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Relapsed small cell lung cancer (SCLC) carries a poor prognosis. Topoisomerase I and II inhibitors and DNA-damaging agents are considered among the most active agents against SCLC. Rebeccamycin analog (RA, Becatecarin) is an antitumor antibiotic with inhibitory activity against both topoisomerase I and II, and DNA-intercalating properties. We performed a phase-II trial of RA in relapsed, sensitive SCLC with the primary end point of response rate. Patients with previously treated SCLC who relapsed more than 60 days after the completion of first-line chemotherapy were treated with RA-administered intravenously at a dose of 140 mg/m on days 1 to 5 of 21-day cycles for a maximum of six cycles. Eligibility included Eastern Cooperative Oncology Group performance status 0 to 2 and adequate organ function. A two-stage design was employed. Twenty evaluable patients were enrolled. Median age was 61 years. Two patients (10%) had a partial response and six had stable disease. The clinical benefit rate was 40% (95% confidence interval [CI], 23-64%). The median progression-free survival was 2 months (95% CI, 1.2-5.2 months). The median survival was 6.7 months (95% CI, 3.3-8.0 months). No treatment-related deaths occurred. Grade-4 neutropenia and thrombocytopenia occurred in 23% and 14% of the patients, respectively. In conclusion, RA has single-agent activity in relapsed, sensitive SCLC with manageable toxicities but is unlikely to provide any superiority compared to existing agents for this disease.

Topoisomerase I is a privileged target for widely used anticancer agents such as irinotecan. Although these drugs are classically considered to be DNA-damaging agents, increasing evidence suggests that they might also influence the tumor environment. This study evaluates in vivo cellular and molecular modifications induced by irinotecan, a topoisomerase I-directed agent, in patient-derived colon tumors subcutaneously implanted in athymic nude mice. Irinotecan was given intraperitoneally at 40 mg/kg five times every 5 d, and expression profiles were evaluated at d 25 in tumors from treated and untreated animals. Unexpectedly, the in vivo antitumor activity of irinotecan was closely linked to a downregulation of hypoxia-inducible factor-1α (HIF1A) target genes along with an inhibition of HIF1A protein accumulation. The consequence was a decrease in tumor angiogenesis leading to tumor size stabilization. These results highlight the molecular basis for the antitumor activity of a widely used anticancer agent, and the method used opens the way for mechanistic studies of the in vivo activity of other anticancer therapies.

CKD-602 (7-[2-(N-isopropylamino)ethyl]-(20S)-camptothecin, belotecan), a novel synthetic water-soluble camptothecin derivative, is known to have a significant anticancer effect in vitro on human glioma cell lines, including U87MG and U251MG. In the present study, we evaluated the in vivo antitumor effect of CKD-602 in a mouse glioma model. Nude mice with established U87MG glioma were treated with a dose of CKD-602 of 0mg/kg (control group, injection with saline only; n=5), 40 mg/kg (group A) or 60 mg/kg (group B). Thereafter, the dose was repeated once every 4 days for a total of four doses. Tumor volume was measured histologically and apoptosis was detected using the terminal deoxynucleotide transferase dUTP nick end labeling (TUNEL) assay and immunofluorescence analysis with cleaved caspase-3. Mean tumor volume in each group was: control, 145.35 mm(3); group A, 76.51 mm(3); group B, 73.99 mm(3)). Tumor volume was significantly smaller in both groups A and B compared with the control group (group A, p<0.01; group B, p<0.05). Apoptosis of tumor cells was evident to a greater extent in groups A and B relative to the control group, but there were no significant differences in tumor volume or apoptotic index between groups A and B. These results suggest that CKD-602 has a significant anticancer effect on glioma cells in vivo., (Copyright © 2011 Elsevier Ltd. All rights reserved.)

Background: Genz-644282 is a novel non-camptothecin topoisomerase I poison that is in clinical development., Procedures: Genz-644282 was tested against the PPTP in vitro panel (0.1 nM to 1 µM), and in vivo using three times per week × 2 schedule repeated at day 21 at its maximum tolerated dose (MTD) of 4 mg/kg. Subsequently Genz-644282 was tested at 4, 3, 2, and 1 mg/kg in 3 models to assess the dose-response relationship. mRNA gene signatures predictive for Genz-644282 response in vitro were applied to select 15 tumor models that were evaluated prospectively., Results: In vitro, Genz-644282 demonstrated potent cytotoxic activity with a median IC(50) of 1.2 nM (range 0.2-21.9 nM). In vivo, Genz-644282 at its MTD (4 mg/kg) induced maintained complete responses (MCR) in 6/6 evaluable solid tumor models. At 2 mg/kg Genz-644282 induced CR or MCR in 3/3 tumor models relatively insensitive to topotecan, but there were no objective responses at 1 mg/kg. Further testing at 2 mg/kg showed that Genz-644282 induced objective regressions in 7 of 17 (41%) models. There was a significant correlation between predictive response scores based on Affymetrix U133Plus2 baseline tumor expression profiles and the observed in vivo responses to Genz-644282., Conclusions: Genz-644282 was highly active within a narrow dose range (2-4 mg/kg), typical of other topoisomerase I poisons. As with other topoisomerase I poisons, how accurately these data will translate to clinical activity will depend upon the drug exposures that can be achieved in children treated with this agent., (Copyright © 2011 Wiley Periodicals, Inc.)

The topoisomerase I (Top 1) poison irinotecan is an important component of the modern treatment of colorectal cancer. By stabilising Top 1-DNA complexes, irinotecan generates Top 1-linked DNA single-strand breaks that can evolve into double-strand breaks and ultimately cause cell death. However, cancer cells may overcome cell killing by releasing the stalled topoisomerase from DNA termini, thereby reducing the efficacy of Top 1 poisons in clinics. Thus, understanding the DNA repair mechanisms involved in the repair of Top 1-mediated DNA damage provides a useful tool to identify potential biomarkers that predict response to this class of chemotherapy. Furthermore, targeting these pathways could enhance the therapeutic benefits of Top 1 poisons. In this review, we describe the cellular mechanisms and consequences of targeting Top 1 activity in cells. We summarise preclinical data and discuss the potential clinical utility of small-molecule inhibitors of the key proteins.

Many anticancer drugs reduce the integrity of DNA, forming strand breaks. This can cause mutations and cancer or cell death if the lesions are not repaired. Interestingly, DNA repair-deficient cancer cells (e.g., those with BRCA1/2 mutations) have been shown to exhibit increased sensitivity to chemotherapy. Based on this observation, a new therapeutic approach termed 'synthetic lethality' has been developed, in which radiation therapy or cytotoxic anticancer agents are employed in conjunction with selective inhibitors of poly(ADP-ribose)polymerase-1 (PARP-1). Such combinations can cause severe genomic instability in transformed cells resulting in cell death. The synergistic effects of combining PARP-1 inhibition with anticancer drugs have been demonstrated. However, the outcome of this therapeutic strategy varies significantly between cancer types, suggesting that synthetic lethality may be influenced by additional cellular factors. This review focuses on the outcomes of the combined action of PARP-1 inhibitors and agents that affect the activity of DNA topoisomerases.

