Correction to: Phase I-II trial of imatinib mesylate (Gleevec; STI571) in treatment of recurrent oligodendroglioma and mixed oligoastrocytoma. North central cancer treatment group study N0272 (ALLIANCE/NCCTG).

The last author's first name was truncated in the initial online publication. The original article has been corrected.

Phase I-II trial of imatinib mesylate (Gleevec; STI571) in treatment of recurrent oligodendroglioma and mixed oligoastrocytoma. North central cancer treatment group study N0272 (ALLIANCE/NCCTG).

PURPOSE: To evaluate the pharmacokinetics and efficacy of imatinib in patients with recurrent oligodendroglial tumors. METHODS: Patients with progressive WHO grade II-III recurrent tumors after prior RT and chemotherapy were eligible. A phase I dose-escalation study was conducted for patients on enzyme-inducing anticonvulsants (EIAC). A phase II study for non-EIAC patients utilized a fixed dose of 600 mg/D. Primary efficacy endpoint was 6-month progression-free survival (PFS6). A 2-stage design was utilized, with 90% power to detect PFS6 increase from 25 to 45%. RESULTS: In the Phase I, maximum tolerated dose was not reached at 1200 mg/D. For phase II patients, overall PFS6 was 33% and median PFS 4.0 months (95% CI 2.1, 5.7). Median overall survival (OS) was longer in imatinib-treated patients compared with controls (16.6 vs. 8.0 months; HR = 0.64, 95% CI 0.41,1.0, p = 0.049), and longer in patients with 1p/19q-codeleted tumors (19.2 vs. 6.2 months, HR = 0.43, 95% CI 0.21,0.89, p = 0.019). Confirmed response rate was 3.9% (PR = 1; REGR = 1), with stable disease observed in 52.9%. At 600 mg/D, mean steady-state imatinib plasma concentration was 2513 ng/ml (95% CI 1831,3195). Grade 3-4 adverse events (hematologic, fatigue, GI, hypophosphatemia, or hemorrhage) occurred in 61%. CONCLUSIONS: Although adequate plasma levels were achieved, the observed PFS6 of 33% did not reach our pre-defined threshold for success. Although OS was longer in imatinib-treated patients than controls, this finding would require forward validation in a larger cohort. Imatinib might show greater activity in a population enriched for PDGF-dependent pathway activation in tumor tissue.

The relationship of polymorphisms in ABCC2 and SLCO1B3 with docetaxel pharmacokinetics and neutropenia: CALGB 60805 (Alliance).

Docetaxel-related neutropenia was associated with polymorphisms in the drug transporters ABCC2 and SLCO1B3 in Japanese cancer patients. We hypothesized that this association is because of reduced docetaxel clearance, associated with polymorphisms in those genes. We studied 64 US cancer patients who received a single cycle of 75 mg/m of docetaxel monotherapy. We found that the ABCC2 polymorphism at rs-12762549 trended to show a relationship with reduced docetaxel clearance (P=0.048), but not with neutropenia. There was no significant association of the SLCO1B3 polymorphisms with docetaxel clearance or neutropenia. We conclude that the relationship between docetaxel-associated neutropenia and polymorphisms in drug transporters identified in Japanese patients was not confirmed in this cohort of US cancer patients.

A Phase I Trial of the ABCB1 Inhibitor, Oral Valspodar, in Combination With Paclitaxel in Patients With Advanced Solid Tumors.

