Meaningful Clinical Changes in Alzheimer Disease Measured With the iADRS and Illustrated Using the Donanemab TRAILBLAZER-ALZ Study Findings

Clinical Benefits and Risks of Antiamyloid Antibodies in Sporadic Alzheimer Disease: Systematic Review and Network Meta-Analysis With a Web Application

BACKGROUND

Despite the increasing approval of antiamyloid antibodies for Alzheimer disease (AD), their clinical relevance and risk-benefit profile remain uncertain. The heterogeneity of AD and the limited availability of long-term clinical data make it difficult to establish a clear rationale for selecting one treatment over another.

OBJECTIVE

The aim of this work was to assess and compare the efficacy and safety of antiamyloid antibodies through an interactive online meta-analytic approach by performing conventional pair-wise meta-analyses and frequentist and Bayesian network meta-analyses of phase II and III clinical trial results. To achieve this, we developed AlzMeta.app 2.0, a freely accessible web application that enables researchers and clinicians to evaluate the relative and absolute risks and benefits of these therapies in real time, incorporating different prior choices and assumptions of baseline risks of disease progression and adverse events.

METHODS

We adhered to PRISMA-NMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses extension for reporting of systematic reviews with network meta-analysis) and GRADE (Grading of Recommendations, Assessment, Development, and Evaluation) guidelines for reporting and rating the certainty of evidence. Clinical trial reports (until September 30, 2024) were retrieved from PubMed, Google Scholar, and clinical trial databases (including ClinicalTrials.gov). Studies with <20 sporadic AD patients and a modified Jadad score <3 were excluded. Risk of bias was assessed with the RoB-2 tool. Relative risks and benefits have been expressed as risk ratios and standardized mean differences, with confidence, credible, and prediction intervals calculated for all outcomes. For significant results, the intervention effects were ranked in frequentist and Bayesian frameworks, and their clinical relevance was determined by the absolute risk per 1000 people and number needed to treat (NNT) for a wide range of control responses.

RESULTS

Among 7 treatments tested in 21,236 patients (26 studies with low risk of bias or with some concerns), donanemab was the best-ranked treatment on cognitive and functional measures, and it was almost 2 times more effective than aducanumab and lecanemab and significantly more beneficial than other treatments on the global (cognitive and functional) Clinical Dementia Rating Scale-Sum of Boxes (NNT=10, 95% CI 8-16). Special caution is required regarding cerebral edema and microbleeding due to the clinically relevant risks of edema for donanemab (NNT=8, 95% CI 5-16), aducanumab (NNT=10, 95% CI 6-17), and lecanemab (NNT=14, 95% CI 7-31), which may outweigh the benefits.

CONCLUSIONS

Our results showed that donanemab is more effective and has a safety profile similar to aducanumab and lecanemab, highlighting the need for treatment options with improved safety. Potential bias may have been introduced in the included trials due to unblinding caused by frequent cerebral edema and microbleeds, as well as the impact of the COVID-19 pandemic.

Assessing the clinical meaningfulness of slowing CDR-SB progression with disease-modifying therapies for Alzheimer's disease

INTRODUCTION

For many patients and caregivers, a major goal of disease-modifying treatments (DMTs) for Alzheimer's disease (AD) dementia is to extend independence in instrumental and basic activities of daily living (IADLs and BADLs). The goal of this study was to estimate the effect of treatments on the time remaining independent in IADLs and BADLs.

METHODS

Participants at the Knight Alzheimer Disease Research Center (Knight ADRC) who met eligibility criteria for recent DMT trials were studied: age ≥60 years at baseline, clinical diagnosis of very mild or mild AD dementia (global Clinical Dementia Rating [CDR] score 0.5 or 1), biomarker confirmation of amyloid pathology, and at least one follow-up CDR assessment within 5 years. For IADLs, a subset of the Functional Assessment Questionnaire (FAQ) was examined that rated the degree of independence in the following: paying bills, driving, remembering medications and appointments, and preparing meals. For BADLs, the Personal Care domain of the CDR was used. Mixed-effects logistic and ordinal regression models were used to examine the relationship between CDR Sum of Boxes (CDR-SB) and the individual functional outcomes and their components. The change in CDR-SB over time was estimated with linear mixed-effects models.

