Protocol for the diagnostic performance of C reactive protein, procalcitonin and interleukin-6 for serious bacterial infections among children ≤36 months old presenting with fever without source: a systematic review and meta-analysis.

INTRODUCTION: The management of fever without source in children ≤36 months old remains a diagnostic challenge as the underlying aetiologies can vary from self-limiting viral infections to serious bacterial infections (SBIs). Biomarkers such as C reactive protein (CRP), procalcitonin (PCT) and interleukin-6 (IL-6) have varying thresholds in the prediction of SBIs due to differences in SBI definitions, SBI prevalence, patient characteristics and timing of presentation. This protocol describes a systematic review and meta-analysis that aims to determine the thresholds at which CRP, PCT and IL-6 can perform optimally in distinguishing the presence of SBIs in children ≤36 months old, as well as to determine their performances in early detection of bacterial infections within 48 hours of fever onset. METHODS AND ANALYSIS: We will systematically search electronic databases including MEDLINE, Cochrane Central Register of Controlled Trials, Cochrane CENTRAL, EMBASE, CINAHL (Cumulative Index to Nursing and Allied Health Literature) and Science Citation Index from 1 July 2023 to 31 July 2023. We will include studies that report the diagnostic accuracy of CRP, PCT and IL-6 in detecting SBIs in children aged ≤36 months presenting with fever without apparent source. Randomised controlled trials (RCTs) and non-randomised studies including non-RCTs and controlled before-and-after studies will be included. A meta-analysis will be performed and diagnostic performances of these biomarkers will be reported. ETHICS AND DISSEMINATION: The results of this study will provide guidance on clinical decision-making in young children presenting with fever without source. Ethics approval will not be required for this study. The authors aim to publish the findings in a peer-reviewed journal as well as present at international conferences. PROSPERO REGISTRATION NUMBER: CRD42023439093.

Cooperative regulation of coupled oncoprotein synthesis and stability in triple-negative breast cancer by EGFR and CDK12/13.

Evidence has long suggested that epidermal growth factor receptor (EGFR) may play a prominent role in triple-negative breast cancer (TNBC) pathogenesis, but clinical trials of EGFR inhibitors have yielded disappointing results. Using a candidate drug screen, we identified that inhibition of cyclin-dependent kinases 12 and 13 (CDK12/13) dramatically sensitizes diverse models of TNBC to EGFR blockade. This combination therapy drives cell death through the 4E-BP1-dependent suppression of the translation and translation-linked turnover of driver oncoproteins, including MYC. A genome-wide CRISPR/Cas9 screen identified the CCR4-NOT complex as a major determinant of sensitivity to the combination therapy whose loss renders 4E-BP1 unresponsive to drug-induced dephosphorylation, thereby rescuing MYC translational suppression and promoting MYC stability. The central roles of CCR4-NOT and 4E-BP1 in response to the combination therapy were further underscored by the observation of CNOT1 loss and rescue of 4E-BP1 phosphorylation in TNBC cells that naturally evolved therapy resistance. Thus, pharmacological inhibition of CDK12/13 reveals a long-proposed EGFR dependence in TNBC that functions through the cooperative regulation of translation-coupled oncoprotein stability.

Cross-Ancestry Genome-Wide Association Study Defines the Extended CYP2D6 Locus as the Principal Genetic Determinant of Endoxifen Plasma Concentrations.

