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G Pizzorno

Publications and source records attributed to G Pizzorno.

At least 19 recordsLinked to original sources
PubMed2000

Dose escalation and pharmacokinetic study of irinotecan in combination with paclitaxel in patients with advanced cancer.

PURPOSE: Based on preclinical data demonstrating synergy between camptothecin analogues and taxanes, we determined the maximum tolerated dose (MTD) of irinotecan that could be given in combination with a fixed dose of paclitaxel of 75 mg/m2, when both drugs were delivered on a weekly schedule. The pharmacokinetics of this combination were explored to determine whether the sequence of administration affected the elimination of irinotecan. METHODS: For the first cycle patients with advanced cancer were treated with irinotecan given as a 90-min infusion followed immediately by paclitaxel given at a dose of 75 mg/m2 over 1 h. The sequence of drug administration was reversed in subsequent cycles for most patients. Chemotherapy was given weekly for 4 weeks, followed by a 2-week rest. In selected patients, plasma concentrations of irinotecan were determined by high-performance liquid chromatography during the first 24 h of cycle 1 and after the first dose of cycle 2 to determine whether the order of drug administration affected the elimination of irinotecan, or the toxicologic effects of the chemotherapy. RESULTS: A total of 53 cycles were delivered to 21 patients. Reversible neutropenia was dose-limiting. Suppression of the other blood cell elements was modest. There was one partial response in a man with a previously treated cholangiocarcinoma that lasted 26 weeks. Prolonged stabilization of disease (6 months or more) was observed in five of the patients (24%). At the recommended dose of irinotecan (50 mg/m2), transfusions of red cells and platelets were not required. The sequence of drug administration produced no significant differences in the pharmacokinetic parameters of irinotecan or SN-38, which were similar to the values reported when irinotecan is administered alone. The most prominent nonhematologic toxicities were mild diarrhea and fatigue. CONCLUSIONS: The recommended dose of irinotecan on this schedule is 50 mg/m2. The sequence of drug administration affects neither the elimination of irinotecan nor the chemotherapy-related toxicity. This combination is well tolerated and causes minimal clinical side effects.

Aged↗
PubMed1999

Genomic structure, chromosomal mapping, and promoter region analysis of murine uridine phosphorylase gene.

Uridine phosphorylase (UPase) plays an important role in the activation of 5-fluorouracil and in the regulation of tissue and plasma concentration of uridine, a potential biochemical modulator of 5-fluorouracil therapy. UPase expression is affected by the c-H-ras oncogene and various cytokines through unknown mechanisms. To understand its expression and regulation, we cloned the murine UPase gene, defined its genomic organization, determined its 5'- and 3'-end flanking sequences, and evaluated the promoter activity. The UPase gene contains nine exons and eight introns, spanning a total of approximately 18.0 kb. Its promoter lacks canonical TATA and CCAAT boxes, although a CAATAAAAA TATA-like box is seen from -41 to -49. Furthermore, IFN regulatory factor 1, c/v-Myb, and p53 binding sites are present in the promoter region, indicating that UPase expression may be directly regulated by cytokines and oncogene products. The 1.2-kb flanking fragment showed promoter activity driving the expression of the luciferase gene in various mammalian cells. A TGGGG repeat sequence is seen in the 3'-end flanking region. This element is considered to be a potential recombination consensus hot spot that may contribute to the encoding of different UPase isoforms present in different tissues, both normal and neoplastic.

3' Untranslated Regions↗
PubMed1999

In vivo effect of 5-ethynyluracil on 5-fluorouracil metabolism determined by 19F nuclear magnetic resonance spectroscopy.

