Analysis of the DPYD gene implicated in 5-fluorouracil catabolism in Chinese cancer patients

Background and objective: 5‐fluorouracil (5‐FU) is still a widely used anticancer drug. More than 85% of the 5‐FU administered is catabolized by dihydropyrimidine dehydrogenase (DPD) in the liver. However, mutations in the DPD gene have been found to be associated with low DPD activity causing severe complications. The purpose of this study was to determine the mutation frequency of four exons in Chinese cancer patients and the relationship between genotype and DPD activity. Methods: Samples from 142 cancer patients were investigated in this study. The DPD activity was determined by reversed‐phase HPLC. Exons 2, 13, 14 and 18 were amplified by polymerase chain reaction (PCR), sequenced and analysed from both sense and antisense directions. Nonparametric one‐sample Kolmogorov–Smirnov test was used for distribution analysis; two independent samples t‐test and one‐way anova was performed for two groups and three groups analyses, respectively. Results and discussion: Plasma‐DPD activities in the 142 cancer patients followed a Gaussian distribution. The mean plasma‐DPD activity in women was lower than that in men (P = 0·006). Four mutations, 85T>C(DPYD*9A), 1627A>G(DPYD*5), 1896T>C and 2194G>A(DPYD*6), were found in the 142 cancer patients. The following mutations reported by others were not detected: 61C>T, 62G>A, 74A>G, 1601G>A(DPYD*4), 1679T>G(DPYD*13), 1714C>G, 1897delC(DPYD*3) and IVS 14 + 1G>A. No significant correlation was found between three mutations [85T>C(DPYD*9A), 1627A>G (DPYD*5) and 1896T>C], and DPD activity was found. Conclusion: No clear correlation between the mutations studied and DPD activity could be established in this study. However, larger‐scale prospective studies are needed to better assess the reported genotype–phenotype correlations.     

Detection of dihydropyrimidine dehydrogenase deficiency before treatment by fluoropyrimidines

Numerous toxic side-effects, sometimes severe, are regularly reported in patients treated with 5-fluorouracil, and oral fluoropyrimidines, UFT and capecitabine, in metastatic and adjuvant setting. These toxic effects are due to a large interindividual variability of the metabolism, mainly depending on dihydropyrimidine dehydrogenase activity (DPD), the major enzyme of the catabolism of fluoropyrimidines. Thus, the patients with a DPD deficiency are at high risk of early severe acute toxicity, with this kind of drug. These toxic side-effects are potentially lethal. DPD deficiency frequencies, partial or complete, are about 3-5% and 0.2% respectively. They are most often due to a gene polymorphism. Different techniques for the detection of DPD deficiency before treatment have been reported: phenotypic, such as the plasma ratio of dihydrouracil/uracil, or genotypic, such as the detection of DPD gene variants, deleterious for enzyme activity. The pretherapeutic detection of DPD deficiency would permit to avoid almost every early acute toxic side-effects. We must emphasize that it is not merely a genetic result, since the detection of a deficiency most often does not contra-indicate the use of a fluoropyrimidine, but it must be combined with therapeutic advice.     

Pharmacokinetic studies of 5-fluorouracil and 5'-deoxy-5-fluorouridine in rats

The pharmacokinetics of 5-fluorouracil (FU) and its metabolic prodrug, 5'-deoxy-5-fluorouridine (dFUR), were investigated in 5- to 9-month-old rats without tumors. Intravenous bolus injections and infusions of FU (25-35 mg X kg-1) and dFUR (500-750 mg X kg-1) had activity against transplanted colon tumors in 2- to 4-month-old rats. Blood and plasma concentrations of FU and dFUR were analyzed by high-pressure liquid chromatography using 5-bromouracil as the internal standard. Free fractions of these drugs in plasma were indistinguishable from unity, indicating little or no protein binding. The area under the blood concentration-time profiles and the steady-state concentrations of unchanged dFUR were 40- to 100-fold higher than those of unchanged FU. The respective blood clearances of FU and dFUR were 44 and 18 ml X kg-1 X min-1 after i.v. bolus injections, which were significantly lower than the 108 and 26 ml X kg-1 X min-1 after infusion. FU clearance decreased when its infusion rate was increased from 25 to 50 mg X kg-1 X day-1. Renal clearances of both drugs remained the same after either route of administration. These data suggest that both drugs were eliminated by nonlinear kinetics and that their metabolism was saturated at a more rapid administration rate.(ABSTRACT TRUNCATED AT 250 WORDS)     

DPD functional tests in plasma,fresh saliva and dried saliva samples as predictors of 5-fluorouracil exposure and occurrence of drug-related severe toxicity

