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PubMed1991

Comparison of the cytotoxicity in vitro of temozolomide and dacarbazine, prodrugs of 3-methyl-(triazen-1-yl)imidazole-4-carboxamide.

The present study tested the hypothesis that the experimental antineoplastic imidazotetrazinone temozolomide degrades in the biophase to 3-methyl-(triazen-1-yl)imidazole-4-carboxamide (MTIC) and exerts its cytotoxicity via this species. MTIC is a metabolite of the antimelanoma agent dacarbazine and is thought to be responsible for the antineoplastic activity of the latter. Cytotoxicity in vitro was investigated in TLX5 murine lymphoma cells. MTIC and temozolomide were cytotoxic in the absence of mouse-liver microsomes, whereas dacarbazine required metabolic activation. The generation of MTIC from either dacarbazine, its primary metabolite 5-[3-(hydroxymethyl)-3-methyl-triazen-1-yl]-imidazole-4-carboxamid e (HMMTIC) or temozolomide was studied by reversed-phase high-performance liquid chromatography in incubation mixtures under the conditions of the cytotoxicity assay. MTIC was found in incubations of temozolomide with or without microsomes. Dacarbazine yielded MTIC (and HMMTIC) only when microsomes were included in the incubation mixture. Although the mode of action of temozolomide seems to be similar to that of dacarbazine, the results obtained in this study show that these agents differ markedly in their ability to generate the active species MTIC.

Animals↗
PubMed1989

Inhibition of cellular esterases by the antitumour imidazotetrazines mitozolomide and temozolomide: demonstration by flow cytometry and conventional spectrofluorimetry.

Using flow cytometry and conventional spectrofluorimetry we have previously shown that chloroethylnitrosoureas (CNUs) can exhibit marked inhibition of cellular enzymes catalysing hydrolysis of fluorescein diacetate (FDA). More potent inhibition was seen for the carbamoylating CNUs, whereas alkylating agents were largely inactive. We now report results obtained with the developmental imidazotetrazines mitozolomide and temozolomide in comparison with BCNU, the novel alkylating agents clomesome and cyclodisone, and the active mitozolomide metabonate MCTIC. Inhibition of EMT6 mouse mammary-tumour esterases was seen for mitozolomide and temozolomide, and activity against purified porcine carboxylesterase was demonstrated. Flow cytometric analysis showed that inhibition occurred across the entire EMT6 cell population, with no evidence of a subpopulation resistant to enzyme inhibition. Inhibitory potency for the imidazotetrazines was much weaker than for BCNU. With EMT6 cells, I50 values from flow cytometry were 9.7 x 10(-3) M and 1.5 x 10(-3) M for mitozolomide and temozolomide compared with 3.7 x 10(-4) M for BCNU. These were higher than the ID50 values for in vitro antitumour activity (MTT assay), 8.5 x 10(-6) M in the case of mitozolomide and 1.2 x 10(-5) M for BCNU, but similar to that of 5.6 x 10(-4) M for the less toxic temozolomide. MCTIC and cyclodisone showed very low activity, but significant inhibition was seen for clomesome. The results are consistent with the view that the imidazotetrazines do not exhibit major carbamoylating ability, although significant effects are seen at cytotoxic concentrations of temozolomide. In addition, the potential for the generation of carbamoylating species at the enzyme active site cannot be ruled out.

Animals↗
PubMed1990

Characterisation of urinary metabolites of temozolomide in humans and mice and evaluation of their cytotoxicity.

The experimental antineoplastic agent temozolomide was not metabolised in vitro at a measurable rate by mouse liver fractions. In contrast, the temozolomide analogue 3-methylbenzotriazinone was metabolically N-demethylated by hepatic microsomes to yield benzotriazinone. The major route of excretion of [14C]-labelled temozolomide in mice was via the kidneys. An acidic metabolite of temozolomide, probably a conjugate, was found in the urine of mice, but its identity could not be established unambiguously. Spectroscopic analysis and chemical tests revealed that it possesses an intact NNN-linkage. Another metabolite was found in the urine of patients but not of mice. This metabolite was identified as the 8-carboxylic acid derivative of temozolomide. Unlike the unknown species, this metabolite was cytotoxic against TLX5 lymphoma cells in vitro.