RESULTS

A total of 282 participants were followed for an average of 2.9 years (standard deviation [SD] 1.3 years). For 50% of individuals, loss of independence in IADLs occurred at CDR-SB >4.5 and in BADLs at CDR-SB >11.5. For individuals with a baseline CDR-SB = 2, treatment with lecanemab would extend independence in IADLs for 10 months (95% confidence interval [CI] 4-18 months) and treatment with donanemab in the low/medium tau group would extend independence in IADLs by 13 months (95% CI 6-24 months).

DISCUSSION

Independence in ADLs can be related to CDR-SB and used to demonstrate the effect of AD treatments in extending the time of independent function, a meaningful outcome for patients and their families.

Highlights

We estimated time to loss of independence for people with AD dementiaEstimating time to loss of independence can help with clinical decision-makingDisease-modifying treatments for AD dementia can extend independence.

Estimating the Economically Justifiable Price of Limited-Duration Treatment with Donanemab for Early Symptomatic Alzheimer's Disease in the United States

INTRODUCTION

The goal of this economic model is to estimate an economically justifiable price (EJP) for using donanemab for the treatment of early symptomatic Alzheimer's disease (AD) in the United States based on clinical data from the phase 3 TRAILBLAZER-ALZ 2 trial (NCT04437511).

METHODS

We adapted an AD Markov state-transition model developed by the Institute for Clinical and Economic Review to estimate the EJP for donanemab at different willingness-to-pay (WTP) thresholds from the health care system perspective and the societal perspective as co-base cases.

RESULTS

Assuming a WTP threshold of $150,000 per quality-adjusted life-year (QALY) gained, the model estimates a 1-year (13-dose) EJP for donanemab of $80,538 from the health care system perspective and $91,126 from the societal perspective; at a WTP threshold of $100,000 per QALY gained, the model estimates a 1-year (13-dose) EJP for donanemab of $44,691 from the health care system perspective and $55,419 from the societal perspective. Mean total treatment costs per patient at the $150,000 per QALY gained EJP derived from the health care system perspective were estimated at $77,812 based on the average number of doses of donanemab patients received in the co-base case analysis. One-way sensitivity analysis (OWSA) indicated that treatment efficacy, disease severity at the time of treatment initiation, and duration of treatment effect were the main drivers of the potential EJP.

CONCLUSIONS

Results from this modeling simulation informed by the TRAILBLAZER-ALZ 2 study support an EJP for limited-duration treatment with donanemab that exceeds per-dose list prices for currently available amyloid-targeting therapies, implying potentially lower lifetime costs and better value for money.

Recent Advances in Therapeutics for the Treatment of Alzheimer's Disease

The most prevalent chronic neurodegenerative illness in the world is Alzheimer's disease (AD). It results in mental symptoms including behavioral abnormalities and cognitive impairment, which have a substantial financial and psychological impact on the relatives of the patients. The review discusses various pathophysiological mechanisms contributing to AD, including amyloid beta, tau protein, inflammation, and other factors, while emphasizing the need for effective disease-modifying therapeutics that alter disease progression rather than merely alleviating symptoms. This review mainly covers medications that are now being studied in clinical trials or recently approved by the FDA that fall under the disease-modifying treatment (DMT) category, which alters the progression of the disease by targeting underlying biological mechanisms rather than merely alleviating symptoms. DMTs focus on improving patient outcomes by slowing cognitive decline, enhancing neuroprotection, and supporting neurogenesis. Additionally, the review covers amyloid-targeting therapies, tau-targeting therapies, neuroprotective therapies, and others. This evaluation specifically looked at studies on FDA-approved novel DMTs in Phase II or III development that were carried out between 2021 and 2024. A thorough review of the US government database identified clinical trials of biologics and small molecule drugs for 14 agents in Phase I, 34 in Phase II, and 11 in Phase III that might be completed by 2028.

Assessing the clinical meaningfulness of slowing CDR-SB progression with disease-modifying therapies for Alzheimer disease

INTRODUCTION

For many patients and caregivers, a major goal of disease-modifying treatments (DMT) for Alzheimer disease (AD) dementia is to extend independence in instrumental and basic activities of daily living (IADLs and BADLs). The goal of this study was to estimate the effect of treatments on the time remaining independent in IADLs and BADLs.