Objectiveto evaluate plasma and salivary uracil (U) to dihydrouracil (UH2) ratios as tools for predicting 5-fluorouracil systemic exposure and drug-related severe toxicity, and clinically validate the use of dried saliva spots (DSS) as an alternative sampling strategy for dihydropyrimidine dehydrogenase (DPD) deficiency assessment.MethodsPre-chemotherapy plasma, fresh saliva and DSS samples were obtained from gastrointestinal patients (N = 40) for measurement of endogenous U and UH2 concentrations by LC-MS/MS. A second plasma sample collected during 5FU infusion was used for 5FU area under the curve (AUC) determination by HPLC-DAD. Data on toxicity was reported according to CTCAE.Results15% of the patients developed severe 5FU-related toxicity, with neutropenia accounting for 67% of the cases. U, UH2 and [UH2,]/[U] were highly correlated between fresh and dried saliva samples (r_s = 0.960; r_s = 0.828; r_s = 0.910, respectively). 5FU AUC ranged from 11.3 to 37.31 mg h L⁻¹, with 46.2% of under-dosed and 10.3% over-dosed patients. The [UH2]/[U] ratios in plasma, fresh saliva and dried saliva samples were moderately correlated with 5FU AUC and adverse events grade, indicating a partial contribution of the variables to drug exposure (r = −0.412, r_s = −0.373, r_s = 0.377) and toxicity (r = −0.363, r_s = −0.523, r_s = 0.542). Metabolic ratios were lower in patients with severe toxicity (P < .01 salivary ratios, and P < .5 plasma ratios), and 5FU AUC were in average 47% higher in this group than in moderate toxicity. The diagnostic performance of [UH2]/[U] ratios in fresh saliva and DSS for the identification of patients with severe toxicity were comparable.ConclusionsThe [UH2]/[U] metabolic ratios in plasma, fresh saliva and DSS were significantly associated with 5FU systemic exposure and toxicity degree. This study also demonstrated the applicability of DSS as alternative sampling for evaluating DPD activity.     

Endogenous metabolic markers for predicting the activity of dihydropyrimidine dehydrogenase

Five‐fluorouracil (5‐FU) is a chemotherapeutic agent that is mainly metabolized by the rate‐limiting enzyme dihydropyrimidine dehydrogenase (DPD). The DPD enzyme activity deficiency involves a wide range of severities. Previous studies have demonstrated the effect of a DPYD single nucleotide polymorphism on 5‐FU efficacy and highlighted the importance of studying such genes for cancer treatment. Common polymorphisms of DPYD in European ancestry populations are less frequently present in Koreans. DPD is also responsible for the conversion of endogenous uracil (U) into dihydrouracil (DHU). We quantified U and DHU in plasma samples of healthy male Korean subjects, and samples were classified into two groups based on DHU/U ratio. The calculated DHU/U ratios ranged from 0.52 to 7.12, and the two groups were classified into the 10th percentile and 90th percentile for untargeted metabolomics analysis using liquid chromatography‐quantitative time‐of‐flight‐mass spectrometry. A total of 4440 compounds were detected and filtered out based on a coefficient of variation below 30%. Our results revealed that six metabolites differed significantly between the high activity group and low activity group (false discovery rate q‐value < 0.05). Uridine was significantly higher in the low DPD activity group and is a precursor of U involved in pyrimidine metabolism; therefore, we speculated that DPD deficiency can influence uridine levels in plasma. Furthermore, the cutoff values for detecting DPD deficient patients from previous studies were unsuitable for Koreans. Our metabolomics approach is the first study that reported the DHU/U ratio distribution in healthy Korean subjects and identified a new biomarker of DPD deficiency.

Study Highlights

• WHAT IS THE CURRENT KNOWLEDGE ON THE TOPIC?

Dihydropyrimidine dehydrogenase (DPD) deficiency can cause severe 5‐fluorouracil toxicity. To predict DPD activity, DPYD genotyping and DPD phenotyping using dihydrouracil and uracil ratio were used.

• WHAT QUESTION DID THIS STUDY ADDRESS?

This study aimed to identify the distribution of DPD activity in a Korean population and explore new biomarkers of DPD activity using untargeted metabolomics.

• WHAT DOES THIS STUDY ADD TO OUR KNOWLEDGE?

This study recognized different distributions of DPD activity between a Korean population and populations of other ethnicities. The cutoff values for activity deficiency based on other ethnic groups could not be considered for East Asian populations, including Korean populations.

• HOW MIGHT THIS CHANGE CLINICAL PHARMACOLOGY OR TRANSLATIONAL SCIENCE?

This study indicated that a new cutoff value should be further validated to overcome the variability in DPD phenotyping in East Asian populations. The new biomarker for DPD deficiency uridine has the potential for more feasible and convenient prediction analysis.     