Animals↗
PubMed2005

Temozolomide combined with irradiation as postoperative treatment of primary glioblastoma multiforme. Phase I/II study.

BACKGROUND AND PURPOSE: The role of radiochemotherapy in the treatment of primary glioblastoma multiforme is still discussed controversially. To evaluate the feasibility and toxicity of irradiation and concomitant administration of 50 mg/m(2) temozolomide in patients with primary malignant glioma, this phase I/II study was conducted. PATIENTS AND METHODS: 53 Patients with histologically confirmed WHO grade IV malignant glioma were enrolled into the study. All patients were treated with radiation therapy up to a total dose of 60 Gy using conventional fractionation of 5 x 2.0 Gy/week. Temozolomide was administered orally each therapy day at a dose of 50 mg/m(2). RESULTS: Prior to radiochemotherapy, complete resection (n = 14), subtotal resection (n = 22) or a biopsy (n = 17) of the tumor was performed. The median time interval between surgery and radiochemotherapy was 21 days. Treatment-related toxicity was very mild. Acute toxicity > grade 2 was observed in one patient who developed grade 4 hemotoxicity. Minor side effects of chemotherapy included nausea and vomiting. No severe late effects were observed. Median progression-free and overall survival were 8 and 19 months, respectively. The overall survival rate was 72% at 1 and 26% at 2 years. Age and extent of surgery significantly influenced survival. CONCLUSION: The combination of temozolomide plus radiation therapy is feasible and safe in terms of toxicity. Overall survival times were relatively long compared to survival times reported for radiotherapy alone. The application of 50 mg/m(2) of temozolomide can be performed throughout the whole time course without interruption due to side effects and might largely contribute to the prolonged overall survival. Further evaluation is warranted as to which dose of temozolomide is optimal with regard to tumor response and toxicity.

Adult↗
PubMed2002

[Temozolomide as therapeutic option for patients with metastatic melanoma and poor prognosis].

BACKGROUND AND OBJECTIVE: Stage IV melanoma patients with a very advanced disease are usually excluded from clinical trials. We treated 25 stage IV patients with temozolomide - a cytostatic drug with 100% oral bioavailability and considerable penetration of CNS tissue. PATIENTS/METHODS: 25 patients (17 female, 8 male) between 24 and 82 years (mean: 55.5 years) were included in this retrospective study. 19 patients had received at least one and up to four previous chemotherapy regimens during the course of stage IV disease. 11 (44%) patients showed cerebral metastases prior to therapy with temozolomide. 200 mg/m2 temozolomide were given orally at home on day 1 to 5 in week 1 and in week 5, respectively. RESULTS: Out of 23 evaluable patients 2 (8.7%) showed a partial remission, 2 (8,7%) a minor response, 6 (26.1%) had stable disease, 1 (4,3%) a mixed response, and 12 (52.1%) patients experienced disease progression. Sites of remission included brain, lung, liver, lymph nodes and muscle. Two patients interrupted therapy due to severe leuko- and thrombocytopenia (WHO grade 3 and 4). All other patients tolerated treatment with temozolomide well and no dose reduction was necessary. The median overall survival was 7 months (2-28+ months) since beginning of therapy and 15 months (4-63+ months) since onset of stage IV disease. CONCLUSION: Temozolomide represents a safe treatment option in patients with metastatic melanoma and poor prognosis.

Administration, Oral↗
PubMed2001

New approaches for temozolomide therapy: use in newly diagnosed glioma.