BRCA1 dysfunction in hereditary breast cancer causes defective homology-directed DNA repair and sensitivity towards DNA damaging agents like the clinically used topoisomerase I inhibitors topotecan and irinotecan. Using our conditional K14cre;Brca1(F/F);p53(F/F) mouse model, we showed previously that BRCA1;p53-deficient mammary tumors initially respond to topotecan, but frequently acquire resistance by overexpression of the efflux transporter ABCG2. Here, we tested the pegylated SN38 compound EZN-2208 as a novel approach to treat BRCA1-mutated tumors that express ABCG2. We found that EZN-2208 therapy resulted in more pronounced and durable responses of ABCG2-positive tumors than topotecan or irinotecan therapy. We also evaluated tumor-specific ABCG2 inhibition by Ko143 in Abcg2(-/-) host animals that carried tumors with topotecan-induced ABCG2 expression. Addition of Ko143 moderately increased overall survival of these animals, but did not yield tumor responses like those seen after EZN-2208 therapy. Our results suggest that pegylation of Top1 inhibitors may be a useful strategy to circumvent efflux transporter-mediated resistance and to improve their efficacy in the clinic.

Irinotecan and topotecan are derivatives of the naturally occurring cytotoxic compound camptothecin that are used in the treatment of patients with colorectal cancer, either as single agents or in combination with radiotherapy and/or other chemotherapy drugs. They are inhibitors of DNA topoisomerase I (Top I) and exert their cytotoxic effects in replicating cells by inducing DNA strand breaks. A wide range of DNA repair proteins is involved in the recognition and repair of these breaks, and depletion or inhibition of some of these proteins increases the cytotoxic effects of Top I inhibitors. Building on these laboratory observations, ongoing translational research is aiming to establish whether this mechanistic information can be used to improve the treatment of patients with certain types of cancer. Two potential strategies are under investigation: (1) individualising treatment by evaluating levels and/or patterns of expression of DNA repair proteins that predict clinical response to Top I inhibitors, and (2) developing small molecule inhibitors of these repair enzymes to overcome tumour resistance and improve outcomes. This review summarises the current status of these research endeavours, focusing on the key roles of tyrosyl DNA phosphodiesterase 1 (Tdp1) and poly(ADP-ribose) polymerase (PARP), and examines the pre-clinical and clinical data that support the potential value of these and other DNA repair proteins as predictive markers and therapeutic targets. Since irinotecan is increasingly being combined with radiotherapy, the potential for these proteins to act as predictive biomarkers for both Top I inhibitors and radiation is proposed, and the possibility of synergistic potentiation of chemoradiation regimes by Tdp1 and/or PARP inhibitors is considered.

Achieving effective treatment outcomes for patients with glioblastoma (GBM) has been impeded by many obstacles, including the pharmacokinetic limitations of antitumor agents, such as topotecan (TPT). Here, we demonstrate that intravenous administration of a novel nanoliposomal formulation of TPT (nLS-TPT) extends the survival of mice with intracranial GBM xenografts, relative to administration of free TPT, because of improved biodistribution and pharmacokinetics of the liposome-formulated drug. In 3 distinct orthotopic GBM models, 3 weeks of biweekly intravenous therapy with nLS-TPT was sufficient to delay tumor growth and significantly extend animal survival, compared with treatment with free TPT (P ≤ .03 for each tumor tested). Analysis of intracranial tumors showed increased activation of cleaved caspase-3 and increased DNA fragmentation, both indicators of apoptotic response to treatment with nLS-TPT. These results demonstrate that intravenous delivery of nLS-TPT is a promising strategy in the treatment of GBM and support clinical investigation of this therapeutic approach.

Topotecan, a semi-synthetic camptothecin analogue with topoisomerase I interaction, has shown to be an active agent in the treatment of advanced refractory lung cancer. This paper describes the authors' experience with this drug when used as a single agent in patients (pts) with advanced non-small cell lung cancer (NSCLC) refractory to platinum- and taxane-containing chemotherapy regimens. Thirty-five patients with NSCLC refractory to previous chemotherapy and KI ≥ 60% were included in the study. Their characteristics are as follows: median age of 52 years (range 43-69) and Karnofsky PS of 70 (60-80); 27 were male and 8 were female. Twenty-one (60%) patients had adenocarcinoma; eleven (31.4%), squamous cell, and three (8.5%), undifferentiated carcinoma. There was a median of two disease sites and two prior chemotherapy regimens. Topotecan was administered at a dose of 1.25 mg/m(2) I.V. daily for 5 days, repeated every 21 days until disease progression, maximal response, or intolerable toxicity. After 73 cycles, patients received a median of 2 treatment cycles (1-9). All patients except one were considered evaluable for toxicity; eight episodes (24%) of nausea/vomiting and two episodes (6%) of grade 1-2 asthenia, respectively, were reported. Four (12%) patients developed grade 1-2 anemia and two (6%) subjects suffered grade 3 anemia. Seven (21%) patients had grade 1-2 neutropenia and one (3%) presented grade 5 neutropenia. In 33 patients evaluable for activity of the 35 subjects included in the study; one (2.8%) presented a partial response; nine (25.7%) had stable disease, and 23 (65.7%) exhibited disease progression. Median time to progression and overall survival were 54 (12-210) and 70 (12-324) days, respectively. Intravenous topotecan at that dose and administration schedule displays scant activity in terms of response rate in individuals with advanced NSCLC previously treated with platinum and taxanes. The role and usefulness of chemotherapy in this setting warrants further investigation and confirmation through comparative studies.

Nuclear topoisomerase I (Top1) is involved in the relaxation of DNA supercoiling and plays a pivotal role in the coordination of essential DNA processes such as transcription, replication, DNA recombination and DNA damage signalling. For all these reasons, Top1 has been an attractive target for the development of anticancer drugs, which poison Top1 by trapping the enzyme on its DNA cleavage sites, which results in irreversible DNA lesions that are responsible for their cytotoxicity. They derive from the natural compound camptothecin and two derivatives are approved in the clinic, topotecan and irinotecan; other compounds such as indolocarbazoles and indenoisoquinolines are in development. However, the efficacy of these drugs is often limited by the problem of resistance, which involves various mechanisms at different steps of drug action, from drug transport and/or metabolism to the signalling and/or repair of the DNA lesions that are generated. A better understanding of these mechanisms is a major concern for the future development of new Top1 inhibitors and the identification of biomarkers that could be used to predict tumour response to these drugs in the clinic and to adapt the treatment to each patient.

