A Phase II clinical trial to assess the safety and tolerability of PBT2 and its effect on amyloid levels in the brains of patients with prodromal or mild Alzheimer's disease.

INTERVENTION: PBT2 is supplied as 250mg immediate‐release capsules. The dose for this study is 250mg / day ie. one capsule is to be taken orally, once a day for 52 weeks duration. CONDITION: Prodromal Alzheimer's disease or mild Alzheimer's disease PRIMARY OUTCOME: To evaluate the effect of PBT2 compared to placebo on brain amyloid levels after 52 weeks of treatment as measured by Carbon 11‐Pittsburgh Imaging Compound‐B (PiB) Positron Emission Tomography (PET) imaging. SECONDARY OUTCOME: To evaluate the effect of PBT2 compared to placebo on brain metabolic activity after 52 weeks as measured by Fluorine 18 labelled Fluorodeoxyglucose (FDG) PET imaging. To evaluate the effect of PBT2 compared to placebo on brain volumes after 52 weeks as assessed by Magnetic Resonance Imaging (MRI) to measure the cortical grey matter volume, hippocampal volume and ventricular volume. To evaluate the effect of PBT2 compared to placebo on cognition after 52 weeks as measured by a Neuropsychological Test Battery (NTB) questionnaires and the Mini‐mental State Examination (MMSE) questionnaire. To evaluate the effect of PBT2 compared to placebo on functional ability after 52 weeks as measured by the Alzheimer's disease Cooperative Study‐Activities of Daily Living‐23 (ADCS‐ADL‐23) questionnaire To evaluate the safety and tolerability of PBT2 compared to placebo as measured by capture of vital signs, physical examination, neurological examination, ECG, eye examination, blood haematology and biochemistry, urinalysis and recording of adverse events. ; From previous clinical trials, the most commonly reported side effects that were possibly related to PBT2 were fatigue (tiredness), headache, dizziness, nasopharyngitis (swollen blocked nose), and somnolence (drowsiness). Less common side‐effects possibly related to PBT2 were diarrhoea, back pain, nausea and pharyngolaryngeal (throat) pain. It is possible that a rare side effect may be dissociation (a feeling of disconnecting from one's thoughts, feelings, memories or self). INCLUSION CRITERIA: 1. Prodromal Alzheimer's disease or mild Alzheimer's disease 2. 11C‐PiB‐PET positive (SUVR>1.7) 3. MMSE >or= 20