Posiphen®, which was discovered by the US National Institute on Aging (NIA) is a selective inhibitor of amyloid precursor protein (APP) production and has potential utility as a disease modifying treatment for AD. The present study will confirm the pharmacokinetics (PK) of Posiphen and its metabolites in plasma and cerebral spinal fluid (CSF). It will also measure the effects of a 23-25 day treatment period with Posiphen on the CSF and plasma levels of a number of biomarkers, inflammatory factors and control proteins. It will also expand the safety data in humans by extending the treatment period from 10 days to a treatment period from 23-25 days. In addition, this study will measure concentrations of various soluble biomarkers in CSF and use the SILK™ assay methods to directly measure the effect of Posiphen on the fractional synthesis rate of Aβ40 in CSF, which will help guide the further development of Posiphen and determine the feasibility of SILK™ in a multicenter trial.