Comparative activity of oral and parenteral topotecan in murine tumor models: efficacy of oral topotecan

Topoisomerases as anticancer targets

Many cancer type-specific anticancer agents have been developed and significant advances have been made toward precision medicine in cancer treatment. However, traditional or nonspecific anticancer drugs are still important for the treatment of many cancer patients whose cancers either do not respond to or have developed resistance to cancer-specific anticancer agents. DNA topoisomerases, especially type IIA topoisomerases, are proved therapeutic targets of anticancer and antibacterial drugs. Clinically successful topoisomerase-targeting anticancer drugs act through topoisomerase poisoning, which leads to replication fork arrest and double-strand break formation. Unfortunately, this unique mode of action is associated with the development of secondary cancers and cardiotoxicity. Structures of topoisomerase-drug-DNA ternary complexes have revealed the exact binding sites and mechanisms of topoisomerase poisons. Recent advances in the field have suggested a possibility of designing isoform-specific human topoisomerase II poisons, which may be developed as safer anticancer drugs. It may also be possible to design catalytic inhibitors of topoisomerases by targeting certain inactive conformations of these enzymes. Furthermore, identification of various new bacterial topoisomerase inhibitors and regulatory proteins may inspire the discovery of novel human topoisomerase inhibitors. Thus, topoisomerases remain as important therapeutic targets of anticancer agents.

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.

A phase I clinical trial of weekly oral topotecan for relapsed small cell lung cancer

PURPOSE

To determine the dose-limiting toxicities (DLTs) and the maximum tolerated dose (MTD) of oral topotecan administered weekly in patients with relapsed small cell lung cancer (SCLC).

PATIENTS AND METHODS

Patients were treated with oral topotecan on days 1, 8, and 15, every 28 days. The dose was escalated by 0.5 mg/m² increments from the starting dose of 3 mg/m² until the MTD was reached. DLTs were defined as grade 4 neutropenia, febrile neutropenia, grade 4 thrombocytopenia, non-hematologic toxicity ≥grade 3, any toxicity precluding the treatment on days 8 or 15 of the first cycle, or delay of the second cycle for more than 7 days.

RESULTS

Eighteen patients were enrolled. Thirteen patients received oral topotecan as second-line and five as third- or further-line treatment. The DLT level was reached at 4.5 mg/m², and the MTD was determined to be 4 mg/m². DLTs consisted of grade 2/3 neutropenia and grade 2 thrombocytopenia precluding treatment on day 15 of the first cycle or on day 1 of the second cycle. The most frequent toxicities were grade 2-3 neutropenia (27.8 % of patients), grade 2-3 anemia (33.3 %), grade 2 thrombocytopenia (16.7 %), and grade 2-3 fatigue (44.4 %). The response rate was 11.1 %, the median progression-free survival 2.3 months, and the median overall survival 5.1 months.

CONCLUSION

The recommended phase II dose of weekly oral topotecan in pretreated patients with SCLC is 4 mg/m² on days 1, 8, and 15 every 28 days.

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.

Phase I trial of weekly topotecan and gemcitabine in patients with solid tumors

OBJECTIVE

This phase I trial was designed to determine the maximal tolerated dose (MTD) of the combination of topotecan and gemcitabine given in a weekly schedule.

MATERIALS AND METHODS

In this single-arm, open label, dose-escalation study, we administered topotecan (0.75-1.5 mg/m) and gemcitabine (1000 mg/m) on days 1, 8, and 15 every 4 weeks to 25 patients with advanced solid tumors.

RESULTS

The topotecan MTD, when combined with gemcitabine, was 1.25 mg/m/wk. Dose-limiting toxicities consisted of febrile granulocytopenia in 2 patients at the highest dose level. At the MTD, no episodes of granulocytopenia were observed, whereas 2/9 patients exhibited grade 3 thrombocytopenia. Other common grades 3-4 adverse events across all cohorts included non-neutropenic infections, fatigue, skin reactions, vomiting, and fever. One partial response and 2 stable diseases were observed in patients with nasopharyngeal carcinoma. Disease stabilization was also observed in patients with squamous cell carcinoma of the head and neck (3), nonsmall cell lung cancer (1), and thymoma (1).