Temozolomide is a novel oral alkylating agent that has been approved for the treatment of patients with refractory malignant glioma. Treatment with temozolomide is now being explored in patients with newly diagnosed malignant glioma in several ongoing clinical trials, and alternative treatment schedules are being evaluated. A schedule of continuous daily treatment with temozolomide for 6 or 7 weeks has been developed and determined to be safe, effective, and well tolerated. When temozolomide was continuously given along with a standard course of radiation therapy for 6 or 7 weeks, followed by adjuvant treatment with temozolomide, promising preliminary results were seen in patients with malignant gliomas.

Antineoplastic Agents, Alkylating↗
PubMed2001

Temozolomide for treating brain metastases.

The metastasis of solid tumors to the brain is associated with a poor prognosis despite aggressive treatment. Available treatment options are limited, as many chemotherapeutic agents do not penetrate the blood-brain barrier. Temozolomide (Temodar in the United States, Temodal globally; Schering Corporation, Kenilworth, NJ) is a novel chemotherapeutic agent with a good safety profile that crosses the blood-brain barrier and has shown activity against many human solid tumors. In two phase II trials of temozolomide in heavily pretreated patients with various solid tumor brain metastases, temozolomide was safe and generally well tolerated and showed clinical activity, with three partial responses and 19 disease stabilizations. Results of a third randomized phase II trial of concurrent administration of temozolomide and radiation therapy followed by adjuvant temozolomide therapy compared with radiation alone showed a higher rate of complete and partial responses (objective response of 96% v 67%) and significantly more complete responses (38% v 33%, P =.017), primarily in patients with newly diagnosed brain and lung metastases.

Aged↗
PubMed2001

Future directions for temozolomide therapy.

Although the initial indications of temozolomide (Temodar in the United States, Temodal globally; Schering Corporation, Kenilworth, NJ) therapy are for refractory central nervous system malignancies (anaplastic astrocytoma in the United States and Europe, glioblastoma multiforme in Europe), a number of clinical trials are planned or ongoing to evaluate the efficacy and safety of temozolomide in newly diagnosed glioma, oligodendroglioma, pediatric glioma, brain metastases, metastatic melanoma, and other systemic tumors. Also under investigation are modifications to the temozolomide dosing schedule, other routes of administration, and treatment regimens that include temozolomide in combination with other chemotherapeutic and biologic agents. Temozolomide has the potential to be a useful agent in the treatment of a variety of cancers.

Antineoplastic Agents, Alkylating↗
PubMed2003

Gliomatosis cerebri: clinical, neurochemical and neuroradiological response to temozolomide administration.

Gliomatosis cerebri is a rare form of diffusely infiltrating glioma that is typically resistant to conventional chemotherapy and radiation therapy and carries a poor prognosis. Temozolomide has shown antineoplastic activity against malignant gliomas and more recently was beneficial in one patient with gliomatosis cerebri. To make an objective assessment of the effect of long-term temozolomide administration in a patient with gliomatosis cerebri we used brain proton magnetic resonance spectroscopy and structural MRI. A 46-year-old man with gliomatosis cerebri was treated with temozolomide (200 mg/m(2) per day for 5 days every 28 days). Twenty cycles of temozolomide resulted in a marked reduction in choline and scyllo-inositol content, as detected using brain proton MR spectroscopy, indicating reduced tumor cellularity and/or growth rate. Neurochemical improvements were associated with normalization of the signal intensity in most of the previously affected cerebral regions and regression of mass effect on MRI. A left pyramidal syndrome, present at the start of the treatment, disappeared. Our observation lends support to larger clinical trials evaluating the use of temozolomide to treat this brain tumor.

Antineoplastic Agents, Alkylating↗
PubMed1994

NMR and molecular modeling investigation of the mechanism of activation of the antitumor drug temozolomide and its interaction with DNA.