OBJECTIVES: Multidrug resistance mediated by P-glycoprotein is a potential obstacle to cancer treatment. This phase 1 trial determined the safety of paclitaxel with valspodar, a P-glycoprotein inhibitor, in patients with advanced solid tumors. METHODS: Patients were treated with single-agent paclitaxel Q3W 175 mg/m 2 (or 135 mg/m 2 if heavily pretreated) as a 3-hour infusion. If their disease was stable (SD) or progressive (PD), paclitaxel at 30% (52.5 mg/m 2 ), 40% (70 mg/m 2 ), or 50% (87.5 mg/m 2 ) of 175 mg/m 2 (full dose) was administered with valspodar 5 mg/kg orally 4 times daily for 12 doses. Pharmacokinetic sampling (PK) for paclitaxel and valspodar was performed during single-agent and combination therapy. RESULTS: Sixteen patients had SD/PD after one cycle of paclitaxel and then received paclitaxel at 30% (n=3), 40% (n=3), and 50% (n=10) with valspodar. Hematologic adverse events (AEs) including myelosuppression at paclitaxel 40% were comparable to those of full-dose paclitaxel. Non-hematologic AEs consisted of reversible hepatic (hyperbilirubinemia and transaminitis) and neurologic AEs (ataxia and paresthesias). Eleven patients experienced SD with a median of 12.7 weeks (range, 5.4 to 36.0), 4 patients progressed, and 1 was inevaluable. Reduced dose paclitaxel with valspodar resulted in lower plasma peak concentrations of paclitaxel; otherwise, concentrations were similar to single-agent paclitaxel. CONCLUSION: Paclitaxel at 70 mg/m 2 was administered safely with valspodar. Limited efficacy in hematologic and solid tumors resulted in discontinuation of its clinical development and other transporter inhibitors. Recently, the development of ATP-binding cassette transporter inhibitors has been reconsidered to mitigate resistance to antibody-drug conjugates.

Renal dysfunction in a renal transplant patient treated concurrently with cyclosporine and imatinib.

Imatinib mesylate has proven activity in treating locally advanced or metastatic gastrointestinal stromal tumors (GIST). Drug interactions are particularly concerning as imatinib is extensively metabolized by the cytochrome P450 enzyme system. We describe the clinical course of a 72 year-old male with a cadaveric renal transplant requiring cyclosporine that presented with a metastatic GIST and was started on imatinib at the standard dose of 400 mg daily. Imatinib initiation resulted in a decline in renal function with the serum creatinine increasing from 123 µmol/L to 196 µmol/L and an elevation in whole blood cyclosporine concentrations from 79 µg/L to 139 µg/L. No other imatinib toxicities were reported. With discontinuation of imatinib, the serum creatinine returned to baseline as did the whole blood cyclosporine levels. Ultimately, decreasing both the cyclosporine and imatinib dosing was associated with stabilized renal function (serum creatinine 150-186 µmol/L) and cyclosporine concentrations (53-97 µg/L). A prolonged partial response to therapy for 19 months was maintained despite low imatinib trough concentrations measured on two separate occasions (127.1 ng/ml and 139 ng/ml). In our patient, imatinib initiation resulted in renal toxicity most likely due to its interaction with cyclosporine resulting in elevation of the whole blood cyclosporine concentration.

Phase I study of vorinostat (suberoylanilide hydroxamic acid, NSC 701852) in combination with docetaxel in patients with advanced and relapsed solid malignancies.

INTRODUCTION: Vorinostat is an inhibitor of histone deacetylase 6, which acetylates tubulin and stabilizes microtubules. Since taxanes also stabilize microtubules, we hypothesized that the administration of vorinostat followed by docetaxel should result in synergistic cytotoxicity. We conducted a phase I trial to determine the dose level of vorinostat plus docetaxel that would result in dose-limiting toxicity (DLT) in ≤30% of patients. METHODS: Eligible patients had castration-resistant prostate cancer (CRPC) or relapsed urothelial or non-small-cell lung cancer (NSCLC) after ≥1 prior chemotherapy regimen not containing docetaxel, performance status of 0-2, and adequate organ function. Vorinostat was given orally for 14 days beginning on day 1 of a 21-day cycle, with docetaxel given intravenously over 1 h on day 4. The time-to-event continuous reassessment method (TITE-CRM) guided dose escalation. Dose levels (DL) -1, 0, 1 and 2 corresponded to vorinostat 100, 100, 200 and 200 mg plus docetaxel 50, 60, 60, and 75 mg/m(2), respectively. Pharmacokinetic studies were performed on days 1 and 4 of cycle 1. RESULTS: Twelve patients were enrolled: median age 65 years (range 49-74); 9 male, 3 female; 4 CRPC, 5 urothelial, 3 NSCLC. The median number of cycles administered was 2. Two patients were treated at DL -1, 4 at DL 0, 5 at DL 1 and 1 at DL 2. Five DLTs occurred in 5 patients: neutropenic fever/sepsis (2), anaphylactic reaction (1), myocardial infarction (1) and gastrointestinal bleed (1). Other toxicities included grade 3/4 neutropenia (4), peripheral neuropathy (1), and gastrointestinal bleed (n = 1). The estimated probability of DLT for DL -1 was 0.32 (90% posterior probability interval [PI], 0.11 to 0.53) for DL 0, 0.38 (90% PI, 0.16 to 0.58) and for DL 1, 0.43 (90% PI, 0.23 to 0.64). The trial was stopped due to excessive toxicity. No responses were noted. CONCLUSIONS: The combination of vorinostat and docetaxel was poorly tolerated with excessive DLTs that required early study termination. No responses were identified. Vorinostat and docetaxel pharmacokinetics were comparable to previous reports in the literature, without obvious drug-drug interactions.