METHODS

Participants at the Knight Alzheimer Disease Research Center were selected who were potentially eligible for recent DMT trials: age ≥ 60 years at baseline, clinical diagnosis of very mild or mild AD dementia (global Clinical Dementia Rating® (CDR®) score 0.5 or 1), biomarker confirmation of amyloid pathology, and at least one follow-up CDR assessment within 5 years. For IADLs, a subset of the Functional Assessment Questionnaire (FAQ) was examined that rated the degree of independence in the following: paying bills, driving, remembering medications and appointments, and preparing meals. For BADLs, the Personal Care domain of the CDR was used. Mixed-effects logistic and ordinal regression models were used to examine the relationship between CDR Sum Boxes (CDR-SB) and the individual functional outcomes and their components. The change in CDR-SB over time was estimated with linear mixed effects models.

RESULTS

282 participants were followed for an average of 2.9 years (SD 1.3 years). For 50% of individuals, loss of independence in IADLs occurred at CDR-SB>4.5 and in BADLs at CDR-SB>11.5. For individuals with a baseline CDR-SB=2, treatment with lecanemab would extend independence in IADLs for 10 months (95% CI 4-18 months) and treatment with donanemab in the low/medium tau group would extend independence in IADLs by 13 months (95% CI 6-24 months).

DISCUSSION

Independence in ADLs can be related to CDR-SB and used to demonstrate the effect of AD treatments in extending the time of independent function, a meaningful outcome for patients and their families.

Meaningful benefit of disease-modifying treatment: Evaluating changes in health-related resource use

INTRODUCTION

Are reductions in the rate of decline from the new disease-modifying treatments (DMTs) in early Alzheimer's disease (AD) meaningful? We examined whether such reductions may be reflected in changes in health-related resource use.

METHODS

Patients with Clinical Dementia Rating (CDR) = 0.5 or 1 with a clinical diagnosis of mild cognitive impairment or AD, reflecting clinical trial populations. Health-related resource use was reported using the Resource Use Inventory (RUI) including direct medical care, non-medical care, unpaid informal care, and time use.

RESULTS

Faster decline in CDR-Sum of Boxes (CDR-SB) from baseline was independently associated with higher likelihood and hours of informal care received, and lower likelihood of employment/volunteer work, but not with direct medical care.

DISCUSSION

Reductions in the rate of decline in CDR-SB seen from DMTs significantly affect patients' work capacity and need for informal care, indicators of economic impact meaningful to patients, families, and health systems. These measures are not readily captured in administrative data sets.

Highlights

Following a cohort of participants with MCI or mild dementia due to AD that mimics participants targeted for AD trials, this study showed slower decline in CDR-SB have significant effects on patients' work capacity and need for informal care, but not on their direct medical care utilization such as hospitalizations, ED use, and doctors' visits.Capturing potential benefits in health-related resource use may require direct measures of informal care and work/volunteer effort which are meaningful outcomes to patients, families and health systems.Caution is needed in our effort to assess benefits of recently developed disease modifying treatment in AD using electronic health records and administrative data from which utilization of direct medical care are routinely collected as these data sources may not capture the most apparent changes in resource utilization during early disease stages.

Donanemab in Japanese Patients with Early Alzheimer's Disease: Subpopulation Analysis of the TRAILBLAZER-ALZ 2 Randomized Trial

INTRODUCTION

Donanemab, a monoclonal antibody directed against an insoluble, modified, N-terminal truncated form of amyloid beta, demonstrated efficacy and safety in patients with early, symptomatic Alzheimer's disease (AD) in the phase 3 TRAILBLAZER-ALZ 2 trial. Here, we report clinical outcomes, biomarkers, and safety results for the Japanese subpopulation.

METHODS

TRAILBLAZER-ALZ 2 (N = 1736) was conducted in eight countries, including Japan (enrollment June 2020-November 2021; database lock April 2023). Participants (60-85 years) with early, symptomatic AD (mild cognitive impairment/mild dementia), Mini-Mental State Examination score 20-28, and confirmed amyloid and tau pathology were randomized 1:1 (stratified by tau status) to intravenous donanemab (700 mg for three doses, then 1400 mg/dose) or placebo every 4 weeks for 72 weeks. Primary outcome was change from baseline to week 76 in integrated Alzheimer's Disease Rating Scale (iADRS) score. Other outcomes included clinical measures of cognitive and functional impairment, biomarkers, and safety.

