Dihydromyricetin reverses capecitabine-induced peripheral myelin dysfunction through modulation of oxidative stress.

Previous clinical reports have shown that capecitabine, an oral prodrug of 5-fluorouracil (5-Fu), can induce peripheral neuropathy, resulting in numbness, paresthesia and hypoesthesia. However, the mechanism through which capecitabine causes peripheral nerve injury remains unclear. Here, we demonstrate that systemic administration of capecitabine leads to myelin abnormalities in the peripheral nerves of mice, which are possibly attributed to the death of Schwann cells, the myelinating cells in the peripheral nervous system. Furthermore, our results show that 5-Fu induces significant oxidative stress in Schwann cells by inhibiting the expression of the anti-oxidative protein DJ-1, leading to a decrease in Schwann cell markers. We found that the anti-oxidant dihydromyricetin (DMY) reverses 5-Fu-induced Schwann cell death and oxidative stress and alleviates capecitabine-induced myelin abnormalities. Taken together, our data indicate that capecitabine induces peripheral myelin dysfunction by regulating DJ-1-mediated oxidative stress in Schwann cells and reveal DMY as a potential therapeutic strategy for capecitabine-induced peripheral neuropathy.

The effect of melatonin on capecitabine-induced hepatic and renal toxicity in rats.

BACKGROUND: Capecitabine (CAPE), an antimetabolite chemotherapy, can induce hepatic and renal toxicity. Melatonin (MEL), a neurohormone, possesses antioxidant, anti-apoptotic and anti-inflammatory effects. This study investigated the impact of MEL on capecitabine-induced hepatic and renal toxicity. METHODS AND MATERIALS: Twenty-five male Wistar rats were categorized into five groups for the study. The groups included a control group, MEL10 group (rats receiving daily intraperitoneal injections of 5 mg/kg MEL), CAPE 500 group (rats receiving weekly intraperitoneal injections of 500 mg/kg CAPE), CAPE + MEL five group, and CAPE + MEL 10 group. All groups were treated for a duration of 6 weeks. Various hematological, serological, biochemical, and histopathological assessments were conducted to evaluate the objective of the study. RESULTS: The administration of CAPE led to significant liver and kidney toxicity, as evidenced by elevated levels of malondialdehyde (MDA), myeloperoxidase (MPO), nitric oxide (NO), as well as serological markers including AST, ALT, ALP, BUN, and creatinine. CAPE exposure also resulted in a reduction in total antioxidant capacity (TAC) and glutathione peroxidase (GPx) levels. Histological examination revealed hyperemia in both liver and kidney tissues exposed to CAPE. However, treatment with MEL demonstrated positive effects. MEL administration alleviated oxidative stress, reduced levels of liver enzymes, BUN, and creatinine, and ameliorated histopathological degenerations. MEL also increased GPx and TAC levels. Moreover, MEL treatment aided in restoring the body weight that was lost due to CAPE exposure. CONCLUSION: Our findings indicated that the administration of MEL in rats significantly enhanced the hepatic and renal toxicity induced by CAPE.

Assessing the risks of capecitabine and its active metabolite 5-fluorouracil to freshwater biota.

Capecitabine (CAP, prodrug) and 5-fluorouracil (5-FU, its active metabolite) are two of the most prominent cytostatics, for which no clear picture can be drawn regarding potential concentrations of effect for freshwater biota, with CAP being grouped in the least studied cytostatic, whereas 5-FU has been classified as of no and of high environmental risk. Accordingly, the present work aimed to assess the ecotoxicity of CAP and 5-FU in three freshwater species, which included a 72-h assay with the producer Raphidocelis subcapitata; a 96-h assay with the invertebrate secondary consumer Hydra viridissima; and a 96-h assay with embryos of the vertebrate secondary consumer Danio rerio. The following endpoints were monitored: yield and population growth rate for the algae; mortality, morphological alterations, and post-exposure feeding rates for the cnidarian; and mortality, hatching, and malformations for the fish. Overall, organisms' sensitivity to CAP decreased in the following order: R. subcapitata > H. viridissima > D. rerio, whereas for 5-FU, it decreased in the following order: H. viridissima > D. rerio > R. subcapitata. For CAP, no median lethal effective concentrations (LC/EC50) were possible to compute for D. rerio, with no significant mortality or malformations registered in embryos exposed at concentrations up to 800 mg L-1. For R. subcapitata, the EC50s were 0.077 and 0.63 mg L-1 for yield and growth rate, respectively, and for H. viridissima, the EC50,30 min for feeding was 22.0 mg L-1. For 5-FU, no EC50s could be computed for R. subcapitata, whilst the EC50s for H. viridissima mortality and feeding were 55.4 and 67.9 mg L-1, respectively, and for D. rerio, the LC50,96 h and EC50,96 h (hatching and abnormalities) were 4546, 4100, and 2459 mg L-1, respectively. Assuming similar modes of action for both compounds and their co-occurrence, the combined risk quotient of the two chemicals was determined to be 7.97, which represents a risk for freshwater biota. Anticipating the increased consumption of these compounds and cancer development trends worldwide, these impacts may be further aggravated.

