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Des-aspartate-angiotensin I (DAA-I) is an endogenous angiotensin peptide and a prototype angiotensin receptor agonist (ARA). It acts on the angiotensin AT receptor and antagonises the deleterious actions of angiotensin II. DAA-I attenuates animal models of human disease in which angiotensin II has been implicated, such as cardiac hypertrophy, neointima formation, arteriosclerosis, renal failure, post-infarction injuries, diabetes, viral infection, chemical-induced inflammation, heat stroke, cancer, and gamma radiation lethality. DAA-I crosses Caco-2 cells and is effective at sub-nanomolar concentrations. These two properties are responsible for its oral efficacy. A single dose-escalation study was conducted to evaluate the safety, tolerability and pharmacokinetics of orally administered DAA-I in 18 healthy subjects. DAA-I was safe and well tolerated by the subjects, who were administered either 0.08, 0.70 or 1.50 mg/kg of the compound. The heart rate and systolic and diastolic blood pressures determined at each post-dose measurement remained within the clinically acceptable range. Across all cohorts, DAA-I had no substantial effect on blood pressures compared with placebo. Electrocardiographs (ECGs) were normal, and none of the subjects complained of chest discomfort. All clinical laboratory tests obtained before and after DAA-I and placebo treatment were normal. Pharmacokinetic analysis over a 12-h period following DAA-I administration did not show any increase of its level beyond basal concentration. This is in line with studies showing that intravenously administered DAA-I is rapidly metabolized and has a short half-life. We postulate that, during its short systemic sojourn, DAA-I exerts its actions via biased agonism on the angiotensin AT receptor. The ClinicalTrial.gov assignment number for this study is NCT02666196. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Purpose: This exploratory study was aimed at elucidating the pharmacogenetics of regulatory nuclear receptors (PXR, CAR, RXRα and HNF4α) and their implications on docetaxel pharmacokinetics and pharmacodynamics in local Chinese nasopharyngeal cancer patients. Methods: A total of 59 single nucleotide polymorphisms (SNPs), including tag-SNPs and functionally relevant SNPs of the genes encoding these regulatory nuclear receptors (PXR/ NR1I2, CAR/ NR1I3, RXRα/ NR2B1 and HNF4α/ NR2A1), were profiled in the patients enrolled in our study by direct sequencing ( N = 50). The generalized linear model was employed to estimate the haplotypic effects on the pharmacokinetics and pharmacodynamics of the patients. Results: The pharmacokinetic profiles of docetaxel in these patients were characterized by marked interindividual variability, with approximately four- to sixfold variations observed in C, AUC and CL. Individual SNP association tests revealed that polymorphisms in NR2B1 and NR2A1 were significantly correlated with altered docetaxel pharmacokinetics. Subsequent haplotype association analysis identified the NR2B1 LD block 2 AG haplotype [*+4458G>A(rs3132291) and *+4988A>G(rs4842198)] to be significantly associated with altered pharmacokinetics, in which patients carrying two copies of the AG haplotype had approximately a 20 % decreased C and AUC and a 21 % increased CL compared to those who carried only one copy or no copies of the haplotype. A number of SNPs in NR1I2, NR1I3, NR2B1 and NR2A1 were also associated with a significant decrease in blood counts from baseline. No haplotype was found to exert any effects on the pharmacodynamics parameters. Conclusions: The present exploratory study identified several SNPs in the genes encoding regulatory nuclear receptors which may account for the interpatient variability in docetaxel pharmacokinetics and pharmacodynamics. These findings highlight the important role of regulatory nuclear receptors on the disposition of docetaxel. [ABSTRACT FROM AUTHOR]

Purpose: To evaluate the maximum tolerated dose (MTD) and pharmacokinetic profile of a chronomodulated, dose-intensified regimen of capecitabine in combination with oxaliplatin (XELOX) in metastatic colorectal cancer (mCRC). Methods: Patients ( N = 18) with 0 or 1 line of prior chemotherapy received oxaliplatin 100 mg/m on day 1 from 1400 to 1800 hours with escalating dose levels of capecitabine (2,500, 3,000, 3,500, 4,000, 4,500, and 5,000 mg) once daily taken at 2400 hours on days 1-5. Each cycle lasted 14 days. Results: The MTD of capecitabine was 4,500 mg. Transaminitis and anemia were the commonest non-hematologic and hematologic toxicities, respectively. Toxicities were generally mild, with only five occurrences of grade 3 toxicity and none of grade 4. There were no dose-limiting toxicities, defined as specific grade 3 or 4 toxicities occurring in the first two cycles of treatment. The objective response rate was 33.3 %, and median overall survival was 16.3 months (95 % CI: 11.2-18.2 months). The maximum plasma concentration ( C) and area under plasma concentration-time curve from time 0 to infinity (AUC) of the capecitabine metabolites in our fixed-dosing chronomodulated regimen were comparable to values seen with comparably dose-intense regimens but associated with significantly reduced toxicity. Conclusions: Chronomodulated dose-intensified XELOX facilitates delivery of dose-intense treatment in mCRC with a favorable therapeutic index that is promising. [ABSTRACT FROM AUTHOR]

