Temozolomide: a review of its discovery, chemical properties, pre-clinical development and clinical trials

Health-related quality of life in patients with glioblastoma: a randomised controlled trial

BACKGROUND

A randomised controlled trial of radiotherapy alone versus radiotherapy with concomitant and adjuvant temozolomide for patients with glioblastoma showed that survival was higher for patients assigned combination treatment compared with those assigned standard radiotherapy alone. This paper reports the health-related quality of life (HRQOL) of the patients in this trial.

METHODS

573 patients with newly diagnosed glioblastoma were randomly allocated either radiotherapy alone or radiotherapy and temozolomide. The primary endpoint was survival, and HRQOL was a secondary endpoint. We assessed HRQOL at baseline and at every 3 months during treatment until progression using the European Organisation for Research and Treatment of Cancer (EORTC) quality of life questionnaire core-30 (QLQ-C30) and the EORTC brain cancer module (EORTC BN-20). We calculated changes from baseline score for seven predefined HRQOL measures (fatigue, overall health, social function, emotional function, future uncertainty, insomnia, and communication deficit) and differences between groups for these measures at every time point. The significance of, and proportions of patients with, improved HRQOL scores--defined as a change of 10 points or more--were recorded. This trial is registered on the US National Cancer Institute website http://www.cancer.gov/search/NewClinicalTrials, NCT00006353.

FINDINGS

Baseline questionnaires were available for 490 (86%) patients. Baseline HRQOL scores did not differ between groups. At first follow-up, groups differed only in social functioning, favouring the radiotherapy-only group (mean score 79.0 [SD 3.2] for patients assigned radiotherapy vs 67.4 [2.7] for those assigned radiotherapy and temozolomide; difference between groups 11.6 points [95% CI 3.5-19.7], p=0.0052). Over subsequent assessments, HRQOL was much the same between treatment groups.

INTERPRETATION

Addition of temozolomide during and after radiotherapy for patients with newly diagnosed glioblastoma significantly improved survival without a negative effect on HRQOL.

Drug Insight: temozolomide as a treatment for malignant glioma—impact of a recent trial

Glioblastoma multiforme is the most common primary brain tumor in adults. Until recently, the standard of care consisted of maximal surgical resection followed by external beam radiotherapy. The role of adjuvant chemotherapy for newly diagnosed glioblastoma has been controversial; most of the numerous randomized phase III trials conducted over the past 40 years have failed to show a statistically significant and clinically meaningful survival advantage for patients randomized to the chemotherapy arm. Consequently, the choices of chemotherapeutics for patients with glioblastoma have been limited, and cytotoxic treatment regimens have usually included a nitrosourea. Temozolomide, a relatively new orally administered methylating agent, has demonstrable activity in glioma. A recent trial conducted under the auspices of the European Organization for the Research and Treatment of Cancer (EORTC) and National Cancer Institute of Canada Clinical Trials Group (NCIC CTG) has defined a role for temozolomide in the initial management of glioblastoma. A companion correlative tumor-biology study has identified epigenetic silencing of the promoter of the gene that encodes MGMT (O6-methylguanine-DNA methyltransferase) in tumor specimens as a strong and independent prognostic factor for survival among patients with a newly diagnosed glioblastoma, as well as a predictor of survival benefit from chemoradiotherapy with temozolomide. This review briefly summarizes the development of temozolomide as a therapy for patients with malignant brain tumors, emphasizing recent trials that have established a new standard of care for patients with glioblastoma and speculating on how these advances might influence future therapeutic investigations for malignant primary brain tumors.

Temozolomide in combination with cisplatin in patients with metastatic melanoma: a phase II trial

The present study was designed to assess the efficacy and safety of combination therapy with temozolomide plus cisplatin in patients with metastatic melanoma. Thirty patients with metastatic melanoma were enrolled. Treatment consisted of intravenous cisplatin (75 mg/m) on day 1 and oral temozolomide (200 mg/m) on days 1 to 5, every 4 weeks. Nine patients (30.0%) achieved an objective response, including two complete (6.7%) and seven partial (23.3%) responses. The median response duration was 161 days. The median progression-free and overall survival times were 72 and 120 days, respectively. Myelosuppression and emesis were the primary toxicities. In conclusion, temozolomide combined with cisplatin is an active and safe first-line chemotherapy regimen with acceptable and easily manageable toxicities in patients with metastatic melanoma.

Phase I study of O6-benzylguanine and temozolomide administered daily for 5 days to pediatric patients with solid tumors

PURPOSE

This pediatric phase I trial of O6-benzylguanine (O6BG) and temozolomide (TMZ) on a daily schedule for 5 days, every 28 days was performed to determine the maximum-tolerated dose of TMZ when given with a biologically active dose of O6BG and to define the toxicity profile of the combination in children with solid tumors.

PATIENTS AND METHODS

Patients < or = 21 years old with refractory solid tumors were eligible. O6BG was administered intravenously over 60 minutes daily for 5 days. TMZ was administered orally 30 minutes after completion of each O6BG infusion. Starting doses of O6BG and TMZ were 60 mg/m2/d and 28 mg/m2/d, respectively. O6BG was escalated to 90 and 120 mg/m2/d; TMZ was subsequently escalated to 40, 55, 75, and 100 mg/m2/d. Cycles were repeated every 28 days.

RESULTS

Forty-one patients were enrolled; 32 patients were assessable for toxicity. The combination of O6BG and TMZ was tolerable at TMZ doses less than half of the conventional dose of 200 mg/m2/d. Myelosuppression occurred sporadically at all dose levels and was the dose-limiting toxicity (DLT) at 100 mg/m2/d of TMZ combined with 120 mg/m2/d O6BG. Nonhematologic toxicities were generally mild. Evidence of antitumor activity was observed at 120 mg/m2/d O6BG combined with TMZ doses of 55 mg/m2/d and above.

CONCLUSION

The recommended doses of O6BG administered with TMZ on a 5-day schedule in children are 120 mg/m2/d of O6BG and 75 mg/m2/d of TMZ. Evidence of activity was observed at these doses. Myelosuppression was the DLT.

A phase II trial of temozolomide as a 6-week, continuous, oral schedule in patients with advanced soft tissue sarcoma

BACKGROUND

The objective of this study was to evaluate the activity and toxicity of temozolomide given as an extended schedule in patients with advanced sarcoma.

METHODS

Forty-nine patients with pretreated soft tissue sarcoma (the STS arm) and 18 patients with previously untreated gastrointestinal stromal tumor (the GIST arm) were enrolled onto a 2-arm, multicenter, Phase II study between November 1999 and July 2001. Temozolomide was administered on a 6-week, continuous, oral schedule at a dose of 75 mg/m2 per day in 41 patients and, after an amendment, at a dose of 100 mg/m2 per day in 22 patients.

RESULTS

Among 45 eligible patients in the STS arm, there were 7 partial responses, for an overall response rate of 15.5% (95% confidence interval [95% CI], 5-26%). Responses were seen in 5 of 11 patients who had gynecologic leiomyosarcoma. The median response duration was 12.5 months (range, 3.9-58.0 mos). In 4 patients, response lasted > 1 year, and 2 of those patients remained progression free for > 3 years. The median time to progression was 2.2 months (95% CI, 1.8-2.5 mos), and the median overall survival was 8.1 months (95% CI, 5.6-10.6 mos). Progression-free survival rates at 3 months and 6 months were 39.5% and 26%, respectively. In the GIST arm, no responses were noted. Grade 3-4 granulocytopenia, thrombocytopenia, and anemia were observed in 6 patients, 5 patients, and 7 patients, respectively. The most common nonhematologic toxicities were emesis and fatigue.

CONCLUSIONS

Temozolomide at the extended schedule was tolerated well and had activity in patients with pretreated soft tissue sarcomas, and especially among patients with gynecologic leiomyosarcoma.

