A Phase I and Pharmacokinetic Study of Exisulind and Docetaxel in Patients with Advanced Solid Tumors

cAMP-PKA/EPAC signaling and cancer: the interplay in tumor microenvironment

Cancer is a complex disease resulting from abnormal cell growth that is induced by a number of genetic and environmental factors. The tumor microenvironment (TME), which involves extracellular matrix, cancer-associated fibroblasts (CAF), tumor-infiltrating immune cells and angiogenesis, plays a critical role in tumor progression. Cyclic adenosine monophosphate (cAMP) is a second messenger that has pleiotropic effects on the TME. The downstream effectors of cAMP include cAMP-dependent protein kinase (PKA), exchange protein activated by cAMP (EPAC) and ion channels. While cAMP can activate PKA or EPAC and promote cancer cell growth, it can also inhibit cell proliferation and survival in context- and cancer type-dependent manner. Tumor-associated stromal cells, such as CAF and immune cells, can release cytokines and growth factors that either stimulate or inhibit cAMP production within the TME. Recent studies have shown that targeting cAMP signaling in the TME has therapeutic benefits in cancer. Small-molecule agents that inhibit adenylate cyclase and PKA have been shown to inhibit tumor growth. In addition, cAMP-elevating agents, such as forskolin, can not only induce cancer cell death, but also directly inhibit cell proliferation in some cancer types. In this review, we summarize current understanding of cAMP signaling in cancer biology and immunology and discuss the basis for its context-dependent dual role in oncogenesis. Understanding the precise mechanisms by which cAMP and the TME interact in cancer will be critical for the development of effective therapies. Future studies aimed at investigating the cAMP-cancer axis and its regulation in the TME may provide new insights into the underlying mechanisms of tumorigenesis and lead to the development of novel therapeutic strategies.

Current Advances of Nitric Oxide in Cancer and Anticancer Therapeutics

Nitric oxide (NO) is a short-lived, ubiquitous signaling molecule that affects numerous critical functions in the body. There are markedly conflicting findings in the literature regarding the bimodal effects of NO in carcinogenesis and tumor progression, which has important consequences for treatment. Several preclinical and clinical studies have suggested that both pro- and antitumorigenic effects of NO depend on multiple aspects, including, but not limited to, tissue of generation, the level of production, the oxidative/reductive (redox) environment in which this radical is generated, the presence or absence of NO transduction elements, and the tumor microenvironment. Generally, there are four major categories of NO-based anticancer therapies: NO donors, phosphodiesterase inhibitors (PDE-i), soluble guanylyl cyclase (sGC) activators, and immunomodulators. Of these, NO donors are well studied, well characterized, and also the most promising. In this study, we review the current knowledge in this area, with an emphasis placed on the role of NO as an anticancer therapy and dysregulated molecular interactions during the evolution of cancer, highlighting the strategies that may aid in the targeting of cancer.

RAC1 GTP-ase signals Wnt-beta-catenin pathway mediated integrin-directed metastasis-associated tumor cell phenotypes in triple negative breast cancers