Biochemical modulation of 5-fluorouracil (5-FU) has been used over the past 20 years to improve the therapeutic efficacy of this antineoplastic agent. Recently, modulation of the catabolic pathway of this fluoropyrimidine has been the focus of extensive preclinical and clinical investigation. Dihydropyrimidine dehydrogenase catalyzes the rate-limiting step in the catabolism of 5-FU and rapidly degrades 60-90% of the drug. An irreversible inactivating inhibitor of this enzyme, 5-ethynyluracil (EU), markedly improves the antitumor effect of 5-FU in animal models. Early clinical studies have shown a substantial alteration of the systemic disposition of 5-FU with an increase in 5-FU terminal half-life and have also indicated that EU allows safe oral administration of 5-FU by improving the oral bioavailability of the fluoropyrimidine, which is otherwise too erratic and unpredictable for a drug with such a limited therapeutic window. We evaluated the effect of EU on the metabolism of 5-FU in mice bearing colon 38 tumors using 19F nuclear magnetic resonance spectroscopy. Ex vivo measurements of tissue extracts from liver, kidney, and tumor indicated a >95% elimination of alpha-fluoro-beta-ureidopropionic acid and a-fluoro-beta-alanine signals in the tissues of mice that received 2 mg/kg of EU before administration of 5-FU. The spectra also showed an increased formation of fluoronucleotides in both normal and tumor tissues, a prolonged presence of 5-FU, and the accumulation of 5-fluorouridine that otherwise is undetectable, particularly in normal tissues. The in vivo NMR experiments on colon 38 tumors confirmed these findings, showing a complete elimination of the a-fluoro-beta-ureidopropionic acid and a-fluoro-beta-alanine signals in tumors treated with EU and a dramatic formation and accumulation of 5-fluorouridine mono-, di-, and triphosphates and 5-fluorouridine. Thus, by inactivating dihydropyrimidine dehydrogenase, EU prolonged the half-life for 5-FU, almost completely eliminated its catabolism for 4-6 h, which led to an increased accumulation of 5-fluorouridine mono-, di-, and triphosphates in both normal and tumor tissues.

Animals↗
PubMed1999

beta-alanine and alpha-fluoro-beta-alanine concentrative transport in rat hepatocytes is mediated by GABA transporter GAT-2.

Studies on the compartmentalization of uridine catabolic metabolism in liver have indicated accumulation of beta-alanine as well as alpha-fluoro-beta-alanine (FbetaAL) for 5-fluorouracil in the hepatocytes. Using preparations of rat hepatocytes we were able to identify a Na+-dependent transport with high affinity for beta-alanine and GABA with Michaelis constant (Km) of 35.3 and 22.5 microM, respectively. A second Na+-dependent kinetic component with Km >1 mM was also identified. The sigmoidal profile of beta-alanine uptake with respect to Na+ shows the involvement of multiple ions of sodium in the transport process. A Hill coefficient of 2.6 +/- 0.4 indicates that at least two sodium ions are cotransported with beta-alanine. The flux of beta-alanine was also shown to be chlorine dependent. The substitution of this anion with gluconate, even in the presence of Na+, reduced the intracellular concentrative accumulation of beta-alanine to passive diffusion level, indicating that both Na+ and Cl- are essential for the activity of this transporter. The transport of beta-alanine was inhibited by GABA, hypotaurine, beta-aminoisobutyric acid, and FbetaAL in a competitive manner. However, concentrations up to 1 mM of L- and D-alanine, taurine, and alpha-aminoisobutyric acid did not affect beta-alanine uptake. Considering the similarities in substrate specificity with the rat GAT-2 transporter, extracts of hepatocytes were probed with the anti-GABA transporter antibody R-22. A 80-kDa band corresponding to GAT-2 was present in the hepatocyte and in the GAT-2 transfected Madin-Darby canine kidney cell extract, confirming the extraneural localization of this transporter. In view of these results, the neurotoxic effects related to the administration of uridine and 5-fluorouracil could be explained with the formation of beta-alanine and FbetaAL and their effect on the cellular reuptake of GABA.

Animals↗
PubMed1999

A clinical-pharmacological evaluation of percutaneous isolated hepatic infusion of doxorubicin in patients with unresectable liver tumors.

