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At least 19 recordsLinked to original sources
PubMed1992

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 of 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/m2, 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 less than 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.

Adenocarcinoma↗
PubMed1994

Phase I pharmacokinetic study of the hypoxic cell sensitizer etanidazole with carboplatin and cyclophosphamide in the treatment of advanced ovarian cancer.

PURPOSE: A Phase I study was undertaken to determine the maximum tolerated dose of the hypoxic cell sensitizer etanidazole which could be administered with carboplatin and cyclophosphamide, to determine whether adequate serum levels of etanidazole were achieved to allow for alkylating agent sensitization, and whether pretreatment with etanidazole altered carboplatin pharmacokinetics. METHODS AND MATERIALS: Patients received 2 g/m2 of intravenous etanidazole followed by a second dose of 4 g/m2 90 min later, followed by intravenous carboplatin (300 mg/m2) and cyclophosphamide (600 mg/m2) for four treatment cycles. Patients received an additional two cycles of carboplatin and cyclophosphamide without etanidazole. RESULTS: Two patients who received a total of 24 g/m2 of etanidazole developed Grade 1 neurotoxicity, and therefore etanidazole doses were not escalated further. The grade of granulocytopenia was worse after cycles with etanidazole than after those without (p = 0.03), but clinical outcome was not different. Etanidazole levels were adequate for alkylating agent sensitization (> 70 ug/ml) in all patients for the majority of the 7 h of testing. Pharmacokinetic data suggested t1/2 alpha and t1/2 beta for carboplatin were prolonged after pretreatment with etanidazole. CONCLUSION: Etanidazole, 2 g/m2 followed by 4 g/m2 90 min later, is safe and results in adequate serum levels for alkylating agent sensitization. Neurotoxicity appears to prevent dose escalation of etanidazole, and an interaction between etanidazole and carboplatin may have enhanced neurotoxicity in these patients.

Antineoplastic Combined Chemotherapy Protocols↗
PubMed1991

Technique, pharmacokinetics, toxicity, and efficacy of intratumoral etanidazole and radiotherapy for treatment of spontaneous feline oral squamous cell carcinoma.

The histologic appearance, locoregional recurrence, and rate/site of metastases of spontaneous feline oral squamous cell carcinoma are similar to head and neck cancer in humans. A feasibility study of intratumoral Etanidazole, a hypoxic cell sensitizer, and radiation therapy were instituted in this model. Eleven cats with feline squamous cell carcinoma were treated with intratumoral Etanidazole and radiation therapy. Total Etanidazole doses were 1.5-24.0 gms/m2 (0.5-6.9 gms). The tumor partial response rate was 100% (11/11); the median volume regression was 70%. All cats have died as a result of tumor recurrence or tumor-related complications. Median survival was 116 days. Ten cats have been autopsied. Non-necrotic and necrotic tumor cells were identified at the treatment site in all cats. Pharmacokinetic studies were performed in six cats. Following intravenous infusion, the plasma elimination of the Etanidazole was biexponential. The systemic availability following intratumoral administration was 61.2 +/- 21.1%. Peak plasma Etanidazole levels were observed 14 minutes following intratumoral injection, after which elimination was biexponential. Thirty minutes following intratumoral Etanidazole administration, tumor Etanidazole levels were 62.8% of plasma levels. Feline squamous cell carcinoma appears to be a useful model of human head and neck cancer. Cats tolerate substantial doses of intratumoral and intravenous Etanidazole. Etanidazole and radiation therapy cause rapid regression, but not cure, of feline squamous cell carcinoma. There is a similarity between the intravenous kinetics of Etanidazole in humans and cats. Further studies in this model are planned.

Animals↗
PubMed1996

Solubility behavior, phase transition, and structure-based nucleation inhibition of etanidazole in aqueous solutions.