Application of a single-objective, hybrid genetic algorithm approach to pharmacokinetic model building.

A limitation in traditional stepwise population pharmacokinetic model building is the difficulty in handling interactions between model components. To address this issue, a method was previously introduced which couples NONMEM parameter estimation and model fitness evaluation to a single-objective, hybrid genetic algorithm for global optimization of the model structure. In this study, the generalizability of this approach for pharmacokinetic model building is evaluated by comparing (1) correct and spurious covariate relationships in a simulated dataset resulting from automated stepwise covariate modeling, Lasso methods, and single-objective hybrid genetic algorithm approaches to covariate identification and (2) information criteria values, model structures, convergence, and model parameter values resulting from manual stepwise versus single-objective, hybrid genetic algorithm approaches to model building for seven compounds. Both manual stepwise and single-objective, hybrid genetic algorithm approaches to model building were applied, blinded to the results of the other approach, for selection of the compartment structure as well as inclusion and model form of inter-individual and inter-occasion variability, residual error, and covariates from a common set of model options. For the simulated dataset, stepwise covariate modeling identified three of four true covariates and two spurious covariates; Lasso identified two of four true and 0 spurious covariates; and the single-objective, hybrid genetic algorithm identified three of four true covariates and one spurious covariate. For the clinical datasets, the Akaike information criterion was a median of 22.3 points lower (range of 470.5 point decrease to 0.1 point decrease) for the best single-objective hybrid genetic-algorithm candidate model versus the final manual stepwise model: the Akaike information criterion was lower by greater than 10 points for four compounds and differed by less than 10 points for three compounds. The root mean squared error and absolute mean prediction error of the best single-objective hybrid genetic algorithm candidates were a median of 0.2 points higher (range of 38.9 point decrease to 27.3 point increase) and 0.02 points lower (range of 0.98 point decrease to 0.74 point increase), respectively, than that of the final stepwise models. In addition, the best single-objective, hybrid genetic algorithm candidate models had successful convergence and covariance steps for each compound, used the same compartment structure as the manual stepwise approach for 6 of 7 (86 %) compounds, and identified 54 % (7 of 13) of covariates included by the manual stepwise approach and 16 covariate relationships not included by manual stepwise models. The model parameter values between the final manual stepwise and best single-objective, hybrid genetic algorithm models differed by a median of 26.7 % (q1 = 4.9 % and q3 = 57.1 %). Finally, the single-objective, hybrid genetic algorithm approach was able to identify models capable of estimating absorption rate parameters for four compounds that the manual stepwise approach did not identify. The single-objective, hybrid genetic algorithm represents a general pharmacokinetic model building methodology whose ability to rapidly search the feasible solution space leads to nearly equivalent or superior model fits to pharmacokinetic data.

Will imatinib compromise reproductive capacity?

Imatinib mesylate is the first in a family of highly effective, minimally toxic, targeted agents used widely to treat Philadelphia-positive leukemias and selected other cancers, leading to a steady rise in the prevalence of patients using such therapy. Because failure of therapy would require conventional gonadotoxic chemotherapeutics, many female patients using imatinib may choose to preserve fertility. Herein, we provide evidence of a potential negative effect of imatinib on ovarian function by reporting the first case of a woman who showed a severely compromised ovarian response to gonadotropin stimulation while on imatinib, with a normal ovarian response after stopping this medication.