The therapeutic efficacy of tamoxifen is predominantly mediated by its active metabolites 4-hydroxy-tamoxifen and endoxifen, whose formation is catalyzed by the polymorphic cytochrome P450 2D6 (CYP2D6). Yet, known CYP2D6 polymorphisms only partially determine metabolite concentrations in vivo. We performed the first cross-ancestry genome-wide association study with well-characterized patients of European, Middle-Eastern, and Asian descent (n = 497) to identify genetic factors impacting active and parent metabolite formation. Genome-wide significant variants were functionally evaluated in an independent liver cohort (n = 149) and in silico. Metabolite prediction models were validated in two independent European breast cancer cohorts (n = 287, n = 189). Within a single 1-megabase (Mb) region of chromosome 22q13 encompassing the CYP2D6 gene, 589 variants were significantly associated with tamoxifen metabolite concentrations, particularly endoxifen and metabolic ratio (MR) endoxifen/N-desmethyltamoxifen (minimal P = 5.4E-35 and 2.5E-65, respectively). Previously suggested other loci were not confirmed. Functional analyses revealed 66% of associated, mostly intergenic variants to be significantly correlated with hepatic CYP2D6 activity or expression (ρ = 0.35 to -0.52), and six hotspot regions in the extended 22q13 locus impacting gene regulatory function. Machine learning models based on hotspot variants (n = 12) plus CYP2D6 activity score (AS) increased the explained variability (~ 9%) compared with AS alone, explaining up to 49% (median R2 ) and 72% of the variability in endoxifen and MR endoxifen/N-desmethyltamoxifen, respectively. Our findings suggest that the extended CYP2D6 locus at 22q13 is the principal genetic determinant of endoxifen plasma concentration. Long-distance haplotypes connecting CYP2D6 with adjacent regulatory sites and nongenetic factors may account for the unexplained portion of variability.

Validation and comparison of the PECARN rule, Step-by-Step approach and Lab-score for predicting serious and invasive bacterial infections in young febrile infants.

INTRODUCTION: Differentiating infants with serious bacterial infections (SBIs) or invasive bacterial infections (IBIs) from those without remains a challenge. We sought to compare the diagnostic performances of single biomarkers (absolute neutrophil count [ANC], C-reactive protein [CRP] and procalcitonin [PCT]) and 4 diagnostic approaches comprising Lab-score, Step-by-Step approach (original and modified) and Pediatric Emergency Care Applied Research Network (PECARN) rule. METHOD: This is a prospective cohort study involving infants 0-90 days of age who presented to an emergency department from July 2020 to August 2021. SBIs were defined as bacterial meningitis, bacteraemia and/or urinary tract infections. IBIs were defined as bacteraemia and/or bacterial meningitis. We evaluated the performances of Lab-score, Step-by-Step (original and modified) and PECARN rule in predicting SBIs and IBIs. RESULTS: We analysed a total of 258 infants, among whom 86 (33.3%) had SBIs and 9 (3.5%) had IBIs. In predicting SBIs, ANC ≥4.09 had the highest sensitivity and negative predictive value (NPV), while PCT ≥1.7 had the highest specificity and positive predictive value (PPV). CRP ≥20 achieved the highest area under receiver operating characteristic curve (AUC) of 0.741 (95% confidence interval [CI] 0.672-0.810). The Step-by-Step (original) approach had the highest sensitivity (97.7%). Lab-score had the highest AUC of 0.695 (95% CI 0.621-0.768), compared to PECARN rule at 0.625 (95% CI 0.556-0.694) and Step-by-Step (original) at 0.573 (95% CI 0.502-0.644). In predicting IBIs, PCT ≥1.7 had the highest sensitivity, specificity, PPV and NPV. The Step-by-Step (original and modified) approach had the highest sensitivity of 100%. Lab-score had the highest AUC of 0.854 (95% CI 0.731-0.977) compared to PECARN rule at 0.589 (95% CI 0.420-0.758) and Step-by-Step at 0.562 (95% CI 0.392-0.732). CONCLUSION: CRP strongly predicted SBIs, and PCT strongly predicted IBI. The Step-by-Step approach had the highest sensitivity and NPV, while Lab-score had the highest specificity and AUC in predicting SBIs and IBIs.

A phase 1b study of OXIRI in pancreatic adenocarcinoma patients and its immunomodulatory effects.

