Publications (5)12.69 Total impact
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Article: In vitro studies on the metabolism of trabectedin (YONDELIS) in monkey and man, including human CYP reaction phenotyping.
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ABSTRACT: Trabectedin (YONDELIS) is a potent anticancer agent which was recently approved in Europe for the treatment of soft tissue sarcoma. The drug is currently also in clinical development for the treatment of ovarian carcinoma. In vitro experiments were conducted to investigate the hepatic metabolism of [(14)C]trabectedin in Cynomolgus monkey and human liver subcellular fractions. The biotransformation of trabectedin was qualitatively similar in 12,000 x g supernatants of both species, and all human metabolites were also produced by the monkey. The trabectedin metabolites were identified by QTOF mass spectrometry, and HPLC co-chromatography with reference compounds. Trabectedin was metabolized via different biotransformation pathways. Most of the metabolic conversions occurred at the trabectedin A domain including mono-oxidation and di-oxidation, carboxylic acid formation with and without additional oxidation, and demethylation either without (N-demethylation to ET-729) or with additional mono-, di- or tri-oxidation. Another metabolite resulted from O-demethylation at the trabectedin C subunit, and in addition, aliphatic ring opening of the methylene dioxybridge at the B domain was detected. Overall, demethylation and oxidation played a major role in phase I metabolism of the drug. Human cDNA expressed CYPs 1A2, 2A6, 2B6, 2C8, 2C9, 2C18, 2D6, 2E1, 3A4 and 3A5 in E. coli membranes, but not CYP1B1, 2C19, and 4A11 were able to metabolize [(14)C]trabectedin. Experiments with chemical inhibitors and CYP inhibitory antibodies indicated that, at therapeutic levels, CYP3A4 is the main human CYP isoform involved in trabectedin's hepatic metabolism. In monkey and human liver microsomes, trabectedin was not substantially metabolized by glucuronidation.Biochemical pharmacology 06/2009; 77(10):1642-54. · 4.25 Impact Factor -
Article: Effect of the fungicide imazalil on hepatic microsomal cytochrome P‐450 and cytochrome P‐450 dependent activities in the Bobwhite quail (Colinus virginianus)
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ABSTRACT: Bobwhite quails were treated with imazalil for 8 weeks. The fungicide was given admixed in the food at 0, 100, 300, 500 and 1000 mg kg−1. Even at the highest dose tested, imazalil did not affect the liver weight or the hepatic microsomal protein content. In treated quails, no significant induction of cytochrome P-450 or NADPH-cytochrome c-reductase activity was observed. Furthermore, imazalil did not induce or inhibit 7-ethoxyresorufin or 7-ethoxycoumarin O-deethylase in quail microsomes. Only a slight but significant increase by 35% and 49% in aniline hydroxylase activity was measured for the 500- and 1000-mg kg−1 dose levels, respectively. After a drug-free period of one week, aniline hydroxylase activity returned to control values, indicating that the effect was fully reversible. It is concluded that imazalil does not induce or inhibit drug-metabolizing enzymes in the quail, even at doses which exceed by far the maximum levels currently used to dress seed under field conditions (100 mg kg−1).Pesticide Science 05/2006; 29(1):47 - 56. -
Article: Expression and induction potential of cytochromes P450 in human cryopreserved hepatocytes.
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ABSTRACT: Fresh human hepatocytes are still considered as the "gold standard" to screen in vitro for cytochrome P450 (P450) induction. However, sparse availability of good quality human liver tissue for research purposes and the demand for standardized cell populations, together with the need for proper storage of the cells not immediately required, have resulted in the development of cryopreservation techniques that provide adequate viability and plateability of hepatocytes after thawing. This study aimed at validating cryopreserved human hepatocytes as a model to investigate P450 induction. Cryopreserved cells from four different donors were plated and cultured for 48 h, followed by incubation in the presence of typical P450 inducers. During the experiments, quality of the cultured cells was monitored both physiologically and morphologically. Concomitantly, the activity of CYP1A2, 2B6, 2C9, 2E1, and 3A4 was measured together with their mRNA and protein expression. Determination of CYP1A2, 2B6, 2C9, 2E1, and 3A4 activity in control versus prototypical inducer-treated hepatocytes revealed a maximal significant mean 11.6-, 2.8-, 1.9-, 1.5-, and 9.0-fold induction over their basal expression, respectively. Protein expression analysis of these P450s confirmed these results. Moreover, a mean 44.9-, 3.5-, 3.2-, and 13.8-fold induction of CYP1A2, 2B6, 2C9, and 3A4 mRNA was observed. Our data demonstrate that cryopreserved human hepatocytes are a valuable tool to study the induction of CYP1A2, 2B6, 2C9, 2E1, and 3A4.Drug Metabolism and Disposition 08/2005; 33(7):1004-16. · 3.73 Impact Factor -
Article: CYP2C8 polymorphisms in Caucasians and their relationship with paclitaxel 6alpha-hydroxylase activity in human liver microsomes.
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ABSTRACT: Published cDNA sequences suggest the existence of non-synonymous single nucleotide polymorphisms in the cytochrome P450 CYP2C8. To determine whether these polymorphisms could be confirmed in a Caucasian population and to investigate whether additional polymorphisms occur in the coding and upstream regions of this gene, we screened for previously described and for novel polymorphisms using PCR-RFLP and SSCP analysis. We confirmed the existence of two of the previously detected polymorphisms which give rise to the amino acid substitutions I264M and K399R, respectively, but failed to detect three others in our population. We also confirmed that a recently identified polymorphism (R139K) is linked to K399R (CYP2C8*3) in our study population. The allele frequencies for the I264M (CYP2C8*4 allele) and the CYP2C8*3 allele were 0.075 and 0.15, respectively. Three novel polymorphisms (T-370G, C-271A and T1196C/L390S) were also detected with the upstream polymorphisms showing allele frequencies of 0.061 and 0.196, respectively, but the L390S polymorphism detected only in a single subject. An additional single subject was heterozygous for a polymorphism recently described in African-Americans (A805T; CYP2C8*2 allele). The functional significance of the two upstream polymorphisms and the CYP2C8*3 and CYP2C8*4 alleles was investigated in human liver microsomes. Samples heterozygous for CYP2C8*3 showed significantly lower paclitaxel 6alpha-hydroxylase activity compared with wild-type samples. Median activity associated with CYP2C8*4 also appeared lower than the wild-type but the difference was not significant. There was no evidence that either upstream polymorphism gave rise to altered CYP2C8 expression.Biochemical Pharmacology 01/2003; 64(11):1579-89. · 4.70 Impact Factor -
Article: In vitro studies on the metabolism of trabectedin (YONDELIS®) in monkey and man, including human CYP reaction phenotyping
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ABSTRACT: In vitro studies on the metabolism of trabectedin (YONDELIS ®) in monkey and man, including human CYP reaction phenotyping, Biochemical Pharmacology (2008), This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
