UGT Genotypes Research Articles

Effect of UGT1A4, UGT2B7, UGT2B15, UGT2B17 and ABC1B polymorphisms on lamotrigine metabolism in Danish patients

ObjectiveTo evaluate the impact of genetic polymorphisms of UGT enzymes (UGT1A4, UGT2B7, UGT2B15 and UGT 2B17) and the transporter protein ABCB1 on Lamotrigine (LTG) metabolism. MethodsSingle nucleotide polymorphisms UGT1A4*2 (P24T, c.70C>A), UGT1A4*3 (L48V c.142T>G), UGT2B7*2 (H802Y, c.802C>T), UGT2B15*2 (Y85D, c.253G>T), UGT2B17 deletion and transporters ABC 1236C> T and 3435C> T were determined in 337 Caucasian patients with epilepsy treated with LTG in Denmark. The prospectively collected data included LTG dosage, LTG plasma concentration, 2-N-GLU concentration, sex, smoking habits, concomitant medicine, oral contraceptives (OC). ResultsThe non-smokers with LTG monotherapy and LTG polytherapy with other non-interacting drugs NIAEDs (n = 199) were analyzed separately in univariant analyses. LTG ratios (LTG plasma concentration/ (LTG dose/weight)) in patients carrying wild type UGT1A4*2 C-allele were 22% lower than in heterozygous C-carriers (p = 0.013). Patients with UGT2B7*2 polymorphism TT genotype had 1.2-fold higher LTG ratios (p = 0.0078) and 0.78-fold lower GLU/LTG ratio (p = 0.0275) than patients homozygous for the C allele. The similar significant findings were also seen comparing homozygotes (TT) with heterozygotes patients (CT). Individuals homozygous for the UGT2B15*2 T allele displayed 18% lower LTG ratio concentrations than individuals homozygous for the G allele (p = 0.014),while significant difference in GLU/LTG ratio was only seen comparing wild type with homozygous patients (GG versus TT, p = 0.031). A copy number variation gene deletion polymorphism of UGT2B17 showed that individuals devoid of the gene (del/del) exhibited 1.3-fold higher LTG ratio (p = 0.015). For ABCB1c.1236 C>T and ABC1B1c.3435 C>T no associations with LTG and GLU ratios were found.Sex specific differences in enzyme activity (most prominent effect in women) on LTG metabolism were found for UGT2B15, UGT2B17, UGT1A4 and UGT2B7 polymorphisms.Multiple regression analysis confirmed the significant effect of OC, VPA and UGT1A4 * 2 and UGT2B7 * 2 on LTG metabolism. ConclusionOur study confirms the previous findings that genetic variations in UGT2B7 and UGT1A4 genes are associated with serum LTG concentrations.Furthermore, our results indicate that it is possible that different UGT genotypes may exert larger impact on LTG metabolism in women than in men.

Effect of race and glucuronidation rates on the relationship between nicotine metabolite ratio and nicotine clearance.

To investigate if the nicotine metabolite ratio (NMR, the ratio of nicotine metabolites 3'-hydroxycotinine/cotinine) is a reliable phenotypic biomarker for nicotine clearance across races, and as a function of differences in the rate of nicotine, cotinine and 3'-hydroxycotinine glucuronidation and UGT genotypes. Participants [Caucasians (Whites), African Americans (Blacks) and Asian-Americans (Asians)] received an oral solution of deuterium-labeled nicotine and its metabolite cotinine. Plasma and saliva concentrations of nicotine and cotinine were used to determine oral clearances. Rates of glucuronidation were assessed from urine glucuronide/parent ratios, and UGT2B10 and UGT2B17 genotypes from DNA. Among the 227 participants, 96 (42%) were White, 67 (30%) Asian and 64 (28%) Black. Compared to the other two races, Whites had higher nicotine and cotinine total oral clearance, Blacks had lower nicotine and cotinine glucuronidation rates and Asians had lower 3'-hydroxycotinine glucuronidation rates. A strong positive correlation (correlations coefficients 0.77-0.84; P < 0.001) between NMR and nicotine oral clearance was found for all three races, and NMR remained a strong predictor for the nicotine oral clearance while adjusting for race, sex and age. Neither the metabolite glucuronidation ratios nor the UGT genotypes had significant effects on the ability of NMR to predict nicotine oral clearance. NMR appears to be a reliable phenotypic biomarker for nicotine clearance across races, glucuronidation phenotypes and genotypes. Racial differences in the relationships between NMR, smoking behaviors and addiction are unlikely to be related to an inadequate estimation of nicotine clearance on the basis of NMR.