CONCLUSIONS

Topotecan and gemcitabine combined in a weekly schedule exhibit a favorable toxicity profile. Efficacy results support the further evaluation of this regimen in patients with head and neck cancer (particularly nasopharyngeal carcinoma).

A Phase I trial of weekly docetaxel and topotecan for solid tumors

BACKGROUND/AIMS

Topotecan and docetaxel are active agents in the treatment of various malignant diseases. Both drugs cause dose-limiting hematologic toxicity. This study defines the maximum tolerated dose (MTD) and dose-limiting toxicity of weekly topotecan when administered in combination with docetaxel 25 mg/m(2) given day 1, 8,15 every 28 days.

METHODS

Thirteen patients were enrolled. Median age was 62 years. Majority of the patients had lung cancer.

RESULTS

The maximum tolerated dose was docetaxel 25 mg/m(2) and topotecan 3 mg/m(2) administered weekly. Dose-limiting toxicity was febrile neutropenia. Eight patients developed at least grade 3 neutropenia in all cycles. Non-hematologic toxicities were mild. No objective responses were noted. Two patients with non-small cell lung cancer had stable disease as a best response.

CONCLUSION

Combination docetaxel and topotecan given weekly is tolerable. The recommended phase II dose is docetaxel 25 mg/m(2) and topotecan 3 mg/m(2) day 1, 8, 15 every 28 days.

Pegylated-liposomal doxorubicin and oral topotecan in eight children with relapsed high-grade malignant brain tumors

BACKGROUND

The combination of topoisomerase I and II chemotherapeutic agents has shown promising preclinical synergistic effects in the treatment of high-grade malignant brain tumors such as high-grade gliomas and choroid plexus carcinomas. To confirm the effectiveness of this treatment combination and determine its possible toxicity, we conducted a retrospective review of the charts of children who received the therapy.

METHODS

Patients with relapsed malignant brain tumors who were given an individualized treatment of pegylated (PEG)-liposomal doxorubicin and topotecan were included in our study. PEG-liposomal doxorubicin was given intravenously at a dosage of 30-40 mg/m(2) over 4 h once every 4 weeks. Additionally, an intravenous formulation of topotecan was given orally twice daily and was increased on an individual basis from a starting dosage of 0.3 mg/m(2) per application to a total daily dosage of 0.6 mg/m(2).

RESULTS

Eight patients were included. The main toxicity (NCI-CTC) after three cycles of the combination therapy was grade IV hematotoxicity (n = 3); grade III hematotoxicity (n = 2), grade III stomatitis (n = 1), grade III infection (n = 2), grade III diarrhea (n = 1); and grade II dermatitis (n = 1). In four patients, stable disease was achieved for 9, 23, more than 24, and more than 48 weeks, respectively.

CONCLUSION

The schedule of PEG-liposomal doxorubicin with 30-40 mg/m(2) every 4 weeks in combination with oral topotecan resulted in tumor response, but the toxicity was high. An individualized increasing dose of PEG-liposomal doxorubicin 10-20 mg/m(2) every two weeks is now recommended.

Weekly topotecan in heavily pretreated patients with recurrent epithelial ovarian carcinoma

OBJECTIVE

To investigate weekly topotecan in heavily pretreated patients with recurrent ovarian cancer.

METHODS

The records of patients with recurrent epithelial ovarian cancer who were treated with weekly topotecan after failure of > or =1 prior regimen were reviewed. Patients received topotecan (median starting dose approximately 2.5 mg/m(2)) on days 1, 8, and 15 of a 28-day cycle. Antitumor response was assessed after 2 cycles by serial CA-125 levels.

