Preclinical and phase I trials of topoisomerase I inhibitors

The Novel Dual Topoisomerase Inhibitor P8-D6 Shows Anti-myeloma Activity In Vitro and In Vivo

P8-D6 is a novel dual inhibitor of human topoisomerase I (TOP1) and II (TOP2) with broad pro-apoptotic antitumor activity. NCI-60 screening revealed markedly improved cytotoxicity of P8-D6 against solid and leukemia cell lines compared with other single and dual topoisomerase inhibitors, for example, irinotecan, doxorubicin, or pyrazoloacridine. In this study, we investigated the capacity of P8-D6 to inhibit myeloma cell growth in vitro and in vivo Growth inhibition assays demonstrated significant anti-myeloma effects against different myeloma cell lines with IC₅₀ values in the low nanomolar range. Freshly isolated plasma cells of patients with multiple myeloma were killed by P8-D6 with similar doses. P8-D6 activated caspase 3/7 and induced significant apoptosis of myeloma cells. Supportive effects of bone marrow stromal cells on IL6-dependent INA-6 myeloma cells were abrogated by P8-D6 and apoptosis occurred in a time- and dose-dependent manner. Of note, healthy donor peripheral blood mononuclear cells and human umbilical vein endothelial cells were not affected at concentrations toxic for malignant plasma cells. Treatment of myeloma xenografts in immunodeficient SCID/beige mice by intravenous and, notably, also oral application of P8-D6 markedly inhibited tumor growths, and significantly prolonged survival of tumor-bearing mice.

Review : Topoisomerase I inhibitors: 2. Irinotecan

Purpose. The primary objective of this article is to discuss the pharmacology, pharmacokinetics, clinical use, and adverse effects of the approved topoisomer ase I inhibitors. This is the second in a series of two articles and will focus on irinotecan.

Data Sources. We reviewed the literature through a MEDLINE search of English language arti cles from 1985 through 1998. Relevant articles cited in the titles obtained from the MEDLINE search were also used. The following terms were used for purpose of conducting the MEDLINE search: topoisomerase inhibitors, irinotecan, topoisomerase I, camptosar, and CPT-11.

Data Extraction. We have reviewed the current literature to discuss the pharmacology, pharmacokinet ics, clinical use, toxicity, drug interactions, indications, formulation, dosage and administration, and pharmaceu tical issues surrounding the use of irinotecan.

Data Synthesis. The topoisomerase I inhibitors are new antineoplastic agents with a unique mechanism of action. Promising areas of application include colo rectal cancer, non-small-cell lung cancer, small-cell lung cancer, cervical cancer, and lymphomas. Clinical trials detailing the activity of topoisomerase I inhibitors in these areas are presented.

Review : Topoisomerase I inhibitors: 1. Topotecan

Purpose. The primary objective of this article is to discuss the pharmacology, pharmacokinetics, clin ical use, and adverse effects of the approved topoisomerase I inhibitors. This is the first in a series of two articles and will focus on topotecan.

Data Sources. We reviewed the literature through a MEDLINE search of English language articles from 1985 through 1997. Relevant articles cited in the titles obtained from the MEDLINE search were also used. The following terms were used for purpose of conducting the MEDLINE search: topoisomerase inhibitors, topotecan, topo isomerase I, Hycamtin, SKF 104864.

Data Extraction. We reviewed the current literature in order to discuss the pharmacology, pharmacokinetics, clinical use, toxicity, drug inter actions, indications, formulation, dosage and ad ministration, and pharmaceutical issues surround ing the use of topotecan.

Data Synthesis. The topoisomerase I inhibi tors are new antineoplastic agents with a unique mechanism of action. Promising areas of applica tion include ovarian cancer, lung cancer, radiation sensitization, and refractory leukemias. Clinical tri als detailing its activity in these areas are pre sented.

