Two drug interaction studies evaluating the pharmacokinetics and toxicity of pemetrexed when coadministered with aspirin or Ibuprofen in patients with advanced cancer.

PURPOSE: Pemetrexed is an antimetabolite that is structurally similar to methotrexate. Because nonsteroidal anti-inflammatory drugs (NSAID) impair methotrexate clearance and increase its toxicity, we evaluated the pharmacokinetics and toxicity of pemetrexed when coadministered with aspirin or ibuprofen in advanced cancer patients. EXPERIMENTAL DESIGN: In two independent, randomized, crossover drug interaction studies, cancer patients with a creatinine clearance (CrCl) > or =60 mL/min received an NSAID (aspirin or ibuprofen) with either the first or the second dose of pemetrexed (cycle 1 or 2). Pemetrexed (500 mg/m(2)) was infused i.v. on day 1 of a 21-day cycle, and all patients were supplemented with oral folic acid and i.m. vitamin B(12). Aspirin (325 mg) or ibuprofen (400 mg; 2 x 200 mg) was given orally every 6 hours, starting 2 days before pemetrexed administration, with the ninth and final dose taken 1 hour before infusion. Pemetrexed pharmacokinetics with and without concomitant NSAID treatment were compared for cycles 1 and 2. RESULTS: Data from 27 patients in each study were evaluable for the analysis of pemetrexed pharmacokinetics. Coadministration of aspirin did not alter pemetrexed pharmacokinetics; however, ibuprofen coadministration was associated with a 16% reduction in clearance, a 15% increase in maximum plasma concentration, and a 20% increase in area under the plasma concentration versus time curve but no significant change in V(ss) compared with pemetrexed alone. No febrile neutropenia occurred in any patient, and no increase in pemetrexed-related toxicity was associated with NSAID administration. CONCLUSIONS: Pemetrexed (500 mg/m(2)) with vitamin supplementation is well tolerated and requires no dosage adjustment when coadministered with aspirin (in patients with CrCl > or =60 mL/min) or ibuprofen (in patients with CrCl > or =80 mL/min).

Use of microdosing to predict pharmacokinetics at the therapeutic dose: experience with 5 drugs.

OBJECTIVES: A volunteer trial was performed to compare the pharmacokinetics of 5 drugs--warfarin, ZK253 (Schering), diazepam, midazolam, and erythromycin--when administered at a microdose or pharmacologic dose. Each compound was chosen to represent a situation in which prediction of pharmacokinetics from either animal or in vitro studies (or both) was or is likely to be problematic. METHODS: In a crossover design volunteers received (1) 1 of the 5 compounds as a microdose labeled with radioactive carbon (carbon 14) (100 microg), (2) the corresponding (14)C-labeled therapeutic dose on a separate occasion, and (3) simultaneous administration of an intravenous (14)C-labeled microdose and an oral therapeutic dose for ZK253, midazolam, and erythromycin. Analysis of (14)C-labeled drugs in plasma was done by use of HPLC followed by accelerator mass spectrometry. Liquid chromatography-tandem mass spectrometry was used to measure plasma concentrations of ZK253, midazolam, and erythromycin at therapeutic concentrations, whereas HPLC-accelerator mass spectrometry was used to measure warfarin and diazepam concentrations. RESULTS: Good concordance between microdose and therapeutic dose pharmacokinetics was observed for diazepam (half-life [t((1/2))] of 45.1 hours, clearance [CL] of 1.38 L/h, and volume of distribution [V] of 90.1 L for 100 microg and t((1/2)) of 35.7 hours, CL of 1.3 L/h, and V of 123 L for 10 mg), midazolam (t((1/2)) of 4.87 hours, CL of 21.2 L/h, V of 145 L, and oral bioavailability [F] of 0.23 for 100 microg and t((1/2)) of 3.31 hours, CL of 20.4 L/h, V of 75 L, and F of 0.22 for 7.5 mg), and development compound ZK253 (F = <1% for both 100 microg and 50 mg). For warfarin, clearance was reasonably well predicted (0.17 L/h for 100 microg and 0.26 L/h for 5 mg), but the discrepancy observed in distribution (67 L for 100 microg and 17.9 L for 5 mg) was probably a result of high-affinity, low-capacity tissue binding. The oral microdose of erythromycin failed to provide detectable plasma levels as a result of possible acid lability in the stomach. Absolute bioavailability for the 3 compounds examined yielded excellent concordance with data from the literature or data generated in house. CONCLUSION: Overall, when used appropriately, microdosing offers the potential to aid in early drug candidate selection.

