A Study to Evaluate the Efficacy and Safety of Brain Polypeptide Solution in Mild Alzheimer's Disease

Inclusion Criteria: 1. Age range from 50 to 85 (including 50 and 85 years old), regardless of ethnic group or gender; 2. The subjects should be able to complete the cognitive ability measurement and other tests specified in the protocol; 3. meeting the criteria for likely Alzheimer's Disease （AD） dementia (2007) by National Institute of Neurological Disorders and Strokes - Alzheimer's Disease and Related Diseases Association（NINCDS-ADRDA）; 4. patients with mild dementia: the total score of Mini-Mental State Examination (MMSE) : illiteracy ≤17 points, primary school ≤20 points, secondary school ≤22 points, university ≤23 points; Clinical Dementia Rating scale （CDR） = 1 point; 5. the total score of the Hachinski Ischemic Score （HIS ）was \< 4. 6. Hamilton depression scale (17 items) total score ≤7 points; 7. Brain MRI shows a high likelihood of AD; 8. before enrollment, patients should take a stable dose of dementia drugs (such as donepezil 10mg) ≥8 weeks; 9. the expected survival time is \> 1 year; 10. subjects should have a stable and reliable caregiver, or at least have frequent contact with the caregiver (at least 3 days per week and at least 2 hours per day), who will help patients participate in the whole study; Caregivers must accompany the subjects to the visit and assist in completing the relevant scale. Exclusion Criteria: 1. refuse to sign the inform consent form; 2. other causes of dementia: known vascular, central nervous system infection ,Parkinson's disease, traumatic brain dementia, other physical and chemical factors; serious body disease , intracranial space-occupying lesions, endocrine system disease, such as thyroid disease, and a lack of vitamin B12, folic acid, or any other known causes of dementia. 3. central nervous system diseases (including stroke, optic neuromyelitis, Parkinson's disease, epilepsy, etc.); 4. obvious positive signs of nervous system examination; 5. psychotic patients, including schizophrenia or other disorders with bipolar disorder, major depression or delirium; 6. uncontrolled hypertension or hypotension during screening: systolic blood pressure ≥180（millimetres of mercury ）mmHg or \< 90mmhg, or diastolic blood pressure ≥120mmHg or \< 60mmhg; 7. unstable or severe diseases of the heart, lung, liver, kidney and hematopoietic system according to the judgment of the researchers; 8. patients with incurable visual and auditory disorders that cannot complete neuropsychological tests and scales; 9. female subjects who are positive in pregnancy test or breast-feeding and who cannot take effective contraceptive measures or have a birth plan; 10. severe allergy, non-allergic drug reaction or multi-drug allergy history; 11. participated in other clinical trials within 3 months before screening visit; 12. taking any health care products related to brain and brain improvement currently and failing to keep the promise to stop using the above products; 13. other conditions are unsuitable for participating in this study according to the judgement of researchers.