The hypothesis that the antitumor prodrug temozolomide is ring-opened to MTIC which then further breaks down to a reactive diazonium ion at guanine-rich sequences in DNA has been probed by NMR spectroscopy and computational techniques. Temozolomide is stable at acid pH but decomposes to MTIC at pH > 7; in contrast, MTIC is stable at alkaline pH values but rapidly fragments in a methylating mode at pH < 7. The proximate methylating agent is the reactive methyldiazonium species. Runs of guanine residues represent an accessible nucleophilic microenvironment in DNA site-specific conversion of the prodrug temozolomide to MTIC possibly via an activated water molecule in the major groove. Molecular modeling of the structure of temozolomide indicates that the prodrug can make a favorable noncovalent encounter with DNA. The known structure-activity relationships as well as the biological and clinical properties of temozolomide can be interpreted in terms of this model.

Antineoplastic Agents↗
PubMed2001

A phase II trial of temozolomide for patients with recurrent or progressive brain metastases.

BACKGROUND: Treatment options for patients with recurrent brain metastases are extremely limited. This study was designed to determine the safety and efficacy of temozolomide in the treatment of recurrent or progressive brain metastases. PATIENTS AND METHODS: Forty-one patients (11 men, 30 women) with a median KPS of 80 were treated with temozolomide 150 mg/m2/day (200 mg/m3/day if no prior chemotherapy) for 5 days; treatment cycles were repeated every 28 days. Primary tumor types included 22 non-small cell lung, 10 breast, three melanoma, two small cell lung, two rectal, one ovarian and one endometrial cancer. RESULTS: There were five episodes of grade 3 thrombocytopenia and one grade 4 leukopenia. Significant non-hematologic toxicity possibly related to temozolomide included pneumonitis [21, constipation [1], and elevated liver enzymes [21. Thirty-four patients were assessed for radiographic response; two had a partial response, 15 stable disease and 17 progressed. Both objective responses were seen in patients with non-small cell lung cancer. Overall median survival was 6.6 months. CONCLUSIONS: Single agent temozolomide achieved disease control (PR or SD) in 41% of patients with recurrent brain metastases from a variety of primary malignancies with minimal toxicity. Therefore, temozolomide may be a reasonable treatment option for some patients with recurrent brain metastases.

Adult↗
PubMed2002

Temozolomide as second-line chemotherapy for relapsed gliomas.

BACKGROUND: Temozolomide, an imidazotetrazine prodrug has shown activity in phase II studies in patients with high-grade glioma at first recurrence. We assessed the efficacy of temozolomide as second-line therapy following failure of PCV chemotherapy in patients with recurrent/progressive gliomas. PATIENTS AND METHODS: Between September 1994 and November 2000, 32 patients with high-grade gliomas at second recurrence/progression received temozolomide as salvage therapy and results were reviewed retrospectively. RESULTS: Of 32 assessable patients 7 had clinical improvement; there were no imaging responses. Median survival of the cohort was 4 months, with 28% alive at 6 months. Age, performance status, histology and previous response to PCV chemotherapy did not predict for clinical response to temozolomide. CONCLUSION: In the small cohort of patients with recurrent malignant glioma who failed PCV chemotherapy temozolomide demonstrated limited activity as second-line treatment although this remains within the confidence intervals of response seen in patients with glioblastoma.

Adult↗
PubMed1993

Depletion of O6-alkylguanine-DNA alkyltransferase correlates with potentiation of temozolomide and CCNU toxicity in human tumour cells.

Temozolomide (8-carbamoyl-3-methylimidazo[5,1-d]-1,2,3,5-tetrazin-4-(3H)-one) has shown promising activity in Phase I trials against some brain (glioma) and skin (melanoma, mycosis fungoides) cancers. Temozolomide and lomustine (CCNU) showed parallel toxicity in seven human tumour cell lines and this generally correlated (correlation coefficients 0.87 and 0.92 respectively) with the level of expression of the DNA repair protein O6-alkylguanine-DNA alkyltransferase (ATase, EC 2.1.1.63). Pretreating cells with the ATase inhibitor, O6-benzylguanine (BG), potentiated cytotoxicity to a similar degree with both drugs, but did not sensitise a cell line (ZR-75-1) expressing very low levels of this protein. When BG pretreatment was combined with repeat doses of temozolomide a dramatic potentiation (300 fold) was seen in MAWI cells, which express high levels of ATase, but not in a cell line (U373) expressing lower levels of ATase. [14C]-labelled temozolomide uptake was similar in sensitive and resistant lines. Human ATase-cDNA transfected xeroderma pigmentosum (XP) fibroblasts were more resistant than XP control cells to temozolomide and the related chloroethylating agent mitozolomide and although BG completely suppressed ATase activity in these cells, resistance was still greater than in control cells.

