To Evaluate the Efficacy and Safety/Tolerability Profiles of G-CSF in Subjects With Mild to Moderate Alzheimer's Disease

1. Subject with age of at lease 50 years old and no more than 85 years old

2. Subject diagnosed of Alzheimer's disease; based on the criteria of The Diagnostic and Statistical Manual of Mental Disorders (DSM)-Ⅳ for dementia and those of National Institute of Neurological and Communicative Disorders and Stroke - Alzheimer's Dementia and Related Disorder Association (NINCDS - ADRDA) and within 12-months CT/MRI brain scan supporting evidences.

3. Subject with Mini-Mental Examination (MMSE) scores of 12 to 26 (inclusive).

4. Subject with Clinical Dementia Rating (CDR) score of 1 (mild) or 2 moderate).

5. Subject with Modified Hachinski Ischemic score of 4.

6. Subject with a Hamilton Psychiatric Rating Scale for Depression score of 12.

7. Female subject with child-bearing potential agrees to take reliable contraceptive method during the participation of the study (Females with no child-bearing potential have to be surgically sterilized or at least 2 years after post-menopausal).

8. Subject and subject's legally acceptable representative have given written informed consent.

9. A reliable caregiver is sufficiently familiar with the subject (as determined by the investigator) and is willing to provide accurate data

1. Subject has underwent any of the following treatment modalities with the respective time frames:

1. Anti-epileptic agents: Within 12 weeks of the screening visit,

2. Narcotic: within 12 weeks of the screening visit,

3. Immunosuppressants: within 12 weeks of the screening visit,

4. Hypnotics: within 24 hours of the screening visit or the randomization visit,

5. Lithium: within 2 weeks of the randomization visit,

6. Succinylcholine-type muscle relaxants: within 2 weeks of the randomization visit,

7. Drugs or treatments known to cause major organ system toxicity: within 42 weeks of the randomization visit,

8. Tricyclic and tetracyclic anti-depressants: within 4 weeks of the screening visit,

9. Antiparkinsonian: Within12 weeks of the screening visit (Not including dopaminergic agent or peripheral anticholinergic agent at stable dose for at least 4 weeks of randomization visit),

10. Any medications for cognition enhancement: Within13 weeks of the screening visit(except for donepezil that has been maintained with a stable regimen for at least 12 weeks).

2. Subject is lactating, pregnant or plans to become pregnant,

3. Subject is cared primarily by nursing home,

4. Subject's AST or ALT is greater than 2 times of the upper limit or normal range.

5. Subject with diabetic history and with HbA1c > 8.5 %.

6. Subject with clinically significant medical or neurological disorders, other than AD, that may affect cognition (e.g., abnormal thyroid function tests, Vitamin B12 or folate deficiency, post-traumatic conditions Huntington's disease, Parkinson's disease, syphilis, probable/possible vascular dementia according to NINDS-AIREN criteria, active/uncontrolled seizure).

7. Subject with major psychiatric disorders.

8. Subject with spleen related disorders.

9. Subject with sickle cell disease.

10. Subject with myelodysplastic syndrome.

11. Subject with current diagnosis of acute stroke or history of acute stroke within 1 year.

12. Subject with allergy history to E. coli-derived proteins or G-CSF or donepezil.

13. Subject with cancer history and has received related therapy(ies) with in 2 years of entering this study.

14. Subject has participated other investigational study within 4 weeks of entering this study.