UGT1A6 and UGT2B7 Gene Polymorphism and its Effect in Pediatric Epileptic Patients on Sodium Valproate Monotherapy

To evaluate the pattern of UGT1A6 and UGT2B7 gene polymorphism in pediatric epileptic patients and to compare the sodium valproate concentration in different patterns of UGT gene polymorphism. In this cross-sectional study, 99 pediatric epileptic patients aged 2-18 y receiving Sodium valproate monotherapy for the past one month were included from JusticeK S Hegde Charitable hospital, Mangalore after obtaining informed consent. Genetic polymorphism patterns were evaluated by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP). Trough level serum valproate concentration was estimated by high-performance liquid chromatography (HPLC). Sodium valproate concentration in different UGT genotypes was compared by Analysis of Variance (ANOVA). P value <0.05 was considered significant. In the present study population, the predominant mutant allele pattern was observed in UGT1A6 (T19G, A541G, A552C) gene. In UGT2B7 (A268G, C161T) showed predominant mutant allele pattern while (G211T) showed predominant wild type. Mean steady-state sodium valproate concentration was 105.40 ± 49.9μg/ml and adjusted sodium valproate concentration was 5.5± 3.2mg/kg/L. It was found that there was no statistical difference in sodium valproate concentration in different UGT1A6 and UGT2B7 gene polymorphism. The present study concluded that though there was a difference in pattern of gene polymorphism with concerning UGT1A6 and UGT2B7, however, it has not contributed to variation in serum concentration of sodium valproate in the present study population.

Impacts of the Glucuronidase Genotypes UGT1A4, UGT2B7, UGT2B15 and UGT2B17 on Tamoxifen Metabolism in Breast Cancer Patients.

Tamoxifen is used to prevent and treat estrogen-dependent breast cancer. It is described as a prodrug since most of its antiestrogen effects are exerted through its hydroxylated metabolites 4-OH-tamoxifen and endoxifen. In prior work, we correlated optimal plasma levels of these metabolites with certain genotypes of CYP2D6 and SULT1A2. This descriptive study examines correlations between concentrations of tamoxifen's glucuronide metabolites and genotypes UGT1A4 Pro24Thr, UGT1A4 Leu48Val, UGT2B7 His268Tyr, UGT2B15 Asp85YTyr UGT2B15 Lys523Thr and UGT2B17del in 132 patients with estrogen receptor-positive breast cancer under treatment with tamoxifen. Patients were genotyped by real-time and conventional PCR-RFLP. The glucuronides 4-OH-tamoxifen-N-glucuronide, 4-OH-tamoxifen-O-glucuronide and endoxifen-O-glucuronide were isolated from blood plasma and quantified using a high-pressure liquid chromatography-tandem mass spectrometry system. Individuals who were homozygous for UGT1A448VAL showed significantly lower mean concentrations of both glucuronide metabolites compared to subjects genotyped as wt/wt plus wt/48Val (p=0.037 and p=0.031, respectively). Women homozygous for UGT2B7268Tyr also showed mean substrate/product ratios of 4-OH-tamoxifen/4-OH-tamoxifen-O-glucuronide and 4-OH-tamoxifen/4-OH-tamoxifen-N-glucuronide indicative of reduced glucuronidase activity compared to wt homozygotes or to heterozygotes for the polymorphism (p=0.005 and p=0.003, respectively). In contrast, UGT2B15 Lys523Thr and UGT2B17del were associated with possibly increased enzyme activity. Patients with at least one variant allele UGT2B15523Thr showed significantly higher 4-OH-tamoxifen-O-glucuronide and endoxifen-glucuronide levels (p=0.023 and p=0.025, respectively) indicating a variant gene-dose effect. Higher 4-OH-tamoxifen-N-glucuronide levels observed in UGT2B17del genotypes (p=0.042) could be attributed to a mechanism that compensates for the greater expression of other genes in UGT2B17 del/del individuals. Our observations suggest that patients carrying mutations UGT1A448Val, UGT2B7268Tyr or with wt genotypes for UGT2B17nodel and UGT2B15523Lys could be the best candidates for a good response to tamoxifen therapy in terms of eliciting effective plasma active tamoxifen metabolite levels. However, additional studies examining the effects of UGT genotype on overall patient response to TAM are needed to further examine the role of UGT polymorphisms in the therapeutic efficacy of TAM.

Association of UGT1A1 (*28, *60 and * 93) polymorphism with the adverse reactions of irinotecan chemotherapy in extensive stage small cell lung cancer

To explore the correlation between UGT1A1 (*28, *60 and * 93) polymorphism and the adverse reactions in small cell lung cancer patients after irinotecan chemotherapy. Clinical data of 58 small cell lung cancer patients in extensive stage treated in our hospital were retrospectively analyzed. Polymerase chain reaction was used to amplify the UTG, and direct sequencing was performed to determine the UGT polymorphism. The adverse reactions ≥ grade 3 after irinotecan chemotherapy in patients with different UGT genotype were analyzed. Amongthe 58 patients with extensive stage small cell lung cancer, there were 45 (77.6%) cases of wild type UGT1A1*28, 40 (69.0%) cases of wild type UGT1A1* 93, 38 (65.5%) cases of wild type UGT1A1*60, 18 cases of mutation in UGT1A1* 93 and 20 cases of mutation in UGT1A1*60. In UGT1A1 promoter position 28, there were 8 (13.8%) cases of TA5 mutation and 5 (8.6%) cases of TA7 mutation. Among the patients with TA5 mutation, 5 cases had ≥ grade 3 diarrhea, 3 cases had ≥ grade 3 leucopenia and 3 cases had ≥ grade 3 neutropenia, while among the patients with UGT1A1 * 93 mutation, 7 cases had ≥ grade 3 diarrhea, 6 cases had ≥ grade 3 leucopenia and 4 cases had ≥ grade 3 neutropenia. TA5 and UGT1A1* 93 mutation increase the risk of diarrhea and ≥ grade 3 leukopenia and neutropenia, however, wild type UGT1A1 (*28, * 93, *60) and mutant UGT1A1*60 do not increase those risks. Further prospective study in a larger number of patients is needed to clarify the association between UGT1A1*28, UGT1A1* 93 and UGT1A1*60 polymorphism and adverse reactions of irinotecan, and to help clinicians in choosing a better therapeutic modality for personalized chemotherapy to improve curative effect and reduce adverse reactions.