Objective: To evaluate the efficacy of topoisomerase I inhibitor, topotecan, in patients with recurrent BRCA+ versus BRCA- ovarian, fallopian tube, and primary peritoneal carcinomas., Methods: A single-institution retrospective analysis of platinum-resistant patients characterized for the presence or absence of known deleterious BRCA mutations. Patients received topotecan at a dose and schedule determined by their treating physician (five day or weekly). Response rate and progression-free survival (PFS) were assessed., Results: A total of 50 patients (9 BRCA+, 41 BRCA-) were treated with topotecan. Both groups were well balanced in terms of age, stage, grade, and number of prior therapies. All patients had high-grade serous carcinoma. The clinical benefit rate in BRCA+ and BRCA- patients was 0% and 26.8% (6 PRs, 6 SDs), respectively (p=0.18). Median PFS in BRCA+ and BRCA- pts was 1.7 months (95% CI: 1.0-2.8 months) and 2.5 months (95%CI: 1.9-2.8 months), respectively (p=0.057). Median time to best response was 1.9 months, and median response duration 2.6 months., Conclusions: This analysis in a heavily pretreated cohort of patients fails to support the superiority of topotecan in BRCA+ platinum-resistant ovarian, fallopian tube, and primary peritoneal cancers. Further study of this class of agents, specifically in less heavily-pretreated patients, may still be warranted., (Copyright © 2011 Elsevier Inc. All rights reserved.)

Introduction: This review covers the preclinical and clinical activity of the novel camptothecin analog, karenitecin, in melanoma., Areas Covered: While the camptothecins are widely used antitumor agents that inhibit topoisomerase I, their utility is limited by instability, high interpatient variability and the development of drug resistance. Karenitecin was rationally designed to overcome these limitations. The authors review the data on karenitecin in preclinical models and in clinical trials in melanoma using studies published in Medline and reports presented at AACR and ASCO., Expert Opinion: Karenitecin shows activity in melanoma, both as a single agent and in combination. In adverse prognostic factor melanoma, karenitecin showed prolonged disease stabilization in 34% of patients. Because preclinical studies suggested a synergistic interaction between karenitecin and HDAC inhibitors, a schedule-specific combination Phase I-II trial of valproic acid and karenitecin was carried out in heavily pretreated melanoma patients which showed a benefit rate in 47% patients with acceptable toxicity. The treatment for melanoma is in rapid transition and genomic profiling is now an integral part, and hence the optimal use of karenitecin in melanoma should be re-evaluated with regard to specific mutational status.

Irinotecan (CPT-11) is used as a first- and second-line chemotherapy for advanced or recurrent colorectal cancer (CRC). However, only 20%-30% of patients show an objective response to CPT-11 and the drug has severe toxicities, such as delayed-onset diarrhea, neutropenia, nausea, and vomiting. It is important to select patients who will demonstrate sensitivity to CPT-11 treatment to avoid unnecessary drug toxicities and to introduce anticancer treatment benefits to CRC patients. DNA topoisomerase I (Topo I) is essential for vital cellular processes such as DNA replication, transcription, translation, recombination, and repair. This article reviews the possibility of assessing Topo I protein expression in tumors as a biological marker for CPT-11 treatment in CRC.

Inhibitors of topoisomerase I (Top1) that result in stalled Top1 cleavage complexes (Top1cc) are commonly employed against cancer. Combination chemotherapy with DNA repair inhibitors can potentially improve response to these widely used chemotherapeutics. One line of inquiry focuses on inhibitors of tyrosyl-DNA phosphodiesterase 1 (Tdp1), a repair enzyme for Top1cc. Tdp1 catalyzes the hydrolysis of DNA adducts covalently linked to the 3'-phosphate of DNA, including Top1-derived peptides and also 3'-phosphoglycolates. Tdp1 inhibitors should synergize not only with Top1-targeting drugs (camptothecins, indenoisoquinolines), but also with bleomycin, topoisomerase II (Top2) inhibitors (etoposide, doxorubicin) and DNA alkylating agents. Here, we summarize the structure-activity relationship obtained from the reported Tdp1 inhibitors. Better understanding of Top1cc repair in vivo coupled with detailed structural studies on Tdp1-inhibitor interaction will be crucial in guiding the rational design of Tdp1 inhibitors.

Purpose: Low dose metronomic (LDM) chemotherapy, combined with VEGF signaling pathway inhibitors, is a highly effective strategy to coordinately inhibit angiogenesis and tumor growth in many adult preclinical cancer models. We have tested the efficacies of daily oral LDM topotecan alone and in combination with pazopanib, a VEGF receptor inhibitor, in three pediatric extracranial solid tumor mouse models., Experimental Design: In vitro dose-response study of topotecan and pazopanib was conducted on several neuroblastoma, osteosarcoma, and rhabdomyosarcoma cell lines. In vivo antitumor efficacies of the LDM topotecan and pazopanib as single agents and in combination were tested on 4 subcutaneous xenograft models and on 2 neuroblastoma metastatic models. Circulating angiogenic factors such as circulating endothelial cells (CEC), circulating endothelial pro genitor cells (CEP), and microvessel densities were used as surrogate biomarker markers of antiangiogenic activity., Results: In vitro, topotecan caused a dose-dependent decrease in viabilities of all cell lines, while pazopanib did not. In vivo, combination of topotecan + pazopanib (TP + PZ) showed significant antitumor activity and significant enhancement in survival compared with the respective single agents in all models. Reductions in viable CEP and/or CEC levels and tumor microvessel density were correlated with tumor response and therefore confirmed the antiangiogenic activity of the regimens. Pharmacokinetic studies of both drugs did not reveal any drug-drug interaction., Conclusion: Metronomic administration of TP + PZ showed a statistically significant antitumor activity compared with respective single agents in pediatric tumor mouse models and represent a valid option as a maintenance therapy in aggressive pediatric solid tumors., (©2011 AACR.)

Purpose: Differences in efficacy and toxicity between UDP-glucuronosyltransferase (UGT) 1A1*1/*1 and *1/*6 or *1/*28 genotypes remain unclear in Japanese patients., Methods: Patients with advanced colorectal cancer who received irinotecan combined with 5-fluorouracil plus l-leucovorin (FOLFIRI) as first-line therapy were divided into two groups: those with UGT1A1*1/*1 genotype and those with UGT1A1*1/*6 or *1/*28 genotype. Efficacy and toxicity were compared between these groups retrospectively., Results: Forty-two patients (24 *1/*1 and 18 *1/*6 or *1/*28) were evaluated. The response rate was 48% in *1/*1 group and 56% in *1/*6 or *1/*28 group (P = 0.847). Median progression-free survival was 8.6 months in *1/*1 group and 8.5 months in *1/*6 or *1/*28 group (P = 0.888). No hematologic or non-hematologic toxic effects were clearly related to UGT1A1*1/*6 or *1/*28 during the first cycle or throughout the entire course of chemotherapy., Conclusions: There were no significant differences in the efficacy or toxicity of FOLFIRI between patients with UGT1A1*1/*1 genotype and those with UGT1A1*1/*6 or *1/*28 genotype. Our results suggest that patients with the latter genotypes can receive FOLFIRI at the same dose of irinotecan as those with the UGT1A1*1/*1 genotype receive.

