Activity of 9-dimethylaminomethyl-10-hydroxycamptothecin against pediatric and adult central nervous system tumor xenografts

Leptomeningeal Dissemination of Low-Grade Neuroepithelial Tumor with FGFR1_TACC1 Fusion with Clinical and Radiographic Response to Pazopanib and Topotecan

INTRODUCTION

Low-grade neuroepithelial tumors are a heterogeneous group of central nervous system tumors that are generally indolent in nature but in rare instances can progress to include leptomeningeal dissemination.

CASE PRESENTATION

We present a case of a patient with a low-grade neuroepithelial tumor of indeterminate type with symptomatic leptomeningeal dissemination despite 3 chemotherapy regimens and radiotherapy. Somatic targetable mutation testing showed an FGFR1_TACC1 fusion. Therapy with pazopanib/topotecan was initiated, and disease stabilization was achieved. He received pazopanib/topotecan for a total of 2 years and is now >2 years from completion of treatment and continues to do well with no evidence of disease.

DISCUSSION

This case highlights the utility of targetable mutation testing in therapeutic decision-making and the novel use of systemic pazopanib/topotecan therapy for refractory low-grade neuroepithelial tumor within the context of this clinical situation and specific mutation profile.

A Modified Nucleoside 6-Thio-2'-Deoxyguanosine Exhibits Antitumor Activity in Gliomas

PURPOSE

To investigate the therapeutic role of a novel telomere-directed inhibitor, 6-thio-2'-deoxyguanosine (THIO) in gliomas both in vitro and in vivo.

EXPERIMENTAL DESIGN

A panel of human and mouse glioma cell lines was used to test therapeutic efficacy of THIO using cell viability assays, flow cytometric analyses, and immunofluorescence. Integrated analyses of RNA sequencing and reverse-phase protein array data revealed the potential antitumor mechanisms of THIO. Four patient-derived xenografts (PDX), two patient-derived organoids (PDO), and two xenografts of human glioma cell lines were used to further investigate the therapeutic efficacy of THIO.

RESULTS

THIO was effective in the majority of human and mouse glioma cell lines with no obvious toxicity against normal astrocytes. THIO as a monotherapy demonstrated efficacy in three glioma cell lines that had acquired resistance to temozolomide. In addition, THIO showed efficacy in four human glioma cell lines grown as neurospheres by inducing apoptotic cell death. Mechanistically, THIO induced telomeric DNA damage not only in glioma cell lines but also in PDX tumor specimens. Integrated computational analyses of transcriptomic and proteomic data indicated that THIO significantly inhibited cell invasion, stem cell, and proliferation pathways while triggering DNA damage and apoptosis. Importantly, THIO significantly decreased tumor proliferation in two PDO models and reduced the tumor size of a glioblastoma xenograft and a PDX model.

CONCLUSIONS

The current study established the therapeutic role of THIO in primary and recurrent gliomas and revealed the acute induction of telomeric DNA damage as a primary antitumor mechanism of THIO in gliomas.

Continuous and bolus intraventricular topotecan prolong survival in a mouse model of leptomeningeal medulloblastoma

Leptomeningeal metastasis remains a difficult clinical challenge. Some success has been achieved by direct administration of therapeutics into the cerebrospinal fluid (CSF) circumventing limitations imposed by the blood brain barrier. Here we investigated continuous infusion versus bolus injection of therapy into the CSF in a preclinical model of human Group 3 medulloblastoma, the molecular subgroup with the highest incidence of leptomeningeal disease. Initial tests of selected Group 3 human medulloblastoma cell lines in culture showed that D283 Med and D425 Med were resistant to cytosine arabinoside and methotrexate. D283 Med cells were also resistant to topotecan, whereas 1 μM topotecan killed over 99% of D425 Med cells. We therefore introduced D425 Med cells, modified to express firefly luciferase, into the CSF of immunodeficient mice. Mice were then treated with topotecan or saline in five groups: continuous intraventricular (IVT) topotecan via osmotic pump (5.28 μg/day), daily bolus IVT topotecan injections with a similar daily dose (6 μg/day), systemic intraperitoneal injections of a higher daily dose of topotecan (15 μg/day), daily IVT pumped saline and daily intraperitoneal injections of saline. Bioluminescence analyses revealed that both IVT topotecan treatments effectively slowed leptomeningeal tumor growth in the brains. Histological analysis showed that they were associated with localized brain necrosis, possibly due to backtracking of topotecan around the catheter. In the spines, bolus IVT topotecan showed a trend towards slower tumor growth compared to continuous (pump) IVT topotecan, as measured by bioluminescence. Both continuous and bolus topotecan IVT showed longer survival compared to other groups. Thus, both direct IVT topotecan CSF delivery methods produced better anti-medulloblastoma effect compared to systemic therapy at the dosages used here.

Sym004-induced EGFR elimination is associated with profound anti-tumor activity in EGFRvIII patient-derived glioblastoma models

BACKGROUND

Sym004 is a mixture of two monoclonal antibodies (mAbs), futuximab and modotuximab, targeting non-overlapping epitopes on the epidermal growth factor receptor (EGFR). Previous studies have shown that Sym004 is more efficient at inducing internalization and degradation of EGFR than individual components, which translates into superior cancer cell inhibition. We investigated whether Sym004 induces removal of EGFRvIII and if this removal translates into tumor growth inhibition in hard-to-treat glioblastomas (GBMs) harboring the mutated, constitutively active EGFR variant III (EGFRvIII).

METHODS

To address this question, we tested the effect of Sym004 versus cetuximab in eight patient-derived GBM xenograft models expressing either wild-type EGFR (EGFRwt) and/or mutant EGFRvIII. All models were tested as both subcutaneous and orthotopic intracranial xenograft models.

RESULTS

In vitro studies demonstrated that Sym004 internalized and removed EGFRvIII more efficiently than mAbs, futuximab, modotuximab, and cetuximab. Removal of EGFRvIII by Sym004 translated into significant in vivo anti-tumor activity in all six EGFRvIII xenograft models. Furthermore, the anti-tumor activity of Sym004 in vivo was superior to that of its individual components, futuximab and modotuximab, suggesting a clear synergistic effect of the mAbs in the mixture.

CONCLUSION

These results demonstrate the broad activity of Sym004 in patient-derived EGFRvIII-expressing GBM xenograft models and provide a clear rationale for clinical evaluation of Sym004 in EGFRvIII-positive adult GBM patients.

Major Contributions towards Finding a Cure for Cancer through Chemotherapy: A Historical Review

The history of cancer chemotherapy is as old as cancer itself. With the increase in the complexities of cancer and the development of resistance towards existing anticancer agents, increased attention is now being paid to the advancement of chemotherapy. Some chemotherapeutic agents were discovered by accident or trial-and-error methods while others were found to be useful for neoplasia when they were being evaluated for some other purpose. Broadly, these agents have been classified as alkylating agents, antimetabolites, platinum compounds, antitumor antibiotics and natural products. Hormones and compounds interfering with hormone metabolism are widely used in cancer treatment, besides monoclonal antibodies and small molecules targeting angiogenesis. In this review an attempt is made to discuss the major breakthroughs that have shaped the course of cancer chemotherapy, helping to decrease the mortality as well as lessen the suffering of patients.

Topoisomerase I inhibitors, shikonin and topotecan, inhibit growth and induce apoptosis of glioma cells and glioma stem cells

Gliomas, the most malignant form of brain tumors, contain a small subpopulation of glioma stem cells (GSCs) that are implicated in therapeutic resistance and tumor recurrence. Topoisomerase I inhibitors, shikonin and topotecan, play a crucial role in anti-cancer therapies. After isolated and identified the GSCs from glioma cells successfully, U251, U87, GSCs-U251 and GSCs-U87 cells were administrated with various concentrations of shikonin or topotecan at different time points to seek for the optimal administration concentration and time point. The cell viability, cell cycle and apoptosis were detected using cell counting kit-8 and flow cytometer to observe the inhibitory effects on glioma cells and GSCs. We demonstrated that shikonin and topotecan obviously inhibited proliferation of not only human glioma cells but also GSCs in a dose- and time-dependent manner. According to the IC50 values at 24 h, 2 μmol/L of shikonin and 3 μmol/L of topotecan were selected as the optimal administration concentration. In addition, shikonin and topotecan induced cell cycle arrest in G0/G1 and S phases and promoted apoptosis. The down-regulation of Bcl-2 expression with the activation of caspase 9/3-dependent pathway was involved in the apoptosis process. Therefore, the above results showed that topoisomerase I inhibitors, shikonin and topotecan, inhibited growth and induced apoptosis of GSCs as well as glioma cells, which suggested that they might be the potential anticancer agents targeting gliomas to provide a novel therapeutic strategy.

