Multiple Dose Study Evaluating the Safety and Tolerability of NSA-789

Inclusion Criteria * Men or women aged 18 - 50 years (healthy subjects) or greater than 55 years old (subjects with Alzheimer's Disease) * Women must be surgically sterile or postmenopausal * Subjects with Alzheimer's Disease must be generally healthy, but may have a stable, chronic illness if well controlled. Exclusion Criteria * Healthy subjects may not be on any prescription or investigation drugs within 30 days of start of study. * Subjects with Alzheimer's Disease may not be on any cholinesterase inhibitors such as donepezil (Aricept®) or rivastigmine (Exelon®) within 4 weeks of the start of the study.