Parkinson's disease (PD) is a neurological condition, which affects the brain. PD gets worse over time, but how quickly it progresses varies a lot from person to person. Some symptoms of PD are tremors, stiffness, and slowness of movement. The purpose of this study is to evaluate how effective ABBV-951 is in treating adult participants with advanced PD in real world setting.

ABBV-951 (foslevodopa/foscarbidopa) is an approved drug for the treatment of Parkinson's Disease. The main ROSSINI study will have approximately 450 adult participants with PD (300 participants new to ABBV-951, up to 150 participants transitioning from open-label extension study) will be enrolled across approximately 60 sites. Decision to treat with ABBV-951 (or continue the treatment in Cohort B) will be made by the doctor prior to any decision to approach the participant to participate in this study. There will be a sub-study that will enroll 40 naïve participants who initiated Foslevodopa/Foscarbidopa treatment for the first time (Cohort A of the ROSSINI parent study only) from 6 to 15 centers in the United States, Germany and Spain.

All participants will receive subcutaneous infusion of ABBV-951 for approximately 3 years.

Participants will attend regular clinic visits during the course of the study. The effect of the treatment will be checked by medical assessments, and completing questionnaires.

Inclusion Criteria:

• Eligibility for ABBV-951 therapy in accordance with the approved local label in the participating country and local reimbursement regulations, if applicable.

• Diagnosis of levodopa-responsive idiopathic Parkinson's Disease (PD).

• Participant must be either:

  • Cohort A: Naïve to ABBV-951
  • Cohort B: Pre-treated with ABBV-951, specifically, participants of Open-Label Extension Studies M15-737 and M20-098 who completed these studies without significant protocol deviations and who did not experience an adverse event (AE) that in the investigator's opinion may indicate an unacceptable safety risk.

• Decision to treat with ABBV-951 (or continue the treatment in Cohort B) made by the clinician prior to any decision to approach the participant to participate in this study.

• Prior to any study-related procedures being performed, the participant, or legal authorized representative (LAR) has voluntarily signed an Authorization for Use/Disclosure of Data (AUDD)/informed consent form (ICF) according to national regulations after the study has been explained and the participant has had the opportunity to have questions answered.

Exclusion Criteria:

• Any condition included in the contraindications section of the approved local ABBV-951 label in the participating country.

• Mini-Mental State Examination (MMSE) score < 24.

  • If the participant has a score of 19-23, he/she can be included if based on the investigator´s judgment the participant is able to handle the therapy and follow the study procedures with the help of a permanent caregiver.

• Participation in a concurrent interventional clinical trial from enrollment and throughout the study.

• History of significant skin conditions or disorders per investigator´s judgment. In case of temporary affections like recent sunburn, acne, scar tissue, tattoo, open wound, branding, or colorations, the participant should not be included if the investigator considers these as interfering with the infusion of study drug or with study assessments.

Participants with Advanced PD, treated with ABBV-951 according to label and local reimbursement regulations, where applicable.