PURPOSE: The solubility behavior, phase transition and inhibition of the nucleation process of etanidazole were characterized. METHODS: Solubility measurements as a function of time permitted characterization of the solubility behavior and phase transition. The precipitate from saturated solutions was isolated and characterized by differential scanning calorimetry, polarized light microscopy, x-ray powder diffraction and coulometric analysis. The physical stability of metastable systems was examined in the presence of various structure-based nucleation inhibitors. RESULTS: Etanidazole is soluble in water with an equilibrium solubility of 68.1 mg/mL, pH 6.5 with changes in pH having virtually no effect on the solubility. Etanidazole reaches concentrations in excess of 150 mg/mL within one hour. Etanidazole solutions prepared at 150 mg/ mL contained crystals after rotating for 24 hours. The crystals were isolated and characterized as etanidazole monohydrate. the solubility of etanidazole monohydrate in water increased with time reaching an equilibrium solubility of 68 mg/mL after 24 hours. Therefore, the solubility studies were actually determining the solubility of the more stable monohydrate from of etanidazole. Etanidazole solutions at concentrations of 50, 100 and 150 mg/mL were stabilized to varying degrees with structure-based nucleation inhibitors (imidazole, ethanolamine or diethanolamine). CONCLUSIONS: Anhydrous etanidazole undergoes a transition in aqueous solutions to the more stable monohydrate when the solubility of the monohydrate is exceeded. The physical stability of etanidazole solutions at 4 degrees C is improved following autoclaving. The addition of structure-based nucleation inhibitors effectively stabilized the metastable systems.

Calorimetry, Differential Scanning↗
PubMed1991

Effect of pH, oxygenation, and temperature on the cytotoxicity and radiosensitization by etanidazole.

The effect of etanidazole was examined in vitro and in vivo in the FSaIIC tumor system. At pH 7.40 and 37 degrees C, etanidazole at 5-500 microM for 1 hr was minimally cytotoxic. At 42 degrees C and 43 degrees C, however, the cytotoxicity of etanidazole increased. Etanidazole was more cytotoxic at pH 6.45 and 37 degrees than at pH 7.40 by about 1 log. Increasing the temperature to 42 degrees C or 43 degrees C at pH 6.45 during drug exposure, however, caused little increase in drug killing above the lethality of hyperthermia. When the radiosensitizing abilities of etanidazole were tested in vitro, there was a radiation dose modifying factor of 2.40 at pH 7.40, but only 1.70 at pH 6.45. In vivo, etanidazole (1 g/kg) produced a radiation dose modifying factor of 1.47, whereas 43 degrees C for 30 min produced a radiation dose modifying factor of 1.38. The combination resulted in a radiation dose modifying factor of 2.29. When the cytotoxicities of hyperthermia (43 degrees C x 30 min), etanidazole (500 mg/kg or 1 mg/kg), and radiation (10 Gy) combinations were assayed by Hoechst 33342 dye selected tumor subpopulations, 43 degrees C x 30 min increased the killing of irradiated dim cells by approximately 9.2-fold but by only 2.9-fold in bright cells. Etanidazole (1 g/kg) increased radiation killing of bright cells by about 3-fold and dim cells by about 4.3-fold. The combination of hyperthermia and etanidazole increased the killing of both dim and bright cells exposed to radiation by approximately 10-fold versus 10 Gy alone.

Animals↗
PubMed1992

Distribution of etanidazole into human brain tumors: implications for treating high grade gliomas.

Etanidazole was developed as an oxygen-mimetic radiosensitizer less lipophilic than misonidazole. Sensitization depends on an adequate concentration of drug in the tumor at the time of irradiation. Therefore, due to the presence of the blood-brain barrier, brain tumors may theoretically be difficult to radiosensitize due to the hydrophilic characteristics of etanidazole. Based on previous reports of loss of BBB integrity in brain tumors, we investigated the ability of etanidazole to penetrate into malignant gliomas of patients receiving etanidazole as part of a Phase I continuous infusion protocol. The patients had completed previous external beam irradiation. Twenty-two patients were studied and their etanidazole plasma and biopsy data were compared to the 2-compartment model derived from a second group of 19 patients with bolus etanidazole. Etanidazole concentration in brain tumor biopsies varied widely and appeared to be clustered into a higher and a lower pharmacokinetic group having mean tumor to well-perfused second compartment ratios of 1 and 0.25, respectively. Both high and low etanidazole concentrations were evident in different biopsies obtained from the same patient. Correlations between histology and tissue concentrations suggested that the higher level correspond to malignant tissue. These data indicate that the blood brain barrier is disrupted to varying degrees by the brain tumor and/or prior irradiation and that etanidazole penetrates into brain tumors.