A dose escalation study of hepatic arterial infusion of doxorubicin during hemodynamic isolation of the liver (the Delcath system) was conducted to: 1) study the pharmacokinetics of regional doxorubicin therapy, and 2) define therapeutic efficacy in the treatment of unresectable liver tumors. Eighteen patients with unresectable primary or metastatic tumor in the liver were treated with 57 procedures. Pharmacokinetic studies were performed on all treatments. Hepatic extraction ratio of doxorubicin remained constant at 60.3+/-12.1%. independent of the dose escalation. The calculated intrahepatic concentration of doxorubicin ranged from 30 to 88 microg/ml when the dosage of doxorubicin was escalated from 50 to 120 mg/m2. Dose-limiting systemic toxicity (grade 4 myelosuppression) was observed at 120 mg/m2. Twelve of 14 patients who received more than one treatment at 90 or 120 mg/m2 were evaluable for disease response: there were 4 partial responses, 3 minor responses, I stable disease, and 4 progressive disease. The median overall survival of responders was 23 months, and for nonresponders it was 8 months. We have demonstrated a dose-response effect of hepatic infusion of doxorubicin at 90 and 120 mg/m2 in advanced hepatic malignancies. The isolated hepatic perfusion system improves the therapeutic index of doxorubicin and provides pharmacologic justification for its use in the treatment of unresectable hepatic malignancies, especially metastatic melanoma and sarcoma.

Adult↗
PubMed1998

Expression, characterization, and detection of human uridine phosphorylase and identification of variant uridine phosphorolytic activity in selected human tumors.

Uridine phosphorylase (UPase) catalyzes the reversible phosphorolysis of uridine to uracil. We purified the enzyme from the murine colon 26 tumor using a two-step procedure through 5-amino-benzylacyclouridine affinity chromatography. Antibodies raised in rabbits against the purified protein revealed single bands in Western blots of normal human tissue and tumor extracts. The polyclonal antibody used to screen a human liver expression library allowed the isolation of a 1.2-kb clone that contained the entire open reading frame of the human UPase. The UPase cDNA has been expressed as a fusion protein in Escherichia coli using the pMal-C2 vector. The kinetic analysis demonstrated that the recombinant UPase preferentially uses uridine, 5-fluorouracil, and uracil as substrates, although lower levels of activity were observed with 2-deoxyuridine and thymidine. Clinical samples of human tumors and adjacent normal tissues were assayed for phosphorolytic activity and sensitivity to 5-benzylacyclouridine (BAU), a potent inhibitor of the enzyme presently in Phase I-II clinical trial. Activity in normal tissues appeared to be low but very sensitive to BAU (approximately 90% inhibition at 10 microM). Tumors had generally 2-3-fold greater activity compared with adjacent normal tissues. In breast cancer specimens and head-neck squamous carcinomas, however, uridine cleavage was only partially inhibited (40-60%) by 10 or 100 microM BAU. The BAU-insensitive activity requires phosphate and pH conditions similar to the normal enzyme, and the new phosphorolytic activity was independent from thymidine phosphorylase. The BAU-insensitive phosphorolytic activity in selected tumors, coupled with the potent inhibitory activity of BAU against the "classical" uridine phosphorylase in normal human tissues, provides the rationale for combining BAU with 5-fluorouracil in the treatment of breast and head-neck tumors.

Amino Acid Sequence↗
PubMed1998

Cytosine deaminase adenoviral vector and 5-fluorocytosine selectively reduce breast cancer cells 1 million-fold when they contaminate hematopoietic cells: a potential purging method for autologous transplantation.

