APOE genotype: no influence on galantamine treatment efficacy nor on rate of decline in Alzheimer's disease

Abstract

Apolipoprotein E (APOE) has been extensively demonstrated to be a genetic risk factor for Alzheimer's disease (AD). Associations of APOE genotype have been reported with age at AD onset, rate of decline, and responsiveness to therapy. This study aimed to test these hypotheses in a large study population of AD patients. APOE genotype was determined from 1,528 Caucasian subjects, diagnosed by NINCDS/ADRDA criteria as probable AD patients, enrolled in four international placebo-controlled clinical trials of 3--12 months duration, designed to evaluate efficacy of treatment with galantamine or sabeluzole. In addition to patient demographics and baseline scores for Mini Mental State Examination, scores on the Disability Assessment for Dementia (DAD) and the cognitive subscale of the Alzheimer's Disease Assessment Scale (ADAS-cog) were recorded at the start, during, and at the end of the study. APOE epsilon 4 homozygotes had a significantly lower age at disease onset compared to patients with other APOE genotypes. The epsilon 4 allele was significantly over-represented in females compared to males, and in the group of subjects with an AD family history. Based on longitudinal data of 504 placebo-treated AD patients, the linear annual rate of change in score was 5 points on the ADAS-cog scale and 11 on the DAD scale. The epsilon 4 allele copy number did not influence these rates of decline. Sabeluzole treatment was not effective in the overall group compared to the placebo-treated group, nor in any subgroup stratified by epsilon 4 allele count. Galantamine produced cognitive and functional improvement that were not affected by epsilon 4 allele count. In conclusion, our data confirm a strong association between epsilon 4 homozygotes and age at onset of AD but do not support an effect of epsilon 4 allele copy number on rate of cognitive and functional decline nor on the efficacy of galantamine in patients with AD.