Brain Neoplasms↗
PubMed1994

Modification of the aerobic cytotoxicity of etanidazole.

PURPOSE: To determine the feasibility of modifying the aerobic cytotoxicity of etanidazole without interfering with the tumoricidal action of radiation plus etanidazole. METHODS AND MATERIALS: The aerobic cytotoxicity of etanidazole was studied using two different models: (1) Induction of apoptosis in EL4 cells: apoptotic DNA fragmentation was analyzed by agarose gel electrophoresis following 24 h treatment with etanidazole alone or in combination with various modifiers. (2) Spinal cord neuronal loss in organotypic roller tube cultures: Survival of acetylcholinesterase positive ventral horn neurons was analyzed morphometrically following 72 h treatment with etanidazole alone or in combination with vitamin E succinate. RESULTS: Etanidazole (10 mM) induced apoptosis in EL4 cells. This effect was suppressed by 24 h treatment with TPA, IBMX, the free radical scavenger TEMPOL or vitamin E succinate. Vitamin E succinate also protected spinal cord cultures from etanidazole-induced neuronal loss. CONCLUSION: These results suggest that it might be possible to modify the neurotoxicity of etanidazole with agents that would not be expected to interfere with the tumoricidal action of radiation plus etanidazole.

Aerobiosis↗
PubMed1994

Use of the hypoxic cell sensitizer etanidazole (SR-2508) with intravenous melphalan and prednisone in the treatment of multiple myeloma: a pharmacokinetic study.

PURPOSE: A study was undertaken adding the alkylating agent sensitizer etanidazole to intravenous melphalan and oral prednisone for patients with multiple myeloma. This study explored the toxicity profile of these agents when given together and assessed the ability to attain adequate serum levels of etanidazole to permit sensitization to occur. METHODS AND MATERIALS: Etanidazole was administered intravenously in two doses of 3 g/m2 and 5 g/m2 90 min apart immediately prior to the administration of intravenous melphalan and oral prednisone for three consecutive cycles (total dose 24 g/m2). Patients received three additional cycles without etanidazole, allowing a comparison of hematologic toxicity from melphalan with and without etanidazole. RESULTS: Hematologic toxicity was moderate (Grade 3 or 4), but severity was similar during cycles with and without etanidazole. Only one patient developed a Grade 1 peripheral neuropathy questionably related to etanidazole. Most patients had etanidazole levels of > or = 70 ug/ml for 7 h, a level felt to be necessary for sensitization to occur. CONCLUSION: Etanidazole, administered as described, results in adequate serum levels for potential alkylating agent sensitization, without significant toxicity.

Antineoplastic Combined Chemotherapy Protocols↗
PubMed1997

Results of a European randomized trial of Etanidazole combined with radiotherapy in head and neck carcinomas.