Interaction of carbamazepine with herbs, dietary supplements, and food: a systematic review

Background. Carbamazepine (CBZ) is a first-line antiepileptic drug which may be prone to drug interactions. Systematic review of herb- and food-drug interactions on CBZ is warranted to provide guidance for medical professionals when prescribing CBZ. Method. A systematic review was conducted on six English databases and four Chinese databases. Results. 196 out of 3179 articles fulfilled inclusion criteria, of which 74 articles were reviewed and 33 herbal products/dietary supplement/food interacting with CBZ were identified. No fatal or severe interactions were documented. The majority of the interactions were pharmacokinetic-based (80%). Traditional Chinese medicine accounted for most of the interactions (n = 17), followed by food (n = 10), dietary supplements (n = 3), and other herbs/botanicals (n = 3). Coadministration of 11 and 12 of the studied herbal products/dietary supplement/food significantly decreased or increased the plasma concentrations of CBZ. Regarding pharmacodynamic interaction, Xiao-yao-san, melatonin, and alcohol increased the side effects of CBZ while caffeine lowered the antiepileptic efficacy of CBZ. Conclusion. This review provides a comprehensive summary of the documented interactions between CBZ and herbal products/food/dietary supplements which assists healthcare professionals to identify potential herb-drug and food-drug interactions, thereby preventing potential adverse events and improving patients' therapeutic outcomes when prescribing CBZ.

Topotecan and carboplatin in patients with platinum-sensitive recurrent ovarian cancer. Results of a multicenter NOGGO: phase I/II study

OBJECTIVE

Second-line treatment with paclitaxel and carboplatin enhances survival of women with platinum-sensitive recurrent ovarian cancer (ROC). However, because of its cumulative neurotoxicity, there is a strong demand for platinum-combinations with better therapeutic index. Because of its pharmacological properties, topotecan is a good adjunct to carboplatin in this setting, but its safety and efficacy remains to be defined.

METHODS

Patients with platinum-sensitive ROC were eligible in this multicenter phase I/II study, stratified according to treatment-free interval (TFI). Dose level 0 consisted of topotecan 1 mg/m(2)/d1-3/q21d plus carboplatin AUC5/d3/q21d. DLT was defined as grade > or =3 neutropenia or thrombocytopenia or grade > or =3 non-hematological toxicity excluding alopecia, nausea and vomiting, accompanied by a treatment delay >1 week.

RESULTS

From June 2004 to August 2005, 26 patients were enrolled, receiving a total of 145 cycles of chemotherapy. MTD was reached at topotecan 0.75 mg/m(2) and carboplatin AUC5. We observed a single grade 4 leucopenia. There were 3 (12%), 15 (58%) and 8 (31%) events of grade 3/4 hematological anaemia, leucopenia, and thrombocytopenia. Response rate was 67% (95% CI 43-85), median progression-free survival 9.5 months (95% CI 7.3-12.0), median overall survival 19.4 months (95% CI 12.3-26.9). None of the toxicity or efficacy endpoints were associated with TFI.

CONCLUSION

Topotecan and carboplatin is a well tolerated novel doublet option for women with platinum sensitive ROC. We encourage further studies on this approach, but to limit the doses of topotecan to 0.75 mg/m(2)/d1-3 and carboplatin AUC 5/d3.

Phase II Trial of Gemcitabine Plus Irinotecan In Patients With Esophageal Cancer

OBJECTIVES

Metastatic esophageal carcinoma is an incurable disease with median survival duration of 6 to 8 months. Based on preclinical data suggesting a dose-dependent synergy between gemcitabine and irinotecan we have conducted a phase II trial in patients with advanced or metastatic esophageal carcinoma.

METHODS

Patient eligibility included a diagnosis of squamous cell or adenocarcinoma of the esophagus/gastroesophageal (GE) junction, metastatic or recurrent disease, no CNS metastasis, no prior chemotherapy, prior adjuvant/neoadjuvant chemotherapy was allowed, no prior gemcitabine or irinotecan, performance status of 0 to 2 and adequate organ function. Patients received gemcitabine 1000 mg/m2 and irinotecan 100 mg/m2 given day 1 and day 8, every 3 weeks. The primary end point was the 6-month survival rate. The secondary end point was to assess qualitative and quantitative toxicities.

