Participants no longer receiving intervention

Eligibility will be assessed during a screening period of up to 4 weeks. Subjects will take study medication once daily up to and including Day 28. Safety, tolerability and PK will be measured at each visit.

Inclusion Criteria:

• Adult males or postmenopausal or surgically sterile females age 55 - 85 years old.
• Healthy as determined by the Investigator, based on a medical evaluation including medical history, physical examination, neurological examination, laboratory tests and ECG recording

Exclusion Criteria:

• Any history of major psychiatric disorders, including substance use disorders, according to the Diagnostic and Statistical Manual of Mental Disorders, 5th Edition (DSM-5) criteria
• Alanine aminotransferase (ALT) or aspartate aminotransferase (AST) levels greater than 1.5 times the upper limit of normal (ULN)
• A clinically significant abnormality on physical examination, neurological examination, ECG, or laboratory evaluations
• A clinically significant vital signs abnormality, as judged by the principal investigator