The acquisition of integrin-directed metastasis-associated (ID-MA) phenotypes by Triple-Negative Breast Cancer (TNBC) cells is caused by an upregulation of the Wnt-beta-catenin pathway (WP). We reported that WP is one of the salient genetic features of TNBC. RAC-GTPases, small G-proteins which transduce signals from cell surface proteins including integrins, have been implicated in tumorigenesis and metastasis by their role in essential cellular functions like motility. The collective percentage of alteration(s) in RAC1 in ER+ve BC was lower as compared to ER-ve BC (35% vs 57%) (brca/tcga/pub2015). High expression of RAC1 was associated with poor outcome for RFS with HR=1.48 [CI: 1.15-1.9] p=0.0019 in the Hungarian ER-veBC cohort. Here we examined how WP signals are transduced via RAC1 in the context of ID-MA phenotypes in TNBC. Using pharmacological agents (sulindac sulfide), genetic tools (beta-catenin siRNA), WP modulators (Wnt-C59, XAV939), RAC1 inhibitors (NSC23766, W56) and WP stimulations (LWnt3ACM, Wnt3A recombinant) in a panel of 6-7 TNBC cell lines, we studied fibronectin-directed (1) migration, (2) matrigel invasion, (3) RAC1 and Cdc42 activation, (4) actin dynamics (confocal microscopy) and (5) podia-parameters. An attenuation of WP, which (a) decreased cellular levels of beta-catenin, as well as its nuclear active-form, (b) decreased fibronectin-induced migration, (c) decreased invasion, (d) altered actin dynamics and (e) decreased podia-parameters was successful in blocking fibronectin-mediated RAC1/Cdc42 activity. Both Wnt-antagonists and RAC1 inhibitors blocked fibronectin-induced RAC1 activation and inhibited the fibronectin-induced ID-MA phenotypes following specific WP stimulation by LWnt3ACM as well as Wnt3A recombinant protein. To test a direct involvement of RAC1-activation in WP-mediated ID-MA phenotypes, we stimulated brain-metastasis specific MDA-MB231BR cells with LWnt3ACM. LWnt3ACM-stimulated fibronectin-directed migration was blocked by RAC1 inhibition in MDA-MB231BR cells. In the light of our previous report that WP upregulation causes ID-MA phenotypes in TNBC tumor cells, here we provide the first mechanism based evidence to demonstrate that WP upregulation signals ID-MA tumor cell phenotypes in a RAC1-GTPase dependent manner involving exchange-factors like TIAM1 and VAV2. Our study demonstrates for the first time that beta-catenin-RAC1 cascade signals integrin-directed metastasis-associated tumor cell phenotypes in TNBC.

Wnt-beta-catenin pathway signals metastasis-associated tumor cell phenotypes in triple negative breast cancers

Tumor cells acquire metastasis-associated (MA) phenotypes following genetic alterations in them which cause deregulation of different signaling pathways. Earlier, we reported that an upregulation of the Wnt-beta-catenin pathway (WP) is one of the genetic salient features of triple-negative breast cancer (TNBC), and WP signaling is associated with metastasis in TNBC. Using cBioPortal, here we found that collective % of alteration(s) in WP genes, CTNNB1, APC and DVL1 among breast-invasive-carcinomas was 21% as compared to 56% in PAM50 Basal. To understand the functional relevance of WP in the biology of heterogeneous/metastasizing TNBC cells, we undertook this comprehensive study using 15 cell lines in which we examined the role of WP in the context of integrin-dependent MA-phenotypes. Directional movement of tumor cells was observed by confocal immunofluorescence microscopy and quantitative confocal-video-microscopy while matrigel-invasion was studied by MMP7-specific casein-zymography. WntC59, XAV939, sulindac sulfide and beta-catenin siRNA (1) inhibited fibronectin-directed migration, (2) decreased podia-parameters and motility-descriptors, (3) altered filamentous-actin, (4) decreased matrigel-invasion and (5) inhibited cell proliferation as well as 3D clonogenic growth. Sulindac sulfide and beta-catenin siRNA decreased beta-catenin/active-beta-catenin and MMP7. LWnt3ACM-stimulated proliferation, clonogenicity, fibronection-directed migration and matrigel-invasion were perturbed by WP-modulators, sulindac sulfide and GDC-0941. We studied a direct involvement of WP in metastasis by stimulating brain-metastasis-specific MDA-MB231BR cells to demonstrate that LWnt3ACM-stimulated proliferation, clonogenicity and migration were blocked following sulindac sulfide, GDC-0941 and beta-catenin knockdown. We present the first evidence showing a direct functional relationship between WP activation and integrin-dependent MA-phenotypes. By proving the functional relationship between WP activation and MA-phenotypes, our data mechanistically explains (1) why different components of WP are upregulated in TNBC, (2) how WP activation is associated with metastasis and (3) how integrin-dependent MA-phenotypes can be regulated by mitigating the WP.