Proteasome inhibition with bortezomib induces cell death in GBM stem-like cells and temozolomide-resistant glioma cell lines, but stimulates GBM stem-like cells' VEGF production and angiogenesis

OBJECT

Recurrent malignant gliomas have inherent resistance to traditional chemotherapy. Novel therapies target specific molecular mechanisms involved in abnormal signaling and resistance to apoptosis. The proteasome is a key regulator of multiple cellular functions, and its inhibition in malignant astrocytic lines causes cell growth arrest and apoptotic cell death. The proteasome inhibitor bortezomib was reported to have very good in vitro activity against malignant glioma cell lines, with modest activity in animal models as well as in clinical trials as a single agent. In this paper, the authors describe the multiple effects of bortezomib in both in vitro and in vivo glioma models and offer a novel explanation for its seeming lack of activity.

METHODS

Glioma stem-like cells (GSCs) were obtained from resected glioblastomas (GBMs) at surgery and expanded in culture. Stable glioma cell lines (U21 and D54) as well as temozolomide (TMZ)-resistant glioma cells derived from U251 and D54-MG were also cultured. GSCs from 2 different tumors, as well as D54 and U251 cells, were treated with bortezomib, and the effect of the drug was measured using an XTT cell viability assay. The activity of bortezomib was then determined in D54-MG and/or U251 cells using apoptosis analysis as well as caspase-3 activity and proteasome activity measurements. Human glioma xenograft models were created in nude mice by subcutaneous injection. Bevacizumab was administered via intraperitoneal injection at a dose of 5 mg/kg daily. Bortezomib was administered by intraperitoneal injection 1 hour after bevacizumab administration in doses of at a dose of 0.35 mg/kg on days 1, 4, 8, and 11 every 21 days. Tumors were measured twice weekly.

RESULTS

Bortezomib induced caspase-3 activation and apoptotic cell death in stable glioma cell lines and in glioma stem-like cells (GSCs) derived from malignant tumor specimens Furthermore, TMZ-resistant glioma cell lines retained susceptibility to the proteasome inhibition. The bortezomib activity was directly proportional with the cells' baseline proteasome activity. The proteasome inhibition stimulated both hypoxia-inducible factor (HIF)-1α and vascular endothelial growth factor (VEGF) production in malignant GSCs. As such, the VEGF produced by GSCs stimulated endothelial cell growth, an effect that could be prevented by the addition of bevacizumab (VEGF antibody) to the media. Similarly, administration of bortezomib and bevacizumab to athymic mice carrying subcutaneous malignant glioma xenografts resulted in greater tumor inhibition and greater improvement in survival than administration of either drug alone. These data indicate that simultaneous proteasome inhibition and VEGF blockade offer increased benefit as a strategy for malignant glioma therapy.

CONCLUSIONS

The results of this study indicate that combination therapies based on bortezomib and bevacizumab might offer an increased benefit when the two agents are used in combination. These drugs have a complementary mechanism of action and therefore can be used together to treat TMZ-resistant malignant gliomas.

Induction of the unfolded protein response drives enhanced metabolism and chemoresistance in glioma cells

The unfolded protein response (UPR) is an endoplasmic reticulum (ER)-based cytoprotective mechanism acting to prevent pathologies accompanying protein aggregation. It is frequently active in tumors, but relatively unstudied in gliomas. We hypothesized that UPR stress effects on glioma cells might protect tumors from additional exogenous stress (ie, chemotherapeutics), postulating that protection was concurrent with altered tumor cell metabolism. Using human brain tumor cell lines, xenograft tumors, human samples and gene expression databases, we determined molecular features of glioma cell UPR induction/activation, and here report a detailed analysis of UPR transcriptional/translational/metabolic responses. Immunohistochemistry, Western and Northern blots identified elevated levels of UPR transcription factors and downstream ER chaperone targets in gliomas. Microarray profiling revealed distinct regulation of stress responses between xenograft tumors and parent cell lines, with gene ontology and network analyses linking gene expression to cell survival and metabolic processes. Human glioma samples were examined for levels of the ER chaperone GRP94 by immunohistochemistry and for other UPR components by Western blotting. Gene and protein expression data from patient gliomas correlated poor patient prognoses with increased expression of ER chaperones, UPR target genes, and metabolic enzymes (glycolysis and lipogenesis). NMR-based metabolomic studies revealed increased metabolic outputs in glucose uptake with elevated glycolytic activity as well as increased phospholipid turnover. Elevated levels of amino acids, antioxidants, and cholesterol were also evident upon UPR stress; in particular, recurrent tumors had overall higher lipid outputs and elevated specific UPR arms. Clonogenicity studies following temozolomide treatment of stressed or unstressed cells demonstrated UPR-induced chemoresistance. Our data characterize the UPR in glioma cells and human tumors, and link the UPR to chemoresistance possibly via enhanced metabolism. Given the role of the UPR in the balance between cell survival and apoptosis, targeting the UPR and/or controlling metabolic activity may prove beneficial for malignant glioma therapeutics.

Pilot study assessing a seven-day continuous intrathecal topotecan infusion for recurrent or progressive leptomeningeal metastatic cancer

Objective

To determine the feasibility and toxicity profile of topotecan administered as a seven-day continuous intrathecal infusion for patients with leptomeningeal metastasis secondary to recurrent or progressive central nervous system cancer.

Study design

Two patients with central nervous system leptomeningeal metastasis were treated with a seven-day continuous infusion of topotecan (0.2 mg/day) administered via continuous intrathecal/intraventricular infusion at a rate of 0.6 mL/h, totaling 1.4 mg/course. CSF and plasma concentrations of topotecan closed lactone (the active metabolite) were quantified at various points during topotecan infusion. Patients were monitored for neurologic and systemic toxicities according to NCI common toxicity criteria.

Results

Both patients tolerated the seven-day continuous topotecan without any significant adverse events. One patient received a second course 21 days after treatment initiation. CSF concentration of topotecan closed lactone ranged from 3.73 to 312 ng/mL (median = 131 ng/mL) and plasma topotecan closed lactone ranged from 0.44 to 1.78 ng/mL (median = 0.92 ng/mL). The median CSF topotecan concentration was greater than the median serum topotecan concentration by a 44-fold magnitude when samples were obtained at the same time point. None of the patients experienced any grade 3 or higher hematological toxicities or signs of arachnoiditis.

Conclusion

A seven-day continuous intrathecal infusion of topotecan is well tolerated and has the potential of maximizing central nervous system drug exposure.

Recombinant anti-podoplanin (NZ-1) immunotoxin for the treatment of malignant brain tumors

Our study demonstrates the glioma tumor antigen podoplanin to be present at very high levels (>90%) in both glioblastoma (D2159MG, D08-0308MG and D08-0493MG) and medulloblastoma (D283MED, D425MED and DAOY) xenografts and cell line. We constructed a novel recombinant single-chain antibody variable region fragment (scFv), NZ-1, specific for podoplanin from the NZ-1 hybridoma. NZ-1-scFv was then fused to Pseudomonas exotoxin A, carrying a C-terminal KDEL peptide (NZ-1-PE38KDEL). The immunotoxin (IT) was further stabilized by a disulfide (ds) bond between the heavy-chain and light-chain variable regions as the construct NZ-1-(scdsFv)-PE38KDEL. NZ-1-(scdsFv)-PE38KDEL exhibited significant reactivity to glioblastoma and medulloblastoma cells. The affinity of NZ-1-(scdsFv), NZ-1-(scdsFv)-PE38KDEL and NZ-1 antibody for podoplanin peptide was 2.1 × 10(-8) M, 8.0 × 10(-8) M and 3.9 × 10(-10) M, respectively. In a protein stability assay, NZ-1-(scdsFv)-PE38KDEL retained 33-98% of its activity, whereas that of NZ-1-PE38KDEL declined to 13% of its initial levels after incubation at 37°C for 3 days. In vitro cytotoxicity of the NZ-1-(scdsFv)-PE38KDEL was measured in cells isolated from glioblastoma xenografts, D2159MG, D08-0308MG and D08-0493MG, and in the medulloblastoma D283MED, D425MED and DOAY xenografts and cell line. The NZ-1-(scdsFv)-PE38KDEL IT was highly cytotoxic, with an 50% inhibitory concentration in the range of 1.6-29 ng/ml. Significantly, NZ-1-(scdsFv)-PE38KDEL demonstrated tumor growth delay, averaging 24 days (p < 0.001) and 21 days (p < 0.001) in D2159MG and D283MED in vivo tumor models, respectively. Crucially, in the D425MED intracranial tumor model, NZ-1-(scdsFv)-PE38KDEL caused a 41% increase in survival (p ≤ 0.001). In preclinical studies, NZ-1-(scdsFv)-PE38KDEL exhibited significant potential as a targeting agent for malignant brain tumors.

