Efficacy, Safety, & Tolerability of AZD3480 Patients With Mild to Moderate Dementia of the Alzheimer's Type (AD)

Inclusion Criteria: 1. A clinical diagnosis of AD per NINCDS-ADRDA criteria; mild to moderate severity as defined by Mini-Mental State Examination (MMSE) scores of 12 to 22. 2. AD diagnosed at least 12 months prior to Screening, and supported by brain imaging studies within 6 months prior to Screening. 3. Absence of vascular dementia both per AIRENS criteria and as defined by modified Hachinski ischemia score (HIS) of \</= 4. 4. Presence of a caregiver with significant proportion of time in contact with subject and who will oversee administration of study drug during the trial 5. Able to complete test assessments and to sign informed consent with the help of a caregiver if needed Exclusion Criteria: 1. Diagnosis or presence of other dementing illnesses 2. Use of mood stabilizers, antidepressants, anxiolytics, antipsychotics or hypnotics 3. Treatment within 1 month prior to Screening using cognition-affecting agents (e.g. CNS stimulants) 4. Tobacco user within 4 months prior to Screening 5. Use of smoking cessation therapy within 4 months prior to Screening 6. History within past 6 months of alcohol abuse or illicit drug abuse 7. Unable, even with caregiver assistance, to comply with study procedures in opinion of investigator 8. Myocardial infarction within the 12 months prior to Screening 9. Hypothyroidism, vitamin B12 or folic acid deficiency 10. Known systemic infection (HBV, HCV, HIV, TB) 11. Vascular dementia per NINDS-AIRENS criteria and as defined by a modified Hachinski ischemia score (HIS, Appendix 4) score of \> 4 (i.e., vascular dementia is consistent with a modified HIS \> 4).