Extension Study To Evaluate Safety And Tolerability Of 24-Hour Daily Exposure Of Continuous Subcutaneous Infusion of ABBV-951 In Adult Participants With Parkinson's Disease

Percentage of Participants With Adverse Events (AE)

An AE is defined as any untoward medical occurrence in a participant or clinical investigation participant administered a pharmaceutical product and which does not necessarily have a causal relationship with the treatment. The investigator assesses the relationship of each event to the use of the study drug or device as either reasonable possibility or no reasonable possibility. A serious adverse event (SAE) is an event that results in death, is life-threatening, requires or prolongs hospitalization, results in a congenital anomaly, persistent or significant disability/incapacity or is an important medical event that, based on medical judgment, may jeopardize the participant and may require medical or surgical intervention to prevent any of the outcomes listed above. Adverse Events of Special Interest (AESI) - polyneuropathy, weight loss, hallucinations/psychosis, and somnolence will be monitored throughout the study.

Time frame: Up To Week 96

Percentage Of Participants With Numeric Grade Equal To Or Higher Than 5 On The Infusion Site Evaluation Scale

The Infusion Site Evaluation Scale will be used to assess infusion sites. Infusion Site Evaluation Scale is an eight-point numeric scale used to assess irritation at the infusion site area (0 being "no evidence of irritation" and 7 being "strong reaction spreading beyond the test site").

Time frame: Up To Week 96

Percentage Of Participants With Letter Grade Equal To Or Higher Than D On The Infusion Site Evaluation Scale

The Infusion Site Evaluation Scale will be used to assess infusion sites. Infusion Site Evaluation Scale is an A to G letter grade scale, used to assess irritation at the infusion site area (A being "no finding" to G being "Small petechial erosions and/or scabs").

Time frame: Up To Week 96

Change in Clinical Laboratory Test Data

Number of participants with clinically significant change from baseline in laboratory parameters (hematology, biochemistry, coagulation, and urinalysis) will be reported throughout the study.

Time frame: Up To Week 96

Change in Vital Signs Measurements

Number of participants with clinically significant change from baseline in vital signs will be reported throughout the study.

Time frame: Up To Week 96

Change From Baseline in Electrocardiograms (ECGs)

Change from baseline in 12-lead ECGs on heart rate, RR interval, PR interval, QRS duration, and QT interval will be monitored throughout the study.

Time frame: Up To Week 96