Pancreatic ductal adenocarcinoma (PDAC) is a highly lethal and debilitating disease with limited therapeutic options. The aim of this clinical study was to evaluate the safety, efficacy and pharmacokinetics of a novel regimen comprised of metronomic oxaliplatin (O), chronomodulated capecitabine (X) and UGT1A1 genotype-guided dosing of irinotecan (IRI) [OXIRI] as well as its immunomodulatory effects. Thirty-six patients were enrolled into either dose-escalation or expansion cohorts. In the dose escalation phase, capecitabine doses (2000, 2650, 3500 and 4500 mg/day) were administered at midnight on days 1 to 14 while oxaliplatin and irinotecan were intravenously infused at fixed doses of 50 and 75 mg/m2 respectively on days 1, 8 in a 21-day cycle. The maximum tolerated dose of capecitabine was 2650 mg/day and the most common grade 3 adverse events were neutropenia (30.6%) and diarrhea (13.9%). No grade 4 toxicity was observed. UGT1A1-genotype directed dosing resulted in similar exposure levels of irinotecan, SN-38 and SN-38G in all patients. Objective response rate was 22.2%. Median overall survival and progression-free survival were 8.1 and 5.2 months, respectively. Exploratory immunoprofiling by flow cytometry and quantitative spatial localization analysis of infiltrated immune cells performed on biopsy and plasma samples revealed significant declines in CCL22, CCL2 and TNFα levels at end of first cycle and an active host immune response. Our study showed that OXIRI was well-tolerated and exhibited good efficacy, with immunomodulatory effects. It may be considered as an alternative to FOLFIRINOX in patients intolerant to the latter.

Excellent Survival Outcomes of Pediatric Patients With Acute Myeloid Leukemia Treated With the MASPORE 2006 Protocol.

PURPOSE: To determine the prognostic factors in pediatric patients with acute myeloid leukemia (AML) and to assess whether their outcomes have improved over time. PATIENTS AND METHODS: Sixty-two patients with AML excluding acute promyelocytic leukemia were retrospectively analyzed. Patients in the earlier cohort (n = 36) were treated on the Medical Research Council (MRC) AML12 protocol, whereas those in the recent cohort (n = 26) were treated on the Malaysia-Singapore AML protocol (MASPORE 2006), which differed in terms of risk group stratification, cumulative anthracycline dose, and timing of hematopoietic stem-cell transplantation for high-risk patients. RESULTS: Significant improvements in 10-year overall survival and event-free survival were observed in patients treated with the recent MASPORE 2006 protocol compared to the earlier MRC AML12 protocol (overall survival: 88.0% ± 6.5% vs 50.1% ± 8.6%, P = .002; event-free survival: 72.1% ± 9.0 vs 50.1% ± 8.6%, P = .045). In univariate analysis, patients in the recent cohort had significantly lower intensive care unit admission rate (11.5% vs 47.2%, P = .005) and numerically lower relapse rate (26.9% vs 50.0%, P = .068) compared to the earlier cohort. Multivariate analysis showed that treatment protocol was the only independent predictive factor for overall survival (hazard ratio = 0.21; 95% confidence interval, 0.06-0.73, P = .014). CONCLUSION: Outcomes of pediatric AML patients have improved over time. The more recent MASPORE 2006 protocol led to significant improvement in long-term survival rates and reduction in intensive care unit admission rate.

Pharmacokinetics Alterations in Critically Ill Pediatric Patients on Extracorporeal Membrane Oxygenation: A Systematic Review.

Objectives: This study aimed to identify alterations in pharmacokinetics in children on extracorporeal membrane oxygenation (ECMO), identify knowledge gaps, and inform future pharmacology studies. Data Sources: We systematically searched the databases MEDLINE, CINAHL, and Embase from earliest publication until November 2018 using a controlled vocabulary and keywords related to "ECMO" and "pharmacokinetics," "pharmacology," "drug disposition," "dosing," and "pediatrics." Study Selection: Inclusion criteria were as follows: study population aged <18 years, supported on ECMO for any indications, received any medications while on ECMO, and reported pharmacokinetic data. Data Extraction: Clearance and/or volume of distribution values were extracted from included studies. Data Synthesis: Forty-one studies (total patients = 574) evaluating 23 drugs met the inclusion criteria. The most common drugs studied were antimicrobials (n = 13) and anticonvulsants (n = 3). Twenty-eight studies (68%) were conducted in children <1 year of age. Thirty-three studies (80%) were conducted without intra-study comparisons to non-ECMO controls. Increase in volume of distribution attributable to ECMO was demonstrated for nine (56%) drugs: cefotaxime, gentamicin, piperacillin/tazobactam, fluconazole, micafungin, levetiracetam, clonidine, midazolam, and sildenafil (range: 23-345% increase relative to non-ECMO controls), which may suggest the need for higher initial dosing. Decreased volume of distribution was reported for two drugs: acyclovir and ribavirin (50 and 69%, respectively). Decreased clearance was reported for gentamicin, ticarcillin/clavulanate, bumetanide, and ranitidine (range: 26-95% decrease relative to non-ECMO controls). Increased clearance was reported for caspofungin, micafungin, clonidine, midazolam, morphine, and sildenafil (range: 25-455% increase relative to non-ECMO controls). Conclusions: There were substantial pharmacokinetic alterations in 70% of drugs studied in children on ECMO. However, studies evaluating pharmacokinetic changes of many drug classes and those that allow direct comparisons between ECMO and non-ECMO patients are still lacking. Systematic evaluations of pharmacokinetic alterations of drugs on ECMO that incorporate multidrug opportunistic trials, physiologically based pharmacokinetic modeling, and other methods are necessary for definitive dose recommendations. Trial Registration Prospero Identifier: CRD42019114881.

