drug candidates is also outlined in this chapter.

Simultaneous analysis of cerebrospinal fluid biomarkers using microsphere-based xMAP multiplex technology for early detection of Alzheimer's disease

The xMAP-Luminex multiplex platform for measurement of Alzheimer's disease (AD) cerebrospinal fluid (CSF) biomarkers using Innogenetics AlzBio3 immunoassay reagents that are for research use only has been shown to be an effective tool for early detection of an AD-like biomarker signature based on concentrations of CSF Aβ(1-42), t-tau and p-tau(181). Among the several advantages of the xMAP-Luminex platform for AD CSF biomarkers are: a wide dynamic range of ready-to-use calibrators, time savings for the simultaneous analyses of three biomarkers in one analytical run, reduction of human error, potential of reduced cost of reagents, and a modest reduction of sample volume as compared to conventional enzyme-linked immunosorbant assay (ELISA) methodology. Recent clinical studies support the use of CSF Aβ(1-42), t-tau and p-tau(181) measurement using the xMAP-Luminex platform for the early detection of AD pathology in cognitively normal individuals, and for prediction of progression to AD dementia in subjects with mild cognitive impairment (MCI). Studies that have shown the prediction of risk for progression to AD dementia by MCI patients provide the basis for the use of CSF Aβ(1-42), t-tau and p-tau(181) testing to assign risk for progression in patients enrolled in therapeutic trials. Furthermore emerging study data suggest that these pathologic changes occur in cognitively normal subjects 20 or more years before the onset of clinically detectable memory changes thus providing an objective measurement for use in the assessment of treatment effects in primary treatment trials. However, numerous previous ELISA and Luminex-based multiplex studies reported a wide range of absolute values of CSF Aβ(1-42), t-tau and p-tau(181) indicative of substantial inter-laboratory variability as well as varying degrees of intra-laboratory imprecision. In order to address these issues a recent inter-laboratory investigation that included a common set of CSF pool aliquots from controls as well as AD patients over a range of normal and pathological Aβ(1-42), t-tau and p-tau(181) values as well as agreed-on standard operating procedures (SOPs) assessed the reproducibility of the multiplex methodology and Innogenetics AlzBio3 immunoassay reagents. This study showed within-center precision values of 5% to a little more than 10% and good inter-laboratory %CV values (10-20%). There are several likely factors influencing the variability of CSF Aβ(1-42), t-tau and p-tau(181) measurements. In this review, we describe the pre-analytical, analytical and post-analytical sources of variability including sources inherent to kits, and describe procedures to decrease the variability. A CSF AD biomarker Quality Control program has been established and funded by the Alzheimer Association, and global efforts are underway to further define optimal pre-analytical SOPs and best practices for the methodologies available or in development including plans for production of a standard reference material that could provide for a common standard against which manufacturers of immunoassay kits would assign calibration standard values.

Granular expression of prolyl-peptidyl isomerase PIN1 is a constant and specific feature of Alzheimer's disease pathology and is independent of tau, Aβ and TDP-43 pathology

Alzheimer's disease (AD) manifests with progressive memory loss and decline of spatial awareness and motor skills. Neurofibrillary tangles (NFTs) represent one of the pathological hallmarks of AD. Previous studies suggest that the enzyme prolyl-peptidyl cis-trans isomerase PIN1 [protein interacting with NIMA (never in mitosis A)-1] recognizes hyperphosphorylated tau (in NFTs) and facilitates its dephosphorylation, thereby recovering its function. This study aims to determine the frequency, severity and distribution of PIN1 immunoreactivity and its relationship to NFTs and other neuropathological markers of neurodegeneration such as amyloid-β (Aβ) plaques and transcription-responsive DNA-binding protein of M(r) 43 kDa (TDP-43). Immunohistochemical analysis of 194 patients (46 with AD, 43 with Parkinson's disease/dementia with Lewy bodies, 12 with progressive supranuclear palsy/corticobasal degeneration, 36 with frontotemporal lobar degeneration, 21 with motor neuron disease and 34 non-demented (ND) individuals) revealed an increased frequency and severity of PIN1 immunoreactive inclusions in AD as compared to all diagnostic groups (P < 0.001). The hippocampal and cortical distribution of PIN1 granules was distinct from that of NFTs, Aβ and TDP-43 pathologies, though the frequency of neurons with PIN1 immunoreactivity increased with increasing NFT pathology. There was a progressive increase in PIN1 changes in ND individuals as the degree of AD-type pathological changes increased. Present findings indicate that PIN1 changes are a constant feature of AD pathology and could serve as a biomarker of the onset or spread of AD neuropathology independent of tau or Aβ.