Abstract 2203: Characterization of raloxifene glucuronidation and the role of UGT genotypes on raloxifene metabolite profiles in vivo.

Abstract Raloxifene is a 2nd-generation selective estrogen receptor modulator used for the prevention and treatment of osteoporosis and the prevention of breast cancer in postmenopausal women. Raloxifene is extensively metabolized by glucuronidation to form raloxifene-6-glucuronide (ral-6-Gluc) and raloxifene-4’-glucuronide (ral-4’-Gluc). The goal of the present study was to determine whether functional polymorphisms in active UGTs could play a role in altered raloxifene glucuronidation in vivo. Using homogenates from HEK293 UGT-overexpressing cell lines, raloxifene was shown to be glucuronidated primarily by the hepatic UGTs 1A1 and 1A9 and the extra-hepatic UGTs 1A8 and 1A10; no detectable raloxifene glucuronidation activity was found for UGT2B enzymes. Functional UGT1A1 transcriptional promoter genotypes were significantly (ptrend=0.005) associated with ral-6-Gluc formation in human liver microsomes, and, consistent with the decreased raloxifene glucuronidation activities observed in vitro with cell line over-expressing UGT1A8 variants, the UGT1A8*2 variant was significantly (p=0.023) correlated with total raloxifene glucuronide formation in human jejunum homogenates. While ral-4’-Gluc exhibited 1/100th the anti-estrogenic activity of raloxifene itself as measured by binding to the estrogen receptor, raloxifene glucuronides comprised ∼99% of the circulating raloxifene dose in raloxifene-treated subjects, with ral-4’-Gluc comprising ∼70% of raloxifene glucuronides. Plasma ral-6-Gluc (ptrend=0.0025), ral-4’-Gluc (ptrend=0.001), and total raloxifene glucuronides (ptrend=0.001) were increased in raloxifene-treated subjects who were predicted slow metabolizers [UGT1A8 (*1/*3)] vs intermediate metabolizers [UGT1A8 (*1/*1) or UGT1A8 (*1/*2)] vs fast metabolizers [UGT1A8 (*2/*2). These data suggest that raloxifene metabolism may be dependent on UGT1A8 genotype and that UGT1A8 genotype may play an important role in overall response to raloxifene. Citation Format: Dongxiao Sun, Nathan R. Jones, Manni Andrea, Philip Lazarus. Characterization of raloxifene glucuronidation and the role of UGT genotypes on raloxifene metabolite profiles in vivo. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 2203. doi:10.1158/1538-7445.AM2013-2203

Su1843 High Enzyme Activity UGT1A1 or Low Activity Ugt1a8 and Ugt2b4 Genotypes Increase Esophageal Cancer Risk

Esophageal cancer (EC) has a globally increasing incidence with poor curative treatment options and survival rates. Environmental and dietary factors have crucial roles in esophageal carcinogenesis. Polymorphisms in the UGT genes, a superfamily of enzymes essential for the detoxification of carcinogens, may alter enzyme activity and subsequently may play a role in EC etiology. Rather than solely estab- lishing differences in genotype distribution, we investigated whether functional polymorphisms in UGT genes that can predict enzyme activity in vivo, may influence EC risk. A case-control study including 351 Caucasian EC patients and 592 Caucasian controls was conducted and polymorphisms in seven UGT genes were determined, using the polymerase chain reaction. On the basis of allelic in vitro enzyme activity measurements, genotypes were categorized according to their predicted in vivo enzyme activity into high, medium and low categories. Predicted enzyme activity groups were combined and compared between patients and controls. The UGT1A1 and UGT1A8 predicted high enzyme activity genotypes were significantly more (OR=1.62; 95% CI, 1.02-2.56) and less frequent (OR=0.36; 95% CI, 0.15-0.84) among patients with esophageal squamous cell carcinoma (ESCC), respectively. High (OR=0.42; 95% CI, 0.22-0.84) and medium (OR=0.25; 95% CI, 0.12-0.52) activity UGT2B4 genotypes were signifi - cantly less often present in ESCC patients. No association was detected between UGT genotypes and esophageal adenocar- cinoma (EAC) risk. Polymorphisms in UGT genes, resulting in altered enzyme activity genotypes, do not seem modifiers of EAC risk. However, the predicted high activity UGT1A1 genotype, associated with low serum levels of the antioxidant bilirubin, was associated with an increased ESCC risk. The UGT1A8 and UGT2B4 genotypes associated with decreased predicted enzyme activities, were significantly associated with an increased risk of ESCC, probably by a decreased detoxifi - cation of carcinogens.