A phase I study of the vitamin D3 analogue ILX23-7553 administered orally to patients with advanced solid tumors.

PURPOSE: ILX23-7553 (1,25-dihydroxy-16-ene-23-yne vitamin D3) is a vitamin D analogue that was developed to avoid the hypercalcemia that may limit the use of vitamin D as an anti-cancer agent. We performed a phase I study of ILX23-7553 to determine its side-effect profile, pharmacokinetics, and to document any observed antitumor activity. PATIENTS AND METHODS: Adult patients with refractory solid tumors were enrolled. A modified Fibonacci dose escalation scheme was employed. ILX23-7553 was administered orally daily for three consecutive days, and repeated in 7-day cycles. Plasma drug concentrations were assayed by radioimmunoassay and radioreceptor assay. RESULTS: Sixteen patients were enrolled to 10 dose levels ranging from 1.7 to 37.3 µg/m(2)/day. The maximum tested dose was six times higher than the maximally-tolerated dose (MTD) in dogs. Dose-limiting toxicity was not observed. ILX23-7553 concentrations on cycle 1 day 1 of treatment were comparable to concentrations on cycle 2 day 1, suggesting limited accumulation. One patient with adrenal cortical cancer had stable disease for 23 weeks, but no objective responses were observed. CONCLUSIONS: ILX23-7553 was well tolerated at the doses tested, with no evidence of hypercalcemia. The plasma concentrations achieved were approximately 100-fold lower than those associated with tumor growth inhibition in vitro, limiting use of this formulation.

A phase 1 study of BMS-275183, a novel oral analogue of paclitaxel given on a daily schedule to patients with advanced malignancies.

PURPOSE: BMS-275183 is an oral C-4 methyl carbonate analogue of paclitaxel that has the same mechanism of action, stabilization of tubulin polymerization. The present study was designed to: (i) assess the safety and tolerability of BMS-275183, and (ii) determine a suitable Phase II dose of BMS-275183 when given on a continuous daily schedule to patients with advanced solid tumor(s). METHODS: This was a multi-institutional, open-label, Phase I, single-arm dose escalation study in which cohorts of eligible patients with advanced malignancies were treated with BMS-275183 orally on a continuous daily schedule. The starting dose level was 6 mg/m(2)/day administered once daily. Cohorts of 3 patients were treated at each dose level provided no dose-limiting toxicities (DLTs) were observed. Each cycle of treatment lasted 28 days. RESULTS: Twenty patients were enrolled in dose cohorts ranging from the initial dose level of 6 mg/m(2)/day to 18 mg/m(2)/day. Overall, the most frequent (>20% of patients) treatment-related adverse events (AEs) were nausea (40%), constipation (20%), diarrhea (20%), and fatigue (20%). There were 2 fatal events of neutropenic sepsis one each at the 15 mg/m(2)/day and 18 mg/m(2)/day dose level, respectively. There were no objective responses; 4 of 20 patients experienced stable disease. Pharmacokinetic data indicated no clear correlation between dose and exposure following daily oral administration of BMS-275183 doses between 6 and 18 mg/m(2). Substantial inter-patient variability was observed, and high drug exposure was associated with fatal neutropenic sepsis. CONCLUSIONS: BMS-275183 is a novel oral analogue of paclitaxel with high inter-patient variability in exposure. The lack of evidence of clinical benefit and the occurrence of two fatal events of neutropenic sepsis, coupled with high drug exposure, argues against further evaluation of BMS-275183 on a daily dosing schedule.

A phase I study of vorinostat in combination with idarubicin in relapsed or refractory leukaemia.

