Construction of EVA/chitosan based PEG-PCL micelles nanocomposite films with controlled release of iprodione and its application in pre-harvest treatment of grapes.

A novel nanocomposite poly(ethylene-co-vinyl acetate) (EVA) film with controlled in vitro release of iprodione (ID) was prepared. Chitosan (CS) was used as the reinforcement which enhances the water and oxygen permeability of films. ID loaded poly(ethylene glycol)-poly(ε-caprolactone) (PEG-PCL) (IPP) micelles were used as the drug carrier which endows the films with antifungal and controlled release ability. IPP micelles with spherical shape and uniform size were obtained, and the maximum encapsulation efficacy (EE) was 91.17 ± 5.03% by well controlling the feeding amount of ID. Incorporation CS could improve the oxygen and moisture permeability of films, and the maximum oxygen permeability (OP) and water vapor transmission rate (WVTR) were 477.84 ± 13.03 cc/(m2·d·0.1 MPa) and 8.60 ± 0.25 g m-2 d-1, respectively. After loading IPP micelles, the films showed an improved antifungal ability and temperature-sensitive drug release behavior, and were found to enhance the quality of grapes by pre-harvest spraying.

Metabolomics and proteomics identify the toxic form and the associated cellular binding targets of the anti-proliferative drug AICAR.

5-Aminoimidazole-4-carboxamide 1-ß-d-ribofuranoside (AICAR, or acadesine) is a precursor of the monophosphate derivative 5-amino-4-imidazole carboxamide ribonucleoside 5'-phosphate (ZMP), an intermediate in de novo purine biosynthesis. AICAR proved to have promising anti-proliferative properties, although the molecular basis of its toxicity is poorly understood. To exert cytotoxicity, AICAR needs to be metabolized, but the AICAR-derived toxic metabolite was not identified. Here, we show that ZMP is the major toxic derivative of AICAR in yeast and establish that its metabolization to succinyl-ZMP, ZDP, or ZTP (di- and triphosphate derivatives of AICAR) strongly reduced its toxicity. Affinity chromatography identified 74 ZMP-binding proteins, including 41 that were found neither as AMP nor as AICAR or succinyl-ZMP binders. Overexpression of karyopherin-ß Kap123, one of the ZMP-specific binders, partially rescued AICAR toxicity. Quantitative proteomic analyses revealed 57 proteins significantly less abundant on nuclei-enriched fractions from AICAR-fed cells, this effect being compensated by overexpression of KAP123 for 15 of them. These results reveal nuclear protein trafficking as a function affected by AICAR.

Characterization of a novel AICARFT inhibitor which potently elevates ZMP and has anti-tumor activity in murine models.

AICARFT is a folate dependent catalytic site within the ATIC gene, part of the purine biosynthetic pathway, a pathway frequently upregulated in cancers. LSN3213128 is a potent (16 nM) anti-folate inhibitor of AICARFT and selective relative to TS, SHMT1, MTHFD1, MTHFD2 and MTHFD2L. Increases in ZMP, accompanied by activation of AMPK and cell growth inhibition, were observed with treatment of LY3213128. These effects on ZMP and proliferation were dependent on folate levels. In human breast MDA-MB-231met2 and lung NCI-H460 cell lines, growth inhibition was rescued by hypoxanthine, but not in the A9 murine cell line which is deficient in purine salvage. In athymic nude mice, LSN3213128 robustly elevates ZMP in MDA-MB-231met2, NCI-H460 and A9 tumors in a time and dose dependent manner. Significant tumor growth inhibition in human breast MDA-MB231met2 and lung NCI-H460 xenografts and in the syngeneic A9 tumor model were observed with oral administration of LSN3213128. Strikingly, AMPK appeared activated within the tumors and did not change even at high levels of intratumoral ZMP after weeks of dosing. These results support the evaluation of LSN3213128 as an antineoplastic agent.

Regulation of hepatic glucose production and AMPK by AICAR but not by metformin depends on drug uptake through the equilibrative nucleoside transporter 1 (ENT1).