High enzyme activity UGT1A1 or low activity UGT1A8 and UGT2B4 genotypes increase esophageal cancer risk

Esophageal cancer (EC) has a globally increasing incidence with poor curative treatment options and survival rates. Environmental and dietary factors have crucial roles in esophageal carcinogenesis. Polymorphisms in the UGT genes, a superfamily of enzymes essential for the detoxification of carcinogens, may alter enzyme activity and subsequently may play a role in EC etiology. Rather than solely establishing differences in genotype distribution, we investigated whether functional polymorphisms in UGT genes that can predict enzyme activity in vivo, may influence EC risk. A case-control study including 351 Caucasian EC patients and 592 Caucasian controls was conducted and polymorphisms in seven UGT genes were determined, using the polymerase chain reaction. On the basis of allelic in vitro enzyme activity measurements, genotypes were categorized according to their predicted in vivo enzyme activity into high, medium and low categories. Predicted enzyme activity groups were combined and compared between patients and controls. The UGT1A1 and UGT1A8 predicted high enzyme activity genotypes were significantly more (OR=1.62; 95% CI, 1.02-2.56) and less frequent (OR=0.36; 95% CI, 0.15-0.84) among patients with esophageal squamous cell carcinoma (ESCC), respectively. High (OR=0.42; 95% CI, 0.22-0.84) and medium (OR=0.25; 95% CI, 0.12-0.52) activity UGT2B4 genotypes were significantly less often present in ESCC patients. No association was detected between UGT genotypes and esophageal adenocarcinoma (EAC) risk. Polymorphisms in UGT genes, resulting in altered enzyme activity genotypes, do not seem modifiers of EAC risk. However, the predicted high activity UGT1A1 genotype, associated with low serum levels of the antioxidant bilirubin, was associated with an increased ESCC risk. The UGT1A8 and UGT2B4 genotypes associated with decreased predicted enzyme activities, were significantly associated with an increased risk of ESCC, probably by a decreased detoxification of carcinogens.

Monitoring of Mycophenolic Acid Predose Concentrations in the Maintenance Phase More Than One Year After Renal Transplantation

Routine therapeutic drug monitoring of mycophenolic acid (MPA) is generally performed using the area under the concentration-time curve from 0 to 12 hours (AUC0-12) with recommended values between 30 and 60 μg·h/mL. The aim of this study was to examine whether the monitoring of the MPA predose concentration (C0) in patients who are stable for >1 year after renal transplantation was practical and to determine factors that cause MPA C0 variability among patients. Eighty-six Japanese patients who had undergone renal transplantation and were taking tacrolimus and who had their MPA C0 analyzed >6 times by high-performance liquid chromatography for >1 year posttransplantation were enrolled. Recipients with MPA AUC0-12 levels<30 μg·h/mL on day 28 and 1 year after transplantation had an MPA C0 of <2.0 μg/mL, with a sensitivity of 90.9% and a specificity of 70.7%. There was no significant difference in the mean dose-adjusted MPA C0>1 year after transplantation between subjects with either the UGT (1A1, 1A9, and 2B7) or drug transporter (SLCO1B3, ABCC2, and ABCG2) genotypes. However, in a multiple regression analysis, the dose-adjusted mean MPA C0>1 year after transplantation was significantly associated with age (P=0.0035), creatinine clearance (P=0.0001), and the dose-adjusted MPA AUC0-12 at 1 year (P=0.0147). To keep the MPA AUC0-12>30 μg·h/mL, the plasma threshold for maintaining the MPA C0 with tacrolimus should be set >2.0 μg/mL as determined by high-performance liquid chromatography. For patients who are stable for >1 year after transplantation, continued monitoring of the MPA C0 using the same samples used to monitor the tacrolimus C0 and the additional assessment of the MPA AUC0-12 at the 1-year time point seem to be a viable option. If a change of the mycophenolate mofetil dose seems necessary based on the routine MPA C0 information, the determination of MPA AUC0-12 using a limited sampling strategy is recommended.

Nilotinib Exposure-Response Analysis In Patients with Imatinib-Resistant or -Intolerant Chronic Myeloid Leukemia (CML)

