Exenatide Once-weekly as a Treatment for Multiple System Atrophy

Inclusion Criteria: * Participants aged 30-80 years old with a diagnosis of Possible or Probable MSA of the parkinsonian subtype (MSA-P) or cerebellar subtype (MSA-C) according to The Gilman Criteria (Gilman et al. 2008). * Participants who are less than five years from the time of documented MSA diagnosis or from the time of documented parkinsonian / ataxic neurological condition that later turns out to be MSA. * Participants who are able to walk at least 10 metres with or without assistance. Participants with an anticipated survival of at least three years in the opinion of the investigator. * Participants that are willing to adhere to the study drug regimen. * Participants that are willing and able to perform all protocol-specified assessments and comply with the study visit schedule. * Females of childbearing potential and male participants with partners of childbearing potential must agree to use an effective method of contraception from the time consent is signed until 10 weeks after treatment discontinuation. Females of childbearing potential have a negative pregnancy test within 7 days prior to being randomised. * Willing and able to provide written informed consent. * Subjects who are not able to write may give verbal consent in the presence of at least one witness, and the witness should sign the informed consent form. Exclusion Criteria: * Females who are pregnant, planning pregnancy or breastfeeding. * Women of child-bearing potential who do not practice an acceptable method of birth control. Subjects who meet any of the following criteria which tend to suggest advance disease: 1. Speech impairment as assessed by a score of ≥ 3 on UMSARS question 1 2. Swallowing impairment as assessed by a score of ≥ 3 on UMSARS question 2 3. Impairment in ambulation as assessed by a score of ≥ 3 on UMSARS question 7 4. Falling more frequently than once per week as assessed by a score of ≥ 3 on UMSARS question 8. Participants with a clinically significant or unstable medical or surgical condition, which in the opinion of the investigator might preclude safe completion of the study. * Participants with active malignant neoplasms or history of malignant neoplasm in the last 5 years. Participants with movement disorders other than MSA. * Concurrent dementia defined by a score lower than 21 on the MoCA. * Concurrent severe depression defined by a score of ≥30 on the Beck Depression Inventory-II. * History of deep brain stimulation surgery. * Participants who have taken any investigational products within 90 days prior to baseline. * Participants with a BMI \< 18.5. * Participants with diabetes, end stage renal disease or severely impaired renal function. * History of clinically significant cardiac disease, pancreatitis and/or alcoholism. * Participants with severe gastrointestinal disease including gastroparesis. * Ongoing treatment with sulphonylurea. * Known allergies to the IMP and excipients of IMP.