PURPOSE: The aim of the study was to evaluate the efficacy and toxicity of Etanidazole, a hypoxic cell sensitizer, combined with radiotherapy in the treatment of head and neck squamous cell carcinoma. METHODS AND MATERIALS: A total of 374 patients from 27 European centers were included in this trial between 1987 and 1990. Treatment was either conventional radiotherapy alone (between 66 Gy in 33 fractions and 74 Gy in 37 fractions, 5 fractions per week), or the same radiotherapy dose plus Etanidazole 2 g/m2, three times weekly for 17 doses. A minimization procedure, balancing for center, site, and T stage (T1-T3 vs. T4) was used for randomization. RESULTS: Among the 187 patients in the Etanidazole group, 82% received at least 14 doses of the drug. Compliance to the radiotherapy protocol was 92% in the Etanidazole group and 88% in the control group; the main cause of deviation was acute toxicity, which was observed at an equal rate in the two treatment groups. Fifty-two cases of Grade 1 to 3 peripheral neuropathy were observed in the Etanidazole group vs. 5 cases, all of Grade 1, in the control group (p < 0.001). The 2-year actuarial loco-regional control rates were 53% in the Etanidazole group and 53% in the control group (p = 0.93), and the overall 2-year survival rates were 54% in each group (p = 0.99). CONCLUSION: Adding Etanidazole to conventional radiotherapy did not afford any benefit for patients with head and neck carcinoma. This study failed to confirm the hypothesis of a benefit for patients with N0-N1 disease, which had been suggested by the results of a previous study (10).

Adult↗
PubMed1998

Intervention with the hypoxic tumor cell sensitizer etanidazole in the combined modality treatment of limited stage small-cell lung cancer. A one-institution study.

PURPOSE: We report the toxicity, patterns of failure and survival of a cohort of patients with limited disease (LD) small-cell lung cancer (SCLC) treated with combined radiation and chemotherapy. During the course of thoracic irradiation, we added intravenous (i.v.) etanidazole (SR-2508, a third-generation 2-nitroimidazole) as a hypoxic cell sensitizer in an attempt to reduce the primary local failure rate and improve survival. METHODS AND MATERIALS: Between July 1988 and August 1990, 30 consecutive patients with limited disease SCLC were enrolled and treated on a Phase II protocol receiving a standard combination chemotherapy regimen utilizing i.v. cisplatin 25 mg/m2/day x 3 days, i.v. etoposide 100 mg/m2/day x 3 days alternating with intravenous cyclophosphamide 1000 mg/m2/day, intravenous doxorubicin 15 mg/m2, and intravenous vincristine 2 mg (CAV) to a total of six cycles every 3 weeks. Radiotherapy and etanidazole were started after the first cycle of chemotherapy. Etanidazole was administered intravenously at a dose of 2 g/m2 three times per week for a total of 30 g/m2 during the course of thoracic radiation that delivered 50.00 Gy tumor dose in 25 fractions in an overall time of 6 weeks. RESULTS: The overall response rate of the primary lesion in the thorax was 96% (CR + PR), with 64% complete responses. The median time to treatment failure was 18 months. Of the patients that have relapsed, only 18% failed in the thorax (alone or concomitant with other sites). This is a marked improvement compared to the 40-50% rate reported in the literature. The 2-year crude survival was 46%. The 3- and 5-year crude survival rate with no evidence of disease was 33 and 30%, respectively. We have observed a 10% increase in the incidence of transient etanidazole related peripheral neuropathies compared to previous etanidazole studies not utilizing systemic chemotherapy. There was no increased incidence of radiation esophagitis, pulmonary toxicity, or nephro- or myelotoxicity over and above what has been routinely observed with this radio/chemotherapy regimen. There were no treatment related deaths. CONCLUSION: The moderate increase in etanidazole-related transient peripheral neuropathies could have been related to the concomitant use of etanidazole with vincristine and cisplatin. Although the almost 50% improvement in the incidence of tumor failure rate in the thorax in this small group of patients did not correlate with an equal marked improvement in their survival, the 5-year survival outcome in our series is at least equal or better than the best reports in the literature of larger clinical trials. We believe there is sufficient data from this study, particularly the improvement of local tumor control, to warrant a large randomized controlled clinical trial, using the most current systemic chemotherapy with concomitant thoracic irradiation with or without the most effective available hypoxic cell cytotoxic/sensitizer.

Antineoplastic Combined Chemotherapy Protocols↗
PubMedDate not supplied

Pilot study of local hyperthermia, radiation therapy, etanidazole, and cisplatin for advanced superficial tumours.