An intronic FTO variant rs16952570 confers protection against thiopurine-induced myelotoxicities in multiethnic Asian IBD patients.

Thiopurines are used in the treatment of inflammatory bowel disease (IBD) but remain clinically challenging to manage due to wide interpatient variability in clinical outcomes and adverse events. Apart from genetic variants in thiopurine S-methyltransferase (TPMT) and nudix hydrolase 15 (NUDT15) genes, polymorphisms in FTO alpha-ketoglutarate dependent dioxygenase (FTO) were found predictive of thiopurine-induced leukopenia, albeit with conflicting results. To clarify the role of FTO variants in a multiethnic Asian IBD cohort, we recruited 149 patients on thiopurine-based therapy and genotyped two FTO variants p.Ala134Thr (rs79206939) and rs16952570 T > C using Sanger sequencing. FTO p.Ala134Thr (rs79206939) was non-polymorphic and absent whereas intronic rs16952570 T > C was equally prevalent in Chinese (22%) and Indians (18%) and higher in Malays (28%). Higher nadir white blood cell (WBC) and absolute neutrophil count (ANC) levels were observed in patients harboring FTO rs16952570 CC genotypes compared with TT carriers at 4, 8, and 12 weeks after start of thiopurine therapy (P < 0.05). A similar trend was observed in patients carrying the previously well-characterized NUDT15 rs116855232 wild-type CC genotypes. Further in silico analysis suggests that FTO variants linked to rs16952570, particularly rs74018601, may play a regulatory role in altering the FTO expression. The findings from this study indicate a novel protective association with the FTO variant rs16952570 CC genotype and hematological parameters.

Predictive role of NUDT15 variants on thiopurine-induced myelotoxicity in Asian inflammatory bowel disease patients.

BACKGROUND: Genetic variants of TPMT and NUDT15 have been reported to predict the inter-patient variability in response and toxicity profiles of patients receiving thiopurine therapy. However, the clinical utility of TPMT genotyping in guiding thiopurine doses has been questionable, in part due to underlying differences in the prevalence of TPMT variants in both Caucasian and Asian populations. Several NUDT15 variants have been associated with thiopurine-induced leukopenia, particularly in Asian cohorts. So far, none have been reported in a multiethnic Asian population. AIM: To investigate the associations between TPMT and NUDT15 variants with thiopurine-induced myelotoxicity in 129 Asian inflammatory bowel disease patients. MATERIALS & METHODS: Pyrosequencing was performed to screen for TPMT and NUDT15 variants. Intracellular steady-state metabolite concentrations were quantified using liquid chromatography-tandem mass spectrometry. RESULTS: Significant declines in nadir white blood cell, absolute neutrophil count and platelet counts were observed with increasing copy numbers of the risk T allele at NUDT15 c.415C>T locus (overall p < 0.05) within 4, 8 and 12 weeks and 6 months after thiopurine initiation. Patients with low and intermediate NUDT15 activity, as inferred from haplotype pairs, had significantly higher risks of leukopenia (p = 0.000253) and neutropenia (p = 0.002) compared with patients with normal NUDT15 activity. CONCLUSION: These findings highlight the critical relevance of NUDT15 pharmacogenetics in predicting for thiopurine-induced myelotoxicity and confirm the lack of significance of TPMT variants in Asian inflammatory bowel disease patients.

