Donohue, Michael

Abstract INTRODUCTION The Consortium for Clarity in Alzheimer's disease related dementias (ADRD) Research Through Imaging (CLARiTI) is a study that aims to collect standardized imaging and plasma biomarkers on 2000 Clinical Core participants enrolled across all Alzheimer's Disease Research Centers (ADRC) sites. We sought to summarize the known heterogeneity across centers regarding scientific focus and initial enrollment plans for CLARiTI. METHODS We developed and distributed a survey capturing information on the 36 CLARiTI site's theme/expertise, recruitment plans, and the intersection of CLARiTI with other ADRC imaging efforts. RESULTS Anticipated CLARiTI enrollees spanned 11 different categories of suspected etiologies underlying impairment. A wide range of risk factors were endorsed across sites regarding the enrollment of unimpaired individuals. Variability also existed regarding site‐level strategies in enrollment into CLARiTI versus other imaging efforts. DISCUSSION We anticipate that the 2000 individuals that will enroll into CLARiTI will reflect the clinical heterogeneity already in place across the ADRC network. Highlights The ADRC Consortium for Clarity in ADRD Research Through Imaging (CLARiTI) will leverage and contribute to the existing Alzheimer's Disease Research Centers (ADRC) program by supporting standardized imaging and plasma collection across all centers. We summarize the variation in scientific focus and enrollment plans across ADRC sites participating in CLARiTI. The anticipated CLARiTI cohort will reflect the clinical heterogeneity that already exists across the ADRC network. CLARiTI will contribute to scientific goals related to the detection of multi‐etiological signatures relevant for Alzheimer's disease and related disorders (ADRDs).

Abstract INTRODUCTION Increased white matter hyperintensity (WMH) volume is a common but non‐specific finding in AD. This study investigates the effect of baseline WMH volume and APO E ε4 on magnetic resonance imaging (MRI)‐visible hemorrhagic lesion emergence. METHODS We included A4 participants with 0/1 hemorrhagic lesion at baseline and >1 post‐baseline MRI. We examined age, sex, amyloid, WMH, APOE ε4, and cardiovascular risk as predictors of whether people would accrue ≥2 hemorrhagic lesions by their last MRI. RESULTS Among 1097 individuals with 0/1 baseline lesion, 120 had at least two hemorrhagic lesions on their last MRI. Elevated baseline WMH (odds ratio [OR] = 2.3, p = 0.002) and APOE ɛ4/ɛ4 (OR = 4.8, p < 0.001) independently predicted membership to this group. Both hetero‐ and homozygous APOE ɛ4 carriers with low WMH volume had a low risk of accumulating hemorrhagic lesions. DISCUSSION These results support the independent consideration of WMH and APOE ɛ4 in the natural history of hemorrhagic lesion accumulation and suggest that individuals with low WMH volume have a low short‐term risk, irrespective of APOE genotype. Trial Registration : NCT02008357 Highlights Elevated baseline white matter lesion volume is related to the risk of ARIA‐H emergence. The effects of white matter lesion volume and APOE ɛ4 on ARIA‐H are independent. APOE ɛ4 carriers with low white matter lesion volume had a low risk of ARIA‐H emergence.