Five patients (six hyperthermia sites) with advanced superficial tumours were treated with combined etanidazole, cisplatin, local hyperthermia, and radiation therapy as part of a Phase I pilot study. Treatment was given once weekly and consisted of etanidazole 3 gm/m2 IV bolus, cisplatin 50 mg/m2 IV bolus, hyperthermia for 60 min with a target temperature of 43 degrees C, and radiation therapy 500 cGy/fraction (median total dose 3000 cGy) for a total of six weeks. Blood levels of etanidazole were taken during treatment at week 1 and week 4. Etanidazole drug exposure was calculated using the trapezoidal rule and expressed as the area under the curve (AUC) of plasma concentration x time. Five of six treatment sites had received prior irradiation. Prior chemotherapy had been given in three patients and tamoxifen therapy given in the other two patients. The median follow-up time is 34 months; 3/5 patients have died of disease. The most significant toxicity was grade I or II nausea and vomiting associated with 19/32 treatments (59%) and a second degree burn in 2/6 fields. None of the five patients experienced peripheral neuropathy, skin ulceration, or needed surgical repair. In addition, there was mild renal toxicity; pharmacokinetic analysis showed a 28-75% increase in the week 1 to week 4 AUC in three patients, all of whom had a decrease in creatinine clearance over the same time of 15-47%. This pilot study suggests this combined modality therapy can be delivered without major complications and that renal function, determined by creatinine clearance, affects clearance of etanidazole and alters the AUC. Therefore, monitoring renal function is important in patients receiving etanidazole in addition to other nephrotoxic agents such as cisplatin. The impact of etanidazole on the therapeutic index of hyperthermia, radiation therapy and cisplatin may be worth of study, especially since a positive interaction between these modalities is found in laboratory models.

Adult↗
PubMed1994

Combined-modality therapy of esophageal cancer with radiotherapy, etanidazole, and cisplatin-fluorouracil, with or without surgery: neurotoxicity, other toxicities and outcome.

PURPOSE: To investigate whether etanidazole and cisplatin can be given safely together and to evaluate the relationship between incidence of peripheral neuropathy and cumulative exposure to etanidazole and cisplatin, as well as other toxicities and treatment outcome. METHODS AND MATERIALS: Thirty-two previously untreated patients with locally advanced esophageal cancer were entered on a Phase I study of etanidazole combined with radiation therapy and chemotherapy. Cisplatin/5-FU (two cycles, weeks 1 and 4) and etanidazole (weeks 2, 3 and 5) were given concurrently with radiation therapy. Eligible patients then underwent surgical resection. All patients were scheduled to receive two additional cycles of cisplatin/5-FU chemotherapy after completion of radiation therapy (definitive arm) or surgery (preoperative arm). RESULTS: Of 19 fully evaluable patients, nine (47%) developed peripheral neuropathy. Six of six patients, 65 years or older, experienced peripheral neuropathy, compared with three of 13 patients less than 65 years old (p = .003). For patients younger than 65 years, two of the two patients with single dose area under the curve (AUC) > 4.0 mMhr experienced peripheral neuropathy, compared with one of 11 patients with single-dose AUC < 4.0 mMhr (p = .03). Grade 4 toxicity included neutropenia (23%) and thrombocytopenia (26%). No other Grade 4 toxicity was observed. The pathologic complete response rate in patients who underwent surgical resection was 29%. CONCLUSION: This regime of chemotherapy, radiotherapy, and etanidazole had acceptable toxicity. However, combining etanidazole and cisplatin appears to increase the risk of developing peripheral neuropathy for at least some categories of patients. Further studies of these interactions are needed.

Adenocarcinoma↗
PubMed2002

Sustained release of etanidazole from spray dried microspheres prepared by non-halogenated solvents.