Purpose: Most ovarian cancers recur after first-line treatment. We studied the pharmacology, tolerability, and therapeutic potential of intraperitoneal (IP) topotecan, alone and with IP cisplatin., Methods: Patients received IP topotecan 1.5 mg (flat dose) daily on days 1-5 (level 0) via IP catheter. Subsequent cohorts received IP cisplatin 50 mg/m(2) on day 1 added to topotecan 1.5 mg on days 1-3 (level I), topotecan 1.25 mg on days 1-3 (level II), or topotecan 1.25 mg on days 1-5 (level III). Plasma and IP concentrations of total and lactone (E-ring closed) topotecan were measured on days 1 and 2 in cycles 1 and 2., Results: Sixteen patients (15 tubo-ovarian, 1 gastric cancers) were entered at levels 0 (3), I (4), II (4), or III (5). Dose-limiting neutropenias occurred in seven patients at dose levels I and III; grade 3 thrombocytopenia occurred in two at level III. Other toxicities included grade 1 hives in two, serum creatinine elevations in two, and Staphylococcus epidermidis and chemical peritonitis (one each). A median progression-free survival of 13 months was recorded among ovarian cancer patients who had minimal (6) or no residuum (3) after platinum-based induction; 5 are alive at 4 years. Topotecan's AUC IP/AUC plasma ratios ranged from 13 to 119., Conclusion: Topotecan IP for 3-5 days is tolerable; occasionally, myelosuppression is dose-limiting. Topotecan 1.25 mg (days 1-3) with IP cisplatin 50 mg/m(2) (day 1) is a regimen suitable for consolidation in phase 3 trials.

Purpose: Histone deacetylase inhibitors (HDACIs), such as PXD101 and suberoylanilide hydroxamic acid, inhibit proliferation and stimulate apoptosis of tumor cells. The enhanced effectiveness of chemotherapy or radiotherapy when combined with HDACIs has been observed in several cancers. In this study, we investigated the antitumor effect of PXD101 combined with irinotecan in colon cancer., Methods: HCT116 and HT29 colon cancer cells for cell viability assay were treated with PXD101 and/or SN-38, the active form of irinotecan. Antitumor effects of HCT116 and HT29 xenografts treated with these combinations were evaluated. [(18)F]FLT-PET was used to detect early responses to PXD101 and irinotecan in colon cancer., Results: PXD101 and SN38 possessed dose-dependent antiproliferative activity against HCT116 and HT29 cells and exerted a synergistic effect when used in combination. In xenografted mice, PXD101 in combination with irinotecan dramatically inhibited tumor growth without causing additive toxicity. Apoptotic effects on xenograft tumors were greater with combined treatment than with irinotecan alone. [(18)F]FLT-PET imaging revealed a 64% decrease in [(18)F]FLT uptake in tumors of HCT116 xenograft-bearing mice treated with a combination of PXD101 and irinotecan, indicating a decrease in thymidine kinase 1 (TK1) activity. These results were supported by Western blot analyses showing a decrease in tumor thymidine kinase 1 protein levels, suggesting that [(18)F]FLT-PET can be used to non-invasively detect early responses to these agents., Conclusions: These data show that PXD101 increases the cytotoxic activity of irinotecan in in vitro and in vivo colon cancer models and suggest these agent combinations should be explored in the treatment of colon cancer.

The prognosis of patients with CNS involvement of solid tumors is poor. In these patients, systemic chemotherapy has a theoretical advantage of concurrent treatment of systemic disease and reduced risk of neurotoxicity. Here, we report on the efficacy and toxicity of topotecan/ifosfamide (TOPO/IFO) combination chemotherapy in patients treated for CNS involvement of different solid malignancies. Fourteen patients with CNS manifestations (seven with brain metastases, two meningeal carcinomatosis, and five both) of solid tumors (seven with breast cancer, six lung cancer, and one unknown primary cancer) received TOPO/IFO treatment. Eleven patients each were pretreated with 1-6 systemic therapy regimens and whole-brain irradiation. Patients received a total of 34 (median 2) TOPO/IFO cycles. TOPO dosage was 3.6 mg/m(2) (1.2 mg/m(2), days 1-3) and IFO dosage 3,000 mg/m(2) (1,500 mg/m(2), days 1-2) per cycle. Of 12 patients with brain metastases, one patient had partial remission, three stable disease, two progressed, and six had no radiologic CNS response evaluation. Response of meningeal carcinomatosis was found in two and progressive disease in two (three patients not evaluated). Neurologic improvement or stabilization was observed in six of twelve evaluable patients. No systemic tumor response was seen in seven evaluated patients. Grade 3/4 toxicities in eleven evaluable patients were leukopenia (n = 9), infection (n = 6), and thrombopenia (n = 5). Median time to treatment failure was 43 days and median overall survival 107 days. Symptom control was frequently achieved with TOPO/IFO systemic chemotherapy despite a low objective response rate. The feasibility of this treatment is impaired by severe hematotoxicity.

Neuroendocrine small cell carcinoma of the bladder is a rare and aggressive cancer with a very pejorative behavior. Neuroendocrine small cell carcinoma of bladder is a histological entity with special characteristics, rapidly aggressive and metastatic and with a poor prognosis. Because it is rare, there is no consensus to date. Its management should be multidisciplinary, involving surgery, chemotherapy and radiotherapy. We report the case of an 84-year-old patient with neuroendocrine small cell carcinoma of the bladder, treated by neoadjuvant chemotherapy followed by a combined chemoradiotherapy. A review of the literature on this topic is also presented., (Copyright © 2011 Société française de radiothérapie oncologique (SFRO). Published by Elsevier SAS. All rights reserved.)