RESULTS

Fifty-seven eligible patients were accrued. There were 4 treatment-related deaths. The primary grade 3 to 4 toxic events were diarrhea, dehydration, neutropenia, thrombocytopenia, anemia, and anorexia; and 4 episodes of grade 3 to 5 febrile neutropenia, 1 fatal. The study was designed to detect a difference between the null hypothesis of 30% 6-month survival and the alternative hypothesis of 50% 6-month survival. The Kaplan-Meier estimate of 6-month survival is 56% (95% CI: 43-69%), with a median of 6.3 months. The median time to progression was 3.7 months. The 6-month progression-free survival estimate is 25% (95% CI: 13-36%).

CONCLUSIONS

The length of survival suggests that this combination has benefit similar to platinum containing regimens, however, the toxicity is substantial and is unlikely to prove superior to platinum containing regimens.

In silico search of putative adverse drug reaction related proteins as a potential tool for facilitating drug adverse effect prediction

Adverse drug reaction (ADR) is a significant issue in drug development and post-market applications. Different experimental and computational approaches need to be explored for predicting ADRs due to the complexity of their molecular mechanisms. One approach for predicting ADRs of a drug is to search for its interaction with ADR-related proteins (ADRRPs). In this work, this approach is tested on 11 marketed anti-HIV drugs covering protease inhibitors (PIs), nucleoside reverse transcriptase inhibitors (NRTIs), and non-nucleoside reverse transcriptase inhibitors (NNRTIs). An in silico drug target search method, INVDOCK, is used for searching the ADRRPs of each of these drugs. The corresponding ADRs of the predicted ADRRPs of each of these drugs are compared to clinically observed ADRs reported in the literature. It is found that 86-89% of the INVDOCK predicted ADRs of these drugs are consistent with the literature reported ADRs, and about 67-100% of the literature-reported ADRs of these drugs to various degrees is agreed with INVDOCK predictions. These results suggest that it is feasible to explore in silico ADRRP search methods for facilitating drug toxicity prediction.

Combined topoisomerase I inhibition for the treatment of metastatic colon cancer

The objective of this study was to define the maximally tolerated dose (MTD) and response rate of a combination of two topoisomerase I inhibitors, topotecan and irinotecan, in patients with metastatic colon cancer. Eleven patients, the majority with previously progressive disease on 5-fluorouracil-based regimens, were enrolled onto a phase I/II dose escalation trial utilizing continuous infusion topotecan for 2 weeks and weekly irinotecan x 3 with cycles repeated every 28 days. Dosages of topotecan utilized included 0.2 and 0.25mg/m2/day. Irinotecan was administered at a dose of 62 mg/m2 by i.v. bolus. Patients were followed for toxicity and response. The MTD of the combination of agents was found to be 0.25mg/m2/day for topotecan and 62 mg/m2 for irinotecan. The most common serious toxicities were diarrhea and nausea/vomiting. Only one patient experienced grade III neutropenia. There were no complete or partial responses. However, four patients had prolonged disease stabilization (SD) of up to 324 days and this group remained on protocol therapy for an average of 227 days (p=0.0005 versus patients not achieving SD). We concluded that the MTD for this combination of topoisomerase I inhibitors, given on this particular schedule, has been defined. This combination cannot be recommended as a first- or second-line therapy for patients with metastatic colon cancer based on the responses observed. However, approximately one-third of patients achieved prolonged disease stabilization. Topotecan with irinotecan may be useful as a palliative regimen for a subgroup of colon cancer patients.

Combination chemotherapy with topotecan for non-small cell lung cancer

Patients with non-small cell lung cancer (NSCLC) typically receive platinum-based combination chemotherapy. In spite of improvements in symptoms and survival, response rates remain low and newer agents are being investigated. The newer agents may offer increased efficacy and reduced toxicity compared with established agents and regimens. The topoisomerase-I inhibitor, topotecan, achieves single-agent response rates of 4-25% in NSCLC. Topotecan has also been studied in combinations: a combination of topotecan, administered using the standard 5-day schedule, with cisplatin was effective but was associated with myelosuppression. The combination of topotecan plus carboplatin may be better tolerated and warrants further investigation. Topotecan was also combined with newer agents (gemcitabine, vinorelbine, docetaxel, paclitaxel) using a range of different administration schedules of topotecan. Response rates of up to 30% were achieved. A weekly schedule of topotecan was effective and well tolerated and was also convenient for healthcare professionals and patients.

