(+)- N -3-Benzyl-Nirvanol and (−)- N -3-Benzyl-Phenobarbital: New Potent and Selective in Vitro Inhibitors of CYP2C19

ABSTRACT:Various groups have sought to determine the impact of CYP2C8 genotype (and CYP2C8 inhibition) on the pharmacokinetics (PK) of ibuprofen (IBU) enantiomers. However, the contribution of cytochrome P450 2C8 (CYP2C8) in human liver microsomes (HLMs) has not been reported. Therefore, in vitro cytochrome P450 (P450) reaction phenotyping was conducted with selective inhibitors of cytochrome P450 2C9 (CYP2C9) and CYP2C8. In the presence of HLMs, sulfaphenazole (CYP2C9 inhibitor), and anti-CYP2C9 monoclonal antibodies (mAbs) inhibited (73-100%) the 2-and 3-hydroxylation of both IBU enantiomers (1 and 20 M). At a higher IBU concentration (500 M), the same inhibitors were less able to inhibit the 2-hydroxylation of There has been continued interest in the safety and ADME properties of cyclooxygenase inhibitors. This interest has extended to 2-(4-isobutylphenyl)propionic acid (ibuprofen, IBU), which is administered as a racemic mixture of (S)-(ϩ)-and (R)-(Ϫ)-enantiomers (Rodrigues, 2005;Agúndez et al., 2007;Pilotto et al., 2007;Blanco et al., 2008). The metabolism of both enantiomers is complex and involves direct (acyl) glucuronidation, 2-hydroxylation, and 3-hydroxylation (methyl hydroxylation) (Fig. 1). Once formed, the 3-hydroxy metabolite is converted almost completely to the corresponding carboxy derivative via cytosolic dehydrogenases (Rudy et al., 1991;Hamman et al., 1997;Davies, 1998). Only (R)-(Ϫ)-IBU undergoes (unidirectional) chiral inversion, which is significant because pharmacological activity after a racemic dose is attributed largely to the (S)-(ϩ)-enantiomer (Davies, 1998;Hao et al., 2005;Ding et al., 2007). Overall, it seems that P450-dependent metabolism accounts for approximately 70 and 30% of (S)-(ϩ)-IBU and (R)-(Ϫ)-IBU clearance, respectively (Rodrigues, 2005). At first glance, the pharmacokinetic profile of the latter is expected to be minimally affected by P450 inhibitors and genotype (e.g., CYP2C9*1/*3, CYP2C9*3/*3; CYP2C8*1/*3, CYP2C8*3/*3). (S)-(؉)-IBU (32-52%) and (R)-(؊)-IBU (30-64%), whereas the 3-hydroxylation of (S)-(؉)-IBU and (R)-(؊)-Currently available in vitro data show that CYP2C9 plays a major role (Ͼ70%) in the oxidative metabolism of racemic IBU and its individual enantiomers. However, hydroxylation of both enantiomers has also been measured with rCYP2C8 and other P450s (CYP3A4 and CYP2C19) (Leeman et al., 1993;Hamman et al., 1997;McGinnity et al., 2000). Such data have led various groups to conclude that both CYP2C forms catalyze the oxidative metabolism of IBU, and attempts have been made to evaluate the impact of both CYP2C9 and CYP2C8 genotype on the PK, pharmacodynamics, and side-effect profile of IBU enantiomers (Kirchheiner et al., 2002;Garcia-Martin et al., 2004; Martinez et al., 2005;Pilotto et al., 2007;Blanco et al., 2008). Clinical drug interaction studies with known inhibitors of CYP2C9 (e.g., fluconazole) and CYP2C8 (e.g., gemfibrozil) have been conducted also (Hynninen et al., 2006;Tornio et al., 2007).However, it is worth noting that CYP2C8-selective chemica...

