This is a 105-week open-label study to evaluate the safety and tolerability of ADS-5102 oral capsules, an extended release formulation of amantadine, in Parkinson's Disease (PD) patients with Levodopa Induced Dyskinesia (LID).

Participation in this study was offered to subjects who were described by one of the following 3 groups:

• Group 1: Subjects who completed an Adamas efficacy study evaluating ADS-5102 in LID and chose to immediately transition into the current study without a time gap; this group was subdivided into Group 1A, consisting of subjects who received ADS-5102 in the previous Adamas efficacy study, and Group 1P, consisting of subjects who received placebo in the previous Adamas efficacy study
• Group 2: Subjects who completed a previous Adamas efficacy study evaluating ADS-5102 in LID and entered the current study with a time gap
• Group 3: Subjects who would have been deemed ineligible for participation in a previous Adamas efficacy study due to having undergone DBS

Consented subjects who completed Screening (Visit 1) and met study eligibility criteria were to have a Baseline Visit and receive study drug. During Week 1, subjects took 170 mg of ADS-5102 (1 capsule) daily at bedtime. For Week 2, the dose was increased to 340 mg (2 capsules) daily at bedtime; this dose was to continue through Week 100. During the final week (Week 101) of the study, the ADS-5102 dose was reduced to 170 mg (1 capsule) daily at bedtime. Subjects were enrolled into the study at Visit 2 (Baseline/Week 0) and were to return to the clinic after 4, 8, 16, 28, 40, 52, 64, 76, 88, and 100 weeks of study drug dosing. Subjects were to receive a telephone reminder at the end of Week 1 to increase their dose during Week 2. At the Week 100 Visit, subjects were instructed to reduce their dose to 1 capsule daily at bedtime for 1 week. The amount of available, unused drug was assessed during the Week 100 Visit; subjects were given an additional bottle of study drug, if needed, to complete the 1 week of reduced dosing.

Efficacy, as measured with the MDS-UPDRS, was to be evaluated at all study visits, beginning with the Screening Visit, and excluding the Baseline and Week 4 Visits. A Safety Follow-up Visit was to occur approximately 2 weeks following the completion of treatment. AEs were recorded beginning with the first dose of study drug and continued through the Safety Follow-up Visit. Concomitant medications were recorded throughout the study.

Inclusion Criteria:

• Signed a current IRB/REB/IEC-approved informed consent form
• Completed all study visits in previous Adamas efficacy study or were ineligible for participation in previous Adamas studies due to having undergone prior deep brain stimulation.
• Parkinson's disease, per UK Parkinson's Disease Society (UKPDS) Brain Bank Clinical Diagnostic Criteria
• On a stable regimen of antiparkinson's medications at least 30 days prior to screening, including a levodopa preparation administered not less than three times daily.
• History of peak dose dyskinesia that might benefit from specific dyskinesia treatment in the judgment of the subject and clinical investigator

Exclusion Criteria:

• Discontinued ADS-5102 in previous Adamas efficacy study due to intolerable or unacceptable AEs considered to be related to ADS-5102
• History of neurosurgical intervention related to Parkinson's disease, with the exception of deep brain stimulation
• History of seizures since completion of participation in previous Adamas studies or within 2 years
• History of stroke or TIA since completion of participation in previous Adamas studies or within 2 years
• History of cancer since completion of participation in previous Adamas studies or within 2 years, 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 (other than ADS-5102) or device within 30 days prior to screening
• Treatment with an investigational biologic within 6 months prior to screening
• Current or planned participation in another interventional clinical trial