Baicalein prevents capecitabine-induced heart damage in female Wistar rats and enhances its anticancer potential in MCF-7 breast cancer cells.

AIM: We investigated the ability of baicalein (BAI) to enhance the anticancer potential of capecitabine (CAP) in the MCF-7 cell line and its protective effect on CAP-induced cardiotoxicity in female Wistar rats. METHODS AND KEY FINDINGS: In vitro study involved evaluating the effect of BAI and/or CAP on cell viability, cell cycle progression, and BAX and Bcl2 gene expression in MCF-7 cells. Co-treatment of BAI with CAP significantly reduced the viability of MCF-7 cells, improved their cytotoxic effect, markedly elevated the percentage of the sub-G1 population, drastically reduced the G2/M population, and significantly altered the mRNA expression of BAX and Bcl2 genes compared with each treatment alone. In vivo study revealed that the oral administration of CAP (140 mg/kg BW) to adult female rats significantly elevated the levels of serum creatine kinase-myocardial band (CK-MB), lactate dehydrogenase (LDH), tumor necrosis factor (TNF)-α, and interleukin (IL)-1ß and cardiac TNF-α, IL-1ß malondialdehyde (MDA) concentration, whereas it reduced the serum and cardiac total antioxidant capacity (TAC), level of cardiac glutathione (GSH) and activity of glutathione peroxidase (GPx) with a vast array of circulatory, inflammatory, degenerative, and necrotic alterations in the cardiac tissue. Furthermore, CAP administration significantly upregulated the mRNA expression of NF-κB, TLR4, MyD88, ATF6, CHOP, and JNK genes. Concurrent administration of BAI (200 mg/kg BW) and CAP significantly improved the biochemical alterations and cardiac oxidant/antioxidant status and architecture. In addition, it modulated the TLR4/MyD88/NF-κB pathway and endoplasmic reticulum stress. SIGNIFICANCE: Altogether, BAI can augment the anticancer potential of CAP and alleviate its cardiotoxic effects during cancer treatment.

Evaluation of hepatic drug-metabolism for glioblastoma using liver-brain chip.

Glioma is one of the most aggressive and highly fatal diseases with an extremely poor prognosis. Considering the poor clinical response to therapy in glioma, it is urgent to establish an in vitro model to facilitate the screening and assessment of anti-brain-tumor drugs. The blood-brain barrier (BBB), as well as liver metabolism plays an important role in determining the pharmacological activity of many anti-brain-tumor drugs. In this work, we designed a multi-interface liver-brain chip integrating co-culture system to assess hepatic metabolism dependent cytotoxicity of anti-brain-tumor drug in vitro. This microdevice composed of three microchannels which were separated by porous membrane and collagen. HepG2 and U87 cells were cultured in separated channels as mimics of liver and glioblastoma. Brain microvascular endothelial cells (BMECS) and cerebral astrocytes were co-cultured on collagen to mimic the brain microvascular endothelial barrier. Three common anti-tumor drugs, paclitaxel (PTX), capecitabine (CAP) and temozolomide (TMZ), were evaluated on this chip. In integrated liver-brain chip, liver enhanced the cytotoxicity of CAP on U87 cells by 30%, but having no significant effect on TMZ. The BBB decreased the cytotoxicity of PTX by 20%, while no significant effects were observed on TMZ and CAP, indicating the importance of liver metabolism and blood-brain barrier on the evaluation of anti-brain-tumor drugs. This work provides a biomimetic liver-brain model to mimic the physiological and pharmacological processes in vitro and presents a simple platform for long-term cell co-culture, drug delivery and metabolism, and real-time analysis of drug effects on brain cancer.

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.

Probing prodrug metabolism and reciprocal toxicity with an integrated and humanized multi-tissue organ-on-a-chip platform.

