Pardoprunox in early Parkinson's disease: results from 2 large, randomized double-blind trials.

This report presents the results of 2 randomized trials-Rembrandt and Vermeer-on the efficacy and safety of pardoprunox in patients with early Parkinson's disease. Patients with Parkinson's disease with a Unified Parkinson's Disease Rating Scale-Motor score ≥ 10 and modified Hoehn and Yahr stage ≤ 3 were randomized to pardoprunox (fixed doses of 6 mg/day [n = 115] or 12 mg/day [n = 118] or a flexible-dose range of 12-42 mg/day [n = 116]) or placebo (n = 119) in Rembrandt and pardoprunox 12-42 mg/day (n = 108), pramipexole 1.5-4.5 mg/day (n = 116), or placebo (n = 110) in Vermeer. Pardoprunox showed a significant benefit over placebo in the primary efficacy variable, least-square mean change from baseline in Unified Parkinson's Disease Rating Scale-Motor score: Rembrandt-fixed doses of 6 and 12 mg/day, -6.0 and -4.7 points, respectively; flexible-dose 12-42 mg/day, -5.5 points; placebo, -2.9 points; Vermeer-flexible-dose 12-42 mg/day, -4.9 points; placebo, -2.5 points; pramipexole, -5.7 points. No minimum effective dose was established. Secondary efficacy parameters supported the results of the primary efficacy variable. Pardoprunox tolerability was dose related: flexible-dose 12-42 mg/day showed the highest dropout rate due to treatment-emergent adverse events (Rembrandt, 56.0%; Vermeer, 46.3%) and overall incidence of treatment-emergent adverse events (Rembrandt, 97.4%; Vermeer, 92.6%), primarily due to nausea, somnolence, and dizziness. Because pardoprunox showed similar efficacy across all dose groups, these observations suggest that the 12-42 mg/day dose range was higher than therapeutically required. Furthermore, the early onset of treatment-emergent adverse events and dropouts observed for pardoprunox suggest that titration was too rapid. Pardoprunox significantly improved motor symptoms in patients with early Parkinson's disease, but further investigation into the dose and titration schedule is required to improve tolerability.

Double-blind study of pardoprunox, a new partial dopamine agonist, in early Parkinson's disease.

This study examined the efficacy and safety of the partial dopamine agonist, pardoprunox (SLV308), in the treatment of patients with early Parkinson's disease (PD). Patients were randomized to receive pardoprunox (n = 69) or placebo (n = 70). Pardoprunox was titrated to each patient's optimal dose (9-45 mg/d) over 2 to 6 weeks and then maintained at this dose for a further 3 weeks. Concomitant anti-Parkinson treatment was not permitted. In the primary analysis, Unified PD Rating Scale (UPDRS)-Motor score was improved in pardoprunox-treated patients (overall mean dose 23.8 mg/d; -7.3 points), as compared with placebo (-3.0 points; P = 0.0001), from baseline to end point. At end point, there were more responders (> or = 30% reduction in UPDRS-Motor score) in the pardoprunox group (50.7%) than in the placebo group (15.7%; P < 0.0001). In other secondary analyses, UPDRS-activities of daily living (ADL) and -ADL+Motor scores were also significantly more improved in the pardoprunox group. Nausea was reported by 32 of 68 (47.1%) pardoprunox-treated patients (vs. 3/70, 4.3%, placebo-treated patients), with dizziness, somnolence, headache, and asthenia also reported by > or = 10 patients. In this exploratory proof-of-concept study, pardoprunox significantly improved motor function in patients with early PD. The efficacy and safety profile of pardoprunox justifies its further investigation in PD.

MK-801 alters the effects of priming with L-DOPA on dopamine D1 receptor-induced changes in neuropeptide mRNA levels in the rat striatal output neurons.

In a previous study, we have shown in unilaterally dopamine-depleted rats that increased behavioral responsiveness to the dopamine D1-receptor agonist SKF-38393, which was induced by pretreatment with L-DOPA, is paralleled by specific alterations in striatal neuropeptide mRNA levels. The behavioral 'priming' effect of L-DOPA is prevented if L-DOPA is preceded by the NMDA-receptor antagonist MK-801. In the present study, the question is addressed whether blockade of the increased behavioral responsiveness with MK-801 also prevents the observed changes in striatal neuropeptide mRNA levels. After a challenge with SKF-38393 (3 mg/kg, s.c.), the striatal levels of preprodynorphin, preprotachykinin, and preproenkephalin mRNA were compared between unilaterally dopamine-depleted rats that were either primed with a single administration of L-DOPA (50 mg/kg, i.p.) or with L-DOPA preceded by MK-801 (0.1 mg/kg, i.p.). Priming with L-DOPA enhanced the increase in dynorphin mRNA levels in the dorsolateral part of the dopamine-depleted striatum that occurred after SKF-38393. On the other hand, it had no significant effect on substance P or enkephalin mRNA levels. MK-801 prior to L-DOPA prevented the increased responsiveness of dynorphin regulation. However, it induced a decreased response to dopamine D1-receptor stimulation in the substance P mRNA levels in dorsal regions of the dopamine-depleted striatum. The levels of enkephalin mRNA after challenge with SKF-38393 were not affected by the MK-801 administration. These results demonstrate that the increased behavioral responsiveness to the D1-receptor agonist SKF-38393 after priming with L-DOPA is primarily related to the upregulation of dynorphin mRNA levels in the dopamine-depleted striatum.