18-month Study of Long-term Efficacy & Safety of Safinamide as add-on Therapy in Patients With Mid-late Stage PD

Inclusion Criteria: * The patient completed 24 weeks of treatment in Study 016, or, if the patient discontinued prematurely, he/she returned for scheduled efficacy evaluations at Weeks 12 and 24, as part of the Retrieved Dropout (RDO) population. * The patient was compliant with taking study medication in Study 016. * The patient is willing to participate in the study and signed an approved Informed Consent form. Exclusion Criteria: * The patient is experiencing clinically significant adverse events that would put the patient at risk for participating in the study. * The patient has shown clinically significant deterioration during participation in Study 016, and has reached Hoehn and Yahr Stage V. * The patient discontinued Study 016 prematurely for any reason, and did not return for scheduled efficacy evaluations at Weeks 12 and 24.