Warfarin is a commonly prescribed oral anticoagulant with narrow therapeutic index. It achieves anti-coagulating effects by interfering with the vitamin K cycle. Warfarin has two enantiomers, S(−) and R(+) and undergoes stereoselective metabolism, with the S(−) enantiomer being more effective. We reported the intracellular metabolic profile in HepG2 cells incubated with S(−) and R(+) warfarin by GCMS. Chemometric method PCA was applied to analyze the individual samples. A total of 80 metabolites which belong to different categories were identified. Two batches of experiments (with and without the presence of vitamin K) were designed. In samples incubated with S(−) and R(+) warfarin, glucuronic acid showed significantly decreased in cells incubated with R(+) warfarin but not in those incubated with S(−) warfarin. It may partially explain the lower bio-activity of R(+) warfarin. And arachidonic acid showed increased in cells incubated with S(−) warfarin but not in those incubated with R(+) warfarin. In addition, a number of small molecules involved in γ-glutamyl cycle displayed ratio variations. Intracellular glutathione detection further validated the results. Taken together, our findings provided molecular evidence on a comprehensive metabolic profile on warfarin-cell interaction which may shed new lights on future improvement of warfarin therapy. [ABSTRACT FROM AUTHOR]

Purpose: This exploratory study aimed to explain the interindividual variabilities of docetaxel pharmacokinetics and pharmacodynamics in Asian nasopharyngeal carcinoma patients ( n = 54) through the genotyping of CYP3A4, CYP3A5, ABCB1, ABCC2, ABCG2 and SLCO1B3 genes. Methods: Docetaxel was administered over 1 h on days 1, 8, and 15 every 28 days at 30 mg/m/dose. Genomic DNA was isolated from peripheral blood and genotyped for the selected polymorphisms in the candidate genes. Docetaxel pharmacokinetic parameters were estimated by non-compartmental modelling. Results: Patients homozygous for the variant allele (GG) of SLCO1B3 rs11045585 (IVS12-5676A > G) had significantly higher area under the plasma concentration-time curve of docetaxel ( P = 0.026) and lower clearance ( P = 0.036) compared to patients with AA/AG genotypes. Patients harbouring the heterozygous genotype (GA + GT + TA) for ABCB1 rs2032582 (2677G > T/A) had the highest percentage decrease in nadir haemoglobin from cycle 1 baseline compared to those with GG/TT genotypes ( P = 0.006). Similar trend was observed for ABCB1 rs1045642 (3435C > T) with heterozygotes (CT) having the highest percentage decrease in nadir haemoglobin from cycle 1 baseline compared to those with CC/TT genotypes ( P = 0.066). Conclusions: This study suggests that the cooperative influence of functional polymorphisms in SLCO1B3 and ABCB1 genes may be responsible for the interindividual variability in docetaxel disposition in Asian nasopharyngeal cancer patients. [ABSTRACT FROM AUTHOR]

