PII-1Effects of β2 genetic polymorphisms on glucose dynamics during beta-blocker titration in heart...
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OV-A-3 GENETIC DETERMINANTS OF THE HEPATIC EXPRES- SION OF THE PHASE II CONJUGATING UGT1A3 ENZYME. B. Caillier, BSc, L. Villeneuve, MSc, O. Barbier, PhD, C. Guillemette, PhD, Laval University and CHUQ Research Center, Quebec, PQ, Canada. BACKGROUND/AIMS: UDP-glucuronosyltransferase UGT1A3 is significant for the glucuronic acid conjugation of a diversity of endo- and xenobiotics in the liver. Considering the variability in UGT1A3- mediated hepatic glucuronidation activity, this study was designed to identify common UGT1A3 genetic variants and determine their potential for contributing to interindividual differences. METHODS: Single nucleotide polymorphism (SNP) discovery was accomplished by resequencing DNA samples from healthy Cau- casians. Haplotypes were inferred and population frequencies esti- mated using PHASE version 2.1. For functional analysis, we used HepG2 cells in transfection studies with UGT1A3/luciferase con- structs and electromobility shift assays. RESULTS: Sequence analysis revealed six UGT1A3 upstream SNPs and 4 common (3-26%) promoter region haplotypes were inferred. One of the promoter variants fell within a putative binding factor site for the hepatocyte nuclear factor (HNF)-1 at -148 and is associated with a significant decrease in luciferase activity. The 148 TC variant significantly decreased by 50% the binding of the protein complex while the HNF1-specific antibody was able to supershift entirely the DNA-protein complex. CONCLUSION: UGT1A3 common promoter haplotype variants modulate gene function, namely through a reduction of the HNF1- mediated promoter activation, and might contribute to interindividual differences in UGT1A3-mediated glucuronidation. OV-A-4 INDUCTION OF CYTOCHROME P450 3A4 (CYP3A4) BY VINBLASTINE: ROLE OF THE NUCLEAR RECEPTOR NR1I2. N. F. Smith, S. Mani, H. Huang, S. E. Bates, W. D. Figg, A. Sparreboom, National Cancer Institute, Albert Einstein College of Medicine, Bethesda, MD. BACKGROUND: Metabolism of the anticancer agent vinblastine is mediated by CYP3A4. It has been demonstrated that other micro- tubule stabilizing agents such as paclitaxel are capable of inducing this enzyme via activation of NR1I2 (hPXR). Therefore, we evalu- ated the CYP3A4 induction potential of vinblastine both clinically and in vitro. METHODS: The pharmacokinetics of the CYP3A4 phenotyping probe midazolam (i.v. bolus, 0.0145 mg/kg) were determined in 6 patients with renal cell cancer undergoing treatment with vinblastine (72-h i.v. q4w) at baseline and in cycle 3. Midazolam plasma con- centrations were measured by LC/MS and clearance (CL) was de- rived using non-compartmental analysis. Protein expression of CYP3A4 and activation of hPXR by vinblastine were measured by Western blotting and a transactivation assay using transiently trans- fected HepG2 cells, respectively (Mani et al, Clin Cancer Res 11: 6359, 2005). RESULTS: Vinblastine increased midazolam CL on average by 60% (range, 2-317%; P0.0156, Wilcoxon test). In vitro, vinblastine at clinically-relevant concentrations induced CYP3A4 and the hPXR- ligand binding domain, but had only weak to no effect on full length hPXR, suggesting it is only a weak activator of hPXR. CONCLUSIONS: Vinblastine is able to induce CYP3A4 in vivo and thus has the potential to facilitate its own elimination and cause interactions with other CYP3A4 substrates. The mechanism of pro- tein induction is likely to be at the level of RNA stabilization or decreased protein turnover. PII-1 EFFECTS OF 2 GENETIC POLYMORPHISMS ON GLU- COSE DYNAMICS DURING BETA-BLOCKER