AbstractAbstract 890 Purpose:Nilotinib is a highly selective and potent BCR-ABL inhibitor, approved for the treatment of patients with newly diagnosed Ph+ CML in chronic phase (CP) and CML patients who fail imatinib. The long-term clinical outcome of nilotinib therapy in patients with imatinib-resistant or -intolerant CML has been reported recently in a 24-month follow-up. In contrast to imatinib, the cellular uptake of nilotinib is independent of active transporter expression, so that systemic exposure is likely to be more closely related to patient response. The purpose of this analysis is to evaluate the population pharmacokinetics (PK) of nilotinib and its potential relationship to efficacy and safety in patients with imatinib-resistant or -intolerant CML. Methods:A non-linear mixed effects modeling analysis was performed to determine nilotinib PK. Serum-concentration data from 495 CML patients in CP (n=235), accelerated phase (AP, n=135) or blast crisis (BC, n=125) from Ph I and II studies was used. An exposure-efficacy analysis was performed in patients with CML-CP in Ph II, where the steady-state trough concentrations (Cmin) of nilotinib were computed for individual patients, and then correlated to efficacy measures, including CCyR at 12 months, MMR at 12 and 24 months, time to CCyR, time to MMR, and time to progression (TTP). Patients with baseline T315I mutations or those who had dose escalation to nilotinib 600 mg twice daily prior to the efficacy endpoints were excluded from the analysis. Baseline prognostic factors and mutation status that were previously suggested to affect the clinical benefit of nilotinib therapy were also investigated as potential covariates in the exposure-efficacy analysis, according to Akaike Information Criteria (Kantarjian et al, ASH abstract 2009). The prognostic score was defined as follows: 0 when the patient had baseline HGB >120 g/L, baseline basophils < 4% and no insensitive mutation; 1 if the patient did not satisfy one of the criteria; and 2 if the patient did not satisfy 2 of the criteria. The relationship between nilotinib Cmin, UGT genotype, and total bilirubin levels over 24 months was assessed in all patients from Ph I and II studies. Results:Nilotinib PK was found to be similar in patients with CML-CP, -AP or -BC. Patient age, body weight, ethnicity, and racial group did not significantly affect nilotinib PK. Overall, patients with lower nilotinib Cmin (quartile Q1) tended to have lower CCyR at 12 months, lower MMR at 12 and 24 months, longer time to achieve CCyR and MMR, and shorter TTP compared with patients with higher nilotinib Cmin (quartiles Q2-Q4, Table). Logistic regression of CCyR at 12 months and Cox proportional hazard analysis of TTP demonstrated that in addition to nilotinib Cmin, baseline prognostic scores also significantly affected CCyR (57% and 21% for patients with prognostic scores of 0–1 and 2, respectively) and TTP (27.9 and 18.7 months for patients with prognostic scores of 0–1 and 2, respectively). Both nilotinib Cmin and UGT genotype were significantly associated with the occurrence of total bilirubin abnormality (both p<0.1). Patients with nilotinib Cmin in Q1 (<422 ng/ml, n = 122) had a lower incidence of grade 3/4 bilirubin abnormalities (5.7%) than patients with nilotinib Cmin in Q2 ([422,610) ng/mL, n=120, 9.2%), Q3 ([610,842) ng/mL, n=121, 10.9%), and Q4 (>=842 ng/mL, n = 121, 14.1%), respectively. The occurrence of grade 3/4 bilirubin abnormalities was 6%, 12% and 48% for patients with TA(6)/TA(6), TA(6)/TA(7), and TA(7)/TA(7) UGT genotypes, respectively. Conclusion:Patients with lower nilotinib Cmin and higher baseline prognostic risk score showed a higher risk of progression as well as a trend of poorer response. These data suggest that adherence to nilotinib dose in order to maintain sufficient Cmin is important in maximizing the clinical efficacy of nilotinib therapy. Disclosures:Giles:Novartis: Consultancy, Honoraria. Yin:Novartis : Employment, Equity Ownership. Chia:Novartis: Employment, Equity Ownership. le Coutre:Novartis: Research Funding, Speakers Bureau; Bristol Myers Squibb: Speakers Bureau. Woodman:Novartis: Employment. Ottmann:Novartis: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau. Baccarani:Novartis, Bristol-Myers Squibb: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau. Kantarjian:Novartis: Consultancy, Research Funding; Bristol Myers Squibb: Research Funding; Pfizer: Research Funding.

Pharmacogenetic effect of the UGT polymorphisms on mycophenolate is modified by calcineurin inhibitors

Mycophenolic acid (MPA) is glucuronidated primarily by uridine diphosphate glucuronosyltransferase enzymes (UGT) 1A9 and 1A8. These enzymes are highly polymorphic resulting in low activity and high expression phenotypes. We hypothesized that polymorphisms of UGT1A9 and 1A8 may alter MPA pharmacokinetics in kidney transplantation. One hundred seventeen kidney (n = 93), pancreas (n = 11), or simultaneous kidney and pancreas (SPK) (n = 13) transplant recipients were studied for the effect of UGT1A9 and UGT1A8 polymorphisms on MPA dose-corrected trough concentrations. Individuals were genotyped for UGT1A8 and UGT1A9 polymorphisms (1A8*2, 1A8*3, 1A9*3, 1A9-275 and 1A9-2152). Linear regression was used to estimate the effect of UGT polymorphisms on the individual's mean MPA dose-corrected trough concentration with and without stratification by calcineurin inhibitor. A multiple linear regression analysis was performed to assess the dependence between the average MPA dose-corrected trough concentration and age, gender, UGT genotype (1A8*2, 1A8*3, 1A9*3, 1A9-275, 1A9-2152), serum albumin, hemoglobin (Hgb), hematocrit (HCT), liver transaminases (AST, ALT), serum creatinine, and bilirubin. Mycophenolic acid dose-corrected trough concentrations were 60% higher in subjects heterozygous or homozygous for UGT1A8*2 than in those with the wild type (p = 0.02); however, this effect was dependent on concomitant calcineurin inhibitor. When subjects were stratified by calcineurin inhibitor status, the UGT1A8*2 effect was only apparent in the tacrolimus group (p < 0.01). Mycophenolic acid dose-corrected trough concentrations were 70% lower in carriers of the UGT1A9 -275T>A/-2152 C>T polymorphism who received cyclosporine (p < 0.01). There was no effect of the UGT1A9 -275T>A/-2152C>T polymorphism in the tacrolimus group. The effect of UGT1A8 and UGT1A9 variants on MPA metabolism appears to be modified by concomitant calcineurin inhibitor therapy. Confirmatory in vivo and in vitro studies are needed.