RESULTS

Thirty-five heavily pretreated patients received a mean of 5 cycles of topotecan (range, 1-13 cycles). Thirty-two patients had definable platinum sensitivity (16 sensitive, 8 resistant, 8 refractory). Median age was 56 years. A total of 177 cycles (534 weeks) of topotecan was administered. Hematologic toxicity was generally mild, and no grade 4 toxicities were observed. Grade 3 hematologic toxicity, including leukopenia, neutropenia, thrombocytopenia, and anemia, was observed in 2, 2, 1, and 0 patients, respectively. No patients experienced grade 3 or 4 nonhematologic toxicity. Based on serial CA-125 measurements, there were 1 (3%) complete and 5 (15%) partial responses, with 1 of the partial responses in a patient with platinum-refractory disease. Stable disease was reported in 13 (38%) patients, including 5 patients with platinum-resistant/refractory disease.

CONCLUSION

Weekly topotecan demonstrates activity and is well tolerated compared with historical data with the standard 5-day schedule. Higher doses may be warranted because of the high tolerability shown for weekly topotecan. Weekly topotecan may be an appropriate treatment option for patients with recurrent ovarian cancer, especially heavily pretreated patients who might require dosing schedules with improved tolerability.

Retrospective analysis of weekly topotecan as salvage therapy in relapsed ovarian cancer

OBJECTIVE

To retrospectively investigate the safety and efficacy of weekly topotecan in heavily pretreated patients with ovarian cancer.

METHODS

Data were collected by retrospective review of patient records. Eligible patients had received > or =2 prior regimens for ovarian cancer before treatment with weekly topotecan. Efficacy was determined by measurable disease or CA 125 levels. Adverse event and growth factor support data were also collected.

RESULTS

Fifty patients (median age, 61 years) were evaluable for safety and received a total of 244 4-week cycles of therapy (median, 3; range, 1-21 cycles). Most patients (84%) had measurable disease, and 30% had performance status of > or =2. Patients had received two to six prior treatments for ovarian cancer. Median weekly dose per patient was topotecan 3.7 mg/m(2). Grade 4 hematologic toxicities (generally manageable) occurred in 4% of patients. One patient had febrile neutropenia. Grade 3/4 nonhematologic toxicities were fatigue in two (4%) patients. Forty-two patients were evaluable for response. Of 35 evaluable patients with measurable disease, 11 (31%) had a partial response (median duration, 3 months), and 15 (43%) patients had stable disease (median duration, 3.5 months). Of 41 evaluable patients with elevated CA 125 (median, 154 U/l; range, 47-7200 U/l), 11 (27%) had > or =50% decreases or normalization of CA 125 levels. Median time to progression in all patients with stable disease has not been reached (follow-up range, 1.5-17.3 months).

CONCLUSIONS

Weekly topotecan is active and well tolerated in heavily pretreated patients with relapsed ovarian cancer. Prospective studies of this regimen are warranted.

Emerging Role of Weekly Topotecan in Recurrent Small Cell Lung Cancer

Small cell lung cancer (SCLC) is an aggressive tumor that often metastasizes before the primary cancer is diagnosed. Patients with SCLC are typically elderly and often have comorbidities that may predispose them to adverse events during therapy. Although topotecan (Hycamtin; GlaxoSmithKline; Philadelphia, PA), 1.5 mg/m(2)/day via a 30-minute i.v. infusion on days 1-5 of a 21-day cycle, is a standard therapy for relapsed SCLC, this regimen can result in significant neutropenia, especially in previously treated patients. This hematologic toxicity is noncumulative and reversible, but its management can be challenging in this poor-prognosis population. Therefore, alternate treatment regimens have been investigated. Weekly topotecan (4.0 mg/m(2)) is currently investigational and has shown promising activity and favorable tolerability in patients with relapsed ovarian cancer, another aggressive malignancy with a poor prognosis. Preliminary results from a phase II trial of weekly bolus topotecan (4.0 mg/m(2)) in patients with recurrent SCLC were recently reported, and this regimen was generally well tolerated. Furthermore, weekly topotecan has been successfully included in several combination therapy regimens in patients with a variety of solid tumors. In untreated SCLC patients, a combination regimen of weekly topotecan, paclitaxel (Taxol; Bristol-Myers Squibb; Princeton, NJ), and cisplatin (Platinol; Bristol-Myers Squibb) was explored and found to be well tolerated and active in patients with extensive and limited-stage disease. Further clinical trials of weekly topotecan and regimens that include weekly topotecan in the SCLC setting are warranted.