A review of nanoelectrospray ionization applications for drug metabolism and pharmacokinetics.

Although traditionally reserved for proteomic analysis, nanoESI has found increased use for small molecule applications related to drug metabolism/pharmacokinetics (DMPK). NanoESI, which refers to ESI performed at flow rates in the range of 200 to 1000 nL/min using smaller diameter emitters (10 to 100 microm id), produces smaller droplets than conventional ESI resulting in more efficient ionization. Benefits include greater sensitivity, enhanced dynamic range, and a reduced competition for ionization. These advantages may now be harnessed largely due to the introduction of a commercial system for automated nanoESI infusion. This development in turn has allowed ADME (absorption, distribution, metabolism, and excretion) scientists to consider novel approaches to mass spectrometric analysis without direct LC interfacing. While it is freely acknowledged that nanoESI infusion is not likely to supplant LC-MS as the primary analytical platform for ADME, nanoESI infusion has been successfully applied to both quantitative (bioanalysis) and qualitative (metabolite identification) applications. This review summarizes published applications of this technology and offers a perspective on where it fits best into the DMPK laboratory.

Population pharmacokinetic analysis of ten phase II clinical trials of pemetrexed in cancer patients.

PURPOSE: The objectives of these population pharmacokinetic analyses were to (1) assess the overall disposition of pemetrexed, (2) characterize between-patient and within-patient variability and identify influential covariates with respect to pemetrexed pharmacokinetics; and, (3) provide individual empirical Bayesian estimates of pharmacokinetic parameters for use in a subsequent pharmacokinetic/pharmacodynamic evaluation of neutropenia following pemetrexed administration. PATIENTS AND METHODS: Data from 287 patients who received 441 cycles without folic acid or vitamin B12 supplementation during participation in one of ten phase II cancer trials were evaluated by population pharmacokinetic analysis using NONMEM. Starting doses were 500 or 600 mg pemetrexed per m2 body surface area, administered as 10-min intravenous infusions every 21 days (1 cycle). The model was developed using data from eight of the ten studies. Predictive performance was evaluated using data from the other two studies. RESULTS: The population pharmacokinetics of pemetrexed administered as a 10-min intravenous infusion are well characterized by a two-compartment model. Typical values of total systemic clearance, central volume of distribution, distributional clearance, and peripheral volume of distribution were 91.6 ml/min, 12.9 l, 14.4 ml/min, and 3.38 l, respectively. Based on these parameter estimates, the terminal elimination half-life of pemetrexed was approximately 3.5 h. Renal function was identified as a covariate with respect to total systemic clearance, and body surface area as a covariate with respect to the central volume of distribution. CONCLUSION: Total systemic exposure (AUC) for a given dose of pemetrexed increases as renal function decreases. Since pharmacodynamic analyses have shown that AUC and not C (max) is the primary determinant of neutropenic response to pemetrexed, this suggests that dose adjustments based on renal function, rather than body surface area, might be considered for pemetrexed.

Phase I study of the multidrug resistance inhibitor zosuquidar administered in combination with vinorelbine in patients with advanced solid tumours.