Ad.CMV-CD is a replication incompetent adenoviral vector carrying a cytomegalovirus (CMV)-driven transcription unit of the cytosine deaminase (CD) gene. The CD transcription unit in this vector catalyzes the deamination of the nontoxic pro-drug, 5-fluorocytosine (5-FC), thus converting it to the cytotoxic drug 5-fluorouracil (5-FU). This adenoviral vector prodrug activation system has been proposed for use in selectively sensitizing breast cancer cells, which may contaminate collections of autologous stem cells products from breast cancer patients, to the toxic effects of 5-FC, without damaging the reconstitutive capability of the normal hematopoietic cells. This system could conceivably kill even the nondividing breast cancer cells, because the levels of 5-FU generated by this system are 10 to 30 times that associated with systemic administration of 5-FU. The incorporation of 5-FU into mRNA at these high levels is sufficient to disrupt mRNA processing and protein synthesis so that even nondividing cells die of protein starvation. To test if the CD adenoviral vector sensitizes breast cancer cells to 5-FC, we exposed primary explants of normal human mammary epithelial cells (HMECs) and the established breast cancer cell (BCC) lines MCF-7 and MDA-MB-453 to the Ad.CMV-CD for 90 minutes. This produced a 100-fold sensitization of these epithelial cells to the effects of 48 hours of exposure to 5-FC. We next tested the selectivity of this system for BCC. When peripheral blood mononuclear cells (PBMCs), collected from cancer patients during the recovery phase from conventional dose chemotherapy-induced myelosuppression, were exposed to the Ad.CMV-CD for 90 minutes in serum-free conditions, little or no detectable conversion of 5-FC into 5-FU was seen even after 48 hours of exposure to high doses of 5-FC. In contrast, 70% of 5-FC was converted into the cytotoxic agent 5-FU when MCF-7 breast cancer cells (BCCs) were exposed to the same Ad.CMV-CD vector followed by 5-FC for 48 hours. All of the BCC lines tested were shown to be sensitive to infection by adenoviral vectors when exposed to a recombinant adenoviral vector containing the reporter gene betagalactosidase (Ad.CMV-betagal). In contrast, less than 1% of the CD34-selected cells and their more immature subsets, such as the CD34+CD38- or CD34(+)CD33- subpopulations, were positive for infection by the Ad.CMV-betagal vector, as judged by fluorescence-activated cell sorting (FACS) analysis, when exposed to the adenoviral vector under conditions that did not commit the early hematopoietic precursor cells to maturation. When artificial mixtures of hematopoietic cells and BCCs were exposed for 90 minutes to the Ad.CMV-CD vector and to 5-FC for 10 days or more, a greater than 1 million fold reduction in the number of BCCs, as measured by colony-limiting dilution assays, was observed. To test if the conditions were damaging for the hematopoietic reconstituting cells, marrow cells collected from 5-FU-treated male donor mice were incubated with the cytosine deaminase adenoviral vector and then exposed to 5-FC either for 4 days in vitro before transplantation or for 14 days immediately after transplantation in vivo. There was no significant decrease in the reconstituting capability of the male marrow cells, as measured by their persistence in female irradiated recipients for up to 6 months after transplantation. These observations suggest that adenovirus-mediated gene transfer of the Escherichia coli cytosine deaminase gene followed by exposure to the nontoxic pro-drug 5-FC may be a potential strategy to selectively reduce the level of contaminating BCCs in collections of hematopoietic cells used for autografts in breast cancer patients.

Adenoviridae↗
PubMed1998

Results of retroviral and adenoviral approaches to cancer gene therapy.

Genetic modification for cancer treatment has involved the introduction of chemotherapy protection and sensitization genes into normal and tumor cells, respectively, for the purpose of improving the outcome of conventional approaches to the treatment of solid tumor neoplasms. This paper will review the use of multidrug resistance-1 retroviral vectors and cytosine deaminase adenoviral prodrug activation vectors for this purpose.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed1998

Discrete roles of hepatocytes and nonparenchymal cells in uridine catabolism as a component of its homeostasis.

