Study Comparing Continuous Subcutaneous Infusion Of ABBV-951 With Oral Carbidopa/Levodopa Tablets For Treatment Of Motor Fluctuations In Adult Participants With Advanced Parkinson's Disease
Study Comparing Continuous Subcutaneous Infusion Of ABBV-951 With Oral Carbidopa/Levodopa Tablets For Treatment Of Motor Fluctuations In Adult Participants With Advanced Parkinson's Disease
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. This study measures the efficacy,
 safety, and tolerability of ABBV-951 versus oral Levodopa (LD)/Carbidopa (CD) [LD/CD] in
 advanced PD participants to achieve reduction in motor fluctuations.

 ABBV-951 is an investigational (unapproved) drug containing Levodopa Phosphate/Carbidopa
 Phosphate (LDP/CDP) given subcutaneously (under the skin) for the treatment of Parkinson's
 Disease. The study has two treatment arms . In one arm, participants will be given ABBV-951
 plus oral placebo (does not contain treatment drug). In the second arm, participants will be
 given placebo solution and LD/CD tablets. Adult participants with advanced PD will be
 enrolled. Approximately 130 participants will be enrolled in the study in approximately 80
 sites across the world.

 In one arm, participants will receive ABBV-951 solution as a continuous infusion under the
 skin plus oral placebo capsules for LD/CD. In the second arm, participants will receive
 placebo solution for ABBV-951 as a continuous infusion under the skin plus oral capsules
 containing LD/CD tablets. The treatment duration is 12 weeks.

 There may be higher treatment burden for participants in this trial compared to their
 standard of care. Participants will attend regular visits during the course of the study at a
 hospital or clinic. The effect of the treatment will be checked by medical assessments, blood
 tests, checking for side effects, and completing questionnaires.
Inclusion Criteria:

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

 -  Participants must be taking a minimum of 400 milligrams/day (mg/day) of Levodopa (LD)
 equivalents and be judged by the investigator to have motor symptoms inadequately
 controlled by current therapy, have a recognizable/identifiable "Off" and "On" states
 (motor fluctuations), and have an average "Off" time of at least 2.5 hours/day over 3
 consecutive PD Diary days with a minimum of 2 hours each day.

 -  Participant or caregiver, if applicable, demonstrates the understanding and correct
 use of the delivery system, including the insertion of the cannula into the
 participant's abdomen, as assessed by the investigator or designee during the
 Screening period.

 Exclusion Criteria:

 -  Clinically significant, unstable medical conditions or any other reason that the
 investigator determines would interfere with the participant's participation in this
 study or would make the participant an unsuitable candidate to receive study drug.

 -  History of allergic reaction or significant sensitivity to LD or constituents of the
 study drug (and its excipients) and/or other products in the same class.

 -  Has known active Coronavirus Disease - 2019 (COVID-19) infection.