A simple and rapid high-performance liquid chromatographic (HPLC) method for 5-fluorouracil (5-FU) assay in plasma and possible detection of patients with impaired dihydropyrimidine dehydrogenase (DPD) activity

Partial protein binding of uracil and thymine affects accurate dihydropyrimidine dehydrogenase (DPD) phenotyping

Fluorouracil is among the most used antimetabolite drugs for the chemotherapeutic treatment of various types of gastrointestinal malignancies. Dihydropyrimidine dehydrogenase (DPYD) genotyping prior to fluorouracil treatment is considered standard practice in most European countries. Yet, current pre-therapeutic DPYD genotyping procedures do not identify all dihydropyrimidine dehydrogenase (DPD)-deficient patients. Alternatively, DPD activity can be estimated by determining the DPD phenotype by quantification of plasma concentrations of the endogenous uracil and thymine concentrations and their respective metabolites dihydrouracil (DHU) and dihydrothymine (DHT). Liquid chromatography - mass spectrometry (LC-MS) detection is currently considered as the most adequate method for quantification of low-molecular weight molecules, although the sample preparation method is highly critical for analytical outcome. It was hypothesized that during protein precipitation, the recovery of the molecule of interest highly depends on the choice of precipitation agent and the extent of protein binding in plasma. In this work, the effect of protein precipitation using acetonitrile (ACN) compared to strong acid perchloric acid (PCA) on the recovery of uracil, thymine, DHU and DHT is demonstrated. Upon the analysis of plasma samples, PCA precipitation showed higher concentrations of uracil and thymine as compared to ACN precipitation. Using ultrafiltration, it was shown that uracil and thymine are significantly (60-65 %) bound to proteins compared to DHU and DHT. This shows that before harmonized cut-off levels of DPD phenotyping can be applied in clinical practice, the analytical methodology requires extensive further optimization.

Synthesis, in silico studies, and in vitro biological evaluation of newly-designed 5-amino-1H-tetrazole-linked 5-fluorouracil analog as a potential antigastric-cancer agent

5-Fluorouracil (5FU) is a chemotherapy drug used to treat various cancers, such as colorectal, prostate, skin, pancreas, and stomach, as an ointment or solution. However, its consumption has several side effects. Therefore, a new derivative of fluorouracil containing 5-Amino-1H-tetrazole was designed and synthesized through multi-step synthesis to reduce urea excretion and toxicity. The effectiveness of the synthesized drug on the Adenocarcinoma gastric cell line (AGS) gastric cancer cell line was evaluated using the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) test, which showed that the new 5-fluorouracil (5FU) analog, with an IC50 of 15.67 µg/mL, is more effective in inhibiting the proliferation of AGS cells after 24 h compared to both synthesized and reported 5FU. In addition, In-silico studies showed that the new 5FU derivative based on amino tetrazole, with a binding energy of -7.2 kcal/mol, exhibits greater anti-cancer activity against the BCL2 enzyme than 5FU, with a binding energy of - 4.8 kcal/mol. It is predicted that the new 5FU derivative will be effective in treating gastric and colorectal cancers. The new derivative of the 5-fluorouracil drug was characterized and identified using FTIR and NMR spectroscopy.Communicated by Ramaswamy H. Sarma.

HSPiP, Computational Modeling, and QbD-Assisted Optimized Method Validation of 5-Fluorouracil for Transdermal Products

This study addressed the simplest and most efficient HPLC (high-performance liquid chromatography) method for the estimation of 5-fluorouracil (5-FU) from rat blood plasma by implementing the Hansen solubility parameters (HSP), computation prediction program, and QbD (quality by design) tool. The mobile phase selection was based on the HSP predictions and experimental data. The Taguchi model identified seven variables (preoptimization) to screen two factors (mobile phase ratio as A and column temperature as B) at three levels as input parameters in "CCD (central composite design)" optimization (retention time as Y1 and peak area as Y2). The stability study (freeze-thaw cycle and short- and long-term stability) was conducted in the rat plasma. Results showed that HSPiP-based HSP values and computational model-based predictions were well simulated with the experimental solubility data. Acetonitrile (ACN) was relatively suitable over methanol as evidenced by the experimental solubility value, HSP predicted parameters (δh of 5-FU - δh of ACN = 8.3-8.3 = 0 as high interactive solvent whereas δh of 5-FU - δh of methanol = 8.3-21.7 = -13.4), and instrumental conditions. CCD-based dependent variables (Y1 and Y2) exhibited the best fit of the model as evidenced by a high value of combined desirability (0.978). The most robust method was adopted at A = 96:4 and B = 40 °C to get earlier Y1 and high Y2 as evidenced by high desirability (D) = 0.978 (quadratic model with p < 0.0023). The estimated values of LLOD and LLOQ were found to be 0.11 and 0.36 μg/mL, respectively with an accuracy range of 94.4-98.7%. Thus, the adopted method was the most robust, reliable, and reproducible methodology for pharmacokinetic parameters after the transdermal application of formulations in the rat.

Intestinal Microbiota: The Driving Force behind Advances in Cancer Immunotherapy

Simple Summary

Despite the great achievements of cancer immunotherapy in a variety of tumors, tumor heterogeneity and drug resistance still plague patients and clinical researchers. In particular, the occurrence of immune-related adverse events forces patients to discontinue cancer immunotherapy. Therefore, it is urgent to optimize cancer immunotherapy and improve the efficacy of immunotherapy. With the iteration of sequencing technology, the microbiome, as the second set of genomes in the body, has been proven to be involved in immunity and metabolism. More and more studies are gradually shifting the perspective to the intestinal microbiota and cancer immunotherapy. The intestinal microbiota reactivates and modulates immune cells in immunotherapy and is expected to become a biomarker for predicting immune efficacy. Targeting to improve the intestinal microbiota can enhance anti-tumor immunity. This advantage is beneficial to control related adverse symptoms and expand the beneficiary population of cancer immunotherapy. This finding can help clinicians comprehensively evaluate the effect of tumor screening and tumor treatment. Therefore, the innovative combination of gut microbiota and cancer immunotherapy is expected to be an active strategy to enhance individualized immune responses.

Abstract

In recent years, cancer immunotherapy has become a breakthrough method to solve solid tumors. It uses immune checkpoint inhibitors to interfere with tumor immune escape to coordinate anti-tumor therapy. However, immunotherapy has an individualized response rate. Moreover, immune-related adverse events and drug resistance are still urgent issues that need to be resolved, which may be attributed to the immune imbalance caused by immune checkpoint inhibitors. Microbiome research has fully revealed the metabolic-immune interaction relationship between the microbiome and the host. Surprisingly, sequencing technology further proved that intestinal microbiota could effectively intervene in tumor immunotherapy and reduce the incidence of adverse events. Therefore, cancer immunotherapy under the intervention of intestinal microbiota has innovatively broadened the anti-tumor landscape and is expected to become an active strategy to enhance individualized responses.

Testing for Dihydropyrimidine Dehydrogenase Deficiency to Individualize 5-Fluorouracil Therapy

Simple Summary

5-Fluorouracil (5-FU) is a chemotherapy drug that is commonly used to treat multiple cancers. Many people who are treated with 5-FU experience severe toxicity to the drug, and in severe cases, patients can die. This review discusses current methods for identifying people who are at high risk for severe side effects to 5-FU therapy.

