This is a Phase 1 study to examine the safety, tolerability and pharmacokinetics of TC-5619 in elderly subjects with and without Alzheimer's disease. Group 1 includes elderly subjects with Alzheimer's disease to receive TC-5619 or placebo for 28 days to evaluate safety and tolerability. Group 2 includes healthy elderly subjects in a dose escalation design to receive TC-5619 or placebo for 10 days to evaluate safety, tolerability and pharmacokinetics.

Inclusion Criteria (Groups 1 & 2):

• Normal body mass index (BMI)
• Non-smoking for a minimum of 3 months
• Subjects must be in reasonably good health, based on medical history, physical examination, vital signs, and ECG.

Group 1 Only:

• Subjects a Mini Mental State Examination score between 12-22, inclusive.
• Diagnosis of probable Alzheimer's Disease according to National Institute of Neurological and Communicative Disorders and Stroke-Alzheimer's Disease and Related Disorders Association (NINCDS-ADRDA) criteria
• Subjects must have a reliable caregiver.

Exclusion Criteria (Groups 1 & 2):

• Subjects with clinically significant heart disease, pulmonary disease, diabetes, neurologic or psychiatric disease (Group 1 subjects must have Alzheimer's Disease), or any other illness that could interfere with interpretation of study results.
• Subjects with a past or current history of seizures cannot participate.
• Current use of donepezil, rivastigmine or galantamine.