Evaluate the Efficacy and Safety of ID1201 for Dose-finding in Mild Alzheimer's Disease

Inclusion Criteria: 1. Patient diagnosed with dementia of Alzheimer's type according to DSM-IV criteria and probable Alzheimer's disease according to the NINCDS-ADRDA 2. modified Hachinski Ischemia Scale score of less than or equal to 4 3. Mini-Mental State Examination score 16 to 26 and Clinical Dementia Rating-Global Scale score 0.5 to 1 4. Amyloid postivie PET image (BAPL score 2 or 3) 5. Patients who have not received AChE inhibitors or NMDA antagonist at least for 3 months prior to the screening visit Exclusion Criteria: 1. Patients diagnosed or accompanied with Dementia due to other Neurodegenerative disorders other than Alzheimer's disease 2. Chronic alcohol and/or drug abuse within the past 5 years 3. Subjects who have medical history of significant renal disease (ccr\<30ml/min) or hepatic disease( 3\*ULN \<= ALT or AST) 4. Has received choline agonists, anticholinergics, anticonvulsants, antidepressants, antipsychotic drugs, Ginko biloba extract, Vitamin E, hormone replacement therapy etc. in the previous 4 weeks