Etanidazole Research Articles

Experimental study on the radiosensitization effect of etanidazole and paclitaxel on hepatocellular carcinoma H22 cells in mice

Objective To investigate the synergistic effect of etanidazole and paclitaxel on hepatocellular carcinoma H22 cells in mice. Methods To establish the murine xenografts, H22 cells was inoculated subcutaneously into the back of BALB/c mice. Among them, 40 tumor-bearing mice were divided into 4 groups by random number table method, 10 mice in each group, and each group injected with phosphate buffered saline (PBS), etanidazole (200 mg/kg), paclitaxel (1 mg/kg) and two drugs combination. Two hours after the administration, the mice were sacrificed by dislocation, and the drugs content in blood and tumor tissues of mice was measured by high-performance liquid chromatography. Sixty-five tumor-bearing mice were selected and divided into PBS non-irradiation group, PBS irradiation group, etanidazole irradiation group, paclitaxel irradiation group and two drugs combination irradiation group by random number table method, 13 mice/group. According to the grouping, the irradiated mice received 60Co source irradiation 2 hours after administration; the survival of 10 mice was observed at different time points, and the tumor volume was measured and calculated. The survival mice were killed by cervical dislocation 180 days after radiation. The other 3 mice in each group were killed after 2 days of irradiation, the tumor tissues were taken, and the expression of hypoxia inducible factor 1 (HIF-1) in these tumor tissues was detected by using immunohistochemistry. Statistical analysis of measurement data between groups was performed by using the one-way ANOVA and t test, and the survival analysis was made by Kaplan-Meier method. Results There was no significant difference of etanidazole and paclitaxel content in blood and tumor tissues between alone and combination administration groups at 2 hours after administration [etanidazole in blood: (55.5±4.7) μg/ml vs. (50.7±5.2) μg/ml; etanidazole in tumor: (31.2±3.5) μg/g vs. (33.6±5.4) μg/g; paclitaxel in blood: (316.9±9.6) μg/ml vs. (289.5±10.3) μg/ml; paclitaxel in tumor: (161.7±7.2) μg/g vs. (181.3±11.6) μg/g; all P > 0.05]. Within 40 days from the 10th day after the irradiation, the body weight of the irradiated group at each time point was significantly lower than that of the unirradiated group (all P 0.05). On the 40th day after irradiation, the tumor inhibition rates of the PBS irradiation group, etanidazole irradiation group, paclitaxel irradiation group, and two drugs combination irradiation group were 19.2%, 33.9%, 48.7%, and 61.6%, respectively. On the 180th day after irradiation, the survival rates of the PBS non-irradiation group, PBS irradiation group, etanidazole irradiation group, paclitaxel irradiation group, and two drugs combination irradiation group were 0, 0, 0, 12.5%, and 25.0%, respectively, and the median survival interval was 30.2, 54.7, 55.6, 83.4, and 102.8 d. After 2 days of irradiation, the positive expression rate of HIF-1 in the tumors tissues of PBS irradiation group, etanidazole irradiation group, paclitaxel irradiation group and two drugs combination irradiation group was lower than that in the PBS non-irradiation group, the differences were statistically significant [(45.7±4.8)%, (40.6 ±5.9)%, (24.5±5.6)%, (17.2±3.7%)% vs. (63.1±7.2)%, all P < 0.05]. The positive expression rate of HIF-1 in the paclitaxel irradiation group and two drugs combination irradiation group was lower than that in the PBS irradiation group and etanidazole irradiation group (all P < 0.05). Conclusion The combination of etanidazole and paclitaxel has synergistic radiation sensitization effect on hepatocellular carcinoma H22 cells in mice, and the expression level of HIF-1 is decreased, reflecting the decrease of hypoxic cells. Key words: Liver neoplasms; Mice; Etanidazole; Paclitaxel; Radiation tolerance

