Association of Amyloid Reduction After Donanemab Treatment With Tau Pathology and Clinical Outcomes: The TRAILBLAZER-ALZ Randomized Clinical Trial

Advanced brain imaging for the diagnosis of Alzheimer disease

PURPOSE OF REVIEW

The purpose is to review the latest advances of brain imaging for the diagnosis of Alzheimer disease (AD).

RECENT FINDINGS

Brain imaging techniques provide valuable and complementary information to support the diagnosis of Alzheimer disease in clinical and research settings. The recent FDA accelerated approvals of aducanumab, lecanemab and donanemab made amyloid-PET critical in helping determine the optimal window for anti-amyloid therapeutic interventions. Tau-PET, on the other hand, is considered of key importance for the tracking of disease progression and for monitoring therapeutic interventions in clinical trials. PET imaging for microglial activation, astrocyte reactivity and synaptic degeneration are still new techniques only used in the research field, and more studies are needed to validate their use in the clinical diagnosis of AD. Finally, artificial intelligence has opened new prospective in the early detection of AD using MRI modalities.

SUMMARY

Brain imaging techniques using PET improve our understanding of the different AD-related pathologies and their relationship with each other along the course of disease. With more robust validation, machine learning and deep learning algorithms could be integrated with neuroimaging modalities to serve as valuable tools for clinicians to make early diagnosis and prognosis of AD.

Validation of quantitative assessment of florbetaben PET scans as an adjunct to the visual assessment across 15 software methods

PURPOSE

Amyloid positron emission tomography (PET) with [18F]florbetaben (FBB) is an established tool for detecting Aβ deposition in the brain in vivo based on visual assessment of PET scans. Quantitative measures are commonly used in the research context and allow continuous measurement of amyloid burden. The aim of this study was to demonstrate the robustness of FBB PET quantification.

METHODS

This is a retrospective analysis of FBB PET images from 589 subjects. PET scans were quantified with 15 analytical methods using nine software packages (MIMneuro, Hermes BRASS, Neurocloud, Neurology Toolkit, statistical parametric mapping (SPM8), PMOD Neuro, CapAIBL, non-negative matrix factorization (NMF), AmyloidIQ) that used several metrics to estimate Aβ load (SUVR, centiloid, amyloid load, and amyloid index). Six analytical methods reported centiloid (MIMneuro, standard centiloid, Neurology Toolkit, SPM8 (PET only), CapAIBL, NMF). All results were quality controlled.

RESULTS

The mean sensitivity, specificity, and accuracy were 96.1 ± 1.6%, 96.9 ± 1.0%, and 96.4 ± 1.1%, respectively, for all quantitative methods tested when compared to histopathology, where available. The mean percentage of agreement between binary quantitative assessment across all 15 methods and visual majority assessment was 92.4 ± 1.5%. Assessments of reliability, correlation analyses, and comparisons across software packages showed excellent performance and consistent results between analytical methods.

CONCLUSION

This study demonstrated that quantitative methods using both CE marked software and other widely available processing tools provided comparable results to visual assessments of FBB PET scans. Software quantification methods, such as centiloid analysis, can complement visual assessment of FBB PET images and could be used in the future for identification of early amyloid deposition, monitoring disease progression and treatment effectiveness.

Whole Person Modeling: a transdisciplinary approach to mental health research

The growing global burden of mental illness has prompted calls for innovative research strategies. Theoretical models of mental health include complex contributions of biological, psychosocial, experiential, and other environmental influences. Accordingly, neuropsychiatric research has self-organized into largely isolated disciplines working to decode each individual contribution. However, research directly modeling objective biological measurements in combination with cognitive, psychological, demographic, or other environmental measurements is only now beginning to proliferate. This review aims to (1) to describe the landscape of modern mental health research and current movement towards integrative study, (2) to provide a concrete framework for quantitative integrative research, which we call Whole Person Modeling, (3) to explore existing and emerging techniques and methods used in Whole Person Modeling, and (4) to discuss our observations about the scarcity, potential value, and untested aspects of highly transdisciplinary research in general. Whole Person Modeling studies have the potential to provide a better understanding of multilevel phenomena, deliver more accurate diagnostic and prognostic tests to aid in clinical decision making, and test long standing theoretical models of mental illness. Some current barriers to progress include challenges with interdisciplinary communication and collaboration, systemic cultural barriers to transdisciplinary career paths, technical challenges in model specification, bias, and data harmonization, and gaps in transdisciplinary educational programs. We hope to ease anxiety in the field surrounding the often mysterious and intimidating world of transdisciplinary, data-driven mental health research and provide a useful orientation for students or highly specialized researchers who are new to this area.

