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Importance: Effects of antiamyloid agents, targeting either fibrillar or soluble monomeric amyloid peptides, on downstream biomarkers in cerebrospinal fluid (CSF) and plasma are largely unknown in dominantly inherited Alzheimer disease (DIAD)., Objective: To investigate longitudinal biomarker changes of synaptic dysfunction, neuroinflammation, and neurodegeneration in individuals with DIAD who are receiving antiamyloid treatment., Design, Setting, and Participants: From 2012 to 2019, the Dominantly Inherited Alzheimer Network Trial Unit (DIAN-TU-001) study, a double-blind, placebo-controlled, randomized clinical trial, investigated gantenerumab and solanezumab in DIAD. Carriers of gene variants were assigned 3:1 to either drug or placebo. The present analysis was conducted from April to June 2023. DIAN-TU-001 spans 25 study sites in 7 countries. Biofluids and neuroimaging from carriers of DIAD gene variants in the gantenerumab, solanezumab, and placebo groups were analyzed., Interventions: In 2016, initial dosing of gantenerumab, 225 mg (subcutaneously every 4 weeks) was increased every 8 weeks up to 1200 mg. In 2017, initial dosing of solanezumab, 400 mg (intravenously every 4 weeks) was increased up to 1600 mg every 4 weeks., Main Outcomes and Measures: Longitudinal changes in CSF levels of neurogranin, soluble triggering receptor expressed on myeloid cells 2 (sTREM2), chitinase 3-like 1 protein (YKL-40), glial fibrillary acidic protein (GFAP), neurofilament light protein (NfL), and plasma levels of GFAP and NfL., Results: Of 236 eligible participants screened, 43 were excluded. A total of 142 participants (mean [SD] age, 44 [10] years; 72 female [51%]) were included in the study (gantenerumab, 52 [37%]; solanezumab, 50 [35%]; placebo, 40 [28%]). Relative to placebo, gantenerumab significantly reduced CSF neurogranin level at year 4 (mean [SD] β = -242.43 [48.04] pg/mL; P < .001); reduced plasma GFAP level at year 1 (mean [SD] β = -0.02 [0.01] ng/mL; P = .02), year 2 (mean [SD] β = -0.03 [0.01] ng/mL; P = .002), and year 4 (mean [SD] β = -0.06 [0.02] ng/mL; P < .001); and increased CSF sTREM2 level at year 2 (mean [SD] β = 1.12 [0.43] ng/mL; P = .01) and year 4 (mean [SD] β = 1.06 [0.52] ng/mL; P = .04). Solanezumab significantly increased CSF NfL (log) at year 4 (mean [SD] β = 0.14 [0.06]; P = .02). Correlation analysis for rates of change found stronger correlations between CSF markers and fluid markers with Pittsburgh compound B positron emission tomography for solanezumab and placebo., Conclusions and Relevance: This randomized clinical trial supports the importance of fibrillar amyloid reduction in multiple AD-related processes of neuroinflammation and neurodegeneration in CSF and plasma in DIAD. Additional studies of antiaggregated amyloid therapies in sporadic AD and DIAD are needed to determine the utility of nonamyloid biomarkers in determining disease modification., Trial Registration: ClinicalTrials.gov Identifier: NCT04623242.