Voltammetry of hypoxic cells radiosensitizer etanidazole radical anion in water

Cytotoxic properties of radiosensitizers are due to the fact that, in the metabolic pathway, these compounds undergo one-electron reduction to generate radical anions. In this study we focused our interest on the electrochemical transfer of the first electron on radiosensitizer Etanidazole (ETN) and, consequently, on the ETN radical-anion formation in the buffered aqueous media. ETN was electrochemically treated in the broad pH range at various scan rates. Three reduction peaks and one oxidation peak were found. At strong alkaline pH the four-electron reduction peak was separated into one-electron and three-electron reductions. Under these conditions the standard rate constant k 0 for the redox couple ETN − NO 2 + e − ⇄ ETN − NO 2 •− was calculated. Moreover, the value of a so called E 7 1 potential that accounts for the energy necessary to transfer the first electron to an electroactive group at pH = 7 in aqueous medium to form a radical anion was also determined. The obtained value of E 7 1 indicates that lower energy compared to the other possible chemical radiosensitizers is necessary for the system to transfer the first electron to ETN. On the other hand, the necessity of the strong alkaline pH may decrease the ability of ETN to act as hypoxic radiosensitizer in the human body.

Impedance study of hypoxic cells radiosensitizer etanidazole radical anion in water

Electrochemical transfer of the first electron to cytotoxic radiosensitizer etanidazole (ETN) and ETN radical anion formation in the alkaline buffered aqueous solution were studied by means of electrochemical impedance spectroscopy (EIS). The heterogeneous electron transfer rate constant for the first reduction of ETN (radical anion production), k0, was calculated. The value of k0 from EIS measurements and the previously obtained value of so-called E71 potential indicate that ETN, compared with other possible chemical radiosensitizers, requires lower energy to accept the first electron during the metabolic pathway. However, the necessity of the alkaline pH may decrease the ability of ETN to act as hypoxic radiosensitizer in the human body.

Etanidazole in pH-sensitive liposomes: Design, characterization and in vitro/in vivo anti- Trypanosoma cruzi activity

In this work, the hydrophilic, low molecular weight and trypanocidal drug etanidazole (ETZ) was loaded in pH-sensitive liposomes (L-ETZ). Liposomes were made of dioleoyl-phosphatidylethanolamine: cholesteryl hemisuccinate (DOPE:CHEMS, 6:4, mol:mol), of 380 nm size at 14% ETZ/total lipid (w/w) ratio. To follow their uptake and intracellular fate by fluorescence microscopy, pH-sensitive liposomes were loaded with the fluorophore/quencher pair HPTS/DPX. A fast and massive delivery of the liposomal aqueous content into the cytosol of murine J774 macrophages was observed. L-ETZ vesicles were phagocytosed by both uninfected and Trypanosoma cruzi-infected macrophages. A 72% of anti-amastigote activity (AA) was demonstrated on L-ETZ-treated J774 cells, whereas the same dose of free ETZ rendered 0% AA. Endovenous administration of L-ETZ at 14 μg/mouse dose provoked significant decrease in parasitemia levels of T. cruzi-infected mice. Conversely, inoculation of a 180-fold higher dose of free ETZ failed in reducing the number of bloodstream trypomastigotes. Hence, these results point to develop systems, such as L-ETZ, designed for selective delivery of drugs to the cytoplasm of phagocytic cells, thus enhancing the efficacy of molecules considered poorly active.

In vitro activity of Etanidazole against the protozoan parasite Trypanosoma cruzi.

We investigated the in vitro action of an hydrosoluble 2-nitroimidazole, Etanidazole (EZL), against Trypanosoma cruzi, the etiologic agent of Chagas disease. EZL displayed lethal activity against isolated trypomastigotes as well as amastigotes of T. cruzi (RA strain) growing in Vero cells or J774 macrophages, without affecting host cell viability. Although not completely equivalent to Benznidazole (BZL), the reference drug for Chagas chemotherapy, EZL takes advantage in exerting its anti-T. cruzi activity for longer periods without serious toxic side effects, as those recorded in BZL-treated patients. Our present results encourage further experiments to study in depth the trypanocidal properties of this drug already licensed for use in human cancers.