Exisulind in the treatment of prostate cancer

Prostate cancer represents the most common noncutaneous malignancy in men. With the widespread use of prostate-specific antigen screening, as many as one in six men in the USA will be diagnosed with prostate cancer. Significant healthcare resources are currently devoted to the treatment of this disease, specifically aimed at improving the side effects of successful treatment. Surgery or radiation therapy provides the best chance of cure from this disease. However, as many as 50% of patients treated with curative intent will develop a recurrence 10-15 years following treatment. Hormonal ablation via medical or surgical castration provides disease control, but is associated with significant hot flushes, loss of libido and impotence. Selective, apoptotic antineoplastic drugs, such as exisulind, may provide an alternative method to treating or preventing prostate cancer. This drug profile reviews the evidence for the use of exisulind in the treatment of prostate cancer.

Customized in silico population mimics actual population in docetaxel population pharmacokinetic analysis

Population pharmacokinetic (PK) analyses have been successfully incorporated into drug dosing optimization; however, these analyses necessitate relatively large patient cohorts that many clinical trials do not have the luxury of affording. To address this problem, we developed an approach that utilizes physiologically based pharmacokinetic (PBPK) modeling coupled with Monte Carlo simulation to generate a virtual population, complete with associated patient characteristics and PK data, for population PK analysis. For this work, we used a previously published PBPK model for docetaxel and found that the systemic clearance of this drug was significantly affected by blood volume, slowly perfused tissue volume, and two liver metabolic parameters--the maximum rate of liver metabolism and the Michaelis constant for liver metabolism. These findings, as well as the PK variability predictions, are consistent with those previously associated with docetaxel clearance in population PK analyses performed with actual patient populations, namely plasma protein levels, body size, and hepatic function. Thus, this in silico exercise demonstrates the utility of simulation modeling coupled to population PK analysis for the estimation of PK variability and the identification of patient characteristics that affect a drug's PK in the absence of data assembled from large clinical trials.

A dose-ranging study of the pharmacokinetics and pharmacodynamics of the selective apoptotic antineoplastic drug (SAAND), OSI-461, in patients with advanced cancer, in the fasted and fed state

PURPOSE

To evaluate the safety, pharmacokinetics and determine the recommended dose of the selective apoptotic antineoplastic drug, OSI-461 administered on a twice-daily regimen to patients with advanced solid malignancies.

METHODS

In this phase I trial, 33 patients were treated with OSI-461 doses ranging from 400 to 1,200 mg given twice daily in 4-week cycles. Pharmacokinetic studies were performed to characterize the plasma disposition of OSI-461 and the effect of food intake on OSI-461 absorption. Secondary biomarker studies were performed to assess the biologic activity of OSI-461 including the measurement of pGSK-3beta, a PKG substrate, and pharmacogenetic studies to identify polymorphisms of CYP3A that influence drug metabolism and of ABCG2, involved in drug resistance.

RESULTS

Thirty-three patients were treated with 86 courses of OSI-461. The dose-limiting toxicities were grade 3 abdominal pain, found in one patient at the 1,000 mg BID fed dose level and all patients at the 1,200 mg BID fed dose level. There was also one episode each of grade 3 fatigue and grade 3 constipation at the 1,000 and 1,200 mg BID fed dose levels, respectively. Other common toxicities included mild to moderate fatigue, nausea, anorexia and mild elevation in bilirubin. Pharmacokinetic studies of OSI-461 revealed approximately a twofold increase in AUC(0-24) when OSI-461 was administered with food. An increase in pGSK-3beta post-dose was seen in the majority of patients and was greater at higher dose levels. No patients exhibited CYP3A4 polymorphisms, while 100% of patients were found to have the CYP3A5*3/CYP3A5*3 polymorphism. Two known polymorphisms of the ABCG2 gene, G34 --> A34 and C421 --> A421, occurred at frequencies of 11.76 and 29%, respectively.

CONCLUSIONS

Toxicity and pharmacodynamic data show that the recommended oral dose of OSI-461 is 800 mg twice daily administered with food. The drug appears to be well-tolerated, and overall bioavailability appears to be markedly increased when the drug is administered with food. These results support further disease-directed evaluations of OSI-461 at a dose of 800 mg BID in combination with other chemotherapeutic agents.