AIM: Recently we have observed differences in the ability of metformin and AICAR to repress glucose production from hepatocytes using 8CPT-cAMP. Previous results indicate that, in addition to activating protein kinase A, 8CPT-modified cAMP analogues suppress the nitrobenzylthioinosine (NBMPR)-sensitive equilibrative nucleoside transporter ENT1. We aimed to exploit 8CPT-cAMP, 8CPT-2-Methyl-O-cAMP and NBMPR, which is highly selective for a high-affinity binding-site on ENT1, to investigate the role of ENT1 in the liver-specific glucose-lowering properties of AICAR and metformin. METHODS: Primary mouse hepatocytes were incubated with AICAR and metformin in combination with cAMP analogues, glucagon, forskolin and NBMPR. Hepatocyte glucose production (HGP) and AMPK signalling were measured, and a uridine uptake assay with supporting LC-MS was used to investigate nucleoside depletion from medium by cells. RESULTS: AICAR and metformin increased AMPK pathway phosphorylation and decreased HGP induced by dibutyryl cAMP and glucagon. HGP was also induced by 8CPT-cAMP, 8CPT-2-Methyl-O-cAMP and NBMPR; however, in each case this was resistant to suppression by AICAR but not by metformin. Cross-validation of tracer and mass spectrometry studies indicates that 8CPT-cAMP, 8CPT-2-Methyl-O-cAMP and NBMPR inhibited the effects of AICAR, at least in part, by impeding its uptake into hepatocytes. CONCLUSIONS: We report for the first time that suppression of ENT1 induces HGP. ENT1 inhibition also impedes uptake and the effects of AICAR, but not metformin, on HGP. Further investigation of nucleoside transport may illuminate a better understanding of how metformin and AICAR each regulate HGP.

Bioaugmentation and rhizosphere-assisted biodegradation as strategies for optimization of the dissipation capacity of biobeds.

Biobeds are on-farm biodepuration systems whose efficiency rely on their high pesticide biodegradation capacity. We evaluated two optimization strategies, bioaugmentation and/or rhizosphere-assisted biodegradation, to maximize the dissipation capacity of biobeds. Iprodione was used as a model pesticide. Its dissipation and metabolism was determined in a biobed packing material inoculated with an iprodione-degrading Arthrobacter strain C1 (bioaugmentation, treatments B+C1) and/or seeded with ryegrass (rhizosphere-assisted biodegradation, treatments B+P). The impact of those strategies on the activity and composition of the microbial community was determined. Bioaugmentation accelerated the dissipation of iprodione which was further enhanced in the bioaugmented, rhizosphere-assisted treatment (treatment B+P+C1, Half-life (DT50) = 3.4 d), compared to the non-bioaugmented, non rhizosphere-assisted control (DT50 = 9.5 d, treatment B). Bioaugmentation resulted in the earlier formation of intermediate formation of metabolites I (3,5-dichlorophenyl-carboxamide), II (3,5-dichlorophenylurea acetate) and 3,5-dichloroaniline (3,5-DCA). The latter was further dissipated by the indigenous microbial community. Acid phosphatase (AP) and ß-glucosidase (GLU) were temporarily stimulated in rhizosphere-assisted treatments, whereas a stimulation of the fluorescein diacetate (FDA) hydrolytic activity in the bioaugmented treatments coincided with the hydrolysis of iprodione. q-PCR showed that changes in the abundance of alpha-proteobacteria and firmicutes was driven by the presence of rhizosphere while bioaugmentation had no significant effect.

A HPLC method for simultaneous determination of 5-aminoimidazole-4-carboxamide riboside and its active metabolite 5-aminoimidazole-4-carboxamide ribotide in tumor-bearing nude mice plasma and its application to pharmacokinetics study.