RESULTS

Of 88 Japanese participants (43 placebo, 45 donanemab), 7 in each group discontinued. Least-squares mean (LSM) change from baseline in iADRS score at week 76 was smaller with donanemab than with placebo in the combined (low-medium tau and high tau) and low-medium tau (N = 76) subpopulations (LSM change difference: 4.43 and 3.99, representing 38.8% and 40.2% slowing of disease progression, respectively). Slowing of AD progression with donanemab was also observed for other clinical outcomes. Marked decreases in amyloid plaque and plasma phosphorylated tau 217 were observed; amyloid clearance (< 24.1 Centiloids) was observed in 83.3% of the combined donanemab and 0% of the combined placebo groups. Amyloid-related imaging abnormalities of edema/effusions occurred in ten (22.2%) donanemab-treated participants (one [2.2%] symptomatic) and one (2.3%) placebo-treated participant.

CONCLUSIONS

The overall efficacy and safety of donanemab in Japanese participants were similar to the global TRAILBLAZER-ALZ 2 population.

TRIAL REGISTRATION

ClinicalTrials.gov identifier: NCT04437511.

How donanemab data address the coverage with evidence development questions

The Centers for Medicare & Medicaid Services (CMS) established a class-based National Coverage Determination (NCD) for monoclonal antibodies directed against amyloid for Alzheimer's disease (AD) with patient access through Coverage with Evidence Development (CED) based on three questions. This review, focused on donanemab, answers each of these CED questions with quality evidence. TRAILBLAZER-ALZ registration trials are presented with supporting literature and real-world data to answer CED questions for donanemab. TRAILBLAZER-ALZ registration trials demonstrated that donanemab significantly slowed cognitive and functional decline in amyloid-positive early symptomatic AD participants, and lowered their risk of disease progression while key safety risks occurred primarily within the first 6 months and then declined. Donanemab meaningfully improved health outcomes with a manageable safety profile in an early symptomatic AD population, representative of Medicare populations across diverse practice settings. The donanemab data provide the necessary level of evidence for CMS to open a reconsideration of their NCD. HIGHLIGHTS: Donanemab meaningfully improved outcomes in trial participants with early symptomatic Alzheimer's disease. Comorbidities in trial participants were consistent with the Medicare population. Co-medications in trial participants were consistent with the Medicare population. Risks associated with treatment tended to occur in the first 6 months. Risks of amyloid-related imaging abnormalities were managed with careful observation and magnetic resonance imaging monitoring.

The search for clarity regarding "clinically meaningful outcomes" in Alzheimer disease clinical trials: CLARITY-AD and Beyond

CLARITY-AD is an 18-month, double-blinded, placebo-controlled, phase 3 trial which examined the safety and efficacy of the anti-amyloid agent, lecanemab, in mild cognitive impairment and mild dementia due to Alzheimer disease (AD). Lecanemab effectively reduced mean brain amyloid burden and was associated with statistically significant favorable effects, reflected by moderately less decline in the primary and secondary clinical outcomes, at 18 months compared to placebo. However, there is controversy within the AD community regarding the clinical significance of these results and whether they translate into clinically meaningful and tangible benefits on cognition or daily functions.We here review the primary and secondary clinical outcomes of CLARITY-AD and present our interpretation of the potential clinical meaningfulness of the group-level differences in study outcomes in the context of the 18-month study duration. We propose that the validation of stage-appropriate group-level thresholds for clinical meaningfulness of AD trial outcomes in biologically confirmed cohorts will allow objective interpretation of trial results and guide clinical decision-making. Further, in accordance with FDA guidance which emphasizes patient-focused drug development, the contextualization of AD clinical trial outcomes can be facilitated by supplementary individual-level data analyses which measure the risk of disease progression or summarize intraindividual change, using prespecified thresholds of clinically meaningful change, in each of the study groups over the trial period. The concepts of "time-saved" and "time-based" slowing in disease progression can be used to communicate clinical outcomes associated with emerging disease-modifying AD therapies to various stakeholders. We also describe several factors that need to be considered when evaluating outcomes of emerging AD therapies, including disease stage, the neuropathologic complexity of AD, time-based effects of disease-modifying therapies, and the possible influence of individual factors on treatment response and/or risk for adverse events. The consideration of these factors in the design and reporting of future trials of emerging AD therapies will guide clinicians regarding their appropriateness for use in various patient populations.Finally, we emphasize that data from clinical cohorts with longer durations of treatment and follow-up, including extension studies and patient registries, is needed to evaluate the long-term safety and efficacy of lecanemab in early symptomatic AD.