BACKGROUND: Zosuquidar (LY335979) is an oral P-glycoprotein modulator. This phase I study was designed to determine the maximum tolerated dose (MTD) of zosuquidar in combination with vinorelbine. The effects of zosuquidar on vinorelbine pharmacokinetics were also examined. DESIGN: Patients with advanced solid tumours were treated with escalating doses of zosuquidar administered every 8-12 h on days 7-9 and 14-16 during cycle 1 then days 0-2, 7-9, and 14-16 from cycle 2 onwards, with vinorelbine 22.5-30 mg/m2 IV on days 1, 8 and 15 every 28 days. RESULTS: Of 21 patients registered, 19 were treated at four dose levels (zosuquidar 100-300 mg/m2). Two patients had prolonged and febrile neutropenia at the second dose level resulting in a reduction of the dose of vinorelbine in subsequent dose levels. There was another patient with dose-limiting febrile neutropenia at dose level four which resulted in the expansion of the dose level three. Eight patients had stable disease and no objective responses were seen. Vinorelbine pharmacokinetic studies showed reduced clearance when given with zosuquidar. CONCLUSIONS: The MTD was zosuquidar 300 mg/m2 orally every 12 h for 3 days weekly for 3 weeks with vinorelbine 22.5 mg/m2 IV weekly for 3 weeks every 28 days. Zosuquidar may inhibit vinorelbine clearance to a modest degree.

A Phase I trial of a potent P-glycoprotein inhibitor, zosuquidar trihydrochloride (LY335979), administered intravenously in combination with doxorubicin in patients with advanced malignancy.

PURPOSE: Our intention was to (a) to investigate the safety and tolerability of a potent P-glycoprotein modulator, zosuquidar trihydrochloride (LY335979), when administered i.v. alone or in combination with doxorubicin, (b) to determine the pharmacokinetics of zosuquidar and correlate exposure to inhibition of P-glycoprotein function in a surrogate assay, and (c) to compare the pharmacokinetics of doxorubicin in the presence and absence of zosuquidar. PATIENTS AND METHODS: Patients with advanced malignancies who provided written informed consent received zosuquidar and doxorubicin administered separately during the first cycle of therapy and then concurrently in subsequent cycles. Zosuquidar was given i.v. over 48 h in a cohort-dose escalation manner until the occurrence of dose-limiting toxicity or protocol specified maximum exposure. Doxorubicin doses of 45, 60, 75 mg/m(2) were administered during the course of the trial. RESULTS: Dose escalation proceeded through 9 cohorts with a total of 40 patients. The maximal doses administered were 640 mg/m(2) of zosuquidar and 75 mg/m(2) of doxorubicin. No dose-limiting toxicity of zosuquidar was observed. Pharmacokinetic analysis revealed that, in the presence of zosuquidar at doses that exceeded 500 mg, there was a modest decrease in clearance (17-22%) and modest increase in area under the curve (15-25%) of doxorubicin. This change was associated with an enhanced leukopenia and thrombocytopenia but was without demonstrable clinical significance. The higher doses of zosuquidar were associated with maximal P-glycoprotein inhibition in natural killer cells. CONCLUSION: Zosuquidar can be safely coadministered with doxorubicin using a 48 h i.v. dosing schedule.

A phase I trial of a potent P-glycoprotein inhibitor, Zosuquidar.3HCl trihydrochloride (LY335979), administered orally in combination with doxorubicin in patients with advanced malignancies.

