Development of bisphosphonates controlled delivery systems for bone implantation: influence of the formulation and process used on in vitro release.

The present study investigates the development of controlled drug delivery devices by association of bisphosphonates (BPs) with calcium-deficient apatite (CDA) to obtain a prolonged drug delivery. In a first part, we studied the microencapsulation of methylene bisphosphonic acid, our model of BPs, in biodegradable PLGA by the double emulsion (w/o/w) solvent evaporation/extraction process. Secondly, we associated BPs, either in a free form or microencapsulated, with calcium phosphate biomaterials. The association of free BPs with CDA was performed by isostatic compression at 80 MPa and we tested the interest of adding a binder, HPMC, in the formulation to reinforce the association. In parallel, microparticles were associated with calcium-deficient apatite, either by simple mixture or by isostatic compression. To compare the different formulations, in vitro dissolution studies were performed. All the formulations tested appear to be efficient to produce BPs loaded biomaterials able to deliver the drug slowly and at a constant rate. The slowest release rate (2.7% in 14 days) was obtained with the blend of microencapsulated BPs with CDA.

Biphasic calcium phosphate: a comparative study of interconnected porosity in two ceramics.

Interconnection, one of the main structural features of macroporous calcium-phosphate ceramics, contributes to the biological and physicochemical properties of bone substitutes. As no satisfactory method exists for evaluating this feature, analysis was performed to determine the permeability, tortuosity, and equivalent diameter of interconnecting channels, that is the parameters that appear to be representative of the way pores are linked. The testing of two ceramics with similar porosity levels revealed important differences in all three interconnection parameters. One ceramic showed poor permeability, corresponding to a small equivalent diameter for interconnecting channels in conjunction with a high tortuosity factor, while the other displayed high permeability, a large diameter for interconnecting channels, and a low tortuosity factor. The methodology used, which can be applied to the quantification of interconnection in all calcium-phosphate ceramics, constitutes the first step in a complete study of the role of this feature in cellular colonization of the ceramic, matrix dissolution, and drug release from the calcium-phosphate matrix.

Transactivation of the metallothionein promoter in cisplatin-resistant cancer cells: a specific gene therapy strategy.

BACKGROUND: Cisplatin (cis-diamminedichloroplatinum) is one of the most active agents against a broad range of malignancies, including ovarian cancer. Cisplatin resistance appears to be associated with several molecular alterations, including overexpression of metallothionein, a metal-binding protein. In the present study, we attempted to take advantage of metallothionein overexpression to overcome cisplatin resistance. METHODS: Using a virus-free system (liposomes), we sought to express the suicide gene, thymidine kinase (TK), driven by the promoter of the human metallothionein IIa (hMTIIa) gene using the pMT-TK plasmid. We used cisplatin-resistant human ovarian carcinoma cells as a model. RESULTS: We first analyzed metallothionein expression using a ribonuclease protection assay. In comparison to parental cells, the cisplatin-resistant cells were found to have increased expression of metallothionein messenger RNA (mRNA). Metallothionein overexpression in these cells was not associated with an increased copy number of the hMTIIa gene or with different transfection efficiencies. Furthermore, we showed by reverse transcription-polymerase chain reaction analysis that transfection of the pMT-TK plasmid results in a 56-fold higher expression of thymidine kinase mRNA in cisplatin-resistant cells compared with parental cells, consistent with increased metallothionein promoter-mediated transactivation in the cisplatin-resistant cells. Transfection of resistant cells with pMT-TK or a control plasmid (pCD3-TK) resulted in a marked sensitization to ganciclovir, with a 50% cell growth-inhibitory concentration (IC(50)) of 20 microg/mL and 9 microg/mL, respectively. Transfections of the cisplatin-sensitive cells resulted in no sensitization to ganciclovir with pMT-TK (IC(50) 200 microg/mL) and a high sensitization with pCD3-TK (IC(50) = 6 microg/mL). CONCLUSION: These studies suggest that pMT-TK gene therapy may provide an alternative treatment for cisplatin-refractory ovarian tumors.

Selective killing of glioma cell lines using an astrocyte-specific expression of the herpes simplex virus-thymidine kinase gene.

Gene therapy using the herpes simplex virus thymidine kinase gene (HSV-TK) is a promising new approach for the treatment of gliomas, a tumor type with a poor prognosis. To limit the toxic effects of this procedure, it is desirable to restrict expression of the HSV-TK gene to the target cells. This can be accomplished by use of the promoter of the glial fibrillary acidic protein gene, an intermediate filament protein expressed primarily in astrocytes. A plasmid containing the HSV-TK gene, driven by the human glial fibrillary acidic protein promoter gfa2, was lipofected into glioma cell lines and into an ovarian cancer cell line. Treatment with ganciclovir showed efficient killing of glioma cells, with no effect on the ovarian cells. Thus, the gfa2 promoter is a promising candidate for directing expression of toxic genes to gliomas.