A new therapeutical approach: topotecan plus gemcitabine in the treatment of patients with relapsed ovarian cancer after failure of first-line chemotherapy with paclitaxel and platinum

AIM

Topotecan and gemcitabine have demonstrated mono-activity against recurrent ovarian cancer. Both drugs affect DNA replication; in addition, topotecan inhibits DNA repair. Based on the efficacy profiles and different mechanisms of action, a phase-I study was conducted to determine the maximum tolerated dose (MTD) of topotecan (day 1-5) and the dose-limiting toxicities (DLT) in combination with gemcitabine (day 1 + 8) every 21 days.

METHODS

Three to six patients were treated per dose-level. Patients with ovarian cancer who had failed a platinum and paclitaxel-containing therapy were enrolled. No individual dose escalation or use of cytokines were allowed.

RESULTS

Twenty-three patients were recruited. Fifty percent of all patients were pretreated with at least two platinum-containing therapies. Eighty courses were assessable for toxicity. The MTD was reached at a dosage of 0.75 mg/m2 topotecan in combination with 800/600 mg/m2 gemcitabine. Thrombocytopenia and leucopenia were the major DLTs. The dose for phase-II trials is 0.50 mg/m2 topotecan given with 800/600 mg/m2 gemcitabine. In this dose-level only one related non-haematological adverse event > grade 2 was observed (grade 3 mycotic stomatitis) and one grade 4 thrombocytopenia occurred. Responses were observed in six patients and stable disease in four out of 12 assessable patients. Median survival time was 15.3 (95% CI: 13.21-28.64) months.

CONCLUSION

The results demonstrate feasibility and the tolerability of topotecan in combination with gemcitabine in recurrent ovarian cancer patients. Based on these results a phase-II study was conducted to evaluate the efficacy of this new combination.

A phase II study of topotecan plus gemcitabine in the treatment of patients with relapsed ovarian cancer after failure of first-line chemotherapy

BACKGROUND

Second-line chemotherapy for patients with ovarian cancer who failed platinum and paclitaxel treatment remains a therapeutic challenge. We investigated the toxicity profile and therapeutic efficacy of a novel combination regimen, topotecan plus gemcitabine, in a clinical phase II study.

PATIENTS AND METHODS

Women with relapsed epithelial ovarian cancer after platinum and paclitaxel treatment were eligible to participate in this trial. Topotecan was given at an initial dose of 0.5 mg/m(2) daily (days 1-5), combined with gemcitabine 800 mg/m(2) and 600 mg/m(2) on days 1 and 8, respectively. Precluding good tolerability, this protocol facilitated subsequent dose increases of topotecan up to 1.0 mg/m(2). The primary objective was to determine the dose-limiting toxicity, whereas secondary objectives comprised measurable and CA-125 response rates, disease-free and overall survival.

RESULTS

The twenty-one patients (median age 57 years, range 37-70 years) who were allocated to this trial received a total of 94 courses of chemotherapy. Median follow-up was 20.5 months. Topotecan dosage could be escalated to 0.75 mg/m(2) in nine patients and 1 mg/m(2) in another two patients. Dose reduction was not necessary in any case. There were no episodes of neutropenic fever, sepsis or chemotherapy-related fatalities. Only one patient developed CTC grade 4 leukopenia after the first treatment cycle, whereas three patients showed grade 3/4 anaemia. Five patients experienced thrombocytopenia grade 4 without clinical sequelae. Non-hematological toxicities were mild and rare. Eleven patients could be evaluated for clinical tumour response, with three complete, and four partial remissions. Two patients each had stable and progressive diseases. The median progression-free survival rate was 8.8 months [95% confidence interval (CI) 6.3-13.4 months]. The median overall survival rate was 21.1 months (95% CI 14.8-22.1 months).

CONCLUSIONS

Topotecan combined with gemcitabine has a favourable toxicity profile and encouraging efficacy in patients with recurrent ovarian cancer.