Chronotherapy for cancer

Cancer chronotherapy is attracting attention as a novel and logical therapy in which anti-cancer drugs are administered with optimal timing according to circadian rhythms of anti-cancer action and those of adverse effects on normal cells. Advances in chronobiology have identified the suprachiasmatic nucleus (SCN) as the center of biological rhythms and the area in which clock genes such as PER1, PER2, PER3, CLOCK, BMAL1, TIM, CRY1, CRY2, tau act to generate and coordinate biological rhythms. These findings have led to the development of chronotherapy. Clinically, patients with advanced gastrointestinal cancer have been treated by chronomodulated chemotherapy with good response. For colorectal cancer patients with unresectable liver metastases, chronotherapy with ℓ-OHP + 5–FU + FA (folinic acid) has been reported to allow complete surgical resection of liver metastases, resulting in 39–50% 5–year survival. Many believe that chronotherapy will become accepted as a refined and advantageous therapeutic option for not only cancer but also for other diseases, due to its universally applicable principles.     

A phase I study of oral uracil-tegafur prior to weekly intravenous gemcitabine in patients with advanced pancreatic cancer

BACKGROUND: Gemcitabine is widely accepted as the first-line agent for advanced pancreatic cancer. The antitumor cell activity of gemcitabine is higher when administered after 5-fluorouracil (5-FU) rather than before 5-FU in an in vitro study. The present study was conducted to define the maximum tolerated dose and dose-limiting toxicity associated with an oral fluoropyrimidine prodrug that combines uracil and tegafur (UFT), given prior to weekly intravenous gemcitabine in patients with advanced pancreatic cancer. METHODS: Over a 21-day cycle, gemcitabine was given intravenously over 30 min on days 8 and 15, while UFT was given orally from days 1 to 14. The dose of UFT used was 400 mg per day, given as two doses. The dose of gemcitabine was escalated in a stepwise fashion from 800 (level 1, n = 3) to 900 mg/m2 (level 2, n = 6) and then to 1,000 mg/m2 (level 3, n = 3), such that totally 12 patients received the combination chemotherapy. RESULTS: During the first cycle, grade 3 leukopenia was observed in 2 patients at dose level 1. Only 1 patient treated at dose level 2 experienced dose-limiting toxicity (grade 3 elevated transaminase), including additional patients treated at this dose level. No grade 3/4 toxicities occurred in patients treated at dose level 3. A significant response was observed in 1 out of 12 patients (8.3%). Seven patients (58.3%) had stable disease, while 4 patients (33.3%) showed disease progression. CONCLUSIONS: The combination chemotherapy of oral UFT and gemcitabine was convenient, well tolerated and may benefit patients with advanced pancreatic cancer. Doses recommended for further study of this schedule are gemcitabine 1,000 mg/m2 and UFT 400 mg/day.     

Prediction of nanoparticle prodrug metabolism by pharmacokinetic modeling of biliary excretion

Pharmacokinetic modeling and simulation is a powerful tool for the prediction of drug concentrations in the absence of analytical techniques that allow for direct quantification. The present study applied this modeling approach to determine active drug release from a nanoparticle prodrug formulation. A comparative pharmacokinetic study of a nanoscale micellar docetaxel (DTX) prodrug, Procet 8, and commercial DTX formulation, Taxotere, was conducted in bile duct cannulated rats. The nanoscale (~ 40 nm) size of the Procet 8 formulation resulted in confinement within the plasma space and high prodrug plasma concentrations. Ex vivo prodrug hydrolysis during plasma sample preparation resulted in unacceptable error that precluded direct measurement of DTX concentrations. Pharmacokinetic modeling of Taxotere and Procet 8 plasma concentrations, and their associated biliary metabolites, allowed for prediction of the DTX concentration profile and DTX bioavailability, and thereby evaluation of Procet 8 metabolism.     

The use of 19F spectroscopy and diffusion-weighted MRI to evaluate differences in gene-dependent enzyme prodrug therapies.