Previous studies indicated that uridine is essentially cleared in a single pass through a rat liver and replaced in a highly regulated manner by uridine formed presumably by de novo synthesis. We report a cellular basis for the catabolic component of this apparent paradox by dissociation of the liver with collagenase into two cell fractions, hepatocytes and a nonparenchymal cell population. Suspensions of the nonparenchymal cells rapidly cleave uridine to uracil, whereas in hepatocytes this activity was <5% of that in nonparenchymal cells. Conversely, hepatocytes cause extensive degradation of uracil to -alanine. These differences correlate with the uridine phosphorylase and dihydrouracil dehydrogenase activity in cell-free extracts of each cell type. We have documented the existence of a Na+-dependent, nitrobenzylthioinosine-insensitive transport system for uridine in the parenchymal cells (Michaelis constant 46 +/- 5 microM) that achieves a three- to fourfold concentration gradient in hepatocytes. A similar system is present in the nonparenchymal cell population. In addition, a highly specific and active Na+-dependent transport system for beta-alanine, the primary catabolic metabolite of uracil, has been demonstrated in hepatocytes.

Animals↗
PubMed1998

Phase I clinical and pharmacological studies of benzylacyclouridine, a uridine phosphorylase inhibitor.

Benzylacyclouridine (BAU, IND 039655) is a potent and specific inhibitor of uridine phosphorylase (UrdPase; EC 2.4.2.3). This enzyme plays a major role in regulating uridine homeostasis and also catalyzes the conversion of fluoropyrimidine nucleosides to their respective bases. Inhibition of UrdPase enzyme activity 18-24 h after 5-fluorouracil (5-FU) administration increased plasma levels of uridine and enhanced the therapeutic index of 5-FU by rescuing normal tissues. Moreover, in vitro preclinical studies have also shown that inhibiting UrdPase enzyme activity by BAU prior to administration of 5-FU increased cytotoxicity in a number of human cancer cell lines. A series of preclinical studies was performed in dogs and pigs to evaluate the pharmacological and pharmacodynamic properties of BAU. These data showed a sustained elevation in plasma uridine concentration in both animal models. The rapid degradation of a tracer dose of uridine into uracil was virtually arrested by BAU administered both p.o. or i.v. The t1/2 of BAU was 1.8-3.6 h in dogs, with bioavailability levels of 85% (30 mg/kg) and 42.5% (120 mg/kg). In pigs, the half-life varied from 1.6 to 2.3 h, with a bioavailability of 40% at 120 mg/kg. The drug was distributed into most tissues with a tissue: plasma ratio of approximately 0.7. On the basis of these preclinical studies, we performed a Phase I clinical trial of BAU in patients with advanced cancer. Patients received 200, 400, 800, and 1600 mg/m2 BAU as a single oral dose. Toxicities included grade 2 anemia, grade 1 fever, grade 1 fatigue, grade 1 constipation, and grade 1 elevation in alkaline phosphatase; none of these toxicities were observed to be dose dependent. The maximum tolerated dose and dose-limiting toxicity were not reached at the doses given. BAU plasma concentrations and area under the curve correlated linearly with the oral dose level. The pharmacokinetics of BAU were consistent with a first-order clearance, with average peak concentrations ranging from 19 microM (200 mg/m2) to 99 microM (1600 mg/m2) and tbeta1/2 ranging from 3.0 to 3.9 h at the four dose levels. Compared with baseline plasma uridine, treatment of patients with 200, 400, 800, and 1600 mg/m2 BAU increased peak uridine concentrations by 120, 150, 250, and 175%, respectively. On the basis of this clinical study, the suggested Phase II starting dose of BAU in combination with 5-FU is 800 mg/m2. Studies combining BAU with 5-FU and incorporating appropriate molecular and biochemical end points to assess the effects of this drug combination on tumor and/or surrogate tumor tissue are under way.

Aged↗
PubMed1997

19F NMR monitoring of in vivo tumor metabolism after biochemical modulation of 5-fluorouracil by the uridine phosphorylase inhibitor 5-benzylacyclouridine.