Importance Advances in Alzheimer disease (AD) have shifted research focus to earlier disease stages, necessitating more scalable approaches to identify cognitively unimpaired individuals with amyloid β (Aβ) pathology. Objective To assess the utility of plasma phosphorylated tau 217 (p-tau217) for classifying Aβ status in cognitively unimpaired individuals, both as a stand-alone test and in a 2-step approach where positive plasma results were confirmed using a second modality (Aβ positron emission tomography [PET] or cerebrospinal fluid [CSF]). Design, Setting, and Participants This cross-sectional cohort study used data collected between June 2009 and March 2024. We included 2916 cognitively unimpaired participants from 12 international independent observational cohorts in the US, Europe, Australia, and Canada with available plasma p-tau217 levels and CSF or PET Aβ biomarkers. Performance comparisons between mass spectrometry and immunoassay-based p-tau217 measurements were also performed (n = 964). Exposures Plasma p-tau217 levels measured by immunoassay. Main Outcome and Measures Aβ status, determined by CSF or Aβ PET biomarkers. Results Participants had a mean (SD) age of 66.9 (9.9) years; 971 (33.3%) were Aβ positive by either CSF or PET, 1667 (57.2%) were women, and 1108 (38.1%) carried at least 1 APOE ε4 allele. As a stand-alone test, plasma p-tau217 achieved a positive predictive value (PPV) of 79% (95% CI, 74-84) and an overall accuracy of 81% (95% CI, 80-82). In a 2-step workflow, the PPV and accuracy significantly increased to 91% (95% CI, 86-95). While this approach required screening of 677 individuals with plasma p-tau217 to identify 100 Aβ-positive individuals, compared to 536 participants when using PET alone, it reduced the need for PET testing to 124. Immunoassays demonstrated comparable PPVs to mass spectrometry (80% [95% CI, 74-86] vs 85% [95% CI, 81-90]; P = .12) but significantly lower overall accuracy (82% [95% CI, 79-84]% vs 88 [95% CI, 86-90]; P &amp;lt; .001) and true Aβ-positive detection rate (49% [95% CI, 43-55] vs 69% [95% CI, 64-75]; P &amp;lt; .001). Conclusions and Relevance The findings highlight the potential of plasma p-tau217 as a stand-alone test—or when used in a sequential 2-step approach alongside PET or CSF testing—as a cost-effective, scalable, and minimally burdensome strategy for identifying preclinical AD. Tailored screening workflows that incorporate p-tau217 can improve efficiency in participant selection for preclinical AD trials and, in the future, help guide access to disease-modifying treatments.

Importance Tau positron emission tomography (PET) allows in vivo detection of neurofibrillary tangles, a core neuropathologic feature of Alzheimer disease (AD). Objective To provide estimates of the frequency of tau PET positivity and its associated risk of clinical outcomes. Design, Setting, and Participants Longitudinal study using data pooled from 21 cohorts, comprising a convenience sample of 6514 participants from 13 countries, collected between January 2013 and June 2024. Cognitively unimpaired individuals and patients with a clinical diagnosis of mild cognitive impairment (MCI), AD dementia, or other neurodegenerative disorders were included. Exposures Tau PET with flortaucipir F 18, amyloid-β (Aβ) PET, and clinical examinations. Tau PET scans were visually rated as positive according to a US Food and Drug Administration– and European Medicines Agency–approved method, designed to indicate the presence of advanced neurofibrillary tangle pathology (Braak stages V-VI). Main Outcomes and Measures Frequency of tau PET positivity and absolute risk of clinical progression (eg, progression to MCI or dementia). Results Among the 6514 participants (mean age, 69.5 years; 50.5% female), median follow-up time ranged from 1.5 to 4.0 years. Of 3487 cognitively unimpaired participants, 349 (9.8%) were tau PET positive; the estimated frequency of tau PET positivity was less than 1% in those aged younger than 50 years, and increased from 3% (95% CI, 2%-4%) at 60 years to 19% (95% CI, 16%-24%) at 90 years. Tau PET positivity frequency estimates increased across MCI and AD dementia clinical diagnoses (43% [95% CI, 41%-46%] and 79% [95% CI, 77%-82%] at 75 years, respectively). Most tau PET–positive individuals (92%) were also Aβ PET positive. Cognitively unimpaired participants who were positive for both Aβ PET and tau PET had a higher absolute risk of progression to MCI or dementia over the following 5 years (57% [95% CI, 45%-71%]) compared with both Aβ PET–positive/tau PET–negative (17% [95% CI, 13%-22%]) and Aβ PET–negative/tau PET–negative (6% [95% CI, 5%-8%]) individuals. Among participants with MCI at the time of the tau PET scan, an Aβ PET–positive/tau PET–positive profile was associated with a 5-year absolute risk of progression to dementia of 70% (95% CI, 59%-81%). Conclusions and Relevance In a large convenience sample, a positive tau PET scan occurred at a nonnegligible rate among cognitively unimpaired individuals, and the combination of Aβ PET positivity and tau PET positivity was associated with a high risk of clinical progression in both preclinical and symptomatic stages of AD. These findings underscore the potential of tau PET as a biomarker for staging AD pathology.