Abstract

Severe adverse events (toxicity) related to the use of the commonly used chemotherapeutic drug 5-fluorouracil (5-FU) affect one in three patients and are the primary reason cited for premature discontinuation of therapy. Deficiency of the 5-FU catabolic enzyme dihydropyrimidine dehydrogenase (DPD, encoded by DPYD) has been recognized for the past 3 decades as a pharmacogenetic syndrome associated with high risk of 5-FU toxicity. An appreciable fraction of patients with DPD deficiency that receive 5-FU-based chemotherapy die as a result of toxicity. In this manuscript, we review recent progress in identifying actionable markers of DPD deficiency and the current status of integrating those markers into the clinical decision-making process. The limitations of currently available tests, as well as the regulatory status of pre-therapeutic DPYD testing, are also discussed.

Rapid analytical method development and validation for the simultaneous estimation of 5-Fluorouracil and Cannabidiol in plasma and lipid-based nanoformulations

Background:

5-Fluorouracil (5-FU) is a well-established anticancer drug. Several studies have also demonstrated the anticancer potential of Cannabidiol (CBD) against various malignancies, including skin cancer. Reported synergistic effects of this combination fascinate researchers to consider this for the management of skin cancer.

Methods:

A simple and robust HPLC method for simultaneous estimation of 5-FU and CBD at its single wavelength (237 nm) was developed and validated. The separation of these compounds was performed on Waters® HPLC system with Hypersil™ C18 RP-column using methanol and water in gradient flow as mobile phase. The method could effectively quantify the nanogram levels of both analytes simultaneously in plasma spiked samples and various nanoformulations. The analytical performance of the proposed method was validated in terms of various parameters, such as linearity, ruggedness, specificity, and few others.

Results:

5-FU as well as CBD were successfully detected at 237 nm with retention time 1.4 and 1.84 minutes respectively. Calibration curves were found to be linear with R2 values of 0.985 and 0.984 for 5-FU and CBD respectively. The method was linear, precise, specific and robust. Additionally, prepared method successfully employed in determining concentration of both drugs in combitorial nanoformulations.

Conclusion:

The findings show that the developed method was simple, reliable, sensitive and economical. It could be employed for the simultaneous estimation of 5-FU and CBD in various in vitro and in vivo studies.

Overcoming barriers to implementing precision dosing with 5-fluorouracil and capecitabine

Despite advances in targeted cancer therapy, the fluoropyrimidines 5-fluorouracil (5FU) and capecitabine continue to play an important role in oncology. Historically, dosing of these drugs has been based on body surface area. This approach has been demonstrated to be an imprecise way to determine the optimal dose for a patient. Evidence in the literature has demonstrated that precision dosing approaches, such as DPD enzyme activity testing and, in the case of intravenous 5FU, pharmacokinetic-guided dosing, can reduce toxicity and yield better patient outcomes. However, despite the evidence, there has not been uniform adoption of these approaches in the clinical setting. When a drug such as 5FU has been used clinically for many decades, it may be difficult to change clinical practice. With the aim of facilitating change of practice, issues and barriers to implementing precision dosing approaches for 5FU and capecitabine are identified and discussed with possible solutions proposed.

Application of smart solid lipid nanoparticles to enhance the efficacy of 5-fluorouracil in the treatment of colorectal cancer

5-Fluorouracil (5-FU) is a standard treatment option for colorectal cancer (CRC) but its rapid metabolism and systemic instability (short half-life) has hindered its therapeutic efficacy. The objective of this study was to develop a novel drug delivery system, solid lipid nanoparticle (SLN), capable of delivering high payload of 5-FU to treat CRC. The rational was to improve 5FU-nanocarrier compatibility and therapeutic efficacy. The SLN-loaded 5-FU was developed by utilizing a Strategic and unique Method to Advance and Refine the Treatment (SMART) of CRC through hot and cold homogenization approach. The SLN was made of unique PEGylated lipids and combination of the surfactants. Cytotoxicity studies, clonogenic assay, flow cytometry and confocal imaging were conducted to evaluate the effectiveness and cellular uptake of 5FU-SLN4 in HCT-116 cancer cells. Pharmacokinetic (PK) parameters and receptor expressions were determined while tumor efficacy studies were conducted on mouse bearing subcutaneous HCT-116 cancer. Among the all the formulations, 5FU-SLN4 was the most effective with particle size of was 263 ± 3 nm, zeta potential was 0.1 ± 0.02 and entrapment efficiency of 81 ± 10%. The IC50 value of 5FU-SLN4 (7.4 ± 0.02 µM) was 2.3 fold low compared with 5-FU (17.7 ± 0.03 µM). For tumor efficacy studies, 5FU-SLN4 significantly inhibited tumor growth in comparison to 5-FU while area-under plasma concentration-time curve (AUC) of 5FU-SLN4 was 3.6 fold high compared with 5-FU. HER2 receptors expression were markedly reduced in 5-FU-SLN4 treated mice compared with 5FU and liver and kidney tissues showed no toxicity at dose of 20 mg/kg. 5FU-SLN4 was highly cytotoxic against HCT-116 cells and significantly inhibited subcutaneous tumor growth in mice compared with 5-FU. This emphasizes the significance of developing a smart nano-delivery system to optimize the delivery efficiency of anticancer drugs to tumors.

Automatic quantification of uracil and dihydrouracil in plasma

Fluoropyrimidines-based chemotherapies are the backbone in the treatment of many cancers. However, the use of 5-fluorouracil and its oral pre-prodrug, capecitabine, is associated with an important risk of toxicity. This toxicity is mainly due to a deficiency of dihydropyrimidine dehydrogenase (DPD). This deficiency may be detected by using a phenotypic approach that consists in the measurement of uracilemia or the calculation of dihydrouracil (UH₂)/uracil (U) ratio. For uracilemia, a threshold value of 16 ng/ml has been proposed for partial deficiency, while a value of 150 ng/ml has been proposed for complete deficiency. We have developed a rapid, accurate and fully-automated procedure for the quantification of U and UH₂ in plasma. Sample extraction was carried out by a programmable liquid handler directly coupled to a liquid chromatography - tandem mass spectrometry (LC-MS/MS) system. The method was validated according to the EMA guidelines and ISO 15189 requirements and was applied to real patient samples (n = 64). The limit of quantification was 5 and 10 ng/ml for U and UH₂ respectively. Imprecision and inaccuracy were less than 15% for inter and intra-assay tests. Comparison with dedicated routine method showed excellent correlation. An automated procedure perfectly fulfills the need of low inaccuracy and CVs at the threshold values (less than 5% at 16 ng/ml) and is highly suitable for the characterization of DPD deficiency. Automatization should guaranty reliable and robust performances by minimizing the sources of variation such as volume inaccuracies, filtration or manual extraction related errors.

High-throughput method to analyze tegafur and 5-fluorouracil in human tears and plasma using hydrophilic interaction liquid chromatography/tandem mass spectrometry

RATIONALE

We developed a new high-throughput method to analyze tegafur (FT) and 5-fluorouracil (5-FU) in tear and plasma samples using hydrophilic interaction liquid chromatography (HILIC)/tandem mass spectrometry (MS/MS).