Sulindac and its metabolites induce carcinogen metabolizing enzymes in human colon cancer cells

Sulindac is a nonsteroidal antiinflammatory drug that has been demonstrated to be a potent chemopreventive agent against colorectal cancer in both human and animal models. In vivo, sulindac may be reversibly reduced to the active antiinflammatory compound, sulindac sulfide, or irreversibly oxidized to sulindac sulfone. Sulindac has also been shown to inhibit polycyclic aromatic hydrocarbon (PAH)-induced cancer, but the molecular mechanisms of its antitumor effect remain unclear. In this study, we investigated the effects of sulindac and its metabolites on the expression of enzymes that metabolize and detoxify PAHs in 2 human colon cancer cell lines, LS180 and Caco-2. Sulindac and sulindac sulfide induced a sustained, concentration-dependent increase in CYP enzyme activity as well as an increase in the mRNA levels of CYP1A1, CYP1A2 and CYP1B1. Sulindac and sulindac sulfide induced the transcription of the CYP1A1 gene, as measured by the level of heterogeneous nuclear CYP1A1 RNA and verified by the use of actinomycin D as a transcription inhibitor. Chromatin immunoprecipitation assays demonstrated that sulindac and sulindac sulfide also increased the nuclear level of activated aryl hydrocarbon receptor, the transcription factor which mediates CYP expression. Additionally, sulindac and both metabolites increased the activity and mRNA expression of the carcinogen detoxification enzyme NAD(P)H:quinone oxidoreductase, as well as the expression of UDP-glucuronosyltransferase mRNA. These results show an overall upregulation of carcinogen metabolizing enzymes in colon cancer cells treated with sulindac, sulindac sulfide and sulindac sulfone that may contribute to the established chemoprotective effects of these compounds.

Docetaxel and exisulind in previously treated non-small cell lung cancer (NSCLC) patients: a multicenter, phase II clinical trial

PURPOSE

This multicenter, phase II clinical trial was conducted to evaluate the activity of the combination of docetaxel and exisulind in advanced non-small cell lung cancer (NSCLC) patients who failed a prior platinum-containing regimen.

PATIENTS AND METHODS

Patients with measurable disease and adequate organ function received exisulind (250 mg) given orally, twice daily, and docetaxel (36 mg/m) administered intravenously on days 1, 8, and 15 of a 4-week cycle for up to six cycles. In the absence of disease progression or intolerable side effects, patients continued taking 250 mg of exisulind orally, twice daily.

RESULTS

Thirty-three patients (median age 60 years; range 34-77; median performance status 1) were enrolled. There were no objective responses documented. Sixteen patients [48%, 95% confidence interval (CI): 31%-66%] had stable disease after 8 weeks of treatment. Median progression-free survival (PFS) was 2.1 months (95% CI: 1.5-3.2 months); median overall survival time was 8.0 months (range 0.2-25.9 months). Toxicity was moderate, with dose adjustment for adverse event/toxicity required for docetaxel or exisulind in 13 (39.3%) patients. Grade 3/4 lymphopenia, neutropenia, and anemia occurred in 48.5%, 12.1%, and 9.1% of patients, respectively. Grade 3 or greater toxicity was seen in 12.1%, 6.1%, and 3% of patients for nausea/vomiting, dyspnea, and abdominal pain, respectively.

CONCLUSIONS

Treatment with exisulind and weekly docetaxel was not active in NSCLC patients who failed a prior platinum-containing regimen. Further study of this combination does not seem warranted.

Phase I/II study of gemcitabine and exisulind as second-line therapy in patients with advanced non-small cell lung cancer

BACKGROUND

The study was designed to evaluate the safety and efficacy of exisulind, a selective apoptotic antineoplastic drug, in combination with gemcitabine as second-line therapy in patients with progressing advanced non-small cell lung cancer.