Etanidazole, a kind of radiosensitizer, was encapsulated in the spray-dried microspheres using biodegradable polymer PLGA 65:35 as the carrier for controlled release applications. Two non-halogenated solvents, e.g., ethyl acetate (EA) and ethanol, were tested to modify the properties of microspheres prepared by the commonly used solvent dichloromethane (DCM) alone. Their effects on the release behavior, morphology, particle size, and encapsulation efficiency of etanidazole-loaded microspheres were determined, and results were compared with DCM. The particle formation process via spray drying technique was also analyzed in order to understand the results obtained. It was found that larger percentage of EA (in the solvent mixture consisting of DCM and EA) in the fabrication of PLGA 65:35 microspheres decreases the initial burst, release rate and prolongs the release duration of etanidazole. In contrast to the spherical and porous microspheres prepared by DCM, the microspheres prepared by the solvent EA are all nonporous with a doughnut like surface structure due to its comparatively rapid phase transition (phase inversion) but slow solvent evaporation rate (longer time required to solidify). Increasing the polymer concentration (e.g., 4%, w/v) can bring about much more spherical microspheres by spray drying. Although ethanol, as a co-solvent, can dissolve a higher amount of etanidazole and lead to a higher drug encapsulation efficiency, the addition of ethanol in the DCM solvent can significantly increase the initial burst and the release rate of the microspheres due to the inhomogeneous drug distribution and structure of microspheres caused by phase separation. This study shows that ethyl acetate is an excellent low-toxic solvent that can be used in the spray drying technique for decreasing the initial burst, prolonging the release duration of a highly water-soluble drug like etanidazole. The use of EA provides a promising way to develop a sustained release system for etanidazole and other highly water-soluble drugs.

Acetates↗
PubMed2003

A phase I trial of etanidazole and hyperfractionated radiotherapy in children with diffuse brainstem glioma.

PURPOSE: To determine the toxicity and maximum tolerated dose of etanidazole administered concurrently with hyperfractionated radiation therapy (HRT) for children with brainstem glioma. METHODS AND MATERIALS: Eighteen patients with brainstem glioma were treated with etanidazole and HRT on a dose escalation protocol (Phase I trial) between 1990 and 1996. All patients had MRI confirmation of diffuse pontine glioma and signs/symptoms of cranial nerve deficit, ataxia, or long tract signs of <6 months' duration. Cervicomedullary tumors were excluded. Patients (median age: 8.5 years; 11 males, 7 females) received HRT to the tumor volume plus a 2-cm margin with parallel-opposed 6-15-MV photons. The total dose was 66 Gy in 44 fractions (1.5 Gy b.i.d., with at least 6 h between fractions) for the first 3 patients and 63 Gy in 42 fractions for the subsequent 15 patients. Etanidazole was administered as a rapid i.v. infusion 30 min before the morning fraction of HRT. Planned doses of etanidazole were 1.8 g/m(2) x 17 doses (30.6 g/m(2)) at Step 1 to a maximum of 2.4 g/m(2) x 21 doses (50.4 g/m(2)) at Step 8. Dose escalation was planned with 3 patients at each of the 8 levels. RESULTS: Three patients were treated at each dose level except Level 2, on which only 1 patient was treated. The highest dose level achieved was Level 7, which delivered a total etanidazole dose of 46.2 g/m(2). Two patients were treated at this level, and both patients experienced Grade 3 toxicity in the form of a diffuse cutaneous rash. Three patients received a lower dose of 42 g/m(2) (dose Level 6) without significant toxicity, and this represents the maximum tolerated dose (MTD). There were 23 cases of Grade 1 toxicity (10 vomiting, 5 peripheral neuropathy, 2 rash, 2 constipation, 1 weight loss, 3 others), 11 cases of Grade 2 toxicity (4 vomiting, 2 skin erythema, 2 constipation, 1 arthralgia, 1 urinary retention, 1 hematologic), and 4 Grade 3 toxicities (2 rash, 1 vomiting, 1 skin desquamation). Grade 2 or 3 peripheral neuropathy was not seen at any dose level. The median survival from the start of treatment was 8.5 months (range: 3-58 months). CONCLUSION: The MTD of etanidazole in children receiving HRT for brainstem glioma is 42 g/m(2), with cutaneous rash as the dose-limiting toxicity. This is in contrast to the adult experience, which demonstrates a 24% lower MTD of 34 g/m(2) limited by peripheral neuropathy.