The impact of UGT1A8, UGT1A9, and UGT2B7 genetic polymorphisms on the pharmacokinetic profile of mycophenolic acid after a single oral dose in healthy volunteers. Clin Pharmacol Ther 81 392-400, 2007.

Mycophenolate mofetil (MMF) is a component of most modern immunosuppressive medication regimens for solid organ transplantation and is increasing used in renal diseases of immune pathogenesis. The pharmacokinetics are complex, and there is wide interindividual variation in drug metabolism and exposure. The target for mycophenolic acid, the active metabolite, is de novo purine biosynthesis limiting T cell proliferation capacity in response to stimuli. For other narrow therapeutic index drugs, therapeutic drug level monitoring has proven utility, but with MMF, no simple approach has proved useful. Perhaps knowing metabolism genotype might provide a better insight into dosing in patients before starting immunosuppression with mycophenolic acid. In this study, 17 healthy volunteers with no polymorphisms were compared with 17 carriers of UGT1A9 (−275/−2152) after a single 1.5-g oral dose of MMF). Findings. Compared with control subjects, the patients who were carriers for the specific UGT1A9 polymorphism showed significantly lower exposure to mycophenolic acid and lower estimated enterohepatic recycling. There was no apparent change in metabolism. Compared with the control subjects, carriers of a different UGT1A9 polymorphism, UgT1A9*3, had higher mycophenolic acid maximum concentrations. The results of this study indicate that mycophenolic acid dosage would be significantly affected by the UGT genotype of an individual. This provides at least a partial explanation for why “one size fits all” does not apply to dosing patients with MMF. Commentary. The information in this article, although somewhat peripheral to the day-to-day practice of nephrology, gives insight as to the complexity of mycophenolic acid exposure and thus efficacy and toxicity in individual patients. Clearly, the current practice of starting with a fixed dosage of 1 g twice daily and titrating down to the maximum dosage tolerable by adverse effects such as gastrointestinal intolerance and cytopenias is somewhat primitive. Disappointing is that simple trough level monitoring has not found much utility. Furthermore, there are differential effects of cyclosporine to block enterohepatic recycling and tacrolimus-based regimens to leave this process relatively unaffected. Area-under-the-curve monitoring is simply not practical for most transplant patients in long-term follow-up settings. Also, it is not even known whether the area under the curve is stable over time. Having a signature genotype on the patient's drug-metabolizing enzymes might provide a useful clue to dosing initial therapy with MMF. Further studies on this approach will be forthcoming. For now, therapy with MMF will continue to be empiric. It should be recognized that patients with renal dysfunction have reduced protein binding of mycophenolic acid, leading to higher free concentration and enhanced adverse effects. Thus, nephrotic patients with low serum albumin may be at increased risk for adverse consequences, particularly cytopenias, if dosage adjustment is not made. Although studies that largely were supported by the manufacturers of MMF and the enteric-coated sodium salt have shown that reducing the dosage enhances rejection activity, none of these studies has provided a pharmacokinetic basis for these observations. The enteric-coated formula has shown no superiority in terms of efficacy or gastrointestinal adverse effects, and thus the foregoing discussion most likely applies to both drugs.

Pharmacogenetics of Mycophenolate Mofetil in Patients Undergoing Hematopoietic Cell Transplantation (HCT).

