The quality of study was seriously affected by the COVID-19, so it was decided to suspend the trial and restart it at the right time.

The purpose of this study is to evaluate the safety, tolerability and efficacy of GV-971 in mild to moderate Alzheimer's disease.

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.
• Brain MRI scan show the highest possibility of AD.
• Have a study partner/caregiver.

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 5 minutes of rest in sitting or supine position.
• Major medical illness or unstable medical condition within 6 months of screening.
• Concomitant use of AChEIs and/or memantine within 30 days before first MMSE score, and during the study.
• Inadequate hepatic function.
• Inadequate organ and marrow function.
• ECG clinically significant abnormalities.