The primary purpose of this study is to confirm the clinical efficacy and mechanism of action of GV-971, and identify incidence of known adverse reactions in long-term use and observe new adverse reactions, providing more guidance for clinical use.

Inclusion Criteria:

• Mild to moderate AD per NIA-AA.
• History of cognitive and functional decline over at least 1 year.
• MMSE scores between 11 and 24 (inclusive) at baseline.
• Hachinski Ischemic Score (HIS) scale total score ≤ 4.
• Hamilton Rating Scale for Depression/17 items (HAMD) total score ≤ 10.
• Brain MRI scan show the highest possibility of AD.
• Have a reliable study partner/caregiver.
• Sign the informed consent form.

Exclusion Criteria:

• Diagnosis of a dementia-related central nervous system disease other than AD.
• Major structural brain disease as judged by MRI.
• A resting heart rate of < 50 beats per minute (bpm) after 10 minutes of rest.
• Major medical illness or unstable medical condition within 12 months of screening.
• Concomitant use of donepezil, rivastigmine, galanthamine, huperzine A, memantine, or aducanumab within 6 moinths prior to baseline.
• Inadequate hepatic function.
• Inadequate organ function.
• ECG clinically significant abnormalities.