Simulating chemotherapeutic schemes in the individualized treatment context: the paradigm of glioblastoma multiforme treated by temozolomide in vivo

A novel patient individualized, spatiotemporal Monte Carlo simulation model of tumor response to chemotherapeutic schemes in vivo is presented. Treatment of glioblastoma multiforme by temozolomide is considered as a paradigm. The model is based on the patient's imaging, histopathologic and genetic data. A discretization mesh is superimposed upon the anatomical region of interest and within each geometrical cell of the mesh the most prominent biological "laws" (cell cycling, apoptosis, etc.) in conjunction with pharmacokinetics and pharmacodynamics information are applied. A good qualitative agreement of the model's predictions with clinical experience supports the applicability of the approach to chemotherapy optimization.

Radiothérapie des glioblastomes : de la radiobiologie à la chimiothérapie concomitante

The prognosis of glioblastoma remains extremely poor. Clinical research has been very active for thirty years, and has explored all the concepts developed in the laboratories of radiobiology. Radiosensitisation of hypoxic tumours, hyperfractioned radiotherapy, external beam radiotherapy plus stereotactic radiosurgery or brachytherapy boost, and intensity modulated radiation therapy failed to improve the results of the treatment of these patients. Concomitant chemoradiotherapy has just obtained a new success in the treatment of glioblastoma. The addition of temozolomide to radiotherapy resulted in a statistically significant survival benefit with minimal acute additional toxicity. The challenge remains to improve clinical outcomes further, and some new research pathways are open.

Chemopotentiation by PARP inhibitors in cancer therapy

Poly(ADP-ribose) polymerases (PARP) constitute a family of enzymes involved in the regulation of many cellular processes such as DNA repair, gene transcription, cell cycle progression, cell death, chromatin functions and genomic stability. Among the 18 members identified so far, PARP-1 and PARP-2 are the only proteins stimulated by DNA strand breaks and implicated in the repair of DNA injury. Therefore, these molecules have been exploited as potential targets for the development of pharmacological strategies to increase the antitumor efficacy of chemotherapeutic agents, which induce DNA damage. PARP inhibitors have been shown to restore sensitivity of resistant tumors to methylating agents or topoisomerase I inhibitors, drugs presently used for the treatment of primary and secondary brain tumors or malignancies refractory to standard chemotherapy. Interestingly, PARP inhibitors may also provide protection from the untoward effects exerted by certain anticancer drugs, which cause oxidative stress and consequent PARP overactivation. The aim of this article is to provide a brief overview of the recent literature on preclinical studies with the specific and potent inhibitors newly synthesized.

Clinical perspectives of PARP inhibitors

Poly(ADP-ribose) polymerase (PARP) activation plays a role in the pathogenesis of various cardiovascular and inflammatory diseases. At the same time, PARP activation is also relevant for the ability of cells to repair injured DNA. Thus, depending on the circumstances, pharmacological inhibitors of PARP may be able to attenuate ischemic and inflammatory cell and organ injury or may be able to enhance the cytotoxicity of antitumor agents. Both aspects of the "double-edged sword" role of PARP can be exploited for the experimental therapy of disease. As several classes of PARP inhibitors move towards clinical development, or have already entered the stage of clinical trials, we expect that in the upcoming few years, clinical proof of PARP inhibitors' therapeutic effect will be obtained in human disease. In the current short overview, we summarize the pros and cons and challenges with respect to the clinical use of PARP inhibitors, the expected clinical outcomes and potential risks. It appears that on the cytoprotective aspect of PARP, acute, life-threatening diseases (myocardial infarction, cardiopulmonary bypass in high-risk patients, and other, severe forms of ischemia-reperfusion to other organs including stroke and thoracoabdominal aneurysm repair) may represent some of the prime development indications. In the context of inhibition of DNA repair, combination of PARP inhibitors with certain antitumor agents (for example temozolomide) in patients with tumors with extremely poor prognosis are expected to provide the initial clinical results. Development of PARP inhibitors for additional indications (e.g. chronic use for the therapy of neurodegeneration and neuroinflammation, or diabetic complications) may be more challenging because of the unknown potential long-term side effects of PARP inhibitors.

O6-methylguanine-DNA methyltransferase, O6-benzylguanine, and resistance to clinical alkylators in pediatric primary brain tumor cell lines

PURPOSE

Primary brain tumors are the leading cause of cancer death in children. Our purpose is (a) to assess the contribution of the DNA repair protein O6-methylguanine-DNA methyltransferase (MGMT) to the resistance of pediatric brain tumor cell lines to clinical alkylating agents and (b) to evaluate variables for maximal potentiation of cell killing by the MGMT inhibitor O6-benzylguanine, currently in clinical trials. Few such data for pediatric glioma lines, particularly those from low-grade tumors, are currently available.

EXPERIMENTAL DESIGN

We used clonogenic assays of proliferative survival to quantitate cytoxicity of the chloroethylating agent 1,3-bis(2-chloroethyl)-1-nitrosourea (BCNU) and the methylating agent temozolomide in 11 glioma and five medulloblastoma lines. Twelve lines are newly established and characterized here, nine of them from low-grade gliomas including pilocytic astrocytomas.

RESULTS

(a) MGMT is a major determinant of BCNU resistance and the predominant determinant of temozolomide resistance in both our glioma and medulloblastoma lines. On average, O(6)-benzylguanine reduced LD10 for BCNU and temozolomide, 2.6- and 26-fold, respectively, in 15 MGMT-expressing lines. (b) O6-Benzylguanine reduced DT (the threshold dose for killing) for BCNU and temozolomide, 3.3- and 138-fold, respectively. DT was decreased from levels higher than, to levels below, clinically achievable plasma doses for both alkylators. (c) Maximal potentiation by O6-benzylguanine required complete and prolonged suppression of MGMT.

CONCLUSIONS

Our results support the use of O6-benzylguanine to achieve full benefit of alkylating agents, particularly temozolomide, in the chemotherapy of pediatric brain tumors.

New Treatment Approaches in Primary Central Nervous System Lymphoma

A major advance in the treatment of primary central nervous system lymphoma (PCNSL) was made when the addition of chemotherapy to radiotherapy was shown to improve patient survival significantly. However, few chemotherapeutic agents are able to cross the blood-brain barrier. New therapeutic approaches in PCNSL are based on: the treatment of systemic non-Hodgkin's lymphomas with monoclonal antibodies and intensive chemotherapy followed by hematopoietic stem cell rescue, new chemotherapeutic agents with central nervous system penetration, or blood-brain barrier disruption to enhance drug delivery to the brain. This article discusses the rationale and results of these innovative approaches.

1-Methyl-3H-pyrazolo[1,2-a]benzo[1,2,3,4]tetrazin-3-ones. Design, synthesis, and biological activity of new antitumor agents

1-Methylpyrazolo[1,2-a]benzo[1,2,3,4]tetrazin-3-ones 4, synthesized in good to excellent yields, were designed as novel alkylating agents because of their peculiar chemical behavior. All derivatives showed antiproliferative activity against more than 50 types of tumor cell lines with GI(50) reaching sub-micromolar values. SAR studies revealed that the presence of a chlorine atom is well-tolerated in both positions 8 and 9, whereas in the case of the methyl group, switching from the 8 to the 9 position gives rise to the most active compound of the series, 4g, either for the number of cell lines inhibited and for selectivity against leukaemia and renal cancer subpanels. COMPARE and 3D-MIND computations indicate, for compounds 4, an activity profile analogous to rifamycins and cytidine analogues.

Synthesis and antiproliferative activity of [1,2,3,5]tetrazino[5,4-a]indoles, a new class of azolo-tetrazinones

Eight derivatives of the new ring system [1,2,3,5]tetrazino[5,4-a]indole-4-one 7, were synthesised in good yields by reaction of 2-diazoindoles with alkyl or aryl isocyanates. Compounds 7 were screened at National Cancer Institute (NCI) for their activity against a panel of approximately 60 human tumour cell lines. Some of them showed antiproliferative activity having generally GI50 in the micromolar range. The most sensitive cell lines were SF-295, SNB-75 and SF-539 of the CNS cancer sub-panel, SR of the leukaemia sub-panel, UACC-62 of the melanoma sub-panel and OVCAR-4 of the ovarian cancer sub-panel.