METHODS

The tear samples (10 μL) spiked with FT, 5-FU, and 5-chlorouracil (internal standard) were diluted using 40 μL of 2 M ammonium acetate and 250 μL of acetonitrile with 2% formic acid; 20 μL of plasma spiked with the two drugs and internal standard was diluted with 80 μL of 2 M ammonium acetate and 500 μL of acetonitrile with 2% formic acid. After centrifugation, the clear supernatant extract (15 μL) was directly injected into the HILIC/MS/MS instrument, and each drug was separated on a Unison UK-Amino column (50 mm × 3 mm i.d., 3 μm particle size) with a linear gradient elution system composed of 10 mM ammonium acetate (pH 6.8) and acetonitrile at a flow rate of 0.7 mL/min. We performed quantification by multiple reaction monitoring (MRM) with negative-ion atmospheric-pressure chemical ionization.

RESULTS

Distinct peaks were observed for the drugs on each MRM channel within 2 min. The regression equations showed good linearity within the range 0.04-4.0 μg/mL for the tear and plasma samples with detection limits at 0.02-0.04 μg/mL. Recoveries for target analytes (FT and 5-FU) for the tear and plasma samples were in the 94-128% and 94-104% ranges, respectively. The intra- and inter-day coefficients of variation for the two drugs were lower than 10.8%. The accuracies of quantitation were 97-115% for both samples.

CONCLUSIONS

We established a high-throughput, reproducible, and practical procedure for analyzing FT and 5-FU in human tear and plasma samples using HILIC/MS/MS analysis with an aminopropyl-bonded mixed-mode separation column. This method can be applied to the high-throughput routines used in clinical analyses.

Food-effect study on uracil and dihydrouracil plasma levels as marker for dihydropyrimidine dehydrogenase activity in human volunteers

AIMS

This study aimed to determine the effect of food intake on uracil and dihydrouracil plasma levels. These levels are a promising marker for dihydropyrimidine dehydrogenase activity and for individualizing fluoropyrimidine anticancer therapy.

METHODS

A randomized, cross-over study in 16 healthy volunteers was performed, in which subjects were examined in fasted and fed state on two separate days. In fed condition, a high-fat, high-caloric breakfast was consumed between 8:00 h and 8:30 h. Whole blood for determination of uracil, dihydrouracil and uridine plasma levels was drawn on both test days at predefined time points between 8:00 h and 13:00 h.

RESULTS

Uracil levels were statistically significantly different between fasting and fed state. At 13:00 h, the mean uracil level in fasting state was 12.6 ± 3.7 ng ml-1 and after a test meal 9.4 ± 2.6 ng ml-1 (P < 0.001). Dihydrouracil levels were influenced by food intake as well (mean dihydrouracil level at 13:00 h in fasting state 147.0 ± 36.4 ng ml-1 and in fed state 85.7 ± 22.1 ng ml-1 , P < 0.001). Uridine plasma levels showed curves with similar patterns as for uracil.

CONCLUSIONS

It was shown that both uracil and dihydrouracil levels were higher in fasting state than in fed state. This is hypothesized to be an direct effect of uridine plasma levels, which were previously shown to be elevated in fasting state and reduced after intake of food. These findings show that, when assessing plasma uracil and dihydrouracil levels for adaptive fluoropyrimidine dosing in clinical practice, sampling should be done between 8:00 h and 9:00 h after overnight fasting to avoid bias caused by circadian rhythm and food effects.

Gold nanoparticles and reduced graphene oxide-amplified label-free DNA biosensor for dasatinib detection

Dasatinib or sprycel is an anticancer drug for treatment of chronic myelogenous leukemia, prostate cancer, and some of the other cancers with several adverse effects.

The Herb-Drug Pharmacokinetic Interaction of 5-Fluorouracil and Its Metabolite 5-Fluoro-5,6-Dihydrouracil with a Traditional Chinese Medicine in Rats

Background: Xiang-Sha-Liu-Jun-Zi-Tang (XSLJZT) is the most common traditional formula given to colorectal and breast cancer patients in Taiwan, according to a statistical study of the National Health Insurance Research Database. 5-Fluorouracil (5-FU) is widely used as the first line of treatment for colorectal cancer. Thus, the aim of study is to investigate the pharmacokinetic interaction of XSLJZT and 5-FU. Methods: To investigate the herb–drug interaction of XSLJZT with 5-FU as well as its metabolite 5-fluoro-5,6-dihydrouracil (5-FDHU) using pharmacokinetics, a high-performance liquid chromatography (HPLC) system coupled with a photodiode array detector was developed to monitor 5-FU and 5-FDHU levels in rat blood. Rats were divided into three cohorts, one of which was administered 5-FU (100 mg/kg, iv—intravenous) alone, while the other two groups were pretreated with low and high doses of XSLJZT (600 mg/kg/day or 2400 mg/kg/day for 5 consecutive days) in combination with 5-FU. Results: The results demonstrated that 5-FU level was not significantly different between the group treated with only 5-FU and the group pretreated with a normal dose of XSLJZT (600 mg/kg/day). However, pharmacokinetic analysis revealed that pretreatment with a high dose of XSLJZT (2400 mg/kg/day) extended the residence time and increased the volume of distribution of 5-FU. No significant distinctions were found in 5-FDHU pharmacokinetic parameters at three doses of XSLJZT. Conclusions: Overall, the pharmacokinetic results confirm the safety of coadministering 5-FU with XSLJZT, and provide practical dosage information for clinical practice.

A new sample preparation and separation combination for the precise, accurate, and simultaneous determination of uracil and dihydrouracil in human plasma by reversed-phase HPLC

We have developed an efficient procedure and detection method using reversed-phase high-performance liquid chromatography for the simultaneous measurement of uracil and dihydrouracil in human plasma. The procedure, including chromatographic conditions and sample preparation, was optimized and validated. Optimization of the sample preparation included deproteinization, extraction, and cleanup. A new sample preparation method which resulted in an improved extraction yield of analytes and significantly reduced interference at low-wavelength UV detection was developed. The developed method was validated for specificity, linearity, limits of detection and quantitation, precision, and accuracy. All calibration curves showed excellent linear regression (R²  > 0.9990) within the testing range. The limit of detection for uracil and dihydrouracil was 2.5 and 5.0 ng/mL, respectively. The extraction yields were >94% for uracil and 91% for dihydrouracil. Intra- and interassay precision and accuracy for uracil and dihydrouracil were lower than 8% at all tested concentrations. The proposed method was successfully applied to measure plasma concentrations of uracil and dihydrouracil in colorectal cancer patients scheduled to receive fluoropyrimidine-based chemotherapy.

Pretreatment serum uracil concentration as a predictor of severe and fatal fluoropyrimidine-associated toxicity

Background:

We investigated the predictive value of dihydropyrimidine dehydrogenase (DPD) phenotype, measured as pretreatment serum uracil and dihydrouracil concentrations, for severe as well as fatal fluoropyrimidine-associated toxicity in 550 patients treated previously with fluoropyrimidines during a prospective multicenter study.