Managing cognitive dysfunction through the continuum of Alzheimer's disease: role of pharmacotherapy

It has been shown that, during several years preceding the diagnosis of Alzheimer's disease there is a gradual cognitive decline with a continuum between the pre-dementia stage (still known as the prodromal stage but now included within the general concept of mild cognitive impairment [MCI]) and the other stages of the disease. In MCI, the use of cholinesterase inhibitors (ChEIs) is not associated with any delay in the onset of Alzheimer's disease or dementia. During the dementia stages, the three ChEIs (donepezil, galantamine and rivastigmine) are efficacious for mild to moderate Alzheimer's disease; therefore, monotherapy with a ChEI can be envisaged as initial treatment. Confirmation of the efficacy of ChEIs in the mild dementia stage is essentially based on the results from a single, randomized study carried out specifically among patients at this stage of severity. Memantine can represent an alternative to ChEIs in the moderate stage of Alzheimer's disease. At the severe stage of the disease, memantine and donepezil are currently indicated. Indeed, memantine has been approved by numerous drug regulatory agencies for use in severe stages of the disease, whereas donepezil has only been approved by the US FDA. There is currently insufficient evidence for recommending combination therapy in Alzheimer's disease.

Cerebrospinal fluid total tau as a marker of Alzheimer's disease intensity

OBJECTIVES

The aim of this longitudinal study was to test the hypothesis that CSF biomarkers in AD patients also may be forward-looking measures that are associated not only with the degree and profile of cognitive impairment but also with changes in cognition over time.

METHODS

Here, we assessed the association of CSF Abeta42, T-tau and P-tau with neuropsychological scores of disease severity, as well as the rate of disease progression, in 142 patients with Alzheimer's disease. All patients were part of a 3-year prospective longitudinal treatment study.

RESULTS

A more rapid progress in MMSE score reduction was seen in AD patients with T-tau levels higher than the upper quartile (800 ng/L) compared with Alzheimer's disease patients with lower T-tau levels (p = 0.008). We also found that individuals with T-tau > 800 ng/L performed worse in total scores and especially in memory and orientation when assessed with MMSE and ADAS cog than patients with T-tau <800 ng/L. Similar results were obtained for P-tau. No associations were seen between Abeta42 and cognitive scores or disease progression.

DISCUSSION

These findings support the hypothesis that increased levels of T-tau reflect the intensity of the disease and are associated with a more rapid disease progress.

Cerebrospinal fluid and plasma biomarkers in Alzheimer disease

Intense multidisciplinary research has provided detailed knowledge of the molecular pathogenesis of Alzheimer disease (AD). This knowledge has been translated into new therapeutic strategies with putative disease-modifying effects. Several of the most promising approaches, such as amyloid-beta immunotherapy and secretase inhibition, are now being tested in clinical trials. Disease-modifying treatments might be at their most effective when initiated very early in the course of AD, before amyloid plaques and neurodegeneration become too widespread. Thus, biomarkers are needed that can detect AD in the predementia phase or, ideally, in presymptomatic individuals. In this Review, we present the rationales behind and the diagnostic performances of the core cerebrospinal fluid (CSF) biomarkers for AD, namely total tau, phosphorylated tau and the 42 amino acid form of amyloid-beta. These biomarkers reflect AD pathology, and are candidate markers for predicting future cognitive decline in healthy individuals and the progression to dementia in patients who are cognitively impaired. We also discuss emerging plasma and CSF biomarkers, and explore new proteomics-based strategies for identifying additional CSF markers. Furthermore, we outline the roles of CSF biomarkers in drug discovery and clinical trials, and provide perspectives on AD biomarker discovery and the validation of such markers for use in the clinic.

Cholinesterase inhibitors in Alzheimer's disease and Lewy body spectrum disorders: the emerging pharmacogenetic story

This review provides an update on the current state of pharmacogenetic research in the treatment of Alzheimer's disease (AD) and Lewy body disease (LBD) as it pertains to the use of cholinesterase inhibitors (ChEI). AD and LBD are first reviewed from clinical and pathophysiological perspectives. This is followed by a discussion of ChEIs used in the symptomatic treatment of these conditions, focusing on their unique and overlapping pharmacokinetic and pharmacodynamic profiles, which can be used to identify candidate genes for pharmacogenetics studies. The literature published to date is then reviewed and limitations are discussed. This is followed by a discussion of potential endophenotypes which may help to refine future pharmacogenetic studies of response and adverse effects to ChEIs.