Main drug- and carcinogen-metabolizing enzyme systems in human non-small cell lung cancer and peritumoral tissues.

To better understand the importance of drug-metabolizing enzymes in carcinogenesis and anticancer drug sensitivity of human non-small cell lung cancer, we studied the main drug-metabolizing enzyme systems in both lung tumors and their corresponding nontumoral lung tissues in 12 patients. The following enzymes were assayed by Western blot analysis: cytochromes P-450 (1A1/A2, 2B1/B2, 2C8-10, 2E1, 3A4); epoxide hydrolase; and glutathione S-transferase isoenzymes (GST-alpha, -mu, and -pi). The activity of the following enzymes or cofactor were determined by spectrophotometric or fluorometric assays: glutathione S-transferase (GST); total glutathione; UDP-glucuronosyltransferase; beta-glucuronidase; sulfotransferase; and sulfatase. Results showed the presence of cytochrome P-450 1A1/1A2 in both tumoral and nontumoral tissues. P-450 1A1/1A2 levels were 3-fold lower in tumors compared to corresponding nontumoral tissues (P < 0.05). None of the other probed cytochromes P-450 were detected in either tumoral or nontumoral lung tissues. For the glutathione system, no significant difference between tumoral and nontumoral tissues was observed (GST activity, glutathione content, GST-alpha, -mu, and -pi). A positive linear correlation was observed between GST activity and GST-alpha or GST-pi. No significant difference was observed for the glucuronide and the sulfate pathways and their corresponding hydrolytic enzymes. Epoxide hydrolase was significantly decreased in tumors compared to nontumoral lung tissues (P < 0.05). In conclusion, these results showed differences between non-small cell lung tumors and nontumoral tissues for cytochrome P-450 1A1/1A2 and epoxide hydrolase. These differences between tumors and peritumoral tissues with regard to these drug-metabolizing enzymes could reflect differences occurring after malignant transformation and may play a role in drug sensitivity to anticancer drugs.

Chronopharmacology of high-dose busulfan in children.

In bone marrow transplantation, high-dose busulfan is given p.o., usually every 6 h over 4 consecutive days. Since this repeated administration might alter busulfan disposition, fluctuations in busulfan plasma levels were studied over the 4-day treatment period in 21 children (median age, 5 years) with malignant solid tumors. In addition, urinary excretion of unchanged busulfan was measured every 6 h in 4 patients. Busulfan (37.5 mg/m2 for 16 doses) was given on an empty stomach at 12 p.m., 6 p.m., midnight, and 6 a.m. for 4 consecutive days, starting at 12 p.m. Trough plasma levels, i.e., concentration 6 h after each dose and just before the next one, and urinary excretion of busulfan were measured using a gas chromatography-mass spectrometry assay. Busulfan trough plasma levels exhibited a significant circadian rhythm with a higher mean level at 6 a.m. compared to that at 12 p.m., 6 p.m., and midnight. This rhythm was characterized by a double amplitude (mean +/- SD) of 42 +/- 14% and an acrophase (maximum) occurring at 5:48 a.m. +/- 115 min. In addition, once the steady state was reached, no decreasing trend was observed in any patient. Busulfan renal clearance proved to be low since only 5.4 +/- 1.2% of the given dose were excreted unchanged in urine. In the 4 patients studied, busulfan urinary excretion exhibited a significant circadian rhythm which was apparently linked to the physiological circadian rhythm in urinary output. Ten of 20 evaluable patients developed hepatic venoocclusive disease (HVOD). A significant circadian rhythm in the plasma level was found in both HVOD and non-HVOD patients with no difference between the two groups with regard to the 24-h mean, amplitude, or acrophase. Thus, the circadian changes in busulfan trough plasma levels observed at the steady state were not related to the occurrence of HVOD in these children with solid tumors. Moreover, since this rhythm was stable from day 2 to day 4, it should not compromise dose adjustment.

Pharmacokinetic and pharmacodynamic advantages of pirarubicin over adriamycin after intraarterial hepatic administration in the rabbit VX2 tumor model.