To evaluate noninvasive measures of gene expression and tumor response in a gene-dependent enzyme prodrug therapy (GDEPT), a bifunctional fusion gene between Saccharomyces cerevisiae cytosine deaminase (CD) and Haemophilus influenzae uracil phosphoribosyltransferase (UPRT) was constructed. CD deaminates 5-fluorocytosine (5FC) to 5-fluorouracil (5FU), and UPRT subsequently converts 5FU to fluorouridine monophosphate, and both of these reactions can be monitored noninvasively in vitro and in vivo using 19F magnetic resonance spectroscopy (MRS). Following transient transfection the CD-UPRT fusion protein exhibited both UPRT and CD enzymatic activities as documented by 19F MRS. In addition, an increase in CD activity and thermal stability was witnessed for the fusion protein compared to native CD. Stable expression of CD-UPRT in 9L glioma cells increased both 5FC and 5FU sensitivity in vitro compared to CD-expressing and wild-type 9L cells. Noninvasive 19F MRS of both CD and UPRT gene function in vivo demonstrated that in animals bearing CD-expressing tumors there was limited conversion of 5FC to 5FU with no measurable accumulation of cytotoxic fluorinated nucleotides (F-nucs). In contrast, CD-UPRT-expressing tumors had increased CD gene activity with a threefold higher intratumoral accumulation of 5FU and significant generation of F-nucs. Finally, CD-UPRT yielded increased efficacy in an orthotopic animal model of high-grade glioma. More importantly, early changes in cellular water mobility, which are felt to reflect cellular death, as measured by diffusion-weighted MRI, were predictive of both durable response and increased animal survival. These results demonstrate the increased efficacy of the CD-UPRT GDEPT compared to CD alone both biochemically and in a preclinical model and validate both 19F MRS and diffusion-weighted MRI as tools to assess gene function and therapeutic efficacy.     

Markers of bone resorption--measurement in serum, plasma or urine?

OBJECTIVE: We compared an established urine marker (total deoxypyridinoline (DPD), related to creatinine (cr)) with a plasma marker (CTX) to evaluate whether the methods are equally suited to detect increased bone resorption in women after the menopause and to see whether both markers show normal bone resorption in postmenopausal women on hormone replacement therapy (HRT). METHODS: DPD in first morning void urines was measured by an automated HPLC system. CTX ("beta-CrossLaps") was measured on the automated electrochemiluminescence analyzer E170 (Roche Diagnostics, Germany). For CTX, EDTA plasma and serum samples taken from fasting patients in the morning between 08.00 and 08.30 were analyzed. 49 women were premenopausal, 43 women were postmenopausal without HRT, and 13 women were postmenopausal on HRT (mostly on oral medication) for more than six months. RESULTS AND DISCUSSION: Inter-assay coefficients of variation (CVs) at three different concentrations were 6.0%, 6.7% and 7.2% for the assay of DPD and 2.58%, 1.83% and 1.99% for CTX, respectively. CTX was more stable in EDTA plasma than in serum. 21/43 (49%) of postmenopausal women without HRT showed increased DPD/cr ratios and 19/43 (44%) showed elevated CTX concentrations. Regarding postmenopausal women on HRT, DPD/cr ratios were elevated in 3/13 women, whereas plasma CTX showed levels within the premenopausal range in all 13 women. It is discussed that in some cases a lower muscle mass as a result of increasing age or as a result of oral HRT might increase the urinary DPD/cr ratio by lowered excretion of cr. This effect would raise the number of cases with an elevated DPD/cr ratio after the menopause out of proportion. CONCLUSION: CTX is determined with very high precision on the E170. CTX, if measured in EDTA plasma samples from fasting patients in the morning, seems to indicate bone resorption in women on HRT correctly as normal. The DPD/cr ratio in urine of women on HRT is increased in some cases above normal, presumably by lowered excretion of cr. According to our results, plasma (or serum) markers of bone resorption seem to be preferable over cr-related urine markers.     

Stability studies on admixtures of 5-fluorouracil with carboplatin and 5-fluorouracil with heparin for administration in continuous infusion regimens

The therapeutic index of several anticancer agents may be improved by replacing rapid infusion/bolus injection schedules with prolonged continuous infusion regimens. Admixtures of 5-fluorouracil (5FU) with carboplatin and 5FU with heparin were subjected to stability studies to establish the feasibility of administering these infusions on an in-patient and out-patient basis, respectively.
In the first study the stability of carboplatin was determined in an admixture of carboplatin and 5FU for neoadjuvant treatment of in-patients with oesophageal carcinoma by 5-day infusion. A previous study had reported significant carboplatin degradation in 5FU/carboplatin admixtures. Our results were consistent with this study and demonstrated that under ward conditions (25°C) carboplatin also degraded (16% in 24h) in dilute admixtures with 5FU. However, the addition of a citric acid buffer, which reduced infusion pH from 8.65 to 6.5, increased the stability of carboplatin (4.8% degradation in 24h), without compromising 5FU solubility or stability.
In a second study, the stability of an infusion containing 5FU and heparin was determined. Prolonged continuous infusion is routinely used for adjuvant treatment of colorectal carcinoma but episodes of thromboses and occlusion of the central venous catheter have been associated with this treatment. The inclusion of heparin in the infusion was advocated to overcome these difficulties and the purpose of this study was to assess the stability of this admixture for ambulatory use. An infusion of 5FU and heparin was stable (>5% degradation of either drug) in prefilled syringes under storage conditions (4°C) for 14 days and under 'in-use' conditions (37°C) for at least 7 days.     