Current drug development techniques are expensive and inefficient, partially due to the use of preclinical models that do not accurately recapitulate in vivo drug efficacy and cytotoxicity. To address this challenge, we report on an integrated, in vitro multi-organoid system that enables parallel assessment of drug efficiency and toxicity on multiple 3D tissue organoids. Built in a low-cost, adhesive film-based microfluidic device, these miniaturized structures require less than 200 µL fluid volume and are amenable to both matrix-based 3D cell culture and spheroid aggregate integration, each supported with an in situ photocrosslinkable hyaluronic acid hydrogel. Here, we demonstrate this technology first with a three-organoid device consisting of liver, cardiac, and lung constructs. We show that these multiple tissue types can be kept in common circulation with high viability for 21 days and validate the platform by investigating liver metabolism of the prodrug capecitabine into 5-fluorouracil (5-FU) and observing downstream toxicity in lung and cardiac organoids. Then we expand the integrated system to accommodate six humanized constructs, including liver, cardiac, lung, endothelium, brain, and testes organoids. Following a 14-day incubation in common media, we demonstrate multi-tissue interactions by metabolizing the alkylating prodrug ifosfamide in the liver organoid to produce chloroacetaldehyde and induce downstream neurotoxicity. Our results establish an expandable, multi-organoid body-on-a-chip system that can be fabricated easily and used for the accurate characterization of drug interactions in vitro. STATEMENT OF SIGNIFICANCE: The use of 3-dimensional (3D) in vitro models in drug development has advanced over the past decade. However, with several exceptions, the majority of research studies using 3D in vitro models, such as organoids, employ single tissue types, in isolated environments with no "communication" between different tissues. This is a significant limiting factor because in the human body there is significant signaling between different cells, tissues, and organs. Here we employ a low-cost, adhesive film-based microfluidic device approach, paired with a versatile extracellular matrix-derived hyaluronic acid hydrogel to support integrated systems of 3 and 6 3D organoid and cell constructs. Moreover, we demonstrate an integrated response to drugs, in which downstream toxicity is dependent on the presence of liver organoids.

Probing the binding mechanism of capecitabine to human serum albumin using spectrometric methods, molecular modeling, and chemometrics approach.

Capecitabine as a prodrug of 5-Fluorouracil plays an important role in the treatment of breast and gastrointestinal cancers. Herein, in view of the importance of this drug in chemotherapy, interaction mechanism between Capecitabine (CAP) and human serum albumin (HSA) as a major transport protein in the blood circulatory system has been investigated by using a combination of spectroscopic and molecular modeling methods. The fluorescence spectroscopic results revealed that capecitabine could effectively quench the intrinsic fluorescence of HSA through a static quenching mechanism. Evaluation of the thermodynamic parameters suggested that the binding process was spontaneous while hydrogen bonds and van der Waals forces played a major role in this interaction. The value of the binding constant (Kb = 1.820 × 104) suggested a moderate binding affinity between CAP and HSA which implies its easy diffusion from the circulatory system to the target tissue. The efficiency of energy transfer and the binding distance between the donor (HSA) and acceptor (CAP) were determined according to forster theory of nonradiation energy transfer as 0.410 and 4.135 nm, respectively. Furthermore, UV-Vis spectroscopic results confirmed that the interaction was occurred between HSA and CAP and caused conformational and micro-environmental changes of HSA during the interaction. Multivariate curve resolution-alternating least square (MCR-ALS) methodology as an efficient chemometric tool was used to separate the overlapped spectra of the species. The MCR-ALS result was exploited to estimate the stoichiometry of interaction and to provide concentration and structural information about HSA-CAP interactions. Molecular docking studies suggested that CAP binds mainly to the subdomain IIA of HSA, which were compatible with those obtained by experimental data. Finally, molecular dynamics simulation (MD) was performed on the best docked complex by considering the permanence and flexibility of HSA-CAP complex in the binding site. MD result showed that CAP could steadily bind to HSA in the site I based on the formation of hydrogen bond and π-π stacking interaction in addition to hydrophobic force.

A molecular basis for the synergy between 17­allylamino­17­demethoxy geldanamycin with Capecitabine and Irinotecan in human colorectal cancer cells through VEFG and MMP-9 gene expression.

