To determine the long-term safety and efficacy of a dose range of safinamide of 50-200 mg/day, p.o., compared to placebo, as add-on therapy in patients with early idiopathic Parkinson's disease who are currently receiving a stable dose of a single dopamine (DA) agonist.

The study will consist of 12 months of double-blind treatment. Patients will continue to take the original treatment administered in Study 015 (safinamide 100 mg/day, safinamide 200 mg/day, or placebo).

Inclusion Criteria:

1. The patient completed 24 weeks of treatment in Study 015, or if the patient discontinued prematurely, he/she returned for scheduled efficacy evaluations at Weeks 12 and 24 (Visits 6 and 8) as part of the Retrieved Dropout (RDO) population.
2. The patient was compliant with taking study medication in Study 015.
3. The patient is willing to participate in the study and signed an approved Informed Consent form.

Exclusion Criteria:

1. The patient is experiencing clinically significant adverse events that would put the patient at risk for participating in the study.
2. The patient has shown clinically significant deterioration during participation in Study 015.
3. The patient discontinued Study 015 prematurely for any reason, and did not return for scheduled efficacy evaluations at Weeks 12 and 24 (Visits 6 and 8) in Study 015.