Donanemab in Early Symptomatic Alzheimer Disease: The TRAILBLAZER-ALZ 2 Randomized Clinical Trial

Importance

There are limited efficacious treatments for Alzheimer disease.

Objective

To assess efficacy and adverse events of donanemab, an antibody designed to clear brain amyloid plaque.

Design, Setting, and Participants

Multicenter (277 medical research centers/hospitals in 8 countries), randomized, double-blind, placebo-controlled, 18-month phase 3 trial that enrolled 1736 participants with early symptomatic Alzheimer disease (mild cognitive impairment/mild dementia) with amyloid and low/medium or high tau pathology based on positron emission tomography imaging from June 2020 to November 2021 (last patient visit for primary outcome in April 2023).

Interventions

Participants were randomized in a 1:1 ratio to receive donanemab (n = 860) or placebo (n = 876) intravenously every 4 weeks for 72 weeks. Participants in the donanemab group were switched to receive placebo in a blinded manner if dose completion criteria were met.

Main Outcomes and Measures

The primary outcome was change in integrated Alzheimer Disease Rating Scale (iADRS) score from baseline to 76 weeks (range, 0-144; lower scores indicate greater impairment). There were 24 gated outcomes (primary, secondary, and exploratory), including the secondary outcome of change in the sum of boxes of the Clinical Dementia Rating Scale (CDR-SB) score (range, 0-18; higher scores indicate greater impairment). Statistical testing allocated α of .04 to testing low/medium tau population outcomes, with the remainder (.01) for combined population outcomes.

Results

Among 1736 randomized participants (mean age, 73.0 years; 996 [57.4%] women; 1182 [68.1%] with low/medium tau pathology and 552 [31.8%] with high tau pathology), 1320 (76%) completed the trial. Of the 24 gated outcomes, 23 were statistically significant. The least-squares mean (LSM) change in iADRS score at 76 weeks was -6.02 (95% CI, -7.01 to -5.03) in the donanemab group and -9.27 (95% CI, -10.23 to -8.31) in the placebo group (difference, 3.25 [95% CI, 1.88-4.62]; P < .001) in the low/medium tau population and -10.2 (95% CI, -11.22 to -9.16) with donanemab and -13.1 (95% CI, -14.10 to -12.13) with placebo (difference, 2.92 [95% CI, 1.51-4.33]; P < .001) in the combined population. LSM change in CDR-SB score at 76 weeks was 1.20 (95% CI, 1.00-1.41) with donanemab and 1.88 (95% CI, 1.68-2.08) with placebo (difference, -0.67 [95% CI, -0.95 to -0.40]; P < .001) in the low/medium tau population and 1.72 (95% CI, 1.53-1.91) with donanemab and 2.42 (95% CI, 2.24-2.60) with placebo (difference, -0.7 [95% CI, -0.95 to -0.45]; P < .001) in the combined population. Amyloid-related imaging abnormalities of edema or effusion occurred in 205 participants (24.0%; 52 symptomatic) in the donanemab group and 18 (2.1%; 0 symptomatic during study) in the placebo group and infusion-related reactions occurred in 74 participants (8.7%) with donanemab and 4 (0.5%) with placebo. Three deaths in the donanemab group and 1 in the placebo group were considered treatment related.

Conclusions and Relevance

Among participants with early symptomatic Alzheimer disease and amyloid and tau pathology, donanemab significantly slowed clinical progression at 76 weeks in those with low/medium tau and in the combined low/medium and high tau pathology population.

Trial Registration

ClinicalTrials.gov Identifier: NCT04437511.

