Abstract
Background: In patients with Alzheimer's disease (AD) either with or without stable cholinesterase inhibitor (ChEI) treatment, clinical trials have shown significant and beneficial Baseline-to-Endpoint effects following memantine (MEM) treatment in comparison with placebo. Time to meaningful levels of change on outcome measures can also provide clinically relevant information for physicians. This new post hoc analysis used a time-to-event Kaplan-Meier methodology to evaluate clinically meaningful changes in four 6-7 month studies of memantine alone or in combination with a ChEI. Methods: The populations of 4 trials were pooled (N=1,628): 3 randomized, double-blind, placebo-controlled trials of MEM IR (10 mg BID; 2 monotherapy; 1 of patients on stable donepezil) and 1 trial of MEM ER (28 mg QD; patients on stable ChEI regimen) in moderate to severe AD. Efficacy outcomes included cognition (SIB), function (ADCS-ADL19), behavior (NPI), and global status (CIBIC-Plus), and clinically meaningful events were defined as the median decline at Endpoint for placebo-only treated patients; the K-M method was used to compare median time to reach this point in the treatment groups and an unadjusted log-rank test was performed on the intent-to-treat population. Results: Meaningful events were defined as declines of ≥4 points on SIB, ≥3 points on ADCS-ADL19, NPI total score increase ≥0, and final score ≥5 for CIBIC-Plus. The median times-to-events (days) were: SIB (PBO-only: 85; PBO+ChEI: 176 [P<0.0001 vs PBO-only]; MEM-only: 188 [P=0.0001 vs PBO-only]; MEM+ChEI: >196 [P<0.0001 vs PBO-only]; all-PBO groups: 168; all-MEM groups: 193 [P=0.0037 vs all-PBO]), ADCS-ADL19 (PBO-only: 125; PBO+ChEI: 127 [P=0.9854 vs PBO-only]; MEM-only: 172 [P=0.0445 vs PBO-only]; MEM+ChEI: 168 [P=0.2390 vs PBO-only]; all-PBO: 127; all-MEM: 168 [P=0.0127 vs all-PBO]), NPI (PBO-only: 85; PBO+ChEI: 84 [P<0.0001 vs PBO-only]; MEM-only: 101 [P=0.3518 vs PBO-only]; MEM+ChEI: 87 [P=0.0333 vs PBO-only]; all-PBO: 85; all-MEM: 88 [P=0.0027 vs all-PBO]), and CIBIC-Plus (PBO-only: 126; PBO+ChEI: 126 [P=0.4567 vs PBO-only]; MEM-only: 168 [P=0.1429 vs PBO-only]; MEM+ChEI: 168 [P=0.4011 vs PBO-only]; all-PBO: 126; all-MEM: 168 [P=0.0205 vs all-PBO]). Conclusions: Time-to-event analyses support the conclusion that memantine alone or in combination with a ChEI is efficacious in delaying cognitive, functional, and behavioral declines in patients with moderate to severe AD.