Mycophenolate mofetil (MMF) is commonly used to provide host immunosuppression for hematopoietic cell engraftment and prevention of acute graft vs host disease (GVHD) in recipients of nonmyeloablative allogeneic HCT. There is wide variability in plasma concentrations of mycophenolic acid (MPA), the active metabolite of mycophenolate. Low MPA exposure is associated with poorer rates of engraftment and development of acute GVHD. This variability is not satisfactorily explained by hepatic or renal function suggesting variability may be due to genetic factors involved in drug metabolism or transport. MPA is glucuronidated by UDP glucuronosyltransferase enzymes UGT1A8, 1A9, and 1A10 to the primary metabolite, mycophenolic acid glucuronide (MPAG). MPAG is excreted into the urine and bile through multidrug resistant protein (MRP2) transporters. Several genetic variants of UGT enzymes and MRP2 are known to modify MPA pharmacokinetic parameters in kidney transplant recipients but have not been evaluated in HCT. We hypothesized that these variants are associated with systemic MPA and MPAG concentrations in HCT recipients. Recipient pretransplant DNA was obtained in 133 patients and evaluated for UGT1A8*2, UGT1A8*3, UGT1A9*2, UGT1A9*3, UGT1A9 T-275A, UGT1A9 C-2152T, UGT1A10*2, UGT2B7*2, MRP2 C-24T, MRP2 C-3972T, and MRP2 G-1249A. Patients received MMF at 1–1.5 gm IV or PO every 8–12 hours along with cyclosporine. Each subject had steady-state pharmacokinetics studied once or twice within the first 15 days of transplant for a total of 118 pharmacokinetic profiles. Frequencies of all variants were consistent with published data. Thirty three (24.8%) subjects were heterozygous (CT) and 3 (2.26%) were homozygous (TT) for the MRP2 C-24T variant. MRP2 C-3972T was heterozygous (CT) and homozygous (TT) in 56(42.2%) and 7(5.3%) individuals, respectively. In univariate analysis, there was no association between UGT variants and MPA IV or PO pharmacokinetics. Patients receiving oral MMF and carrying at least one MRP2 C-24T variant had significantly higher median (range) total dose adjusted MPAG Cmax 90.8ug/ml(40.0–164.8) vs 63.3(30.8–202.7), p= 0.02, trough 54.5ug/ml(16.1–99.6) vs 39.7(11.9–173.5), p=0.01 and MPAG Css 71.5ug/ml(28.9–123.0) vs 51.0(19.9–175.6), p=0.01. Similar results were observed for the C-3972T. These data suggest that single UGT variants do not significantly alter MPA exposure but MRP2 variants influence MPAG exposure. Reasons for observed UGT effects on MPA exposure in kidney transplant and not HCT remain unclear but may be due to bioavailability, lack of enterohepatic recycling due to gut decontamination, chemotherapy-induced mucosal and subclinical hepatic damage, and unidentified drug interactions. MRP2 variants may have an impact on other MRP2 substrates such as cyclophosphamide or inhibitors such as cyclosporine. A single UGT genotype to assist in dose selection is unlikely to be of clinical benefit; therefore the effect of combined variants should be explored.

Hepatocyte nuclear factor-1 alpha is associated with UGT1A1, UGT1A9 and UGT2B7 mRNA expression in human liver

Experimental evidence suggests HNF1alpha regulates UGT expression. This study investigates (1) whether the variability in HNF1alpha expression is associated with the variability in UGT1A1, UGT1A9 and UGT2B7 expression in human livers and (2) the functionality of 12 HNF1alpha variants using mRNA expression as phenotype. Controlling for known UGT variation in cis-acting elements known to affect UGT expression, we demonstrate that a combination of HNF1alpha mRNA levels and UGT genotype predicts variance in UGT expression to a higher extent than UGT genotype alone. None of the HNF1alpha polymorphisms studied, however, seem to have an effect on HNF1alpha, UGT1A1, UGT1A9 and UGT2B7 expression, ruling out their functional role. Our data provide evidence for HNF1alpha being a determinant of UGT1A1, UGT1A9 and UGT2B7 mRNA expression. However, the amount of UGT intergenotype variability explained by HNF1alpha expression appears to be modest, and further studies should investigate the role of multiple transcription factors.

Pharmacogenetic analysis of UGT1A1, UGT1A6, UGT1A7 and thymidylate synthase in a phase II study of capecitabine plus irinotecan in patients with metastatic colorectal cancer

3623 Background: Capecitabine (CAP) and irinotecan (IR) are used in the treatment of colorectal cancer (CRC). SN-38, the active metabolite of IR, is metabolized by several UDP-glucuronosyltransferases including UGT1A1, UGT1A6, and UGT1A7. Although UGT1A1 genotype has previously been correlated with IR toxicity, the association between other UGT genotypes and IR response or toxicity has not been determined. CAP is a prodrug of 5-fluorouracil (5FU) that inhibits thymidylate synthase (TS). Although genetic polymorphisms in TS have been associated with antitumor response to 5FU, such relationships are not well established with CAP. The objective of this study was to evaluate the impact of genetic polymorphisms in UGT1A1, UGT1A6, UGT1A7, and TS on response and toxicity in patients with CRC treated with CAP/IR. Methods: 67 chemotherapy-naïve patients (pts) with measurable metastatic CRC were treated with IR (100–125 mg/m2 intravenously on days 1 and 8), plus CAP (orally 900-1000 mg/m2 twice daily on days 2–15). DNA was genotyped using Pyrosequencing, dye terminator sequencing, and GeneScan technologies. Results: The overall response rate was 42% (RECIST Criteria). 26 pts (39%) had CTC grade 3–4 diarrhea, and 7 pts had grade 3–4 neutropenia (10%). Low activity UGT1A7 genotypes, UGT1A7*2/*2 (6 pts) and *3/*3 (7 pts), were significantly associated with antitumor response (p=.005, 11 of 13 patients) and lack of toxicity (p=0.01, only 1 of 13 patients exhibited severe toxicity). There were no statistically significant associations between UGT1A1, UGT1A6 or TS genotypes and toxicity or antitumor response. Conclusions: These data suggest, for the first time, that UGT1A7 genotype may be a useful predictor of response and toxicity in patients with CRC treated with irinotecan-based therapy. Specifically, patients with genotypes associated with low metabolic capacity may be particularly likely to exhibit an antitumor response with little toxicity. Author Disclosure Employment or Leadership Consultant or Advisory Stock Ownership Honoraria Research Funding Expert Testimony Other Remuneration Roche Labs Roche Labs Roche Labs Roche Labs Roche Labs