Affinity-matured anti-glycoprotein NMB recombinant immunotoxins targeting malignant gliomas and melanomas

Glycoprotein NMB (GPNMB), a transmembrane glycoprotein highly expressed in high-grade gliomas (HGGs), is an attractive target in cancer immunotherapy. We isolated a GPNMB-specific scFv clone, G49, from a human synthetic phage-display library. To obtain mutant single-chain variable-fragment antibodies (scFvs) with improved affinity and immunotoxins with increased activity, we subjected G49 to in vitro affinity maturation by a complementarity-determining-region (CDR) random-mutagenesis technique. Using light-chain CDR3 mutagenesis, cell-based panning by phage display, subsequent heavy-chain CDR1 mutagenesis, and flow-cytometric selection by yeast-surface display, we generated the mutant scFv clone 902V, with an overall 11-fold increase in affinity for GPNMB. Clone 902V was further randomized throughout the whole scFv by error-prone PCR, and one mutant, F6V, was selected by yeast-surface display. F6V scFv, differing from 902V by one amino-acid change in the light-chain CDR2, exhibited an affinity for GPNMB of 0.30 nM. The F6V mutant scFv clone was fused with a truncated form of Pseudomonas exotoxin A to form the immunotoxin F6V-PE38. F6V-PE38 demonstrated significant protein-synthesis-inhibition activity on GPNMB-expressing glioma and malignant melanoma cells (IC(50) = 0.5 ng/ml [8 pM]), a 60-fold improvement over G49 activity, but no cytotoxicity on GPNMB-negative cells. Furthermore, F6V-PE38 exhibited significant antitumor activity against subcutaneous malignant glioma xenografts in two nude-mouse models and a melanoma neoplastic meningitis model in athymic rats. These GPNMB-specific scFv antibodies and immunotoxins hold promise as reagents in targeted therapy for HGGs and other GPNMB-expressing malignancies.

Cancer therapies utilizing the camptothecins: a review of the in vivo literature

This review summarizes the in vivo assessment-preliminary, preclinical, and clinical-of chemotherapeutics derived from camptothecin or a derivative. Camptothecin is a naturally occurring, pentacyclic quinoline alkaloid that possesses high cytotoxic activity in a variety of cell lines. Major limitations of the drug, including poor solubility and hydrolysis under physiological conditions, prevent full clinical utilization. Camptothecin remains at equilibrium in an active lactone form and inactive hydrolyzed carboxylate form. The active lactone binds to DNA topoisomerase I cleavage complex, believed to be the single site of activity. Binding inhibits DNA religation, resulting in apoptosis. A series of small molecule camptothecin derivatives have been developed that increase solubility, lactone stability and bioavailability to varying levels of success. A number of macromolecular agents have also been described wherein camptothecin(s) are covalently appended or noncovalently associated with the goal of improving solubility and lactone stability, while taking advantage of the tumor physiology to deliver larger doses of drug to the tumor with lower systemic toxicity. With the increasing interest in drug delivery and polymer therapeutics, additional constructs are anticipated. The goal of this review is to summarize the relevant literature for others interested in the field of camptothecin-based therapeutics, specifically in the context of biodistribution, dosing regimens, and pharmacokinetics with the desire of providing a useful source of comparative data. To this end, only constructs where in vivo data is available are reported. The review includes published reports in English through mid-2009.

Tyrosine kinase inhibitor gefitinib enhances topotecan penetration of gliomas

Gefitinib, an epidermal growth factor receptor tyrosine kinase inhibitor, increases brain parenchymal extracellular fluid (ECF) accumulation of topotecan, a substrate of the ATP-binding cassette (ABC) transporters P-glycoprotein (Pgp/MDR-1) and breast cancer resistance protein (BCRP/ABCG2). The effect of modulating these transporters on topotecan penetration in gliomas has not been thoroughly studied. Thus, we performed intracerebral microdialysis on mice bearing orthotopic human gliomas (U87 and MT330) and assessed topotecan tumor ECF (tECF) penetration and the effect of gefitinib on topotecan tECF penetration and intratumor topotecan distribution. We found that topotecan penetration (P(tumor)) of U87 was 0.96 +/- 0.25 (n = 7) compared with that of contralateral brain (P(contralateral), 0.42 +/- 0.11, n = 5; P = 0.001). In MT330 tumors, P(tumor) (0.78 +/- 0.26, n = 6) and P(contralateral) (0.42 +/- 0.11, n = 5) also differed significantly (P = 0.013). Because both tumor models had disrupted blood-brain barriers and similar P(tumor) values, we used U87 and a steady-state drug administration approach to characterize the effect of gefitinib on topotecan P(tumor). At equivalent plasma topotecan exposures, we found that P(tumor) after gefitinib administration was lower. In a separate cohort of animals, we determined the volume of distribution of unbound topotecan in tumor (V(u,tumor)) and found that it was significantly higher in groups receiving gefitinib, implying that gefitinib administration leads to a greater proportion of intracellular topotecan. Our results provide crucial insights into the role that transporters play in central nervous system drug penetration and provide a better understanding of the effect of coadministration of transporter modulators on anticancer drug distribution within a tumor.

Topotecan in combination with radiotherapy in unresectable glioblastoma: a phase 2 study

Improving glioblastoma multiforme (GBM) treatment with radio-chemotherapy remains a challenge. Topotecan is an attractive option as it exhibits growth inhibition of human glioma as well as brain penetration. The present study assessed the combination of radiotherapy (60 Gy/30 fractions/40 days) and topotecan (0.9 mg/m(2)/day on days 1-5 on weeks 1, 3 and 5) in 50 adults with histologically proven and untreated GBM. The incidence of non-hematological toxicities was low and grade 3-4 hematological toxicities were reported in 20 patients (mainly lymphopenia and neutropenia). Partial response and stabilization rates were 2% and 32%, respectively, with an overall time to progression of 12 weeks. One-year overall survival (OS) rate was 42%, with a median OS of 40 weeks. Topotecan in combination with radiotherapy was well tolerated. However, while response and stabilization concerned one-third of the patients, the study did not show increased benefits in terms of survival in patients with unresectable GBM.

Molecular characterization of the pediatric preclinical testing panel

PURPOSE

Identifying novel therapeutic agents for the treatment of childhood cancers requires preclinical models that recapitulate the molecular characteristics of their respective clinical histotypes.

EXPERIMENTAL DESIGN AND RESULTS

Here, we have applied Affymetrix HG-U133Plus2 profiling to an expanded panel of models in the Pediatric Preclinical Testing Program. Profiling led to exclusion of two tumor lines that were of mouse origin and five osteosarcoma lines that did not cluster with human or xenograft osteosarcoma samples. We compared expression profiles of the remaining 87 models with profiles from 112 clinical samples representing the same histologies and show that model tumors cluster with the appropriate clinical histotype, once "immunosurveillance" genes (contributed by infiltrating immune cells in clinical samples) are eliminated from the analysis. Analysis of copy number alterations using the Affymetrix 100K single nucleotide polymorphism GeneChip showed that the models have similar copy number alterations to their clinical counterparts. Several consistent copy number changes not reported previously were found (e.g., gain at 22q11.21 that was observed in 5 of 7 glioblastoma samples, loss at 16q22.3 that was observed in 5 of 9 Ewing's sarcoma and 4 of 12 rhabdomyosarcoma models, and amplification of 21q22.3 that was observed in 5 of 7 osteosarcoma models). We then asked whether changes in copy number were reflected by coordinate changes in gene expression. We identified 493 copy number-altered genes that are nonrandom and appear to identify histotype-specific programs of genetic alterations.

CONCLUSIONS

These data indicate that the preclinical models accurately recapitulate expression profiles and genetic alterations common to childhood cancer, supporting their value in drug development.

Phase I/II study of IV topotecan in combination with whole brain radiation for the treatment of brain metastases

A phase I/II trial was conducted to determine the toxicities and efficacy (overall response, overall survival, and progression-free survival) of the combination of topotecan and whole brain radiation therapy (XRT) in patients with brain metastases. Patients received 30 Gy XRT given in 10 fractions to the whole brain. In phase I, patients were treated in groups of three at each topotecan dose level; dose escalation proceeded until the maximum tolerated dose (MTD) was identified. The dose-limiting toxicity proved to be grade IV neutropenia at 0.6 mg/m2/d, resulting in an MTD of 0.5 mg/m2/d. One of nine patients showed a response to treatment, and that was partial (OR 11%). Three had stable disease (33%), and four experienced progressive disease (44%). Median progression-free survival was 60 d; median overall survival was 102 d. Intravenous topotecan at 0.5 mg/m2/d concomitant to XRT with 30 Gy in 3-Gy fractions is tolerable in patients with brain metastases. This regimen has the additional advantage of providing systemic treatment to patients with metastases in other locations while whole brain radiation is in progress. Although response and survival outcomes in this small study do not appear higher than expected from historical controls, these were not primary end points, and larger studies on this topic would be useful to elucidate the efficacy of this combination treatment regimen.