Anti-proliferative, anti-metastatic and anti-angiogenic effects of 17­allylamino­17­demethoxy geldanamycin (17-AAG) were studied alone and in combination with Capecitabine (Cap) and/or Irinotecan (IR) on HT-29 human colorectal carcinoma cells. Expression of MMP-9 (matrix metalloproteinase­9) and VEGF (vascular endothelial growth factor) mRNA was analyzed by real-time PCR method. The study was further followed by wound scratch assay for migration assessment. Nitric oxide content, Malondialdehyde generation and total anti-oxidant capacity were also assessed. Results showed significant differences between mono- and double therapy (p < 0.05). Combination of 17-AAG with IR or Cap resulted in synergistic effect (Combination Index < 1). Among double combination groups only Cap/17-AAG showed significant differences in MMP-9 and VEGF genes expression and wound healing assay. Moreover, a significant decrease of wound area in our triple combination group was obtained, indicating the antagonistic effect. IR/17-AAG and IR/Cap double combination groups resulted in down-regulation of MMP-9 and VEGF mRNA expression, respectively. Significant generation of MDA and decrease in TAC values have been observed in all our tested groups, however, the IR/17-AAG combination was the only group that could elevate NO concentration, significantly. Our findings demonstrated potent anti-angiogenesis and anti-metastatic effects for 17-AAG when it is provided in double combination especially with Cap, suggesting a new protocol in colorectal cancer combination therapy. These findings may indicate that down-regulation of VEGF and MMP-9 genes is directly related to angiogenesis and metastasis.

A new, sensitive and versatile assay for quantitative determination of α-fluoro-ß-alanine (AFBA) in human urine by using the reversed-phase ultrahigh performance-tandem mass spectrometry (rp-UHPLC-MS/MS) system.

A method for the quantitation of α-fluoro-ß-alanine (AFBA), the main metabolite of capecitabine (Cape) and 5-fluoruracil (5-FU), is described. Among antineoplastic drugs (ADs), 5-FU and Cape (the new oral prodrug) are the most commonly applied drugs in cancer therapy. The main objective of this study was to develop a reliable method that would be easy to run on a reversed-phase UHPLC system coupled to tandem mass spectrometry. AFBA was derivatized with Sanger's reagent to ensure complete yield of a stable 2,4 dinitrophenil-α-fluoro-ß-alanine derivative. This method was based on the use of a mixed-mode anion exchange solid phase extraction enabling urinary extracts to be clear of endogenous interferences affecting quantitative results. The assay was validated in human urine according to FDA criteria with the use of a labeled internal standard (ß-alanine-d4) to minimize experimental error. Good accuracy and precision were demonstrated by determining spiked urine QC samples in four consecutive days. The recovery of AFBA was between 70.0 and 82.6%, with a matrix effect that was 12.8%-18.5%. The lower limit of quantitation (LOQ) was 0.5 ng/mL with a coefficient of variation of 5.3%. This assay was successfully applied to determine the levels of this metabolite in a large number of urine samples taken from personnel who were occupationally exposed to ADs.

Identification of the Novel Capecitabine Metabolites in Capecitabine-Treated Patients with Hand-Foot Syndrome.

Hand-foot syndrome (HFS), the most common side effect of capecitabine, is a dose-limiting cutaneous toxicity with only rare therapeutic options. The causative mechanisms of HFS are still unclear. Many studies suggested that capecitabine or its metabolites caused the toxicity. This study is attempting to determine if there are any new metabolites that may be present and be linked to toxicity. For this purpose, 25 patients who ingested capecitabine orally were enrolled and divided into HFS positive and negative groups. Urine and plasma samples were collected before administration and five cycles after administration. Eleven phase I and phase II metabolites of capecitabine were detected and identified by ultraperformance liquid chromatography coupled with quadrupole time-of-flight tandem mass spectrometry with a metabolomic approach and MetaboLynxXS. Nine novel metabolites of capecitabine were identified herein, which were not observed in the HFS negative group. Their structures were confirmed by chemical synthesis and nuclear magnetic resonance spectroscopy. The cytotoxities of capecitabine and its metabolites on HaCaT cells were measured. Among them, M9/10 exhibited significant inhibitory activity, and they were produced via acetylation mainly by N-acetyltransferase 2. Our study comprehensively described the metabolism of capecitabine in patients with HFS and detected the novel pathways of capecitabine, which was a positive significance for the mechanism of HFS.

Capecitabine encapsulated chitosan succinate-sodium alginate macromolecular complex beads for colon cancer targeted delivery: in vitro evaluation.