METHODS

Patients whose disease progressed more than 3 months from completion of first-line chemotherapy were eligible for this phase I/II trial. Primary end points were maximally tolerated dose and time to progression. Patients in the phase I portion of the study were treated with gemcitabine (1250 mg/m) in combination with three escalated dose levels of exisulind. Treatment involved six cycles of gemcitabine and exisulind followed by exisulind maintenance. The study was subsequently expanded to phase II.

RESULTS

Thirty-nine patients (15 in phase I and 24 in phase II) were treated. The regimen was well tolerated with grade 3 fatigue and grade 3 constipation being dose-limiting toxicities. The maximally tolerated dose was not reached. Dose level 3 of exisulind (250 mg twice daily) in combination with gemcitabine was used for phase II. The overall response rates were 7% (phase I), 17% (phase II), and 13% (all). Median time to progression and median and 1-year survival, respectively, were 3.7 and 9.7 months and 33% (phase I); 4.3 and 9.4 months and 41% (phase II); and 4.1 and 9.4 months and 39% (all).

CONCLUSION

Although the study met its primary end point of improving time to progression (more than 4.1 months in phase II), we did not observe a clear survival advantage and thus do not plan to further investigate this schedule of gemcitabine and exisulind.

A Physiologically Based Pharmacokinetic Model of Docetaxel Disposition: from Mouse to Man

PURPOSE

Docetaxel (Taxotere), an important chemotherapeutic agent with shown activity in a broad range of cancers, is being investigated for use in combination therapies and as an antiangiogenic agent. Docetaxel exhibits a complex pharmacologic profile with high interpatient variability. Pharmacokinetic models capable of predicting exposure under various dosing regimens would aid the rational development of clinical protocols.

EXPERIMENTAL DESIGN

A pharmacokinetic study of docetaxel at 5 and 20 mg/kg was carried out in female BALB/c mice. Tissues were collected at various time points and analyzed by liquid chromatography-tandem mass spectrometry. Time course tissue distribution and pharmacokinetic data were used to build and validate a physiologically based pharmacokinetic (PBPK) model in mice. Specific and nonspecific tissue partitioning, metabolism, and elimination data were coupled with mouse physiologic variables to develop a PBPK model that describes docetaxel plasma and tissue pharmacokinetic. The PBPK model was then modified with human model variables to predict the plasma distribution of docetaxel.

RESULTS

Resulting simulation data were compared with actual measured data obtained from our pharmacokinetic study (mouse), or from published data (human), using pharmacokinetic variables calculated using compartmental or noncompartmental analysis to assess model predictability.

CONCLUSIONS

The murine PBPK model developed can accurately predict plasma and tissue levels at the 5 and 20 mg/kg doses. The human PBPK model is capable of estimating plasma levels at 30, 36, and 100 mg/m(2). This will enable us to develop and test various dosing regimens (e.g., metronomic schedules and combination therapies) to achieve specific tissue and plasma concentrations to maximize therapeutic benefit while minimizing toxicity.

A phase I clinical and pharmacokinetic study of tipifarnib in combination with docetaxel in patients with advanced solid malignancies

PURPOSE

This phase I study assessed the maximum tolerated doses (MTDs), safety, pharmacokinetics, and efficacy of combined tipifarnib and docetaxel treatment in patients with advanced solid malignancies.

EXPERIMENTAL DESIGN

The study protocol was sensitive to myelosuppression, as both drugs have been associated with this adverse event. Due to myelosuppression incidence, and in order to determine the MTD of docetaxel, multiple treatment regimens were employed. Tipifarnib was administered orally at 200 or 300 mg, twice daily (BID) for 21 days, 14 days, or 7 days for multiple 21-day cycles; intravenous (i.v.) docetaxel was administered on day 1 of each cycle at 60, 75, or 85 mg/m2.