Objective: The Phase II trial was conducted to evaluate the efficacy and toxicity of belotecan (CKD 602), a topoisomerase I inhibitor, in persistent or recurrent carcinoma of the cervix., Methods: Belotecan was administrated at 0.5 mg/m(2)/day for 5 consecutive days every 3-week cycle in patients with recurrent or progressive cervical carcinoma who were unsuitable candidates for curative treatment with surgery or radiotherapy., Results: At the first stage of trial, a total of 16 patients were entered in the study. A median of three cycles were administrated per patient with a range of one to seven cycles. Fourteen of 16 patients (87.5%) had received radiotherapy or chemotherapy prior to the study. The most frequently severe adverse events were anemia and neutropenia. More than Grade 3 anemia and neutropenia were seen in 10 cycles (23.8%) and 6 cycles (14.3%) of 42 cycles, respectively. The incidence of non-hematologic toxicity was minimal. One patient died of treatment-related toxicities. There was no complete or partial response to belotecan. The median overall survival was 12.38 months (95% confidence interval, 9.71-15.04)., Conclusions: Belotecan was not active in the treatment of recurrent or progressive cervical cancer as a single agent. ClinicalTrials.gov identifier: NCT00430144.

Background: Five-day topotecan is approved by the US Federal Drug Administration (FDA) for sensitive relapsed small-cell lung cancer (SCLC). We previously found that 4 mg/m(2) intravenous (I.V.) weekly dosing resulted in low-grade 3/4 toxicity but an overall response rate (ORR) < 10%. We hypothesized that higher topotecan dosing could improve ORR without significantly increasing toxicity., Patients and Methods: This multicenter phase II trial sought a 25% ORR (α = 0.04; β = 0.20). Eligible patients (sensitive or refractory relapsed SCLC; Eastern Cooperative Oncology Group [ECOG] performance status [PS] 0-1; measurable disease) received weekly topotecan (6 mg/m(2) I.V. for 6 weeks) and were restaged every 8 weeks., Results: Baseline characteristics were N = 38, enrolled 5/2006-10/2007; median age 64 years (range, 35-82), 47% female, 74% ECOG PS 1, 50% refractory relapsed SCLC. The median follow-up was 15 months (range, 12-24 months). No patients received all planned therapy; only 1 patient was able to receive all planned treatment in cycle 1 because of hematologic toxicity and progressive disease (PD). Among all patients, ORR was 8% (95% confidence interval [CI], 2%-21%), 24% had stable disease, and disease in 47% progressed. Among sensitive relapsed patients ORR was 16% (95% CI, 3%-40%) with no complete responses; median response duration was 3.3 months. Five (26%) patients had stable disease; 8 (42%) patients had PD. Among sensitive relapsed patients, the median time to progression (TTP) and overall survival (OS) was 2.5 months and 8.6 months, respectively. Among refractory relapsed patients there were no ORRs, and median TTP and OS were 1.5 months and 3.7 months, respectively. Grade 3/4 toxicities (> 10%) included neutropenia (53%), leukopenia (42%), thrombocytopenia (37%), anemia (13%), fatigue (13%), and pain (13%). There were no treatment-related deaths., Conclusion: Weekly topotecan (6 mg/m(2) I.V.) is not feasible because of hematologic toxicity and does not improve efficacy in patients with relapsed SCLC., (Copyright © 2011. Published by Elsevier Inc.)

Purpose: Genz-644282 [8,9-dimethoxy-5-(2-N-methylaminoethyl)-2,3-methylenedioxy-5H-dibenzo[c,h][1,6]naphthyridin-6-one] has emerged as a promising candidate for antitumor agents. This report describes the bone marrow colony-forming unit, granulocyte macrophage (CFU-GM) and tumor cell CFU activity of topoisomerase I (Top1) inhibitors, such as Genz-644282, topotecan, irinotecan/SN-38, and ARC-111, and examines their activity in several human tumor xenograft models., Experimental Design: Colony-forming assays were conducted with mouse and human bone marrow and eight human tumor cell lines. In addition, 29 human tumor cell lines representing a range of histology and potential resistance mechanisms were assayed for sensitivity to Genz-644282 in a 72-hour exposure assay. The efficacy of Genz-644282 was compared with standard anticancer drugs (i.e., irinotecan, docetaxel, and dacarbazine) in human tumor xenografts of colon cancer, renal cell carcinoma, non-small cell lung cancer, and melanoma., Results: Human bone marrow CFU-GM was more sensitive to the Top1 inhibitors than was mouse bone marrow CFU-GM. The ratio of mouse to human IC(90) values was more than 10 for the camptothecins and less than 10 for Genz-644282, which had more potency as a cytotoxic agent toward human tumor cells in culture than the camptothecins in the colony-forming and 72-hour proliferation assays. Genz-644282 has superior or equal antitumor activity in the human tumor xenografts than the standard drug comparators., Conclusions: On the basis of preclinical activity and safety, Genz-644282 was selected for development and is currently undergoing phase 1 clinical trial., (©2011 AACR.)

Purpose: Camptothecin (CPT), a potent topoisomerase I inhibitor, was originally discovered as an anticancer agent to induce programmed cell death of cancer cells. Recent evidence suggests that, similar to cancer, alterations in apoptosis and over-proliferation of key effector cells in the arthritic joint result in rheumatoid arthritis (RA) pathogenesis. Initial in vitro studies have suggested that camptothecin inhibits synoviocyte proliferation, matrix metalloproteinases expression in chrondrocytes and angiogenesis. This study is one of the first to test, in vivo, RA as a new indication for CPT., Methods: To circumvent insolubility, instability and toxicity of CPT, we used biocompatible, biodegradable and targeted sterically stabilized micelles (SSM) as nanocarriers for CPT (CPT-SSM). We also surface-modified CPT-SSM with vasoactive intestinal peptide (VIP) for active targeting. We then determined whether this nanomedicine abrogated collagen-induced arthritis (CIA) in mice., Results: Based on our findings, this is the first study to report that CPT was found to be efficacious against CIA at concentrations significantly lower than usual anti-cancer dose. Furthermore, a single subcutaneous injection of CPT-SSM-VIP (0.1 mg/kg) administered to CIA mice mitigated joint inflammation for at least 32 days thereafter without systemic toxicity. CPT alone needed at least 10-fold higher dose to achieve the same effect, albeit with some vacuolization in liver histology., Conclusion: We propose that CPT-SSM-VIP is a promising targeted nanomedicine and should be further developed as a safe, long-acting, disease-modifying pharmaceutical product for RA.

Belotecan (Camtobell, CKD602) is a new camptothecin derivative antitumor agent that belongs to the topoisomerase inhibitors. The aim of this phase II study was to evaluate the efficacy and safety of single agent belotecan as a second-line therapy in patients with small cell lung cancer (SCLC). Patients who were previously treated for SCLC were entered into the study. Belotecan was given by daily intravenous infusion for five consecutive days, every three weeks. Twenty-five patients were enrolled in this study. On an intention-to-treat basis, belotecan induced an overall response rate of 24%, a median overall survival of 9.9 months, a median time to progression of 2.2 months, and a 1-year survival rate of 38.3%. Grade 3/4 neutropenia developed in 88.0% of patients and grade 3/4 thrombocytopenia in 40.0%. Nonhematologic toxicity of grade 3 or 4 was low. The results suggest that belotecan is relatively active and well tolerated as a second-line agent in patients with SCLC., (Copyright © 2010 Elsevier Ireland Ltd. All rights reserved.)