Importance: β-amyloid plaques and neurofibrillary tau deposits biologically define Alzheimer disease., Objective: To perform post hoc analyses of amyloid reduction after donanemab treatment and assess its association with tau pathology and clinical measures., Design, Setting, and Participants: The Study of LY3002813 in Participants With Early Symptomatic Alzheimer's Disease (TRAILBLAZER-ALZ) was a phase 2, placebo-controlled, randomized clinical trial conducted from December 18, 2017, to December 4, 2020, with a double-blind period of up to 76 weeks and a 48-week follow-up period. The study was conducted at 56 centers in the US and Canada. Enrolled were participants from 60 to 85 years of age with gradual and progressive change in memory function for 6 months or more, early symptomatic Alzheimer disease, elevated amyloid, and intermediate tau levels., Interventions: Donanemab (an antibody specific for the N-terminal pyroglutamate β-amyloid epitope) dosing was every 4 weeks: 700 mg for the first 3 doses, then 1400 mg for up to 72 weeks. Blinded dose-reduction evaluations occurred at 24 and 52 weeks based on amyloid clearance., Main Outcomes and Measures: Change in amyloid, tau, and clinical decline after donanemab treatment., Results: The primary study randomized 272 participants (mean [SD] age, 75.2 [5.5] years; 145 female participants [53.3%]). The trial excluded 1683 of 1955 individuals screened. The rate of donanemab-induced amyloid reduction at 24 weeks was moderately correlated with the amount of baseline amyloid (Spearman correlation coefficient r, -0.54; 95% CI, -0.66 to -0.39; P &lt; .001). Modeling provides a hypothesis that amyloid would not reaccumulate to the 24.1-centiloid threshold for 3.9 years (95% prediction interval, 1.9-8.3 years) after discontinuing donanemab treatment. Donanemab slowed tau accumulation in a region-dependent manner as measured using neocortical and regional standardized uptake value ratios with cerebellar gray reference region. A disease-progression model found a significant association between percentage amyloid reduction and change on the integrated Alzheimer Disease Rating Scale only in apolipoprotein E (APOE) ε4 carriers (95% CI, 24%-59%; P &lt; .001)., Conclusions and Relevance: Results of post hoc analyses for donanemab-treated participants suggest that baseline amyloid levels were directly associated with the magnitude of amyloid reduction and inversely associated with the probability of achieving complete amyloid clearance. The donanemab-induced slowing of tau was more pronounced in those with complete amyloid clearance and in brain regions identified later in the pathologic sequence. Data from other trials will be important to confirm aforementioned observations, particularly treatment response by APOE ε4 status., Trial Registration: ClinicalTrials.gov Identifier: NCT03367403.

Importance: Alzheimer disease (AD) is a neurodegenerative disorder characterized by cognitive deterioration and impaired activities of daily living. Current treatments provide only minor symptomatic improvements with limited benefit duration. Lanabecestat, a brain-permeable inhibitor of human beta-site amyloid precursor protein-cleaving enzyme 1 (BACE1/β-secretase), was developed to modify the clinical course of AD by slowing disease progression., Objective: To assess whether lanabecestat slows the progression of AD compared with placebo in patients with early AD (mild cognitive impairment) and mild AD dementia., Design, Setting, and Participants: AMARANTH (first patient visit on September 30, 2014; last patient visit on October 4, 2018) and DAYBREAK-ALZ (first patient visit on July 1, 2016; last patient visit on September 28, 2018) were randomized, placebo-controlled, phase 2/3 and phase 3 clinical trials lasting 104 weeks and 78 weeks, respectively. AMARANTH and DAYBREAK-ALZ were multicenter, global, double-blind studies conducted at 257 and 251 centers, respectively, located in 15 and 18 countries or territories, respectively. A population-based sample of men and women aged 55 to 85 years who met National Institute on Aging-Alzheimer's Association criteria for early AD or mild AD dementia was screened using cognitive assessments, and the presence of amyloid was confirmed. Patients were excluded for unstable medical conditions or medication use, significant cerebrovascular pathologic findings, or a history of vitiligo and/or current evidence of postinflammatory hypopigmentation. AMARANTH screened 6871 patients; 2218 (32.3%) were randomized, and 539 patients completed the study. DAYBREAK-ALZ screened 5706 patients; 1722 (30.2%) were randomized, and 76 patients completed the study., Interventions: Patients were randomized (1:1:1) to once-daily oral doses of lanabecestat (20 mg), lanabecestat (50 mg), or placebo., Main Outcomes and Measures: The primary outcome measure was change from baseline on the 13-item Alzheimer Disease Assessment Scale-cognitive subscale. Secondary outcomes included Alzheimer's Disease Cooperative Study-Instrumental Activities of Daily Living Inventory, Clinical Dementia Rating, Functional Activities Questionnaire, Mini-Mental State Examination, and Neuropsychiatric Inventory. Efficacy analyses were conducted on the intent-to-treat population., Results: Among 2218 AMARANTH patients, the mean (SD) age was 71.3 (7.1) years, and 1177 of 2218 (53.1%) were women. Among 1722 DAYBREAK-ALZ patients, the mean (SD) age was 72.3 (7.0) years, and 1023 of 1722 (59.4%) were women. Both studies were terminated early after futility analysis. There were no consistent, reproducible dose-related findings on primary or secondary efficacy measures. Psychiatric adverse events, weight loss, and hair color changes were reported in a higher percentage of patients receiving lanabecestat than placebo., Conclusions and Relevance: Treatment with lanabecestat was well tolerated and did not slow cognitive or functional decline., Trial Registration: ClinicalTrials.gov identifiers: NCT02245737 and NCT02783573.