Methods:

Pretreatment serum concentrations of uracil and dihydrouracil were measured using a validated LC-MS/MS method. The primary endpoint of this analysis was global (any) severe fluoropyrimidine-associated toxicity, that is, grade ⩾3 toxicity according to the NCI CTC-AE v3.0, occurring during the first cycle of treatment. The predictive value of uracil and the uracil/dihydrouracil ratio for early severe fluoropyrimidine-associated toxicity were compared. Pharmacogenetic variants in DPYD (c.2846A>T, c.1679T>G, c.1129-5923C>G, and c.1601G>A) and TYMS (TYMS 5′-UTR VNTR and TYMS 3′-UTR 6-bp ins/del) were measured and tested for associations with severe fluoropyrimidine-associated toxicity to compare predictive value with DPD phenotype. The Benjamini-Hochberg false discovery rate method was used to control for type I errors at level q<0.050 (corresponding to P<0.010).

Results:

Uracil was superior to the dihydrouracil/uracil ratio as a predictor of severe toxicity. High pretreatment uracil concentrations (>16 ng ml⁻¹) were strongly associated with global severe toxicity (OR 5.3, P=0.009), severe gastrointestinal toxicity (OR 33.7, P<0.0001), toxicity-related hospitalisation (OR 16.9, P<0.0001), as well as fatal treatment-related toxicity (OR 44.8, P=0.001). None of the DPYD variants alone, or TYMS variants alone, were associated with severe toxicity.

Conclusions:

High pretreatment uracil concentration was strongly predictive of severe, including fatal, fluoropyrimidine-associated toxicity, and is a highly promising phenotypic marker to identify patients at risk of severe fluoropyrimidine-associated toxicity.

Pharmacogenetics of anti-cancer drugs: State of the art and implementation - recommendations of the French National Network of Pharmacogenetics

Individualized treatment is of special importance in oncology because the drugs used for chemotherapy have a very narrow therapeutic index. Pharmacogenetics may contribute substantially to clinical routine for optimizing cancer treatment to limit toxic effects while maintaining efficacy. This review presents the usefulness of pharmacogenetic tests for some key applications: dihydropyrimidine dehydrogenase (DPYD) genotyping for fluoropyrimidine (5-fluorouracil, capecitabine), UDP glucuronosylstransferase (UGT1A1) for irinotecan and thiopurine S-methyltransferase (TPMT) for thiopurine drugs. Depending on the level of evidence, the French National Network of Pharmacogenetics (RNPGx) has issued three levels of recommendations for these pharmacogenetic tests: essential, advisable, and potentially useful. Other applications, for which the level of evidence is still discussed, will be evoked in the final section of this review.

Characterization of Contrast Agent Microbubbles for Ultrasound Imaging and Therapy Research

The high efficiency with which gas microbubbles can scatter ultrasound compared with the surrounding blood pool or tissues has led to their widespread employment as contrast agents in ultrasound imaging. In recent years, their applications have been extended to include super-resolution imaging and the stimulation of localized bio-effects for therapy. The growing exploitation of contrast agents in ultrasound and in particular these recent developments have amplified the need to characterize and fully understand microbubble behavior. The aim in doing so is to more fully exploit their utility for both diagnostic imaging and potential future therapeutic applications. This paper presents the key characteristics of microbubbles that determine their efficacy in diagnostic and therapeutic applications and the corresponding techniques for their measurement. In each case, we have presented information regarding the methods available and their respective strengths and limitations, with the aim of presenting information relevant to the selection of appropriate characterization methods. First, we examine methods for determining the physical properties of microbubble suspensions and then techniques for acoustic characterization of both suspensions and single microbubbles. The next section covers characterization of microbubbles as therapeutic agents, including as drug carriers for which detailed understanding of their surface characteristics and drug loading capacity is required. Finally, we discuss the attempts that have been made to allow comparison across the methods employed by various groups to characterize and describe their microbubble suspensions and promote wider discussion and comparison of microbubble behavior.

Degradation Rate of 5-Fluorouracil in Metastatic Colorectal Cancer: A New Predictive Outcome Biomarker?

Background

5-FU based chemotherapy is the most common first line regimen used for metastatic colorectal cancer (mCRC). Identification of predictive markers of response to chemotherapy is a challenging approach for drug selection. The present study analyzes the predictive role of 5-FU degradation rate (5-FUDR) and genetic polymorphisms (MTHFR, TSER, DPYD) on survival.

Materials and Methods

Genetic polymorphisms of MTHFR, TSER and DPYD, and the 5-FUDR of homogenous patients with mCRC were retrospectively studied. Genetic markers and the 5-FUDR were correlated with clinical outcome.

Results

133 patients affected by mCRC, treated with fluoropyrimidine-based chemotherapy from 2009 to 2014, were evaluated. Patients were classified into three metabolic classes, according to normal distribution of 5-FUDR in more than 1000 patients, as previously published: poor-metabolizer (PM) with 5-FU-DR ≤ 0,85 ng/ml/10⁶ cells/min (8 pts); normal metabolizer with 0,85 < 5-FU-DR < 2,2 ng/ml/10⁶ cells/min (119 pts); ultra-rapid metabolizer (UM) with 5-FU-DR ≥ 2,2 ng/ml/10⁶ cells/min (6 pts). PM and UM groups showed a longer PFS respect to normal metabolizer group (14.5 and 11 months respectively vs 8 months; p = 0.029). A higher G3-4 toxicity rate was observed in PM and UM, respect to normal metabolizer (50% in both PM and UM vs 18%; p = 0.019). No significant associations between genes polymorphisms and outcomes or toxicities were observed.

Conclusion

5-FUDR seems to be significantly involved in predicting survival of patients who underwent 5-FU based CHT for mCRC. Although our findings require confirmation in large prospective studies, they reinforce the concept that individual genetic variation may allow personalized selection of chemotherapy to optimize clinical outcomes.

Improving safety of fluoropyrimidine chemotherapy by individualizing treatment based on dihydropyrimidine dehydrogenase activity - Ready for clinical practice?

Fluoropyrimidines remain the cornerstone of treatment for different types of cancer, and are used by an estimated two million patients annually. The toxicity associated with fluoropyrimidine therapy is substantial, however, and affects around 30% of the patients, with 0.5-1% suffering fatal toxicity. Activity of the main 5-fluorouracil (5-FU) metabolic enzyme, dihydropyrimidine dehydrogenase (DPD), is the key determinant of 5-FU pharmacology, and accounts for around 80% of 5-FU catabolism. There is a consistent relationship between DPD activity and 5-FU exposure on the one hand, and risk of severe and potentially lethal fluoropyrimidine-associated toxicity on the other hand. Therefore, there is a sound rationale for individualizing treatment with fluoropyrimidines based on DPD status in order to improve patient safety. The field of individualized treatment with fluoropyrimidines is now rapidly developing. The main strategies that are available, are based on genotyping of the gene encoding DPD (DPYD) and measuring of pretreatment DPD phenotype. Clinical validity of additional approaches, including genotyping of MIR27A has also recently been demonstrated. Here, we critically review the evidence on clinical validity and utility of strategies available to clinicians to identify patients at risk of developing severe and potentially fatal toxicity as a result of DPD deficiency. We evaluate the advantages and limitations of these methods when used in clinical practice, and discuss for which strategies clinical implementation is currently justified based on the available evidence and, in addition, which additional data will be required before implementing other, as yet less developed strategies.

