This is a multi-center, randomized, double-blind, placebo-controlled, 2-arm, parallel group study to evaluate the efficacy and safety of ADS-5102 extended release (ER) capsules, an investigational formulation of amantadine, dosed once nightly at bedtime for the treatment of levodopa induced dyskinesia (LID) in subjects with Parkinson's disease (PD). The novel pharmacokinetic profile of ADS-5102 is expected to achieve i) maximal concentrations in the early morning through mid-day, when LID can be troublesome, and ii) lower concentrations in the evening, potentially reducing the negative impact of amantadine on sleep. This pharmacokinetic profile could enable higher doses to be tolerated with a once-nightly ER formulation than can be tolerated with an immediate-release formulation. The once-nightly dosing regimen may also provide enhanced convenience and compliance.

In a previous clinical study, ADS-5102 met its primary endpoint; LID was significantly reduced as measured by the change in UDysRS score over 8 weeks vs. placebo.

Inclusion Criteria:

• Signed a current IRB/REB/IEC-approved informed consent form
• Parkinson's disease, per UK Parkinson's Disease Society (UKPDS) Brain Bank Clinical Diagnostic Criteria
• On a stable regimen of antiparkinson's medications for at least 30 days prior to screening, including a levodopa preparation administered not less than three times daily, and willing to continue the same doses and regimens during study participation
• Following diary training, the subject is willing and able to understand and complete the 24-hour PD home diary (caregiver/study partner assistance allowed)
• Any other current and allowed prescription/non-prescription medications and/or nutritional supplements taken regularly must have been at a stable dose and regimen for at least 30 days prior to screening, and subject must be willing to continue the same doses and regimens during study participation (this criterion does not apply to medications that are being taken pre-study only on an as-needed basis)

Exclusion Criteria:

• History of neurosurgical intervention related to Parkinson's disease (e.g. deep brain stimulation)
• History of seizures within 2 years prior to screening
• History of stroke or transient ischemic attack (TIA) within 2 years prior to screening
• History of cancer within 5 years prior to screening, with the following exceptions: adequately treated non-melanomatous skin cancers, localized bladder cancer, non-metastatic prostate cancer or in situ cervical cancer
• Presence of cognitive impairment, as evidenced by a Mini-Mental Status Examination (MMSE) score of less than 24 during screening
• If female, is pregnant or lactating
• If a sexually active female, is not surgically sterile or at least 2 years post-menopausal, or does not agree to utilize an effective method of contraception from screening through at least 4 weeks after the completion of study treatment.
• Treatment with an investigational drug or device within 30 days prior to screening
• Treatment with an investigational biologic within 6 months prior to screening
• Current participation in another clinical trial