The present study aims to investigate the efficacy of the novel biopolymeric complex multiparticulate system consisting of chitosan succinate and alginate for the capecitabine-targeted delivery to colon cancer. A Box-Behnken design was used to optimize the CS-SA beads by considering the effect of three factors: CS (A;X1), CaCl2 (B;X2), and SA (C;X3), on the response variables Y1 (EE), Y2 (Size), and Y3 (Release). The results of response surface plots allowed an optimized bead to be identified with high drug EE and maximum drug release at colon. The swelling index showed that the beads reached a maximum good swelling at pH 7.4, and nil or little swelling at acidic pH, which proves that the beads completely protect the release of drug. The in vitro release portrayed a maximum release at pH 7.4, due to the large swelling force that was created by electrostatic repulsion between the ionized carboxylic acid groups of the CS-SA network. In vitro cytotoxicity assay (MTT) of CS-SA beads shows inhibition of the proliferation of HT-29 tumour cell to induce apoptosis over a longer period of time. The above results show that CS-SA beads prolong the release of CP in the colonic region, and also enhance antitumor efficacy.

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.

Functionally modified polyacrylamide-graft-gum karaya pH-sensitive spray dried microspheres for colon targeting of an anti-cancer drug.

An effort was made to formulate and evaluate pH-sensitive spray dried microspheres using hydrolyzed polyacrylamide-graft-gum karaya (PAAm-g-GK) for colon specific delivery of an anti-cancer agent, capecitabine. The synthesis of pH-sensitive PAAm-g-GK copolymer was done by free radical polymerization followed by alkaline hydrolysis and characterized satisfactorily. The microspheres were spherical in shape; drug entrapment efficiency was found to be in the range of 77.30% to 88.74%. Pulsatile swelling study indicates that the PAAm-g-GK consists of considerable pH-sensitivity. The in-vitro drug release suggested that the microspheres prepared using native GK were incapable to retard the drug release within 5h in the environment of stomach and small intestine. While, those microspheres prepared using pH-sensitive PAAm-g-GK copolymer having crosslinked with glutaraldehyde (GA), released little amount of drug within 5h, but maximum amount of drug was targeted to colonic region in a controlled manner up to 24h. For example, GK10 Microspheres showed only 19.16% drug release at the end of 5th h, while about 80.14% of drug was targeted to colonic region. Cross-linking with GA reduced the early drug release in the upper part of gastrointestinal tract and guaranteed maximum drug release in the colonic region. A rapid enhancement in drug release was witnessed in rat caecal content medium due to the action of colonic bacteria on PAAm-g-GK copolymer.

Novel spray dried pH-sensitive polyacrylamide-grafted-carboxymethylcellulose sodium copolymer microspheres for colon targeted delivery of an anti-cancer drug.

Unique pH-sensitive spray dried microspheres were formulated employing hydrolyzed polyacrylamide-g-carboxymethylcellulose sodium (PAAm-g-NaCMC) co-polymer for colon targeted delivery of an anticancer drug, capecitabine. Synthesis of PAAm-g-NaCMC was carried out through free radical polymerization, which was supported with an inert atmosphere and then the alkaline hydrolysis was performed and subjected for characterization including FTIR spectroscopic analysis, 1H NMR spectroscopic analysis, elemental analysis, viscosity measurement, neutralization equivalent and thermo-gravimetric investigation. The swelling data suggested that the PAAm-g-NaCMC possesses significant pH-sensitive property. The microspheres were in the range of 1.00 to 7.34 µ and the drug entrapment efficiency ranged between 70.98 and 94.41%. In vitro drug release suggested the failure of microspheres formulated using native NaCMC which failed to impede drug release in stomach and small intestine, while those prepared with pH-sensitive PAAm-g-NaCMC copolymer and cross-linked with glutaraldehyde are suitable for colon targeting because they retarded release of drug in physiologic atmosphere of stomach and small intestine. Only 12.97% of drug was released from CMC10 formulation by the end of 5th h and rest of drug has been targeted to colonic region. A sudden increase in release of drug was observed in rat caecal contents media because of colonic bacterial action on PAAm-g-NaCMC copolymer.

The role of pharmacogenetics in capecitabine efficacy and toxicity.

