Low doses of sarizotan reduce dyskinesias and maintain antiparkinsonian efficacy of l-Dopa in parkinsonian monkeys

Dyskinesia is an important complication of treatment in Parkinson's disease (PD). Sarizotan, a 5-HT1A agonist with high affinity for D3 and D4 receptors was investigated on l-Dopa-induced dyskinesia (LID) in the 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) animal model of PD. Five MPTP female cynomolgus monkeys (Macaca fascicularis) with a moderate to severe parkinsonian syndrome and LID were used. Sarizotan 0.2, 1, and 2 mg/kg administered alone did not worsen parkinsonian symptoms; there were no effect on locomotor counts or on normal behavior of the monkeys. Sarizotan 0.2, 1, and 2 mg/kg administered 30 min before a fixed dose of l-Dopa (25–30 mg/kg s.c.) + benserazide (50 mg) did not affect the antiparkinsonian response to l-Dopa. However, mean dyskinetic scores were significantly reduced with sarizotan 1 and 2 mg/kg but not at 0.2 mg/kg. Higher doses of sarizotan (4 and 8 mg/kg, administered immediately before l-Dopa) reduced l-Dopa-induced locomotor response in all monkeys. A pharmacokinetic investigation in these monkeys showed a dose-dependent increase in mean plasma sarizotan concentrations with similar mean plasma concentrations for sarizotan 1 mg/kg alone or with l-Dopa, indicating a lack of sarizotan/l-Dopa interaction. The time course of plasma sarizotan concentrations was associated with time of maximal reduction of dyskinesias. When administered daily for two weeks in combination with l-Dopa in the same MPTP monkeys, sarizotan 1 mg/kg had a sustained antidyskinetic effect while maintaining the antiparkinsonian and locomotor effect of l-Dopa. This detailed sarizotan investigation in MPTP monkeys supports the antidyskinetic activity of this drug and for 5-HT1A agonists.