A uridine phosphorylase inhibitor, 5-benzylacyclouridine (BAU), has been utilized as biochemical modulator of 5-fluorouracil (5-FU) anti-tumor activity in a murine tumor model. The effect of BAU on 5-FU metabolism has been evaluated using in vitro and in vivo 19F NMR spectroscopy. The analysis of the NMR data revealed an increased formation and retention of fluorouracil nucleotides and fluorouridine in colon 38 tumors treated with the regimen containing BAU and a reduction in 5-FU catabolites (alpha-fluoro-beta-ureidopropionic acid and alpha-fluoro-beta-alanine). In the normal tissues evaluated, the presence of BAU did not significantly alter the metabolism and presence of fluoropyrimidine species, indicating a more selective effect on tumor tissues. Therapy experiments on C57/BL6 mice bearing colon 38 tumor showed that the administration of 120 mg/kg BAU 30 min before 5-FU at 85 mg/kg, on a weekly basis, resulted in an increased antineoplastic effect compared to the same dose of 5-FU alone. A smaller dose of 5-FU (60 mg/kg) also administered 30 min after 120 mg/kg BAU caused a reduction in tumor growth similar to 5-FU alone. The addition of BAU to 5-FU (85 mg/kg) resulted in a slight increase, although statistically nonsignificant, in host toxicity without causing any toxic death during the chemotherapeutic treatment. 19F NMR spectroscopy is here shown to be a powerful technique to evaluate changes in the metabolism of fluoropyrimidines after the use of biochemical modulator and to allow a correlation between improved therapeutic response with the biochemical effects generated in tissues.

Animals↗
PubMed1997

Dose-escalation and pharmacodynamic study of topotecan in combination with cyclophosphamide in patients with refractory cancer.

PURPOSE: Based on preclinical data that demonstrated synergy between alkylating agents and topoisomerase (topo) I poisons, we determined the maximum-tolerated dose (MTD) of topotecan, using a 5 day bolus schedule, that could be given in combination with a single, fixed dose of cyclophosphamide. Pharmacodynamics of this combination were explored by analyzing biochemical effects of treatment in peripheral-blood mononuclear cells (PBMCs). PATIENTS AND METHODS: Patients with refractory cancer were treated with cyclophosphamide 600 mg/m2 on day 1, followed by topotecan given as a 30-minute infusion for 5 consecutive days. Cycles were repeated every 3 weeks. Once the MTD was defined, granulocyte colony-stimulating factor (G-CSF) was added to the regimen in an attempt to escalate further the dose of topotecan. Plasma concentrations of topotecan were determined during the first treatment cycle by high-performance liquid chromatography. PBMCs were sampled at baseline and throughout the 5-day treatment period for analysis of topo I protein concentrations and to determine drug-induced DNA fragmentation. RESULTS: Twenty-six patients were treated with topotecan at doses that ranged from 0.5 mg/m2/d to 1.2 mg/ m2/d for a total of 74 cycles. Reversible neutropenia was dose-limiting, with mild to moderate suppression of the other blood-cell elements commonly occurring. Transfusions of RBCs and platelets were required in 24% and 7% of treatment cycles, respectively. The most prominent nonhematologic toxicities were fatigue and weight loss. Compared with previously published data in which topotecan was administered alone, cyclophosphamide did not appear to alter the pharmacokinetics of topotecan. Significant increases in topo I concentration were identified in PBMCs following the administration of cyclophosphamide on day 1 and there was a significant decrease in topo 1 during the 5-day course of treatment (P < .01, sign test). DNA fragmentation as a result of drug treatment was identified in 11 of 15 (73%) cycles analyzed. CONCLUSION: For previously treated patients, the recommended dose of topotecan in this schedule is 0.75 mg/m2/d without growth factor support and 1.0 mg/ m2/d if it is administered with G-CSF. Biochemical changes in cells induced by exposure to camptothecins can be measured in vivo and these effects may have important implication in the design of combination therapies and the optimal scheduling of this class of agents.

Adult↗
PubMed1997

Pharmacokinetic and phase I trial of intraperitoneal carboplatin and cyclosporine in refractory ovarian cancer patients.