Capecitabine is an oral prodrug of 5-fluorouracil (5-FU) and approved for treatment of various malignancies. Hereditary genetic variants may affect a drug's pharmacokinetics or pharmacodynamics and account for differences in treatment response and adverse events among patients. In this review we present the current knowledge on genetic variants, commonly single-nucleotide polymorphisms (SNPs), tested in cohorts of cancer patients and possibly useful for prediction of capecitabine efficacy or toxicity. Capecitabine is activated to 5-FU by CES, CDA and TYMP, of which SNPs in CDA and CES2 were found to be associated with efficacy and toxicity. In addition, variants in genes of the 5-FU metabolic pathway, including TYMS, MTHFR and DPYD also influenced capecitabine efficacy and toxicity. In particular, well-known SNPs in TYMS and DPYD as well as putative DPYD SNPs had an association with clinical outcome as well as adverse events. Inconsistent findings may be attributable to factors related to ethnic differences, sample size, study design, study endpoints, dosing schedule and the use of multiple agents. Of the SNPs described in this review, dose reduction of fluoropyrimidines based on the presence of DPYD variants *2A (rs3918290), *13 (rs55886062), -2846A>T (rs67376798) and -1236G>A/HapB3 (rs56038477) has already been recommended. Other variants merit further validation to establish their definite role in explanation of interindividual differences in the outcome of capecitabine-based therapy.

Comparative analysis of the interaction of capecitabine and gefitinib with human serum albumin using (19)F nuclear magnetic resonance-based approach.

Monitoring the interaction between drugs and proteins is critical to understanding drug transport and metabolism underlying pharmacodynamics. The binding capacities to human serum albumin of two anticancer drugs, capecitabine and gefitinib, were compared via an approach combining (19)F NMR, (1)H saturation transfer difference (STD) NMR, circular dichroism and docking simulations. Results showed that the two drugs interaction with human serum albumin caused (19)F NMR signal shifted to different directions. Capecitabine had accurate binding site and higher binding affinity than gefitinib. This study provided fresh insights into ligand-protein interaction and the strength of (19)F NMR approach in biomedical research was well illustrated in this case.

(19)F MRSI of capecitabine in the liver at 7 T using broadband transmit-receive antennas and dual-band RF pulses.

Capecitabine (Cap) is an often prescribed chemotherapeutic agent, successfully used to cure some patients from cancer or reduce tumor burden for palliative care. However, the efficacy of the drug is limited, it is not known in advance who will respond to the drug and it can come with severe toxicity. (19)F Magnetic Resonance Spectroscopy (MRS) and Magnetic Resonance Spectroscopic Imaging (MRSI) have been used to non-invasively study Cap metabolism in vivo to find a marker for personalized treatment. In vivo detection, however, is hampered by low concentrations and the use of radiofrequency (RF) surface coils limiting spatial coverage. In this work, the use of a 7T MR system with radiative multi-channel transmit-receive antennas was investigated with the aim of maximizing the sensitivity and spatial coverage of (19)F detection protocols. The antennas were broadband optimized to facilitate both the (1)H (298 MHz) and (19)F (280 MHz) frequencies for accurate shimming, imaging and signal combination. B1(+) simulations, phantom and noise measurements showed that more than 90% of the theoretical maximum sensitivity could be obtained when using B1(+) and B1(-) information provided at the (1)H frequency for the optimization of B1(+) and B1(-) at the (19)F frequency. Furthermore, to overcome the limits in maximum available RF power, whilst ensuring simultaneous excitation of all detectable conversion products of Cap, a dual-band RF pulse was designed and evaluated. Finally, (19)F MRS(I) measurements were performed to detect (19)F metabolites in vitro and in vivo. In two patients, at 10 h (patient 1) and 1 h (patient 2) after Cap intake, (19)F metabolites were detected in the liver and the surrounding organs, illustrating the potential of the set-up for in vivo detection of metabolic rates and drug distribution in the body.

An in vitro liver model on microfluidic device for analysis of capecitabine metabolite using mass spectrometer as detector.

In this work, an in vitro liver model in a microfluidic device to imitate and detect prodrug metabolism was developed. A widely used prodrug capecitabine (CAP), which needs to be metabolized into active intermediate in the liver and then transformed into final effective drug in tumor cells, was selected as a model compound. The microfluidic device we exploited consists of a cell co-culture section, in which HepG2 cells were cultured to represent liver while MCF-7 cells were used to represent the tumor tissue, and an on-line solid phase extraction (SPE) section connecting to the ionization source of the ESI-Q-TOF mass spectrometer. The prodrug metabolism was realized and confirmed within this in vitro liver model as the intermediate product of the prodrug 5'-deoxy-5-fluorouridine (DFUR) was successfully detected with MS after the conditioning of HepG2 cells, and the anti-tumor effect of the active metabolite was observed through cell vitality assays of MCF-7 cells. The limit of detection (LOD) using on-chip SPE was at 10nM and semi-quantitative analysis could be realized. This system has been proved useful and practical, showing a potential to replace conventional drug screening methods.