Brief summary: This is a phase II study to investigate the safety, preliminary efficacy and pharmacokinetics of AD-35 tablet in patients with mild to moderate Alzheimer's Disease. This study is to be run in China involving 21 sites. It will enroll approximately 480 patients to ensure 240 randomized with mild to moderate Alzheimer's Disease. The treatment period is 52 weeks and total study duration per patient is approximately 57 weeks.

In this multicenter, randomized, double blind, parallel-group, placebo controlled phase II study, 240 patients with mild to moderate Alzheimer's Disease are planned to be enrolled and randomly assigned 1:1:1 to receive placebo, or different doses of AD-35 tablet (30 or 60 mg). After the first 26 weeks, subjects on active study drug will remain on the current doses, and subjects assigned to placebo will be randomized to receive 30 mg and 60 mg AD-35 tablet in a 1:1 ratio, respectively, for the second 26 weeks. This study will evaluate the safety, preliminary efficacy and pharmacokinetics of AD-35 tablets in patients with mild to moderate Alzheimer's Disease.

Inclusion Criteria:

• Men and women, 50-75 years of age.
• Formal education of five or more years.
• Diagnosed of probable AD in accordance with the NINCDS/ADRDA criteria (2011).
• Mild or moderate AD subjects: MMSE Score of 15-26 and CDR Score ≥ 0.5 (CDR memory score ≥ 0.5).
• Subjects must have a brain magnetic resonance imaging (MRI) scan that is consistent with a clinical diagnosis of probable AD. Brain atrophy and medial temporal lobe atrophy visual assessment scale MTA grading >2 points. Mild white matter degeneration may occur, but Fazekas less than or equal to 2 points and supratentorial lacunar infarction lesions less than or equal to 3 points.
• The total score of modified Hachinski ischemia scale (MHIS) ≤ 4.
• Hamilton depression scale (HAMD) has a total score ≤ 17.

Exclusion Criteria:

• Visual, hearing and verbal communication of subjects cannot meet the needs of cognitive function evaluation.
• Inability to tolerate MRI procedures or contraindication to MRI, (such as implanted in the body, MRI incompatible pacemakers, implantable cardioverter defibrillators, cochlear implants, aneurysm clips, implanted injection pump, implanted nerve stimulator, metallic splinters in the eye, other magnetic, electrical and other metal implants) [note], or any other situation, in the judgment of the Investigator, is not suitable for magnetic resonance imaging (MRI).
• The investigators believe that other severe or unstable conditions may interfere with the cognitive evaluation in clinical trials.
• Dementia caused by other reasons: vascular dementia, central nervous system infection, endocrine system diseases (such as thyroid disease, parathyroid gland disease) and other reasons.

Double (Participant, Investigator)