PURPOSE: The feasibility and pharmacokinetics of cyclosporine (CsA) delivered intraperitoneally (IP) have not been previously explored. We performed a pharmacokinetic study of IP CsA followed by a phase I dose-escalation trial of the combination of IP CsA and carboplatin in refractory ovarian cancer patients. PATIENTS AND METHODS: A pilot study was performed of three patients who received 1, 10, and 20 mg/kg IP CsA alone. Subsequently, a phase I trial of 35 patients was performed between April 1990 and April 1993. Whole-blood and IP fluid CsA concentrations were measured at serial time points. The highest dose delivered IP was 34.6 mg CsA/kg in combination with carboplatin (250 mg/m2 or 300 mg/m2, depending on creatinine clearance), which was not dose-escalated. The area under the concentration-time curve (AUC) for CsA and half-life (T1/2) were calculated. Objective and serologic responses were noted, and toxicity was graded using the National Cancer Institute common toxicity criteria. RESULTS: The feasibility of delivering IP CsA alone was established. We observed a 1,000:1 ratio between IP fluid and blood concentrations at 20 mg CsA/kg. Pharmacokinetic analysis confirmed that at 20 mg CsA/kg, there was an IP fluid-to-blood AUC ratio of 600:1 in favor of peritoneal exposure. At the highest dose delivered, 34.6 mg CsA/kg, the mean IP CsA levels of 1,110 micrograms/ mL were tolerated moderately well and the IP fluid-to-blood ratio of 1,000:1 was maintained. Blood and IP CsA concentrations were analyzed in the presence and absence of IP carboplatin. At 20 mg CsA/kg, there was no difference in either mean blood CsA levels (0.9 microgram/ mL) or mean IP CsA concentrations (1,000 micrograms/mL) obtained in the absence or presence of carboplatin. The most common toxicity in the phase I study was anemia, seen in 66% of patients. Common toxicities at the maximum CsA dose delivered (34.6 mg/kg) were anemia, leukopenia, thrombocytopenia, and hypertension. In this trial, three objective responses (two complete and one partial) were observed for a duration of 3 to 11 months. Control of platinum-resistant ascites was an important feature, noted in five of eight patients. CONCLUSION: We have established the feasibility of delivering IP CsA up to doses of 34.6 mg/kg in conjunction with carboplatin, and the sustaining of IP fluid to blood ratios of 1,000:1. The IP administration of CsA resulted in a favorable ratio of exposure for the peritoneal cavity compared with systemic exposure, indicating a therapeutic advantage of this approach with a significant decrease in systemic toxicity. We recommend that 34.6 mg/ kg of IP CsA be tested as a phase II dose in combination with carboplatin in refractory ovarian cancer patients. This report provides the groundwork for future studies using IP CsA, both as a chemomodulator of platinum and of multidrug resistance.

Antineoplastic Agents↗
PubMed1996

Antifolates: current developments.

In summary, the problem of MTX resistance has been approached in a mechanistic fashion, based on the wealth of information generated over the years. To date, these strategies have produced several new classes of anticancer drugs, with a variety of anticipated and unanticipated mechanisms of action. Several of these have shown promising preclinical activity, and these are moving into more stringent testing in the clinic.

Aminopterin↗
PubMed1995

5-Fluoro-2-pyrimidinone, a liver aldehyde oxidase-activated prodrug of 5-fluorouracil.