A Comprehensive Review on Potential Molecular Drug Targets for the Management of Alzheimer's Disease

Alzheimer's disease (AD) is an onset and incurable neurodegenerative disorder that has been linked to various genetic, environmental, and lifestyle factors. Recent research has revealed several potential targets for drug development, such as the prevention of Aβ production and removal, prevention of tau hyperphosphorylation, and keeping neurons alive. Drugs that target numerous ADrelated variables have been developed, and early results are encouraging. This review provides a concise map of the different receptor signaling pathways associated with Alzheimer's Disease, as well as insight into drug design based on these pathways. It discusses the molecular mechanisms of AD pathogenesis, such as oxidative stress, aging, Aβ turnover, thiol groups, and mitochondrial activities, and their role in the disease. It also reviews the potential drug targets, in vivo active agents, and docking studies done in AD and provides prospects for future drug development. This review intends to provide more clarity on the molecular processes that occur in Alzheimer's patient's brains, which can be of use in diagnosing and preventing the condition.

Evaluation of Clinical Meaningfulness of Fortasyn Connect in Terms of "Time Saved"

Assessment of meaningfulness in randomized clinical trials (RCTs) in Alzheimer's disease (AD) is challenging, particularly in early disease. Converting clinical outcomes to disease progression time allows assessment of treatment effects using a metric that is understandable and meaningful: time. We demonstrate time savings assessments using meta time component tests (TCTs) in the LipiDiDiet multinutrient RCT. Dietary patterns are important for dementia prevention, likely due to individual cumulative nutrient effects. LipiDiDiet used a multinutrient (Fortasyn Connect) formulation in patients with prodromal AD, benefitting cognition (5-item composite NTB, effect 0.089), cognition and function (CDR-SB, -0.605), and slowing hippocampal atrophy (0.122 cm3). Meaningfulness of point differences is unclear. However, a combination TCT showed 9-month disease time savings at 24 months (38% slowing of disease time): 9.0, 10.5, and 7.2 months for NTB, CDR-SB, and hippocampal volume, underscoring the value of TCTs in AD RCTs and the need for continued validation of this approach.

APOE ε4's impact on response to amyloid therapies in early symptomatic Alzheimer's disease: Analyses from multiple clinical trials

INTRODUCTION

Apolipoprotein E (APOE) ε4 may interact with response to amyloid-targeting therapies.

METHODS

Aggregate data from trials enrolling participants with amyloid-positive, early symptomatic Alzheimer's disease (AD) were analyzed for disease progression.

RESULTS

Pooled analysis of potentially efficacious antibodies lecanemab, aducanumab, solanezumab, and donanemab shows slightly better efficacy in APOE ε4 carriers than in non-carriers. Carrier and non-carrier mean (95% confidence interval) differences from placebo using Clinical Dementia Rating Scale-Sum of Boxes (CDR-SB) were -0.30 (-0.478, -0.106) and -0.20 (-0.435, 0.042) and AD Assessment Scale-Cognitive subscale (ADAS-Cog) values were -1.01 (-1.577, -0.456) and -0.80 (-1.627, 0.018), respectively. Decline in the APOE ε4 non-carrier placebo group was equal to or greater than that in carriers across multiple scales. Probability of study success increases as the representation of the carrier population increases.

DISCUSSION

We hypothesize that APOE ε4 carriers have same or better response than non-carriers to amyloid-targeting therapies and similar or less disease progression with placebo in amyloid-positive trials.

HIGHLIGHTS

Amyloid-targeting therapies had slightly greater efficacy in apolipoprotein E (APOE) ε4 carriers. Clinical decline is the same/slightly faster in amyloid-positive APOE ε4 non-carriers. Prevalence of non-carriers in trial populations could impact outcomes.

Low circulating adropin levels in late-middle aged African Americans with poor cognitive performance