Treatment of squamous cell esophageal cancer with topotecan: an Eastern Cooperative Oncology Group Study (E2293)

Seventeen patients with enhanced measurable squamous cell carcinoma of the esophagus were treated with topotecan 1.5 mg/m2 daily for 5 days repeated every 21 days. Toxicity was severe, with 1 death from myelotoxicity and 10 patients with life-threatening myelotoxicity. Severe gastrointestinal toxicity consisting of vomiting was also seen in three patients. No response was seen in any of the patients in the study. Topotecan given in this manner has no activity in squamous cell carcinoma of the esophagus.

Schedule-dependent cytotoxicity of SN-38 in p53 wild-type and mutant colon adenocarcinoma cell lines

In this study the effects of SN-38 on colon adenocarcinoma cell lines expressing wild-type p53 (LS174T) or mutant non-functional p53 (HT29) have been investigated. On exposure to SN-38, HT29 cells rapidly progressed through G1 and S and arrested in G2/M. Release and concomitant increase in apoptosis after 48 h was concentration- and time-dependent (P < 0.001), being more rapid at higher concentrations, but reaching plateau at 10 ng ml(-1) with prolonged exposure. LS174T cells showed only a small increase in apoptosis, and only at high concentrations (50-100 ng ml(-1)). The main effect of SN-38 in LS174T cells was prolonged cell cycle arrest, which was independent of concentration. Arrest occurred in all phases of the cell cycle, with the distribution depending on concentration (P < 0.001) and not duration (P > 0.05). With increasing concentration, LS174T cells arrested in G2/M, S and G1. Cell cycle arrest was coincident with increased p53 expression in each phase of the cell cycle. Expression in G1 increased with time and concentration (P < 0.001, P = 0.01 respectively)whereas in S and G2/M p53 expression increased only with time (P< 0.001). Dose-dependent p53-associated G1 arrest, in the absence of DNA synthesis indicates an additional cytotoxic mechanism for SN-38, which requires higher concentrations than the S phase mechanism, and detection of which seems to involve p53. For incubations with the same ED (exposure x duration), apoptosis in HT29 cells was significantly higher for prolonged exposure to lower concentrations, whereas in LS174T cells there was a trend towards increased apoptosis with shorter exposures to higher concentrations, indicating a schedule effect of SN-38. Although expression of wild-type p53 leads to a more rapid induction of apoptosis, SN-38 cytotoxicity was generally greater in cells with mutant p53, as wild-type cells escaped apoptosis by p53 associated prolonged cell cycle arrest. Thus, pulsed schedules with higher doses may be more effective in cells expressing wild-type p53, whereas continued exposure with protracted schedules may be more active in cells expressing mutant p53.

Phase II trial of topotecan administered as a 21-day continuous infusion in previously untreated patients with stage IIIB and IV non-small-cell lung cancer

Topotecan (9-dimethylaminoethyl-10-hydroxycamptothecin) is a topoisomerase I inhibitor. Twenty-six patients with stage IIIB or IV non-small-cell lung cancer (NSCLC) who had received no prior chemotherapy were treated in a multicenter study with topotecan 0.6 mg/m2/day for 21 days by continuous intravenous infusion every 28 days; this starting dose was decreased to 0.5 mg/m2/day in the last 23 patients because of myelosuppression. There was one partial response, for a response rate of 4% (95% confidence interval, 0.1%-19.6%). Median survival was 9 months. One-year survival was 39%. Of the 58 lung cancer symptoms at baseline, 40% were resolved by the end of best response (all in the partial response patient, 62% in stable disease patients, 26% in progressive disease patients). Catheter-related infections complicated 19% of courses. Red-cell transfusions were given in 50% of courses. Toxicity included grade 4 neutropenia (4%), grade 3-4 anemia (19%), grade 4 thrombocytopenia (8%), and catheter-related infections (19% courses). Although the major objective response rate was only 4%, patients treated with topotecan given as a 21-day continuous intravenous infusion experienced a decrease in cancer-related symptoms and a 1-year survival of 39%.

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.