Current and future therapeutic strategies for Alzheimer's disease: an overview of drug development bottlenecks

Alzheimer's disease (AD) is the most common chronic neurodegenerative disease worldwide. It causes cognitive dysfunction, such as aphasia and agnosia, and mental symptoms, such as behavioral abnormalities; all of which place a significant psychological and economic burden on the patients' families. No specific drugs are currently available for the treatment of AD, and the current drugs for AD only delay disease onset and progression. The pathophysiological basis of AD involves abnormal deposition of beta-amyloid protein (Aβ), abnormal tau protein phosphorylation, decreased activity of acetylcholine content, glutamate toxicity, autophagy, inflammatory reactions, mitochondria-targeting, and multi-targets. The US Food and Drug Administration (FDA) has approved five drugs for clinical use: tacrine, donepezil, carbalatine, galantamine, memantine, and lecanemab. We have focused on the newer drugs that have undergone clinical trials, most of which have not been successful as a result of excessive clinical side effects or poor efficacy. Although aducanumab received rapid approval from the FDA on 7 June 2021, its long-term safety and tolerability require further monitoring and confirmation. In this literature review, we aimed to explore the possible pathophysiological mechanisms underlying the occurrence and development of AD. We focused on anti-Aβ and anti-tau drugs, mitochondria-targeting and multi-targets, commercially available drugs, bottlenecks encountered in drug development, and the possible targets and therapeutic strategies for future drug development. We hope to present new concepts and methods for future drug therapies for AD.

Comparative Study of Safety and Efficacy of Angiotensin-Receptor Blockers and Anti Amyloid-ß Monoclonal Antibodies for the Treatment of Alzheimer's Disease: A Systematic Review

Amyloid-ß (Aß) plaques and Neurofibrillary tangles are hallmarks of Alzheimer's disease (AD) pathology. Recent advances to find a cure for AD have led to the exploration of Anti-Aß monoclonal antibodies and angiotensin-receptor blockers (ARBs). The antibodies can decrease plaque formation or remove already formed plaques. ARBs increase angiotensin II (AT2) levels and decrease the effect of AT2 on the AT1 receptor (AT1R). This systematic analysis reviews evidence of monoclonal antibodies (Aducanumab, Lecanemab, Donanemab, and Solanezumab) and ARBs in managing AD. An in-depth methodical search was conducted across PubMed, Science Direct, and Mendeley. PRISMA 2020 guidelines were followed for this study. Randomized control trials for antibodies and ARBs and one retrospective cohort study were included. The comparison was made among studies that shared similar measured outcomes. Antibodies were found to be more effective than ARBs, with Aducanumab and Lecanemab being the most effective. ARBs, on the other hand, were found to be the safer choice. Further trials of longer duration and larger sample sizes are needed to explore both groups' long-term safety and efficacy.

Unraveling Molecular and Genetic Insights into Neurodegenerative Diseases: Advances in Understanding Alzheimer's, Parkinson's, and Huntington's Diseases and Amyotrophic Lateral Sclerosis

Neurodegenerative diseases are, according to recent studies, one of the main causes of disability and death worldwide. Interest in molecular genetics has started to experience exponential growth thanks to numerous advancements in technology, shifts in the understanding of the disease as a phenomenon, and the change in the perspective regarding gene editing and the advantages of this action. The aim of this paper is to analyze the newest approaches in genetics and molecular sciences regarding four of the most important neurodegenerative disorders: Alzheimer's disease, Parkinson's disease, Huntington's disease, and amyotrophic lateral sclerosis. We intend through this review to focus on the newest treatment, diagnosis, and predictions regarding this large group of diseases, in order to obtain a more accurate analysis and to identify the emerging signs that could lead to a better outcome in order to increase both the quality and the life span of the patient. Moreover, this review could provide evidence of future possible novel therapies that target the specific genes and that could be useful to be taken into consideration when the classical approaches fail to shed light.

Comparison of Group-Level and Individualized Brain Regions for Measuring Change in Longitudinal Tau Positron Emission Tomography in Alzheimer Disease

Importance

Longitudinal tau positron emission tomography (PET) is a relevant outcome in clinical trials evaluating disease-modifying therapies in Alzheimer disease (AD). A key unanswered question is whether the use of participant-specific (individualized) regions of interest (ROIs) is superior to conventional approaches where the same ROI (group-level) is used for each participant.

Objective

To compare group- and participant-level ROIs in participants at different stages of the AD clinical continuum in terms of annual percentage change in tau-PET standardized uptake value ratio (SUVR) and sample size requirements.