Intraarterial chemotherapy with Adriamycin (ADM) has shown limited advantages over i.v. administration, with no reduction in systemic toxicities and modest decrease in peripheral plasma levels. In an effort to improve the selectivity of i.a. anthracycline chemotherapy, we compared pirarubicin (4'-O-tetrahydropyranyladriamycin, THP) and ADM in the surgically implanted VX2 rabbit tumor model. Both drugs were administered at the same dose (0.5 mg/kg) either by the intraarterial hepatic route (i.a.h.) or by the i.v. route. Anthracycline plasma and tissue levels were determined by high-performance liquid chromatography with fluorescence detection. ADM peak plasma concentration and area under the curve were not significantly reduced after i.a.h. administration compared to the i.v. route; however, ADM tumor concentration was 1.9-fold higher following i.a.h. administration compared to the i.v. infusion. After THP administration by the i.a.h. route, systemic exposure (area under the curve) was markedly reduced (8-fold) compared to the same dose administered i.v. These findings correlated well with the very low concentration of the drug in heart tissue following i.a.h. infusion. After i.a.h. administration, tumor THP concentrations were 10.5 times higher compared to the i.v. route. The pharmacokinetic advantage of i.a.h. administration of THP also led to a better antitumoral effect, as shown by a significantly lower tumor growth rate [3 +/- 2% (SD)] in the i.a.h.-treated animals compared to the i.v.-treated groups (58 +/- 9%). Administration of ADM by the i.a.h. route was also inferior to i.a.h. THP. Taken together, our results suggest a clear-cut advantage of THP over ADM for i.a.h. locoregional chemotherapy, because of higher local tumor concentrations, greater antitumoral effect, and lower systemic exposure following the i.a.h. administration of THP. This anthracycline analogue could also be of therapeutic advantage in tumors partially resistant to anthracyclines that would become vulnerable to the high local concentrations achieved with i.a.h. administration. Based on these encouraging results, clinical trials using THP administered by the i.a.h. route were initiated.

Phase I and pharmacokinetic study of the camptothecin derivative irinotecan, administered on a weekly schedule in cancer patients.

Irinotecan (CPT-11) is a novel water-soluble, semisynthetic derivative of camptothecin, with inhibitory effects on mammalian DNA topoisomerase I, high cytotoxic activity in vitro and anticancer activity in animal models. Fifty-nine patients, with cancer refractory to conventional therapy, were entered in this phase I study, using a weekly schedule administration. A total of 304 weekly doses were administered at dose levels ranging from 50 to 145 mg/m2 (30-90 min i.v. infusion). Leukoneutropenia and diarrhea were the dose-limiting toxicities and appeared to be dose related, reversible and noncumulative. However, interpatient variability of toxic effects was substantial. Prolongation of the infusion time from 30 min to 90 min appeared to decrease the diarrhea. Other toxicities included moderate emesis, asthenia, alopecia, abdominal pain, and anemia. CPT-11 plasma disposition was bi- or triphasic with a terminal half-life of 9.3 h. CPT-11 area under the plasma concentration versus time curves increased linearly with dose (r = 0.47, P < 0.01). The active metabolite area under the plasma concentration versus time curve correlated significantly with that of CPT-11, but not with that of CPT-11 dose. Both CPT-11 and 7-ethyl-10-hydroxycamptothecin areas under the plasma concentration versus time curve correlated significantly with leukoneutropenia and diarrhea. One partial and 4 minor responses were observed at dose levels of 130 and 145 mg/m2. Using this weekly schedule, recommended doses for phase II studies are 100 mg/m2 in high risk patients and 115 mg/m2 in others.

Main drug-metabolizing enzyme systems in human breast tumors and peritumoral tissues.

In an attempt to better understand breast tumors sensitivity or resistance to anticancer drugs, the main drug-metabolizing enzyme systems were evaluated in both breast tumors and their corresponding peritumoral tissues in 12 patients. The following enzymes were assayed by Western blot: cytochromes P-450 (1A1/A2, 2B1/B2, 2C8-10, 2E1, 3A4); glutathione S-transferases (GST-alpha, -mu, and -pi); and epoxide hydrolase. The activity of the following enzymes or cofactor were determined by spectrophotometric or fluorometric assays: GST; total glutathione; UDP-glucuronosyltransferase; beta-glucuronidase; sulfotransferase; and sulfatase. Results showed the absence of all probed cytochromes P-450 in both tumoral and peritumoral tissues. GST activity was significantly (P < 0.05) higher in tumors (mean +/- SD, 399 +/- 362 nmol/min/mg) than in corresponding peritumoral tissues (86 +/- 67). The GST isoenzymes GST-mu and GST-pi (determined by immunoblotting) were also higher in tumors than in corresponding peritumoral tissues (3- and 5-fold, respectively). Both GST-mu and GST-pi levels were significantly correlated with GST activity. GST-alpha was not detected in either tumoral or peritumoral tissues. Glutathione levels in tumors (22 +/- 23 nmol/mg protein) were not statistically different from peritumoral tissues (11 +/- 12). Epoxide hydrolase was expressed at similar levels in tumors and peritumoral tissues. The glucuronide-forming enzyme UDP-glucuronosyltransferase was 5-fold lower in tumors (0.1 +/- 0.2 nmol/h/mg) than in peritumoral tissues (0.5 +/- 1), whereas the opposite was observed for the hydrolytic enzyme beta-glucuronidase, which was 6-fold higher in tumors (736 +/- 1392 nmol/h/mg) compared to peritumoral tissues (125 +/- 75). No difference was noted between tumoral and peritumoral tissues for sulfotransferase (1 +/- 2 nmol/h/mg), but the corresponding hydrolytic enzyme (sulfatase) was 2-fold higher in tumoral tissues (14 +/- 15 nmol/h/mg) than in peritumoral tissues (6 +/- 2). In conclusion, several differences were observed between human breast tumors and peritumoral tissues for many conjugating enzymes (GST-mu, GST-pi, and UDP-glucuronosyltransferase) and hydrolytic enzymes (sulfatase and beta-glucuronidase). These noteworthy differences between tumoral and peritumoral tissues with regard to their main drug-metabolizing enzymes could play a role in the relative drug sensitivity or insensitivity of human breast cancer tissues to chemotherapeutic agents and could be potential targets for chemotherapeutic interventions.