AbstractINTRODUCTIONCerebral microhemorrhages (CMHs) are detectable by magnetic resonance imaging (MRI). CMHs in deep brain regions are linked to hypertensive vasculopathy, while those in lobar regions with amyloid beta (Aβ) deposition in blood vessels. This study aims to determine the association between anti‐thrombotic treatment and CMH prevalence among cognitively asymptomatic adults, and to assess the role of Aβ markers, apolipoprotein E (APOE) ε4 carrier status, and cardiovascular risk factors in CMH development.METHODSUsing baseline data from the Anti‐Amyloid Treatment in Asymptomatic Alzheimer's Disease (A4) and Longitudinal Evaluation of Amyloid Risk and Neurodegeneration (LEARN) studies, we examined CMH presence via 3T MRI, along with medication use, APOE ε4 carrier status, medical history, and blood pressure.RESULTSOur analysis showed a significantly higher prevalence of CMHs in the A4 cohort (17.3%) compared to the LEARN cohort (2.6%).DISCUSSIONFactors such as male sex, age, Aβ markers, and APOE ε4 status were significantly associated with higher CMH prevalence in the A4 cohort. However, anti‐thrombotic treatment did not show association with overall CMHs.Highlights Male sex, age > 75, amyloid beta (Aβ) burden, and apolipoprotein E (APOE) ε4 homozygosity are significantly associated with higher prevalence of CMHs (cerebral microhemorrhages) in a cohort of cognitively asymptomatic individuals. Male sex, age > 75, Aβ burden, and APOE ε4 homozygosity are significantly associated with higher prevalence of lobar CMHs in a cohort of cognitively asymptomatic individuals. Anti‐platelet or anti‐coagulant usage were not associated with an increased prevalence of CMHs in either brain location or overall, in a cohort of cognitively asymptomatic individuals. History of a lipid disorder is associated with a higher prevalence of lobar CMHs in a cohort of cognitively asymptomatic individuals.

AbstractBackgroundThe residual approach has found wide application in researching cognitive resilience, a phenomenon conceptually understood as cognitive performance being better‐than‐typical for an individual, despite apparent AD pathology. The standard residual approach extracts information about an individual’s resilience from the residuals of a linear model predicting cognition. This approach is subject to several limiting assumptions. Here, we explore the implications of these assumptions and propose an alternative predictive modeling approach which circumvents them.MethodsOur alternative approach relies on training a machine learning model on a sample of participants who follow a “typical” clinical progression (Fig. 1A). Residuals are then extracted for a heterogeneous dataset that potentially includes resilient participants by comparing observed cognitive outcomes to those predicted by the “typical” model (Fig. 1B). Additionally, our estimate can be refined by effectively estimating and removing model error from the extracted residual by leveraging a second predictive model (Fig. 1C). Using simulated data, we explore the assumptions made by the standard approach and the consequences of their violation. We then contrast this against our approach.ResultsOur simulations demonstrated that the standard residual approach only extracted accurate resilience estimates if the predictors used in the model explained cognition sufficiently well, while being unrelated to resilience itself. That is, as the predictors explain more of the resilience, the residuals became increasingly determined by model error (Fig. 2). We found that residuals achieved with our approach are more precise and provide individualized estimates that are unaffected by the aforementioned trade‐off (Fig. 3).ConclusionsOur approach holds several advantages over the standard approach: The definition of resilience can be freely adjusted and enforced via different definitions of “typical”, it allows for incorporating complex, non‐linear models without removing relevant information from the residual, the error component of the residual can be estimated through cross‐validation, and all predictors that potentially explain cognition can be included into the model without losing resilience information from the residual. Our approach can be used to measure any phenomenon that can be operationalized as a deviation from a typical outcome and, thus, is also applicable for researching resistance to pathology.