Six-week randomized controlled trial to compare the tolerabilities, pharmacokinetics, and antiviral activities of GW433908 and amprenavir in human immunodeficiency virus type 1-infected patients

This study compared the plasma amprenavir pharmacokinetics of the human immunodeficiency virus (HIV) protease inhibitors amprenavir (Agenerase) 1,200 mg twice daily (BID) and the amprenavir prodrug GW433908, a formulation that substantially reduces the number of tablets per dose compared with amprenavir, at doses of 1,395 mg and 1,860 mg BID, in combination with abacavir 300 mg BID and lamivudine 150 mg BID in patients with HIV infection. Overall, 78 patients received study treatment. Compared with amprenavir 1,200 mg BID, both GW433908 1,395 mg BID and GW433908 1,860 mg BID delivered equivalent steady-state (ss) values for area under the plasma amprenavir concentration-time curve (AUC) at the end of a dosing interval (tau), lower maximum plasma amprenavir concentrations (30% lower), and higher plasma amprenavir concentrations at the end of a dosing interval (28% higher for GW433908 1,395 mg BID and 46% higher for GW433908 1,860 mg BID). Time-variant plasma amprenavir pharmacokinetics were observed with reductions in plasma amprenavir exposure over the first 4 weeks of dosing; the decrease in plasma amprenavir AUC(tau,ss) versus the AUC from 0 h to infinity was 27% for GW43308 1,395 mg, 45% for GW433908 1,860 mg, and 23% for amprenavir 1,200 mg. All three regimens reduced plasma HIV-1 RNA ( approximately 2 log(10) copies/ml) and increased CD4(+) cell counts ( approximately 100 cells/mm(3)) over the initial 28 days. Adverse event profiles were consistent with those previously reported for amprenavir. Although not statistically tested, the GW433908 groups appeared to have fewer gastrointestinal symptoms. In conclusion, the protease inhibitor GW433908 delivered comparable plasma amprenavir concentrations to those delivered by amprenavir 1,200 mg BID. GW433908, in combination with abacavir and lamivudine, demonstrated potent antiviral activity and was generally well tolerated over a 4-week period.     

Pharmacokinetics of bis(t-butyl-SATE)-AZTMP, a bispivaloylthioethyl prodrug for intracellular delivery of zidovudine monophosphate, in mice

The pharmacokinetics of a bispivaloylthioethyl prodrug of zidovudine monophosphate (AZTMP), bis(t-butyl-SATE)-AZTMP, and intracellular conversion of the prodrug to AZTMP were characterized following intravenous (i.v.) and oral (p.o.) administration of the prodrug to mice. Concentrations of bis(t-butyl-SATE)-AZTMP, AZTMP and zidovudine (AZT) in blood, red blood cells, plasma, brain and lymph nodes were determined by HPLC. Following i.v. administration of bis(t-butyl-SATE)-AZTMP, concentrations of the prodrug declined rapidly with low levels of the prodrug detected until 4 h. Both bis(t-butyl-SATE)-AZTMP and AZTMP were detected in brain 3 min after dosing. AZTMP was found in both plasma and peripheral red blood cells, peaking at approximately 30 min and remaining detectable until 2 h. No AZTMP was detected in lymph nodes. Compared to the pharmacokinetics of AZT following its i.v. administration, i.v. administration of bis(t-butyl-SATE)-AZTMP produced lower peak concentrations of AZT in plasma, peripheral red blood cells, brain and lymph nodes. However, terminal half-lives of AZT were significantly prolonged following administration of the prodrug. Following p.o. administration of bis(t-butyl-SATE)-AZTMP, neither the prodrug nor AZTMP were detectable in whole blood. The conversion of AZT from bis(t-butyl-SATE)-AZTMP in plasma and peripheral red blood cells following p.o administration was 12.1% of that following i.v. administration of the prodrug. Bis(t-butyl-SATE)-AZTMP demonstrated promising potential for intracellular delivery of AZTMP. The prodrug also prolonged the retention of AZT in mice, and particularly increased delivery of AZT to the lymphatic and central nervous systems.     

In vivo potentiation of 5-fluorouracil by leucovorin in murine colon carcinoma

In vitro results have clearly demonstrated that leucovorin (LV) can enhance the growth inhibitory effects of 5-fluorouracil (5FU) but in vivo potentiation of the antitumor effect of 5FU by LV has not yet been defined in animal models. The antitumor effect and the toxicity of the LV-5FU combination was studied in mice bearing the colon carcinomas, Colon 26 and Colon 38. Mice were treated weekly with 5FU at the maximum tolerated dose (100 mg/kg) alone or with LV at different doses and schedules. Pretreatment with LV followed 1 hr later by a second LV injection together with 5FU clearly potentiated the antitumor effect of 5FU in both murine tumor lines. Comparable results were obtained with total LV doses of 100 and 200 mg/kg. The effect of 5FU pretreatment was studied by randomization of 5FU pretreated Colon 38-bearing mice in 2 groups, one treated with 5FU and the other with LV-LV + 5FU. Again, LV potentiated the effect of 5FU. Also in a Colon 38 tumor which had developed resistance against 5FU and which was reimplanted, LV potentiated the antitumor activity of 5FU. Weight loss of the combination was slightly higher than for 5FU alone. A moderate leukopenia (nadir 40%) and mild anemia were observed, which were less than for 5FU alone. The combination did not cause thrombocytopenia. In conclusion, LV can potentiate the therapeutic efficacy of 5FU in murine colon carcinoma.     