Influence of the KDM4A rs586339 polymorphism on overall survival in Asian non-small-cell lung cancer patients.

The critical role of lysine demethylase 4A (KDM4A), in regulating chromatin structure and consequently in driving cellular proliferation and oncogenesis has been the focus of recent studies. Non-small-cell lung cancer (NSCLC) patients with adenocarcinoma histology who were homozygous for KDM4A single nucleotide polymorphism (SNP)-A482 (rs586339) were recently shown to have significantly worse overall survival (OS) compared with patients with the wild-type or the heterozygous genotype at this locus (hazard ratio=1.68, P=0.042). In the current study, we investigated the association between the same polymorphism with OS in our Asian NSCLC-adenocarcinoma patients comprising Chinese (N=572), Malays (N=50), and Indians (N=22). KDM4A SNP-A482 genotype status was determined by Sanger sequencing. OS was calculated from the date of diagnosis to date of death or censored at the date of last follow-up. Kaplan-Meier analysis, log-rank test, and Cox regression methods were utilized to evaluate OS outcomes. KDM4A SNP-A482 had a minor allele (C) frequency of 18.8% and a major allele (A) frequency of 81.2% in our Asian NSCLC (adenocarcinoma) patients. However, the OS in our Asian NSCLC patients homozygous for KDM4A SNP-A482 was not significantly different from those who were wild type or heterozygous at this locus [CC vs. AA/AC: median OS (95% confidence interval): 40.2 (18.7-61.6) vs. 29.6 (26.9-32.3) months; P=0.858]. The results remained statistically nonsignificant even after adjustment for epidermal growth factor receptor mutational status, suggesting that KDM4A SNP-A482 does not significantly influence OS in Asian NSCLC patients.

EGFR Mutation Subtypes Influence Survival Outcomes following First-Line Gefitinib Therapy in Advanced Asian NSCLC Patients.

INTRODUCTION: Activating mutations in the EGFR gene have been shown to confer sensitivity to EGFR tyrosine kinase inhibitors in patients with advanced NSCLC. However, wide interpatient variability in treatment outcomes in response to EGFR tyrosine kinase inhibitors in these patients remains unaccounted for. This study aimed to evaluate the influence of EGFR mutation types and subtypes on survival outcomes in advanced Asian patients with NSCLC receiving first-line gefitinib therapy. METHODS: Patients with stage IIIB or IV NSCLC who were harboring EGFR mutations, receiving first-line gefitinib treatment, and of Asian descent (N = 383) were evaluated. Overall survival (OS) and progression-free survival (PFS) were estimated by Kaplan-Meier analysis. Log-rank tests and Cox proportional hazards models were implemented to evaluate the differences in PFS and OS. RESULTS: Significant differences in PFS were observed between patients carrying EGFR mutations in exons 18, 19, 20, and 21, with patients carrying EGFR exon 19 mutations having the longest median PFS (overall p = 8.88 × 10-15). Comparison of PFS among the five different exon 19 mutation subtypes and among the two exon 19 deletion start codons did not reveal any significant differences. No significant difference was observed in OS among patients carrying EGFR mutations on different exons (overall p = 0.054); however, OS was found to be significantly different among the various subtypes of exon 19 mutations, with the 15-nucleotide deletion "non-ELREA" group having the shortest OS of 11.3 months (overall p = 0.025). CONCLUSIONS: EGFR mutation types and subtypes significantly influence survival outcomes in patients with advanced NSCLC who are receiving first-line gefitinib treatment.

Pharmacogenetics of drug transporters in modulating imatinib disposition and treatment outcomes in chronic myeloid leukemia & gastrointestinal stromal tumor patients.

