Efficacy and Safety of 26-Week Treatment of AR1001 in Patients With Mild to Moderate Alzheimer's Disease

Inclusion Criteria 1. Male or female subjects aged 55-80 years at the time of signing the Informed Consent Form. 2. Subjects (or subject's legally acceptable representative) and caregiver(s) who can sign an Informed Consent to participate in the study. Same caregiver(s) must assist the subject throughout the entire duration of the study. 3. Subjects who have a diagnosis of probable Alzheimer's disease according to the NIA-AA (National Institute of Aging and Alzheimer's Associations, 2011) criteria with mild to moderate dementia (stage 4 - 5) at screening. 4. Subjects who have mild-to-moderate cognitive impairment with MMSE Score of 16-26 at screening. 5. Subjects who have an MRI (either 1.5T or 3T) or CT scan performed after onset of symptoms and prior to randomization with findings consistent with the diagnosis of dementia due to Alzheimer's disease and without any other clinically significant comorbid pathologies. 6. Subjects who have one (or more) identified adult study partner(s) who, in the opinion of the investigator, has sufficient contact with and knowledge about the subject as to be able to report knowledgeably about the subject's safety, compliance and adherence, cognition, function, and behavior. Exclusion Criteria 1. Subjects who are female who are pregnant, nursing, or of childbearing potential and not practicing effective contraception. 2. Subjects who have signs of delirium. 3. Subjects who have had a cortical stroke within the preceding 2 years. 4. Subjects who have any diagnosis of dementia other than that related to Alzheimer's Disease, including concomitant vascular dementia. 5. Subjects who have a PET scan performed after onset of symptoms with negative amyloid results. 6. Subjects with a history of myocardial infarction, unstable angina, New York Heart Association (NYHA) class III or IV heart failure or stroke within the last 12 months. 7. Subjects with uncontrolled hypertension (systolic blood pressure \>160mm Hg or diastolic blood pressure \> 95mm Hg) or hypotension (systolic blood pressure \<90mm Hg or diastolic blood pressure \<50mm Hg). 8. Subjects who have clinically significant renal impairment (creatinine \> 1.5x ULN) or hepatic impairment (AST or ALT \> 2.5x ULN or total bilirubin \> 1.5x ULN). 9. Subjects who have history of cancer or malignant tumor within 5 years prior to screening with the exception of: 1. Basal or squamous cell carcinoma of the skin or cervical dysplasia which has been adequately treated. 2. In situ Grade 1 cervical cancer, fully treated at least 2 years prior to screening and without recurrence. 3. Prostate cancer, confined to the prostate gland, which has been adequately treated (surgery and/or radiation) with normal or low and stable PSA levels for 2 years prior to screening. 10. Subjects who have history of untreated thyroid disorder or a seizure disorder. 11. Subjects who are being treated, or likely to require treatment during the study, with any medications prohibited by the study protocol. 12. Subjects who have participated in any investigational drug or device trial within the previous 30 days or five half-lives of the investigational drug at screening, whichever one is longer. 13. Subjects who have any other clinically significant abnormal result in laboratory tests such as abnormally low B12 or high TSH levels, as determined by the Investigator. 14. Subjects with any current psychiatric diagnosis other than AD if, in the judgment of the investigator, the psychiatric disorder or symptom is likely to confound interpretation of drug effect, affect cognitive assessments, or affect the subject's ability to complete the study. 15. Subjects whose treatment with FDA-approved AD medication (donepezil, galantamine, memantine, rivastigmine or their combinations) has not been stable for at least 3 months prior to screening. Treatment and dosing should remain stable, with no changes throughout the trial. 16. Subjects who are currently receiving (or unable to stop use for at least 21 days \[3 weeks\] prior to receiving the first dose of the AR1001 and throughout the study) prescription or non-prescription medications or other products known to be moderate or potent inhibitors/inducers of CYP3A4. 17. Subjects who have had any intake of grapefruit, grapefruit juice, Seville oranges, Seville orange marmalade, or other products containing grapefruit or Seville oranges within 7 days of the first administration of the AR1001 and throughout the study. 18. Subjects, in the opinion of the Investigator, who are unsuitable to participate in the study. Extension Phase Continuation Criterion 1\. Subjects enrolled in AR1001-ADP2-US01 and completed 26 weeks of assigned dosing.