A HPLC method with on-line solid phase extraction (SPE) and column switching was developed for simultaneous determination of 5-aminoimidazole-4-carboxamide riboside (AICA riboside) and its active metabolite 5-aminoimidazole-4-carboxamide ribotide (AICA ribotide) in nude mice plasma. Plasma sample was deproteinized by adding a half volume of 10% trichloroacetic acid (TCA), and the resulting supernatant was extracted with diethyl ether to remove TCA. 50 µl aqueous fraction was injected onto a WAX-1 SPE column, and AICA ribotide was trapped on the SPE column, while AICA riboside was eluted from the SPE column. The chromatographic separation of AICA riboside was achieved on CG16 column, and separation of AICA ribotide was performed on HILIC-10 and WAX-1 column. The columns temperature was maintained at 40 °C, and the optimal detection wavelength was 268 nm for both AICA riboside and AICA ribotide. The total analytical run time was 40 min. The proposed method was linear over the range of 0.1-500 µg/ml for AICA riboside and 0.03-50 µg/ml for AICA ribotide. The lower limit of quantification (LLOQ) was 100 and 30 ng/ml for AICA riboside and AICA ribotide, respectively. The sensitivity, accuracy and precision of this method were within acceptable limits during validation period. The method was successfully applied to investigate the pharmacokinetics characteristics of AICA riboside and its active metabolite AICA ribotide in nude mice bearing MCF-7 cell xenografts.

Acadesine for patients with relapsed/refractory chronic lymphocytic leukemia (CLL): a multicenter phase I/II study.

PURPOSE: Acadesine has shown in vitro to selectively induce apoptosis in B cells from chronic lymphocytic leukemia (CLL) patients. We conducted a phase I/II open-label clinical study, to determine the safety and tolerability of acadesine given intravenously as a 4-h infusion to CLL patients. METHODS: Patient population included CLL patients with relapsed/refractory disease who had received one or more prior lines of treatment including either a fludarabine or an alkylator-based regimen. Twenty-four patients were included: eighteen in Part I treated at single doses of 50-315 mg/kg, and six in Part II, three with two doses at 210 mg/kg and three with five doses at 210 mg/kg. RESULTS: A manageable and predictable safety profile was demonstrated for acadesine at single doses between 50 and 210 mg/kg; 210 mg/kg was the maximum tolerated dose (MTD) and optimal biological dose (OBD). Grade ≥2 hyperuricemia occurred commonly but was not clinically significant and resolved with the administration of prophylactic allopurinol. Other adverse events included transient anemia and/or thrombocytopenia (not clinically significant), renal impairment, and transient infusion-related hypotension (clinically significant). Trends of efficacy such as a reduction of peripheral CLL cells and reduction in lymphadenopathy were observed; however, the results were variable due to the small population and the range of doses tested. CONCLUSIONS: A MTD of 210 mg/kg was established with single acadesine dose. Multiple dose administrations at the OBD were tested with an acceptable safety profile, showing that acadesine might be a valuable agent for the treatment of relapsed/refractory CLL patients.

Intravenous AICAR during hyperinsulinemia induces systemic hemodynamic changes but has no local metabolic effect.

AMPK activation may stimulate glucose uptake in skeletal muscle, but the results in humans have so far been inconclusive. The authors investigated whether infusion of the AMPK activator, 5-aminoimidazole-4-carboxamide-riboside (AICAR), increased whole-body glucose infusion rate (GIR) and forearm skeletal muscle glucose uptake (FGU) during hyperin-sulinemia in vivo in healthy humans. Ten participants (paired data: n = 8) underwent 2 euglycemic hyperinsulinemic clamps (60 mU·m(-2)·min(-1), 120 minutes) with concomitant AICAR (67 mg·kg(-1)) or placebo (saline) administration over the last 60 minutes. The authors also measured forearm blood flow (FBF; plethysmography), heart rate, blood pressure, and AICAR and AICA-ribotide (ZMP) concentrations in plasma and erythrocytes. FGU and GIR (T = 95-120 min) did not differ between insulin + AICAR and insulin + placebo. Compared with insulin + placebo, insulin + AICAR raised heart rate more profoundly (T = 60-120 minutes: from 58 ± 3 to 70 ± 3 vs 60 ± 4 to 63 ± 4 bpm for placebo; P < .05 between treatments) and lowered blood pressure significantly. AICAR plasma concentrations increased significantly during AICAR infusion; AICAR was rapidly taken up by erythrocytes and phosphorylated to ZMP. In conclusion, AICAR does not seem to have a direct effect on systemic or local glucose uptake in humans. AICAR increases heart rate and decreases blood pressure, most likely by systemic vasodilation.