Survival Results from a Phase I Study of Etanidazole (SR2508) and Radiotherapy in Patients with Malignant Glioma

Purpose: To report the survival results from a previous Phase I study of etanidazole (ETA) and radiotherapy in patients with glioblastoma multiforme (GBM n = 50) or anaplastic astrocytoma (AA n = 19) and examine survival according to age, Karnofsky performance status (KPS), and implant status. Patients and Methods: In a previous Phase I study, 70 previously untreated patients (median age 49) with malignant gliomas were accrued. One patient was excluded from analysis because pathology was unverifiable. All had KPS ≥ 70. Prior to initiation of treatment, patients were stratified according to whether they were candidates for interstitial implantation. The implant patients (IMP n = 14) received accelerated fractionation radiotherapy (XRT) 2 Gy BID (6 hours apart) to 40 Gy in 2 weeks with ETA 2 gm/m 2 × 6 doses, a 2 week break, and then interstitial implant for an additional 50 Gy (4–7 days) with a continuous infusion of ETA over 90–96 hours. There were 55 patients treated on two sequentially conducted non-implant arms. These patients started with accelerated fractionation XRT 2 Gy BID (6 hours apart) to 40 Gy in 2 weeks with ETA 2 gm/m 2 × 4–5 doses/week. Non-IMP1 arm (n = 41) received a 2-week break before standard fractionated boost XRT of 2 Gy/day for 2 weeks to a total dose of 60 Gy with ETA. Non-IMP2 arm (n = 14) did not have the 2-week break. All patients had plasma pharmacokinetic monitoring of ETA. Subsequent follow-up study provided information regarding long-term survival status of this group of patients. The Phase I toxicity evaluation was conducted according to the RTOG toxicity scale and was found well tolerated in both groups. Overall actuarial survival was plotted for all patients, by histologic group, and by implant status. Subset analyses of GBM patients by age (≤ 49 or > 49 years), KPS (≤ 80 or > 80) and implant versus non-implant were also performed. Results: Median survival of GBM patients was 1.1 years and that of anaplastic astrocytoma patients was 3.1 years ( p = 0.0001). In GBM patients, KPS > 80, implanted patients, and age ≤ 49 were factors found not to be associated with a statistically improved survival. Conclusion: The results of survival in this Phase I etanidazole study of patients with anaplastic astrocytoma are comparable to the results from other studies using bromodeoxyuridine, iododeoxyuridine, or procarbazine, lomustine (CCNU), and vincristine. The use of etanidazole with accelerated radiotherapy does not appear to improve survival in patients with glioblastoma multiforme compared to those treated with conventional therapies.

Results of an RTOG phase III trial (RTOG 85-27) comparing radiotherapy plus etanidazole with radiotherapy alone for locally advanced head and neck carcinomas

The objectives of this study were to determine the efficacy and toxicity of Etanidazole (ETA), a hypoxic cell sensitizer, when combined with conventional radiotherapy (RT) in the management of advanced head and neck carcinomas. From March 1988 to September 1991, 521 patients who had Stage III or IV head and neck carcinomas were randomized to receive conventional RT alone (66 Gy in 33 fractions to 74 Gy in 37 fractions, 5 fractions per week) or RT+ETA (2.0 g/m2 thrice weekly for 17 doses), of whom 504 were eligible and analyzable. Treatment assignments were stratified before randomization according to the primary site (oral cavity + hypopharynx vs. supraglottic larynx + oropharynx + nasopharynx), T-stage (T1-3 vs. T4), and N-stage (N0-2 vs. N3). Pretreatment characteristics were balanced. In the RT-alone arm, 39% of patients had T3 and 34% had T4 disease, whereas in the RT+ETA arm, 42% of patients had T3 and 33% had T4 disease. Thirty-eight percent of the RT-alone patients and 37% of the RT+ETA patients had N3 disease. The median follow-up of surviving patients was 3.38 years, with a range between 0.96 and 5.63 years. One hundred and ninety-four of the 252 (77%) RT+ETA patients received at least 14 doses of the drug. Overall RT protocol compliance rate was 82% in the RT-alone arm and 86% in the RT+ETA arm. No Grade 3 or 4 central nervous system or peripheral neuropathy was observed in the RT+ETA arm. Eighteen percent of the patients developed Grade 1 and 5% developed Grade 2 peripheral neuropathy. Other drug related toxicities included nausea/vomiting (27%), low blood counts (15%), and allergy (9%). Most of these toxicities were Grade 1 and 2. The incidence of severe acute and late radiation effects were similar between the two arms. The 2-year actuarial local-regional control rate (LCR) was 40% for the RT-alone arm and 40% for the RT+ETA arm. Two-year actuarial survival was 41% for the RT-alone arm and 43% for the RT+ETA arm (p = 0.65). Multivariate analyses were performed to investigate the influence of covariates on treatment effects. A strong treatment interaction with N-stage was revealed: LCR (50% vs. 40% at 2 years), RT+ETA improved for patients with N0-2 disease but not for N3 patients (22% for RT+ETA and 40% for RT). Further analyses showed that RT+ETA was more advantageous in N0-1 patients, with a 2-year LCR of 55% for RT+ETA vs. 37% for RT only (p = 0.03). A similar phenomenon was observed when using survival as the end point. The results showed that adding Etanidazole to conventional RT produced no global benefit for patients who had advanced head and neck carcinomas. There was a suggested benefit for patients who had N0-1 disease, and that needs to be confirmed by another study.