The aim of this study was to characterize the population frequency of SLCO1B1 polymorphic variants in three distinct healthy Asian populations, namely Chinese ( n = 100), Malay ( n = 100) and Indian ( n = 100), and to explore the association between haplotype-tagged single nucleotide polymorphisms (htSNPs) on hepatic SLCO1B1 mRNA expression. The distribution of polymorphic variants in the SLCO1B1 gene at eight loci that spanned approximately 48 kb was investigated in the three different Asian ethnic groups and in 32 non-cancerous liver tissues from Chinese patients. Of the 26 polymorphisms screened, we found eight polymorphic variants that differed in genotypic and allelic frequencies between the Chinese, Malay and Indian populations. Significant interethnic differences were observed in the genotype frequency distributions across the promoter SNP [g.-11187G>A ( P = 0.030)] as well as three coding region SNPs [c.388G>A ( P < 0.001); c.571T>C ( P < 0.001); c.597C>T ( P < 0.001)] in the healthy subjects. Haplotype analysis revealed 12 different haplotypes in both the Chinese and Malay populations and 18 haplotypes in the Indian population. In both the Malay and Indian populations, the htSNPs were c.388A>G, c.571T>C and c.597C>T, whereas in the Chinese population they were g.-11187G>A, c.388A>G and c.597C>T. The c.388A>G and c.597C>T htSNPs accounted for more than 70% of the variations between the three major haplotypes in each Asian ethnic group. In terms of the c.388A>G htSNPs, genotypic-phenotypic association analyses revealed that there was no effect on SLCO1B1 expression in hepatic tissues; in addition, no genotypic-phenotypic associations were evident with regards to the c.597C>T htSNP. Future studies should investigate the phenotypic effects of the c.388A>G htSNP on the disposition of OATP1B1 substrates in Asian populations. [ABSTRACT FROM AUTHOR]

Warfarin is a widely prescribed anticoagulant for thromboembolic disorders and exhibits wide inter-individual differences in its pharmacodynamic effects. Warfarin exerts its anticoagulant effect by inhibiting the enzymatic activity of vitamin K 2,3-epoxide reductase complex, subunit 1 (VKORC1) which regenerates reduced vitamin K as an essential cofactor for the post-translational γ-carboxylation of glutamic acid residues on coagulation factors II, VII, IX and X, and the anticoagulant proteins C, S and Z. Recent studies have shown polymorphisms in genes involved in the uptake of vitamin K (apolipoprotein E [ApoE]), reduction of vitamin K 2,3-epoxide (VKORC1), metabolism of warfarin (cytochrome P450 2C9 [CYP2C9]), and gamma carboxylation (γ-glutamyl carboxylase [GGCX]) to influence the pharmacokinetics and pharmacodynamics of warfarin in patients from different ethnic backgrounds, resulting in variable warfarin dose requirements. Understanding the causal relationship of these polygenic influences on warfarin dose requirements in patients of different ethnicity may be vital in reducing inter-patient variability and optimising anticoagulant therapy. [ABSTRACT FROM AUTHOR]

Background: Photodynamic therapy (PDT) is a promising therapeutic modality using a tumor localizing photosensitizer and light to destroy tumor cells. A major limitation of PDT is tumor recurrence, which is partly due to neovascularization. Purpose: The objective of the present study was to determine whether combination therapy with PDT and antiangiogenic agents (i.e. SU5416 and SU6668) would be more effective in controlling tumor recurrence in a mouse model of human CNE2 poorly differentiated nasopharyngeal carcinoma compared with PDT or antiangiogenic agents administered alone. Methods: Athymic mice bearing CNE2 tumor xenografts received daily i.p. injections of 20 mg/kg SU5416 or 100 mg/kg SU6668 for 28 consecutive days either alone or following a single hypericin-PDT treatment. Results: Significant inhibition of CNE2 tumor growth was observed in all treatment groups. Differences in 4× tumor growth time, the number of mice with 4× tumor growth, tumor growth inhibition as well as the percent of mice surviving were not statistically significant among individual treatment groups. However, the number of mice with 4× tumor growth observed in SU6668 monotherapy and combined PDT and SU6668 treatment groups was significantly less than that in the control group ( P<0.05 and 0.01, respectively). Moreover, compared with the control group, only the combined PDT and SU6668 treatment significantly extended survival of tumor-bearing host mice ( P<0.05). The semiquantitative RT-PCR results showed that the expression of HIF-1α, VEGF, COX-2 and bFGF were increased in PDT-treated tumor samples collected 24 h post-PDT, suggesting that PDT-induced damage to tumor microvasculature and the resultant hypoxia upregulate the expression of certain proangiogenic factors. Conclusions: The effectiveness of PDT can be enhanced by antiangiogenic treatment with the synthetic RTK inhibitors. Of the two synthetic RTK inhibitors tested, SU6668 was more effective than SU5416 in enhancing tumor responsiveness to PDT. [ABSTRACT FROM AUTHOR]

A correction to the article "Pharmacogenetics of SLCO1B1: haplotypes, htSNPs and hepatic expression in three distinct Asian populations," that was published in the June 21, 2007 issue is presented.