Comparison of mouse and human colon tumors with regard to phase I and phase II drug-metabolizing enzyme systems.

Since human colorectal tumors are insensitive to most chemotherapeutic agents, there is a need for the discovery of new drugs that would show activity against this disease. In an attempt to better appreciate the relevance of a widely used mouse colon tumor (colon adenocarcinoma Co38) as a screening model for human colorectal tumors, we compared the main phase I and phase II drug-metabolizing enzyme systems in both tumoral and nontumoral colon tissues. The following enzymes were assayed by Western blot: cytochromes P-450 (1A1/A2, 2B1/B2, 2C, 2E1, and 3A), epoxide hydrolase, and glutathione-S-transferases (GST-alpha, -mu, and -pi). The activities of the following enzymes or cofactors were determined by spectrophotometric or fluorometric assays: total cytochrome P-450, 1-chloro-2,4-dinitrobenzene-GST, selenium-independent glutathione peroxidase, 3,4-dichloronitrobenzene-GST, ethacrynic acid-GST, total glutathione, epoxide hydrolase, UDP-glucuronosyltransferase, beta-glucuronidase, sulfotransferase, and sulfatase. Results obtained by Western blot showed that mouse colon adenocarcinoma Co38 did not express any of the probed cytochromes P-450, whereas human colorectal tumors expressed only low levels of cytochrome P-450 3A. GST-alpha and GST-pi were detected in all tumoral and nontumoral tissues of both species. The neutral GST-mu was expressed in all murine tissues investigated and was found to be polymorphic in human tissues. For human peritumoral and tumoral colorectal tissues there was no significant difference between GST isoenzyme levels, whereas mouse colon adenocarcinoma Co38 had a lower expression of GST-mu and GST-pi, compared to normal mouse colon. Enzymatic activities for glutathione peroxidase, 3,4-dichloronitrobenzene-GST, and ethacrynic acid-GST confirmed the Western blot results for GST-alpha, GST-mu, and GST-pi, respectively. Total GSH levels were similar between murine and human tumors but were 3-fold higher in human tumors than in peritumoral tissues, whereas they were 7-fold lower in mouse colon tumor Co38, compared to normal mouse colon. Epoxide hydrolase was not expressed in either mouse colon adenocarcinoma Co38 or normal mouse colon tissues, whereas it was expressed in human colon peritumoral and tumoral tissues at similar levels. No significant difference was observed between human tumors and peritumoral tissues for UDP-glucuronosyltransferase, beta-glucuronidase, sulfotransferase, and sulfatase. For murine colon tissues, the conjugation pathways (UDP-glucuronosyltransferase and sulfotransferase) were lower in colon adenocarcinoma Co38, whereas the converse was observed for the corresponding hydrolytic enzymes (beta-glucuronidase and sulfatase).(ABSTRACT TRUNCATED AT 400 WORDS)

Cytoplasmic accumulation of ditercalinium in rat hepatocytes and induction of mitochondrial damage.