Combined systemic chronotherapy and hepatic artery infusion for the treatment of metastatic colorectal cancer confined to the liver

BACKGROUND: The optimal treatment of patients with metastatic colorectal cancer is still a clinical challenge. We describe the use of combined hepatic arterial infusion (HAI) of irinotecan (CPT-11) in conjunction with systemic chronotherapy infusion of 5-fluorouracil (5FU), folinic acid and carboplatin in patients with colorectal liver metastases. METHODS: Twenty-three patients with colorectal cancer and isolated liver metastases were enrolled in this trial. Intraoperative insertion of an intra-arterial catheter into the hepatic artery was accomplished during the colon operation (in cases of synchronous tumor) or as a separate procedure in colorectal cancer patients with newly diagnosed liver metastases. A systemic double-lumen double-chamber port was inserted via the subclavian vein as a separate procedure. The treatment plan included irinotecan given by intra-arterial infusion at 150 mg/m2 for 1 h. After 2 weeks of rest chronomodulated 5FU (700 mg/m(2); peak delivery rate at 04:00 h), leucovorin (175 mg/m2; peak delivery rate at 04:00 h) and carboplatin (40 mg/m2; peak delivery rate at 16:00 h) for 4 days was followed by 10 days' rest and then given again. After 10 days' rest another HAI was introduced using the same method. Each cycle of therapy included 2 HAI courses and 2 chronotherapy courses in between. After 2 complete cycles, patients were evaluated for their response with weekly accessed toxicity recording. RESULTS: Seven women, 8 men, median age 61 years (range 46-72). Eight patients had synchronous colon and hepatic disease and 7 patients had metachronous disease. Ten patients had previously been treated with 5FU and leucovorin while 5 patients were chemonaive. The mean number of cycles were 11.6 per patient (range 8-19). Partial response was achieved in 6 patients (40%) and was followed by laparoscopic radiofrequency ablation in 5 patients (33%). Disease stabilization was observed in 2 patients (13%) and disease progression in 7 patients (47%) mainly after previous chemotherapy failure. Side effects were infrequent and mild including grade 2 GIT complaints (5 patients), RUQ pain during HAI (9 patients) and grade 2 hematological complaints in 2 patients. CONCLUSION: A combined chemotherapy protocol (HAI and chronotherapy) with irinotecan (CPT-11) together with chronomodulated infusion of 5FU, folinic acid and carboplatin can be used in metastatic colorectal patients with a high efficacy rate and minor side effects especially in pretreated patients.     

The value of dihydrouracil/uracil plasma ratios in predicting 5-fluorouracil-related toxicity in colorectal cancer patients

This study investigated the relationship between the dihydrouracil/uracil (UH(2)/U) plasma ratio, a surrogate marker of dihydropyrimidine dehydrogenase (DPD) activity, and 5-fluorouracil (5-FU)-related early toxicity. Plasma UH(2)/U ratios were determined in 68 colorectal cancer patients and 100 healthy controls. A cut-off value indicative of DPD deficiency was calculated using receiver operator characteristics. Patients experiencing toxicity were screened for the DPD G-to-A point mutation within the 5'-splicing donor site of intron 14 (IVS14+1G>A). Overall, 24/68 patients (35%) experienced toxicity (all grades) and abnormal UH(2)/U ratios were demonstrated in 21/24 (87.5%) patients. Drug concentrations up to 130 times the recommended level were found in 13/24 (54%) patients experiencing toxicity. One patient experiencing toxicity was a heterozygous carrier of the IVS14+1G>A mutation. A low UH(2)/U plasma ratio had a sensitivity of 0.87 and specificity of 0.93 for predicting 5-FU-induced toxicity. Systematic detection of DPD-deficient patients using the UH(2)/U ratio could optimize 5-FU-based chemotherapy and minimize life-threatening toxicity.     

