A Study of CREXONT (Carbidopa and Levodopa) Extended-Release Capsules in Participants With Parkinson's Disease

Inclusion Criteria

• •1. Participants with PD consistent with the United Kingdom Parkinson's Disease Society Brain Bank Diagnostic Criteria and who are being treated with stable regimens of oral CD-LD.
• •2. Participants with a score of at least 20 units at Screening on the Movement Disorder Society - Unified Parkinson's Disease Rating Scale (MDS-UPDRS) Part III total score in the "Off" state.
• •3. Participants with predictable "Off" periods at Screening defined by a score of 1 or 2 (Complexity of Motor Fluctuations) of the MDS-UPDRS Part IV B (Motor Fluctuations).
• •4. By history, for the 4 weeks (28 days) prior to Screening, the participant experiences.
• •1. Daily predictable "wearing-off" episodes with periods of worsening motor symptoms.
• •2. An average of at least 2.5 cumulative hours per day of "Off" time, during the hours the participant awake.
• •5. At Screening, the participant is able to differentiate "On" state from "Off" state as determined by at least 75 percentage (%) concordance with a trained rater (that is, investigator or qualified and certified site staff) in "On/Off" ratings for 8 ratings over a 4-hour training period. The concordance must include at least one "On" and one "Off" rating in this 4-hour training period.
• •1. If the concordance is less than 75%, or if it does not include at least one "On" and one "Off" rating within the first 4-hour training period, a second 4-hour training period should be conducted with the participant before being considered for inclusion in the study.
• •2. If during the second 4-hour training-period a concordance of at least 75% is also not achieved, or if it does not include at least one "On" and one "Off" rating, the participant cannot be included in the study.
• •6. At baseline (Visit 1), review of the 3-day PD diaries confirms the following:
• •1. The participant is able to properly complete the PD diaries with valid entries. Inability to properly complete the diaries is indicated when more than 1 day of a diary is not returned or if more than 1 day of the diary is not valid (that is, more than 2 hours \[4 half-hour periods\] of the 24-hour diary day are missing); and
• •2. The participant has an average of at least 2.5 hours per day of "Off" time, during the hours the participant is awake, over the 3 PD diary days; and
• •3. The participant has at least 1.5 hours of cumulative "Off" time, during the hours the participant is awake, on each of the 3 PD diary days.
• •7. Participant is responsive to CD-LD therapy and currently being treated on a stable regimen of oral CD-LD for at least 4 weeks (greater than equal to \[\>=\] 28 days) prior to baseline (Visit 1) and meets the following criteria:
• •a. Daily Dose Requirements: i. All participants should be taking at least 100 mg of immediate-release (IR) CD-LD or 195 mg of Rytary for the first morning dose.
• •ii. For participants taking IR CD-LD (with or without a bedtime dose of CR CD-LD):
• •* Require a total daily dose of at least 300 mg of LD and a maximum total daily dose of less than equal to \[\<=\]1200 mg LD (from IR CD-LD alone or from IR CD-LD in combination with a single daily bedtime dose of CR CD-LD).
• •* The maximum individual dose allowed is 250 mg of LD.
• •* The minimum individual dose should be at least 100 mg of LD. iii. For participants using a catechol-O-methyltransferase (COMT) inhibitor:
• •* Require a total daily dose of at least 300 mg of LD and a maximum total daily dose of less than \[\<\]1000 mg LD.
• •* The maximum individual dose is 200 mg of LD. iv. For participants using Rytary:
• •* Require a total daily dose of at least 585 mg of LD and a maximum total daily dose of \<2100 mg LD.
• •* The maximum individual dose is 685 mg of LD. b. Dose Frequency Requirement: i. If a participant is using IR/CR CD-LD alone or in combination with a COMT inhibitor, then the dosing frequency must be 3 to 6 times daily. ii. If a participant is using Rytary, then the dosing frequency must be 3 to 4 times daily.
• •8. Participant is able and willing to provide written informed consent prior to the conduct of any study-specific procedures.
• •9. Participant is able and willing to comply with the protocol, including completion of PD diaries, questionnaires, and available for all study visits and telephone calls.
• •10. Participants who have participated in prior CREXONT clinical studies are allowed to be enrolled in this Phase 4 study.