Pharmacokinetic results of a phase I trial of sorafenib in combination with dacarbazine in patients with advanced solid tumors.

PURPOSE: Sorafenib, a multikinase inhibitor of Raf and several growth factor receptors, is under investigation in combination with dacarbazine, a commonly used chemotherapeutic agent for the treatment of many cancers. The current phase I study investigates the effects of sorafenib on the pharmacokinetic (PK) profile of dacarbazine and its metabolite 5-amino-imidazole-4-carboxamide (AIC). (AIC is formed in amounts equimolar to the active alkylating moiety, methane diazohydroxide, which is undetectable by known validated assays.) METHODS: Patients with advanced solid tumors received intravenous dacarbazine 1,000 mg/m(2) on day 1 of a 21-day cycle to evaluate the PK of dacarbazine alone. Sorafenib 400 mg was administered twice daily continuously starting at day 2 of cycle 1. The PK of dacarbazine in the presence of sorafenib was assessed on day 1 of cycle 2. Sorafenib PK was also assessed at steady state. RESULTS: PK data were available for 15 of 23 patients. With concomitant administration of sorafenib, the mean AUC and C (max) values of dacarbazine were reduced by 23 and 16%, respectively. Mean AUC and C (max) values of AIC were increased by 41 and 45%, respectively, with individual increases of up to 106 and 136%, respectively. The apparent terminal half-lives of the two compounds were not significantly influenced by sorafenib. Based on coefficients of variation, the AUC and C (max) values for sorafenib and its three metabolites were highly variable with dacarbazine coadministration. CONCLUSIONS: Concomitant administration of sorafenib and dacarbazine as described above may result in decreased dacarbazine exposure but increased AIC exposure.

Validated hydrophilic interaction LC-MS/MS method for simultaneous quantification of dacarbazine and 5-amino-4-imidazole-carboxamide in human plasma.

A hydrophilic interaction high performance liquid chromatography-tandem mass spectrometric method has been developed and validated for simultaneous quantification of dacarbazine (DTIC) and its terminal metabolite, 5-amino-4-imidazole-carboxamide (AIC) in human plasma. The plasma samples are first extracted by a C8+SCX mixed-mode 96-well plate to extend the extraction stability of DTIC and AIC. The extracted residues are further cleaned by a primary and secondary amine (PSA) adsorbent for minimization of matrix effect. Analyses are done on an Amide-80 HPLC column coupled to a tandem mass spectrometer fitted with an atmospheric pressure turbo ion spray ionization interface in the positive-ion mode. Both DTIC and AIC have reproducible retention times on the Amide-80 HPLC column. This type of column not only has an excellent column life (over 4000 injections), but also has zero carryover effect. The injection volume should be limited at 10 microL or less to avoid the peak splitting. The validated concentration ranges are from 0.5 to 500 ng/mL for DTIC and from 2.0 to 500 ng/mL for AIC. The validated method has been successfully applied to determine the pharmacokinetic profiles for human patients receiving DTIC infusions.

Synthesis of new carbon-11-labeled carboxamide derivatives as potential PET dopamine D3 receptor radioligands.