Design, Setting, and Participants

This was a longitudinal cohort study with consecutive participant enrollment between September 18, 2017, and November 15, 2021. Included in the analysis were participants with mild cognitive impairment and AD dementia from the prospective and longitudinal Swedish Biomarkers For Identifying Neurodegenerative Disorders Early and Reliably 2 (BioFINDER-2) study; in addition, a validation sample (the AVID 05e, Expedition-3, Alzheimer's Disease Neuroimaging Initiative [ADNI], and BioFINDER-1 study cohorts) was also included.

Exposures

Tau PET (BioFINDER-2, [18F]RO948; validation sample, [18F]flortaucipir), 7 group-level (5 data-driven stages, meta-temporal, whole brain), and 5 individualized ROIs.

Main Outcomes and Measures

Annual percentage change in tau-PET SUVR across ROIs. Sample size requirements in simulated clinical trials using tau PET as an outcome were also calculated.

Results

A total of 215 participants (mean [SD] age, 71.4 (7.5) years; 111 male [51.6%]) from the BioFINDER-2 study were included in this analysis: 97 amyloid-β (Aβ)-positive cognitively unimpaired (CU) individuals, 77 with Aβ-positive mild cognitive impairment (MCI), and 41 with AD dementia. In the validation sample were 137 Aβ-positive CU participants, 144 with Aβ-positive MCI, and 125 with AD dementia. Mean (SD) follow-up time was 1.8 (0.3) years. Using group-level ROIs, the largest annual percentage increase in tau-PET SUVR in Aβ-positive CU individuals was seen in a composite ROI combining the entorhinal cortex, hippocampus, and amygdala (4.29%; 95% CI, 3.42%-5.16%). In individuals with Aβ-positive MCI, the greatest change was seen in the temporal cortical regions (5.82%; 95% CI, 4.67%-6.97%), whereas in those with AD dementia, the greatest change was seen in the parietal regions (5.22%; 95% CI, 3.95%-6.49%). Significantly higher estimates of annual percentage change were found using several of the participant-specific ROIs. Importantly, the simplest participant-specific approach, where change in tau PET was calculated in an ROI that best matched the participant's data-driven disease stage, performed best in all 3 subgroups. For the power analysis, sample size reductions for the participant-specific ROIs ranged from 15.94% (95% CI, 8.14%-23.74%) to 72.10% (95% CI, 67.10%-77.20%) compared with the best-performing group-level ROIs. Findings were replicated using [18F]flortaucipir.

Conclusions and Relevance

Finding suggest that certain individualized ROIs carry an advantage over group-level ROIs for assessing longitudinal tau changes and increase the power to detect treatment effects in AD clinical trials using longitudinal tau PET as an outcome.

Donanemab exposure and efficacy relationship using modeling in Alzheimer's disease

INTRODUCTION

Donanemab is an amyloid-targeting therapy that specifically targets brain amyloid plaques. The objective of these analyses was to characterize the relationship of donanemab exposure with plasma biomarkers and clinical efficacy through modeling.

METHODS

Data for the analyses were from participants with Alzheimer's disease from the phase 1 and TRAILBLAZER-ALZ studies. Indirect-response models were used to fit plasma phosphorylated tau 217 (p-tau217) and plasma glial fibrillated acidic protein (GFAP) data over time. Disease-progression models were developed using pharmacokinetic/pharmacodynamic modeling.

RESULTS

The plasma p-tau217 and plasma GFAP models adequately predicted the change over time, with donanemab resulting in decreased plasma p-tau217 and plasma GFAP concentrations. The disease-progression models confirmed that donanemab significantly reduced the rate of clinical decline. Simulations revealed that donanemab slowed disease progression irrespective of baseline tau positron emission tomography (PET) level within the evaluated population.

DISCUSSION

The disease-progression models show a clear treatment effect of donanemab on clinical efficacy regardless of baseline disease severity.

Donanemab Population Pharmacokinetics, Amyloid Plaque Reduction, and Safety in Participants with Alzheimer's Disease