The CHO XRCC1 mutant, EM9, deficient in DNA ligase III activity, exhibits hypersensitivity to camptothecin independent of DNA replication

We have analyzed the X-ray-sensitive CHO mutant cell line EM9 for sensitivity to the topoisomerase I inhibitor comptothecin. These cells exhibit defective repair of single strand DNA breaks. Recently, EM9 were complemented the DNA ligase III interactive protein, XRCC1. Defective XRCC1 apparently accounts for the low DNA ligase III activity that may explain the single-strand break repair deficiency of EM9 cells. Here, we demonstrate cytotoxic hypersensitivity of EM9 cells following a brief camptothecin treatment. Both the S-phase and non-S-phase populations of EM9 exhibited camptothecin sensitivity relative to the parent cell line AA8. In AA8 cells, only the 55% of the population corresponding to the S-phase subpopulation were sensitive to camptothecin, while the remainder of the population were totally resistant to doses as high as 10 microM. The role of DNA replication in the camptothecin sensitivity was studied using the DNA polymerase inhibitor aphidicolin in co-treatment with camptothecin. Aphidicolin treatment fully protected AA8 cells from camptothecin cytotoxicity. In EM9 cells, aphidicolin protected the S-phase fraction to some degree but all the cells remained sensitive to camptothecin cytotoxicity. These results suggest that EM9 cells are sensitized to camptothecin by a mechanism that is independent of DNA replication and may be a consequence of the XRCC1 mutation or the associated deficiency in DNA ligase III activity. Mechanistic models for the replication-independent cytotoxicity of camptothecin in EM9 cells are discussed.

Phase I study of daily times five topotecan and single injection of cisplatin in patients with previously untreated non-small-cell lung carcinoma

BACKGROUND

The objectives were to determine the dose-limiting toxicity of topotecan in combination with cisplatin, to describe the principal toxicities, and to define the maximally-tolerated doses of the drugs in previously untreated patients with advanced non-small-cell lung carcinoma.

PATIENTS AND METHODS

The study was designed to evaluate escalated doses of topotecan (starting at 0.75 mg/m2/day) as a 30-minute infusion daily for five consecutive days with a fixed clinically-relevant dose of 75 mg/m2 cisplatin given on day 1, every three weeks.

RESULTS

Fifteen chemotherapy-naive patients entered the study and 14 were evaluable for toxicity. All 11 patients treated at the first topotecan/cisplatin dose level of 0.75/75 mg/m2, experienced at least one episode of grade 4 neutropenia. For six patients, absolute neutrophil counts were below 500/ml for more than five days, and two of them developed a grade 4 thrombocytopenia. At the next higher topotecan/cisplatin dose level (1.0/75 mg/m2), grade 4 neutropenia lasting longer than five days occurred in all three evaluable patients, including one patient who expired due to a severe neutropenia associated with sepsis. Non-hematologic toxicities, predominantly nausea and vomiting, were mild to moderate in severity and manageable. Four patients had partial responses (30.7%; 95% confidence interval (9%-61%) of relatively short duration.

CONCLUSION

Both severe neutropenia and thrombocytopenia precluded dose escalation of topotecan and cisplatin administered on this schedule. In previously untreated patients, the first topotecan/cisplatin dose level (0.75/75 mg/m2), was associated with intolerable myelosuppression, and, therefore, the dose levels evaluated in this study cannot be recommended for subsequent phase II investigations. The high toxicity of this schedule and the recent understanding of the pharmacokinetic interaction between those drugs may encourage the investigation of the alternate sequence of cisplatin after TPT in phase II studies.

Phase I trial and pharmacokinetic (PK) and pharmacodynamics (PD) study of topotecan using a five-day course in children with refractory solid tumors: a pediatric oncology group study

PURPOSE

A phase I trial was conducted in children with refractory solid tumors to determine the maximum tolerated dose (MTD), dose-limiting toxicity (DLT), pharmacokinetics, and pharmacodynamics for topotecan administered by a 30-min infusion for 5 consecutive days.