What Is Known and Objective: Pharmacogenetic studies, to help us understand variability in human drug response, have hitherto focussed largely on our own germline mutations, and in the context of anticancer and antimicrobial drugs, also on mutations of the tumour cell or invader microorganism. Here, we wish to draw attention to how our microbiome may contribute to variability in drug effects., Comment: Irinotecan, a prodrug which is activated to the topoisomerase I inhibitory metabolite (SN-38), is commonly used for the treatment of a range of cancers. SN-38 is subsequently detoxified by uridine diphosphate-glycosyltransferase 1, encoded by the UGT1A1 gene. It is well known that the variant allele UGT1A*18 is associated with the more common adverse effects of irinotecan. A recent study shows that the potentially dose-limiting irinotecan-induced diarrhoea is due to enterohepatic circulation of SN-38, and its reactivation in the gut by bacterial β-glucuronidases. Importantly, the authors used specific inhibitors of the microbial enzymes to reduce the gastro-intestinal toxicity in mice., What Is New and Conclusion: We draw attention to the increasing range of diseases, including diabetes and obesity, associated with our microbiome. This pharmacogenetic example reminds us that in personalized medicine, there is more than our own genome to take account of., (© 2011 Blackwell Publishing Ltd.)

Objective: To evaluate the efficacy and safety of topotecan in patients with recurrent ovarian, primary peritoneal, and fallopian tube carcinomas., Methods: A randomized phase II analysis of platinum-sensitive patients with measurable disease was performed independently assessing intravenous topotecan 1.25 mg/m2 daily×5 every 21 days (regimen I) and topotecan 4.0 mg/m2/day on days 1, 8, and 15 of a 28-day cycle (regimen II). All patients were treated until disease progression, unmanageable toxicity, or patient refusal. Insufficient accrual related to regimen I resulted in a redesign of the study as a single arm phase II trial assessing only regimen II. More complete efficacy data is presented for regimen II as enrollment on regimen I was insufficient for some analyses., Results: A total of 81 patients were enrolled. One patient was ineligible. Fifteen patients received regimen I, while 65 patients were treated with regimen II. The response rate on regimen I (daily×5) was 27% (90% CI: 10-51%) and 12% (90% CI: 6-21%) on regimen II (weekly). The median PFS and OS were 4.8 and 27.8 months, respectively, for regimen II. Grade 3/4 neutropenia rate was 93% with daily×5 dosing and 28% for weekly treatment. Febrile neutropenia was very low in both groups., Conclusion: The weekly regimen of topotecan appeared less active but resulted in less toxicity than the daily regimen in platinum-sensitive recurrent ovarian cancer patients., (Copyright © 2010. Published by Elsevier Inc.)

Objective: This Phase II study was carried out to investigate the efficacy, safety and pharmacokinetics of topotecan in Japanese patients with relapsed ovarian carcinoma., Methods: Patients with relapsed ovarian carcinoma after having received one regimen containing platinum-based chemotherapy were eligible for this study. Topotecan was administered at 1.2 mg/m(2)/day for five consecutive days, repeated every 3 weeks., Results: Seventy-two patients were enrolled in the study. The response rate was 28.2% (95% confidence interval, 18.1-40.1%). Signs of myelosuppression, such as neutropenia (Grade 3, 12.5%; Grade 4, 83.3%), thrombocytopenia (Grade 3, 36.2%; Grade 4, 4.2%) and decreased hemoglobin (Grade 3, 36.1%; Grade 4, 11.1%), were the most common hematological toxicities. Grade 3 febrile neutropenia occurred in 5 (6.9%) patients. There was little intraindividual or interindividual variability in the pharmacokinetics of topotecan., Conclusions: Topotecan at 1.2 mg/m(2)/day is an effective and tolerable therapeutic option for Japanese patients with relapsed ovarian carcinoma.

Purpose: This phase II study evaluated the safety and efficacy of single-agent amrubicin versus topotecan in patients with small-cell lung cancer (SCLC) sensitive to first-line platinum-based chemotherapy., Patients and Methods: Patients were randomly assigned 2:1 to amrubicin (40 mg/m(2)/d in a 5-minute intravenous [IV] infusion, days 1 through 3, every 21 days) or topotecan (1.5 mg/m(2)/d in a 30-minute IV infusion, days 1 through 5, every 21 days). The primary efficacy end point was overall response rate (ORR) for amrubicin. Secondary end points included time to progression, median progression-free survival (PFS), and median overall survival (OS)., Results: Of 76 patients enrolled, 50 patients were randomly assigned to amrubicin, and 26 patients were randomly assigned to topotecan. Amrubicin treatment resulted in a significantly higher ORR than topotecan (44% v 15%; P = .021). Median PFS and median OS were 4.5 months and 9.2 months with amrubicin and 3.3 months and 7.6 months with topotecan, respectively. Tolerability was similar with both agents. However, grade 3 or worse neutropenia and thrombocytopenia seemed to be more frequent in the topotecan group as compared with the amrubicin group (78% and 61% v 61% and 39%, respectively)., Conclusion: Amrubicin shows promising activity, with an ORR of 44% compared with an ORR of 15% for topotecan as second-line treatment in patients with SCLC sensitive to first-line platinum-based chemotherapy. In addition, the safety profiles were comparable; however, a trend was noted for more frequent grade 3 or worse neutropenia and thrombocytopenia in the topotecan group as compared with the amrubicin group. Additional studies are ongoing.

Charge is an important characteristic of drug molecules, since ionization sites determine the pKa at a particular pH. The pKa in turn can affect many parameters, including solubility, dissolution rate, reaction kinetics, formulation, cell permeability, tissue distribution, renal elimination, metabolism, protein binding and receptor interactions. The impact of charge dynamics is amplified in human solid tumors that exhibit the glycolytic phenotype and associated acidic extracellular microenvironment. This phenotype is driven by hypoxia and creates a pH gradient in tumors that favors uptake of weak acids and exclusion of weak bases. Established anticancer drugs exhibit a range of pKa's and thus variable ability to exploit the tumor pH gradient. The camptothecins are a prime example as they represent a diverse class of approved anticancer drugs and drug candidates whose charge distribution varies with pH. An in silico method was used to predict charge distribution of camptothecins at physiological versus acidic pH in both the lactone and carboxylate forms. A significant amount of uncharged carboxylate was predicted at acidic pH that could enter tumor cells and accumulate in mitochondria to inhibit mitochondrial topoisomerase I. A model is presented to describe the charge dynamics of a new camptothecin analog and the impact on nuclear and mitochondrial mechanism(s) of action. This example illustrates the importance of integrating tumor physiology and charge dynamics into anticancer drug development.