AbstractBackgroundAnti‐amyloid immunotherapies modestly slow disease progression in early symptomatic AD; addition of other therapeutic modalities may be necessary to achieve larger treatment effects. Therapies that directly target tau can potentially produce substantial clinical benefit because the accumulation of insoluble tau protein is strongly correlated with the progression of AD. Which tau therapies are likely to be efficacious, whether or not to combine them with anti‐amyloid therapies, and which individuals are most likely to benefit are important unresolved questions that would require multiple parallel design trials to answer. Platform (umbrella) trials test multiple therapies in the same trial, allowing for substantial savings in time, cost and participant burden.MethodATP is a new NIH‐funded Phase 2 clinical trial platform that will be conducted as part of the AD Clinical Trials Consortium (ACTC) in partnership with industry and philanthropic groups. The goal is to investigate the effects of tau therapies on the biological hallmarks of AD including insoluble and soluble tau species, amyloid and other biomarkers of neurodegeneration. ATP will initially evaluate two tau therapies alone or in combination with an anti‐amyloid therapy. 900 participants with late preclinical or early prodromal AD (CDR 0 or 0.5) will be randomized to six arms for two years of blinded treatment, followed by an optional open label extension (Figure 1). At least 20 percent of participants will be from underrepresented groups. The primary endpoint is 18F MK6240 tau PET, with key secondary endpoints including plasma P‐tau and MTBR243‐tau, amyloid PET and clinical assessments (CDR‐SB, PACC5). Inclusion criteria are based on plasma P‐tau217, clinical status and regional 18F MK6240 uptake.ResultTwo tau therapies and an anti‐amyloid therapy have been chosen for inclusion in ATP and startup is underway. The final design, choice of therapies and design as well as plans for inclusion of additional tau therapies after the trial begins and other details will be presented.ConclusionThe ATP is a six arm factorial design platform trial that is planned to begin in late 2024 or early 2025 that will support efficient development of tau and combination therapies for early, sporadic AD.

Abstract The Alzheimer's Disease Neuroimaging Initiative (ADNI) Clinical Core is responsible for coordination of all clinical activities at the ADNI sites, including project management, regulatory oversight, and site management and monitoring, as well as the collection of all clinical data and management of all study data. The Clinical Core is also charged with determining the clinical classifications and criteria for enrollment in evolving AD trials and enabling the ongoing characterization of the cross‐sectional features and longitudinal trajectories of the ADNI cohorts with application of these findings to optimal clinical trial designs. More than 2400 individuals have been enrolled in the cohorts since the inception of ADNI, facilitating refinement of our understanding of the AD trajectory and allowing academic and industry investigators to model therapeutic trials across the disease spectrum from the presymptomatic stage through dementia. Highlights Since 2004, the Alzheimer's Disease Neuroimaging Initiative (ADNI) Clinical Core has overseen the enrollment of > 2400 participants with mild cognitive impairment, mild Alzheimer's disease (AD) dementia, and normal cognition. The longitudinal dataset has elucidated the full cognitive and clinical trajectory of AD from its presymptomatic stage through the onset of dementia. The ADNI data have supported the design of most major trials in the field.