Colon Cancer Cells Gene Expression Signature As Response to 5- Fluorouracil, Oxaliplatin, and Folinic Acid Treatment

5-FU cytotoxicity mechanism has been assigned both to the miss-incorporation of fluoronucleotides into RNA and DNA and to the inhibition of thymidylate synthase. 5-FU is one of the most widely used chemotherapeutic drugs, although it has severe side effects that may vary between patients. Pharmacogenetic studies related to 5-FU have been traditionally focused on the rate-limiting catabolic enzyme, dihydropyrimidine dehydrogenase that breaks 80–85% of 5-FU into its inactive metabolite. Choosing the right dosing scheme and chemotherapy strategy for each individual patient remains challenging for personalized chemotherapy management. In the general effort toward reduction of colorectal cancer mortality, in vitro screening studies play a very important role. To accelerate translation research, increasing interest has been focused on using in vivo-like models such as three-dimensional spheroids. The development of higher throughput assays to quantify phenotypic changes in spheroids is an active research area. Consequently, in this study we used the microarray technology to reveal the HT-29 colorectal adenocarcinoma cells gene expression signature as response to 5-FU/OXP/FA treatment in a state of the art 3D culture system. We report here an increased reactive oxygen species production under treatment, correlated with a decrease in cell viability and proliferation potential. With respect to the HT-29 cells gene expression under the treatment with 5-FU/OXP/FA, we found 15.247 genes that were significantly differentially expressed (p < 0.05) with a fold change higher that two-fold. Among these, 7136 genes were upregulated and 8111 genes were downregulated under experimental conditions as compared to untreated cells. The most relevant and statistic significant (p < 0.01) pathways in the experiment are associated with the genes that displayed significant differential expression and are related to intracellular signaling, oxidative stress, apoptosis, and cancer.

Fluorouracil plasma monitoring: systematic review and economic evaluation of the My5-FU assay for guiding dose adjustment in patients receiving fluorouracil chemotherapy by continuous infusion

BACKGROUND

5-Fluorouracil (5-FU) is a chemotherapy used in colorectal, head and neck (H&N) and other cancers. Dose adjustment is based on body surface area (BSA) but wide variations occur. Pharmacokinetic (PK) dosing is suggested to bring plasma levels into the therapeutic range to promote fewer side effects and better patient outcomes. We investigated the clinical effectiveness and cost-effectiveness of the My5-FU assay for PK dose adjustment to 5-FU therapy.

OBJECTIVES

To systematically review the evidence on the accuracy of the My5-FU assay compared with gold standard methods [high-performance liquid chromatography (HPLC) and liquid chromatography-mass spectrometry (LC-MS)]; the effectiveness of My5-FU PK dosing compared with BSA; the effectiveness of HPLC and/or LC-MS compared with BSA; the generalisability of published My5-FU and PK studies; costs of using My5-FU; to develop a cost-effectiveness model.

DATA SOURCES

We searched MEDLINE, EMBASE, Science Citation Index and other databases between January and April 2014.

METHODS

Two reviewers independently screened titles and abstracts with arbitration and consensus agreement. We undertook quality assessment. We reconstructed Kaplan-Meier plots for progression-free survival (PFS) and overall survival (OS) for comparison of BSA and PK dosing. We developed a Markov model to compare My5-FU with BSA dosing which modelled PFS, OS and adverse events, using a 2-week cycle over a 20 year time horizon with a 3.5% discount rate. Health impacts were evaluated from the patient perspective, while costs were evaluated from the NHS and Personal Social Services perspective.

RESULTS

A total of 8341 records were identified through electronic searches and 35 and 54 studies were included in the clinical effectiveness and cost-effectiveness reviews respectively. There was a high apparent correlation between My5-FU, HPLC and LC-MS/mass spectrometer but upper and lower limits of agreement were -18% to 30%. Median OS were estimated as 19.6 [95% confidence interval (CI) 17.0 to 21.0] months for PK versus 14.6 (95% CI 14.1 to 15.3) months for BSA for 5-FU+folinic acid (FA); and 27.4 (95% CI 23.2 to 38.8) months for PK versus 20.6 (95% CI 18.4 to 22.9) months for BSA for FOLFOX6 in metastatic colorectal cancer (mCRC). PK versus BSA studies were generalisable to the relevant populations. We developed cost-effectiveness models for mCRC and H&N cancer. The base case assumed a cost per My5-FU assay of £ 61.03. For mCRC for 12 cycles of a oxaliplatin in combination with 5-fluorouracil and FA (FOLFOX) regimen, there was a quality-adjusted life-year (QALY) gain of 0.599 with an incremental cost-effectiveness ratio of £ 4148 per QALY. Probabilistic and scenario analyses gave similar results. The cost-effectiveness acceptability curve showed My5-FU to be 100% cost-effective at a threshold of £ 20,000 per QALY. For H&N cancer, again, given caveats about the poor evidence base, we also estimated that My5-FU is likely to be cost-effective at a threshold of £ 20,000 per QALY.

LIMITATIONS

Quality and quantity of evidence were very weak for PK versus BSA dosing for all cancers with no randomised controlled trials (RCTs) using current regimens. For H&N cancer, two studies of regimens no longer in use were identified.

CONCLUSIONS

Using a linked evidence approach, My5-FU appears to be cost-effective at a willingness to pay of £ 20,000 per QALY for both mCRC and H&N cancer. Considerable uncertainties remain about evidence quality and practical implementation. RCTs are needed of PK versus BSA dosing in relevant cancers.

Attenuation effect of Abnormal Savda Munziq on liver and heart toxicity caused by chemotherapy in mice

Abnormal Savda Munziq (ASMq), an Uighur medicine formula commonly used in the treatment of cancer, has been speculated to possess antioxidative and antiproliferative effects, and to regulate immune activity. The present study was designed to systematically elucidate the toxicity-reducing activity of ASMq in mice undergoing combination chemotherapy with doxorubicin and 5-fluorouracil (5-FU). The mice were divided into normal (saline, 10 ml/kg) and doxorubicin + 5-FU groups (doxorubicin, 2.5 mg/kg; 5-FU, 10 mg/kg on alternate days). In addition, three groups received different doses of ASMq (2, 4 and 8 g/kg), in addition to doxorubicin (2.5 mg/kg) and 5-FU (10 mg/kg) treatment on alternate days. The histology of the heart and liver, superoxide dismutase (SOD), glutathione peroxidase (GSH-Px) activity, malondialdehyde (MDA) concentrations in heart homogenate, and various biochemical parameters of the liver were evaluated. Compared with the normal control group, ASMq dose-dependently improved a number of variables, including body weight, liver index, transaminase and total protein, and partially normalized liver and cardiac pathology. ASMq restored activities of defense antioxidant enzymes SOD and GSH-Px towards normal levels, and decreased MDA concentration in dose-dependent manner. These results demonstrated that ASMq provides significant protection against doxorubicin + 5-FU combination induced hepatotoxicity and cardiotoxicity. Further studies are required to determine the effects of ASMq against doxorubicin + 5-FU-induced toxicity during chemotherapy in vivo.