Donanemab is an amyloid-targeting therapy that resulted in robust amyloid plaque reduction and slowed Alzheimer's disease (AD) progression compared with placebo in the phase II TRAILBLAZER-ALZ study (NCT03367403). The objectives of the current analyses are to characterize (i) the population pharmacokinetics of donanemab, (ii) the relationship between donanemab exposure and amyloid plaque reduction (response), and (iii) the relationship between donanemab exposure and amyloid-related imaging abnormalities with edema or effusions (ARIA-E). Model development included data from participants with mild cognitive impairment or mild to moderate dementia due to AD from the phase Ib study on donanemab (NCT02624778) and participants with early symptomatic AD from the TRAILBLAZER-ALZ study. The analysis showed donanemab has a terminal elimination half-life of 11.8 days. Body weight and antidrug antibody titer impact donanemab exposure but not the pharmacodynamic response. Maintaining a donanemab serum concentration above 4.43 μg/mL (95% confidence interval: 0.956, 10.4) is associated with amyloid plaque reduction. The time to achieve amyloid plaque clearance (amyloid plaque level < 24.1 Centiloids) varied depending on the baseline amyloid level, where higher baseline levels were associated with fewer participants achieving amyloid clearance. The majority of participants achieved amyloid clearance by 52 weeks on treatment. Apolipoprotein ε4 carriers, irrespective of donanemab serum exposure, were 4 times more likely than noncarriers to have an ARIA-E event by 24 weeks.

Tau; One Protein, So Many Diseases

Tau, a member of the microtubule-associated proteins, is a known component of the neuronal cytoskeleton; however, in the brain tissue, it is involved in other vital functions beyond maintaining the cellular architecture. The pathologic tau forms aggregates inside the neurons and ultimately forms the neurofibrillary tangles. Intracellular and extracellular accumulation of different tau isoforms, including dimers, oligomers, paired helical filaments and tangles, lead to a highly heterogenous group of diseases named "Tauopathies". About twenty-six different types of tauopathy diseases have been identified that have different clinical phenotypes or pathophysiological characteristics. Although all these diseases are identified by tau aggregation, they are distinguishable based on the specific tau isoforms, the affected cell types and the brain regions. The neuropathological and phenotypical heterogeneity of these diseases impose significant challenges for discovering new diagnostic and therapeutic strategies. Here, we review the recent literature on tau protein and the pathophysiological mechanisms of tauopathies. This article mainly focuses on physiologic and pathologic tau and aims to summarize the upstream and downstream events and discuss the current diagnostic approaches and therapeutic strategies.

[Parkinson's disease and Alzheimer type dementia-Pathophysiology and drug treatment approaches]

Symptomatically effective forms of treatment for neurodegenerative diseases have been developed in the last 50 years based on the knowledge about the pathophysiological and neurochemical context in the central nervous system. These so far represent the basis of available treatment options. Knowledge of the pathophysiological and neurochemical context, however, is not only necessary for the development of treatment but also enables a meaningful implementation of currently available substances. The most important neuropathological and neurochemical alterations that characterize Parkinson's disease and Alzheimer type dementia are briefly presented. In recent years, new substances ranging from symptomatic to disease-modifying treatment options have been developed, the latter mostly based on the neuropathologically detectable alterations. Recent results from clinical studies raise hopes that disease-modifying treatment options for neurodegenerative diseases will become available in the foreseeable future.

Role of monomeric amyloid-β in cognitive performance in Alzheimer's disease: Insights from clinical trials with secretase inhibitors and monoclonal antibodies

According to the β-amyloid (Aβ) hypothesis of Alzheimer's disease (AD), brain Aβ accumulation is the primary cascade event leading to cognitive deficit and dementia. Numerous anti-Aβ drugs either inhibiting production or aggregation of Aβ or stimulating its clearance have failed to show clinical benefit in large scale AD trials, with β- and γ-secretase inhibitors consistently worsening cognitive and clinical decline. In June 2021, the FDA approved aducanumab, an anti-Aβ monoclonal antibody for early AD based on its ability to reduce brain amyloid plaques, while two other amyloid-clearing antibodies (lecanemab and donanemab) have recently produced encouraging cognitive and clinical results. We reviewed AD trials using PubMed, meeting abstracts and ClinicalTrials.gov and evaluated the effects of such drugs on cerebrospinal fluid (CSF) Aβ levels, correlating them with cognitive effects. We found that β-secretase and γ-secretase inhibitors produce detrimental cognitive effects by significantly reducing CSF Aβ levels. We speculate that monoclonal antibodies targeting Aβ protofibrils, fibrils or plaques may improve cognitive performance in early AD by increasing soluble Aβ levels through Aβ aggregate disassembly and/or stabilization of existing Aβ monomers.These findings suggest that the real culprit in AD may be decreased levels of soluble monomeric Aβ due to sequestration into brain Aβ aggregates and plaques.