Temozolomide Pharmacodynamics in Patients with Metastatic Melanoma: DNA Damage and Activity of Repair EnzymesO6-Alkylguanine Alkyltransferase and Poly(ADP-Ribose) Polymerase-1

PURPOSE

Temozolomide, a DNA methylating agent used to treat melanoma, induces DNA damage, which is repaired by O6-alkylguanine alkyltransferase (ATase) and poly(ADP-ribose) polymerase-1 (PARP-1)-dependent base excision repair. The current study was done to define the effect of temozolomide on DNA integrity and relevant repair enzymes as a prelude to a phase I trial of the combination of temozolomide with a PARP inhibitor.

EXPERIMENTAL DESIGN

Temozolomide (200 mg/m2 oral administration) was given to 12 patients with metastatic malignant melanoma. Peripheral blood lymphocytes (PBL) were analyzed for PARP activity, DNA single-strand breakage, ATase levels, and DNA methylation. PARP activity was also measured in tumor biopsies from 9 of 12 patients and in PBLs from healthy volunteers.

RESULTS

Temozolomide pharmacokinetics were consistent with previous reports. Temozolomide therapy caused a substantial and sustained elevation of N7-methylguanine levels, a modest and sustained reduction in ATase activity, and a modest and transient increase in DNA strand breaks and PARP activity in PBLs. PARP-1 activity in tumor homogenates was variable (828 +/- 599 pmol PAR monomer/mg protein) and was not consistently affected by temozolomide treatment.

CONCLUSIONS

The effect of temozolomide reported here are consistent with those documented in previous studies with temozolomide and similar drug, dacarbazine, demonstrating that a representative patient population was investigated. Furthermore, PARP activity was not inhibited by temozolomide treatment and this newly validated pharmacodynamic assay is therefore suitable for use in a proof-of-principle phase I trial a PARP-1 inhibitor in combination with temozolomide.

Poly(ADP-ribose) polymerase inhibitors as potential chemotherapeutic agents

PARP [poly(ADP-ribose) polymerase] activity is up-regulated by binding to DNA strand breaks and its association with DNA repair is well documented. Many anticancer therapies work by inducing breaks in DNA, if unrepaired these can lead to cell death. As PARP promotes DNA repair there is a strong rational to suggest that its inhibition may increase the efficiency of certain cytotoxic treatments. This review discusses the advances made in PARP inhibitor design and the mechanism by which they enhance anti-tumour therapies.

Apurinic endonuclease activity in adult gliomas and time to tumor progression after alkylating agent-based chemotherapy and after radiotherapy

PURPOSE

Apurinic/apyrimidinic endonuclease (Ap endo) is a key DNA repair enzyme that cleaves DNA at cytotoxic abasic sites caused by alkylating agents and radiation. We have observed that human glioma cells deficient in Ap endo activity are hypersensitive to clinically used alkylators (Silber et al., Clin Cancer Res 2002;8:3008.). Here we examine the association of glioma Ap endo activity with clinical response after alkylating agent-based chemotherapy or after radiotherapy.

EXPERIMENTAL DESIGN

Cox proportional hazards regression models were used to analyze the relationship of Ap endo activity with time to tumor progression (TTP).

RESULTS

In a univariate model with Ap endo activity entered as a continuous variable, the hazard ratio (HR) for progression after alkylator therapy in 30 grade III gliomas increased by a factor of 1.061 for every 0.01 increase in activity (P = 0.013). Adjusting for age, gender, extent of resection, and prior treatment strengthened slightly the association (HR = 1.094; P = 0.003). Similarly, the HR for progression after radiotherapy in 44 grade II and III tumors increased by a factor of 1.069 (P = 0.008). Adjusting for the aforementioned variables had little effect on the association. In contrast, we observed no association between activity and TTP in grade IV gliomas after either alkylator therapy in 34 tumors or radiotherapy in 26 tumors.

CONCLUSIONS

Our data suggest that Ap endo activity mediates resistance to alkylating agents and radiation and may be a useful predictor of progression after adjuvant therapy in a subset of gliomas.

Poly(ADP-ribose) Polymerase Activity Prevents Signaling Pathways for Cell Cycle Arrest after DNA Methylating Agent Exposure

Mouse fibroblasts, deficient in DNA polymerase beta, are hypersensitive to monofunctional DNA methylating agents such as methyl methanesulfonate (MMS). Both wild-type and, in particular, repair-deficient DNA polymerase beta null cells are highly sensitized to the cytotoxic effects of MMS by 4-amino-1,8-naphthalimide (4-AN), an inhibitor of poly(ADP-ribose) polymerase (PARP) activity. Experiments with synchronized cells suggest that exposure during S-phase of the cell cycle is required for the 4-AN effect. 4-AN elicits a similar extreme sensitization to the thymidine analog, 5-hydroxymethyl-2'-deoxyuridine, implicating the requirement for an intermediate of DNA repair. In PARP-1-expressing fibroblasts treated with a combination of MMS and 4-AN, a complete inhibition of DNA synthesis is apparent after 4 h, and by 24 h, all cells are arrested in S-phase of the cell cycle. Continuous incubation with 4-AN is required to maintain the cell cycle arrest. Caffeine, an inhibitor of the upstream checkpoint kinases ATM (ataxia telangiectasia-mutated) and ATR (ATM and Rad3-related), has no effect on the early inhibition of DNA synthesis, but cells are no longer able to maintain the block after 8 h. Instead, the addition of caffeine leads to arrest of cells in G(2)/M rather than S-phase after 24 h. Analysis of signaling pathways in cell extracts reveals an activation of Chk1 after treatment with MMS and 4-AN, which can be suppressed by caffeine. Our results suggest that inhibition of PARP activity results in sensitization to MMS through maintenance of an ATR and Chk1-dependent S-phase checkpoint.

Radiotherapy plus concomitant and adjuvant temozolomide for glioblastoma

BACKGROUND

Glioblastoma, the most common primary brain tumor in adults, is usually rapidly fatal. The current standard of care for newly diagnosed glioblastoma is surgical resection to the extent feasible, followed by adjuvant radiotherapy. In this trial we compared radiotherapy alone with radiotherapy plus temozolomide, given concomitantly with and after radiotherapy, in terms of efficacy and safety.

METHODS

Patients with newly diagnosed, histologically confirmed glioblastoma were randomly assigned to receive radiotherapy alone (fractionated focal irradiation in daily fractions of 2 Gy given 5 days per week for 6 weeks, for a total of 60 Gy) or radiotherapy plus continuous daily temozolomide (75 mg per square meter of body-surface area per day, 7 days per week from the first to the last day of radiotherapy), followed by six cycles of adjuvant temozolomide (150 to 200 mg per square meter for 5 days during each 28-day cycle). The primary end point was overall survival.

RESULTS

A total of 573 patients from 85 centers underwent randomization. The median age was 56 years, and 84 percent of patients had undergone debulking surgery. At a median follow-up of 28 months, the median survival was 14.6 months with radiotherapy plus temozolomide and 12.1 months with radiotherapy alone. The unadjusted hazard ratio for death in the radiotherapy-plus-temozolomide group was 0.63 (95 percent confidence interval, 0.52 to 0.75; P<0.001 by the log-rank test). The two-year survival rate was 26.5 percent with radiotherapy plus temozolomide and 10.4 percent with radiotherapy alone. Concomitant treatment with radiotherapy plus temozolomide resulted in grade 3 or 4 hematologic toxic effects in 7 percent of patients.

CONCLUSIONS

The addition of temozolomide to radiotherapy for newly diagnosed glioblastoma resulted in a clinically meaningful and statistically significant survival benefit with minimal additional toxicity.

Temozolomide in the treatment of solid tumours: current results and rationale for dosing/scheduling

This review examines the current evidence for the use of temozolomide in the treatment of solid tumours. The possible molecular and clinical advantages of temozolomide are identified and the molecular mechanism of temozolomide resistance is explored. Attempts to maximise efficacy have led to manipulation of both dosage and drug scheduling and the evidence for the various strategies is reviewed. Finally, the potential role of combination therapy is considered.