TITRATION IN HEART FAILURE. K. I. Cheang, O. Vardeny, J. S. Zebrack, M. A. Munger, E. M. Gilbert, Virginia Commonwealth University, Univer- sity of Wisconsin, University of Utah, Richmond, VA. BACKGROUND: 2-adrenergic receptor (ADRB2) polymor- phisms affect 2-mediated glucose production by terbutaline. Whether beta-blockers’ effects on 2-mediated glucose production are affected by ADRB2 polymorphisms is unknown. This study determines the effect of ADRB2 Arg16Gly and Glu27Gln polymor- phisms on 2-mediated glucose dynamics during beta-blocker titra- tion in heart failure. METHODS: From a previous heart failure cohort whose meto- prolol or carvedilol were titrated to maximally tolerated doses (up to metoprolol 200mg/d or carvedilol 25mg twice daily) in 5 visits, we analyzed ADRB2 polymorphisms at codons 16 and 27, and glucose AUC0-180min upon a 2-agonist (terbutaline) infusion in nondia- betic individuals. RESULTS: Glucose AUC (mmol/Lx180 min) upon terbutaline infusion decreases as beta-blocker dosages increase (p0.0033, re- peated measure ANOVA). At baseline, subjects carrying a Glu allele at codon 27 demonstrated lower glucose AUC compared to individ- uals homozygous for Gln, although this difference was not signifi- cant. After maximal beta-blocker titration, glucose AUC decreased from 5.50.2 to 4.90.2 in subjects carrying a Glu allele at codon 27 versus from 6.30.4 to 5.50.4 in subjects homozygous for Gln (p0.0342, ANCOVA for comparisons between genotype groups). The ADRB2 Arg16Gly variant was not associated with differences in glucose values. CONCLUSIONS: ADRB2 polymorphisms may play a role in 2-mediated glucose production in heart failure patients taking beta- blockers. PII-2 EFFECTS OF BUPRENORPHINE TRANSDERMAL SYSTEM 10 MG. AND 2 20 MG. ON QT INTERVALS IN HEALTHY SUBJECTS. S. C. Harris, MD, D. Hoelscher, MD, A. Kristensen, MS, S. A. O’Keefe, BSN, A. Schemera, BA, Purdue Pharma, LP, PPD Development, Stamford, CT. AIM: Evaluate the effect of buprenorphine transdermal system (BTDS) 10 mg and 2 20 mg on QT/QTc intervals in healthy subjects, compared with placebo and oral moxifloxacin 400 mg. METHODS: Randomized, placebo- and positive-controlled, parallel-group, thorough QTc study in 132 healthy adults (18 to 55 years), BMI30 kg/m 2 , normal cardiac conduction, and resting heart rate 50-85 bpm. Safety was assessed with adverse event reports, clinical laboratory results, vital signs and SpO 2 , physical examina- tions, ECGs, and telemetry. RESULTS: BTDS 10 was not associated with a change in QTci. However, BTDS 2 20 (supratherapeutic dose) resulted in a pro- longation comparable to moxifloxacin 400 mg (Day 13). Mean (90% CI) changes from baseline in QTci over 24 hours compared with placebo were 7.6 (5.4, 9.9) and 5.9 (3.3, 8.4) for single 400 mg moxifloxacin doses on Days 6 and 13 respectively, and 0.4 (1.8, 2.6) and 5.9 (3.4, 8.4) for BTDS 10 and BTDS 2 20, respectively. No subjects had maximum QT/QTc intervals 480 msec, and no subject had increases in QTci 30 msec. Most common adverse events in BTDS group were nausea, head- ache, constipation, vomiting, and dizziness. No changes of potential clinical importance were observed in vital signs, ECGs (except QTc), or laboratory tests. CONCLUSIONS: BTDS 10 does not increase QTci in healthy subjects. BTDS 2 20 increases the QTci in healthy subjects by an amount comparable to 400 mg moxifloxacin. Most BTDS subjects were successfully titrated to the supratherapeutic dose of 2 x BTDS- 20. CLINICAL PHARMACOLOGY & THERAPEUTICS 2006;79(2) American Society for Clinical Pharmacology and Therapeutics P35
Transcript of PII-1Effects of β2 genetic polymorphisms on glucose dynamics during beta-blocker titration in heart...
