Safinamide is an α-aminoamide with both dopaminergic and nondopaminergic mechanisms of action evaluated as an add-on to dopamine agonist (DA) therapy in early-stage PD. In this 24-week, double-blind study, patients with early PD receiving a stable dose of a single DA were randomized to once-daily safinamide 100 mg, safinamide 200 mg, or placebo. The primary efficacy variable was UPDRS part III (motor examination) total score. Analysis was hierarchical: 200 mg of safinamide versus placebo was tested first; the success of safinamide 100 mg versus placebo was contingent on this. Two hundred sixty-nine patients received safinamide 100 mg (n = 90), safinamide 200 mg (n = 89), or placebo (n = 90); 70, 81, and 81 patients, respectively, completed the study. Mean improvements from baseline to week 24 in UPDRS III total scores were -3.90 for safinamide 200 mg, -6.0 for safinamide 100 mg and -3.60 for placebo. The difference between safinamide 200 mg and placebo was not significant [point estimate: -0.4; 95% confidence interval (CI): -2.3-1.4; P = 0.6504]. Although the difference between 100 mg/day and placebo was significant (point estimate: -1.9; 95% CI: -3.7 to -0.1; P = 0.0419), these results are considered exploratory. No clinically meaningful differences from placebo were observed for any safety variables. This study did not demonstrate a significant improvement of the primary endpoint for safinamide 200 mg/day. Exploratory analysis of the primary endpoint for 100 mg/day demonstrated that the addition of safinamide to a stable dose of DA improves motor symptoms in early PD and warrants further investigation.
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