Section: Resultsmentioning

confidence: 94%

Confirmation That Cytochrome P450 2C8 (CYP2C8) Plays a Minor Role in (S)-(+)- and (R)-(-)-Ibuprofen Hydroxylation in Vitro

Chang¹,

Li²,

Traeger³

et al. 2008

“…Inhibition studies with two concentrations of P450-selective reference inhibitors were carried out at a final nabumetone concentration of 50 M. Inhibitor concentrations were selected based on previous experience of selectivity (lower concentration) and potency (higher concentration) (Suzuki et al, 2002;Turpeinen et al, 2005;Pelkonen et al, 2008). Reference inhibitors furafylline (1 and 10 M; CYP1A2), tranylcypromine (0.5 and 5 M; CYP2A6), ticlopidine (0.1 and 1 M; CYP2B6), montelukast (0.1 and 1 M; CYP2C8), sulfaphenazole (1 and 10 M; CYP2C9), (ϩ)-N-3-benzyl-nirvanol (1 and 10 M; CYP2C19), quinidine (1 and 10 M; CYP2D6), pyridine (5 and 50 M; CYP2E1), and ketoconazole (0.5 and 5 M; CYP3A4) were added into the incubation mixture in a small volume (0.5% v/v) of an appropriate solvent (water, methanol, ACN, or dimethyl sulfoxide), and incubations were carried out as described under Incubations Using HLMs.…”

Section: Turpeinen Et Almentioning

confidence: 99%

A Predominate Role of CYP1A2 for the Metabolism of Nabumetone to the Active Metabolite, 6-Methoxy-2-naphthylacetic Acid, in Human Liver Microsomes

Turpeinen¹,

Hofmann²,

Klein³

et al. 2009

ABSTRACT:Nabumetone, a widely used nonsteroidal anti-inflammatory drug, requires biotransformation into 6-methoxy-2-naphthylacetic acid (6-MNA), a close structural analog to naproxen, to achieve its analgesic and anti-inflammatory effects. Despite its wide use, the enzymes involved in metabolism have not been identified. In the present study, several in vitro approaches were used to identify the cytochrome P450 (P450) enzyme (

“…In another series of assays, we examined the effects on olomoucine II metabolite formation of the following specific inhibitors of CYP1A2, CYP2C9, CYP3A4, CYP2E1, CYP2D6, CYP2A6, CYP2B6, and CYP2C19 activity: 22.5 M furafylline, 3 M sulfaphenazole, 2 M ketoconazole, 75 M diethyldithiocarbamate, 0.3 M quinidine, 1 M 8-methoxypsoralen, 2 M 7-pentoxyresorufin, and 1 M S-benzylnirvanol, respectively (Goldstein et al, 1994;Baldwin et al, 1995;Newton et al, 1995;Dierks et al, 2001;Suzuki et al, 2002). In these experiments, each of the inhibitors was preincubated with the P450-containing reaction mixture (see Metabolite formation and its inhibition by carbon monoxide) before addition of olomoucine II to a final concentration of 25 M.…”

Section: Methodsmentioning

confidence: 99%

Interactions of Olomoucine II with Human Liver Microsomal Cytochromes P450

Siller

Anzenbacher²,

Anzenbacherová³

et al. 2009

ABSTRACT:Olomoucine II is a cyclin-dependent kinase inhibitor and a potential antineoplastic agent because it can arrest animal cell cycles. This study examines its interactions with human liver microsomal cytochrome P450 (P450) enzymes. Spectroscopic and high-performance liquid chromatography (HPLC) methods were used to estimate the degree of olomoucine II-mediated inhibition of enzymatic activities of eight drug-metabolizing P450s in vitro. In addition, mass spectrometry coupled with HPLC was used to identify an olomoucine II metabolite (2,5-dihydroxyroscovitine) formed in the reaction mixtures, and CYP3A4 was found to be responsible for the hydroxylation of the N 6 -benzyl ring at position 5, leading to this compound. Olomoucine II significantly inhibited the enzymatic activities of CYP1A2, CYP2C9, and (to a lesser degree) CYP3A4. The results indicate that use of olomoucine II as a drug could affect the activities of CYP3A4, CYP1A2, and CYP2C9 in vivo. Hence, the clinical relevance of these interactions should be carefully evaluated.