Background: The prognosis for recurrent or refractory brain tumors in children is poor with conventional therapies. Topotecan is a topoisomerase I inhibitor with good central nervous system (CNS) penetration following oral administration. Increased efficacy of topotecan has been demonstrated with prolonged low-dose daily treatment in pre-clinical models. To investigate further this drug delivered orally in pediatric CNS malignancies, a phase II study in children with recurrent or refractory brain tumors was performed., Procedure: Patients ≤ 21 years of age at diagnosis with a recurrent, progressive, or refractory primary CNS malignancy and measurable disease, were eligible. Patients enrolled into four strata: ependymoma (N = 4), high-grade glioma (HGG) (N = 6), brainstem glioma (BSG) (N = 13), and primitive neuroectodermal tumor (PNET) (N = 8). Oral topotecan was administered once daily at a dose of 0.8 mg/m(2)/day for 21 consecutive days repeated every 28 days. Response and toxicity profiles were evaluated., Results: Twenty-six patients were evaluable (median age 9.2 years; 10 males). Two objective responses were observed in PNET patients with disseminated tumor at study entry. These two patients remain alive and in remission 7 and 9.5 years off study. Four other patients (two BSG, one PNET, and one HGG) had stable disease (median 4.6 months). The most common toxicities were hematologic., Conclusions: Daily oral topotecan at a dose of 0.8 mg/m(2)/day can be safely administered to children with recurrent or refractory brain tumors. This regimen identified activity in recurrent PNET. The prolonged progression free survival (PFS) in two PNET patients justifies consideration of this regimen in more advanced clinical trials.

Background: The objective of this study was to evaluate feasibility, safety and clinical outcome of long-term therapy with topotecan (Hycamtin) in recurrent or persistent ovarian cancer., Patients and Methods: A retrospective chart review was conducted on all patients treated with topotecan (TPT) at the Department of Obstetrics and Gynecology, University of Bari, Italy between 1999 and 2007. Pertinent clinicopathologic information, response and toxicity following treatment with TPT were collected. TPT was given at a dosage ranging between 1.5 and 1.0 mg/m2 every three to four weeks. All patients were evaluated for toxicity acording to the CTC and response according to the RECIST response criteria. Time to progression (TTP) was calculated from initiation of TPT treatment and start of the next chemotherapy regimen., Results: A total of 30 patients received TPT for at least eight cycles for recurrent ovarian (22), fallopian tube (3) or primary peritoneal carcinoma (5). A total of 432 cycles of chemotherapy were given, with an average of 14.4 cycles per patient (range 8-22). Dose reduction was necessary in 20 patients (66%). About half of the patients required blood transfusions and growth factors. Non hematologic toxicity was mild and manageable. Responses were observed in 16/30 patients (53%), the remaining having SD. Median time to treatment progression was 28 months (range 9-88)., Conclusion: Long-term treatment with topotecan in recurrent/persistent ovarian cancer is feasible with limited evidence of cumulative toxicity. The results of this retrospective analysis suggest a potential role for late response and survival benefit for those patients without disease progression who continue topotecan therapy beyond six cycles of treatment.

Camptothecin is a selective inhibitor of DNA topoisomerase I, and has effective antitumor activity. Recently, camptothecin has been shown to activate the transcription of low-abundance antisense RNAs at the HIF-1α gene locus in human cancer cells in a Topoisomerase I-dependent manner. The activation of antisense transcription is likely due to sustained drug interference with transcription regulation mechanisms leading to a more open chromatin conformation and de-repression/activation of antisense transcription. Camptothecin readily inhibits Topoisomerase I in cells, and the enzyme inhibition activates transcriptional Cdk (Cdk9 and/or Cdk7) activity leading to the hyperphosphorylation of the CTD of the largest subunit of RNA polymerase II (RNAP II). This results in an alteration of RNAP II regulation with specific effects at transcription levels. Thus, the findings have documented that camptothecin can interfere with specific transcription regulatory steps, impairing the balance of cellular antisense and sense transcripts at the HIF-1α gene locus. That may have a considerable impact on cancer therapy development particularly for non-responsive human tumors., (Copyright © 2010 Elsevier B.V. All rights reserved.)

High grade primary CNS gliomas hold some of the worst prognoses of any malignancy, with the vast majority of patients dying within two years of diagnosis, even with aggressive modern treatments. Surgical resection and radiotherapy are cornerstones of treatment when possible. In spite of many years of research, only recently has management with chemotherapy been able to prolong survival in patients with high grade gliomas, albeit only modestly at best. Topoisomerase I (TOP1) inhibitors target an enzyme critical for DNA replication and cell-cycle progression; they cross the blood-brain barrier and have antitumor activity against glioblastoma cells in vitro. The most frequently associated toxicities are neutropenia and diarrhea, but are often manageable. The two most used agents are irinotecan and topotecan. Due to enhanced cytochrome CY3A4/5 enzyme activity, irinotecan dose must be adjusted with concomitant enzyme-inducing antiepileptic drug usage; the data is less clear regarding the effects on topotecan. Clinical trials in patients with recurrent malignant glioma have evaluated TOP1 inhibitors as monotherapy and in combination with other agents. There is evidence for using topotecan with radiotherapy. Irinotecan has limited efficacy as monotherapy, but shows promise in combination with other agents, particularly temozolomide and bevacizumab. Newer generation TOP1 inhibitors are currently being evaluated in phase I trials. TOP1 inhibitors show promising activity in patients with primary CNS malignancies and warrant further study.

Topotecan was loaded into large unilamellar vesicles using nigericin-generated pH gradient or with triethylammonium (TA) ion gradient. Despite that in both loading methods, the encapsulated counter ion was 5-sulfosalicylate (5ssa), the resultant formulations exhibited distinct properties. In NaCl-containing release buffer, vesicles prepared with nigericin/Na(+) system could release topotecan at a faster rate than 5ssa-TA vesicles, whereas in the absence of Na(+), there was no difference in the drug release kinetics. In plasma, both formulations could prolong the circulation halftime of topotecan, but 5ssa-TA vesicles were more able to stabilize the encapsulated topotecan, as evidenced by the increased t(1/2) and decreased conversion of lactone to carboxylate form. However, the improved drug retention did not mean the elevated safety and efficacy. In L1210 ascitic tumor model, the administration of 5ssa-TA vesicles at 10mg/kg induced the early death of ∼60% mice at 6-7 days. In contrast, the treatment with nigericin/Na(+) vesicles at the same dose level resulted in a mean survival time of ∼18.0 days, ∼1.38-fold of that of free topotecan. In addition, the formulation was safer than free topotecan. The results indicated that nigericin could be used as release regulator to optimize drug release kinetics, resulting in safe and efficacious liposome-based topotecan formulation. The results were promising since no liposome topotecan formulations with reduced toxicity were reported., (Copyright © 2010 Elsevier B.V. All rights reserved.)