Antineoplastic Agents↗
PubMed1995

Potentiation of temozolomide-induced cytotoxicity: a comparative study of the biological effects of poly(ADP-ribose) polymerase inhibitors.

Four poly(ADP-ribose) polymerase (PADPRP) inhibitors [3-aminobenzamide, benzamide, 3,4-dihydro-5-methoxyisoquinolin-1(2H)-one (PD 128763) and 8-hydroxy-2-methylquinazolin-4(3H)-one (NU1025)] were compared with respect to their effects on a number of biological end points. The following parameters were assessed: their ability to inhibit the enzyme in permeabilised L1210 cells; their ability to potentiate the cytotoxicity of temozolomide (including the cytotoxicity of the compounds per se); their ability to increase net levels of temozolomide-induced DNA strand breaks and inhibit temozolomide-induced NAD depletion. PD 128763 and NU1025 were equipotent as PADPRP inhibitors, and 40- and 50-fold more potent than benzamide and 3-aminobenzamide respectively. All the compounds acted in a concentration-dependent manner to potentiate the cytotoxicity and increase DNA strand break levels in cells treated with temozolomide. There was an excellent correlation between the potency of the compounds as PADPRP inhibitors and their effects on cell survival and DNA repair. Temozolomide treatment caused a decrease in cellular NAD levels, and this was abolished by the PADPRP inhibitors. In conclusion, the new generation of PADPRP inhibitors are at least 50-fold more effective than 3-aminobenzamide as chemopotentiators, and can be used at micromolar rather than millimolar concentrations in intact cells.

Animals↗
PubMed2003

Temozolomide induces apoptosis and senescence in glioma cells cultured as multicellular spheroids.

Temozolomide is an alkylating cytostatic drug that finds increasing application in the treatment of melanoma, anaplastic astrocytoma and glioblastoma multiforme. The compound is a prodrug that decomposes spontaneously, independent of an enzymatic activation step. DNA methylation induces futile mismatch repair cycles and depletion of the DNA repair enzyme O(6)-methylguanine-DNA methyltransferase should then initiate programmed cell death. We show drug-dependent inhibition of tumour growth in a three-dimensional cell culture model of the glioma cell lines U87MG and GaMG. Migrational behaviour of the glioblastoma cells remained unaltered. However, coincubation of tumour spheroids with primary brain aggregates showed reduced tumour cell invasion into brain tissue in the presence of temozolomide. This was not achieved by slowing cellular migration, as temozolomide-treated cells displayed no reduced motility. By transferase-mediated dUTP nick-end labelling (TUNEL) of apoptotic nuclei, we found that the drug was able to induce apoptosis throughout the tumour cell spheroids. Apoptosis was highest in the core region of the spheroids. Repetitive application of sublethal doses of temozolomide to multicellular spheroids resulted in the development of drug resistance in GaMG cells. We suggest that temozolomide is a strong initiator of apoptosis in glioblastoma tumour cells in a spheroid cell culture system, when cells are already in a stressful environment.

Antineoplastic Agents, Alkylating↗
PubMed2006

Temozolomide 3 weeks on and 1 week off as first-line therapy for recurrent glioblastoma: phase II study from gruppo italiano cooperativo di neuro-oncologia (GICNO).