Activity of VNP40101M (Cloretazine) in the treatment of CNS tumor xenografts in athymic mice

VNP40101M, or 1,2-bis(methylsulfonyl)-1-(2-choloroethyl)-2-(methylamino)carbonylhydrazine (Cloretazine), is a bifunctional prodrug that belongs to a class of DNA-modifying agents-the sulfonylhydrazines-that has been synthesized and been shown to have activity against a wide spectrum of xenografts. The current study was designed to assess the activity of VNP40101M administered at a dose of 18 mg/kg daily for five days against a panel of human adult and pediatric CNS tumors growing subcutaneously or intracranially in athymic nude mice. The results demonstrated statistically significant (p < 0.05) growth delays of 15.0, 8.3, 51.0, 60+, 60+, and 60+ days in subcutaneous xenografts derived from childhood glioblastoma multiforme (D-456 MG), childhood ependymoma (D-528 EP and D-612 EP), childhood medulloblastoma (D-425 MED), and adult malignant glioma (D-245 MG and D-54 MG), respectively, with corresponding tumor regressions in 10 of 10, 4 of 10, 8 of 10, 9 of 10, 9 of 10, and 10 of 10 treated mice, respectively. Delayed toxicity was seen more than 60 days after treatment, with 23 deaths in 100 treated animals, despite a median weight loss of only 0.06%. In mice bearing intracranial D-245 MG xenografts, treatment with VNP40101M at a dose of 18 mg/kg daily for five days produced a 50% increase in median survival compared with controls. Additional experiments conducted against subcutaneous D-245 MG xenografts by using reduced doses of 13.5 or 9.0 mg/kg daily for five days demonstrated tumor growth delays of 82.2 and 53.5 days, with corresponding tumor regressions in 8 of 9 and 9 of 10 treated mice, respectively (all values, p < 0.001), with one toxic death. These findings suggest that VNP40101M is active in the treatment of a wide range of human central nervous system tumors and warrants translation to the clinic.

Topotecan Central Nervous System Penetration Is Altered by a Tyrosine Kinase Inhibitor

A potential strategy to increase the efficacy of topotecan to treat central nervous system (CNS) malignancies is modulation of the activity of ATP-binding cassette (ABC) transporters at the blood-brain and blood-cerebrospinal fluid barriers to enhance topotecan CNS penetration. This study focused on topotecan penetration into the brain extracellular fluid (ECF) and ventricular cerebrospinal fluid (CSF) in a mouse model and the effect of modulation of ABC transporters at the blood-brain and blood-cerebrospinal fluid barriers by a tyrosine kinase inhibitor (gefitinib). After 4 and 8 mg/kg topotecan i.v., the brain ECF to plasma AUC ratio of unbound topotecan lactone was 0.21 +/- 0.04 and 0.61 +/- 0.16, respectively; the ventricular CSF to plasma AUC ratio was 1.18 +/- 0.10 and 1.30 +/- 0.13, respectively. To study the effect of gefitinib on topotecan CNS penetration, 200 mg/kg gefitinib was administered orally 1 hour before 4 mg/kg topotecan i.v. The brain ECF to plasma AUC ratio of unbound topotecan lactone increased by 1.6-fold to 0.35 +/- 0.04, which was significantly different from the ratio without gefitinib (P < 0.05). The ventricular CSF to plasma AUC ratio significantly decreased to 0.98 +/- 0.05 (P < 0.05). Breast cancer resistance protein 1 (Bcrp1), an efficient topotecan transporter, was detected at the apical aspect of the choroid plexus in FVB mice. In conclusion, topotecan brain ECF penetration was lower compared with ventricular CSF penetration. Gefitinib increased topotecan brain ECF penetration but decreased the ventricular CSF penetration. These results are consistent with the possibility that expression of Bcrp1 and P-glycoprotein at the apical side of the choroid plexus facilitates an influx transport mechanism across the blood-cerebrospinal fluid barrier, resulting in high topotecan CSF penetration.

Topotecan by 21-day continuous infusion in children with relapsed or refractory solid tumors: a Children's Oncology Group study

PURPOSE

The Children's Oncology Group conducted a phase II trial of 21-day continuous infusion topotecan to determine the response rate in pediatric patients with recurrent or refractory malignant solid tumors.

PROCEDURE

Patients with Ewing sarcoma family of tumors (ESFT), osteosarcoma (OS), soft tissue sarcomas (STS), medulloblastoma (MB)/primitive neuroectodermal tumor (PNET), astrocytoma, or neuroblastoma (NB) recurrent or refractory to conventional therapy, measurable disease, and adequate organ function were treated with topotecan 0.3 mg/m2/day by continuous intravenous infusion for 21 consecutive days, followed by 7 days without therapy prior to response assessment.

RESULTS

Fifty-five patients were enrolled; two were ineligible, two were removed from protocol therapy prior to evaluation for response, and one was inevaluable for response, leaving 53 and 50 patients evaluable for toxicity and response, respectively. Objective responses were seen in 2/20 patients with ESFT (both partial responses, 4 and 19 courses), 0/10 OS patients, and 0/12 STS patients. There were insufficient patients enrolled to determine the response rate for the MB/PNET, astrocytoma, and NB strata. The most common Grade 3 or 4 toxicities during the first course of therapy were thrombocytopenia (12/53), neutropenia (8/53), and fatigue (7/53).

CONCLUSION

Intravenous topotecan by 21-day continuous infusion is tolerable in pediatric patients with recurrent or refractory solid tumors. Limited activity was seen in ESFT and further development of this topotecan schedule as a single agent is not warranted.

Convection-enhanced delivery of Ls-TPT enables an effective, continuous, low-dose chemotherapy against malignant glioma xenograft model

Treatment of malignant gliomas represents one of the most formidable challenges in oncology. The combination of surgery, radiation, and chemotherapy yields median survivals of less than one year. Here we demonstrate the use of a minimally invasive surgical technique, convection-enhanced delivery (CED), for local administration of a novel nanoparticle liposome containing topotecan. CED of this liposomal topotecan (Ls-TPT) resulted in extended brain tissue retention (t1/2 = 1.5 days), whereas free topotecan was rapidly cleared (t1/2 = 0.1 days) after CED. The favorable pharmacokinetic profile of extended topotecan release for about seven days, along with biodistribution featuring perivascular accumulation of the nanoparticles, provided, in addition to the known topoisomerase I inhibition, an effective antiangiogenic therapy. In the rat intracranial U87MG tumor model, vascular targeting of Ls-TPT with CED was associated with reductions in laminin expression and vascular density compared to free topotecan or control treatments. A single CED treatment on day 7 showed that free topotecan conferred no survival benefit versus control. However, Ls-TPT produced a significant (P = 0.0002) survival benefit, with six of seven complete cures. Larger U87MG tumors, where CED of Ls-TPT on day 12 resulted in one of six cures, indicated the necessity to cover the entire tumor with the infused therapeutic agent. CED of Ls-TPT was also efficacious in the intracranial U251MG tumor model (P = 0.0005 versus control). We conclude that the combination of a novel nanoparticle Ls-TPT and CED administration was very effective in treating experimental brain tumors.

A phase II window trial of procarbazine and topotecan in children with high-grade glioma: a report from the children’s oncology group

The role of chemotherapy in the treatment of high-grade gliomas in children is unclear. Early reports were suggestive of improved outcome in children with high-grade glioma with the addition of chemotherapy after surgery and radiation therapy. Subsequent studies did not show similar favorable contribution of chemotherapy to the outcome of these children. Further efforts to identify active chemotherapy agents in children include use of agents that have shown efficacy in adult patients with high-grade glioma and agents that have shown promise in mice bearing human xenografts of brain tumors. A Pediatric Oncology Group (POG 9431) trial tested the activity of two such agents, procarbazine and topotecan in newly diagnosed patients with high-grade glioma who had measurable disease after diagnostic surgery. Neither agent showed efficacy within the confines of the statistical design of the study. This study showed that children with high-grade glioma have an innate resistance to alkylating agents based on mismatch repair deficiency and high levels of alkyguanine transferase (AGT). Future trials should consider strategies to overcome the resistance mechanisms in children with high-grade glioma.

Topotecan Can Compensate for Protracted Radiation Treatment Time Effects in High Grade Glioma Xenografts*

PURPOSE

Several studies reported that prolongation of overall treatment time of fractionated radiotherapy reduces the chance of tumor control. In the present study, we hypothesize that combining topotecan with irradiation could compensate for this detrimental time effect on the radioresponse. Therefore, we investigated the efficiency of different schedules of topotecan (TPT), radiotherapy (RT) or concomitant combination TPT + RT.

METHODS AND MATERIALS

Experiments were performed in two human high-grade glioma xenograft models (U87 and GBM Nan1). TPT and RT were delivered at a total dose of 3 mg/kg and 40 Gy, respectively. For the TPT + RT groups, TPT was injected 5 min before radiation. Total radiation doses were delivered in 5, 10, 20, or 30 fractions over 1, 2, 4, or 6 weeks, respectively. The efficiency of TPT, RT, and TPT + RT was evaluated by tumor growth delay (TGD).