A phase I study of etanidazole and radiotherapy in malignant glioma

Purpose : To determine the maximum tolerable total dose (MTD) of etanidazole (ETA) when administered with external beam radiotherapy (XRT) and as a continuous infusion during stereotactic brachytherapy for patients with malignant glioma (anaplastic astrocytoma or glioblastoma multiforme or mixed cell tumors). Methods and Materials : Seventy previously untreated patients were entered in a Phase I study. Prior to initiation of treatment, patients were stratified according to whether or not they were candidates for interstitial implantation. The implant patients (IMP, n = 17 pt) received accelerated fractionation XRT 20 Gy BID (6 h apart) to 40 Gy in 2 weeks with ETA 2 gm/m 2 × 6 doses, a 2 week break and then interstitial implant to 50 Gy (4–7 days) with a continuous infusion of ETA over 90–96 h. The two sequentially conducted nonimplant arms started with accelerated fractionation XRT 2 Gy BID (6 h apart) to 40 Gy in 2 weeks with ETA 2 gm/m 2 × 4–5 doses/week. NonIMP 1 arm ( n = 38) received a 2-week break before standard fractionated boost XRT of 20 Gy/day for 2 weeks to a total dose of 60 Gy with ETA. NonIMP 2 arm ( n = 14) did not have the 2-week break. All patients had plasma pharmacokinetic monitoring of ETA. Results : The dose-limiting toxicity (DLT) in the IMP group was the cramping/arthralgia syndrome (4) and the cumulative MTD was 26 gm/m 2. For both nonIMP 1 and 2 the DLTs were peripheral neuropathy and the cramping-arthralgia syndrome. The MTD for nonIMP 1 was 34 gm/m 2 and nonIMP 2, 30 gm/m 2. Conclusion : The clinical efficacy and radiation-related toxicity of these regimens are being evaluated. The doses of ETA that can be used with accelerated fractionation and with external beam irradiation plus brachytherapy have been established.

Phase II trial of external beam radiation with etanidazole (SR 2508) for the treatment of locally advanced prostate cancer

Purpose : To evaluate the efficacy and toxicity of the addition of etanidazole (ETA) to external beam radiation. Methods and Materials : Fifty eight previously untreated patients with locally advanced adenocarcinoma of the prostate were entered on a Phase II trial of etanidazole (ETA) combined with standard external beam radiation therapy. ETA was given concurrently with irradiation. Four patients received less than 25% of the intended dose of ETA and were ineligible for further analysis. The stage of the remaining patients were T 2c-11, T 3–39, T 4-1, bulky local recurrence after prostatectomy-1, and T 3, N 1–2. Results : Forty-five of 54 patients (83.3%) achieved a clinical complete response (CCR) in the prostate and seminal vesicles as judged by digital rectal exam (DRE). Responses were rapid with a median time to CCR of 3.4 months, range 0–22.8 months. Local control was maintained in 82% of the patients who achieved a CCR. Fifteen of 32 eligible patients with a normal DRE underwent prostate biopsies from 12–20 months after treatment, seven had negative biopsies (46.6%). Distant metastases occurred in 18 patients (33.3%). Pretreatment prostatic specific antigen (PSA), Gleason score, and stage were not associated with treatment outcome in a univariate analysis. Conclusion : While ETA plus radiation was associated with a rapid CCR, the overall treatment outcome of these patients appeared to be similar to published reports of patients receiving RT alone. The rapid response rate may imply biologic activity of the ETA. In future trials, it may be reasonable to focus on patients at lower risk for the subsequent development of distant disease.