The efficacy of temozolomide strongly depends on O(6)-alkylguanine DNA-alkyl transferase (AGAT), which repairs DNA damage caused by the drug itself. Low-dose protracted temozolomide administration can decrease AGAT activity. The main end point of the present study was therefore to test progression-free survival at 6 months (PFS-6) in glioblastoma patients following a prolonged temozolomide schedule. Chemonaïve glioblastoma patients with disease recurrence or progression after surgery and standard radiotherapy were considered eligible. Chemotherapy cycles consisted of temozolomide 75 mg/m(2)/daily for 21 days every 28 days until disease progression. O(6)-methyl-guanine-DNA-methyl-tranferase (MGMT) was determined in 22 patients (66.7%). A total of 33 patients (median age 57 years, range 31-71) with a median KPS of 90 (range 60-100) were accrued. The overall response rate was 9%, and PFS-6 30.3% (95% CI:18-51%). No correlation was found between the MGMT promoter methylation status of the tumours and the overall response rate, time to progression and survival. In 153 treatment cycles delivered, the most common grade 3/4 event was lymphopoenia. The prolonged temozolomide schedule considered in the present study is followed by a high PFS-6 rate; toxicity is acceptable. Further randomised trials should therefore be conducted to confirm the efficacy of this regimen.

Adult↗
PubMed2004

Evaluation of temozolomide in patients with myelodysplastic syndrome.

In our previous phase I study of temozolomide in patients with acute leukemia, temozolomide was well tolerated and demonstrated significant anti-leukemic activity. The maximum tolerated dose was 200 mg/m2/d for 7 days, repeated approximately every 5-6 weeks. In the current study, we evaluated the same dose of temozolomide in patients with myelodysplastic syndrome. Fourteen patients received 19 courses of temozolomide. The median age was 71 years. In this study, treatment was poorly tolerated with patients requiring admission in 9 of 19 courses. Toxicity included worsening cytopenias, neutropenic fever, and exacerbation of cardiac disease, the latter due to worsening anemia. An unusual finding was the development of leukocytoclastic vasculitis in 4 patients. There were no formal responses to therapy. The current schedule of temozolomide is not efficacious in patients with myelodysplastic syndrome.

Aged↗
PubMed2005

Temozolomide in combination with BCNU before and after radiotherapy in patients with inoperable newly diagnosed glioblastoma multiforme.

BACKGROUND: The aim of this study was to evaluate the efficacy and safety of carmustine (BCNU) in combination with temozolomide as first-line chemotherapy before and after radiotherapy (RT) in patients with inoperable, newly diagnosed glioblastoma multiforme (GBM). PATIENTS AND METHODS: Forty patients were treated with BCNU (150 mg/m2) on day 1 and temozolomide (110 mg/m2/day) on days 1 through 5 of each 42-day cycle for up to four cycles prior to conventional RT (2 Gy fractions to a total of 60 Gy). After RT, BCNU + temozolomide was administered for four additional cycles or until progression. The primary end point was response rate; secondary end points included progression-free survival (PFS); overall survival (OS) and safety. RESULTS: Sixty per cent of patients completed four cycles of neo-adjuvant BCNU + temozolomide. Objective response rate (intention-to-treat) was 42.5% (95% confidence interval 27% to 58%), including two (5%) complete and 15 (37.5%) partial responses. In the eligible population (n=37) the objective response rate was 46%. Nine (24%) patients had stable disease and 14 (35%) had progressive disease. Median PFS and OS were 7.4 and 12.7 months, respectively. Age was the only significant prognostic factor and tumor location (lobar versus multifocal versus corpus callosum) showed a trend. Grade 3-4 toxicities included thrombocytopenia (n=11) and neutropenia (n=7) for both pre- and post-RT chemotherapy. Four patients required platelet transfusions. No patient discontinued treatment because of toxicity. CONCLUSIONS: The combination of BCNU plus temozolomide as neo-adjuvant therapy in inoperable GBM exhibited promising activity with a good safety profile and warrants further evaluation.

Adult↗