Carbon-11-labeled carboxamide derivatives, (E)-4-fluoro-N-(4-(4-(2-[(11)C]methoxyphenyl)piperazin-1-yl)butyl)cinnamoylamide, ([(11)C]3a), (E)-4-chloro-N-(4-(4-(2-[(11)C]methoxyphenyl)piperazin-1-yl)butyl)cinnamoylamide ([(11)C]3b), (E)-4-bromo-N-(4-(4-(2-[(11)C]methoxyphenyl)piperazin-1-yl)butyl)cinnamoylamide, ([(11)C]3c), (E)-4-methoxy-N-(4-(4-(2-[(11)C]methoxyphenyl)piperazin-1-yl)butyl)cinnamoylamide ([(11)C]3d), N-(4-(4-(2-[(11)C]methoxyphenyl)piperazin-1-yl)butyl)naphthyl-2-carboxamide ([(11)C]BP897, [(11)C]3e), and N-(4-(4-(2-[(11)C]methoxyphenyl)piperazin-1-yl)butyl)biphenyl-4-carboxamide ([(11)C]3f), have been synthesized as new potential PET radioligands for imaging of dopamine D(3) receptors. The target tracers were prepared by O-[(11)C]methylation of their corresponding precursors using [(11)C]CH(3)OTf and isolated by a simplified solid-phase extraction (SPE) purification procedure in 50-65% radiochemical yields decay corrected to end of bombardment (EOB), 20 min overall synthesis time, and 111-148GBq/micromol specific activity at end of synthesis (EOS).

Acadesine: AICA riboside, ARA 100, arasine, GP 1 110.

Acadesine is an adenosine receptor agonist (ARA) in development for the treatment of ischaemia-reperfusion injury and chronic lymphocytic leukaemia. Schering-Plough is developing the compound as a cardioprotective agent in ischaemia-reperfusion injury. Avancell and Protherics are co-developing acadesine for the treatment of B-cell chronic lymphocytic leukaemia (B-CLL). Clinical development is underway for both indications. In January 2005, PeriCor Therapeutics obtained a sublicense for the worldwide rights to acadesine and three additional ARA compounds from Dr Mangano who was a founder of the company. Dr Mangano acquired the license of worldwide rights for acadesine from Metabasis in November 2000.Previously, in December 1997, all intellectual property rights and data covering acadesine and related ARAs for cardiovascular and cerebrovascular disorders were transferred from the original developer, Gensia Sicor (SICOR), to Metabasis Therapeutics in an asset-liability transfer agreement.Schering-Plough intends to conduct a randomized, placebo-controlled phase III trial, which is required for regulatory approval. The trial will further evaluate acadesine in patients deemed to be at high risk of ischaemic heart disorders. Patients will have either undergone coronary artery bypass graft surgery, or have a history of cardiovascular events (heart attack or stroke). Protherics presented 2-year mortality results from a study of acadesine, investigating long-term mortality after perioperative myocardial infarction, at the 55th Scientific Session of the American College of Cardiology in 2006.Previously, Gensia Sicor conducted clinical trials of acadesine in Canada, the EU and the US; results of these trials were inconclusive. Acadesine has been shown to selectively cause the death of B-cells, whilst sparing T-cells when administered to blood samples taken from patients with B-CLL. Orphan drug status has been granted for acadesine in the EU for the treatment of B-cell chronic lymphocytic leukaemia.

Determination of 5-aminoimidazole-4-carboxamide in human plasma by ion-pair extraction and LC-MS/MS.

A liquid chromatography/tandem mass spectrometry (LC-MS/MS) method was established for the determination of 5-aminoimidazole-4-carboxamide (AICA) in human plasma. The method included a solvent extraction of AICA as an ion pair with 1-pentanesulfonate ion and a separation on a Hypersil ODS2 column with the mobile phase of methanol-water (68:32, v/v). Determination was performed using an electrospray ionization source in positive ion mode (ESI(+)). Multiple reaction monitoring (MRM) was utilized for the detection monitoring m/z at 127-->110 for AICA, and 172-->128 for IS. The calibration curve was linear within a range from 20 to 2000 ng/mL and the limit of quantity for AICA in plasma was 20 ng/mL. RSD of intra-assay and inter-assay were no more than 5.90% and 5.65%.

Analysis of 3,5-dichloroaniline as a biomarker of vinclozolin and iprodione in human urine using liquid chromatography/triple quadrupole mass spectrometry.