Adolescent↗
PubMed1996

Effect of BSO and etanidazole on neurofilament degradation in neonatal rat spinal cord cultures.

Peripheral neuropathy is the major dose-limiting toxicity of the hypoxic cell sensitiser, etanidazole. Previous work from this laboratory using culture neuronal cell lines suggested that nitroimidazole-induced degradation of neurofilament proteins might be the critical biological event mediating this neurotoxicity. The purpose of the present study was to develop the neurofilament degradation assay in an organotypic spinal cord culture system with the goal of developing strategies for optimising sensitiser efficacy as well as ameliorating nitroimidazole-induced neurotoxicity. Spinal cord cultures were treated with etanidazole and neurofilament protein degradation was analysed by immunoblot analysis. Spinal cord cultures exposed to etanidazole exhibited a dose-dependent loss of parent neurofilament proteins, with concomitant appearance of low molecular weight degradation products. The potential neurotoxic effect of L, S-buthionine sulphoximine (BSO), a compound that enhances the radiosensitising effectiveness of 2-nitroimidazoles, was also screened in this assay system. BSO alone, at concentrations up to 100 microM, did not promote neurofilament degradation. BSO (20 microM) enhanced the effect of etanidazole on neurofilament degradation by a dose-modifying factor of 1.6 +/- 0.5. Since 20 microM BSO is expected to enhance etanidazole radiosensitisation of hypoxic cells by a larger factor, this suggests that a therapeutic gain could be achieved using BSO in combination with etanidazole in radiation therapy.

Animals↗
PubMed1998

Dose escalation of the hypoxic cell sensitizer etanidazole combined with ifosfamide, carboplatin, etoposide, and autologous hematopoietic stem cell support.

Multiple mechanisms of drug resistance contribute to treatment failure. Although high-dose therapy attempts to overwhelm these defenses pharmacologically, this approach is only successful in a fraction of treated patients. Many drug resistance mechanisms are shared between malignant and normal cells, but the expression of various drug resistance mechanisms associated with hypoxia is largely confined to tumor tissue. Thus, reversal of this mechanism is likely to provide a therapeutic advantage to the host. This study was designed to define the dose-limiting toxicities and maximum tolerated dose of etanidazole when it is given concurrently with high-dose ifosfamide, carboplatin, and etoposide (ICE), with hematopoietic stem cell support. The maximum tolerated doses of high-dose ICE were administered concurrently with dose escalations of etanidazole, a hypoxic cell sensitizer. All agents were given by 96-h continuous i.v. infusion beginning on day -7. Mesna uroprotection was provided. Autologous marrow and cytokine mobilized peripheral blood progenitor cells were reinfused on day 0. Granulocyte colony-stimulating factor was administered following reinfusion until the granulocytes recovered to > 1000/microliter. Fifty-five adults with advanced malignancies were enrolled in cohorts of five to nine patients. Four dose levels of etanidazole between 3 and 5.5 g/m2/day (12, 16, 20, and 22 g/m2 total doses) and two doses of carboplatin (1600 and 1800 mg/m2 total doses) were evaluated. Seven patients died of organ toxicity (13%); two each from veno-occlusive disease of liver and sepsis; and one each from sudden death, renal failure, and refractory thrombocytopenic hemorrhage. Five deaths occurred at the top dose level. One additional patient suffered a witnessed cardiorespiratory arrest from ventricular fibrillation and was resuscitated. Dose-dependent and largely reversible peripheral neuropathy was observed consisting of two syndromes: severe cramping myalgic/neuralgic pain, predominantly in stocking glove distribution, occurring between day -3 and day 0, and a sensory peripheral neuropathy with similar distribution peaking around day +60. The maximal achievable dose of etanidazole (16 g/m2 dose level) resulted in a mean serum level of 38 micrograms/ml (25-55 micrograms/ml). Etanidazole significantly enhanced host toxicity of high-dose ICE. Effective modulatory doses of etanidazole could not be given with acceptable toxicity using this schedule.