Metabolic studies and neurotoxicity in tumors and brain of mice after hypoxic cell sensitizers

Purpose : The effects of the radiosensitizers RK-28 and RP-170, both 2-nitroimidazole nucleoside analogues, and KU-2285, a fluorinated 2-nitroimidazole, as well as etanidazole (ETA) on glucose metabolism in mouse tumors and brain were studied to assess their degree of neurotoxicity. Methods and Materials : Adult male C57Bl mice received differing doses of the above sensitizers IP. Blood, brain, and tumor samples were removed at various times and the levels of glycolytic metabolites determined. Glucose uptake and phosphorylation in brain was measured by the 2-deoxyglucose method of Sokoloff et al. (6). Results : RP-170 showed neither signs of toxicity nor significant alterations in glucose metabolism in brain or tumor at doses up to 4 g/kg b.w. up to 4 h. By contrast, RK-28 was extremely neurotoxic at a dose of 1 g/kg b.w. with a high degree of lethality, resulting in a highly significant increase in the brain glucose level from 0.38 μmol/g to 2.20 μmol/g ( p < 0.001) 2 h after administration, whereas that in the tumor was decreased. KU-2285 and ETA were significantly ( p < 0.01) less toxic than RK-28 at this dose, as reflected in a lower increase in the brain glucose level (0.60 gmol/g), although KU-2285 approached that of RK-28 (1.43 μmol/g; p < 0.01) after 2 h following a dose of 2 g/kg b.w. However, in contrast to the other sensitizers, KU-2285 concomitantly also resulted in a highly significant continuous increase ( p < 0.01) in tumor glucose levels. Labeled 3H-2-deoxyglucose studies showed that RP-170 neither markedly affected the uptake of total radioactivity into the brain nor its degree of phosphorylation whereas, KU-2285 (2 g/kg) and RK-28 (1 g/kg) decreased uptake by ∼ 50% and phosphorylation approximately 3 and 4-fold, respectively. At doses of 1 g/kg, ETA and KU-2285 showed no significant changes in these parameters. This indicates a decreased level of neurotoxicity. Conclusion : Since the adult brain relies solely on glucose metabolism for its energy supply, interference to this pathway may be instrumental in the development of neurotoxicity, thus, underlining the need for such metabolic studies to assess the level of toxicity by radiosensitizers.

Relationship between Intracellular Concentration and Radiosensitizing Effect of Pimonidazole and Etanidazole on Two Human Melanoma Cell Lines

A study on the uptake and radiosensitizing properties of pimonidazole (PIMO) and etanidazole (ETA) was made in vitro with two melanoma cell lines: Na11+ and Na11-. The amelanotic Na11- was derived from the pigmented Na11+ cell line and was characterized by the complete absence of pigmentation in vitro. Plateau-phase cells were heavily pigmented for the Na11+ line whereas exponential cells showed a lower melanin content. Radiosensitivity was studied using an in vitro colony assay; intracellular drug concentration was determined by HPLC. For both cell lines the uptake of PIMO was always higher than the uptake of ETA, and slightly higher in hypoxia than in air. The uptake of PIMO was exceptionally high in plateau-phase cells of the pigmented Na11+ cell line. The radiosensitizing effect of ETA did not differ greatly as a function of the cell kinetics in both cell lines, whereas the radiosensitizing effect of PIMO was cell line-dependent. Sensitization of exponential cells by PIMO was similar in both cell lines but significantly less in plateau-phase cells, with the heavily pigmented Na11+ cell line being least affected, despite a three-fold increase in PIMO uptake observed in plateau cells relative to exponentially growing Na11+ cells. The uptake of PIMO may be related to the high melanin content of plateau-phase Na11+ cells and therefore this in vitro model may be useful for predicting the effects of agents such as PIMO towards melanotic melanomas in vivo.