The fungicides vinclozolin and iprodione are widely used in agriculture. These pesticides are dicarboximide fungicides containing the common moiety 3,5-dichloroaniline (3,5-DCA). It has been suggested that low-level exposures to such compounds may be associated with adverse health effects such as endocrine disruption. In this study a method using liquid chromatography/triple quadrupole mass spectrometry (LC/MS/MS) was developed for the analysis of 3,5-DCA as a biomarker of exposure to these fungicides in human urine. The urine samples were treated by basic hydrolysis to degrade the fungicides, their metabolites and conjugates to 3,5-DCA. The 3,5-DCA was then extracted using toluene and derivatized using pentafluoropropionic anhydride (PFPA). Analysis of the derivative was carried out using selected reaction monitoring (SRM) in the negative ion mode. Quantification of the derivative was performed using [(13)C(6)]-labeled 3,4-DCA as an internal standard with good precision and linearity in the range 0.1-200 ng/mL urine. The limit of detection was determined to be 0.1 ng/mL. The metabolites in urine were found to be stable during storage at -20 degrees C. To validate 3,5-DCA as a biomarker the method was applied in a human experimental exposure to iprodione and vinclozolin. Two healthy volunteers received 200 microg single oral doses of each pesticide followed by urine sampling during 72-120 h post-exposure. Between 78-107% of the dose was recovered as 3,5-DCA in the urine after exposure.

Methotrexate enhances the antianabolic and antiproliferative effects of 5-aminoimidazole-4-carboxamide riboside.

Because of its ability to mimic a low energy status of the cell, the cell-permeable nucleoside 5-aminoimidazole-4-carboxamide (AICA) riboside was proposed as an antineoplastic agent switching off major energy-consuming processes associated with the malignant phenotype (lipid production, DNA synthesis, cell proliferation, cell migration, etc.). Key to the antineoplastic action of AICA riboside is its conversion to ZMP, an AMP mimetic that at high concentrations activates the AMP-activated protein kinase (AMPK). Here, in an attempt to increase the efficacy of AICA riboside, we pretreated cancer cells with methotrexate, an antimetabolite blocking the metabolism of ZMP. Methotrexate enhanced the AICA riboside-induced accumulation of ZMP and led to a decrease in the levels of ATP, which functions as an intrasteric inhibitor of AMPK. Consequently, methotrexate markedly sensitized AMPK for activation by AICA riboside and potentiated the inhibitory effects of AICA riboside on tumor-associated processes. As cotreatment elicited antiproliferative effects already at concentrations of compounds that were only marginally effective when used alone, our findings on the cooperation between methotrexate and AICA riboside provide new opportunities both for the application of classic antimetabolic chemotherapeutics, such as methotrexate, and for the exploitation of the energy-sensing machinery as a target for cancer intervention.

AICA riboside both activates AMP-activated protein kinase and competes with adenosine for the nucleoside transporter in the CA1 region of the rat hippocampus.

5-Aminoimidazole-4-carboxamide riboside (AICA riboside; Acadesine) activates AMP-activated protein kinase (AMPK) in intact cells, and is reported to exert protective effects in the mammalian CNS. In rat cerebrocortical brain slices, AMPK was activated by metabolic stress (ischaemia > hypoxia > aglycaemia) and AICA riboside (0.1-10 mm). Activation of AMPK by AICA riboside was greatly attenuated by inhibitors of equilibrative nucleoside transport. AICA riboside also depressed excitatory synaptic transmission in area CA1 of the rat hippocampus, which was prevented by an adenosine A1 receptor antagonist and reversed by application of adenosine deaminase. However, AICA riboside was neither a substrate for adenosine deaminase nor an agonist at adenosine receptors. We conclude that metabolic stress and AICA riboside both stimulate AMPK activity in mammalian brain, but that AICA riboside has an additional effect, i.e. competition with adenosine for uptake by the nucleoside transporter. This results in an increase in extracellular adenosine and subsequent activation of adenosine receptors. Neuroprotection by AICA riboside could be mediated by this mechanism as well as, or instead of, by AMPK activation. Caution should therefore be exercised in ascribing an effect of AICA riboside to AMPK activation, especially in systems where inhibition of adenosine re-uptake has physiological consequences.