PURPOSE: The purpose of this study was to investigate the safety and tolerability of Zosuquidar.3HCl, a potent inhibitor of P-glycoprotein (Pgp), when administered p.o. alone and in combination with doxorubicin and to determine whether Zosuquidar.3HCl affects doxorubicin pharmacokinetics and inhibits Pgp function in peripheral blood natural killer lymphocytes. EXPERIMENTAL DESIGN: Patients with advanced nonhematological malignancies were eligible for this Phase I trial. Zosuquidar.3HCl and doxorubicin were administered separately during the first cycle of therapy and then administered concurrently. Zosuquidar.3HCl was administered over 4 days, with doses escalated until the occurrence of dose-limiting toxicity. Subsequently, doxorubicin doses were increased from 45 to 75 mg/m(2). Zosuquidar.3HCl, doxorubicin, and doxorubicinol pharmacokinetics were analyzed, and dual fluorescence cytometry was used to determine the effects of Zosuquidar.3HCl on Pgp function in natural killer cells. RESULTS: A total of 38 patients were treated at nine dose levels. Neurotoxicity was dose-limiting for oral Zosuquidar.3HCl, characterized by cerebellar dysfunction, hallucinations, and palinopsia. The maximum-tolerated dose for oral Zosuquidar.3HCl administered every 12 h for 4 days is 300 mg/m(2). Zosuquidar.3HCl did not affect doxorubicin myelosuppression or pharmacokinetics, and Zosuquidar.3HCl pharmacokinetics were similar in the absence and presence of doxorubicin. Higher plasma concentrations of Zosuquidar.3HCl were associated with greater Pgp inhibition in natural killer cells. CONCLUSION: Zosuquidar.3HCl can be coadministered with doxorubicin using a 4-day oral dosing schedule, with little effect on doxorubicin toxicity or pharmacokinetics. Further refinement in Zosuquidar.3HCl dosing and scheduling should be explored to optimize Pgp inhibition while minimizing cerebellar toxicity.

Repeat analysis and incurred sample reanalysis: recommendation for best practices and harmonization from the global bioanalysis consortium harmonization team.

The A7 harmonization team (A7 HT), a part of the Global Bioanalysis Consortium (GBC), focused on reviewing best practices for repeat analysis and incurred sample reanalysis (ISR) as applied during regulated bioanalysis. With international representation from Europe, Latin America, North America, and the Asia Pacific region, the team first collated common practices and guidance recommendations and assessed their suitability from both a scientific and logistical perspective. Subsequently, team members developed best practice recommendations and refined them through discussions and presentations with industry experts at scientific meetings. This review summarizes the team findings and best practice recommendations. The few topics where no consensus could be reached are also discussed. The A7 HT recommendations, together with those from the other GBC teams, provide the basis for future international harmonization of regulated bioanalytical practices.

Dried blood spot sampling: coupling bioanalytical feasibility, blood-plasma partitioning and transferability to in vivo preclinical studies.

BACKGROUND: The adoption of dried blood spot (DBS) sampling and analysis to support drug discovery and development requires the understanding of its bioanalytical feasibility as well as the distribution of the analyte in blood. RESULTS: Demonstrated the feasibility of adopting DBS for four test analytes representing diverse physico-chemical as well as pharmacokinetic parameters. The key findings include the use of a single extraction procedure across all four analytes, assay range of 1 to 5000 ng/ml, stability in whole blood as well as on-card, and the non-impact of blood volume. In vivo data were used to calculate the blood-to-plasma ratio (using both AUC and average of individual time points), which was then used to predict plasma concentration from DBS data. The predicted data showed an excellent correlation with actual plasma data. CONCLUSION: Transition from plasma to DBS can be supported for preclinical studies by conducting a few well-defined bioanalytical experiments followed by an in vivo bridging study. Blood:plasma ratio derived from the bridging study can be used to predict plasma concentrations from DBS data.

Validation of 96-well equilibrium dialysis with non-radiolabeled drug for definitive measurement of protein binding and application to clinical development of highly-bound drugs.