We recently reported accelerated cognitive decline in Europeans aged > 70 years with low circulating adropin levels. Adropin is a small, secreted peptide that is highly expressed in the human nervous system. Expression profiling indicate relationships between adropin expression in the human brain and pathways that affect dementia risk. Moreover, increased adropin expression or treatment using synthetic adropin improves cognition in mouse models of aging. Here we report that low circulating adropin concentrations associate with poor cognition (worst quintile for a composite score derived from the MMSE and semantic fluency test) in late-middle aged community-dwelling African Americans (OR = 0.775, P < 0.05; age range 45-65 y, n = 352). The binomial logistic regression controlled for sex, age, education, cardiometabolic disease risk indicators, and obesity. Previous studies using cultured cells from the brains of human donors suggest high expression in astrocytes. In snRNA-seq data from the middle temporal gyrus (MTG) of human donors, adropin expression is higher in astrocytes relative to other cell types. Adropin expression in all cell-types declines with advance age, but is not affected by dementia status. In cultured human astrocytes, adropin expression also declines with donor age. Additional analysis indicated positive correlations between adropin and transcriptomic signatures of energy metabolism and protein synthesis that are adversely affected by donor age. Adropin expression is also suppressed by pro-inflammatory factors. Collectively, these data indicate low circulating adropin levels are a potential early risk indicator of cognitive impairment. Declining adropin expression in the brain is a plausible link between aging, neuroinflammation, and risk of cognitive decline.

Clinical trials of new drugs for Alzheimer disease: a 2020-2023 update

Alzheimer's disease (AD) is the leading cause of dementia, presenting a significant unmet medical need worldwide. The pathogenesis of AD involves various pathophysiological events, including the accumulation of amyloid and tau, neuro-inflammation, and neuronal injury. Clinical trials focusing on new drugs for AD were documented in 2020, but subsequent developments have emerged since then. Notably, the US-FDA has approved Aducanumab and Lecanemab, both antibodies targeting amyloid, marking the end of a nearly two-decade period without new AD drugs. In this comprehensive report, we review all trials listed in clinicaltrials.gov, elucidating their underlying mechanisms and study designs. Ongoing clinical trials are investigating numerous promising new drugs for AD. The main trends in these trials involve pathophysiology-based, disease-modifying therapies and the recruitment of participants in earlier stages of the disease. These trends underscore the significance of conducting fundamental research on pathophysiology, prevention, and intervention prior to the occurrence of brain damage caused by AD.

Neurodevelopmental disorders and microcephaly: how apoptosis, the cell cycle, tau and amyloid-β precursor protein APPly

Recent studies promote new interest in the intersectionality between autism spectrum disorder (ASD) and Alzheimer's Disease. We have reported high levels of Amyloid-β Precursor Protein (APP) and secreted APP-alpha (sAPPa ) and low levels of amyloid-beta (Aβ) peptides 1-40 and 1-42 (Aβ40, Aβ42) in plasma and brain tissue from children with ASD. A higher incidence of microcephaly (head circumference less than the 3rd percentile) associates with ASD compared to head size in individuals with typical development. The role of Aβ peptides as contributors to acquired microcephaly in ASD is proposed. Aβ may lead to microcephaly via disruption of neurogenesis, elongation of the G1/S cell cycle, and arrested cell cycle promoting apoptosis. As the APP gene exists on Chromosome 21, excess Aβ peptides occur in Trisomy 21-T21 (Down's Syndrome). Microcephaly and some forms of ASD associate with T21, and therefore potential mechanisms underlying these associations will be examined in this review. Aβ peptides' role in other neurodevelopmental disorders that feature ASD and acquired microcephaly are reviewed, including dup 15q11.2-q13, Angelman and Rett syndrome.

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.

Challenges associated with using extracellular vesicles as biomarkers in neurodegenerative disease

INTRODUCTION

The hunt for new biomarkers - for the diagnosis of subcategories of disease, or for the monitoring of the efficacy of novel therapeutics - is an increasingly relevant challenge in the current era of precision medicine. In neurodegenerative research, the aim is to look for simple tools which can predict cognitive or motor decline early, and to determine whether these can also be used to test the efficacy of new interventions. Extracellular vesicles (EVs) are thought to play an important role in intercellular communication and have been shown to play a vital role in a number of diseases.

AREAS COVERED

The aim of this review is to examine what we know about EVs in neurodegeneration and to discuss their potential to be diagnostic and prognostic biomarkers in the future. It will cover the techniques used to isolate and study EVs and what is currently known about their presence in neurodegenerative diseases. In particular, we will discuss what is required for standardization in biomarker research, and the challenges associated with using EVs within this framework.

EXPERT OPINION

The technical challenges associated with isolating EVs consistently, combined with the complex techniques required for their efficient analysis, might preclude 'pure' EV populations from being used as effective biomarkers. Whilst biomarker discovery is important for more effective diagnosis, monitoring, prediction and prognosis in neurodegenerative disease, reproducibility and ease-of-use should be the priorities.