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Introduction: Lanabecestat, a beta-site amyloid precursor protein-cleaving enzyme 1 (BACE1) inhibitor, was investigated as a potential Alzheimer's disease (AD)-modifying treatment. As previously reported, amyloid beta (Aβ) neuritic plaque burden reduction did not result in clinical benefit. Lanabecestat's effects on neuroimaging biomarkers and correlations between neuroimaging biomarkers and efficacy measures are reported., Methods: AMARANTH and DAYBREAK-ALZ were 104- and 78-week, multicenter, randomized, double-blind, placebo-controlled studies of lanabecestat in early symptomatic AD (AMARANTH) and mild AD dementia (DAYBREAK-ALZ). Patients randomly (1:1:1) received placebo, lanabecestat 20 mg, or lanabecestat 50 mg daily (AMARANTH, n = 2218; DAYBREAK-ALZ, n = 1722). Florbetapir positron emission tomography (PET), fluorodeoxyglucose (FDG) PET, flortaucipir PET, and volumetric magnetic resonance imaging (MRI) were used to measure Aβ neuritic plaque burden, cerebral metabolism, aggregated tau neurofibrillary tangles, and brain volume, respectively. Additionally, florbetapir perfusion scans were performed in DAYBREAK-ALZ. Efficacy measures included 13-item Alzheimer's Disease Assessment Scale-Cognitive Subscale, Alzheimer's Disease Cooperative Study Activities of Daily Living Inventory, Clinical Dementia Rating-Sum of Boxes, Functional Activities Questionnaire, and Mini-Mental State Examination. These studies stopped early due to futility., Results: Despite previously observed annualized reduction in Aβ neuritic plaque burden, there were no treatment differences in annualized change of aggregated tau neurofibrillary tangle burden (AMARANTH, n = 284; DAYBREAK-ALZ, n = 70), cerebral metabolism (AMARANTH, n = 260; DAYBREAK-ALZ, n = 38) and perfusion (DAYBREAK-ALZ, n = 213). Greater brain volume reduction (AMARANTH, n = 1697 [whole brain]; DAYBREAK-ALZ, n = 650 [whole brain]) occurred on lanabecestat compared to placebo. Higher baseline aggregated tau neurofibrillary tangle burden, lower cerebral metabolism, and lower brain volumes correlated with poorer baseline efficacy scores and greater clinical worsening. Lower baseline cerebral perfusion correlated with poorer baseline efficacy scores. Reduction in cerebral metabolism or whole brain volume correlated with clinical worsening, regardless of treatment assignment., Discussion: Tau pathology and cerebral metabolism assessments showed no evidence of lanabecestat slowing pathophysiologic progression of AD. Lanabecestat exposure was associated with brain volume reductions. Correlations between imaging measures and cognitive assessments may aid future study design., Competing Interests: Drs Zimmer, Shcherbinin, Devous, Selzler, Wessels, Downing, Fleisher, Otero Svaldi, and Sims; Ms Bragg; Messrs Landry and Andersen reported being full‐time employees and minor shareholders of Eli Lilly and Company. Drs Shering and Mullen reported being employees of AstraZeneca, which holds the intellectual property for lanabecestat, and being minor shareholders of AstraZeneca. Dr Mullen is a former AstraZeneca employee., (© 2021 The Authors. Alzheimer's & Dementia: Translational Research & Clinical Interventions published by Wiley Periodicals LLC on behalf of Alzheimer's Association.)

Introduction: Solanezumab is an anti-amyloid monoclonal antibody in clinical testing for treatment of Alzheimer's disease (AD). Its mechanism suggests the possibility of slowing the progression of AD., Methods: A possible disease-modifying effect of solanezumab was assessed using a new statistical method including noninferiority testing. Performance differences were compared during the placebo-controlled period with performance differences after the placebo patients crossed over to solanezumab in the delayed-start period., Results: Noninferiority of the 14-item Alzheimer's Disease Assessment Scale-Cognitive subscale (ADAS-Cog 14 ) and Alzheimer's Disease Cooperative Study Activities of Daily Living inventory instrumental items (ADCS-iADL) differences was met through 132 weeks, indicating that treatment differences observed in the placebo-controlled period remained, within a predefined margin, after the placebo group initiated solanezumab. Solanezumab was well tolerated, and no new safety concerns were identified., Discussion: The results of this secondary analysis show that the mild subgroup of solanezumab-treated patients who initiated treatment early, at the start of the placebo-controlled period, retained an advantage at most time points in the delayed-start period.