Identification of GS 4104 as an Orally Bioavailable Prodrug of the Influenza Virus Neuraminidase Inhibitor GS 4071

GS 4071 is a potent carbocyclic transition-state analog inhibitor of influenza virus neuraminidase with activity against both influenza A and B viruses in vitro. GS 4116, the guanidino analog of GS 4071, is a 10-fold more potent inhibitor of influenza virus replication in tissue culture than GS 4071. In this study we determined the oral bioavailabilities of GS 4071, GS 4116, and their respective ethyl ester prodrugs in rats. Both parent compounds and the prodrug of the guanidino analog exhibited poor oral bioavailability (2 to 4%) and low peak concentrations in plasma (C_maxs; C_max <0.06 μg/ml). In contrast, GS 4104, the ethyl ester prodrug of GS 4071, exhibited good oral bioavailability (35%) as GS 4071 and high C_maxs of GS 4071 (C_max = 0.47 μg/ml) which are 150 times the concentration necessary to inhibit influenza virus neuraminidase activity by 90%. The bioavailability of GS 4104 as GS 4071 was also determined in mice (30%), ferrets (11%), and dogs (73%). The plasma of all four species exhibited high, sustained concentrations of GS 4071 such that at 12 h postdosing the concentrations of GS 4071 in plasma exceeded those necessary to inhibit influenza virus neuraminidase activity by 90%. These results demonstrate that GS 4104 is an orally bioavailable prodrug of GS 4071 in animals and that it has the potential to be an oral agent for the prevention and treatment of influenza A and B virus infections in humans.     

The plasma and intracellular steady-state pharmacokinetics of lopinavir/ritonavir in HIV-1-infected patients

Therapeutic drug monitoring of protease inhibitors (PIs) is usually performed on plasma samples although their antiretroviral effect takes place inside cells. Little is known, however, about the intracellular accumulation and related plasma pharmacokinetics of PIs such as lopinavir/ritonavir (LPV/RTV). Therefore, we studied the plasma and intracellular (cell-associated) steady-state pharmacokinetics of this PI combination in a dosage of 400/100 mg twice daily in a non-randomized cohort of HIV-1-infected individuals. Plasma (0-12 h) and peripheral blood mononuclear cell (PBMC; 0-8 h) samples were drawn during a 12-h dosing interval in 11 subjects. The plasma concentrations versus time curves of LPV and RTV were characterized by an irregular absorption phase showing double-peaks (Cmax) in most subjects and single-peaks in the remaining patients between 1 and 3 h after drug intake. Pre-dose concentrations of both agents in plasma were significantly higher than the concentrations at the end of the dosing interval indicating the presence of a circadian rhythm in their pharmacokinetics. The course of the intracellular concentrations versus time curves appeared to be similar to the plasma concentration curves, with the highest intracellular concentration measured 3 h after drug intake. The intracellular RTV concentrations were higher than reported in vitro EC50 values and might therefore contribute to the antiretroviral effect of LPV/RTV. The median intracellular-to-plasma concentration ratios (interquartile range) were 1.18 (0.74-2.06) and 4.59 (3.20-7.70) for LPV and RTV, respectively. In conclusion, both LPV and RTV accumulate to potential therapeutic concentrations in PBMCs. Irregular absorption and circadian plasma clearance patterns were observed for the PI combination LPV/RTV.     