Histone deacetylase inhibitors (HDACi) affect chromatin remodelling and modulate the expression of aberrantly silenced genes. HDACi have single-agent clinical activity in haematological malignancies and have synergistic anti-leukaemia activity when combined with anthracyclines in vitro. We conducted a two-arm, parallel Phase I trial to investigate two schedules of escalating doses of vorinostat (Schedule A: thrice daily (TID) for 14 d; B: TID for 3 d) in combination with a fixed dose of idarubicin in patients with refractory leukaemia. Of the 41 patients enrolled, 90% had acute myeloid leukaemia, with a median of 3 prior therapies. Seven responses (17%) were documented (two complete response (5%), one complete response without platelet recovery (2.5%), and four marrow responses). The 3-d schedule of vorinostat was better tolerated than the 14-d schedule. The maximum tolerated dose for vorinostat was defined as 400 mg TID for 3 d. The most common grade 3 and 4 toxicities included mucositis, fatigue and diarrhoea. Correlative studies demonstrated histone acetylation in patients on therapy and modulation of CDKN1A and TOP2A (topoisomerase II) gene expression. Pharmacokinetic analysis confirmed a dose-related elevation in plasma vorinostat concentrations. The combination of vorinostat and idarubicin is generally tolerable and active in patients with advanced leukaemia and should be studied in the front-line setting.

In vitro cytotoxicity and in vivo efficacy, pharmacokinetics, and metabolism of 10074-G5, a novel small-molecule inhibitor of c-Myc/Max dimerization.

The c-Myc oncoprotein is overexpressed in many tumors and is essential for maintaining the proliferation of transformed cells. To function as a transcription factor, c-Myc must dimerize with Max via the basic helix-loop-helix leucine zipper protein (bHLH-ZIP) domains in each protein. The small molecule 7-nitro-N-(2-phenylphenyl)-2,1,3-benzoxadiazol-4-amine (10074-G5) binds to and distorts the bHLH-ZIP domain of c-Myc, thereby inhibiting c-Myc/Max heterodimer formation and inhibiting its transcriptional activity. We report in vitro cytotoxicity and in vivo efficacy, pharmacodynamics, pharmacokinetics, and metabolism of 10074-G5 in human xenograft-bearing mice. In vitro, 10074-G5 inhibited the growth of Daudi Burkitt's lymphoma cells and disrupted c-Myc/Max dimerization. 10074-G5 had no effect on the growth of Daudi xenografts in C.B-17 SCID mice that were treated with 20 mg/kg 10074-G5 intravenously for 5 consecutive days. Inhibition of c-Myc/Max dimerization in Daudi xenografts was not seen 2 or 24 h after treatment. Concentrations of 10074-G5 in various matrices were determined by high-performance liquid chromatography-UV, and metabolites of 10074-G5 were identified by liquid chromatography/tandem mass spectrometry. The plasma half-life of 10074-G5 in mice treated with 20 mg/kg i.v. was 37 min, and peak plasma concentration was 58 µM, which was 10-fold higher than peak tumor concentration. The lack of antitumor activity probably was caused by the rapid metabolism of 10074-G5 to inactive metabolites, resulting in tumor concentrations of 10074-G5 insufficient to inhibit c-Myc/Max dimerization. Our identification of 10074-G5 metabolites in mice will help design new, more metabolically stable small-molecule inhibitors of c-Myc.

A phase I, pharmacokinetic and pharmacodynamic study on vorinostat in combination with 5-fluorouracil, leucovorin, and oxaliplatin in patients with refractory colorectal cancer.

PURPOSE: We conducted a phase I study to determine the maximum tolerated dose of vorinostat in combination with fixed doses of 5-fluorouracil (FU), leucovorin, and oxaliplatin (FOLFOX). EXPERIMENTAL DESIGN: Vorinostat was given orally twice daily for 1 week every 2 weeks. FOLFOX was given on days 4 and 5 of vorinostat. The vorinostat starting dose was 100 mg twice daily. Escalation occurred in cohorts of three to six patients. Pharmacokinetics of vorinostat, FU, and oxaliplatin were studied. RESULTS: Twenty-one patients were enrolled. Thrombocytopenia, neutropenia, gastrointestinal toxicities, and fatigue increased in frequency and severity at higher dose levels of vorinostat. Two of 4 evaluable patients at dose level 4 (vorinostat 400 mg orally twice daily) developed dose-limiting fatigue. One of 10 evaluable patients at dose level 3 (vorinostat 300 mg orally twice daily) had dose-limiting fatigue, anorexia, and dehydration. There were significant relationships between vorinostat dose and the area under the curve on days 1 and 5 (Pearson, < 0.001). The vorinostat area under the curve increased (P = 0.005) and clearance decreased (P = 0.003) on day 5 compared with day 1. The median C(max) of FU at each dose level increased significantly with increasing doses of vorinostat, suggesting a pharmacokinetic interaction between FU and vorinostat. Vorinostat-induced thymidylate synthase (TS) modulation was not consistent; only two of six patients had a decrease in intratumoral TS expression by reverse transcription-PCR. CONCLUSIONS: The maximum tolerated dose of vorinostat in combination with FOLFOX is 300 mg orally twice daily x 1 week every 2 weeks. Alternative vorinostat dosing schedules may be needed for optimal down-regulation of TS expression.