Ditercalinium (NSC 335153), a 7H-pyridocarbazole dimer, is a bis-intercalating agent whose mechanism of action differs from that of other mono-intercalating compounds, such as ellipticine derivatives. After a Phase I clinical trial, where irreversible hepatotoxicity was the dose-limiting side-effect, we have reinvestigated the disposition of ditercalinium in rats after i.v. administration. Tissue distribution of the tritiumlabeled drug was studied during 5 weeks. The drug distributed very quickly into tissues, and accumulated mostly in liver and kidneys. A much slower clearance followed, with a half-life greater than 7 days. The present study raises the question of whether ditercalinium, a biscationic lipophilic agent, exerts a direct mitochondria interaction both in vitro and in vivo. Fluorescence microscopy on rat tissue cryosections, after drug administration, showed that the major cellular site of drug accumulation corresponds to mitochondria. The mitochondrial probe 3,3'-diethyloxadicarbocyanine confirmed the mitochondrial localization of ditercalinium. An identical fluorescent pattern was found in cultured rat hepatocytes. These fluorescent granulation patterns suggest mitochondrial damage. To further study cell alterations, ultrastructural changes in rat liver and kidneys were observed with selective mitochondrial damage while nuclei remained apparently normal. The same observations were made in rat hepatocyte cultures. Therefore, the accumulation of ditercalinium in tissues and, more particularly, in mitochondrial probably plays an important role in ditercalinium-induced toxicity.

Dose-dependent neurotoxicity of high-dose busulfan in children: a clinical and pharmacological study.

Busulfan is known to be neurotoxic in animals and humans, but its acute neurotoxicity remains poorly characterized in children. We report here a retrospective study of 123 children (median age, 6.5 years) receiving high-dose busulfan in combined chemotherapy before bone marrow transplantation for malignant solid tumors, brain tumors excluded. Busulfan was given p.o., every 6 hours for 16 doses over 4 days. Two total doses were consecutively used: 16 mg/kg, then 600 mg/m2. The dose calculation on the basis of body surface area results in higher doses in young children than in older patients (16 to 28 mg/kg). Ninety-six patients were not given anticonvulsive prophylaxis; 7 (7.5%) developed seizures during the 4 days of the busulfan course or within 24 h after the last dosing. When the total busulfan dose was taken into account, there was a significant difference in terms of neurotoxicity incidence among patients under 16 mg/kg (1 of 57, 1.7%) and patients under 600 mg/m2 (6 of 39, 15.4%) (P less than 0.02). Twenty-seven patients were given a 600-mg/m2 busulfan total dose with continuous i.v. infusion of clonazepam; none had any neurological symptoms. Busulfan levels were measured by a gas chromatographic-mass spectrometry assay in the plasma and cerebrospinal fluid of 9 children without central nervous system disease under 600 mg/m2 busulfan with clonazepam:busulfan cerebrospinal fluid:plasma ratio was 1.39. This was significantly different (P less than 0.02) from the cerebrospinal fluid:plasma ratio previously defined in children receiving a 16-mg/kg total dose of busulfan. This study shows that busulfan neurotoxicity is dose-dependent in children and efficiently prevented by clonazepam. A busulfan dose calculated on the basis of body surface area, resulting in higher doses in young children, was followed by increased neurotoxicity, close to neurotoxicity incidence observed in adults. Since plasma pharmacokinetic studies showed a faster busulfan clearance in children than in adults, this new dose may approximate more closely the adult systemic exposure obtained after the usual 16-mg/kg total dose, with potential inferences in terms of anticancer or myeloablative effects. The busulfan dose in children and infants undergoing bone marrow transplantation should be reconsidered on the basis of pharmacokinetic studies.

Active metabolism of arachidonic acid by Kaposi sarcoma cells cultured from lung biopsies (KS-3); identification by HPLC and MS/MS of the predominant metabolite secreted as the 11,12-epoxy-eicosatrienoic acid.

The development of long-term culture of AIDS-KS cells has allowed us to investigate further a possible vascular origin of Kaposi sarcoma. Taking into account the relative specificity of arachidonic acid (AA) metabolism according to cell type, the AA 'cascade' was analyzed in cultured KS-3 cells established from lung biopsies and compared to human umbilical venous endothelial (H-UVE) cells and human myometrial smooth muscle (H-MSM) cells, under basal conditions and after stimulation with vasoactive agents such as histamine or thrombin. Considering strictly the 'prostaglandin' profile given by RIAs, the metabolism of AA was closer, whilst not identical, to H-UVE than to H-MSM cells. However, evaluation of all the eicosanoids released from [3H]AA labeled KS-3 cells revealed that the predominant metabolite was not prostacyclin (PGI2), as suggested from PG RIAs, but an epoxy-eicosatrienoic acid (EET), identified as the 11, 12 isomer by HPLC and MS/MS. The synthesis of this EET is probably cytochrome P-450 monooxygenase dependent. Its potential role in the development of the KS tumor cells is under investigation.

Phase I and pharmacologic studies of the camptothecin analog irinotecan administered every 3 weeks in cancer patients.

