Meta-analysis of Placebo-controlled Clinical Trials of Safinamide and Entacapone as Add-on Therapy to Levodopa in the Treatment of Parkinson's Disease

Abstract

Chronic levodopa (L-dopa) treatment of Parkinson’s disease (PD) patients is sooner or later associated with the onset of motor complications, for example wearing off and dyskinesia. PD patients with motor complications usually require the addition of further PD drugs to reduce these L-dopa side effects and enhance its efficacy. Entacapone is an available catechol-O-methyltransferase (COMT) inhibitor, which was extensively investigated as add-on to L-dopa/dopadecarboxylase inhibitor (DDCI) application in PD patients. Safinamide, a watersoluble, orally active a-aminoamide derivative, which modulates dopaminergic and glutamatergic neurotransmission with a unique dual mechanism of action, has been studied in two placebo-controlled clinical trials as add-on therapy to L-dopa in fluctuating PD patients. To date, there are no head-to-head clinical trials comparing the efficacy of safinamide and entacapone in the clinic. The aim of this meta-analysis was to determine effect sizes of safinamide and entacapone as add-on treatment to L-dopa in fluctuating PD patients. A systematic search of the literature on entacapone trials up to the end of September 2014 was first conducted on the MEDLINE and EMBASE databases in order to identify appropriate studies. Definition criteria for inclusion were prospective, randomised, placebocontrolled and double-blinded trials on the efficacy and safety of entacapone or safinamide in fluctuating L-dopa-treated PD patients. Four studies for entacapone and two trials on safinamide were considered. Data from the safinamide trials were provided by Zambon and therefore ‘safinamide’ was not used as a search term. Safinamide and entacapone treatment was comparable in terms of the main efficacy variables ( off time, percentage on time, Unified Parkinson’s Disease Rating Scale). Significant advantages in favour of safinamide were shown in terms of the total incidence of adverse events (AEs) in comparison to placebo, the study discontinuation due to AEs and deaths and in the risk differences of the AEs versus placebo, particularly for nausea, vomiting, diarrhoea, dizziness, urine abnormality and shortness of breath. The odds ratio (OR) of 0.907 for any AE corresponds to an overall AE rate of 68.7 % for safinamide whereas the OR of 2.089 to an overall AE rate of 84.4 % for entacapone.