OV-A-3GENETIC DETERMINANTS OF THE HEPATIC EXPRES-
SION OF THE PHASE II CONJUGATING UGT1A3 ENZYME. B.Caillier, BSc, L. Villeneuve, MSc, O. Barbier, PhD, C. Guillemette,PhD, Laval University and CHUQ Research Center, Quebec, PQ,Canada.
BACKGROUND/AIMS: UDP-glucuronosyltransferase UGT1A3 issignificant for the glucuronic acid conjugation of a diversity of endo- andxenobiotics in the liver. Considering the variability in UGT1A3-mediated hepatic glucuronidation activity, this study was designed toidentify common UGT1A3 genetic variants and determine their potentialfor contributing to interindividual differences.
METHODS: Single nucleotide polymorphism (SNP) discoverywas accomplished by resequencing DNA samples from healthy Cau-casians. Haplotypes were inferred and population frequencies esti-mated using PHASE version 2.1. For functional analysis, we usedHepG2 cells in transfection studies with UGT1A3/luciferase con-structs and electromobility shift assays.
RESULTS: Sequence analysis revealed six UGT1A3 upstreamSNPs and 4 common (3-26%) promoter region haplotypes wereinferred. One of the promoter variants fell within a putative bindingfactor site for the hepatocyte nuclear factor (HNF)-1� at -148 and isassociated with a significant decrease in luciferase activity. The �148T C variant significantly decreased by 50% the binding of theprotein complex while the HNF1�-specific antibody was able tosupershift entirely the DNA-protein complex.
CONCLUSION: UGT1A3 common promoter haplotype variantsmodulate gene function, namely through a reduction of the HNF1�-mediated promoter activation, and might contribute to interindividualdifferences in UGT1A3-mediated glucuronidation.
OV-A-4INDUCTION OF CYTOCHROME P450 3A4 (CYP3A4) BY
VINBLASTINE: ROLE OF THE NUCLEAR RECEPTOR NR1I2.N. F. Smith, S. Mani, H. Huang, S. E. Bates, W. D. Figg, A.Sparreboom, National Cancer Institute, Albert Einstein College ofMedicine, Bethesda, MD.
BACKGROUND: Metabolism of the anticancer agent vinblastineis mediated by CYP3A4. It has been demonstrated that other micro-tubule stabilizing agents such as paclitaxel are capable of inducingthis enzyme via activation of NR1I2 (hPXR). Therefore, we evalu-ated the CYP3A4 induction potential of vinblastine both clinicallyand in vitro.
METHODS: The pharmacokinetics of the CYP3A4 phenotypingprobe midazolam (i.v. bolus, 0.0145 mg/kg) were determined in 6patients with renal cell cancer undergoing treatment with vinblastine(72-h i.v. q4w) at baseline and in cycle 3. Midazolam plasma con-centrations were measured by LC/MS and clearance (CL) was de-rived using non-compartmental analysis. Protein expression ofCYP3A4 and activation of hPXR by vinblastine were measured byWestern blotting and a transactivation assay using transiently trans-fected HepG2 cells, respectively (Mani et al, Clin Cancer Res 11:6359, 2005).
RESULTS: Vinblastine increased midazolam CL on average by60% (range, 2-317%; P�0.0156, Wilcoxon test). In vitro, vinblastineat clinically-relevant concentrations induced CYP3A4 and the hPXR-ligand binding domain, but had only weak to no effect on full lengthhPXR, suggesting it is only a weak activator of hPXR.
CONCLUSIONS: Vinblastine is able to induce CYP3A4 in vivoand thus has the potential to facilitate its own elimination and causeinteractions with other CYP3A4 substrates. The mechanism of pro-tein induction is likely to be at the level of RNA stabilization ordecreased protein turnover.
PII-1EFFECTS OF �2 GENETIC POLYMORPHISMS ON GLU-
COSE DYNAMICS DURING BETA-BLOCKER TITRATION INHEART FAILURE. K. I. Cheang, O. Vardeny, J. S. Zebrack, M. A.Munger, E. M. Gilbert, Virginia Commonwealth University, Univer-sity of Wisconsin, University of Utah, Richmond, VA.