Synthesis and antitumor activity of methyltriazene prodrugs simultaneously releasing DNA-methylating agents and the antiresistance drug O(6)-benzylguanine

Active resistance of tumor cells against DNA alkylating agents arises by the production of high levels of the DNA repair protein O(6)-alkylguanine-DNA alkyltransferase (AGT). This resistance during treatment with, for example, the anticancer agent temozolomide can be reversed by administration of O(6)-benzylguanine, a purine that transfers its benzyl group to AGT and irreversibly inactivates it. Stimulated by the favorable therapeutic properties of temozolomide we designed and synthesized DNA-methylating triazenes built on the antiresistance benzylguanine ring system. The condensation reaction between 2-nitrosopurines and acylhydrazines proved to be very suitable to prepare acylated methyltriazenes. Fine-tuning of the release rate of both the methylating agent (diazomethane) and of O(6)-benzylguanine was accomplished by variation of the hydrolysis-sensitive acyl substituent in 5. Hydrolysis studies were performed with (1)H NMR and revealed that the p-nitrophenyl substituted triazene 26 showed an optimal hydrolysis rate (t(1/2) = 23 min) and almost 100% selectivity for the desired fragmentation route. In vitro antitumor studies in the 60 human tumor cell line panel of the National Cancer Institute confirmed the superior properties of p-nitrophenyl-protected methyl triazene 26, showing mean IC(50) values of 10 microM compared to 100 microM for temozolomide. In analogy with temozolomide, triazene 26 showed however low preference for each of the cancer subpanels, with IC(50) values between 8 and 14 microM.

The effect of temozolomide-based chemotherapy in patients with cerebral metastases from melanoma

Cerebral metastases from melanoma are correlated with a poor prognosis. Temozolomide is an oral alkylating agent that can cross the blood-brain barrier and in phase II and III trials, patients with advanced metastatic melanoma achieved overall response rates of 13 to 21%. The present study evaluated the efficacy and toxicity of temozolomide-based chemotherapy in patients with cerebral metastases from melanoma. Twenty-five patients (median age 48 years) with histologically confirmed stage IV melanoma and cerebral metastases treated with temozolomide-based chemotherapy. 10 patients received temozolomide plus docetaxel, nine patients temozolomide plus cisplatin and six patients temozolomide as single agent. Six patients achieved an objective response (24%). All responses were partial. The disease was stable in five patients (20%) and 13 patients progressed (52%). The median response duration was 6.9 months (range 1.8 to 16 months). The median time to progression (TTP) for all patients was 2 months, compared with a median TTP of 3.9 months, among responders and a median TTP of 1.8 months, for patients who remained stable or progressed (P<0.0001). The median survival time for the entire patient population was 4.7 months. The median survival for responders was 5.5 months and for non-responders was 3.6 months. The difference was statistically significant (P<0.05). The toxicity was mild. The most frequently reported adverse event were myelotoxicity and nausea and vomiting. Four patients developed grade 3/4 leukopenia, two grade 4 neutropenia, and one patient developed grade 3 thrombocytopenia. There was no treatment discontinuation caused by toxicity. Temozolomide-based chemotherapy may have a role in patients with cerebral metastases from melanoma. Further exploration is required. Toxicity was manageable.

Engineering 3-alkyltriazenes to block bcr-abl kinase: a novel strategy for the therapy of advanced bcr-abl expressing leukemias

Recently, within the framework of a new strategy termed "combi-targeting," we designed ZRCM5 to contain a 2-phenylaminopyrimidopyridine moiety targeted to bcr-abl kinase and a triazene tail capable of generating a methyldiazonium species upon hydrolysis. The ability of ZRCM5 to block tyrosine kinase activity was tested in a short 10 min exposure ELISA involving isolated bcr-abl kinase and Western blotting assays. The results showed that: (a) ZRCM5 was hydrolyzed with a half-life of 27 min in cell culture media, (b) it blocked bcr-abl autophosphorylation in promyeloblastic leukemia K562 cells in a dose-dependent manner (IC(50)=14.01 microM) and (c) it induced dose-dependent levels of DNA strand breaks. In contrast, temozolomide (TEM), a clinical DNA damaging triazene capable of generating, like ZRCM5, a methyldiazonium species, could neither block bcr-abl tyrosine kinase activity in isolated enzyme nor in whole cell autophosphorylation assays. In cells expressing varied levels of bcr-abl, ZRCM5 was consistently more potent than TEM. The significant potency of ZRCM5 against the leukemia cells was attributed to its ability to simultaneously to block bcr-abl and related DNA repair activity while inducing significant DNA lesions in bcr-abl expressing leukemia cells. Further studies are ongoing to increase the affinity of ZRCM5 with the purpose of further enhancing its potency in bcr-abl expressing cells.

Economic evaluation of temozolomide in the treatment of recurrent glioblastoma multiforme

BACKGROUND

Temozolomide (TMZ) is an oral alkylating agent with demonstrated efficacy as therapy for glioblastoma multiforme (GBM) and anaplastic astrocytoma. TMZ has widely replaced the procarbazine, lomustine plus vincristine (PCV) combination for the treatment of malignant brain tumours as a result of its oral administration and favourable toxicity profile.

OBJECTIVES

This study had three related aims. First, the cost effectiveness of TMZ (from the Finnish healthcare payer perspective) was compared with PCV in patients with GBM that had relapsed after primary treatment with surgery and radiotherapy. Second, the probability that TMZ is cost effective, compared with PCV, was estimated at different societal willingness-to-pay levels. Third, the value of new information for reducing the uncertainty related to the choice of treatment between TMZ and PCV was evaluated.

METHODS

The cost effectiveness of TMZ and PCV was evaluated using a decision-modelling approach. Incremental cost-effectiveness ratios (ICERs) for cost per gained life-month, progression-free life-month and QALY were calculated. Various information sources were used to acquire parameter values for the model. The efficacy information of both treatments was derived from the medical literature, quality-of-life (QOL) estimates were gathered from Finnish neuro-oncologists using visual analogue scale methods, and data on the use of healthcare resources were collected from hospital databases. The exact prices for resource use were gained from the list of Finnish health service unit costs (year 2001 prices). The model was analysed using second-order Monte Carlo simulation. The value of new information on reducing uncertainty was analysed using the expected value of perfect information (EVPI) approach.

RESULTS

According to the derived ICERs, 1 extra life-month gained with TMZ costs euro2367, 1 extra progression-free life-month costs euro2165, and 1 extra QALY costs euro32 471, compared with PCV, in the treatment of GBM. The probability of TMZ being the most cost-effective choice of treatment was >60% for all levels of willingness to pay >euro5000 per gained life-month. The respective probabilities were >75% for all levels of willingness to pay >euro10 000 per gained progression-free life-month and about 85% for all levels of willingness to pay >euro20 000 per gained quality-adjusted life-month. According to EVPI analysis, future research would potentially be cost effective if the costs of research were euro4.1 million (maximum).

CONCLUSIONS

On the basis of this Finnish analysis, TMZ has a high probability of being more cost effective than PCV for patients with GBM. The addition of QOL aspects to the prolonging of survival increases the probability further.

The Werner syndrome protein confers resistance to the DNA lesions N3-methyladenine and O6-methylguanine: implications for WRN function

The Werner syndrome (WS) protein (WRN), a DNA helicase/exonuclease, is required for genomic stability and avoidance of cancer. Current evidence suggests that WRN is involved in the resolution of stalled and/or collapsed replication forks. This function is indicated, in part, by replication defects in WS cells and by hypersensitivity to agents causing major structural aberrations in DNA that block replication. We show here that antisense suppression of WRN in two human glioma cell lines reproduces hallmarks of the drug cytotoxicity profile of WS cells, namely, hypersensitivity to 4-nitroquinoline 1-oxide, camptothecin and hydroxyurea. We also show that antisense-treated cells are hypersensitive to methyl-lexitropsin, a site-specific alkylating agent that produces mainly N3-methyladenine, a cytotoxic and replication-blocking lesion. Antisense-treated cells are hypersensitive to O(6)-methylguanine adducts as well, but only when repair by O(6)-methylguanine-DNA methyltransferase is lacking. Our results illustrate the drug sensitivity caused by deficiency of WRN in a uniform genetic background. They extend the WRN DNA damage sensitivity spectrum to methyl base adducts that can result in blocked replication, and suggest that WRN may be required for resumption of processive replication when incomplete repair of DNA damage leaves blocking lesions at forks. The evidence that highly disparate lesions fall within the purview of WRN, and that abrogating DNA repair can reveal dependence on WRN, suggests that WRN may protect the genome from the lethal, mutagenic and carcinogenic effects of widely diverse DNA damage arising from endogenous processes and environmental agents.

