APOE ε4/ε4 homozygotes with early Alzheimer's disease show accelerated hippocampal atrophy and cortical thinning that correlates with cognitive decline.

Introduction: Hippocampal volume (HV) and cortical thickness are commonly used imaging biomarkers in Alzheimer's disease (AD) trials, and may have utility as selection criteria for enrichment strategies. Atrophy rates of these measures, in the high-risk apolipoprotein E (APOE) ε4/ε4 homozygous AD subjects are unknown.
Methods: Data from Alzheimer's Disease Neuroimaging Initiative (ADNI-1) and a tramiprosate trial were analyzed in APOE ε4/ε4 and APOE ε3/ε3 subjects with mild cognitive impairment (MCI) or mild AD. Magnetic resonance imaging (MRI) data were centrally processed using FreeSurfer; total HV and composite average cortical thickness were derived and adjusted for age, head size, and education. Volumetric changes from baseline were assessed using Boundary Shift Integral, and correlated with cognitive changes.
Results: APOE ε4/ε4 MCI subjects showed significantly higher % HV atrophy and cortical thinning at 12 months (4.4%, 3.1%, n = 29) compared to APOE ε3/ε3 subjects (2.8%, 1.8%, n = 93) and similarly in mild AD (7.4%, 4.7% n = 21 vs 5.4%, 3.3% n = 29). Differences were all significant at 24 months. Over 24 months, HV atrophy and cortical thinning correlated significantly with Alzheimer's Disease Assessment Scale-Cognitive subscale worsening in APOE ε4/ε4 MCI subjects, but not in mild AD.
Discussion: Correlation of volumetric measures to cognitive change in APOE ε4/ε4 subjects with early AD supports their role as efficacy biomarkers. If confirmed in a Phase 3 trial with ALZ-801 (pro-drug of tramiprosate) in APOE ε4/ε4 early AD subjects, it may allow their use as surrogate outcomes in future treatment or prevention trials in AD.
Competing Interests: Dr. Susan Abushakra serves as the chief medical officer of Alzheon, Inc. and holds stock and stock options of Alzheon, Inc. Dr. Martin Tolar serves as the founder, president, and chief executive officer of Alzheon, Inc. and holds stock and stock options of Alzheon, Inc. Dr. John A. Hey serves as the chief scientific officer of Alzheon, Inc. and holds stock and stock options of Alzheon, Inc. Dr. Aidan Power serves as a vice president at Alzheon, Inc. and holds stock and stock options of Alzheon, Inc. Dr. Anton Porsteinsson receives research support from the National Institutes of Health and U.S. Department of Defense. He also receives grants from AstraZeneca, Avanir, Biogen, Biohaven, Eisai, Eli Lilly, Genentech/Roche, Janssen, Novartis, Merck, and Toyama. He receives personal fees from Acadia Pharmaceuticals, Avanir, BioXcel, Eisai, Functional Neuromodulation, Grifols, Lundbeck, Merck, Neurim Pharmaceuticals, Pfizer, Tetra Discovery Partners, and Toyama. Dr. Marwan Sabbagh receives research support from the NIH and the Keep Memory Alive Foundation. He has consulting agreements with Allergan, Biogen, Bracket, Cortexyme, Grifols, Sanofi, Neurotrope, and Roche‐Genentech. He has ownership interest in Brain Health Inc., Versanum Inc., Neurotrope Inc., and uMethod Health. Drs. Joyce Suhy, Luc Bracoud, Joel Schaerer, and David Scott serve as full‐time employees of Bioclinica Inc. and have no competing interest in Alzheon Inc.
(© 2020 The Authors. Alzheimer's & Dementia: Translational Research & Clinical Interventions published by Wiley Periodicals, Inc. on behalf of Alzheimer's Association.)