Abstract
BACKGROUND: A subset of Alzheimer's disease patients progresses much more rapidly than average. These rapid progressors exhibit accelerated cognitive and functional decline. Potential differences in Alzheimer's biomarkers for rapid progressors and their responses to disease-modifying treatments remain poorly understood, with previous clinical trials and studies producing limited biomarker data and inconsistent results. OBJECTIVES: Examine differences in rapid progressor versus non-rapid progressor outcomes in two AD treatment trials (bapineuzumab and semagacestat) and investigate cognitive and biomarker progression in the placebo groups. DESIGN: Retrospective cohort study. SETTING: Four randomized, double-blind, phase 3 clinical trials from the Center for Global Clinical Research Data (Semagacestat) and the Yale University Open Data Access Project (Bapineuzumab). PARTICIPANTS: 4,902 patients (2,355 in bapineuzumab trials, 2,647 in semagacestat trials). Rapid progressors were operationally defined as the 10% of patients with the largest changes in cognitive scores from baseline to trial end. INTERVENTION: Bapineuzumab (monoclonal antibody) and Semagacestat (γ-secretase inhibitor). MEASUREMENTS: Cognitive assessments (CDR-SB, MMSE, ADAS-Cog, ADCS-ADL) and biological markers (CSF and plasma levels, MRI, FDG PET Scan, and Amyloid PET Scan) at baseline and endpoint. RESULTS: Rapid progressors showed distinct baseline characteristics in both the bapineuzumab and semagacestat trials: younger age (61.27 vs 63.14 years, p=0.008; and, 72.64 v. 73.64 years, p=0.046), a higher proportion of APOE4 carriers (87.6% vs 41.4%, p<0.001; and, 85.2% vs 49.3%, p = 0.022), and greater cognitive impairment across all measures (p<0.001). Both progression groups demonstrated improvement in specific biomarkers with treatment, though with different patterns. With bapineuzumab according to Conditional Average Treatment Effect analysis, rapid progressors showed biomarker improvement in amyloid CSF, p-Tau CSF, and amyloid PET scan, while non-rapid progressors demonstrated biomarker improvements in p-Tau CSF, amyloid PET, and MRI. With semagacestat, rapid progressors showed improvements in amyloid CSF and plasma while non-rapid progressors showed improvements in amyloid CSF, FDG PET, and MRI. CONCLUSIONS: This study provides crucial insights for clinical practice and trial design. The distinct response patterns between progression groups suggest that early identification and balancing of RPs between groups could improve clinical trial efficiency. The findings support the development of personalized treatment approaches for rapid progressors, who have aggressive disease progression. These results may significantly modify clinical trial design and patient care in Alzheimer's disease.