Cyp2d6 Catalyzes 5-Hydroxylation of 1-(2-Pyrimidinyl)-Piperazine, an Active Metabolite of Several Psychoactive Drugs, in Human Liver Microsomes

Abstract

ABSTRACT:1-(2-Pyrimidinyl)-piperazine (1-PP) is an active metabolite of several psychoactive drugs including buspirone. 1-PP is also the major metabolite in the human circulation and in rat brains following oral administration of buspirone. This study was conducted to identify the enzyme responsible for the metabolic conversion of 1-PP to 5-hydroxy-1-(2-pyrimidinyl)-piperazine (HO-1-PP) in human liver microsomes (HLMs). The product HO-1-PP was quantified by a validated liquid chromatography-tandem mass spectrometry method. In the presence of NADPH, 1-PP (100 M) was incubated separately with human cDNA-expressed cytochrome P450 isozymes (including CYP2D6, 3A4, 1A2, 2A6, 2C9, 2C19, 2E1, and 2B6) at 37°C. CYP2D6 catalyzed the formation of HO-1-PP from 1-PP. This catalytic activity was >95% inhibited by quinidine, a CYP2D6 inhibitor. HO-1-PP formation rates correlated well with the bufuralol 1-hydroxylase (CYP2D6) activities of individual HLMs. The formation of HO-1-PP followed a Michaelis-Menten kinetics with a K m of 171 M and V max of 313 pmol/min ⅐ mg protein in HLMs. Collectively, these results indicate that polymorphic CYP2D6 is responsible for the conversion of 1-PP to HO-1-PP.1-(2-Pyrimidinyl)-piperazine (1-PP) is a major active metabolite resulting from the N-dealkylation of several antidepressant/anxiolytic 5-HT 1A agonists including tandospirone, gepirone, ipsapirone, and buspirone (Caccia et al., 1985(Caccia et al., , 1986Koenig et al., 1988). 1-PP is up to 20% as active as buspirone in in vitro pharmacological models for buspirone and in in vivo anxiolytic and ␣ 2 -adrenoceptor antagonist activity (Garattini et al., 1982;Caccia et al., 1986;Berlin et al., 1995). In addition, 1-PP has an affinity for ␣ 2 -adrenergic receptor with K d ϭ 40 nM and for 5-HT 1A with K d ϭ 1035 nM (Zuideveld et al., 2002). 1-PP was a partial agonist for 5-HT 1A and an antagonist for the ␣ 2 -adrenergic receptor and induced hyperthermic response in rats (Komissarev et al., 1990). The concentration of 1-PP in rat brain after oral administration of buspirone was 15 to 30 times higher than the concentration of buspirone (Gammans et al., 1983). The human plasma levels of 1-PP (ng/ml) were approximately 4-fold higher than that of buspirone after a 20-mg effective oral dose of buspirone. Elimination of 1-PP appeared to be much slower than that of buspirone in humans (Goldberg and Finnerty, 1979;Gammans et al., 1986).Metabolism of buspirone in humans has been reported (Jajoo et al., 1989). Following administration of a 20-mg oral dose in humans, 60% of the dose was excreted in urine. HO-1-PP represented a major urinary metabolite (7-19% of the dose). 1-PP accounted for approximately 5% of the dose in the urine. No glucuronide or sulfate conjugation metabolites of 1-PP were reported in the human urine. HO-1-PP could result from hydroxylation of 1-PP or N-dealkylation of metabolites that have a hydroxyl group at the 5-position (e.g., 5-hydroxybuspirone). Both HO-1-PP and 5-hydroxybuspirone were major circulating metabolites with a mola...

N-Dealkylation of Arylpiperazine Derivatives: Disposition and Metabolism of the 1-Aryl-Piperazines Formed

“…p-Hydroxy-PmP and its conjugates were identified in urine of man and animals given buspirone, indicating that PmP derived from the N-dealkylation of its parent drugs and other intermediates also undergoes oxidation and conjugation before excretion [70]. In contrast BITP is further oxidized at sulfur, with quantitative differences in the amounts of sulfoxide and sulfone derivatives excreted in man and rats given ziprasidone [31].…”

“…Correlation studies with isoform activities in human microsomes and metabolism by recombinant human CYP enzymes indicated that polymorphic CYP2D6 is responsible for the aromatic hydroxylation of mClPP [71], mCF 3 PP [72], and PmP [70]. This was supported by studies with CYP isoform-selective chemical inhibitors which showed that quinidine strongly reduced the formation rate of their hydroxylated derivative, from about 77% for mCF 3 PP to more than 95% for PmP in human liver microsomes and cDNA-expressed CYP2D6 or both [70][71][72].…”

Die Erschließung von Wirkstoffmetaboliten durch übergangsmetallkatalysierte C‐H‐Oxidation: die Leber als Inspiration für die Synthese

“…Diese Methoden sind außergewöhnlich gut für die Anwendung an Pharmazeutika geeignet, da sie eine beeindruckende Toleranz gegenüber funktionellen Gruppen haben; einige Beispiele sind im Folgenden veranschaulicht. 2‐(Piperazin‐1‐yl)pyrimidin‐5‐ol ( 105 ) ist ein Metabolit von verschiedenen im Markt befindlichen Antidepressiva wie Buspiron ( 2 ), Tandospiron, Gepiron und Ipsapiron . Die Verbindung wird in vivo durch N‐Dealkylierung gebildet.…”

Antidepressant potential of nitrogen-containing heterocyclic moieties: An updated review

“…[62] 1-(2-Pyrimidinyl)-piperazine is a major active metabolite of tandospirone, gepirone, ipsapirone, and buspirone which also have antidepressant/anxiolytic 5-HT 1A agonists′ activity. [63] The pharmaceutical importance of this nucleus is due to extensive occurrence in current marketed drug. [64] Various antidepressant drugs have a piperazine nucleus such as Amoxapine, Befuraline, Binospirone, Alnespirone, Buspirone, Flesinoxan, Gepirone, Ipsapirone, Nefazodone, Piberaline, and Tandospirone.…”