Adult↗
PubMed1991

A comparison of radiosensitization by etanidazole and pimonidazole in mouse tumors.

Radiosensitization by pimonidazole (Ro 03-8799) was tested in three murine tumors, EMT6/SF using the excision assay, SCC-VII/SF using the excision and growth delay assays, and MDAH-MCa-4 using TCD50 assays with both single doses and 6 fractions of radiation with a 24-hr interfraction interval. Results were compared with those using etanidazole (SR-2508), both at equitoxic doses and at doses giving tumor concentrations similar to those achievable in the clinic. In excision assays with EMT6/SF and SCC-VII/SF tumors, pimonidazole and etanidazole gave similar radiosensitization at similar concentrations in the tumors. Pimonidazole, however, did not demonstrate radiosensitization in SCC-VII/SF tumors in the growth delay assay, despite tumor concentrations that gave maximum sensitization in the excision assay. Furthermore, pimonidazole gave less than expected sensitization in single dose and 6-fraction TCD50 assays with MDAH-MCa-4 tumors, and less sensitization than comparable levels of etanidazole in this tumor line. When the concentration of pimonidazole in the tumors was approximately 0.36 mumoles/g the dose modification factor (DMF = dose without sensitizer/dose with sensitizer to give an isoeffect) was 1.56 (1.40-1.74, 95% c.l.) in single dose TCD50 assays. Etanidazole, however, gave a DMF of 1.92 (1.59-2.32) with a tumor concentration of approximately 0.32 mumoles/g and 1.69 (1.46-1.96) with a tumor concentration of approximately 0.21 mumoles/g. Thus, etanidazole gave more consistent sensitization for different tumors and different endpoints than did pimonidazole. The results appear to confirm the disappointing performance of pimonidazole in the clinic.

Animals↗
PubMed1992

Logistics in designing clinical trials for etanidazole (SR 2508): an RTOG experience.

In a Phase II study of etanidazole (SR 2508), the dose of 17 x 2 g/m2 (total drug dose: 34 g/m2) was tested in 33 patients and the toxicity was deemed acceptable. A Phase III trial is now in progress comparing conventional radiotherapy with conventional radiotherapy plus etandizole (2 g/m2 i.v. 30 to 60 min before radiotherapy each Monday, Wednesday, and Friday to 34 g/m2 in 17 doses) in patients with unresectable head and neck carcinomas. A recent analysis showed only 14.7% grade 1 and 3.9% Grade 2 peripheral neuropathy. In the initial study design, 133 evaluable patients per treatment arm could achieve an 80% level of power of detecting a 15% difference in local-regional control rates between the radiotherapy arm (25% local-regional control at 2 years) and the radiotherapy plus etanidazole arm (assuming a 40% rate). Allowing for 20 ineligible cases in each arm, a total number of 306 was required. An interim analysis showed that 27% of the patients assigned to radiotherapy plus etanidazole are receiving less than 14 doses of the drug. It is assumed that less than 14 drug doses will not produce any therapeutic gain, therefore, a true 40% local-regional control rate in the radiotherapy plus etanidazole arm will be observed as a 36% rate when analyzed by assigned treatment. Using this information, the study was modified to have an 80% level of power in detecting a difference between a 25% local-regional control rate in the radiotherapy group and a 36% rate in the radiotherapy plus etanidazole group. Allowing for a 10% patient ineligibility rate, 518 patients are required. With 12 patients entered per month, it is estimated that patient accrual to this study will continue through October 1991.

Carcinoma, Squamous Cell↗