The present pharmacokinetic study is designed to assess the pharmacokinetics of RSG XR as monotherapy in patients with mild Alzheimer's disease (AD) as such information will not be obtained from the current phase III trials . The study aims to enroll fourteen patients (seven of each APOE genotype). Each patient will receive a single oral dose of 4mg of RSG XR in the morning under fasted conditions and PK samples will be taken up to 36h.