The main purpose of this study is to follow and observe a group of people living with Parkinson's disease to see how study participation affects their signs and symptoms in the months after starting in the study. While taking part in this study participants will take their usual medication as prescribed. However, the study doctor may recommend adjustments to their medication to provide a better treatment of their Parkinson's disease. Participation will last from 3 up to 24 months. During visits to the clinic, the study doctor or study nurse will evaluate signs and symptoms of Parkinson's disease using several different assessments. At a minimum of 2 visits participants will be asked to undergo 'off'-assessments.

Inclusion Criteria:

• Male or female, aged 50-68 years (both inclusive) at the time of signing informed consent.
• Diagnosed with Parkinson's disease using the Movement Disorder Society (MDS) criteria (fulfilling the definition of clinically probable Parkinson's disease).
• Moderate Parkinson's disease, e.g. as defined by i) modified Hoehn and Yahr stage 2-3 in OFF state and ii) MDS-Unified Parkinson's Disease Rating Scale (MDS-UPDRS) Part III total score greater than or equal to (≥) 30 in OFF state, both as judged by the investigator.
• Patient has symptoms that are not adequately controlled by existing oral anti-Parkinson's disease medications, i.e., having both ON and OFF periods, as judged by the investigator.
• Parkinson's disease duration greater than (>) 5 years and lesser than or equal to (≤) 12 years from diagnosis at the time of signing informed consent.
• Potential candidate for a future cell therapy transplantation, as judged by the investigator.
• Life expectancy >7 years as judged by the investigator.

Exclusion Criteria:

• Any atypical or secondary Parkinson's disease, or non-Parkinson's disease-suspected cause(s) of, or contributors to, parkinsonism, as judged by the investigator.
• Significant drug-induced dyskinesias as judged by the investigator, e.g., as defined by a score of > 2 in the Abnormal Involuntary Movement Scale (AIMS), in any body part in the ON state.
• Tremor-dominant Parkinson's disease, as judged by the investigator.
• Cognitive impairment predictive of dementia (including Parkinson's disease dementia) or other cognitive dysfunction as judged by the investigator, e.g., as defined by Montreal Cognitive Assessment (MoCA) score ≤ 24, or evidence of major neurocognitive disorder according to the Diagnostic and Statistical Manual of Mental Disorders V (DSM-V) criteria.
• Major medical or psychiatric disorder (e.g., depression (Montgomery-Asberg Depression Rating Scale (MADRS) >20) or psychosis), or other disease making the patient unsuited for participation in the study, as judged by the investigator.
• Treatment for dystonia or spasticity within 3 months of screening (Botox for a focal dystonia is allowed).
• Substantial neurological symptoms not accounted for by Parkinson's disease, including active seizure disorder, as judged by the investigator.

Participants with Parkinson's disease will be included. The participants will not receive any investigational treatment in this study.

According to the Novo Nordisk disclosure commitment on novonordisk-trials.com