Despite a decreasing incidence in the United States, small-cell lung cancer (SCLC) remains a major clinical problem, with approximately 30,000 new cases each year. The diagnosis of SCLC is usually not difficult. The Veterans Administration Lung Study Group (VALSG) staging system is less accurate than the American Joint Committee of Cancer tumor-node-metastasis (TNM) system (7th edition) at predicting survival in SCLC, especially in lower stage disease. Surgery has not played a major part in the management of SCLC, but emerging data suggest that resection may have a role in earlier stage disease. While the frontline treatment of SCLC has not changed significantly in the past decade, newer agents that are currently being investigated provide hope for better treatment of relapsed/refractory disease for the future.

Background: Belotecan is a topoisomerase I inhibitor. This phase II trial was conducted to evaluate the efficacy and toxicity of belotecan in relapsing small-cell lung cancer (SCLC) patients after irinotecan failure., Patients and Methods: SCLC patients, who had relapsed at least 3 months after achieving objective response to irinotecan plus platinum chemotherapy, were eligible. Belotecan was administered at a dose of 0.5 mg/m(2)/day for 5 consecutive days every 3 weeks., Results: Twenty-seven patients were enrolled in this study. Twenty-five patients were evaluated for response, and 27 patients were evaluated for toxicity and survival. The overall response rate was 22%. The median time to progression was 4.7 months (95% CI, 3.6-5.8 months), and the median overall survival was 13.1 months (95% CI, 10.4-15.8 months). The most frequent grade 3/4 toxicities were neutropenia (93%) and thrombocytopenia (48%). There was one treatment-related death due to pneumonia., Conclusion: Belotecan showed modest activity and manageable toxicities in relapsing SCLC patients in this study which was conducted in Asia. But further study in Caucasian patients is needed., (Copyright 2010 Elsevier Ireland Ltd. All rights reserved.)

Purpose: Treatment of neuroblastoma is successful in less than half of patients with high-risk disease. The antitumor activity of a water soluble pegylated SN38 drug conjugate, EZN-2208, was compared with CPT-11 (a prodrug for SN38) in preclinical models of human neuroblastoma., Experimental Design: The in vitro cytotoxicity of EZN-2208 was tested by counting trypan blue dye- and Annexin V-positive cells, whereas its therapeutic efficacy was evaluated, in terms of survival, and antitumor and antiangiogenic activities, in s.c. luciferase-transfected, pseudometastatic, and orthotopic neuroblastoma animal models., Results: EZN-2208 was about 100-fold more potent than CPT-11 in vitro, by inducing apoptosis/necrosis and p53 expression and by reducing hypoxia-inducible factor (HIF)-1α/HIF-2α expression. EZN-2208 gave superior antitumor effects compared with CPT-11 in neuroblastoma xenografts. EZN-2208 treatment always resulted in lack of tumor detection at the end of trials whereas only small therapeutic effects were observed with CPT-11, as assessed by luciferase assay or tumor size, or even by staining histologic sections of tumors with antibodies recognizing neuroblastoma cells and cell proliferation. In a neuroblastoma model resistant to doxorubicin, cisplatin, vincristine, fenretinide, and topotecan, EZN-2208 induced 100% curability. It also blocked tumor relapse after topotecan-vincristine-doxorubicin combined treatment. Mechanistic experiments showed statistically significantly enhanced terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling and Histone H2ax staining as well as decreased vascular endothelial growth factor, CD31, matrix metalloproteinase (MMP)-2, and MMP-9 expression in tumors removed from EZN-2208-treated mice and radiating vessels invading the tumor implanted onto the chorioallantoic membranes., Conclusions: EZN-2208 should be considered a most promising novel antineuroblastoma agent. An ongoing phase I study in pediatric patients should identify the optimal dose for a phase II study., (©2010 AACR.)

There is an opportunity to improve the therapeutic potential of a combination of two drugs using nanoliposomes. The combination of topotecan (TPT) and vincristine (VCR) was selected. The ratio-dependent synergy between these two drugs was evaluated, in an attempt to improve the therapeutic efficacy of this combination in vivo. The interaction between the drugs was evaluated in tissue culture by the median-effect analysis. Certain ratios of combined drugs were synergistic, whereas, others were antagonistic, implying that the most efficacious combinations should be at a specific fixed drug ratio. For in vivo evaluation, nanoliposomes co-remotely loaded simultaneously with both drugs by transmembrane ammonium sulfate gradient were developed. VCR and TPT were successfully co-encapsulated at therapeutically relevant levels in the same nanoliposome (LipoViTo). The nanoliposomes controlled the drugs' "biofate" and maintained a fixed drug ratio in vivo, allowing one to compare the therapeutic efficacy of various predefined drug ratios. Pharmacokinetics and biodistribution studies showed that LipoViTo delivers the two drugs simultaneously to the tumors, where they are released at a predefined ratio. LipoViTo was more efficacious than the free drugs and liposomes with one agent, singly or in combination, in two tumor models in mice. LipoViTo co-loaded with both drugs corresponding to their maximal tolerated dose (MTD) ratio resulted in the best therapeutic efficacy. To summarize: liposomal co-encapsulation of anticancer drug combinations can profoundly influence therapeutic outcomes. Drug combinations can be optimized preclinically through pharmacokinetic control by remote loading into nanoliposomes., (2010. Published by Elsevier B.V.)

Because camptothecins are effective against previously resistant tumors and are the only class of topoisomerase I (Top1) inhibitors approved for cancer treatment, we developed the indenoisoquinolines. Like camptothecins, the indenoisoquinolines selectively trap Top1-DNA cleavage complexes and have been cocrystallized with the Top1-DNA cleavage complexes. Indenoisoquinolines show antitumor activity in animal models. They have several advantages over the camptothecins: (a) They are synthetic and chemically stable. (b) The Top1 cleavage sites trapped by the indenoisoquinolines have different genomic locations, implying differential targeting of cancer cell genomes. (c) The Top1 cleavage complexes trapped by indenoisoquinolines are more stable, indicative of prolonged drug action. (d) They are seldom or not used as substrates for the multidrug resistance efflux pumps (ABCG2 and MDR-1). Among the >400 indenoisoquinolines synthesized and evaluated, three have been retained as leads for clinical development by the National Cancer Institute: NSC 706744, NSC 725776 (Indimitecan), and NSC 724998 (Indotecan). The trapping of Top1 cleavage complexes by indenoisoquinolines in cells results in the rapid and sustained phosphorylation of histone H2AX (γ-H2AX). We discuss the use of γ-H2AX as a pharmacodynamic biomarker for the clinical development of the indenoisoquinolines.