ImportanceBlack or African American (hereinafter, Black) and Hispanic or Latino/a/x (hereinafter, Latinx) adults are disproportionally affected by Alzheimer disease, but most research studies do not enroll adequate numbers of both of these populations. The Alzheimer’s Disease Neuroimaging Initiative-3 (ADNI3) launched a diversity taskforce to pilot a multipronged effort to increase the study inclusion of Black and Latinx older adults.ObjectiveTo describe and evaluate the culturally informed and community-engaged inclusion efforts to increase the screening and enrollment of Black and Latinx older adults in ADNI3.Design, Setting, and ParticipantsThis cross-sectional study used baseline data from a longitudinal, multisite, observational study conducted from January 15, 2021, to July 12, 2022, with no follow-up. The study was conducted at 13 ADNI3 sites in the US. Participants included individuals aged 55 to 90 years without cognitive impairment and those with mild cognitive impairment or Alzheimer disease.ExposuresEfforts included (1) launch of an external advisory board, (2) changes to the study protocol, (3) updates to the digital prescreener, (4) selection and deployment of 13 community-engaged research study sites, (5) development and deployment of local and centralized outreach efforts, and (6) development of a community-science partnership board.Main Outcomes and MeasuresScreening and enrollment numbers from centralized and local outreach efforts, digital advertisement metrics, and digital prescreener completion.ResultsA total of 91 participants enrolled in the trial via centralized and local outreach efforts, of which 22 (24.2%) identified as Latinx and 55 (60.4%) identified as Black (median [IQR] age, 65.6 [IQR, 61.5-72.5] years; 62 women [68.1%]). This represented a 267.6% increase in the monthly rate of enrollment (before: 1.11 per month; during: 4.08 per month) of underrepresented populations. For the centralized effort, social media advertisements were run between June 1, 2021, and July 31, 2022, which resulted in 2079 completed digital prescreeners, of which 1289 met criteria for subsequent site-level screening. Local efforts were run between June 1, 2021, to July 31, 2022. A total of 151 participants underwent site-level screening (100 from local efforts, 41 from centralized efforts, 10 from other sources).Conclusions and RelevanceIn this cross-sectional study of pilot inclusion efforts, a culturally informed, community-engaged approach increased the inclusion of Black and Latinx participants in an Alzheimer disease cohort study.

AbstractBackgroundEthnoculturally diverse individuals from underrepresented populations (URPs), including but not limited to Black/African American and Hispanic/Latinx adults, are disproportionally affected by Alzheimer’s disease (AD) compared to non‐Hispanic/Latinx white (NLW) adults. However, URPs have historically been under‐included in AD studies. The objective of this study is to describe efforts, and the results of those efforts, to increase enrollment and engagement of ethnoculturally diverse individuals from URPs in the Alzheimer’s Disease Neuroimaging Initiative 3 (ADNI3).MethodsEfforts undertaken by ADNI to increase enrollment and engagement of URPs included (1) launching of a Diversity Taskforce (DVTF) lead by two health disparities experts in July 2020, charged with overseeing ADNI’s mission in this space. Specific DVTF activities included: (2) the establishment, funding, and instrumental support (e.g., training, consultation, resources) of diversity at 13 ADNI3 sites; (3) changing ADNI protocol to facilitate research participation of URPs (e.g., optional lumbar puncture and sharing of amyloid PET results); (4) hiring a marketing agency to launch culturally‐informed digital/social media campaigns for the 13 DVTF Sites, with local websites; (5) development of a database to capture performance metrics of inclusion efforts at the 13 DVTF Sites; and (6) formation of a six‐member External Advisory Board, comprised of leaders in health disparities research, to guide DVTF efforts.ResultURP enrollment at these 13 DVTF sites improved from 1.1 URPs per month previously to >4 URPs per month, a 264% increase. Across all 59 ADNI sites, overall enrollment of ethnoculturally diverse individuals from URPs went from 89 (16.8%) to 126 (21.1%), representing a 25% increase in enrollment between May 2020 and September 2021. Moreover, since February 1st, 2021, ADNI enrolled 43 new participants of which 33 (77%) were from URPs.ConclusionIt is possible to improve the enrollment and retention of URPs in AD research using a multi‐pronged community engaged approach that also provides human capital, infrastructure, and financial resources. The success of the DVTF has led to the formation of a new Engagement Core in ADNI4, tasked with implementing a scaled‐up culturally‐informed, community‐engaged research approach to URP inclusion and retention across all 59 ADNI sites.