Development and validation of a rapid and sensitive UPLC-MS/MS method for determination of uracil and dihydrouracil in human plasma

Quantification of the endogenous dihydropyrimidine dehydrogenase (DPD) substrate uracil (U) and the reaction product dihydrouracil (UH2) in plasma might be suitable for identification of patients at risk of fluoropyrimidine-induced toxicity as a result of DPD deficiency. In this paper, we describe the development and validation of a rapid and sensitive ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) assay for quantification of U and UH2 in human plasma. Analytes were extracted by protein precipitation, chromatographically separated on an Acquity UPLC(®) HSS T3 column with gradient elution and analyzed with a tandem mass spectrometer equipped with an electrospray ionization source. U was quantified in the negative ion mode and UH2 in the positive ion mode. Stable isotopes for U and UH2 were used as internal standards. Total chromatographic run time was 5min. Validated concentration ranges for U and UH2 were from 1 to 100ng/mL and 10 to 1000ng/mL, respectively. Inter-assay bias and inter-assay precision for U were within ±2.8% and ≤12.4%. For UH2, inter-assay bias and inter-assay precision were within ±2.9% and ≤7.2%. Adequate stability of U and UH2 in dry extract, final extract, stock solution and plasma was demonstrated. Stability of U and UH2 in whole blood was only satisfactory when stored up to 4hours at 2-8°C, but not at ambient temperatures. An accurate, precise and sensitive UPLC-MS/MS assay for quantification of U and UH2 in plasma was developed. This assay is now applied to support clinical studies with fluoropyrimidine drugs.

A Critical Review on Clinical Application of Separation Techniques for Selective Recognition of Uracil and 5-Fluorouracil

The most important objectives that are frequently found in bio-analytical chemistry involve applying tools to relevant medical/biological problems and refining these applications. Developing a reliable sample preparation step, for the medical and biological fields is another primary objective in analytical chemistry, in order to extract and isolate the analytes of interest from complex biological matrices. Since, main inborn errors of metabolism (IEM) diagnosable through uracil analysis and the therapeutic monitoring of toxic 5-fluoruracil (an important anti-cancerous drug) in dihydropyrimidine dehydrogenase deficient patients, require an ultra-sensitive, reproducible, selective, and accurate analytical techniques for their measurements. Therefore, keeping in view, the diagnostic value of uracil and 5-fluoruracil measurements, this article refines several analytical techniques involved in selective recognition and quantification of uracil and 5-fluoruracil from biological and pharmaceutical samples. The prospective study revealed that implementation of molecularly imprinted polymer as a solid-phase material for sample preparation and preconcentration of uracil and 5-fluoruracil had proven to be effective as it could obviates problems related to tedious separation techniques, owing to protein binding and drastic interferences, from the complex matrices in real samples such as blood plasma, serum samples.

Targeted and controlled drug delivery using a temperature and ultra-violet responsive liposome with excellent breast cancer suppressing ability

Drug delivery systems (DDS) with favorable serum stability, high intra-tumor accumulation and tumor specific drug release are highly desired for promoting chemotherapeutic efficacy.

Evaluation of a closed-system cytotoxic transfer device in a pharmaceutical isolator

PURPOSE

The occupational risk associated with handling of cytotoxic anticancer drugs is well documented and, in many countries, pharmaceutical isolators are used to contain cytotoxic residues during preparation of cytotoxic infusions. Isolators are difficult to clean leading to concerns that cytotoxic contamination from the work area could be transferred to surfaces of products leaving the isolator. This study investigated the surface contamination arising from the preparation of five anticancer drug infusions (Epirubicin, Fluorouracil, Cisplatin, Oxaliplatin and Carboplatin) in a pharmaceutical isolator and compared use of a conventional syringe and needle technique with a closed-system drug transfer device (CSDTD).

METHODS

Wipe samples were taken over 1 week from pre-defined areas in the isolator, gloves, preparation mats, and also from the surfaces of prepared cytotoxic infusion bags and pre-filled syringes to obtain baseline surface contamination data. Following operator familiarisation, the CSDTD was then introduced and sampling repeated for a further week (intervention period). The samples obtained were analysed using validated HPLC-UV, HPLC-FL and ICP-MS techniques, as appropriate.

RESULTS

All surfaces sampled during baseline, including external surfaces of infusions and syringes, were contaminated with each marker drug. During the intervention phase, isolator surfaces were free from detectable contamination and the contamination measured on gloves, preparation mats and surface of infusions was markedly reduced. The frequency of contamination on syringe and infusion surfaces was also lower.

CONCLUSION

Surface contamination from cytotoxic infusion preparation in a pharmaceutical isolator was significant and could transmit cytotoxic residues to patient and public areas via infusion surfaces. The frequency and amount of contamination were reduced by the CSDTD.

Indirect assessment of dihydropyrimidine dehydrogenase activity in cats

Use of 5-fluoropyridimine antimetabolite drugs, specifically 5-fluorouracil (5-FU), has been discouraged in cats because of adverse events including neurotoxicity and death. Causes of toxicity have never been elucidated. In humans, toxicity has been associated with ineffective metabolism secondary to deficiencies in dihydropyrimidine dehydrogenase (DPD). Direct assessment of DPD activity is challenging; determination of uracil:dihydrouracil (U:UH2 ) in plasma using high performance liquid chromatography (HPLC) has been reported as an indirect measurement. U:UH2 was measured in the plasma of 73 cats. Mean U:UH2 for all cats was 1.66 ± 0.11 (median 1.53, range 0.24-7.00). Seventeen (23%) cats had U:UH2 >2, a value associated with decreased DPD activity in humans. Spayed female cats had significantly lower U:UH2 as compared with intact females, and age and U:UH2 were weakly but significantly negatively correlated (r = -0.26). Studies correlating U:UH2 and 5-FU tolerability are required to further determine the validity and use of this test in cats.

Evaluation of predictive tests for screening for dihydropyrimidine dehydrogenase deficiency

5-Fluorouracil (5-FU) is rapidly degraded by dihyropyrimidine dehydrogenase (DPD). Therefore, DPD deficiency can lead to severe toxicity or even death following treatment with 5-FU or capecitabine. Different tests based on assessing DPD enzyme activity, genetic variants in DPYD and mRNA variants have been studied for screening for DPD deficiency, but none of these are implemented broadly into clinical practice. We give an overview of the tests that can be used to detect DPD deficiency and discuss the advantages and disadvantages of these tests.

Pharmacokinetic application of a bio-analytical LC-MS method developed for 5-fluorouracil and methotrexate in mouse plasma, brain and urine

In the past we have reported significant cognitive deficits in mice receiving 5-fluorouracil in combination with low-dose methotrexate. To explain such interactions, a pharmacokinetic study was designed. A sensitive bio-analytical method was therefore developed and validated for 5-fluorouracil and methotrexate in mouse plasma, brain and urine with liquid chromatography coupled to a single quadrupole mass spectrometer. Chromatographic separation was accomplished by Agilent® Zorbax® SB-C18 column, with isocratic elution (5 mM ammonium acetate and methanol, 70:30, %v/v) at a flow rate of 300 μL/min. The limit of quantitation for both drugs was 15.6 ng/mL (plasma and brain) and 78.1 ng/mL (urine), with interday and intraday precision and accuracy ≤15% and a total run time of 6 min. This bio-analytical method was used for the pharmacokinetic characterization of 5-fluorouracil and methotrexate in mouse plasma, brain and urine over a period of 24 h. This method allowed characterization of the brain concentrations of 5-fluorouracil over a period of 24 h.