In vitro circuit stability of 5-fluorouracil and oxaliplatin in support of hyperthermic isolated hepatic perfusion.

Over the years, a large number of drugs have been used in isolated perfusion of extremities or organs. To interpret the pharmacokinetics of these drugs correctly, the contributions of tissue or organ clearance and chemical degradation, respectively, to overall drug elimination from the circuit need to be identified. In support of a phase I clinical trial of isolated hepatic perfusion (IHP), delivering 5-fluorouracil (5-FU) and oxaliplatin to patients with colorectal cancer hepatic metastases, we aimed to characterize the stability of 5-FU and oxaliplatin in the IHP circuit. Stability of 5-FU and oxaliplatin was assessed in human blood, lactated Ringer infusion (LRI), and in an in vitro IHP circuit consisting of both blood and LRI. Samples were analyzed with liquid chromatography tandem mass spectrometry (5-FU) and atomic absorption spectrophotometry (oxaliplatin). 5-FU was stable under all tested in vitro conditions, but ultrafilterable platinum concentrations decreased slowly with a half-life of 85 minutes in both IHP perfusate and whole blood. The stability of 5-FU in the media containing blood is likely attributable to saturation of dihydropyrimidine dehydrogenase. The decrease of ultrafilterable platinum in blood-containing media with an 85 minutes half-life is in agreement with previous reports on oxaliplatin biotransformation. Oxaliplatin and 5-FU are sufficiently stable in the circuit for the 1-hour perfusion in ongoing and planned clinical trials.

A phase I study of hyperthermic isolated hepatic perfusion with oxaliplatin in the treatment of unresectable liver metastases from colorectal cancer.

Isolated hepatic perfusion (IHP) is a proven approach for regional delivery of chemotherapy in patients with unresectable primary and metastatic tumors of the liver. Most trials of IHP have utilized melphalan as the active drug in the perfusate. We performed a phase I trial to evaluate the efficacy, safety, and maximum tolerated dose (MTD) of oxaliplatin delivered by hyperthermic isolated hepatic perfusion. A phase I dose-escalation trial of hyperthermic IHP with oxaliplatin in patients with unresectable metastatic colorectal cancer scheduled to undergo placement of a hepatic arterial infusion (HAI) pump was carried out. Thirteen patients were enrolled between November 2003 and September 2006. Dose-limiting veno-occlusive disease was observed at 60 mg/m(2). At the MTD of 40 mg/m(2) only minor transient liver dysfunction was observed. Ultrafilterable platinum area under the curve and maximum concentration delivered by IHP increased nonlinearly with dose as did platinum concentrations in liver biopsies obtained at the end of the 60 min IHP. Seventy-seven percent of patients had a >50% decrease in serum carcinoembryonic antigen (CEA) after IHP. The overall response rate to the combined IHP and HAI therapy was 66%. One patient had a durable complete response (>4 years). We conclude that hyperthermic IHP with oxaliplatin was safe and feasible at a dose of 40 mg/m(2). The ability to obtain complete vascular isolation with open IHP was confirmed. The response rate in this small phase I study was encouraging.

Disposition of temozolomide in a patient with glioblastoma multiforme after gastric bypass surgery.

