This is a randomized, double-blind, placebo-controlled, parallel-group comparison study in subjects with Alzheimer's Disease. Following first screening period, subjects will be randomly assigned into one of the following arms: AstroStem and placebo control in a 1:1 ratio. AstroStem or placebo control will be administered via I.V. at Week 0. This procedure will be repeated 9 times at 2-week interval. Subjects will be scheduled for two follow-up visits at Weeks 30 and 52 to evaluate primary and secondary outcome endpoints.