N3-methyladenine induces early poly(ADP-ribosylation), reduction of nuclear factor-kappa B DNA binding ability, and nuclear up-regulation of telomerase activity

Methylation of N3-adenine represents a novel pharmacological strategy for the treatment of resistant tumors. However, little is known about the biochemical pathways involved in cell death induced by N3-methyladenine. In the present study, we show that MeOSO(2) (CH(2))(2)-lexitropsin (Me-Lex), a compound generating almost exclusively N3-methyladenine (>99%), provoked a burst of poly(ADP-ribosylation) and loss of mitochondrial membrane potential in leukemia cells. These events were followed by a marked decrease in nuclear poly(ADP-ribose) polymerase-1 (PARP-1) expression and nuclear factor-kappaB (NF-kappaB) activity. Moreover, DNA damage generated by N3-methyladenine induced a marked decrease in telomerase in the cytosol that was accompanied by a transient up-regulation of activity in the nucleus, as a consequence of nuclear translocation of telomerase in response to genotoxic damage. PARP-1 inhibition blocked ADP-ribose polymer formation, preserved mitochondrial membrane integrity, and counteracted the reduction of NF-kappaB activity, thus preventing the appearance of necrosis. On the other hand, because PARP-1 is a component of the base excision repair (BER), the combination of Me-Lex + PARP-1 inhibitor triggered apoptosis as a result of disruption of BER process. In conclusion, the present study provides new insight into the cellular response to N3-adenine-selective methylating agents that can be exploited for the treatment of tumors unresponsive to classical wide-spectrum methylating agents. Moreover, the results underline the central and paradoxical role of PARP-1 in cell death induced by N3-methyladenine: effector of necrosis and coordinator of methylpurine repair.

Temozolomide and interferon alpha 2b in metastatic melanoma stage IV

BACKGROUND

A multicentre, centrally randomized, open-labelled study with temozolomide and interferon (IFN)-alpha 2b was carried out to study the therapeutic effect in patients with metastatic melanoma stage IV.

OBJECTIVES

The response rate, efficacy, side-effects, reasons for discontinuation of therapy and survival rate of 47 patients treated with temozolomide in combination with two different dosing regimens of IFN-alpha 2b were documented.

PATIENTS/METHODS

Twenty-nine male and 18 female patients (mean age 57.6 years, range 34-74) were centrally randomized to two different arms: 20 patients received a treatment schedule with temozolomide 150 mg m(-2) on days 1-5 orally every 28 days in combination with IFN-alpha 2b 10 MIU m(-2) every other day and 27 patients received temozolomide 150 mg m(-2) on days 1-5 every 28 days in combination with IFN-alpha 2b in a fixed dose of 10 MIU every other day.

RESULTS

We observed an overall response rate of 27.6% comprising five complete remissions (10.6%: one patient group A, four patients group B), in two of these five patients at the last follow-up in the study (4.3%, both in group B); and eight partial remissions (17%: six patients in group A, two patients in group B), in three of these eight patients at the last follow-up in the study (6.4%, two patients in group A, one patient in group B). Three patients showed stable disease (6.4%: one patient in group A, two patients in group B). Mean survival was 14.5 months [95% confidence interval (CI) 10-19] with no significant differences between treatment groups. However, there was a significant correlation with response after three cycles (log rank test, P < 0.03). Within the 32 patients who completed at least three cycles of therapy, seven patients (three in group A and four in group B) with a partial or complete response showed a significantly better mean survival of 30.6 months (95% CI 19.1-42) compared with 25 patients who did not respond (13.7 months 95% CI 9.2-18.3). In total, patients with at least one complete remission showed the longest survival (37.1 months 95% CI 26.3-47.9), followed by patients with at least one partial response (17.4 95% CI 10.9-23.9). Major side-effects of the treatment were nausea, vomiting, headache, leucopenia, thrombopenia, elevation of liver function parameters and neurological symptoms. In five patients, the side-effects led to a discontinuation of treatment: neurological symptoms (two patients), sepsis (one patient), brain haemorrhage (one patient) and exanthema (one patient). There were no treatment-related deaths.

CONCLUSIONS

The combination of temozolomide and IFN-alpha 2b can easily be administered and shows tolerable toxicity. When an objective response occurs after three cycles, it indicates a significant survival advantage.

Role of autophagy in temozolomide-induced cytotoxicity for malignant glioma cells

Autophagy is originally named as a process of protein recycling. It begins with sequestering cytoplasmic organelles in a membrane vacuole called autophagosome. Autophagosomes then fuse with lysosomes, where the materials inside are degraded and recycled. To date, however, little is known about the role of autophagy in cancer therapy. In this study, we present that temozolomide (TMZ), a new alkylating agent, inhibited the viability of malignant glioma cells in a dose-dependent manner and induced G2/M arrest. At a clinically achievable dose (100 microM), TMZ induced autophagy, but not apoptosis in malignant glioma cells. After the treatment with TMZ, microtubule-associated protein light-chain 3 (LC3), a mammalian homologue of Apg8p/Aut7p essential for amino-acid starvation-induced autophagy in yeast, was recruited on autophagosome membranes. When autophagy was prevented at an early stage by 3-methyladenine, a phosphatidylinositol 3-phosphate kinase inhibitor, not only the characteristic pattern of LC3 localization, but also the antitumor effect of TMZ was suppressed. On the other hand, bafilomycin A1, a specific inhibitor of vacuolar type H(+)-ATPase, that prevents autophagy at a late stage by inhibiting fusion between autophagosomes and lysosomes, sensitized tumor cells to TMZ by inducing apoptosis through activation of caspase-3 with mitochondrial and lysosomal membrane permeabilization, while LC3 localization pattern stayed the same. These results indicate that TMZ induces autophagy in malignant glioma cells. Application of an autophagy inhibitor that works after the association of LC3 with autophagosome membrane, such as bafilomycin A1, is expected to enhance the cytotoxicity of TMZ for malignant gliomas.

The treatment of brain metastases in melanoma patients

The incidence of central nervous system (CNS) metastases in patients with melanoma ranges from 10% to 40% in clinical studies and is even higher in autopsy series with as many as two-thirds of patients with metastatic melanoma having CNS involvement. Treatment options for patients with cerebral metastases are limited and depend largely on the number and the size of the lesions and on the extracranial extension of metastatic disease. This report gives the results of different treatment modalities in patients with melanoma metastases to the brain. As data from prospective randomized studies are lacking, the general recommendations based on clinical series reports are: (i) the combination of surgery and whole-brain radiotherapy (WBRT) is superior to WBRT alone for the treatment of single brain metastasis in patients with limited or absent systemic disease and good neurological condition. (ii) Radio surgery, alone or in conjunction with WBRT, yields results which are comparable to those reported after surgery followed by WBRT, provided that the lesion's diameter does not exceed 3 cm. With the use of WBRT after surgery or radio surgery the local control seems better (with the combined approach), but the overall survival does not improve. (iii) WBRT alone or in combination with chemotherapy is the treatment of choice in patients with single brain metastasis not amenable to surgery or radio surgery, with an active systemic disease, and in patients with multiple brain metastases. Chemotherapy may be also offered to patients with a good performance status, or after recurrence to local therapy.