RESULTS

At this low total dose, and independent of the schedule, no efficacy was found in TPT-treated glioma xenografts. Conversely, radiotherapy-induced antitumor effect decreased with prolongation of treatment time. For TPT + RT combination, antitumor activity was not influenced by schedule, and tumor response was always comparable to those measured for the shortest and the most efficient irradiation schedule (i.e. 1 week). When treatment was delivered over 4 or 6 weeks in U87 glioma xenografts, therapeutic enhancement ratios reached 2.6 and 3.7, respectively. This indicated that the interaction between ionizing radiation and topotecan was synergistic.

CONCLUSION

The present study demonstrated that concomitant topotecan can compensate for the detrimental effect of treatment time protraction on radiotherapy efficacy in two malignant glioma xenografts.

Poly(ADP-ribose) polymerase-1 inhibition reverses temozolomide resistance in a DNA mismatch repair–deficient malignant glioma xenograft

Temozolomide is a DNA-methylating agent used in the treatment of malignant gliomas. In this study, we have examined if inhibition of poly(ADP-ribose) polymerase (PARP) could increase the cytotoxicity of temozolomide, particularly in cells deficient in DNA mismatch repair. Athymic mice, transplanted with mismatch repair-proficient [D-245 MG] or deficient [D-245 MG (PR)] xenografts, were treated with a combination of temozolomide and the PARP inhibitor, INO-1001. For the tumors deficient in mismatch repair, the most effective dose of INO-1001 was found to be 150 mg/kg, given i.p. thrice at 4-hour intervals with the first injection in combination with 262.5 mg/kg temozolomide (0.75 LD(10)). This dose of temozolomide by itself induced no partial regressions and a 4-day growth delay. In two separate experiments, the combination therapy increased the growth delay by 21.6 and 9.7 days with partial regressions observed in four of eight and three of nine mice, respectively. The addition of INO-1001 had a more modest, yet statistically significant, increase in tumor growth delay in the mismatch repair-proficient xenografts. In these experiments, mice were treated with a lower amount of temozolomide (88 mg/kg), which resulted in growth delays of 43.1 and 39.2 days. When the temozolomide treatment was in combination with 200 mg/kg INO-1001, there was an increase in growth delay to 48.9 and 45.7 days, respectively. These results suggest that inhibition of PARP may increase the efficacy of temozolomide in the treatment of malignant gliomas, particularly in tumors deficient in DNA mismatch repair.

Topotecan, an active new antineoplastic agent: review and current status

Topotecan (Hycamtin) is a water soluble semisynthetic analogue of the alkaloid camptothecin which has antitumour activity in preclinical models in vitro and in vivo. A range of Phase I studies has been performed and a daily x 5 iv. schedule, which showed most promising evidence of activity, was selected for extensive clinical evaluation. To date, topotecan has been shown to be active in a number of malignancies, including metastatic ovarian cancer, recurrent small cell lung cancer (SCLC), non-small cell lung cancer (NSCLC), breast cancer, colorectal cancer and myelodysplastic syndrome. In ovarian cancer, response rates of around 15% were identified in patients who had failed standard chemotherapy, and in a randomised, comparative study with paclitaxel response rates of 20% (topotecan) and 13% (paclitaxel) were observed. In addition, overall time to progression was impressive at 23 weeks (topotecan) compared with 14 weeks (paclitaxel). In recurrent SCLC, topotecan has shown good activity in sensitive patients with a response rate of 39%, although the response rate in refractory patients was considerably lower (7%). Median survival of all patients was 5.4 months, acceptable for this difficult clinical scenario. Topotecan is well-tolerated in the majority of patients and subjective toxicities are uncommon. The principal side-effect is myelosuppression, mainly neutropenia. Serious clinical sequelae are relatively uncommon and non-cumulative. Nonhaematological toxicities are generally mild and not dose-limiting. In clinical use, topotecan has exhibited activity in multiple tumour types, with a side-effect profile that is predictable and manageable. The drug is under evaluation in other tumour types and in combination chemotherapy regimens.

Efficacy of the novel camptothecin gimatecan against orthotopic and metastatic human tumor xenograft models

PURPOSE

Gimatecan, a novel oral lipophilic camptothecin characterized by favorable features at molecular/cellular level and by a promising profile of preclinical activity, is currently in clinical phase I/II. The aim of the study was to additionally investigate the therapeutic potential of the drug in human tumor xenografts growing in different organs as models representative of tumor growth in the clinical setting.

EXPERIMENTAL DESIGN

The models include two orthotopic central nervous system tumors, two melanomas growing intracranially, and an ovarian carcinoma growing i.p. In addition, gimatecan was tested against experimental lung metastases of two tumor types (lung and ovarian carcinomas). Gimatecan was delivered by oral gavage according to various schedules (daily or intermittent). The time (in days) mice required to show evident signs of disease was used as end point for drug efficacy.

RESULTS

Gimatecan was highly effective in delaying disease manifestations in all tumor systems investigated. In the intracranially growing tumors, a significant time increase (versus control mice) was achieved by the drug administered according to all of the schedules. In addition, almost all treated mice were alive and tumor-free at the end of the experiment in the metastatic models and in the ascitic ovarian tumor. The daily prolonged treatment schedule was the best one.

CONCLUSIONS

In all tumor systems investigated, including orthotopic tumor growth models and lung metastases, the oral administration of gimatecan showed a therapeutic benefit in terms of survival increase. The good oral availability allowed a prolonged daily treatment regimen, which seems the most promising to exploit the therapeutic potential of the drug.

A Phase II trial of paclitaxel and topotecan with filgrastim in patients with recurrent or refractory glioblastoma multiforme or anaplastic astrocytoma

PURPOSE

Therapy for high-grade gliomas remains unsatisfactory. Paclitaxel and topotecan have separately demonstrated activity against gliomas. We conducted a Phase II trial of these agents in combination with filgrastim (G-CSF) in patients with recurrent or refractory glioblastoma multiforme or anaplastic astrocytoma.

PATIENTS AND METHODS

Adult patients with radiographic evidence of recurrent or progressive tumor following primary therapy were eligible for study. Patients received paclitaxel 175 mg/m2 IV over 3 h on day 1 and topotecan 1.0 mg/m2 IV over 30 min on days 1-5. Filgrastim 5 microg/kg was given days 6-14 for neutrophil support. Treatment cycles were repeated every 21 days.

RESULTS

Twenty patients were enrolled on study, and seventeen were considered evaluable for response. Two patients (12/%) exhibited partial remission and seven patients (41/%) exhibited stable disease in response to therapy. Hematologic toxicity was common with 25 /% of patients experiencing grade III or IV leukopenia despite G-CSF support. Two patients died of infectious complications on protocol, prompting suspension of further accrual.

CONCLUSION

Paclitaxel and topotecan with G-CSF support exhibits modest activity in adults with recurrent or refractory glioblastoma and anaplastic astrocytoma. The significant hematotoxicity encountered, however, cannot justify further investigation of this combination in patients with high grade brain tumors.

Phase I study of topotecan in combination with concurrent radiotherapy in adults with glioblastoma

A phase I study was performed to determine the maximum tolerated dose and the recommended dose of continuous intravenous infusion of topotecan in combination with radiotherapy (RT) in patients with previously untreated glioblastoma multiforme (GBM). Twenty patients with histologically proven GBM and 1 with rhabdoid tumor were enrolled. After surgery or stereotactic biopsy, patients received cranial RT (60 Gy/30 fractions/40 days) and 3 cycles of topotecan as continuous infusion (CIV) from day 1 to 5 on weeks 1, 3, and 5 during RT. The dose of topotecan was escalated from 0.6 to 1.0 mg/m2/day. Four dose levels were tested. One grade 4 thrombocytopenia was seen at level 1 (topotecan dose 0.6 mg/m2/day; 6 patients). No dose-limiting toxicity was seen at level 2 (0.8 mg/m2/day; 3 patients) or an intermediate level of 2 bis (0.9 mg/m2/day; 6 patients). Six patients were included at level 3 (1.0 mg/m2/day), 4 of whom experienced dose-limiting toxicities, including 3 episodes of grade 4 thrombocytopenia, 1 platelet transfusion, 1 febrile neutropenia, and 1 grade 4 neutropenia of more than 7 days. Eighty percent of patients with GBM were alive at 12 months. The dose-limiting toxicity of topotecan administered as CIV for 5 days every 2 weeks is hematological. The maximum tolerated dose is 1.0 mg/m2/day and the recommended dose is 0.9 mg/m2/day. A phase II trial using the recommended dose of topotecan is ongoing.