PATIENTS AND METHODS

Forty children with a variety of recurrent solid tumors, including nine patients with neuroblastoma and 10 with brain tumors, were given topotecan as a 30-min infusion for 5 consecutive days, beginning with a dose of 1.4 mg/m2/day. The dose was escalated in 20% increments after establishing that DLT was not present at the prior dose. Drug toxicity was graded using standard criteria. Dose-limiting toxicity was defined as grade 3 or 4 nonhematopoietic toxicity or grade 4 hematopoietic toxicity lasting > 7 days. Pharmacokinetic studies were performed during the first infusion course.

RESULTS

The DLT was hematopoietic and involved both platelets and neutrophils. Grade 4 hematopoietic toxicity of brief duration was seen at all dose levels. Over half of the patients received red blood cell transfusion support, and 19/40 received platelet transfusions. Hospital admissions for fever and neutropenia or for documented infections occurred in 32 of 169 courses of therapy. Gastrointestinal symptoms with nausea and vomiting or diarrhea were mild to moderate in 12 of the 40 patients. Antitumor responses were seen in three patients with neuroblastoma. An additional four patients (one with neuroblastoma, two with anaplastic astrocytomas, one with Ewing) had stable disease with continued therapy for > 6 months. Using a limited sampling model, pharmacokinetic studies were performed in 36 of the 40 patients. Topotecan lactone and total clearance were similar to those reported in other pediatric populations receiving topotecan by continuous infusion. A pharmacodynamic relation between systemic exposure to topotecan lactone and myclosuppression was observed.

CONCLUSIONS

In heavily pretreated children, the MTD for topotecan given by intermittent 30-min infusion for 5 days is 1.4 mg/m2 without GCSF and 2.0 mg/m2/day with GCSF. The dose-limiting toxicity is hematopoietic. Data from this study provide the basis for further studies of topotecan in children with cancer.

Moving the Frontiers of Cancer Chemotherapy for Solid Tumors by Changing the Scope of Drug Development

Our increasing knowledge on the pathogenetic mechanisms involved in the growth of cancer cells and on the molecular basis of cancer has influenced the development of anticancer agents. The realization that new targets should be evaluated for anti-cancer drug treatment has a.o. led to the introduction of the taxoids and topoisomerase I inhibitors. Attacking the known targets in a more sophisticated way led to the development of drugs with increased target specificity like Tomudex and Gemcitabine. Finally, using old drugs more efficiently by using pharmacokinetic and pharmacodynamic ananlysis hold a promise for the near future.

Adenocarcinoma of unknown primary: retrospective analysis of chemosensitivity of 313 freshly explanted tumors in a tumor cloning system

Cancer of unknown primary origin is the eighth most common form of malignancy and accounts for up to 10% of all neoplasms diagnosed. It is a set of heterogenous tumors with widely varying sensitivity to systemic chemotherapy. Over the past years progress has been made in identifying subsets of patients that can be effectively treated with chemotherapy and may achieve long-term survival even with metastatic disease. However, the large majority of cancers of unknown origin still is resistant to chemotherapy. In an attempt to identify conventional and investigational new agents with possible activity against cancers of unknown primary, we have retrospectively analyzed the results of chemosensitivity testing in a soft agar cloning system in vitro and have compared these data with published clinical trials. Between 1978 and 1993, a total of 19584 tumor specimens were studied using a variety of investigational or established antitumor agents. Of these, 615 (3.1%) were tumors of unknown origin and confirmed on pathology review. The largest histologic subgroup was adenocarcinoma (332, 54%). Sufficient numbers of cells for in vitro testing were obtained from 313 tumor specimens (94.3%). Of 278 agents tested in adenocarcinoma of unknown origin, borderline activity (< 20% in vitro response) was noted for 5-FU, doxorubicin, bleomycin, mitoxantrone, mitomycin-C, cisplatin, and etoposide. In vitro response rates of > or = 20% were observed for actinomycin-D, BCNU, melphalan, methotrexate, taxol, and vinblastine. In addition, several investigational agents including fludarabine, amira235, bisantrene, Dupont840, echinomycin, tiazofurin, LY104208 (vinzolidine), intoplicine, and topotecan had activity.(ABSTRACT TRUNCATED AT 250 WORDS)