The primary purpose of this study is to demonstrate the superiority of UCB0022 as an adjunctive treatment to stable dose of standard-of-care (SoC) (including at least levodopa therapy) over placebo with regard to motor fluctuations time spent in the OFF state (OFF time) in study participants with advanced Parkinson's Disease (PD).

Inclusion Criteria:

• Study participant must be 35 to 85 years of age (inclusive) at the time of signing the informed consent form (ICF)

• Study participant is diagnosed with Parkinson's disease (PD) (based on the United Kingdom Parkinson's Disease Society Brain Bank Diagnostic criteria performed at the Screening Visit) and diagnosed ≥5 years before the Screening Visit (based on historical medical- information documented by the investigator)

• Study participant has significant daily motor fluctuations

• Study participant is able to complete a Hauser PD symptoms diary and differentiate between the ON and OFF states

• Study participant is responsive to levodopa and currently receiving treatment with oral daily doses of levodopa combination (levodopa/carbidopa or levodopa/benserazide) with or without oral adjunctive antiparkinsonian therapies (based on historical clinical data)

• Study participant has disease severity Stages I-III (modified Hoehn and Yahr staging) during ON state

• Study participant agrees to not post personal medical data or information related to the study on social media until study completion

• Study participant has body weight ≥45 kg and body mass index within 18 to 30 kg/m^2 (inclusive)

• Study participant may be male or female:

  1. A male study participant must agree to use contraception during the Treatment Period and for at least 2 weeks after the last dose of study treatment and refrain from donating sperm during this period
  2. A female study participant must not be a woman of childbearing potential (WOCBP)

Exclusion Criteria:

• Study participant is diagnosed with any form of Parkinsonism other than idiopathic PD (eg, atypical or secondary Parkinsonism)
• Study participant is diagnosed with dementia or has important cognitive dysfunction, as determined by Montreal Cognitive Assessment (MoCA) <23 at screening
• Study participant has a history of neurosurgical intervention for PD (including DBS, thalamotomy, and experimental cell therapy or gene therapy)
• Participant has a severe peak dose or biphasic dyskinesia at screening, defined by Movement Disorder Society Unified Parkinson's Disease Rating Scale (MDS-UPDRS) items 4.2 score 4 or as per investigator opinion
• Participant has a history of major depression or psychotic disorder or any other psychiatric condition within the past 5 years, that, as per investigator opinion, could jeopardize or would compromise the study participant's ability to participate in the study
• Study participant has a history of narrow angle glaucoma
• Study participant has a history of melanoma
• Study participant has current untreated hypertension
• Study participant has a history of hypertensive crisis and/or hypertensive encephalopathy, unless the underlying cause was unequivocally identified and has been removed
• Study participant has orthostatic hypotension requiring medication or a current history of "clinically significant" orthostatic hypotension as per the investigator's opinion (eg, recurrent orthostatic presyncope or syncope)
• Study participant has a history over the past 12 months or between the Screening and Baseline Visits of any clinically significant arrythmia, myocardial infarction, stroke, transient ischemic attack, moderate or severe congestive heart failure (either New York Heart Association Class III or IV or known ejection fraction <40%)

Data from this study may be requested by qualified researchers six months after product approval in the US and/or Europe, or global development is discontinued, and 18 months after trial completion. Investigators may request access to anonymized IPD and redacted study documents which may include: raw datasets, analysis-ready datasets, study protocol, blank case report form, annotated case report form, statistical analysis plan, dataset specifications, and clinical study report. Prior to use of the data, proposals need to be approved by an independent review panel at www.Vivli.org and a signed data sharing agreement will need to be executed. All documents are available in English only, for a pre-specified time, typically 12 months, on a password protected portal. This plan may change if a determination is made that the data cannot be adequately anonymized.

Data from this study may be requested by qualified researchers six months after product approval in the US and/or Europe or global development is discontinued, and 18 months after trial completion.

Qualified researchers may request access to anonymized IPD and redacted study documents which may include: raw datasets, analysis-ready datasets, study protocol, blank case report form, annotated case report form, statistical analysis plan, dataset specifications, and clinical study report. Prior to use of the data, proposals need to be approved by an independent review panel at www.Vivli.org and a signed data sharing agreement will need to be executed. All documents are available in English only, for a pre-specified time, typically 12 months, on a password protected portal

Sponsor and CRO staff is blinded.