Antibodies to watch in 2023

In this 14th installment of the annual Antibodies to Watch article series, we discuss key events in commercial monoclonal antibody therapeutics development that occurred in 2022 and forecast events that might occur in 2023. As of mid-November, 12 antibody therapeutics had been granted first approvals in either the United States or European Union (tebentafusp (Kimmtrak), faricimab (Vabysmo), sutimlimab (Enjaymo), relatlimab (Opdualag), tixagevimab/cilgavimab (Evusheld), mosunetuzumab (Lunsumio), teclistamab (TECVAYLI), spesolimab (SPEVIGO), tremelimumab (Imjudo; combo with durvalumab), nirsevimab (Beyfortus), mirvetuximab soravtansine (ELAHERE™), and teplizumab (TZIELD)), including 4 bispecific antibodies and 1 ADC. Based on FDA action dates, several additional product candidates could be approved by the end of 2022. An additional seven were first approved in China or Japan in 2022, including two bispecific antibodies (cadonilimab and ozoralizumab). Globally, at least 24 investigational antibody therapeutics are undergoing review by regulatory agencies as of mid-November 2022. Our data show that, with antibodies for COVID-19 excluded, the late-stage commercial clinical pipeline grew by ~20% in the past year to include nearly 140 investigational antibody therapeutics that were designed using a wide variety of formats and engineering techniques. Of those in late-stage development, marketing application submissions for at least 23 may occur by the end of 2023, of which 5 are bispecific (odronextamab, erfonrilimab, linvoseltamab, zanidatamab, and talquetamab) and 2 are ADCs (datopotamab deruxtecan, and tusamitamab ravtansine).

Donanemab for Alzheimer's Disease: A Systematic Review of Clinical Trials

Amyloid-β (Aβ) plaques and aggregated tau are two core mechanisms that contribute to the clinical deterioration of Alzheimer’s disease (AD). Recently, targeted-Aβ plaque reduction immunotherapies have been explored for their efficacy and safety as AD treatment. This systematic review critically reviews the latest evidence of Donanemab, a humanized antibody that targets the reduction in Aβ plaques, in AD patients. Comprehensive systematic search was conducted across PubMed/MEDLINE, CINAHL Plus, Web of Science, Cochrane, and Scopus. This study adhered to PRISMA Statement 2020 guidelines. Adult patients with Alzheimer’s disease being intervened with Donanemab compared to placebo or standard of care in the clinical trial setting were included. A total of 396 patients across four studies received either Donanemab or a placebo (228 and 168 participants, respectively). The Aβ-plaque reduction was found to be dependent upon baseline levels, such that lower baseline levels had complete amyloid clearance (<24.1 Centiloids). There was a slowing of overall tau levels accumulation as well as relatively reduced functional and cognitive decline noted on the Integrated Alzheimer’s Disease Rating Scale by 32% in the Donanemab arm. The safety of Donanemab was established with key adverse events related to Amyloid-Related Imaging Abnormalities (ARIA), ranging between 26.1 and 30.5% across the trials. There is preliminary support for delayed cognitive and functional decline with Donanemab among patients with mild-to-moderate AD. It remains unclear whether Donenameb extends therapeutic benefits that can modify and improve the clinical status of AD patients. Further trials can explore the interplay between Aβ-plaque reduction and toxic tau levels to derive meaningful clinical benefits in AD patients suffering from cognitive impairment.

Alzheimer Disease Biomarkers in Clinical Practice: A Blood-Based Diagnostic Revolution

An estimated 6.1 million Americans live with cognitive impairment-a number that is expected to triple by 2050. Alzheimer disease (AD) is the most common cause of impairment. The development of blood-based biomarkers capable of detecting pathological changes of AD in living patients has the potential to revolutionize the diagnostic approach to cognitive impairment by enabling screening for AD using accessible, non-invasive measures of amyloid and tau neuropathology, with accuracy that increasingly approaches that seen with "gold standard" positron emission tomography and cerebrospinal fluid measures. Demand for biomarker testing is expected to intensify with the emergence of effective treatments for AD and related dementias. Clinicians in all fields must prepare to meet this demand. Primary care practitioners are well positioned to support dementia diagnosis and management, including the application and interpretation of biomarkers. This article reviews the current uses of AD biomarkers and the potential applications of emerging blood-based AD biomarkers in clinical practice.