BACKGROUND: �2-adrenergic receptor (ADRB2) polymor-phisms affect �2-mediated glucose production by terbutaline.Whether beta-blockers’ effects on �2-mediated glucose productionare affected by ADRB2 polymorphisms is unknown. This studydetermines the effect of ADRB2 Arg16Gly and Glu27Gln polymor-phisms on �2-mediated glucose dynamics during beta-blocker titra-tion in heart failure.
METHODS: From a previous heart failure cohort whose meto-prolol or carvedilol were titrated to maximally tolerated doses (up tometoprolol 200mg/d or carvedilol 25mg twice daily) in 5 visits, weanalyzed ADRB2 polymorphisms at codons 16 and 27, and glucoseAUC0-180min upon a �2-agonist (terbutaline) infusion in nondia-betic individuals.
RESULTS: Glucose AUC (mmol/Lx180 min) upon terbutalineinfusion decreases as beta-blocker dosages increase (p�0.0033, re-peated measure ANOVA). At baseline, subjects carrying a Glu alleleat codon 27 demonstrated lower glucose AUC compared to individ-uals homozygous for Gln, although this difference was not signifi-cant. After maximal beta-blocker titration, glucose AUC decreasedfrom 5.5�0.2 to 4.9�0.2 in subjects carrying a Glu allele at codon 27versus from 6.3�0.4 to 5.5�0.4 in subjects homozygous for Gln(p�0.0342, ANCOVA for comparisons between genotype groups).The ADRB2 Arg16Gly variant was not associated with differences inglucose values.
CONCLUSIONS: ADRB2 polymorphisms may play a role in�2-mediated glucose production in heart failure patients taking beta-blockers.
PII-2EFFECTS OF BUPRENORPHINE TRANSDERMAL SYSTEM
10 MG. AND 2 � 20 MG. ON QT INTERVALS IN HEALTHYSUBJECTS. S. C. Harris, MD, D. Hoelscher, MD, A. Kristensen,MS, S. A. O’Keefe, BSN, A. Schemera, BA, Purdue Pharma, LP,PPD Development, Stamford, CT.
AIM: Evaluate the effect of buprenorphine transdermal system(BTDS) 10 mg and 2 � 20 mg on QT/QTc intervals in healthysubjects, compared with placebo and oral moxifloxacin 400 mg.
METHODS: Randomized, placebo- and positive-controlled,parallel-group, thorough QTc study in 132 healthy adults (18 to 55years), BMI�30 kg/m2, normal cardiac conduction, and resting heartrate 50-85 bpm. Safety was assessed with adverse event reports,clinical laboratory results, vital signs and SpO2, physical examina-tions, ECGs, and telemetry.
RESULTS: BTDS 10 was not associated with a change in QTci.However, BTDS 2 � 20 (supratherapeutic dose) resulted in a pro-longation comparable to moxifloxacin 400 mg (Day 13). Mean (90%CI) changes from baseline in QTci over 24 hours compared withplacebo were 7.6 (5.4, 9.9) and 5.9 (3.3, 8.4) for single 400 mgmoxifloxacin doses on Days 6 and 13 respectively, and 0.4 (�1.8,2.6) and 5.9 (3.4, 8.4) for BTDS 10 and BTDS 2 � 20, respectively.No subjects had maximum QT/QTc intervals �480 msec, and nosubject had increases in QTci �30 msec.
Most common adverse events in BTDS group were nausea, head-ache, constipation, vomiting, and dizziness. No changes of potentialclinical importance were observed in vital signs, ECGs (except QTc),or laboratory tests.
CONCLUSIONS: BTDS 10 does not increase QTci in healthysubjects. BTDS 2 � 20 increases the QTci in healthy subjects by anamount comparable to 400 mg moxifloxacin. Most BTDS subjectswere successfully titrated to the supratherapeutic dose of 2 x BTDS-20.
CLINICAL PHARMACOLOGY & THERAPEUTICS2006;79(2) American Society for Clinical Pharmacology and Therapeutics P35