A phase II study of topotecan in patients with anaplastic oligodendroglioma or anaplastic mixed oligoastrocytoma

To determine the efficacy and toxicity of a novel chemotherapeutic approach with topotecan, a camptothecin analog, for progressive or recurring anaplastic oligodendroglioma or mixed oligoastrocytoma.Patients from seven centers with recurrent or progressive disease were treated with topotecan, 1.5 mg/m(2) intravenously (i.v.), 30 min dailyx5 days every 3 weeks. Efficacy and toxicity were assessed clinically and radiologically. The study was planned to accrue up to 30 evaluable patients if there was at least one response among the first 15 patients treated. Sixteen eligible patients entered the study. No response was documented in 14 evaluable patients. Eleven patients had stable disease of a median of 3.8 months and three had progressive disease. Sixteen patients were evaluable for toxicity. The most significant toxic effect was myelosuppression. Grade 3 or 4 granulocytopenia was experienced by 15 of 16 patients and led to dose reduction in nearly half of the cycles delivered. Other adverse effects were fatigue, nausea, stomatitis, alopecia, and vomiting.Topotecan, delivered in the dailyx5 regimen, is relatively well tolerated. We could not demonstrate significant activity among the population studied to justify completing accrual to 30 patients. Topotecan did not demonstrate, with this small sample size, efficacy as a salvage chemotherapy monotherapy after exposure to procarbazine, CCNU and vincristine. Further trials with different agents in this indication are certainly warranted.

The camptothecins

Supported by detailed understanding of their mechanism of action, and facilitated by chemical manipulations that have amplified their solubility, the camptothecins have advanced to the forefront of several areas of therapeutic and developmental chemotherapy. Additive and synergistic laboratory interactions with other cytotoxic drugs have been exploited to allow development of camptothecin-based multidrug regimens, which are showing important activity in several malignancies. Topotecan and irinotecan are already in widespread use in clinical practice, and newer agents with promising preclinical activity are in various stages of clinical assessment. As knowledge of molecular and biochemical mechanisms of action and resistance continues to expand, newer and better camptothecin-based strategies for treatment of malignant disease are likely to evolve.

Phase II study of topotecan plus cranial radiation for glioblastoma multiforme: results of Radiation Therapy Oncology Group 9513

PURPOSE

A Phase II trial was conducted by the Radiation Therapy Oncology Group (RTOG) to compare the survival of patients with glioblastoma multiforme treated with topotecan combined with standard cranial radiotherapy (RT) for matched patients treated in prior RTOG studies. A secondary objective was to document the acute and late toxicities of this combination of chemotherapy and RT.

METHODS AND MATERIALS

Eighty-seven patients with histologically confirmed glioblastoma multiforme received standard cranial RT (60 Gy/30 fractions in 6 weeks) plus topotecan 1.5 mg/m2 per day i.v. for 5 d/wk every 3 weeks for 3 cycles. Eighty-four patients were evaluated, of whom 60 (71%) were > or =50 years, 44 (52%) were men, and 61 (73%) had a Karnofsky performance status of > or =80. Twenty-nine percent of patients had undergone biopsies, 48% partial resections, and 21% gross total resections. Two resections were unspecified as to the extent of tumor removal. Fourteen percent of patients were recursive partitioning analysis Class III, 46% were Class IV, 35% were Class V, and 5% were Class VI.

RESULTS

The median survival was 9.3 months. Sixty-seven patients (80%) had progression. The 1-year survival rate was 32%. One patient remained alive without recurrence. RTOG 9513 patients were matched with patients in an RTOG clinical trial database from previous clinical trials. The matching variables were age, Karnofsky performance status, mental status, and prior surgery. No statistically significant difference was found between the survival of the study patients and that of the matched patients from the RTOG database. Fifty-four percent of patients had Grade IV acute toxicity. The toxicity was primarily hematologic. Four patients had Grade III late central nervous system toxicities.

CONCLUSION

Topotecan administered at a dose of 1.5 mg/m2 per day i.v. for 5 d/wk every 3 weeks for 3 cycles given concurrently with standard cranial RT for glioblastoma does not produce a statistically significant survival advantage over previously tested therapies. Other methods of administration of topotecan or other camptothecins may provide more effective radiosensitization.

Irinotecan for pediatric solid tumors: the Memorial Sloan-Kettering experience

PURPOSE

Irinotecan is a novel antineoplastic agent that works by inhibiting the enzyme, topoisomerase 1. Although not extensively studied in children, preclinical studies and several phase I trials indicate activity against a variety of relapsed solid tumors when administered on a protracted schedule. This report describes an institutional experience with irinotecan for the treatment of pediatric solid tumors.

PATIENTS AND METHODS

Twenty-two heavily pretreated children with multiply relapsed tumors were treated with courses of irinotecan at 20 mg/m2 per day for 10 days [(every day x 5) x 2].

RESULTS

Of the 19 patients evaluable for response, four achieved an objective response, including two complete responses and one partial response among four patients with rhabdomyosarcoma and one additional patient with an undifferentiated sarcoma with rhabdomyoblastic features, and one patient with a fibrosarcoma had stable disease. Among three patients with non-Hodgkin lymphoma, one achieved a partial response and one had stable disease. Diarrhea was the most commonly observed toxicity.

CONCLUSION

Irinotecan appears to have promising single-agent activity, particularly against rhabdomyosarcoma. with minimal hematopoietic toxicity, making it ideal for further evaluation in patients at high risk with newly diagnosed disease, particularly in combination with other active agents with nonoverlapping toxicities.

Topotecan-filgrastim combination is an effective regimen for mobilizing peripheral blood stem cells

We compared the efficacy, toxicity, and cost of topotecan-filgrastim and filgrastim alone for mobilizing peripheral blood stem cells (PBSCs) in 24 consecutive pediatric patients with newly diagnosed medulloblastoma. PBSCs were mobilized with an upfront window of topotecan-filgrastim for 11 high-risk patients (residual tumor > or =1.5 cm2 after resection; metastases limited to neuraxis) and with filgrastim alone for 13 average-risk patients. All patients subsequently underwent craniospinal irradiation and four courses of high-dose chemotherapy with stem cell rescue. Target yields of CD34+ cells (> or =8 x 10(6)/kg) were obtained with only one apheresis procedure for each of the 11 patients treated with topotecan-filgrastim, but with a mean of 2.3 apheresis procedures for only six (46%) of the 13 patients treated with filgrastim alone (P = 0.0059). The median peak and median total yield of CD34+ cells were six-fold higher for the topotecan-filgrastim group (328/microl and 21.5 x 10(6)/kg, respectively) than for the filgrastim group (54/microl and 3.7 x 10(6)/kg, respectively). Mean times to neutrophil and platelet engraftment were similar. Myelosuppression was the only grade 4 toxicity associated with topotecan-filgrastim mobilization and lasted a median of 5 days. Compared with filgrastim mobilization, topotecan-filgrastim mobilization resulted in a mean cost saving of $3966 per patient. Topotecan-filgrastim is an efficacious, minimally toxic, and cost-saving combination for PBSC mobilization.

Phase I study of topotecan plus cranial radiation for glioblastoma multiforme: results of Radiation Therapy Oncology Group Trial 9507

PURPOSE

A phase I trial was conducted by the Radiation Therapy Oncology Group (RTOG) to determine the maximum-tolerated dose of topotecan that could be safely combined with standard cranial radiation for glioblastoma multiforme. A secondary objective was to document the acute and late toxicities of this combination of chemotherapy and radiation.

PATIENTS AND METHODS

Forty-seven patients with histologically confirmed glioblastoma multiforme were entered onto this phase I trial. Three cycles of topotecan were administered at 21-day intervals commencing at day 1 of cranial radiotherapy (60 Gy/30 fractions). Each cycle consisted of daily 30-minute intravenous (IV) infusions for 5 days. The dose of topotecan was escalated in three-dose increments from 0.5 mg/m(2)/d to 1.0 mg/m(2)/d to 1.5 mg/m(2)/d in different patient groups.

RESULTS

The majority of patients were over age 50. Three dose levels of topotecan were tested. Fifteen patients accrued to level 1 (topotecan dose 0.5 mg/m(2)/d). No grade 4 toxicities were seen. Sixteen patients accrued to level 2 (topotecan dose 1.0 mg/m(2)/d), five of whom had brief episodes of grade 4 neutropenia. Seventeen patients accrued to level 3 (1.5 mg/m(2)/d). Six of these patients had brief episodes of grade 4 neutropenia and four developed grade 3 thrombocytopenia. No serious nonhematologic or late toxicities were seen. Median survival for all patients was 9.7 months. There was no apparent difference in survival by topotecan dose schedule.

CONCLUSION

Toxicity was acceptable at an IV topotecan dose of 1.5 mg/m(2)/d administered daily for 5 days every 21 days for three cycles. A phase II trial has been performed using this dose of topotecan.

Clinical presentation, diagnosis, and pharmacotherapy of patients with primary brain tumors

OBJECTIVE

To briefly review the clinical presentation and diagnosis of patients with primary brain tumors, followed by an in-depth survey of the pertinent pharmacotherapy.