Synthesis and characterization of a series of 1-methyl-4-[2-aryl-1-diazenyl]piperazines and a series of ethyl 4-[2-aryl-1-diazenyl]-1-piperazinecarboxylates

1-Methylpiperazine was coupled with a series of diazonium salts to afford the 1-methyl-4-[2-aryl-1-diazenyl]piperazines (2), a new series of triazenes, which have been characterized by 1H and 13C NMR spectroscopy, IR spectroscopy, and elemental analysis. Assignment of the chemical shifts to specific protons and carbons in the piperazine ring was facilitated by comparison with the chemical shifts in the model compounds piperazine and 1-methylpiperazine and by a HETCOR experiment with the p-tolyl derivative (2i). A DEPT experiment with 1-methylpiperazine (6) was necessary to distinguish the methyl and methylene groups in 6, and a HETCOR spectrum of 6 enabled the correlation of proton and carbon chemical shifts. Line broadening of the signals from the ring methylene protons is attributed to restricted rotation around the N2-N3 bond of the triazene moiety in 2. The second series of triazenes, the ethyl 4-[2-phenyl-1-diazenyl]-1-piperazinecarboxylates (3), have been prepared by similar diazonium coupling to ethyl 1-piperazinecarboxylate and were similarly characterized. The chemical shifts of the piperazine ring protons are much closer together in series 3 than in series 2, resulting in distortion of the multiplets for these methylenes. It was noticed that the difference between these chemical shifts in 3 exhibited a linear free energy relationship with the Hammett substituent constants for the substituents in the aryl ring. Key words: triazene, piperazine, diazonium coupling, NMR, HETCOR, linear free energy relationship.

Plasma and Cerebrospinal Fluid Population Pharmacokinetics of Temozolomide in Malignant Glioma Patients

PURPOSE

Scarce information is available on the brain penetration of temozolomide (TMZ), although this novel methylating agent is mainly used for the treatment of malignant brain tumors. The purpose was to assess TMZ pharmacokinetics in plasma and cerebrospinal fluid (CSF) along with its inter-individual variability, to characterize covariates and to explore relationships between systemic or cerebral drug exposure and clinical outcomes.

EXPERIMENTAL DESIGN

TMZ levels were measured by high-performance liquid chromatography in plasma and CSF samples from 35 patients with newly diagnosed or recurrent malignant gliomas. The population pharmacokinetic analysis was performed with nonlinear mixed-effect modeling software. Drug exposure, defined by the area under the concentration-time curve (AUC) in plasma and CSF, was estimated for each patient and correlated with toxicity, survival, and progression-free survival.

RESULTS

A three-compartment model with first-order absorption and transfer rates between plasma and CSF described the data appropriately. Oral clearance was 10 liter/h; volume of distribution (V(D)), 30.3 liters; absorption constant rate, 5.8 h(-1); elimination half-time, 2.1 h; transfer rate from plasma to CSF (K(plasma-->CSF)), 7.2 x 10(-4)h(-1) and the backwards rate, 0.76 h(-1). Body surface area significantly influenced both clearance and V(D), and clearance was sex dependent. The AUC(CSF) corresponded to 20% of the AUC(plasma). A trend toward an increased K(plasma-->CSF) of 15% was observed in case of concomitant radiochemotherapy. No significant correlations between AUC in plasma or CSF and toxicity, survival, or progression-free survival were apparent after deduction of dose-effect.

CONCLUSIONS

This is the first human pharmacokinetic study on TMZ to quantify CSF penetration. The AUC(CSF)/AUC(plasma) ratio was 20%. Systemic or cerebral exposures are not better predictors than the cumulative dose alone for both efficacy and safety.

Dose-dense regimen of temozolomide given every other week in patients with primary central nervous system tumors

BACKGROUND

Temozolomide has shown activity and limited toxicity in patients with primary brain tumors at doses of 150-200 mg/m(2)/day on days 1-5 every 4 weeks. In this study, a new alternative dose-dense regimen of temozolomide was explored in patients with recurrent brain tumors.

PATIENTS AND METHODS

In this study, we evaluated the safety, dose-limiting toxicity, maximum tolerated dose, recommended dose and activity of temozolomide given on days 1-3 and 14-16 every 28 days (one cycle). The starting daily dose was 200 mg/m(2) in a group of at least six patients, with subsequent increments of 50 mg/m(2) in groups of at least 12 patients until unacceptable toxicity was reached. Oral ondansetron (8 mg) was given 1 h prior to temozolomide administration. McDonald's criteria were used to evaluate antitumor activity.

RESULTS

Seventy patients with brain tumors entered this study. The median number of prior chemotherapy treatments was two (range 1-3). Patients were assigned to one of four groups to receive temozolomide at daily doses of 200 (seven patients), 250 (13 patients), 300 (38 patients) and 350 mg/m(2)/day (12 patients). The absence of dose-limiting toxicity at cycle 1 led us to establish dose recommendations based on toxicity after repeated cycles. A total of 23, 72, 192 and 83 cycles were given at daily doses of 200, 250, 300 and 350 mg/m(2), respectively. Grade 3-4 thrombocytopenia was observed in 0/7, 1/13, 5/38 and 4/12 patients treated at doses of 200, 250, 300 and 350 mg/m(2)/day, respectively. Grade 3-4 neutropenia was observed in 1/7, 0/13, 3/38 and 4/12 patients treated with 200, 250, 300 and 350 mg/m(2)/day temozolomide, respectively. At a dose of 350 mg/m(2), sustained grade 2-3 thrombocytopenia did not allow treatment to be resumed at day 14 in >40% of patients, and this dose was considered to be the maximum tolerated dose. Thus, a dose of 300 mg/m(2)/day that was associated with <20% treatment delay due to sustained hematological toxicity was considered as the recommended dose. Objective responses were reported in 13 patients.

CONCLUSIONS

Temozolomide can be given safely using a dose-dense regimen of 300 mg/m(2)/day for 3 consecutive days every 2 weeks in patients with recurrent brain tumors.

The combi-targeting concept: intracellular fragmentation of the binary epidermal growth factor (EGFR)/DNA targeting “combi-triazene” SMA41

We have designed a novel tumor targeting strategy that consists of designing molecules termed "combi-molecules" or TZ-I to be masked forms of multiple antitumor agents. One such molecule SMA41, the TZ-I prototype, has been shown to target the epidermal growth factor receptor (EGFR) and to degrade under physiological conditions to give SMA52 (I) (an inhibitor of EGFR) and methyldiazonium (TZ) (a DNA alkylating species). While the antiproliferative advantages of this novel binary targeting strategy have now been demonstrated, the exact subcellular localization of the degradation products released from SMA41 remained elusive. Here we exploited the fluorescence properties of SMA52 to study its release from SMA41 and its subcellular distribution. Further, using 14C-labeled SMA41, we determined the distribution of the methydiazonium within subcellular macromolecules (DNA, RNA, protein). The results showed that SMA41 degraded to SMA52 in the carcinoma of the vulva cell line A431 with a half-life of 11min. The latter compound was primarily distributed in the perinuclear region. At equimolar concentrations, higher levels of SMA52 were observed when released from SM41 than when the cells were directly exposed to SMA52, indicating that the combi-molecular approach may offer a transport advantage to the released bioactive species. Radioactivity associated with SMA41 3-[ 14C]-methyl group was distributed throughout DNA, RNA, and protein, the latter macromolecule being the most alkylated. The results suggest that SMA41 (TZ-I) may diffuse into the cells, break down into two species: SMA52 (I) concentrated in the perinuclear region and methyldiazonium (TZ) that diffuses in all intracellular organelles and unspecifically alkylates RNA, protein, and nuclear DNA.

Anticancer chemosensitization and radiosensitization by the novel poly(ADP-ribose) polymerase-1 inhibitor AG14361

BACKGROUND

Poly(ADP-ribose) polymerase-1 (PARP-1) facilitates the repair of DNA strand breaks. Inhibiting PARP-1 increases the cytotoxicity of DNA-damaging chemotherapy and radiation therapy in vitro. Because classical PARP-1 inhibitors have limited clinical utility, we investigated whether AG14361, a novel potent PARP-1 inhibitor (inhibition constant <5 nM), enhances the effects of chemotherapy and radiation therapy in human cancer cell cultures and xenografts.

METHODS

The effect of AG14361 on the antitumor activity of the DNA alkylating agent temozolomide, topoisomerase I poisons topotecan or irinotecan, or x-irradiation or gamma-radiation was investigated in human cancer cell lines A549, LoVo, and SW620 by proliferation and survival assays and in xenografts in mice by tumor volume determination. The specificity of AG14361 for PARP-1 was investigated by microarray analysis and by antiproliferation and acute toxicity assays in PARP-1-/- and PARP-1+/+ cells and mice. After intraperitoneal administration, the concentration of AG14361 was determined in mouse plasma and tissues, and its effect on PARP-1 activity was determined in tumor homogenates. All statistical tests were two-sided.