Capecitabine: a review

BACKGROUND: Fluorouracil (FU) is an antimetabolite with activity against numerous types of neoplasms, including those of the breast, esophagus, larynx, and gastrointestinal and genitourinary tracts. Systemic toxicity, including neutropenia, stomatitis, and diarrhea, often occur due to cytotoxic nonselectivity. Capecitabine was developed as a prodrug of FU, with the goal of improving tolerability and intratumor drug concentrations through tumor-specific conversion to the active drug. OBJECTIVES: The purpose of this article is to review the available information on capecitabine with respect to clinical pharmacology, mechanism of action, pharmacokinetic and pharmacodynamic properties, clinical efficacy for breast and colorectal cancer adverse-effect profile, documented drug interactions, dosage and administration, and future directions of ongoing research. METHODS: Relevant English-language literature was identified through searches of PubMed (1966 to August 2004), International Pharmaceutical Abstracts (1977 to August 2004), and the Proceedings of the American Society of Clinical Oncology (January 1995 to August 2004). Search terms included capecitabine, Xeloda, breast cancer, and colorectal cancer. The references of the identified articles were reviewed for additional sources. In addition, product information was obtained from Roche Pharmaceuticals. Studies from the identified literature that addressed this article's objectives were selected for review, with preference given to Phase II/III trials. RESULTS: Capecitabine is an oral prodrug that is converted to its only active metabolite, FU, by thymidine phosphorylase. Higher levels of this enzyme are found in several tumors and the liver, compared with normal healthy tissue. In adults, capecitabine has a bioavailability of approximately 100% with a Cmax of 3.9 mg/L, Tmax of 1.5 to 2 hr, and AUC of 5.96 mg.h/L. The predominant route of elimination is renal, and dosage reduction of 75% is recommended in patients with creatinine clearance (CrCl) of 30 to 50 mL/min. The drug is contraindicated if CrCl is < 30 mL/min. Capecitabine has shown varying degrees of efficacy with acceptable tolerability in numerous cancers including prostate, renal cell, ovarian, and pancreatic, with the largest amount of evidence in metastatic breast and colorectal cancer. Single-agent capecitabine was compared with IV FU/leucovorin (LV) using the bolus Mayo Clinic regimen in 2 Phase III trials as first-line treatment for patients with metastatic colorectal cancer. Overall response rate (RR) favored the capecitabine arm (26% vs 17%, P < 0.001); however, this did not translate into a difference in time to progression (TTP) (4.6 months vs 4.7 months) or overall survival (OS) (12.9 months vs 12.8 months). In Phase II noncomparative trials, combinations of capecitabine with oxaliplatin or irinotecan have produced results similar to regimens combining FU/LV with the same agents in patients with colorectal cancer. In metastatic breast cancer patients who had received prior treatment with an anthracycline-based regimen, a Phase III trial comparing the combination of capecitabine with docetaxel versus docetaxel alone demonstrated superior objective tumor RR (42% vs 30%, P = 0.006), median TTP (6.1 months vs 4.2 months, P < 0.001), and median OS (14.5 months vs 11.5 months, P = 0.013) with the combination treatment. Noncomparative Phase II studies have also supported efficacy in patients with metastatic breast cancer pretreated with both anthracyclines and taxanes, yielding an overall RR of 15% to 29% and median OS of 9.4 to 15.2 months. The most common dose-limiting adverse effects associated with capecitabine monotherapy are hyperbilirubinemia, diarrhea, and hand-foot syndrome. Myelosuppression, fatigue and weakness, abdominal pain, and nausea have also been reported. Compared with bolus FU/LV, capecitabine was associated with more hand-foot syndrome but less stomatitis, alopecia, neutropenia requiring medical management, diarrhea, and nausea. Capecitabine has been reported to increase serum phenytoin levels and the international normalized ratio in patients receiving concomitant phenytoin and warfarin, respectively. The dose of capecitabine approved by the US Food and Drug Administration (FDA) for both metastatic colorectal and breast cancer is 1250 Mg/M2 given orally twice per day, usually separated by 12 hours for the first 2 weeks of every 3-week cycle. CONCLUSIONS: Capecitabine is currently approved by the FDA for use as first-line therapy in patients with metastatic colorectal cancer when single-agent fluoropyrimidine therapy is preferred. The drug is also approved for use as (1) a single agent in metastatic breast cancer patients who are resistant to both anthracycline- and paclitaxel-based regimens or in whom further anthracycline treatment is contra indicated and (2) in combination with docetaxel after failure of prior anthracycline-based chemotherapy. Single-agent and combination regimens have also shown benefits in patients with prostate, pancreatic, renal cell, and ovarian cancers. Improved tolerability and comparable efficacy compared with IV FU/LV in addition to oral administration make capecitabine an attractive option for the treatment of several types of cancers as well as the focus of future trials.     

Relationship between soluble thrombomodulin in plasma and coagulation or fibrinolysis in type 2 diabetes

Serum concentration of soluble thrombomodulin (TM) is thought to be a marker for endothelial damage. Although several studies have reported that serum TM concentrations are increased in patients with diabetes mellitus, there is little information on the physiological function of soluble TM in human plasma. To evaluate the relationship of soluble TM in plasma between coagulation and/or fibrinolysis system in patients with diabetes, we measured plasma soluble TM, protein C activity (a natural anticoagulant induced by thrombin-TM complex), prothrombin F1+2 (a direct marker of thrombin generation), and plasmin-alpha 2-antiplasmin complex (PAP) and D dimer (measures of fibrinolytic activity) in 55 patients with type 2 diabetes mellitus. The plasma concentrations of soluble TM (P<0.01), protein C activity (P<0.01), prothrombin F1+2 (P<0.05), PAP (P<0.001) and D dimer (P<0.001) were significantly higher in the diabetic patients than the 48 age-matched control subjects. The plasma concentrations of TM and PAP were obviously increased in patients with diabetic nephropathy. In the diabetic patients, the plasma concentrations of soluble TM were inversely correlated with the protein C activity (r=-0.43, P<0.005), and were positively correlated with the plasma concentrations of prothrombin F1+2 (r=0.63, P<0.0001) and the plasma PAP concentrations (r=0.30, P<0.05). The present study demonstrated that both coagulation and fibrinolysis are enhanced concomitantly in patients with type 2 diabetes mellitus, and that an increase in plasma concentration of soluble TM is associated not only with hypercoagulability but also with enhanced fibrinolysis in diabetic patients.