Definitive plasma protein binding (PB) studies in drug development are routinely conducted with radiolabeled material, where the radiochemical purity limits quantitative PB measurement. Recent and emerging regulatory guidances increasingly expect quantitative determination of the fraction unbound (Fu) for key decision making. In the present study, PB of 11 structurally- and therapeutically-diverse drugs spanning the full range of plasma binding was determined by equilibrium dialysis of non-radiolabeled compound and was validated against the respective definitive values obtained by accepted radiolabeled protocols. The extent of plasma binding was in agreement with the radiolabeled studies; however, the methodology reported herein enables reliable quantification of Fu values for highly-bound drugs and is not limited by the radiochemical purity. In order to meet the rigor of a development study, equilibrium dialysis of unlabeled drug must be supported by an appropriately validated bioanalytical method along with studies to determine compound solubility and stability in matrix and dialysis buffer, nonspecific binding to the dialysis device, and ability to achieve equilibrium in the absence of protein. The presented methodology establishes an experimental protocol for definitive PB measurement, which enables quantitative determination of low Fu values, necessary for navigation of new regulatory guidances in clinical drug development.

Conference report: Inaugural Applied Pharmaceutical Analysis: India 2010 conference.

The inaugural Applied Pharmaceutical Analysis-India (APA-India) conference was held between 21 and 24 February 2010 in Hyderabad, India. The theme of the 2010 APA-India meeting was "The best of bioanalytical science in India: the role of bioanalysis and absorption, distribution, metabolism and excretion in translational medicine". The conference brought together scientists from across India and the rest of the world to stimulate discussion in the areas of discovery bioanalysis, new technologies, regulated bioanalysis and biotransformation, as applied to pharmaceutical analysis in India, the USA and other parts of the world. A total of 37 podium presentations and three webinars were presented at the 2010 APA-India meeting. The analytical tool of focus was MS with an emphasis on application to the Department of Drug Metabolism and Pharmacokinetics studies in a globalized pharmaceutical industry.

Workshop report and follow-up--AAPS Workshop on current topics in GLP bioanalysis: Assay reproducibility for incurred samples--implications of Crystal City recommendations.

The Conference Report of the 3rd AAPS/FDA Bioanalytical Workshop (Crystal City III) endorsed the concept that assay methods supporting bioanalytical data in submissions must demonstrate assay reproducibility by using incurred samples. The present Workshop was convened to provide a forum for discussion and consensus building about incurred sample assay reproducibility for both nonclinical and clinical studies. Information about current regulatory perspectives on incurred sample reanalysis (ISR) was presented, implications of ISR for both large and small molecules were discussed, and the steering committee put forth recommendations for performing ISR. These recommendations from the Workshop, along with the subsequent evolution of approaches leading to a robust ISR program, may be used by scientists performing bioanalytical assays for regulated studies to provide additional confirmation of assay reproducibility for incurred samples.

Current applications of liquid chromatography/mass spectrometry in pharmaceutical discovery after a decade of innovation.

Current drug discovery involves a highly iterative process pertaining to three core disciplines: biology, chemistry, and drug disposition. For most pharmaceutical companies the path to a drug candidate comprises similar stages: target identification, biological screening, lead generation, lead optimization, and candidate selection. Over the past decade, the overall efficiency of drug discovery has been greatly improved by a single instrumental technique, liquid chromatography/mass spectrometry (LC/MS). Transformed by the commercial introduction of the atmospheric pressure ionization interface in the mid-1990s, LC/MS has expanded into almost every area of drug discovery. In many cases, drug discovery workflow has been changed owing to vastly improved efficiency. This review examines recent trends for these three core disciplines and presents seminal examples where LC/MS has altered the current approach to drug discovery.

Phase I and pharmacokinetic study of pemetrexed administered every 3 weeks to advanced cancer patients with normal and impaired renal function.