RESULTS

AG14361 at 0.4 micro M did not affect cancer cell gene expression or growth, but it did increase the antiproliferative activity of temozolomide (e.g., in LoVo cells by 5.5-fold, 95% confidence interval [CI] = 4.9-fold to 5.9-fold; P =.004) and topotecan (e.g., in LoVo cells by 1.6-fold, 95% CI = 1.3-fold to 1.9-fold; P =.002) and inhibited recovery from potentially lethal gamma-radiation damage in LoVo cells by 73% (95% CI = 48% to 98%). In vivo, nontoxic doses of AG14361 increased the delay of LoVo xenograft growth induced by irinotecan, x-irradiation, or temozolomide by two- to threefold. The combination of AG14361 and temozolomide caused complete regression of SW620 xenograft tumors. AG14361 was retained in xenografts in which PARP-1 activity was inhibited by more than 75% for at least 4 hours.

CONCLUSION

AG14361 is, to our knowledge, the first high-potency PARP-1 inhibitor with the specificity and in vivo activity to enhance chemotherapy and radiation therapy of human cancer.

The management of recurrent and drug-resistant gestational trophoblastic neoplasia (GTN)

Gestational trophoblastic neoplasia (GTN) comprises a spectrum of disease from low-risk disease which can be cured with simple relatively non-toxic treatment, to extremely aggressive tumours which require specialized management. The prognostic variables in patients with GTN are different from those in other gynaecological malignancies, and the major adverse prognostic variables include long interval from antecedent pregnancy, high concentrations of the pregnancy hormone, human chorionic gonadotrophin, metastases in brain and liver and failure of prior treatment. Patients who relapse after their prior treatment can also be categorized into different risk groups. Salvage treatment can vary from single agent actinomycin D to combination chemotherapy and, in selected cases, surgery. With appropriate management, the majority of patients can achieve long-term remission and, in most cases, preserve fertility. The late side-effects of more intensive treatment are a small risk of inducing second tumours and also of bringing forward the age of menopause.

A mechanistic mathematical model of temozolomide myelosuppression in children with high-grade gliomas

Temozolomide (TMZ) is currently being evaluated for the treatment of high-grade gliomas in children. Myelosuppression (the suppression of bone marrow activity) is the dose-limiting toxicity for TMZ in adults and children. Empirical methods (i.e. relations between the percent change in absolute neutrophil count (ANC) and the area under the plasma concentration curve (AUC) of TMZ or its active metabolite MTIC) showed poor results when attempting to describe myelosuppression from serial data derived during TMZ therapy in a Phase II study of children with high-grade glioma. Therefore, to improve our understanding of the myelosuppressive effects of TMZ and MTIC in children we developed a mechanistic mathematical model. The model describes the progression of neutrophils from their production in the bone marrow to their release in the plasma. Included in the model are the feedback effects of granulocyte colony stimulating factor (G-CSF), which stimulates neutrophil production when there is a decrease in circulating neutrophils. The model is fit to serial ANC measurements obtained after TMZ dosing and it is able to explain, among other things, the lag in ANC reduction following a dose of TMZ, the ANC nadir, and the 'rebound effect' observed where the ANC recovers to levels greater than that observed pre-TMZ dose. This model will be useful for the prospective design of clinical trials of TMZ in children with cancer.

Synthesis of pyrimidinopyridine-triazene conjugates targeted to abl tyrosine kinase

The synthesis and abl tyrosine kinase inhibitory activities of alkyltriazenes conjugated to phenylaminopyrimidines are described. Significant abl inhibitory activities were observed only when a benzamido spacer was inserted between the 1,2,3-triazene chain and the 2-phenyaminopyridopyrimidine moiety.

Inhibition of angiogenesis by non-toxic doses of temozolomide

It is well established that certain chemotherapeutic agents have potent antiangiogenic properties which may be part of their antitumor activity. Temozolomide (TMZ) is a lipophilic methylating agent used in the therapy of malignant melanoma and other tumors. We sought to determine whether TMZ is capable of inhibiting angiogenesis or influencing endothelial function. We used the in vivo chorioallantoic membrane (CAM) assay, and HUVEC-based in vitro Matrigel, adhesion and proliferation assays to determine the antiangiogenic effects of different doses of TMZ. In the CAM assay, angiogenesis was significantly inhibited by 5 microM TMZ, a concentration also found to be effective in interfering with in vitro angiogenesis as measured by the Matrigel assay. For the inhibition of basic fibroblast growth factor (bFGF)-, vascular endothelial growth factor (VEGF)- or beta-phorbol 12-myristate-13-acetate (PMA)-induced endothelial cell proliferation or endothelial cell adhesion to fibronectin, TMZ concentrations of at least 25 microM were necessary, indicating that bFGF-, VEGF- or protein kinase C-mediated pathways may not primarily be involved in the observed antiangiogenic effect. Thus, we could demonstrate that TMZ inhibits angiogenesis at low, non-toxic doses that correspond to the plasma concentrations achieved by an oral application of 20 mg/m2 every 8 h. This 'metronomic' scheduling has already been used in phase I studies and has produced antitumor effects. Therefore, the antitumor activity of TMZ may, at least in part, be due to its antiangiogenic properties. The precise mechanism of its antiangiogenic action remains to be elucidated.

Temozolomide in combination with interferon alpha-2b in patients with metastatic melanoma: a phase I dose-escalation study

BACKGROUND

Metastatic melanoma (MM) is associated with a high risk of central nervous system (CNS) metastases, and current chemotherapy does not adequately treat or protect patients with MM against CNS metastases. Therefore, the authors initiated a Phase I study to determine the pharmacokinetics and safety profile of temozolomide (TMZ), a novel oral alkylating agent known to cross the blood-brain barrier, in combination with interferon alpha-2b (IFN-alpha2b).

METHODS

Twenty-three patients with MM were enrolled in this single-center, open-label study. Patients with CNS metastasis were excluded. One cohort (n = 6 patients) received oral TMZ (200 mg/m(2) per day) for 5 days every 28-day cycle plus subcutaneous IFN-alpha2b (5 million International Units [MIU]/m(2) per day, 3 times per week). A second cohort (n = 17 patients) received TMZ 150 mg/m(2) per day on the same schedule plus escalating doses of IFN-alpha2b (5.0 MIU/m(2) per day, 7.5 MIU/m(2) per day, and 10 MIU/m(2) per day 3 times per week).

RESULTS

The most common adverse events were fatigue, fever, nausea/emesis, anxiety, and diarrhea. Most toxicity was mild to moderate in severity. The primary dose-limiting toxicity was thrombocytopenia. The maximum tolerated dose was either TMZ 150 mg/m(2) plus IFN-alpha2b 7.5 MIU/m(2) or TMZ 200 mg/m(2) plus IFN-alpha2b 5.0 MIU/m(2). Four patients (17%) had objective responses (one complete response and three partial responses), and four patients had stable disease. The median survival was 9 months. The pharmacokinetics of TMZ were not affected by coadministration of IFN-alpha2b.

CONCLUSIONS

TMZ can be combined safely with IFN-alpha2b. This regimen demonstrated clinical activity in patients with MM and merits further investigation to define its effect on the incidence of brain metastases.

Inhibition of telomerase increases resistance of melanoma cells to temozolomide, but not to temozolomide combined with poly (adp-ribose) polymerase inhibitor

In the present study, we have investigated the influence of telomerase inhibition in chemosensitivity of melanoma cells to temozolomide (TMZ), a methylating agent with promising antitumor activity against metastatic melanoma. In fact, telomerase, a ribonucleoprotein enzyme expressed in the majority of tumors, is presently considered an attractive target for anticancer therapy, with the double aim of reducing tumor growth and increasing chemosensitivity of cancer cells. Susceptibility to TMZ and to other antitumor agents used for treatment of metastatic melanoma was initially assessed in melanoma lines with different basal levels of telomerase activity. Thereafter, chemosensitivity was investigated after inhibition of telomerase by means of stable transfection of a catalytically inactive, dominant-negative mutant of hTERT (DN-hTERT). This study shows for the first time that: a) susceptibility to TMZ of melanoma lines derived from the same patient did not depend on basal telomerase activity; b) inhibition of telomerase by DN-hTERT resulted in reduced growth rate and increased resistance to TMZ and to the chloroethylating agent carmustine, increased sensitivity to cisplatin, and no change in response to tamoxifen or to a selective N3-adenine methylating agent; c) inhibition of poly(ADP-ribose) polymerase (PARP), an enzyme involved in the repair of N-methylpurines, restored sensitivity of DN-hTERT clones to TMZ. These results indicate that a careful selection of the antitumor agent has to be made when antitelomerase therapy is combined with chemotherapy. Moreover, the data presented here suggest that TMZ + PARP inhibitor combination is active against telomerase-suppressed and slowly growing tumors.

