This is a study to compare the efficacy of IPX066 and CLE in subjects with advanced Parkinson's disease.

This is a randomized, double-blind, double-dummy, 2 treatment, 2-period crossover study followed by an open-label extension study period.

Inclusion Criteria:

1. Diagnosed with idiopathic Parkinson's Disease (PD).

2. At least 30 years old at the time of PD diagnosis.

3. Currently being treated with carbidopa/levodopa/entacapone (CLE) and on a stable regimen of conventional LD for at least 4 weeks and:

   • Requiring a total daily levodopa (LD) dose of at least 400 mg
   • Having a minimum dosing frequency of four times per day.
   • Individual CD-LD or CLE doses that contain an LD dose which is a multiple of 50 mg.

4. Able to differentiate "on" state from "off" state.

5. Have predictable "off" periods.

6. Amantadine, anticholinergics, selective monoamine oxidase (MAO) type B inhibitors (e.g., selegiline, rasagiline) or dopamine agonists are allowed as long as the doses and regimens have been stable for at least 4 weeks prior to Screening and the therapy is intended to be constant throughout the course of the study.

7. Agrees to use a medically acceptable method of contraception throughout the study and for 1 month afterward.

Exclusion Criteria:

1. Diagnosed with atypical Parkinsonism or any known secondary Parkinsonian syndrome.
2. Nonresponsive to LD therapy.
3. Prior functional neurosurgical treatment for PD (e.g., ablation or deep brain stimulation) or if such procedures are anticipated during study participation.
4. Received within 4 weeks of Screening or planning to take during participation in the clinical study: any controlled-release LD product, tolcapone, apomorphine, nonselective MAO inhibitors, or antipsychotics including neuroleptic agents for the purpose of treating psychosis or bipolar disorder.
5. Allergy or hypersensitivity to CD, LD, entacapone, riboflavin, Yellow Dye #5 (tartrazine), citrus fruit or grape juice.
6. History of or currently active psychosis.
7. Active or prior medical conditions such as peptic ulcers or prior surgical (e.g., bowel) procedures that would interfere with LD absorption.
8. Active or history of narrow-angle glaucoma.
9. History of malignant melanoma or a suspicious undiagnosed skin lesion.
10. History of myocardial infarction with residual atrial, nodal, or ventricular arrhythmias, upper gastrointestinal hemorrhage, or neuroleptic malignant syndrome or nontraumatic rhabdomyolysis.
11. Received any investigational medications during the 4 weeks prior to Screening.
12. Unable to swallow large pills (e.g., large vitamin pills).
13. Pregnant or breastfeeding.
14. Subjects who are unable to complete a symptom diary.