Pre-clinical assessment of DRF 4367, a novel COX-2 inhibitor: evaluation of pharmacokinetics, absolute oral bioavailability and metabolism in mice and comparative inter-species in vitro metabolism

Study on pharmacokinetics and tissue distribution of the isocorydine derivative (AICD) in rats by HPLC-DAD method

A simple and effective high-performance liquid chromatography with diode-array detection method coupled with a liquid-liquid extraction pretreatment has been developed for determining the pharmacokinetics and tissue distribution of a novel structurally modified derivative (8-acetamino-isocorydine) of isocorydine. According to the in vivo experiments data calculations by DAS 2.0 software, a two-compartment metabolic model was suitable for describing the pharmacokinetic of 8-acetamino-isocorydine in rats. 8-Acetamino-isocorydine was absorbed well after oral administration, and the absolute bioavailability was 76.5%. The half-life of 8-acetamino-isocorydine after intravenous and oral administration was 2.2 h and 2.0 h, respectively. In vivo, 8-acetamino-isocorydine was highly distributed in the lungs, kidney and liver; however, relatively little entered the brain, suggesting that 8-acetamino-isocorydine could not easily pass through the blood brain barrier. Our work describes the first characterization of the pharmacokinetic parameters and tissue distribution of 8-acetamino-isocorydine. The acquired data will provide useful information for the in vivo pharmacology of 8-acetamino-isocorydine, and can be applied to new drug research.

Preclinical pharmacokinetics, tissue distribution and excretion studies of a potential analgesics - corydaline using an ultra performance liquid chromatography-tandem mass spectrometry

A rapid resolution ultra performance liquid chromatography (UPLC) coupled with electrospray ionization (ESI) mass spectrometry method was developed and validated for the quantitative analysis of corydaline in rats' plasma and various tissues for pharmacokinetic, tissue distribution and excretion studies of corydaline. The analytes were separated on an Acquity UPLC BEH C18 column (2.1mm×100mm, 1.7μm) and detected with a triple quadrupole mass spectrometer using positive ion ESI in the multiple reaction monitoring (MRM) mode. The MS/MS ion transitions monitored were m/z 370.0→192.0 for corydaline and 354.1→188.0 for IS, respectively. Calibration curves (1/x(2) weighted) offered satisfactory linearity (r(2)>0.9984) within 1-1000ng/mL. The accuracy and precision ranged from -7.4% to 8.5% and 3.4% to 12.8%, respectively. The absolute matrix effect (94.2-119.2%), relative matrix effect (1.7-9.6%) and recoveries (81.4-93.7%) were satisfactory in all the biological matrices examined. The assay was successfully applied to the plasma pharmacokinetics, tissue distribution and excretion studies of corydaline in rats. The pharmacokinetic parameters such as half-life (t1/2), mean residence time (MRT) and maximum concentration (Cmax) were determined. These preclinical data of corydaline would be useful for the clinical reference.

Application of a liquid chromatography-tandem mass spectrometry method to the pharmacokinetics, tissue distribution and excretion studies of Dactylicapnos scandens in rats

The herbal ingredients of isocorydine and protopine were isolated from Dactylicapnos scandens. This study was aimed at developing a liquid chromatography-electrospray ionization-tandem mass spectrometry (LC-ESI-MS/MS) method to quantify isocorydine and protopine in rat plasma and tissues for pharmacokinetic, tissue distribution and excretion studies. Biological samples were processed with ethyl acetate extraction, and corydaline was chosen as the internal standard (IS). The analytes were separated by a C(18) column and detected with a triple quadrupole mass spectrometer using positive ion ESI in the multiple reaction monitoring (MRM) mode. The MS/MS ion transitions monitored were m/z 342.0→278.9 for isocorydine, 354.1→188.0 for protopine and 370.0→192.0 for IS, respectively. Excellent linearity was observed over the concentration range between 10 and 3000 ng/mL for isocorydine and 10-300 ng/mL for protopine. The lower limit of quantification (LLOQ) was 10 ng/mL for both isocorydine and protopine. This novel method was rapid, accurate, high sensitive and high selective. It was successfully applied to the pharmacokinetic, tissue distribution and excretion studies of D. scandens. These preclinical data of D. scandens would be useful for the clinical reference.

Glucuronidation of DRF-6574, hydroxy metabolite of DRF-4367 (a novel COX-2 inhibitor) by pooled human liver, intestinal microsomes and recombinant human UDP-glucuronosyltransferases (UGT): Role of UGT1A1,1A3 and 1A8