RESULTS

A total of 36 patients entered into the study. For each drug, MTDs were identified (tipifarnib: 300 mg BID for 14 days with 60 mg/m2 docetaxel; tipifarnib: 200 mg BID for 14 days with 75 mg/m2 docetaxel). The major dose-limiting toxicity was myelosuppression, particularly febrile neutropenia (44%). Mutual pharmacokinetic interactions (the effect of docetaxel on tipifarnib pharmacokinetics and the effect of tipifarnib on docetaxel pharmacokinetics) were not evident, as maximum plasma concentration (Cmax) and the area under the serum concentration-time curve (AUC) values of both tipifarnib and docetaxel were similar (p > or = 0.43) whether the two drugs were concomitantly administered or not. Seven of 31 evaluable patients (23%) had an objective response, 11 (35%) had stable disease (six > or = 24 weeks), and the overall clinical benefit rate (objective response and/or stable disease > or = 24 weeks) was 42%.

CONCLUSIONS

Although the high incidence of febrile neutropenia necessitated a multiple scheduling adaptation of tipifarnib compared to the original protocol, the apparent lack of mutual pharmacokinetic interactions, the ability to coadminister tipifarnib and docetaxel near single-agent MTDs, and suggestive evidence of efficacy make this drug combination attractive for further examination.

A comparison of the effectiveness of selected non-steroidal anti-inflammatory drugs and their derivatives against cancer cells in vitro

PURPOSE

Previously, we reported in vitro observations suggesting that ibuprofen is an effective non-prescription non-steroidal anti-inflammatory drug (NSAID) to reduce the survival of human prostate cancer cells (Andrews et al. in Cancer Chemother Pharmacol 502:77-284, 2002), and that this observed effectiveness is mediated by an up-regulation of the p75 NTR tumor suppressor (Khwaja et al. in Cancer Res 646:207-6213, 2004). However, other NSAIDs and their derivatives have received significant attention with regard to their anti-cancer effectiveness and have been selected for clinical trials to treat a variety of human cancers. In this investigation, we compared celecoxib, sulindac sulfone, nitric oxide linked NSAIDs, and R-flurbiprofen with ibuprofen in their ability to inhibit the growth of a variety of human cancer cells lines including cells lines with multi-drug resistance. We also evaluated whether, like ibuprofen, an up-regulation of p75 NTR is a molecular mechanism that mediates the anti-growth effectiveness of these drugs.

MATERIALS AND METHODS

Selected dosages for each drug were evaluated for their ability to reduce the growth (MTT analysis) and induce apoptosis (Hoechst staining) of a variety of different cancer cell lines, including an ovarian cell line expressing multidrug resistance-1 glycoprotein (MDR-1). The drugs were then analyzed using immunoblot, RT-PCR and siRNA to study the role of p75 NTR in their anti-growth effectiveness.

RESULTS

Our study revealed consistency in the drug dosages that inhibit the survival of different human cancer cell lines. While NO-linked aspirin and celecoxib were most effective in decreasing cell growth and inducing apoptosis at the lowest dosages, R-flurbiprofen and ibuprofen were most effective at clinically relevant dosages. A multidrug resistant ovarian cell line is more resistant to growth inhibition by the drugs tested than its non-drug resistant parental counterpart. There was no correlation between the expression of cyclooxygenase-2 (COX-2) and the ability of the drugs to reduce cancer cell survival. All the drugs tested induced an up-regulation in p75 NTR tumor suppressor gene expression in concert with their observed growth inhibiting ability. Inhibition of p75 NTR expression with siRNA reduced the cell growth inhibiting effects of all the drugs tested.

CONCLUSIONS

The method of chemotherapy (i.e., intravascular, intrathecal, oral) might dictate the choice of NSAID/NSAID derivative used to treat/prevent a given type of cancer. Also, the p75 NTR tumor suppressor appears to be a common molecular mechanism that mediates the growth inhibiting effectiveness of these drugs.