DATA SOURCES

A detailed search of the neurologic, neurosurgical, and oncologic literature for basic science research, clinical studies, and review articles related to chemotherapy and pharmacotherapy of primary brain tumors.

STUDY SELECTION

Relevant studies on tissue culture systems, animals, and humans examining the mechanisms of action, pharmacokinetics, clinical pharmacology, and treatment results of chemotherapeutic agents for primary brain tumors. In addition, studies of pharmacologic agents administered for supportive care and symptom control are reviewed.

DATA SYNTHESIS

Primary brain tumors derive from cells within the intracranial cavity and generally present with headache, seizure activity, cognitive changes, and weakness. They are diagnosed most efficiently with magnetic resonance imaging. After diagnosis, the most common supportive medications include corticosteroids, gastric acid inhibitors, and anticonvulsants. Chemotherapy is adjunctive treatment for patients with malignant tumors and selected recurrent or progressive benign neoplasms. In general, the most effective chemotherapeutic drugs are alkylating agents such as the nitrosoureas, procarbazine, cisplatin, and carboplatin. Other agents used include cyclophosphamide, methotrexate, vincristine, and etoposide. Angiogenesis inhibitors and gene therapy comprise some of the novel therapeutic strategies under investigation.

CONCLUSIONS

The efficacy of chemotherapy for primary brain tumors remains modest. Novel agents must be discovered that are more specific and attack tumor cells at the molecular level of tumorigenesis. Furthermore, strategies must be developed to counteract the pervasive problem of brain tumor chemoresistance.

Topotecan for the treatment of recurrent or progressive central nervous system tumors - a pediatric oncology group phase II study

Topotecan was studied as a 72 h infusion given every 3 weeks. Treatment began at a dose of 1.0 mg/m2/day and was increased to 1.25 mg/m2/day after the first 6 patients tolerated this higher dose without excessive toxicities. Eighty-eight evaluable children were accrued in 6 strata. There were no complete nor partial responses. Twenty subjects had stable disease (astrocytoma 5/11, malignant glioma 5/13, medulloblastoma 0/12, brain stem tumor 4/19, ependymoma 5/17, and miscellaneous histologies 1/16). Two patients (astrocytoma, ependymoma) completed the maximum 18 topotecan courses. The remaining 68 children developed progressive disease within 2 months. Myelosuppression was the main toxicity. Grade 4 leukopenia, neutropenia, anemia, and thrombocytopenia were observed in 18, 32, 5, and 23 participants, respectively. It was concluded that topotecan as given according to this schedule showed insufficient activity to promote it to frontline protocol usage.

The accumulation of topotecan in 9L glioma and in brain parenchyma with and without dexamethasone administration

The accumulation of the topoisomerase I inhibitor topotecan in brain tumor as well as in brain around tumor (BAT) and normal brain following an intravenous bolus of topotecan of 0.5 mg/kg was investigated in rats bearing a 9L glioma. Also the influence of dexamethasone (Dex) on the uptake of topotecan was examined. Tumor, BAT and brain tissue as well as whole blood were collected at 1 h after an i.v. bolus of topotecan. Concentrations of total topotecan in tumor, BAT and brain were quantified with high-performance liquid chromatography (HPLC) and compared with concentrations in plasma of total topotecan. In brain tumor tissue the mean total topotecan concentration was 96 +/- 33 ng/g which was 20-fold higher than the accumulation of topotecan in normal brain tissue. In BAT intermediate concentrations of 13 +/- 4.9 ng/g were reached. Mean total topotecan concentration in plasma was 100 +/- 25 ng/ml. We did not find an influence of Dex on the uptake of topotecan in either tissue. We conclude that high tissue concentrations of topotecan can be reached in experimental brain tumors in rats. This observation may be useful in the design of clinical studies with topotecan.

Clinical pharmacology of camptothecins

Camptothecins (CPTs) are a unique class of chemotherapeutic agent which inhibit DNA synthesis by inhibiting topoisomerase I activity. Structure-activity studies on the original CPT alkaloid led to the development of the new analogues irinotecan (CPT-11), topotecan, and 9-aminocamptothecin, which have improved water solubility and lower toxicity. CPT analogues exhibit interesting pharmacokinetic/pharmacodynamic and metabolic properties that are of major research and clinical interest. This review describes the clinical pharmacology of these 3 CPT analogues. Specific areas such as absorption after extravascular administration, pharmacokinetic/pharmacodynamic variability, metabolism, and administration in special populations are discussed.

Topoisomerase I inhibitors and drug resistance

DNA topoisomerase I is a nuclear enzyme which catalyzes the conversion of the DNA topology by introducing single-strand breaks into the DNA molecule. This enzyme represents a novel and distinct molecule target for cancer therapy by antitopoisomerase drugs belonging to the campthotecin series of antineoplastics. As many tumors can acquire resistance to drug treatment and become refractary to the chemotherapy it is very important to investigate the mechanisms involved in such a drug resistance for circumventing the phenomenon. This article describes the role of topoisomerase I in cell functions and the methods used to assess its in vitro catalytic activity. It reviews the mechanisms of cytotoxicity of the most specific antitopoisomerase I drugs by considering also the phenomenon of drug resistance. Some factors useful to drive the future perspectives in the development of new topoisomerase I inhibitors are also evidenced and discussed.

Relationship between topotecan systemic exposure and tumor response in human neuroblastoma xenografts

BACKGROUND

Topotecan is a topoisomerase I inhibitor with activity against xenografts of childhood solid tumors and established clinical activity against neuroblastoma and rhabdomyosarcoma. We have studied the relationship between systemic exposure to and the antitumor activity of topotecan lactone (the active form of the drug) in the xenograft models. Furthermore, we determined whether the responses seen in these models occur at systemic exposure levels that are tolerable in children.

METHODS

Neuroblastoma xenografts derived from the tumors of six different patients were established subcutaneously in immune-deprived mice. Topotecan was administered by intravenous bolus injection 5 days a week for 2 consecutive weeks, repeated every 21 days for three cycles. The minimum daily doses that induced complete responses (CRs) and partial responses (PRs) were determined. Topotecan lactone pharmacokinetic studies were performed in both tumor-bearing and nontumor-bearing mice.

RESULTS

The minimum doses associated with CRs and PRs in four of the six neuroblastoma xenografts were 0.61 and 0.36 mg/kg body weight, respectively. The topotecan lactone single-day systemic exposures associated with these doses were 88 and 52 ng x hr/mL, respectively. There was an approximately sixfold difference in topotecan lactone systemic exposure (290 ng x hr/mL versus 52 ng x hr/mL) associated with achieving CRs in the least-sensitive and most-sensitive tumors, respectively.

CONCLUSIONS

Neuroblastoma xenografts are highly sensitive to topotecan therapy, and responses in mice are achieved at systemic exposures similar to those that are clinically effective and tolerable in children. These results support the concept of deriving preclinical data relating systemic exposure to antitumor activity in xenograft models. Such data may be valuable in making informed decisions regarding the clinical development of new agents.

Preclinical development of camptothecin derivatives and clinical trials in pediatric oncology

Although the prognosis of childhood cancers has dramatically improved over the last three decades, new active drugs are needed. Camptothecins represent a very attractive new class of anticancer drugs to develop in paediatric oncology. The preclinical and clinical development of two of these DNA-topoisomerase I inhibitors, i.e. topotecan and irinotecan, is ongoing in paediatric malignancies. Here we review the currently available results of this evaluation. Topotecan proved to be active against several paediatric tumour xenografts. In paediatric phase I studies exploring several administration schedules, myelosuppression was dose-limiting. The preliminary results of topotecan evaluation in phase II study showed antitumour activity in neuroblastoma (response rate: 15% at relapse and 37% in newly diagnosed patients with disseminated disease) and in metastatic rhabdomyosarcoma (40% in untreated patients). Topotecan-containing drug combinations are currently investigated. Irinotecan displayed a broad spectrum of activity in paediatric solid tumour xenografts, including rhabdo-myosarcoma, neuroblastoma, peripheral primitive neuroectodermal tumour, medulloblastoma, ependymoma, malignant glioma and juvenile colon cancer. For several of these histology types, tumour-free survivors have been observed among animals bearing an advanced-stage tumour at time of treatment. The clinical evaluation of irinotecan in children is ongoing. Irinotecan undergoes a complex in vivo biotransformation involving several enzyme systems, such as carboxylesterase, UDPGT and cytochrome P450, in children as well as in adults. Preclinical studies of both drugs have shown that their activity was schedule-dependent. The optimal schedule of administration is an issue that needs to be addressed in children. In conclusion, the preliminary results of the paediatric evaluation of camptothecin derivatives show very encouraging results in childhood malignancies. The potential place of camptothecins in the treatment of paediatric malignant tumours is discussed.