The use of imatinib in the treatment of BCR-ABL-positive chronic myeloid leukemia and gastrointestinal stromal tumors has significantly improved survival outcomes in patients afflicted by these malignancies. However, a substantial proportion of imatinib-treated patients still experience treatment failure. Suboptimal concentrations of imatinib have been postulated to contribute at least partially to the development of resistance against imatinib. Indeed, variations in the genes encoding drug transporters have been reported to markedly influence imatinib disposition and treatment outcomes in various populations. This review aims to consolidate and critically assess the studies conducted to date which have investigated the influence of pharmacogenetic variants in drug transporters on the disposition of imatinib and treatment outcomes in Asians and other populations.

Pharmacogenetics of irinotecan, doxorubicin and docetaxel transporters in Asian and Caucasian cancer patients: a comparative review.

Drug efflux and influx transporters play critical roles in regulating the cellular drug disposition and modulating the pharmacokinetics and pharmacodynamics of anti-cancer agents, which may potentially alter treatment outcomes. The efficiency of drug transport is often dependent on the expression and activity of these membrane-bound proteins, factors which have been shown to be regulated by genes that are known to be highly polymorphic in different ethnic populations. The role of drug transporters becomes even more critical for anti-cancer agents due to the narrow therapeutic windows that separate treatment response and toxicities for these agents. Moreover, high inter-individual variability in the disposition of anti-cancer agents often results in variable treatment outcomes among patients receiving standard doses of the same drug. Such variability has been attributed at least in part to polymorphisms in genes encoding drug-metabolizing enzymes and transporter. To date, numerous pharmacogenetic studies have investigated the associations between variants in the ABC and SLC transporters genes with drug disposition, treatment outcomes and drug-induced toxicities. However, the strengths of these associations and their clinical relevance in different ethnic populations have not been critically examined. This review aims to summarize and evaluate the implications of pharmacogenetic variants in the ABC and SLC transporters genes on the pharmacokinetics and clinical outcomes of three anti-cancer agents: irinotecan, docetaxel and doxorubicin in Caucasian and Asian patients.

Phase I Study of Oral Vinorelbine in Combination with Erlotinib in Advanced Non-Small Cell Lung Cancer (NSCLC) Using Two Different Schedules.

PURPOSE: This study aimed to evaluate the safety, tolerability and pharmacokinetics of the combination of oral vinorelbine with erlotinib using the conventional (CSV) and metronomic (MSV) dosing schedules in patients with advanced non-small cell lung cancer (NSCLC). METHODS: This was an open-label, multiple dose-escalation phase I study. An alternating 3+3 phase I design was employed to allow each schedule to enroll three patients sequentially at each dose level. Thirty patients with Stage IIIB/IV NSCLC were treated with escalating doses of oral vinorelbine starting at 40 mg/m2 on day 1 and 8 in the CSV group (N = 16) and at 100 mg/week in the MSV group (N = 14). Erlotinib was administered orally daily. RESULTS: The maximum tolerated dose was vinorelbine 80 mg/m2 with erlotinib 100 mg in the CSV group and vinorelbine 120 mg/week with erlotinib 100 mg in the MSV group. Grade 3/4 toxicities included neutropenia (N = 2; 13%) and hyponatremia (N = 1; 6%) in the CSV group, and neutropenia (N = 5; 36%) in the MSV group. Objective response was achieved in 38% and 29% in the CSV and MSV groups respectively. Vinorelbine co-administration did not significantly affect the pharmacokinetics of erlotinib and OSI-420 after initial dose. However, at steady-state, significantly higher Cmax, higher Cmin and lower CL/F of erlotinib were observed with increasing dose levels of vinorelbine in the CSV group. Significantly higher steady-state Cmin, Cavg and AUCss of erlotinib were observed with increasing dose levels of vinorelbine in the MSV group. CONCLUSIONS: Combination of oral vinorelbine with erlotinib is feasible and tolerable in both the CSV and MSV groups. TRIAL REGISTRATION: ClinicalTrials.gov NCT00702182.

Pharmacogenetics of UGT1A4, UGT2B7 and UGT2B15 and Their Influence on Tamoxifen Disposition in Asian Breast Cancer Patients.