Protection against Light-Activated Photofrin II Killing of Tumor Cells by Nitroimidazoles

Nitroimidazoles are good quenchers of triplet state porphyrins in chemical systems, thereby inhibiting singlet oxygen formation and type II photodynamic reactions. Photobiological studies were performed with EMT-6 tumor cells in vitro utilizing Photofrin II (PII) in combination with etanidazole (ETAN), misonidazole (MISO), and trifluoromisonidazole (TF-MISO). After short-term (1 h) exposure of cells to PII, 5 mM ETAN and MISO had no effect on photoinactivation while 5 mM TF-MISO had a small but significant protective effect. When the intracellular oxygen level was equilibrated with 0.3% oxygen in the gas phase, all three nitroimidazoles produced significant photoprotection at concentrations as low as 0.3 microM. After long-term (24 h) exposure of cells to PII, all three nitroimidazoles demonstrated large photoprotective effects under both aerobic and 0.3% oxygen conditions. At equal concentrations of nitroimidazole, photoprotection was greatest for the most lipophilic compound (TF-MISO) and least effective for the most hydrophilic compound (ETAN). These studies suggest that nitroimidazoles can quench triplet state porphyrins (within cells) to reduce intracellular concentrations of singlet oxygen, the putative toxin in PII photoinactivation. In addition, after long-term exposures to PII when porphyrins have partitioned into cellular membranes and lipid environments, the lipophilicity of this class of photoprotector correlates with effectiveness in these mammalian cells.

The efficacy of pharmacokinetic monitoring and dose modification of etanidazole on the incidence of neurotoxicity: Results from a phase II trial of etanidazole and radiation therapy in locally advanced prostate cancer

Fifty-four patients have been entered on a Phase II trial to study the efficacy of etanidazole (ETA) for locally advanced prostate cancer. The primary goal was to study the incidence of and time to a complete response for patients receiving ETA and radiation therapy. The secondary goal was to prospectively evaluate the utility of pharmacokinetic monitoring and dose-modification on the incidence and severity of the dose-limiting peripheral neurotoxicity. Within a constant radiation therapy regimen, the dose of ETA was either (a) unmodified (2 g/m 2, 3 times weekly for 17 doses); (b) altered by a schedule modification of either number of doses or dose adjustment; or (c) individualization of single dose size so that the total number of doses (19 doses) were maintained but the single dose size was adjusted to keep the total AUC of plasma concentration versus time to < 40 mM-hr. Sufficient efficacy data are not yet available. The use of drug dose modification has reduced the incidence of neurotoxicity from (a) unmodified: 17 26 = 65% (1 grade II); (b) schedule adjustment: 5 9 = 55% (no grade II); and (c) individualized dose modification: 1 19 ( no grade II) = 6% . The minimum number of time points needed to accurately assess the AUC will be determined. Pharmacokinetic monitoring will be important in the use of ETA so that drug underdosing can be avoided while minimizing the risk of serious neurotoxicity.

A phase I pilot study to evaluate intraoperative radiation therapy (IORT) and the hypoxic cell sensitizer etanidazole (ETA) in patients with locally advanced malignancies (RTOG protocol 89-06)

A phase I pilot study to evaluate intraoperative radiation therapy (IORT) and the hypoxic cell sensitizer etanidazole (ETA) in patients with locally advanced malignancies (RTOG protocol 89-06)