Temozolomide in malignant gliomas of childhood: a United Kingdom Children's Cancer Study Group and French Society for Pediatric Oncology Intergroup Study

PURPOSE

To determine the response rate of the malignant gliomas of childhood to an oral, daily schedule of temozolomide.

PATIENTS AND METHODS

A multicenter, phase II evaluation of an oral, daily schedule of temozolomide (200 mg/m(2) on 5 consecutive days) was undertaken in children with relapsed or progressive, biopsy-proven, high-grade glioma (arm A) and progressive, diffuse, intrinsic brainstem glioma (arm B). Evidence of activity was defined by radiologic evidence of a sustained reduction in tumor size on serial magnetic resonance imaging scans.

RESULTS

Fifty-five patients were recruited (34 to arm A and 21 to arm B) and received 215 cycles of chemotherapy. Grade 3/4 thrombocytopenia was the most frequent toxic event (7% of cycles). Prolonged myelosuppression resulted in significant treatment delays and dose reductions (17% and 22% of cycles, respectively). Two toxic deaths were documented and were related to myelosuppression and sepsis in one patient and pneumonia in a second. The overall (best) response rate was 12% for arm A (95% confidence interval [CI], 3 to 28 in the study cohort, and 2 to 31 for eligible patients) and 5% and 6%, respectively, for arm B (95% CI, 0 to 26 in the study cohort, and 0 to 27 for eligible patients). Stabilization of disease was also documented and was most noteworthy for brainstem gliomas, where two patients achieved both radiologic static disease and discontinued steroid medication.

CONCLUSION

Despite moderate toxicity, objective response rates to temozolomide have been low, indicating that temozolomide has minimal activity in the high-grade gliomas of childhood.

Chemosensitivity of glioblastoma cells during treatment with the organo-tin compound triethyltin(IV)lupinylsulfide hydrochloride

Malignant gliomas are the most common primary brain tumors in humans. However, poor response to conventional therapeutic approaches, including chemotherapy, leads invariably to disease recurrence and progression. The organo-tin derivative triethyltin(IV)lupinylsulfide hydrochloride (IST-FS 29) was identified and developed as potential antiproliferative agent in human cancer cell lines. However, for its peculiar chemical structure and good lipophilicity, this compound also appeared an eligible candidate for the treatment of gliobastoma cells. The present experiments were designed to explore the in vitro effects of IST-FS 29 on four human glioblastoma cell lines: A-172, DBTRG.05MG, U-87MG and CAS-1. The average IC50 values were obtained by MTT assay and ranged between 3 and 10 microM. Time-course assays with cell recovery after drug withdrawal, demonstrated marked cytotoxicity following exposure to IST-FS 29 for 8, 24 and 72 h. Cultures treated for 8 h were able to partially re-grow by 144 h; on the contrary, longer times of exposure did not allow surviving cells to recover from the damage and actively proliferate. Cell morphology of cultures exposed to IST-FS 29 was assessed by inverted light microscopy after 24 and 72 h and was more consistent with cell death by necrosis which included cell size reduction, vacuolation of cytoplasm, round dying cells. The present results and our previous data, in vitro and in vivo, indicate the relevant cytotoxic activity of this organo-tin compound and suggest that IST-FS 29 might be a promising novel agent to be developed for the treatment of malignant brain neoplasms.

Chemotherapy for the treatment of metastatic brain tumors

Metastatic brain tumors are the most common complication of systemic cancer and affect 20-40% of all adult cancer patients. Whole-brain radiotherapy and surgical resection of accessible, solitary lesions have been the mainstay of treatment. Recently, chemotherapy has become a more viable treatment option for metastatic brain tumors. Many different drugs and administrative approaches have been shown to be clinically active. Traditional chemotherapy given before or during irradiation can be effective with agents such as cyclophosphamide, cisplatin and etoposide. Nontraditional approaches, such as tempozolomide and intra-arterial administration of carboplatin, have demonstrated activity against recurrent metastatic disease. In early clinical trials of interstitial chemotherapy, biodegradable polymers have shown some clinical efficacy and have been well-tolerated. Molecular approaches are also under investigation in response to new information regarding the metastatic phenotype. Potential targets include growth factor receptors and other protein tyrosine kinases, internal signal transduction pathways, ras activation and matrix metalloprotease activity. New clinical trials will be needed to investigate these new molecular-based therapeutics, alone and in combination with currently available treatment options, to determine the optimal application of chemotherapy to metastatic brain tumors.

Poly(ADP-ribose) polymerase inhibitor increases growth inhibition and reduces G(2)/M cell accumulation induced by temozolomide in malignant glioma cells

Temozolomide (TZM) is a novel methylating agent currently under investigation for treatment of recurrent high-grade gliomas. Although TZM generates a wide spectrum of methyl adducts, its cytotoxicity has been attributed to mismatch repair (MR)-mediated processing of O(6)-methylguanine:T mispairs. N3-methyladenine and N7-methylguanine adducts are promptly repaired by the base excision repair system, unless a poly(ADP-ribose) polymerase (PARP) inhibitor is combined to TZM. In this case, the repair process of N-methylpurines cannot be completed and the deriving DNA strand breaks contribute to cytotoxicity. In this study, we investigated the influence on cell growth and cell cycle of treatment with TZM + PARP inhibitor in glioma cells characterized by different susceptibility to TZM. The results indicated that PARP inhibitor increases growth inhibition induced by TZM in either p53-wild-type or p53-mutant glioblastoma cells, as early as 24 h after drug exposure. The enhancing effect exerted by PARP inhibitor was particularly evident in glioma cells characterized by a defective expression of MR, since these cells are tolerant to O(6)-methylguanine damage and show low sensitivity to TZM. In O(6)-alkylguanine-DNA alkyltransferase (OGAT)-deficient and MR-proficient tumor cells bearing wild-type p53, the drug combination markedly reduced cell accumulation in the G(2)/M phase of cell cycle and induction of the G(2) checkpoint regulator Chk1 kinase. In short-term cultures of glioma cells derived from surgical specimens, PARP inhibitor enhanced chemosensitivity to TZM and this effect was especially evident in OGAT-proficient tumors. Thus, a pharmacological strategy based on the interruption of N-methylpurine repair might represent a novel strategy to restore or increase glioma sensitivity to TZM.

A phase II EORTC study of temozolomide in patients with malignant pleural mesothelioma

The aim of this study was to investigate the anti-tumour activity of temozolomide in patients with malignant pleural mesothelioma. 27 chemotherapy-naïve patients with histologically-proven malignant mesothelioma were treated with temozolomide 200 mg/m2/day, given orally on days 1-5 of each 28-day cycle. Therapy continued up to 10 cycles unless disease progression or excessive toxicity mandated discontinuation. Toxicity, symptom improvement and pain intensity were regularly assessed. With a median relative dose intensity of 97%, toxicity was moderate with grade 3 or more nausea, vomiting, thrombocytopenia, leucocytopenia, neutropenia, febrile leucocytopenia, arthralgia, infection and fever with infection occurring in 13, 13, 10, 3, 7 and 3% of patients for the remaining events, respectively. Overall, 1 objective response was observed (response rate 4%, 95% Confidence Interval (CI): 0.1-19). Median survival was 8.2 months. Symptom assessment showed no improvement and an increase of pain was observed during the study. Thus, oral temozolomide is an inactive agent in malignant mesothelioma.