PURPOSE: A phase I study was undertaken to determine the maximum-tolerated dose (MTD), principal toxicities, and pharmacokinetics of the novel topoisomerase I inhibitor irinotecan (CPT-11). PATIENTS AND METHODS: Sixty-four patients meeting standard phase I eligibility criteria were included (24 women, 40 men; median age, 51 years; primary sites: colon, head and neck, lung, pleura; 60 of 64 had been previously treated). Pharmacokinetics was determined by high-performance liquid chromatography (HPLC). RESULTS: One hundred ninety CPT-11 courses were administered as a 30-minute intravenous (IV) infusion every 3 weeks (100 to 750 mg/m2). Grade 3 to 4 nonhematologic toxicities included diarrhea (16%; three hospitalizations), nausea and vomiting (9%), asthenia (14%), alopecia (53%), elevation of hepatic transaminases (8%), and one case of skin toxicity. An acute cholinergic syndrome was observed during CPT-11 administration. Diarrhea appeared dose-limiting at 350 mg/m2, but this was circumvented by using a high-dose loperamide protocol that allowed dose escalation. Dose-dependent, reversible, noncumulative granulocytopenia was the dose-limiting toxicity (nadir, days 6 to 9; median recovery time, 5 days). Grade 3 to 4 anemia was observed in 9% of patients. One patient died during the study, 8 days after CPT-11 treatment. Two complete responses (cervix, 450 mg/m2; head and neck, 750 mg/m2) and six partial responses in fluorouracil (5-FU)-refractory colon cancer were observed (260 to 600 mg/m2). Pharmacokinetics of CPT-11 and active metabolite SN-38 were performed in 60 patients (94 courses). CPT-11 plasma disposition was bi- or triphasic, with a mean terminal half-life of 14.2 +/- 0.9 hours (mean +/- SEM). The mean volume of distribution (Vdss) was 157 +/- 8 L/m2, and total-body clearance was 15 +/- 1 L/m2/h. The CPT-11 area under the plasma concentration versus time curves (AUC) and SN-38 AUC increased linearly with dose. SN-38 plasma decay had an apparent half-life of 13.8 +/- 1.4 hours. Both CPT-11 and SN-38 AUCs correlated with nadir leukopenia and granulocytopenia, with grade 2 diarrhea, and with nausea and vomiting. CONCLUSION: The MTD of CPT-11 administered as a 30-minute IV infusion every 3 weeks is 600 mg/m2, with granulocytopenia being dose-limiting. At 350 mg/m2, diarrhea appeared dose-limiting, but high-dose loperamide reduced this toxicity and allowed dose escalation. For safety reasons, the recommended dose is presently 350 mg/m2 every 3 weeks; more experience must be gained to establish the feasibility of a higher dose in large multicentric phase II studies. However, when careful monitoring of gastrointestinal toxicities is possible, a higher dose of 500 mg/m2 could be recommended in good-risk patients. The activity of this agent in 5-FU-refractory colorectal carcinoma makes it unique and mandates expedited phase II testing.

Drug resistance mechanisms in chronic lymphocytic leukemia.

Peripheral blood samples from 18 patients with chronic lymphocytic leukemias (CLL) who were either untreated but who were later sensitive to chlorambucil (CLL S) or resistant to a combination containing doxorubicin, vincristine, cyclophosphamide and prednisone (CLL R) were studied for glutathione system, P-glycoprotein, PCNA and topoisomerase II expression. P-glycoprotein expression detected by an immunocytochemical technique using MRK 16 antibody was present at the same level in CLL S and CLL R. The percentage of cells positive for P-gp was below 5% in all samples tested. Topoisomerase IIalpha level was quantified by Western blot analysis. None of the 18 CLL samples had detectable topoisomerase IIalpha protein. In addition, 12 CLL were tested for PCNA staining and no samples had more than 1% of positive cells at immunocytochemical detection indicating that CLL cells were not engaged in the cell cycle. Some differences were found between CLL S and CLL R in the glutathione system. Glutathione concentration (GSH) and GST activity was the same in CLL S and CLL R. The glutathione-S-transferase (GST) isoenzyme profile was different in the two CLL groups. The mean GST-pi and GST-alpha quantitation were twice as high as in CLL R compared to CLL S, but this difference did not reach statistical significance because of large variations between CLL samples. A significant correlation was observed between GST-pi expression and GST activity using CDNB as the substrate. GST-mu was detected in only one of seven CLL before therapy and in six of 11 resistant to chemotherapy. No correlation was found between P-glycoprotein expression, GST activity and the different GST isoenzymes studied. These results suggest that the glutathione system could play a role in the resistance of anticancer agents in chronic lymphocytic leukemia. The role of the other drug resistance mechanisms (P-glycoprotein and topoisomerase IIalpha) seems to be of limited importance.

Metabolism of irinotecan (CPT-11) by CYP3A4 and CYP3A5 in humans.