Pharmacogenetic analysis of UGT1A1, UGT1A6, UGT1A7 and thymidylate synthase in a phase II study of capecitabine plus irinotecan in patients with metastatic colorectal cancer

3623 Background: Capecitabine (CAP) and irinotecan (IR) are used in the treatment of colorectal cancer (CRC). SN-38, the active metabolite of IR, is metabolized by several UDP-glucuronosyltransferases including UGT1A1, UGT1A6, and UGT1A7. Although UGT1A1 genotype has previously been correlated with IR toxicity, the association between other UGT genotypes and IR response or toxicity has not been determined. CAP is a prodrug of 5-fluorouracil (5FU) that inhibits thymidylate synthase (TS). Although genetic polymorphisms in TS have been associated with antitumor response to 5FU, such relationships are not well established with CAP. The objective of this study was to evaluate the impact of genetic polymorphisms in UGT1A1, UGT1A6, UGT1A7, and TS on response and toxicity in patients with CRC treated with CAP/IR. Methods: 67 chemotherapy-naïve patients (pts) with measurable metastatic CRC were treated with IR (100–125 mg/m2 intravenously on days 1 and 8), plus CAP (orally 900-1000 mg/m2 twice daily on days 2–15). DNA was genotyped using Pyrosequencing, dye terminator sequencing, and GeneScan technologies. Results: The overall response rate was 42% (RECIST Criteria). 26 pts (39%) had CTC grade 3–4 diarrhea, and 7 pts had grade 3–4 neutropenia (10%). Low activity UGT1A7 genotypes, UGT1A7*2/*2 (6 pts) and *3/*3 (7 pts), were significantly associated with antitumor response (p=.005, 11 of 13 patients) and lack of toxicity (p=0.01, only 1 of 13 patients exhibited severe toxicity). There were no statistically significant associations between UGT1A1, UGT1A6 or TS genotypes and toxicity or antitumor response. Conclusions: These data suggest, for the first time, that UGT1A7 genotype may be a useful predictor of response and toxicity in patients with CRC treated with irinotecan-based therapy. Specifically, patients with genotypes associated with low metabolic capacity may be particularly likely to exhibit an antitumor response with little toxicity. Author Disclosure Employment or Leadership Consultant or Advisory Stock Ownership Honoraria Research Funding Expert Testimony Other Remuneration Roche Labs Roche Labs Roche Labs Roche Labs Roche Labs

UDP-glucuronosyltransferase and sulfotransferase polymorphisms, sex hormone concentrations, and tumor receptor status in breast cancer patients.

IntroductionUDP-glucuronosyltransferase (UGT) and sulfotransferase (SULT) enzymes are involved in removing sex hormones from circulation. Polymorphic variation in five UGT and SULT genes – UGT1A1 ((TA)6/(TA)7), UGT2B4 (Asp458Glu), UGT2B7 (His268Tyr), UGT2B15 (Asp85Tyr), and SULT1A1 (Arg213His) – may be associated with circulating sex hormone concentrations, or the risk of an estrogen receptor-negative (ER-) or progesterone receptor-negative (PR-) tumor.MethodsLogistic regression analysis was used to estimate the odds ratios of an ER- or PR- tumor associated with polymorphisms in the genes listed above for 163 breast cancer patients from a population-based cohort study of women in western Washington. Adjusted geometric mean estradiol, estrone, and testosterone concentrations were calculated within each UGT and SULT genotype for a subpopulation of postmenopausal breast cancer patients not on hormone therapy 2–3 years after diagnosis (n = 89).ResultsThe variant allele of UGT1A1 was associated with reduced risk of an ER- tumor (P for trend = 0.03), and variants of UGT2B15 and SULT1A1 were associated with non-statistically significant risk reductions. There was some indication that plasma estradiol and testosterone concentrations varied by UGT2B15 and SULT1A1 genotypes; women with the UGT2B15 Asp/Tyr and Tyr/Tyr genotypes had higher concentrations of estradiol than women with the Asp/Asp genotype (P = 0.004). Compared with women with the SULT1A1 Arg/Arg and Arg/His genotypes, women with the His/His genotype had elevated concentrations of testosterone (P = 0.003).ConclusionsThe risk of ER- breast cancer tumors may vary by UGT or SULT genotype. Further, plasma estradiol and testosterone concentrations in breast cancer patients may differ depending on some UGT and SULT genotypes.