To be able to join the ATLANTIS Study, you must:

• Be between 35 and 80 years of age
• Have been diagnosed with Parkinson’s disease 5 or more years ago
• Be experiencing daily motor fluctuations (at least 2 cumulative hours of “OFF” time every day when Parkinson’s disease symptoms return after the medication has worn off)
• Currently be receiving treatment with levodopa (with or without additional therapies for Parkinson’s disease)
• Be willing to complete a 3-day symptom diary at four time points during the study

You cannot participate in the study if you:

• Have had brain surgery for PD (including deep brain stimulation or thalamus surgery)
• Are using parenteral PD medication (medication that is infused or injected)
• Have a diagnosis of dementia, other forms of important cognitive dysfunction, epilepsy or another seizure disorder
• Have a history or current diagnosis of Type 1 diabetes or uncontrolled Type 2 diabetes or have current untreated hypertension (high blood pressure)
• Have had major depression or psychotic disorder or any other psychiatric condition within the past 5 years
• Have a history of alcohol or drug use disorder
• Have a positive drug/alcohol test, HIV test or hepatitis B test when you join the study

Other criteria will need to be met in order to participate in this study. Your study team will discuss these with you.

Participation in the ATLANTIS Study will last up to a little over 4 months and will involve a total of 10 visits to the study site.

During Screening, the study doctor will perform several tests and assessments to confirm you meet all the study criteria. Provided you can continue in the study, you will then begin the Treatment Period. After the Treatment Period, you move into the Safety Follow-up Period where you will have a follow-up visit after you stopped taking the study medication.

The assessments performed during the study can include:

• Discussing your medical history
• Discussing your current medications
• Having physical and neurological examinations
• Having your vital signs taken (blood pressure, pulse, breathing rate, and body temperature)
• Having your height and weight measured
• Providing blood and urine samples for laboratory testing
• Having an ECG to check your heart’s activity
• Completing questionnaires

Your study team and an informed consent document you will receive will tell you more about the different study visits and what exactly happens during these visits.

During the ATLANTIS Study, we will compare two different doses of UCB0022 to a placebo in addition to your regular medication(s) for Parkinson’s disease. A placebo looks like the UCB0022 medication but contains no medicinally active ingredients. The study medication is taken by mouth as tablets once a day.

You will be randomly assigned (like drawing straws) to one of three possible study treatment groups. There is a:

• 1 in 3 chance that you will receive the lower dose of UCB0022
• 1 in 3 chance that you will receive the higher dose of UCB0022
• 1 in 3 chance that you will receive a placebo

The ATLANTIS study is blinded, which means that neither you, your care partner, nor the study team will know or be able to decide whether you will be receiving UCB0022 or a placebo during the ATLANTIS Study.

On four occasions during the study you will be asked to record your Parkinson’s disease symptoms for three consecutive days in a simple and easy to complete paper document (study diary) you will be given. These diary entries are important in showing if there are, or are not, any changes in symptoms while you are taking the study medication.

You will also be asked to fill out some questionnaires at home on two occasions. These will be completed electronically on a tablet computer. If you have a care partner, he or she will be asked to complete a questionnaire about their experience of what it’s like to care for someone with PD.

The study uses a wrist-worn device very similar to a normal smartwatch that automatically records movements and motor symptoms. This device will be given to patients who are 46 years or older and needs to be given back after the study ends. It monitors your movement throughout the study while you are awake and sleeping.

You and your care partner will have the option of travel support to and from your study visits, as well as being reimbursed for reasonable expenses and a stipend may also be paid.