This 52-week, open-label extension study is to evaluate the long-term safety and tolerability of ACP-204 in subjects with ADP.

Inclusion Criteria:

• Subject has successfully completed ACP-204-006 study
• Male or female (age 55 to 95 years old): female must be of non-childbearing potential, male must take appropriate contraceptive method if partner has childbearing potential
• Subject has a designated study partner/caregiver
• Subjects are able to complete all study visits with a study partner/caregiver
• Signed inform consent form with a caregiver or legal representative

Exclusion Criteria:

• Requires treatment with a medication prohibited by the protocol
• Is in hospice and receiving end-of-life palliative care, or has become bedridden
• Unstable clinically significant medical condition other than AD
• Any medical condition that in the opinion of the investigator may affect safety or ability to complete the study

Additional inclusion/exclusion criteria apply. Subjects will be evaluated at screening to ensure that all criteria for study participation are met.