Alpha-tocopheryl succinate sensitizes human colon cancer cells to exisulind-induced apoptosis

Sulindac sulfone (also known as exisulind) and its chemical derivatives are promising anticancer agents capable of inducing apoptosis in a variety of malignant cell types with minimal toxicity to normal cells. Here, we tested the ability of alpha-tocopheryl succinate (TOS), another promising anticancer agent, to sensitize colon cancer cells to exisulind-induced apoptosis. We found that sub-apoptotic doses of TOS greatly enhanced exisulind-induced growth suppression and apoptosis in the HCT116, LoVo and SNU-C4 human colon cancer cell lines. Our results revealed that this was accounted for primarily by an augmented cleavage of poly(ADP-ribose) polymerase (PARP) and enhanced activation of caspase-8, -9 and -3. Pretreatment with z-VAD-FMK (a pan-caspase inhibitor), z-IETD-FMK (a caspase-8 inhibitor) or z-LEHD-FMK (a caspase-9 inhibitor) blocked TOS and exisulind cotreatment-induced PARP cleavage and apoptosis. Furthermore, TOS/exisulind cotreatment induced JNK phosphorylation, while pretreatment with SP600151 (a JNK inhibitor) partially blocked cotreatment-induced caspase-dependent PARP cleavage and apoptosis. Taken together, these findings indicate that TOS sensitizes human colon cancer cells to exisulind-induced apoptosis. Apoptotic synergy induced by exisulind plus TOS seems likely to be mediated through a mechanism involving activation of caspases and JNK.

Capillary electrophoresis combining field-amplified sample stacking and electroosmotic flow suppressant for analysis of sulindac and its two metabolites in plasma

Field-amplified sample stacking with electroosmotic flow (EOF) suppressant in capillary electrophoresis was used to determine the concentration of sulindac (SU) and its two active metabolites, sulindac sulfide (SI) and sulindac sulfone (SO), in human plasma. After acidification, the analytes were extracted from the plasma with dichloromethane. Before sample loading, a water plug (0.5 psi, 3 s) was injected to contain sample anions and to permit field-amplified stacking. Electrokinetic injection at a reversed voltage (-6 kV, 99.9 s) was then used to introduce anions. Separation was performed using phosphate buffer (80 mM, pH 6.0) containing 2,6-di-O-methyl-beta-cyclodextrin (0.75 mM), and poly(ethylene oxide) (0.01%) as an EOF suppressant. The separation was performed at -30 kV and 200 nm. During method validation, calibration plots were linear (r > 0.994) over a range of 0.3-30.0 microM for SU and SO, and 0.5-30.0 microM for SI. During intra- and inter-day analysis, relative standard deviations (RSD) and relative errors (RE) were all less than 16%. The limits of detection were 0.1 microM for SU and SO, and 0.3 microM for SI (S/N = 4, sampling 99.9s at -6 kV). This method was feasible for determining SU and its metabolites in plasma. One female volunteer (27 years, 42 kg) was orally administered one SU tablet (Clinoril, 20 0 mg/tab), and blood samples were drawn at regular intervals over an 8h period. After pretreatment and analysis, the plasma levels of SU, SI and SO were monitored. The pharmacokinetic profile of SU was also investigated.

Preclinical experience with docetaxel in gastrointestinal cancers

Docetaxel is a semisynthetic taxane that acts primarily by promoting microtubule assembly and preventing the depolymerization of assembled microtubules, thereby inducing mitotic block and inhibition of cell proliferation. This agent also induces apoptosis and appears to prevent angiogenesis. Although docetaxel has shown efficacy in a wide variety of tumors, it has only recently been evaluated in the treatment of gastrointestinal cancers. Data from preclinical studies have shown that docetaxel has substantial in vitro and in vivo activity against gastric, esophageal, and pancreatic tumors. The cytotoxic activity of docetaxel is generally time- and dose-dependent, and greater than that produced by other chemotherapeutic agents, including paclitaxel and anthracyclines. Studies evaluating combination regimens suggest that docetaxel has additive-to-synergistic antitumor activity against gastrointestinal cancers over that produced by the individual agents, and the increased antitumor activity appears to be schedule-dependent. These data suggest that docetaxel has promising therapeutic activity in the treatment of gastrointestinal cancers and provides a rationale for its inclusion in therapeutic protocols either as a single agent or in combination regimens. In addition to combination regimens with conventional chemotherapeutic agents, early studies with a number of novel molecularly targeted therapies in combination with docetaxel have shown encouraging results. These studies provide a basis for pursuing future clinical trials with docetaxel-based combinations of novel therapies for improving response rates in the treatment of gastrointestinal cancers.