7-Ethyl-10[4-(1-piperidino)-1-piperidino] carbonyloxy-camptothecin (CPT-11), a DNA topoisomerase I inhibitor, undergoes several metabolic pathways to generate conjugated and unconjugated derivatives that could be excreted from the body. The objective of this study was to determine the oxidative metabolites of CPT-11 recovered in human urine samples and to identify cytochrome P450 (CYP) involved in their formation. In addition to the already known metabolites of CPT-11 [SN-38, SN-38-G, 7-ethyl-10-[4-N-(5-aminopentanoic acid)-1-piperidino]carbonyloxycamptothecin (APC), and 7-ethyl-10-(4-amino-1-piperidino) carbonyloxycamptothecin (NPC)], we isolated three oxidized metabolites from the urine of two children and two adults given CPT-11. M1 and M2 (molecular weight, 602) were hydroxylated, respectively, on the CPT moiety and on the terminal piperidine ring of CPT-11. M3 had a molecular mass of 602, but its urine concentration in patients was too low to establish its chemical structure by liquid chromatography/mass spectrometry. In vitro incubations with cells expressing CYP2C8, CYP2C9, CYP1A1, CYP1A2, or CYP3A7 did not produce any detectable metabolites. Only CYP3A4 produced both APC and NPC, resulting from the oxidation of the piperidinylpiperidine side chain of CPT-11 along with metabolite M2. The metabolism of CPT-11 by CYP3A5 was markedly different because neither APC or NPC nor M2 was produced, whereas only one new metabolite, M4 (molecular weight, 558), was generated by de-ethylation of the CPT moiety. No previous study has reported the presence of the M4 metabolite. Production of APC, NPC, M2, and M4 was prevented by ketoconazole, a specific CYP3A inhibitor. The parameters of CPT-11 biotransformation into M2 and M4 were examined using cell lines expressing, respectively, with CYP3A4 and CYP3A5, indicating that CPT-11 is preferentially metabolized by CYP3A4. In conclusion, CYP3A plays a major role in the metabolism of CPT-11, with some differences of the metabolic profile exhibited by 3A4 and 3A5.

Activity of fotemustine in medulloblastoma and malignant glioma xenografts in relation to O6-alkylguanine-DNA alkyltransferase and alkylpurine-DNA N-glycosylase activity.

Fotemustine is a chloroethylnitrosourea with antitumor activity in disseminated melanoma and adult primary brain tumors. Because new drugs are required for the treatment of medulloblastoma in children, we evaluated the preclinical antitumor activity of fotemustine in four s.c. medulloblastoma xenografts, in comparison with 1,3-bis(2-chloroethyl)-1-nitrosourea (BCNU). Both drugs were administered as a single i.p. injection to nude mice bearing advanced-stage tumor. Fotemustine displayed significant antitumor activity in three of four medulloblastoma xenografts; two, IGRM34 and IGRM57, were highly sensitive, with 37 and 100% tumor-free survivors, respectively, more than 120 days after treatment at the highest nontoxic dose (50 mg/kg). Fotemustine was also highly active in a malignant glioma xenograft (IGRG88; five of six tumor-free survivors on day 177). Fotemustine proved to be significantly more active than BCNU in IGRM34 and the glioma xenograft IGRG88. The DNA repair protein O6-alkylguanine-DNA alkyltransferase (ATase) was detected in all tumor xenografts, ranging in activity from 6 to 892 fmol/mg protein. The high in vivo sensitivity to fotemustine and BCNU observed in three xenografts was clearly associated with a low ATase activity (> 20 fmol/mg), whereas the two poorly sensitive or refractory medulloblastoma xenografts showed high ATase activity (> 500 fmol/mg). Alkylpurine-DNA N-glycosylase activity was detected in all tumor xenografts but at levels ranging only from 513 to 1105 fmol/mg/h; no consistent relationship was found between alkylpurine-DNA N-glycosylase activity and the in vivo sensitivity to the two chloroethylnitrosoureas. The improved activity and tolerance of fotemustine in comparison with BCNU in pediatric medulloblastoma xenografts strongly support the clinical development of this agent in children with brain tumors, in which ATase should be examined as a potential prognostic indicator.

Inhibition of glioma cells in vitro and in vivo using a recombinant adenoviral vector containing an astrocyte-specific promoter.