5-Fluorouracil (5-FU) is an effective antitumor agent used in treating various cancers. Because of its metabolism by intestinal and other cells, 5-FU has an inconsistent bioavailability that limits its oral use. 5-Fluoro-2-pyrimidione (5-FP), a 5-FU prodrug, was synthesized and found to be converted to 5-FU by aldehyde oxidase, an enzyme present in high concentrations in the livers of mice and humans but not in the gastrointestinal tract. Using BDF1 mice, the pharmacokinetics of 5-FP were studied and compared with those of 5-FU. The bioavailability of 5-FP given orally was 100% at a dosage of 25 mg/kg and 78% at a dosage of 50 mg/kg. The half-lives of both doses of 5-FP were at least 2-fold longer than the half-lives of the same doses of 5-FU, and the clearance rates of 5-FP were 3-fold slower. 5-FP was converted rapidly to 5-FU, in vivo. The resulting 5-FU was measured at a steady-state level of 40-70 microM in plasma, at a dosage of 25 mg/kg, that was sustained for at least 4 hr. Also, when given orally, 5-FP was shown to have potent activity against Colon 38 tumor cells and P388 leukemia cells in mice. The therapeutic index of 5-FP was similar to that of 5-FU in these mouse tumor models. The potential clinical use of 5-FP as a prodrug of 5-FU should be considered.

Administration, Oral↗
PubMed1995

Aberrant cell cycle inhibition pattern in human colon carcinoma cell lines after exposure to 5-fluorouracil.

In this report, we describe the use of two human colon carcinoma cell lines, HCT-8 and HT-29, as potential models to study DNA- and RNA-directed cytotoxicity due to 5-fluorouracil (FUra) exposure by flow microfluorimetric analysis of DNA cell content. The sensitivity of the HT-29 line (EC50 = 0.9 microM) to FUra was somewhat greater than that of the HCT-8 line (EC50 = 4 microM), but each presented a dramatically different DNA histogram after exposure to FUra. In HCT-8, an unexpected and nearly complete disappearance of cells in S-phase occurred, whereas in HT-29 the expected accumulation of cells at the G1-S border was observed. The absence of HCT-8 cells in S-phase also occurred as a result of two RNA polymerase inhibitors: actinomycin D and dichloro-D-ribofuranosylbenzimidazole. However, an accumulation of cells in S-phase was observed in the presence of 5-fluorodeoxyuridine. These results suggest that in the HCT-8 cell line, FUra predominantly causes an RNA-related toxicity. By comparison, the rate of formation of 5-fluorodeoxyuridine monophosphate, the increased dUMP pool size, and low thymidylate synthase activity in the HT-29 line are consistent with its greater susceptibility to DNA-directed toxicity. Further evidence was seen in the prevention of FUra cytotoxicity by thymidine in HT-29, but not in HCT-8 cells. Similarly, Leucovorin synergized the action of FUra in HT-29 but not in HCT-8. Enzymatic correlates supporting these observations are seen in the greater activity of uridine kinase than thymidine kinase (20:1) in HCT-8 cells compared with that in HT-29 cells (4:1).

Cell Cycle↗
PubMed1995

Effect of clinically modeled regimens on the growth response and development of resistance in human colon carcinoma cell lines.

Two human colon cell lines, HCT-8 and HT-29, were exposed to 5-fluorouracil (FUra) under conditions similar to the human plasma pharmacokinetic profile achieved by a single bolus dose or a sustained i.v. infusion. The bolus treatment for 5 days caused a substantial cell kill; however, only a moderate inhibition in cell growth was obtained with sustained exposure to the clinically relevant level of 2 microM. To achieve a cell kill equivalent to the bolus method, a sustained concentration of 10 microM was required. This would constitute a 60% increase in the total area under the curve (AUC) compared with the bolus treatment. After three courses of therapy with each of the schedules, emerging cell lines displayed a similar degree of resistance. HT-29 resistant cell lines returned to the original sensitivity within a few weeks, and most of the enzymes involved in the metabolic activation of FUra returned to their pretreatment activities. However, resistance and enzymatic modifications remained in the HCT-8 line for at least 3 months. In the HCT-8 cell line derived from bolus treatment, resistance was associated with a 50-60% reduction in uridine kinase activity. In the line derived from continuous exposure, there was a 35-40% reduction in uridine kinase in addition to a greater reduction in the activity of orotate phosphoribosyltransferase. These changes in both resistant cell lines resulted in a decreased incorporation of [3H]FUra into nucleic acids and a reduced formation of di- and triphosphate nucleotides of FUra.

Cell Division↗