This is a multi-centre study to be conducted in Sweden and Finland. Up to 24 male and/or female patients of non-childbearing potential aged 45 to 75 years (inclusive), with a clinical diagnosis Parkinson's Disease will be randomised in the study to allow for 20 patients to complete this study.The study will evaluate the effect of 8 weeks treatment with AZD3241 on microglia activation as measured via PET examinations.

A Phase IIA, Multi centre, Double-blind, Randomised, Placebo-controlled, Parallel-group Study to Assess the Effect of 8 Weeks Treatment with Oral AZD3241 on Microglia Activation, as Measured by Positron Emission Tomography (PET), in Patients with Parkinson's Disease

Inclusion Criteria:

• Female and male patients aged 45 to 75 years (inclusive) at the day of enrolment (Visit 1)
• Female patients must have a negative pregnancy test at Screening, must not be lactating and must be of non childbearing potential, confirmed at Screening
• Male patients should be willing to use barrier contraception, eg, condoms, even if their partners are post-menopausal, be surgically sterile or are using accepted contraceptive methods, from the administration of the first dose of the investigational
• The clinical diagnosis of patients must meet the criteria for "diagnosis of idiopathic Parkinson's disease" according to the modified UKPDS Brain Bank criteria (see Appendix E)
• Modified Hoehn and Yahr stage 1 to 2

Exclusion Criteria:

• Diagnosis is unclear or a suspicion of other Parkinsonian syndromes exists, such as secondary Parkinsonism (caused by drugs, toxins, infectious agents, vascular disease, trauma, brain neoplasm), Parkinson-plus syndromes or heredodegenerative diseases
• Patients who have undergone surgery for the treatment of Parkinson's disease (eg, pallidotomy, deep brain stimulation, foetal tissue transplantation) or have undergone any other brain surgery
• Presence of significant dyskinesias, motor fluctuations, swallowing difficulties or loss of postural reflexes Patients with a history of non-response (according to both the clinician and the patient) to an adequate course of L-dopa or a DA agonist
• Use of pergolide, selegiline, metoclopramide, strong CYP3A4 inhibitors, CYP3A4 inducers (including St John's Wort) and strong CYP1A2 inhibitors and inducers, within 1 month of randomisation;