LC-MS/MS method for simultaneous analysis of uracil, 5,6-dihydrouracil, 5-fluorouracil and 5-fluoro-5,6-dihydrouracil in human plasma for therapeutic drug monitoring and toxicity prediction in cancer patients

The chemotherapeutic drug 5-fluorouracil (5-FU) is widely used for treating solid tumors. Response to 5-FU treatment is variable with 10-30% of patients experiencing serious toxicity partly explained by reduced activity of dihydropyrimidine dehydrogenase (DPD). DPD converts endogenous uracil (U) into 5,6-dihydrouracil (UH(2) ), and analogously, 5-FU into 5-fluoro-5,6-dihydrouracil (5-FUH(2) ). Combined quantification of U and UH(2) with 5-FU and 5-FUH(2) may provide a pre-therapeutic assessment of DPD activity and further guide drug dosing during therapy. Here, we report the development of a liquid chromatography-tandem mass spectrometry assay for simultaneous quantification of U, UH(2) , 5-FU and 5-FUH(2) in human plasma. Samples were prepared by liquid-liquid extraction with 10:1 ethyl acetate-2-propanol (v/v). The evaporated samples were reconstituted in 0.1% formic acid and 10 μL aliquots were injected into the HPLC system. Analyte separation was achieved on an Atlantis dC(18) column with a mobile phase consisting of 1.0 mm ammonium acetate, 0.5 mm formic acid and 3.3% methanol. Positively ionized analytes were detected by multiple reaction monitoring. The analytical response was linear in the range 0.01-10 μm for U, 0.1-10 μm for UH(2) , 0.1-75 μm for 5-FU and 0.75-75 μm for 5-FUH(2) , covering the expected concentration ranges in plasma. The method was validated following the FDA guidelines and applied to clinical samples obtained from ten 5-FU-treated colorectal cancer patients. The present method merges the analysis of 5-FU pharmacokinetics and DPD activity into a single assay representing a valuable tool to improve the efficacy and safety of 5-FU-based chemotherapy.

Assessment of plasma uracil-to-dihydrouracil concentration ratio as an indicator of dihydropyrimidine dehydrogenase activity in clinically normal dogs and dogs with neoplasia or renal insufficiency

OBJECTIVE

To determine and compare the ratio of uracil (U) to dihydrouracil (UH(2)) concentrations in plasma as an indicator of dihydropyrimidine dehydrogenase activity in clinically normal dogs and dogs with neoplasia or renal insufficiency.

ANIMALS

101 client- and shelter-owned dogs.

PROCEDURES

Study dogs included 74 clinically normal dogs, 17 dogs with neoplasia, and 10 dogs with renal insufficiency. For each dog, a blood sample was collected into an EDTA-containing tube; plasma U and UH(2) concentrations were determined via UV high-performance liquid chromatography, and the U:UH(2) concentration ratio was calculated. Data were compared among dogs grouped on the basis of sex, clinical group assignment, reproductive status (sexually intact, spayed, or castrated), and age.

RESULTS

Mean ± SEM U:UH(2) concentration ratio for all dogs was 1.55 ± 0.08 (median, 1.38; range, 0.4 to 7.14). In 14 (13.9%) dogs, the U:UH(2) concentration ratio was considered abnormal (ie, > 2). Overall, mean ratio for sexually intact dogs was significantly higher than that for neutered dogs; a similar difference was apparent among males but not females. Dogs with ratios > 2 and dogs with ratios ≤ 2 did not differ significantly with regard to sex, clinical group, reproductive status, or age.

CONCLUSIONS AND CLINICAL RELEVANCE

Determination of the U:UH(2) concentration ratio was easy to perform. Ratios were variable among dogs, possibly suggesting differences in dihydropyrimidine dehydrogenase activity. However, studies correlating U:UH(2) concentration ratio and fluoropyrimidine antimetabolite drug tolerability are required to further evaluate the test's validity and its appropriate use in dogs.

Pretherapeutic uracil and dihydrouracil levels of colorectal cancer patients are associated with sex and toxic side effects during adjuvant 5-fluorouracil-based chemotherapy

BACKGROUND

In Nordic countries, the standard treatment of colorectal cancer (CRC) in the adjuvant setting is bolus 5-fluorouracil (5-FU) plus leucovorin alone or in combination with oxaliplatin. 5-FU competes with the natural occurring pyrimidine uracil (Ura) as a substrate for dihydropyrimidine dehydrogenase (DPD; enzyme commission number 1.3.1.2). Low DPD activity is associated with toxicity during treatment. Pretherapeutic detection of DPD deficiency could prevent severe toxicity otherwise limiting drug administration. Assays showing that DPD deficiency impairs breakdown of Ura to dihydrouracil (UH(2)) seem promising for clinical use.

METHODS

Urine was collected from 56 untreated volunteers and 143 patients with CRC before adjuvant treatment. Ura and UH(2) were analyzed using a column-switching high-performance liquid chromatography method that incorporates reversed-phase and cation-exchange columns. Ura, UH(2), and UH(2)/Ura levels were related to toxicity.

RESULTS

Ura and UH(2) in patients were not different from controls. UH(2) was significantly higher in women compared with men. The UH(2)/Ura ratio, however, did not differ according to sex. Low UH(2) and UH(2)/Ura levels were associated with diarrhea in men. Women experiencing thrombocytopenia had significantly higher Ura compared with women with no thrombocytopenia. The UH(2)/Ura ratio correlated negatively with total toxicity score in men (r = -0.39, P = .020).

CONCLUSION

Pretherapeutic Ura and UH(2) levels per se may be related to risk of side effects during adjuvant 5-FU-based treatment, whereas the UH(2)/Ura ratio may not always reveal such a risk. Sex is a strong risk factor for toxicity, showing the importance of evaluating male and female patients separately.

Severe fluoropyrimidine-related toxicity: clinical implications of DPYD analysis and UH2/U ratio evaluation

The fluoropyrimidines are commonly used in chemotherapeutic cancer medicine, but many patients still experience severe adverse side effects from these drugs. We observed a severe toxicity in a 50-year-old woman treated with capecitabine and docetaxel for a metastatic breast cancer. Since dihydropyrimidine dehydrogenase (DPD) is the main candidate for pharmacogenetic studies on 5-FU toxicity, the entire coding sequence and exon-flanking intronic regions of the DPYD gene were sequenced in the patient. None of the previously described deleterious variants were detected. Also, the haplotype-based analysis failed to reveal DPYD variations associated with 5-FU toxicity. We also evaluated the UH2/U ratio in plasma as an index of 5-FU pharmacokinetics. The UH2/U value did not demonstrate low DPD activity in the patient. We discuss the advantages and limitations of this approach, particularly concerning the clinical applications of 5-FU pharmacogenetics in the family setting.