DRF-4367 is a novel COX-2 inhibitor, which showed good efficacy in several animal models of inflammation. In a comparative in vitro metabolism in various liver microsomes, DRF-4367 forms a hydroxy metabolite (DRF-6574) mediated by CYP2D6 and 2C19 isoenzymes. DRF-6574 readily undergoes Phase-II metabolism and forms glucuronide and sulfate conjugates both in vitro and in vivo. The objective of the present study was two folds: to study the glucuronidation of DRF-6574 in human liver and intestinal microsomes and to identify the recombinant human liver and intestinal UDP-glucuronosyltransferase (UGT) enzymes responsible for glucuronidation of DRF-6574. Of twelve recombinant UGTs tested, two hepatic UGTs viz., UGT1A1 and 1A3 and an extra hepatic UGT i.e., UGT1A8 showed the catalytic activity. The enzyme kinetics in pooled human liver, intestinal and recombinant UGT microsomes showed a typical Michaelis-Menten plot. The apparent Km and Vmax value for DRF-6574 was found to be 116 +/- 24 microM and 2.07 +/- 0.12 microg/min/mg protein and 142 +/- 17 microM and 3.83 +/- 0.15 microg/min/mg protein in pooled human liver and intestinal microsomes, respectively. The intrinsic clearance (Vmax/Km) value for DRF-6574 was estimated to be 0.043 and 0.065 ml/min/mg protein, respectively in pooled human liver and intestinal microsomes. Moreover we have determined the Km and Vmax and intrinsic clearance values for specific UGTs viz., UGT 1A1, 1A3 and 1A8. The apparent Km and Vmax values are 23 +/- 7.2 microM, 3.44 +/- 0.17 microg/min/mg protein for UGT1A1, 60 +/- 7.9 microM, 3.67 +/- 0.11 microg/min/mg protein for UGT1A3, 96 +/- 8.0 microM, 2.95 +/- 0.06 microg/min/mg protein for UGT1A8. The intrinsic clearance values (Vmax/Km) estimated were 0.367, 0.148, 0.074 ml/min/mg protein for UGT1A1, 1A3 and 1A8, respectively. The intrinsic clearance value in UGT1A8 was very close to that in human intestinal and liver microsomes. The formation of DRF-6574 glucuronide by human liver, intestinal and UGT1A1, 1A3 and 1A8 microsomes was effectively inhibited by phenylbutazone.

Identification of 2-hydroxymethyl-4-[5-(4-methoxyphenyl)-3-trifluoromethyl-pyrazol-1-yl]-N-propionylbenzenesulfonamide sodium as a potential COX-2 inhibitor for oral and parenteral administration

Synthesis of prodrugs of orally active COX-2 inhibitor 3 involving sulfamoyl (SO(2)NH(2)) and hydroxymethyl (CH(2)OH) groups, and their biological evaluation are described. Of these prodrugs, the N-propionyl sulfonamide sodium 3k was found to be much superior to the parent compound 3 and other marketed COX-2 inhibitors in carrageenan induced rat paw edema model of inflammation due to highly elevated drug levels in systemic circulation. This prodrug has a potential both for oral as well as parenteral administration due to impressive analgesic activity, antipyretic potency, and extraordinary water solubility.

N-Acylated sulfonamide sodium salt: A prodrug of choice for the bifunctional 2-hydroxymethyl-4-(5-phenyl-3-trifluoromethyl-pyrazol-1-yl) benzenesulfonamide class of COX-2 inhibitors

Synthesis and biological evaluation of possible prodrugs of COX-2 inhibitors involving sulfonamide and hydroxymethyl groups of 2-hydroxymethyl-4-(5-phenyl-3-trifluoromethyl-pyrazol-1-yl) benzenesulfonamides are described. Out of many options, the sodium salt of N-propionyl sulfonamide demonstrated much improved pharmacological profiles and physicochemical properties suitable for oral as well as parenteral administration.

In Vitro Inhibitory Effect of 1-Aminobenzotriazole on Drug Oxidations in Human Liver Microsomes: a Comparison with SKF-525A

1-Aminobenzotriazole (ABT) is extensively used as a non-specific cytochrome P450 (CYP) inhibitor. In this study, the inhibitory effect of ABT on CYP-dependent drug oxidations was investigated in human liver microsomes (HLM) and compared with that of SKF-525A, another non-specific inhibitor. The following probe activities for human CYP isoforms were determined using pooled HLM: phenacetin O-deethylation (CYP1A2); diclofenac 4'-hydroxylation (CYP2C9); S-mephenytoin 4'-hydroxylation, (CYP2C19); bufuralol 1'-hydroxylation (CYP2D6); chlorzoxazone 6-hydroxylation (CYP2E1); midazolam 1'-hydroxylation, nifedipine oxidation, and testosterone 6beta-hydroxylation (CYP3A). ABT had the strongest inhibitory effect on the CYP3A-dependent drug oxidations and the weakest effect on the diclofenac 4'-hydroxylation. SKF-525A potently inhibited the bufuralol 1'-hydroxylation, but weakly inhibited chlorzoxazone 6-hydroxylation. The inhibitory effects of ABT and SKF-525A were increased by preincubation in some probe reactions, and this preincubation effect was greater in ABT than in SKF-525A. The remarkable IC50 shift (> 10 times) by preincubation with ABT was observed on the phenacetin O-deethylation, chlorzoxazone 6-hydroxylation, and midazolam 1'-hydroxylation. In conclusion, ABT and SKF-525A had a wide range of IC50 values in inhibiting the drug oxidations by HLM with and without preincubation.