AMP-activated protein kinase: possible target for treatment of type 2 diabetes.

A considerable amount of data have accumulated showing that contraction of muscle has an acute insulin-like effect, triggering the uptake of glucose. Chronic muscle contraction, as seen in endurance training has effects on insulin sensitivity, enhancing the effect of insulin on glucose uptake. Endurance training results in an increase in levels of GLUT4 in the muscle. This increase in GLUT4 is thought to be responsible in part for the enhancement of insulin sensitivity. Recent experiments have demonstrated that acute and chronic effects of muscle contraction on glucose uptake and the increase in GLUT4 may be due to activation of a protein kinase, AMP-activated protein kinase (AMPK). This kinase is activated by the increase in 5'-AMP and the decline in creatine phosphate that occur during muscle contraction. Phosphorylated AMPK then presumably phosphorylates undefined target proteins, which in turn increase glucose uptake and transcription of the GLUT4 gene. Experiments have demonstrated that this kinase, normally activated during exercise, can be activated artificially in muscle by injecting non-exercising rats with 5-aminoimidazole-4-carboxamide-riboside (AICAR), an adenosine analog. AICAR is taken up into muscle and phosphorylated to form an analog of 5'-AMP. Acute (stimulation of glucose uptake into muscle) and chronic (increase in GLUT4) effects of exercise can be reproduced by injection of this drug. These observations open the door to the possibility of treatment of patients with type 2 diabetes with AMPK activators.

Absorption, metabolism, and excretion of 14C-temozolomide following oral administration to patients with advanced cancer.

The purpose of this study is to characterize the absorption, metabolism, and excretion of carbon 14-labeled temozolomide (14C-TMZ) administered p.o. to adult patients with advanced solid malignancies. On day 1 of cycle 1, six patients received a single oral 200-mg dose of 14C-TMZ (70.2 microCi). Whole blood, plasma, urine, and feces were collected from days 1-8 and on day 14 of cycle 1. Total radioactivity was measured in all samples. TMZ, 5-(3-methyltriazen-1-yl)imidazole-4-carboxamide (MTIC), and 4-amino-5-imidazole-carboxamide (AIC) concentrations were determined in plasma, and urine and plasma samples were profiled for metabolite/degradation products. Maximum TMZ plasma concentrations were achieved between 0.33 to 2 h (mean, 1.2 h), and half-life, apparent volume of distribution, and oral clearance values averaged 1.9 h, 17 liters/m2, and 104 ml/min/m2, respectively. A first-order absorption, one-compartment linear model, which included first-order formation of MTIC from TMZ and elimination of MTIC via degradation to AIC, and a peripheral distribution compartment for AIC, adequately described the plasma TMZ, MTIC, and AIC concentrations. MTIC systemic clearance was estimated to be 5384 ml/min/m2, and the half-life was calculated to be 2.5 min. Metabolite profiles of plasma at 1 and 4 h after treatment showed that 14C-derived radioactivity was primarily associated with TMZ, and a smaller amount was attributed to AIC. Profiles of urine samples from 0-24 h revealed that 14C-TMZ-derived urinary radioactivity was primarily associated with unchanged drug (5.6%), AIC (12%), or 3-methyl-2,3-dihydro-4-oxoimidazo[5,1-d]tetrazine-8-carboxyl ic acid (2.3%). The recovered radioactive dose (39%) was principally eliminated in the urine (38%), and a small amount (0.8%) was excreted in the feces. TMZ exhibits rapid oral absorption and high systemic availability. The primary elimination pathway for TMZ is by pH-dependent degradation to MTIC and further degradation to AIC. Incomplete recovery of radioactivity may be explained by the incorporation of AIC into nucleic acids.