Temozolomide, used for anaplastic gliomas and glioblastoma multiforme, is an oral drug that is stable under acidic, but labile under neutral and basic conditions. Although the bioavailability of temozolomide is approximately 100%, pathology or anatomical changes of the gastrointestinal tract may adversely affect absorption, and consequently therapeutic response. HPLC-UV was used to evaluate temozolomide plasma pharmacokinetics in a patient with unresponsive glioblastoma multiforme who had previously undergone gastric bypass as part of a weight-loss strategy. Temozolomide plasma pharmacokinetics were comparable to values reported for patients with normal gastrointestinal anatomy. These data imply that progression of disease in this patient was not due to inadequate temozolomide concentrations. Physicians need to become aware of the rapidly increasing population of patients who have had a gastric bypass and require oral therapy, of which our case is representative. The effect of gastric bypass on pharmacokinetics will need to be evaluated on a drug-by-drug basis.

Effect of a proton pump inhibitor on the pharmacokinetics of imatinib.

AIMS: Imatinib mesylate (Gleevec/Glivec), which has revolutionized the treatment of chronic myeloid leukemias (CML) and gastrointestinal stromal tumours (GIST), has been reported to cause gastric upset. Consequently, proton pump inhibitors (PPI) are frequently co-administered with imatinib. Because PPI can elevate gastric pH and delay gastric emptying or antagonize ATP-binding-cassette transporters, they could influence imatinib absorption and pharmacokinetics. We aimed to evaluate whether use of omeprazole has a significant effect on imatinib pharmacokinetics. METHODS: Twelve healthy subjects were enrolled in a two-period, open-label, single-institution, randomized cross-over, fixed-schedule study. In one period, each subject received 400 mg imatinib orally. In the other period, 40 mg omeprazole (Prilosec) was administered orally for 5 days, and on day 5 it was administered 15 min before 400 mg imatinib. Plasma concentrations of imatinib and its active N-desmethyl metabolite CGP74588 were assayed by LC-MS, and data were analyzed non-compartmentally. RESULTS: PPI administration did not significantly affect the imatinib area under the plasma concentration vs time curve (AUC) (34.1 microg ml(-1) h alone vs 33.1 microg ml(-1) h with omeprazole, P= 0.64; 80% power), maximum plasma concentration (C(max)) (2.04 microg ml(-1) alone vs 2.02 microg ml(-1) with omeprazole, P= 0.97), or half-life (13.4 h alone vs 14.1 h with omeprazole, P= 0.13). CONCLUSIONS: Our results indicate that the use of omeprazole does not significantly affect the pharmacokinetics of imatinib, as opposed to, for example, dasatinib where PPI decreased AUC and C(max) two-fold.

Multicenter evaluation of a novel nanoparticle immunoassay for 5-fluorouracil on the Olympus AU400 analyzer.

BACKGROUND: 5-Fluorouracil (5-FU) is the most widely used chemotherapy drug, primarily against gastrointestinal, head and neck, and breast cancers. 5-FU has large pharmacokinetic variability resulting in unexpected toxicity or ineffective treatment. Therapeutic drug management of 5-FU minimizes toxicity and improves outcome. A nanoparticle-based immunoassay was developed to provide oncologists with a rapid, cost-effective tool for determining 5-FU plasma concentrations. METHODS: Monoclonal antibodies, bound to nanoparticles, were used to develop an immunoassay for the Olympus AU400. Assay precision, linearity, calibration stability, and limit of detection were run at multiple centers; interference, cross-reactivity, lower limit of quantitation and recovery at 1 center. Clinical samples collected from 4 cancer centers were analyzed for 5-FU concentrations by liquid chromatography-tandem mass spectrometry and compared with the immunoassay results. RESULTS: With calibrators from 0 to 1800 ng/mL 5-FU and autodilution, concentrations up to 9000 ng/mL could be determined. Time to first result was 10 minutes, and 400 samples per hour could be quantitated from a standard curve stored for >30 days. Imprecision across all laboratories was <5%, and the assay was linear upon dilution over the entire range. Cross-reactivities for dihydro-5-FU, uracil, capecitabine, and tegafur were <1%, 9.9%, 0.05%, and 0.23%, respectively. The limit of detection was 52 ng/mL with a lower limit of quantitation of 86 ng/mL. Assay results of clinical samples (93-1774 ng/mL) correlated with liquid chromatography-tandem mass spectrometry results: (R = 0.9860, slope 1.035, intercept 10.87 ng/mL). CONCLUSIONS: This novel immunoassay is suitable for quantitating 5-FU plasma concentrations with advantages of speed, small sample size, minimal sample pretreatment, and application on automated instrumentation. These advantages enable efficient therapeutic drug management of 5-FU in clinical practice.