Tamoxifen (TAM) is an established endocrine treatment for all stages of oestrogen receptor (ER)-positive breast cancer. Its complex metabolism leads to the formation of multiple active and inactive metabolites. One of the main detoxification and elimination pathways of tamoxifen and its active metabolites, 4-hydroxytamoxifen (4-OHT) and endoxifen, is via glucuronidation catalysed by uridine 5'-diphospho-glucuronosyltransferases (UGTs). However, few studies have comprehensively examined the impact of variations in the genes encoding the major hepatic UGTs on the disposition of tamoxifen and its metabolites. In the present study, we systematically sequenced exons, exon/intron boundaries, and flanking regions of UGT1A4, UGT2B7 and UGT2B15 in 240 healthy subjects of different Asian ethnicities (Chinese, Malays and Indians) to identify haplotype tagging single nucleotide polymorphisms. Subsequently, 202 Asian breast cancer patients receiving tamoxifen were genotyped for 50 selected variants in the three UGT genes to comprehensively investigate their associations with steady-state plasma levels of tamoxifen, its active metabolites and their conjugated counterparts. The UGT1A4 haplotype (containing variant 142T>G, L48 V defining the *3 allele) was strongly associated with higher plasma levels of TAM-N-glucuronide, with a twofold higher metabolic ratio of TAM-N-glucuronide/TAM observed in carriers of this haplotype upon covariate adjustment (P < 0.0001). Variants in UGT2B7 were not associated with altered O-glucuronidation of both 4-OHT and endoxifen, while UGT2B15 haplotypes had a modest effect on (E)-endoxifen plasma levels after adjustment for CYP2D6 genotypes. Our findings highlight the influence of UGT1A4 haplotypes on tamoxifen disposition in Asian breast cancer patients, while genetic variants in UGT2B7 and UGT2B15 appear to be of minor importance.

Association of CYP2C19*2 and associated haplotypes with lower norendoxifen concentrations in tamoxifen-treated Asian breast cancer patients.

AIM: The aim was to examine the influence of CYP2C19 variants and associated haplotypes on the disposition of tamoxifen and its metabolites, particularly norendoxifen (NorEND), in Asian patients with breast cancer. METHODS: Sixty-six CYP2C19 polymorphisms were identified in healthy Asians (n = 240), of which 14 were found to be tightly linked with CYP2C19*2, CYP2C19*3 and CYP2C19*17. These 17 SNPs were further genotyped in Asian breast cancer patients receiving tamoxifen (n = 201). Steady-state concentrations of tamoxifen and its metabolites were quantified using liquid chromatography­mass spectrometry. Non-parametric tests and regression methods were implemented to evaluate genotypic­phenotypic associations and haplotypic effects of the SNPs. RESULTS: CYP2C19 functional polymorphisms and their linked SNPs were not significantly associated with plasma concentrations of tamoxifen and its main metabolites N-desmethyltamoxifen, (Z)-4-hydroxytamoxifen and (Z)-Endoxifen. However, CYP2C19*2 and its seven linked SNPs were significantly associated with lower NorEND concentrations, MRNorEND/NDDM and MRNorEND/(Z)-END. Specifically, patients carrying the CYP2C19*2 variant allele A had significantly lower NorEND concentrations [median (range), GG vs. GA vs. AA: 1.51 (0.38­3.28) vs. 1.28 (0.30­3.36) vs. 1.15 ng ml−1 (0.26­2.45, P = 0.010)] as well as significantly lower MRNorEND/(Z)-END [GG vs. GA vs. AA: 9.40 (3.27­28.35) vs. 8.15 (2.67­18.9) vs. 6.06 (4.47­14.6), P < 0.0001] and MRNorEND/NDDM [GG vs. GA vs. AA: 2.75 (0.62­6.26) vs. 2.43 (0.96­4.18) vs. 1.75 (1.10­2.49), P < 0.00001]. CYP2C19 H2 haplotype, which included CYP2C19*2, was also significantly associated with lower NorEND concentrations (P = 0.0020), MRNorEND/NDDM (P < 0.0001) and MRNorEND/(Z)-END (P < 0.0001), indicating significantly lower formation rates of NorEND. CONCLUSION: These data highlight the potential relevance of CYP2C19 pharmacogenetics in influencing NorEND concentrations in tamoxifen-treated patients, which may influence treatment outcomes.