DNA-topoisomerase I, a new target for the treatment of neuroblastoma

DNA-topoisomerase I is the nuclear target of new anticancer drugs, namely camptothecin and its derivatives. In order to establish the rational basis for their clinical development in paediatric oncology, the antitumour activity of irinotecan (CPT-11) and topotecan, two camptothecin water-soluble derivatives, was studied in nude mice bearing neuroblastoma xenografts. The panel was composed of 4 previously established subcutaneous xenograft lines (IGR-N835, IGR-N91, IGR-NB3, IGR-NB8) that exhibited the common biological markers of poor prognosis in children (MYCN amplification, 1p deletion, paradiploidy and/or MDR1 overexpression). Irinotecan and topotecan were administered i.v. or i.p. over 5 consecutive days in animals bearing tumours. Irinotecan (40 mg/kg/day) induced 20-100% complete regressions with tumour growth delays ranging from 20 to 46 days. Two out of 10 IGR-N91 bearing animals were tumour free more than 120 days after treatment with the top dose (50 mg/kg/day). Topotecan (2.7 mg/kg/day) induced 0-67% complete regressions with tumour growth delays ranging from 23 to 50 days. One out of 8 IGR-NB3 bearing mice was tumour free at the end of the experiment. The antitumour activity of both drugs was clearly sustained at a lower dose level. Topoisomerase I activity was assayed in 15 neuroblastomas, 3 ganglioneuroblastomas and 2 normal adrenal glands, using a DNA relaxation assay. Topoisomerase I activity ranged from 69 to 1304 arbitrary units/mg of protein, and was significantly higher in immature neuroblastomas than in ganglioneuroblastomas and adrenal glands. In conclusion, irinotecan and topotecan are active against neuroblastoma xenografts. Their target is expressed in patients' tumour samples. Clinical development of topoisomerase I inhibitors in children with neuroblastoma is warranted.

Cytotoxic activity of topotecan in human tumour cell lines and primary cultures of human tumour cells from patients

The cytotoxic activity and cross-resistance pattern of the novel topoisomerase I inhibitor topotecan (Topo) were investigated in ten cell lines, representing different mechanisms of cytotoxic drug resistance, and in 218 fresh human tumour samples using the fluorometric microculture cytotoxicity assay (FMCA). Resistance to Topo in the cell lines was associated with expression of the multidrug resistance-associated protein (MRP), whereas the cell lines with P-glycoprotein (P-gp), topoisomerase II and glutathione-associated resistance did not show decreased sensitivity to the drug. Topo was more active in haematological than in solid tumour samples, but substantial activity was observed in carcinomas of the ovary and breast, sarcoma and childhood solid tumours. Cross-resistance to standard drugs representing different mechanisms of action was generally low in patient cells. The effect of Topo was better after longer exposure, but this time-dependent effect was largely abolished when adjustment for in vitro exposure was made. Topo showed activity both in proliferative and non-proliferative cell systems. The results indicate that Topo is insensitive to major mechanisms of resistance except for MRP. Proliferation does not seem to be necessary for the effect of Topo, and no superiority for protracted dosing schedules was observed. The results also suggest that, for example, leukaemias, lymphomas, sarcomas and childhood solid tumours may be suitable targets for future phase II trials.

Phase II evaluation of topotecan for pediatric central nervous system tumors

BACKGROUND

Topotecan is a topoisomerase I inhibitor that has good penetration across the blood-brain barrier and significant antitumor activity against human brain tumor xenografts. In a Phase I trial in children with refractory cancer, topotecan was well tolerated when administered as a 24-hour infusion. The maximum tolerated dose was 5.5 mg/m2 and the dose-limiting toxicity was myelosuppression. This Phase II study of topotecan was performed to assess the activity of topotecan against childhood brain tumors.

METHODS

Forty-five children with either a previously treated primary brain tumor that was refractory to standard therapy, or an untreated brain stem glioma or glioblastoma multiforme, received topotecan administered as a 24-hour intravenous infusion every 21 days. The initial dose was 5.5 mg/m2 with escalation to 7.5 mg/m2 on the second and subsequent doses in patients who did not experience dose-limiting toxicity.

RESULTS

There were no complete or partial responses in the patients with high grade glioma (n=9), medulloblastoma (n=9), or brain stem glioma (n=14). One of 2 patients with a low grade glioma had a partial response lasting more than 17 months; 3 patients with a brain stem glioma had stable disease for 12 to 28 weeks; and 1 patient with a malignant neuroepithelial tumor and 1 patient with an optic glioma had stable disease for 41 weeks and 22 weeks, respectively. Dose escalation from 5.5 mg/m2 to 7.5 mg/m2 was well tolerated in the first 11 patients enrolled on this study who had not received prior craniospinal radiation therapy. The starting dose was subsequently increased to 7.5 mg/m2 for patients without prior craniospinal radiation.

CONCLUSIONS

Topotecan administered as a 24-hour infusion every 21 days is inactive in high grade gliomas, medulloblastomas, and brain stem tumors.

Current perspectives on camptothecins in cancer treatment

The camptothecins are a new class of chemotherapeutic agents which have a novel mechanism of action targeting the nuclear enzyme topoisomerase I. Knowledge of the structure-activity relationships of the parent compound camptothecin has led to the development of effective soluble analogues with manageable toxicities. Broad anti-tumour activity shown in preclinical studies has been confirmed in phase I/II studies for irinotecan and topotecan. Two other derivatives, 9-aminocamptothecin and GI 147211C, are undergoing phase I and early phase II evaluation. Although camptothecin is a plant extract, it and most of its derivatives are not affected by the classic P-gpMDR1 mechanism of resistance which may allow the development of novel combination chemotherapeutic regimens. Important areas of future endeavour will include the development of rational combination regimens and the pursuit of randomised trials. Based on single agent data, colorectal cancer and non-small-cell lung cancer should be the focus for future irinotecan studies. Small-cell lung cancer and ovarian carcinoma are logical tumour types to pursue with topotecan. Both 9-aminocamptothecin and GI 147211C are too early in their clinical evaluation to make recommendations about their future roles. Finally, the unfolding story of camptothecin analogue development will give important insights into the predictive value of preclinical observations on relative efficacy, schedule dependency, combination strategies and resistance mechanisms which have helped determine the strategies for clinical evaluation of these agents.

Pediatric drug development: a perspective from the Cancer Therapy Evaluation Program (CTEP) of the National Cancer Institute (NCI)

Well-designed and carefully conducted pediatric phase 1 trials are critical to the process of evaluating new agents for potential benefit in children with cancer, and the National Cancer Institute (NCI) has for a number of years sponsored pediatric phase I trials. The development of new agents for children with cancer differs in important ways from drug development for adults with cancer, primarily necessitated by the smaller number of children eligible for phase I trials in comparison to adults. Pediatric drug development is characterized by a greater need to prioritize new agents for evaluation, since many more agents can be evaluated in adults than can be evaluated in children. Pediatric phase I trials are also commonly conducted as multi-institutional collaborations, since most single institutions do not have enough eligible patients to complete phase I trials within a reasonable time. In addition, pediatric phase I trials begin at doses close to the adult maximum tolerated dose, thereby minimizing the number of patients required to complete pediatric phase I trials. While pediatric phase I trials have traditionally evaluated conventional cytotoxic agents, new classes of agents with distinctive mechanisms of action are entering clinical evaluation. These agents target specific cellular proteins (e.g., protein tyrosine kinases, protein kinase C isoforms, enzymes involved in controlling progression through the cell cycle). Determining whether these agents with specificity for critical cellular proteins will be effective anti-cancer agents will be an important objective of pediatric clinical investigations in the coming years.

Topoisomerase I interactive drugs in children with cancer

Topotecan, irinotecan, and 9-aminocamptothecin (9-AC) are analogs of the plant alkaloid 20(S)-camptothecin (CMT), the prototypical DNA topoisomerase I interactive agent. These agents interact with the topoisomerase I-DNA complex and prevent resealing topoisomerase I-mediated DNA single-strand breaks. This eventual leads to double-strand DNA breaks and apoptosis or cell death. Topotecan, irinotecan, and 9-AC have shown significant activity in mice bearing pediatric solid tumor xenografts; the greatest antitumor responses were found with protracted continuous schedules. Preclinical data also suggest that maintenance of an exposure-duration threshold (EDT) may be required to achieve optimal cytotoxicity. Pediatric Phase I trials have evaluated the toxicity and safety to camptothecin analogs in children with relapsed solid tumors and relapsed acute leukemia. The primary dose-limiting toxicity (DLT) for the CMT analogs in children has been myelosuppression, except for mucositis observed with the 120-hr continuous topotecan infusion schedule. Pharmacodynamic relationships with these analogs have been reported between systemic exposure, and myelosuppression and mucositis. Although not a primary objective of the early Phase I studies, antitumor responses have been reported. In this review, the pharmacokinetic and pharmacodynamics of the CMT analogs studied in children are summarized, and future studies of these agents are discussed.