<br>        Inclusion Criteria:<br><br>          -  Diagnosis of all cause dementia and probable Alzheimer's disease<br><br>          -  Clinical Dementia Rating (CDR) total score of 1 (mild) to 2 (moderate) and MMSE score<br>             of 14-26 (inclusive)<br><br>          -  Age < 90 years<br><br>          -  Modified Hachinski ischemic score of = 4<br><br>          -  Females, if of child-bearing potential, must practice true abstinence or be competent<br>             to use adequate contraception and agree to maintain this throughout the study<br><br>          -  Subject, and/or, in the case of reduced decision-making capacity, legally acceptable<br>             representative(s) consistent with national law is/are able to read, understand, and<br>             provide written informed consent<br><br>          -  Has one (or more) identified adult caregiver who is willing to provide written<br>             informed consent for his/her own participation; is able to read, understand, and speak<br>             the designated language at the study site; either lives with the subject or sees the<br>             subject for =2 hours/day =3 days/week; agrees to accompany the subject to each study<br>             visit; and is able to verify daily compliance with study drug<br><br>          -  If currently taking an acetylcholinesterase inhibitor and/or memantine at the time of<br>             Screening, the subject must have been taking such medication(s) for =3 months. The<br>             dosage regimen must have remained stable for =6 weeks and it must be planned to remain<br>             stable throughout participation in the study.<br><br>          -  Able to comply with the study procedures<br><br>        Exclusion Criteria:<br><br>          -  Significant central nervous system (CNS) disorder other than Alzheimer's disease<br><br>          -  Significant focal or vascular intracranial pathology seen on brain MRI scan<br><br>          -  Clinical evidence or history of stroke, transient ischemic attack, significant head<br>             injury or other unexplained or recurrent loss of consciousness =15 minutes<br><br>          -  Epilepsy<br><br>          -  Major depressive disorder, schizophrenia, or other psychotic disorders, bipolar<br>             disorder, or substance (including alcohol) related disorders<br><br>          -  Metal implants in the head (except dental), pacemaker, cochlear implants, or any other<br>             non-removable items that are contraindications to MRI<br><br>          -  Resides in hospital or moderate to high dependency continuous care facility<br><br>          -  History of swallowing difficulties<br><br>          -  Pregnant or breastfeeding<br><br>          -  Glucose-6-phosphate dehydrogenase deficiency<br><br>          -  History of significant hematological abnormality or current acute or chronic<br>             clinically significant abnormality<br><br>          -  Abnormal serum chemistry laboratory value at Screening deemed to be clinically<br>             relevant by the investigator<br><br>          -  Clinically significant cardiovascular disease or abnormal assessments<br><br>          -  Preexisting or current signs or symptoms of respiratory failure<br><br>          -  Concurrent acute or chronic clinically significant immunologic, hepatic, or endocrine<br>             disease (not adequately treated) and/or other unstable or major disease other than<br>             Alzheimer's disease<br><br>          -  Diagnosis of cancer within the past 2 years prior to Baseline (other than basal cell<br>             or squamous cell skin cancer or Stage 1 prostate cancer) unless treatment has resulted<br>             in complete freedom from disease for at least 2 years<br><br>          -  Prior intolerance or hypersensitivity to methylthioninium-containing drug, similar<br>             organic dyes, or any of the excipients<br><br>          -  Treatment currently or within 3 months before Baseline with any of the following<br>             medications:<br><br>               -  Tacrine<br><br>               -  Clozapine, olanzapine (and there is no intent to initiate therapy during the<br>                  course of the study)<br><br>               -  Carbamazepine, primidone<br><br>               -  Drugs with a warning or precaution in the labeling about methemoglobinemia at<br>                  approved doses<br><br>          -  Current or prior participation in a clinical trial as follows:<br><br>               -  Clinical trial of a product for cognition within 3 months of Screening (unless<br>                  confirmed to have been randomized to placebo)<br><br>               -  A clinical trial of a drug, biologic, therapeutic device, or medical food in<br>                  which the last dose/administration was received within 28 days prior to Baseline<br>