Modulation of gemcitabine (2',2'-difluoro-2'-deoxycytidine) pharmacokinetics, metabolism, and bioavailability in mice by 3,4,5,6-tetrahydrouridine.

PURPOSE: In vivo, 2',2'-difluoro-2'-deoxycytidine (dFdC) is rapidly inactivated by gut and liver cytidine deaminase (CD) to 2',2'-difluoro-2'-deoxyuridine (dFdU). Consequently, dFdC has poor oral bioavailability and is administered i.v., with associated costs and limitations in administration schedules. 3,4,5,6-Tetrahydrouridine (THU) is a potent CD inhibitor with a 20% oral bioavailability. We investigated the ability of THU to decrease elimination and first-pass effect by CD, thereby enabling oral dosing of dFdC. EXPERIMENTAL DESIGN: A liquid chromatography-tandem mass spectrometry assay was developed for plasma dFdC and dFdU. Mice were dosed with 100 mg/kg dFdC i.v. or orally with or without 100 mg/kg THU i.v. or orally. At specified times between 5 and 1,440 min, mice (n = 3) were euthanized. dFdC, dFdU, and THU concentrations were quantitated in plasma and urine. RESULTS: THU i.v. and orally produced concentrations >4 microg/mL for 3 and 2 h, respectively, whereas concentrations of >1 microg/mL have been associated with near-complete inhibition of CD in vitro. THU i.v. decreased plasma dFdU concentrations but had no effect on dFdC plasma area under the plasma concentration versus time curve after i.v. dFdC dosing. Both THU i.v. and orally substantially increased oral bioavailability of dFdC. Absorption of dFdC orally was 59%, but only 10% passed liver and gut CD and eventually reached the systemic circulation. Coadministration of THU orally increased dFdC oral bioavailability from 10% to 40%. CONCLUSIONS: Coadministration of THU enables oral dosing of dFdC and warrants clinical testing. Oral dFdC treatment would be easier and cheaper, potentially prolong dFdC exposure, and enable exploration of administration schedules considered impractical by the i.v. route.

A phase I study of 17-allylamino-17-demethoxygeldanamycin combined with paclitaxel in patients with advanced solid malignancies.

BACKGROUND: 17-Allylamino-17-demethoxygeldanamycin (17-AAG) inhibits heat shock protein 90, promotes degradation of oncoproteins, and exhibits synergy with paclitaxel in vitro. We conducted a phase I study in patients with advanced malignancies to determine the recommended phase II dose of the combination of 17-AAG and paclitaxel. METHODS: Patients with advanced solid malignancies that were refractory to proven therapy or without any standard treatment were included. 17-AAG (80-225 mg/m2) was given on days 1, 4, 8, 11, 15, and 18 of each 4-week cycle to sequential cohorts of patients. Paclitaxel (80-100 mg/m2) was administered on days 1, 8, and 15. Pharmacokinetic studies were conducted during cycle 1. RESULTS: Twenty-five patients were accrued to five dose levels. The median number of cycles was 2. Chest pain (grade 3), myalgia (grade 3), and fatigue (grade 3) were dose-limiting toxicities at dose level 4 (225 mg/m2 17-AAG and 80 mg/m2 paclitaxel). None of the six patients treated at dose level 3 with 17-AAG (175 mg/m2) and paclitaxel (80 mg/m2) experienced dose-limiting toxicity. Disease stabilization was noted in six patients, but there were no partial or complete responses. The ratio of paclitaxel area under the concentration to time curve when given alone versus in combination with 17-AAG was 0.97 +/- 0.20. The ratio of end-of-infusion concentration of 17-AAG (alone versus in combination with paclitaxel) was 1.14 +/- 0.51. CONCLUSIONS: The recommended phase II dose of twice-weekly 17-AAG (175 mg/m2) and weekly paclitaxel (80 mg/m2/wk) was tolerated well. There was no evidence of drug-drug pharmacokinetic interactions.