In Vitro Characterization of Sarizotan Metabolism: Hepatic Clearance, Identification and Characterization of Metabolites, Drug-Metabolizing Enzyme Identification, and Evaluation of Cytochrome P450 Inhibition

Abstract

ABSTRACT:In vitro biotransformation studies of sarizotan using human liver microsomes (HLM) showed aromatic and aliphatic monohydroxylation and dealkylation. Recombinant cytochromes P450 (P450) together with P450-selective inhibitors in HLM/hepatocyte cultures were used to evaluate the relative contribution of different P450s and revealed major involvement of CYP3A4, CYP2C9, CYP2C8, and CYP1A2 in sarizotan metabolism. The apparent K m, u and V max of sarizotan clearance, as investigated in HLM, were 9 M and 3280 pmol/mg/min, predicting in vivo hepatic clearance of 0.94 l/h, which indicates that sarizotan is a low-clearance compound in humans and suggests nonsaturable metabolism at the targeted plasma concentration (<1 M). This finding is confirmed by the reported human clearance (CL/F of 3.6-4.4 l/h) and by the doselinear area under the curve increase observed with doses up to 25 mg. The inhibitory effect of sarizotan toward six major P450s was evaluated using P450-specific marker reactions in pooled HLM. K i, u values of sarizotan against CYP2C8, CYP2C19, and CYP3A4 were >10 M, whereas those against CYP2D6 and CYP1A2 were 0.43 and 8.7 M, respectively. Based on the estimates of sarizotan concentrations at the enzyme active sites, no clinically significant drug-drug interactions (DDIs) due to P450 inhibition are expected. This result has been confirmed in human DDI studies in which no inhibition of five major P450s was observed in terms of marker metabolite formation.Sarizotan (SZ) hydrochloride is an aminomethyl-chromane that underwent clinical development for levodopa therapy-associated dyskinesia in patients with Parkinson's disease. The occurrence of dyskinesias, or involuntary movements, is one of the most troublesome and debilitating side effects of prolonged treatment with L-dopa, occurring in up to one-third of all patients. In preclinical studies, SZ was effective in induced Parkinson syndrome in monkeys (Bibbiani et al., 2005). In clinical studies, SZ demonstrated proof of concept in an open pilot study and in a placebo-controlled dose-finding study. Single-and multiple-dose studies in healthy volunteers with orally administered SZ hydrochloride revealed rapid absorption (t max 0.5-2.3 h). Subsequently, plasma levels declined polyexponentially with a terminal elimination half-life of 5 to 7 h. C max and t max varied slightly with formulation and food intake, whereas the area under the curve (AUC) was unaffected by these factors. AUC and C max increased dose proportionally over the tested dose range of 0.5 to 25 mg (Kroesser et al., 2006a(Kroesser et al., , 2007.The Food and Drug Administration (FDA) recommends that all new chemical entities (NCEs) in development be characterized with respect to metabolic properties before administration to humans (FDA Guidance for Industry: Drug Interaction Studies-Study Design, Data Analysis and Implications for Dosing and Labeling, http://www.fda. gov/cber/guidelines.htm, 2006). The in vitro characterization involves estimation of the role of metabolism in the clear...

The paraoxonase‐1 pathway is not a major bioactivation pathway of clopidogrel in vitro

“…The specific CYP inhibitors (Dierks et al ., 2001) used in this study were 3 µM ketoconazole for CYP3A, 3 µM quinidine for CYP2D6, 5 µM sulfaphenazole for CYP2C9, 30 µM furafylline for CYP1A2, 50 µM omeprazole for CYP2C19 and 1 µM 4‐(4‐chlorobenzyl) pyridine for CYP2B6 (Korhonen et al ., 2007; Gallemann et al ., 2010). The PON1 inhibitor used is this study was 1 mM EDTA (Gonzalvo et al ., 1997).…”

Intramolecular carbolithiation of N-allyl-ynamides: an efficient entry to 1,4-dihydropyridines and pyridines – application to a formal synthesis of sarizotan

“…The pyridinyl-chroman sarizotan (also called EMD-128130) was originally developed by Merck KGaA in the late 1990’s [44] and was found to be a dual selective 5-HT 1A receptor agonist and D 2 receptor antagonist displaying a strong efficacy in the reduction of dyskinesia resulting from long-term antiparkinsonian treatment with levodopa [45–50]. Although its development was stopped by Merck KGaA in 2006 after analysis of data from Phase III clinical trials failed to confirm its efficiency [51], sarizotan is still under intense investigation [52–54] and was recently licensed to Newron Pharmaceuticals for further testing in new indications [55]. …”