Gene therapy using the herpes simplex virus thymidine kinase (HSV-TK) gene in combination with the drug ganciclovir (GCV) is a promising approach for the treatment of cancer-inducing gliomas, a tumor with a poor prognosis. In an attempt to limit the toxic effects on normal tissues, we constructed a recombinant adenoviral vector, Adgfa2TK, in which the HSV-TK gene is driven by the promoter for the gene encoding glial fibrillary acidic protein, an intermediate filament protein expressed primarily in astrocytes. Infection by Adgfa2TK of a glial cell line (C6) and a non-glial cell line (MDA-MB-231) revealed markedly increased expression of HSV-TK in glial cells as determined by Western blot. In comparison, high HSV-TK protein levels were produced in both cell lines after infection with a control virus, AdCMVTK, in which the constitutive cytomegalovirus viral promoter was used to direct HSV-TK expression. Infection of two glial cell lines (C6, U251) and two non-glial cell lines (HepG2, MDA-MB-231) with Adgfa2TK followed by GCV treatment revealed high toxicity in glial cell lines (50% growth inhibitory concentration: <2 microg/mL of GCV) with little or no toxicity (50% growth inhibitory concentration: >75 microg/mL) in the non-glial cell lines. In vivo, injection of Adgfa2TK into C6 tumors grown in nude mice followed by intraperitoneal GCV treatment significantly repressed tumor growth compared with the controls. Adgfa2TK may be useful for directing expression of the HSV-TK gene to gliomas.

Tumour necrosis factor-alpha plasma levels after flavone acetic acid administration in man and mouse.

Flavone acetic acid (FAA) is a synthetic flavonoid with a remarkable spectrum of anticancer activities in mouse tumours, but with no anticancer activity in humans. The mechanism of action of this drug is complex and involves a tumour vasculature action similar to the effects of tumour necrosis factor (TNF). To assess directly the role of TNF in FAA mechanism of action, this cytokine was assayed in both mouse and human plasma after intravenous administration of the drug. In mouse, a species particularly sensitive to FAA antitumour action, FAA plasma concentrations reached 268 micrograms/ml at 0.5 h and remained high (165 micrograms/ml) at 6 h following the intravenous administration of an anticancer efficacious dose (540 mg/m2). After FAA administration in mouse, TNF activity (L929 mouse cell bioassay) increased to 300 pg/ml TNF-alpha-equivalent at 2 h, reached a maximum concentration of 600 pg/ml at 4 h, and declined thereafter to 220 pg/ml at 6 h. TNF activity in mouse plasma was completely abrogated in the presence of mouse TNF-alpha antibodies. FAA added directly to blank mouse plasma did not show TNF activity. In patients receiving the drug as a 6-h intravenous infusion at doses ranging from 3.6 to 8.1 g/m2, FAA plasma levels ranged from 58 to 449 micrograms/ml at the end of infusion. Human TNF-alpha levels assayed with an immunoradiometric assay were either not detectable or very low (< 25 pg/ml) before FAA administration. At completion of the FAA infusion, TNF-alpha remained near background levels in 20 of the 21 courses. A slight increase in plasma TNF-alpha was observed in 1 patient at the 8.1 g/m2 dose level of FAA, from 13 pg/ml before intravenous infusion, to 70 pg/ml at completion of intravenous infusion. Taken together, these data demonstrate a marked interspecies difference with regard to TNF-alpha secretion after FAA treatment, as this cytokine is produced in mice, whereas it is not significantly secreted in pretreated patients. Although the low TNF-alpha levels achieved in mice probably do not explain all of FAA antitumour activity in that species, the observed interspecies difference in TNF-alpha secretion after FAA administration could partly explain the marked difference in FAA antitumour activity observed between mice and humans.

Phase I and pharmacokinetic study of brequinar (DUP 785; NSC 368390) in cancer patients.

Brequinar (DUP 785, NSC 368390) is a 4-quinoline carboxylic acid derivative with broad spectrum antitumour activity in experimental models that acts as an antimetabolite by specific inhibition of de novo pyrimidine synthesis. We performed a phase I study of brequinar administered as a 10 min intravenous (i.v.) infusion for 5 consecutive days, every 4 weeks. 67 evaluable patients were entered in this study and a total of 130 courses were administered at doses ranging from 2 to 350 mg/m2. The dose-limiting toxicity was myelosuppression with predominant thrombocytopenia. Myelosuppression was dose-related and non-cumulative, with considerable interpatient variability depending on haematological risk factors. The maximum tolerated dose of brequinar was 210 mg/m2/day in poor risk patients whereas patients with good risk haematological profile tolerated higher doses (up to 350 mg/m2/day). Other non-limiting toxicities included nausea and vomiting, mucositis and skin reactions. Brequinar plasma pharmacokinetic profiles were biphasic with alpha half-life ranging from 0.1 to 0.7 h, and beta half-life ranging from 1.5 to 8.2 h. Increase in brequinar area under the plasma concentration versus time curves (AUC) was nonlinear. Day 5 brequinar pharmacokinetics obtained in 21 patients indicated a significant increase in AUC (47%) and half-life beta (133%) compared to day 1 pharmacokinetics in the same patient. Brequinar plasma AUC and the per cent change in platelet count at nadir were correlated (P < 0.001). Although no objective response was observed in this study, one minor response was noted in cervical lymph nodes of a Hodgkin's disease patient.