Pharmacokinetics of orally administered uracil in healthy volunteers and in DPD-deficient patients, a possible tool for screening of DPD deficiency

Purpose

Dihydropyrimidine dehydrogenase (DPD) deficiency can lead to severe toxicity in patients treated with standard doses of 5-fluorouracil (5-FU). Oral uracil administration and subsequent measurement of uracil and dihydrouracil (DHU) plasma concentrations might detect patients with DPD deficiency. This study compares the pharmacokinetics of uracil and DHU after oral uracil administration in subjects with normal and deficient DPD status.

Methods

Five hundred milligrams of uracil per metre square was administered orally to 11 subjects with normal DPD status and to 10 subjects with reduced DPD activity. Repeated administration (n = 3) of this dose was performed in 4 subjects, and 1,000 mg uracil/m² was administered to 4 subjects to assess intra-individual variation and linearity of pharmacokinetics.

Results

In subjects with normal DPD status, 500 mg/m² uracil resulted in uracil C_max levels of 14.4 ± 4.7 mg/L at T_max = 30.0 ± 11.6 min, and in DPD-deficient subjects, 20.0 ± 4.5 mg/L at 31.5 ± 1.1 min. The uracil AUC_0>180 was 31.2 ± 5.1 mg L/h in DPD-deficient subjects, which was significantly higher (P < 0.05) than in the subjects with normal DPD status (13.8 ± 3.9 mg L/h). Repeated uracil dosing showed reproducible uracil PK in subjects with normal DPD status, and dose elevation of uracil suggested linear pharmacokinetics.

Conclusion

The pharmacokinetics of uracil differs significantly between subjects with a normal DPD activity and those with a deficient DPD status. The AUC and C_max of uracil can be useful as a diagnostic tool to differentiate patients with regard to DPD status.

Pharmacokinetically guided dose adjustment of 5-fluorouracil: a rational approach to improving therapeutic outcomes

Chemotherapy dosing of the fluoropyrimidine 5-fluorouracil (5-FU) is currently based on body surface area. However, body surface area-based dosing has been associated with clinically significant pharmacokinetic variability, and as such, dosing based on body surface area may be of limited use. The clinical activity of 5-FU is modest at standard doses, and in general, dosing is limited by the safety profile, with myelosuppression and gastrointestinal toxicity being the most commonly observed side effects. Various strategies have been developed to enhance the clinical activity of 5-FU, such as biochemical modulation, alterations in scheduling of administration, and the use of oral chemotherapy. Studies that have shown an association between plasma concentration with toxicity and clinical efficacy have shown that pharmacokinetically guided dose adjustments can substantially improve the therapeutic index of 5-FU treatment. These studies have shown that only 20%-30% of patients treated with a 5-FU-based regimen have 5-FU levels that are in the appropriate therapeutic range--approximately 40%-60% of patients are underdosed and 10%-20% of patients are overdosed. To date, 5-FU drug testing has not been widely used because of the lack of a simple, fast, and inexpensive method. Recent advances in testing based on liquid chromatography-mass spectroscopy and a nanoparticle antibody-based immunoassay for 5-FU may now allow for routine monitoring of 5-FU in clinical practice. We review the data on pharmacokinetically guided dose adjustment of 5-FU and discuss the potential of this approach to advance therapeutic outcomes.

5-fluorouracil pharmacokinetics predicts disease-free survival in patients administered adjuvant chemotherapy for colorectal cancer

PURPOSE

To evaluate 5-fluorouracil (5-FU) and 5-fluoro-5,6-dihydrouracil (5-FDHU) pharmacokinetics and disease-free survival (DFS) in colorectal cancer patients given 5-FU-based adjuvant chemotherapy within a nonrandomized, retrospective, pharmacokinetic study.

EXPERIMENTAL DESIGN

One hundred fifteen patients including 72 men (median age, 63 years; range, 36-79 years) and 43 women (median age, 60 years; range, 36-73 years) received 6 cycles of l-leucovorin 100 mg/m(2)/day and 5-FU 370 mg/m(2)/day i.v. boluses (5 days every 4 weeks). Individual plasma concentrations of 5-FU and 5-FDHU were determined on day 1 of the first cycle with a validated high performance liquid chromatography method, and the main pharmacokinetic variables were determined. Follow-up of all patients was extended up to 5 years after the end of adjuvant chemotherapy, and DFS was recorded. Univariate and multivariate analyses were conducted to evaluate any correlation among 5-FU pharmacokinetics, clinical and pathologic variables, and DFS.

RESULTS

The area under the time/concentration curve (AUC) of 5-FU was significantly lower in 58 subjects who recurred (7.5 +/- 2.9 h x mg/L) with respect to other patients (9.3 +/- 4.1 h x mg/L). Furthermore, AUC values lower than 8.4 h x mg/L together with lymph node involvement and the interruption of treatment or reduction of doses were identified as risk factors at univariate analysis. The completion of 6 cycles of adjuvant treatment without dosage modifications was the only independent risk factor at multivariate analysis, despite a trend toward significance for 5-FU AUC values (cutoff value, 8.4 hxmg/L) was observed (P = 0.06).

CONCLUSIONS

Pharmacokinetics of 5-FU should be regarded as an important factor for predicting disease recurrence in colorectal cancers.

HPLC with UV or mass spectrometric detection for quantifying endogenous uracil and dihydrouracil in human plasma

BACKGROUND

We developed and compared 2 different methods for quantifying uracil (U) and dihydrouracil (UH(2)) in BSA and human plasma. Special attention was paid to the selectivity/specificity and the absence of a matrix effect. The UH(2)/U ratio is intended as a biomarker to identify patients with deficiency in 5-fluorouracil metabolism.

METHODS

We quantified U and UH(2) with 2 liquid chromatography methods after solid-phase extraction, one with UV detection (LC-UV) and the other with mass spectrometric detection (LC-MS). We selected 2 internal standards to prevent the risk of interferences. Separation was achieved with a Waters Atlantis dC18 column (LC-MS) or a Waters SymmetryShield RP18 column connected with an Atlantis dC18 (LC-UV). Mass spectrometric data were acquired in single-ion monitoring mode.

RESULTS

Assay imprecision in BSA solution was <15% (LC-UV) and <12% (LC-MS); in plasma, assay imprecision was <9.5% and <9.0%, respectively. Recoveries were 88.2%-110% (LC-UV) and 94.8%-107% (LC-MS). Extraction efficiencies were >or=89.0%. In BSA, the lower limits of quantification for U and UH(2) were 2.5 microg/L and 6.25 microg/L, respectively, for the LC-UV method and 2.5 microg/L and 3.1 microg/L for LC-MS. The corresponding values in plasma were 11.6 microg/L and 21.5 microg/L, and 4.1 microg/L and 12.1 microg/L.

CONCLUSIONS

To estimate endogenous U and UH(2) concentrations and their ratio, we recommend the use of a drug-free human plasma pool in which baseline U and UH(2) concentrations have previously been measured with the standard-addition method. Our LC-MS method, which has the better test performance and is useful for measuring UH(2)/U ratios in cancer patients, is preferred when this equipment is available.