PURPOSE: This phase I study was conducted to determine the toxicities, pharmacokinetics, and recommended doses of pemetrexed in cancer patients with normal and impaired renal function. PATIENTS AND METHODS: Patients received a 10-minute infusion of 150 to 600 mg/m2 of pemetrexed every 3 weeks. Patients were stratified for independent dose escalation by measured glomerular filtration rate (GFR) into four cohorts ranging from > or = 80 to less than 20 mL/min. Pemetrexed plasma and urine pharmacokinetics were evaluated for the first cycle. Patients enrolled after December 1999 were supplemented with oral folic acid and intramuscular vitamin B12. RESULTS: Forty-seven patients were treated with 167 cycles of pemetrexed. Hematologic dose-limiting toxicities occurred in vitamin-supplemented patients (two; 15%) and non-supplemented patients (six; 18%), and included febrile neutropenia (four patients) and grade 4 thrombocytopenia (two patients). Nonhematologic toxicities included fatigue, diarrhea, and nausea, and did not correlate with renal function. Accrual was discontinued in patients with GFR less than 30 mL/min after one patient with a GFR of 19 mL/min died as a result of treatment-related toxicities. Pemetrexed plasma clearance positively correlated with GFR (r2 = 0.736), resulting in increased drug exposures in patients with impaired renal function. With vitamin supplementation, pemetrexed 600 mg/m2 was tolerated by patients with a GFR > or = 80 mL/min, whereas patients with a GFR of 40 to 79 mL/min tolerated a dose of 500 mg/m2. CONCLUSION: Pemetrexed was well tolerated at doses of 500 mg/m2 with vitamin supplementation in patients with GFR > or = 40 mL/min. Additional studies are needed to define appropriate dosing for renally impaired patients receiving higher dose pemetrexed with vitamin supplementation.

Validating regulatory-compliant wide dynamic range bioanalytical assays using chip-based nanoelectrospray tandem mass spectrometry.

Automated chip-based infusion nanoelectrospray ionization coupled to tandem mass spectrometry (nanoESI-MS/MS) was used to validate a bioanalytical assay conforming to United States Food and Drug Administration (FDA) regulatory guidelines and Good Laboratory Practices (GLP). Reboxetine was used as the analyte fortified in dog plasma along with an analog internal standard (IS). The best nanoESI response for reboxetine was observed with 90% acetonitrile (ACN)/water without any mobile phase modifiers. The analyte and IS were extracted from dog plasma samples by liquid-liquid extraction (LLE). The supernatant was concentrated to dryness and redissolved in 90% ACN/water for nanoESI. Selected reaction monitoring (SRM) data were collected for all samples to generate ion current profiles with a base width of approximately 20 s. Selectivity experiments showed no interferences in blank plasma samples. Interferences as a result of in-source collision-induced dissociation of metabolites were not an issue due to the previously documented metabolism of reboxetine. Matrix suppression was evaluated across multiple lots of dog plasma as well as over different animal species (rabbit, rat, mouse) and different anticoagulants (heparin, EDTA). Matrix suppression ranged from approximately 30-60% across the different lots, species etc.; however, in all instances, the analyte and the IS were suppressed by similar amounts, suggesting the similarity in ionization properties between the two. A three-batch validation was performed (each batch consisting of four different concentrations, six replicates of each concentration) and demonstrated inter-assay accuracy (% relative error; RE) of less than +/-8% and an inter-assay precision (% relative standard deviation; RSD) of less than 7%, thus meeting regulatory guidelines. A comparison of analyses by nanoESI-MS/MS and liquid chromatography coupled to tandem mass spectrometry (LC/MS/MS) showed that nanoESI-MS/MS had a greater slope for the calibration standard curve compared to LC/MS/MS, indicating greater sensitivity for the former technique. It is also noteworthy that the amount of sample infused during nanoESI-MS/MS was approximately 80-fold less compared to the amount of sample injected during LC/MS/MS. The absence of carryover (attributed to the lack of a common fluid path) in the nanoESI technique enabled the extension of the assay linear dynamic range to 500,000-fold, and the possibility of analyzing samples in a single batch without the need for re-analysis of samples with high concentrations. This technology offers the possibility for increased throughput for studies supporting drug development by providing fast data turnaround for assays conforming to regulatory guidelines and GLPs.