Combination of etanidazole with cyclophosphamide and platinum complexes

In an effort to improve the therapeutic efficacy and selectivity of cyclophosphamide (CTX), cis-diamminedichloroplatinum(II) (CDDP), and carboplatin (Carbo), these antitumor alkylating agents were combined with the 2-nitroimidazole drug etanidazole (ETA). As revealed by tumor-cell survival assay in the FSaIIC murine fibrosarcoma, the addition of ETA (1 g/kg, i.p.) just prior to the i.p. injection of various doses of the alkylating agents resulted in increases in the tumor-cell kill produced by each drug (CTX, 10-fold; CDDP, 20-fold; and Carbo, 5- to 15-fold), whereas toxicity to bone marrow granulocyte-macrophage colony-forming units (CFU-GM) increased only about 0- to 3-fold. When CTX was combined with either CDDP or Carbo, striking increases in tumor-cell killing were observed (20- to 100-fold across the CDDP dose range and 5- to 20-fold across the dose range of Carbo), which were supra-additive for CDDP and additive for Carbo as revealed by isobologram analysis. The addition of ETA to these alkylating-agent combinations produced a further approx. 20-fold increase in tumor-cell kill for both CTX/CDDP and CTX/Carbo. This effect was greatest at the lowest dose of the platinum drug tested and was supra-additive in the case of CDDP and additive for Carbo. Following treatment with ETA/CTX/CDDP, bone marrow CFU-GM toxicity increased only about 5-fold over that of CTX/CDDP alone, but the injection of ETA/CTX/Carbo resulted in a 10- to 20-fold increase in bone marrow toxicity as compared with that obtained using CTX/Carbo alone. Tumor growth-delay studies revealed significant increases in the antitumor effect of the alkylating agents when these were given in combination with ETA. Both the ETA/CTX/CDDP and the ETA/CTX/Carbo combinations produced tumor growth delays of 23 days, which represented approx. 1.6-fold increases over those obtained using the alkylating-agent combinations alone. These results suggest that ETA could significantly improve the therapeutic efficacy of these alkylating agents, whether they are given individually or in combination.

Schedule dependent tumour growth delay, DNA cross-linking and pharmacokinetic parameters in target tissues withcis-diamminedichloroplatinum(II) and etanidazole with or without hyperthermia or radiation

It has been reported previously that striking increases in tumour growth delay and cytotoxicity are seen when cis-diamminedichloroplatinum(II) (CDDP) is combined with mild local hyperthermia (43 degrees C, 30 min) and/or etanidazole (ETA). This paper reports a study of CDDP pharmacology and the in vivo tumour DNA cross-linking produced by these combinations. In C3H mice bearing the FSaIIC murine fibrosarcoma, Pt plasma pharmacokinetics were not significantly altered by any of the combination of treatments. Although ETA caused no significant change in CDDP tissue pharmacokinetics, treatment of the tumour-bearing limb with hyperthermia immediately following an i.p. injection of CDDP (10 mg/kg) resulted in an increased peak Pt concentration (3.5 versus 2.8 micrograms Pt/g tumour wet weight) and doubled the t1/2 elimination of Pt (15 to 30 h) from the tumour. Similar heat-induced changes were observed in the Pt pharmacokinetics in skin. There was about a three-fold increase in the Pt area under the curve (AUC) for the tumour, a 1.5-fold increase in the AUC for skin and little change in the AUC for muscle with hyperthermia. When the tumour DNA cross-linking factor (CLF) was determined, it was found that local hyperthermia treatment (43 degrees C, 30 min) increased the CLF of CDDP from 1.7 to 2.7 and hyperthermia (43 degrees C, 1 h) further increased the CLF to 6.1. Misonidazole (MISO) (1 g/kg) increased the CDDP CLF to 2.0, 6.3 and 15.1 in conjunction with 37, 43 (30 min) and 43 degrees C (1 h), respectively. ETA (1 g/kg) was more effective than MISO at increasing the CDDP CLF, producing CLFs of 2.8, 9.1 and 21.5 at 37, 43 (30 min) and 43 degrees C (1 h), respectively. These changes in CLF were reflected in an increased tumour growth delay in the FSaIIC murine fibrosarcoma with CDDP (5 mg/kg) alone from 4.4 to 5.9 days with 43 degrees C (30 min) and then to 11.9 days with ETA (1 g/kg) and 20.9 days with both ETA and local hyperthermia (43 degrees C, 30 min). When CDDP, ETA and hyperthermia were added to a radiation schedule of 300 cGy daily for five days, it was found that giving ETA (1 g/kg), CDDP (5 mg/kg) and hyperthermia (43 degrees C, 30 min) together on day 1 produced the largest tumour growth delay (43 days) and that other schedules which divided the dose of ETA over the other days of the radiation treatment (including one schedule with a second heat treatment on day 4) were significantly inferior.(ABSTRACT TRUNCATED AT 400 WORDS)