Oral topotecan in children with recurrent or progressive high-grade glioma: a Phase I/II study by the German Society for Pediatric Oncology and Hematology

BACKGROUND

Continuous oral treatment with topotecan may be more effective than the typical 1-day and 5-day treatment schedules. In previous studies of continuous treatment with topotecan, increased intestinal side effects were reported in adult patients; however, the experience in pediatric patients and patients with high-grade glioma is quite limited.

METHODS

Thirty-two pediatric patients with recurrent high-grade glioma (16 females and 16 males; median age, 9.5 years) were enrolled in the current Phase I/II study. Tumor locations included the cerebral cortex (n = 5), pons (n = 18), and other sites (n = 9). An injectable formulation of topotecan was administered orally, in ice-cold orange juice, once daily. The starting dose of 0.4 mg/m(2) per day was escalated on a patient-by-patient basis. At each patient's maximum dose, blood samples were obtained for the determination of plasma hydroxytopotecan and topotecan lactone concentrations and for the calculation of pharmacokinetic quantities.

RESULTS

The toxicity criteria for a maximum tolerated topotecan dose were met in only 19 patients. The primary toxicity type was hematologic. The median maximum tolerated dose was 0.9 mg/m(2) per day (n = 19). The calculated maximum total plasma topotecan concentration was 3.8 ng/mL (n = 7), with an area under the concentration-time curve of 38.4 ng. hours/mL and a half-life of 4.1 hours, which would result in the complete disappearance of topotecan from the plasma after 12 hours. Objective responses were observed in 2 of 13 evaluable patients and lasted for 2.5 and 9 months, respectively (continuous clinical remission, 1 of 14 patients; partial response, 2 of 14 patients; stable disease, 7 of 14 patients; progressive disease, 4 of 14 patients).

CONCLUSIONS

Oral topotecan (median dose, 0.9 mg/m(2) per day) administered once daily was well tolerated and somewhat effective in children with recurrent high-grade glioma. A schedule in which the daily dose is split so that dosing is performed twice daily may be superior to the current schedule.

Phase I and pharmacokinetic study of topotecan administered orally once daily for 5 days for 2 consecutive weeks to pediatric patients with refractory solid tumors

PURPOSE

We conducted a phase I trial of the injectable formulation of topotecan given orally once daily for 5 days for 2 consecutive weeks (qd x 5 x 2) in pediatric patients with refractory solid tumors.

PATIENTS AND METHODS

Cohorts of two to six patients received oral topotecan at 0.8, 1.1, 1.4, 1.8, and 2.3 mg/m(2)/d every 28 days for a maximum of six courses. Twenty patients (median age, 10.6 years) received a total of 51 courses. Eight patients received topotecan capsules during course 2 only.

RESULTS

Dose-limiting toxicity occurred at 2.3 mg/m(2)/d and consisted of prolonged grade 4 neutropenia (n = 2), grade 3 stomatitis as a result of radiation recall (n = 1), grade 3 hemorrhage (epistaxis) in the presence of grade 4 thrombocytopenia (n = 1), and grade 3 diarrhea in the presence of Clostridium difficile infection (n = 1). Dose-limiting, prolonged grade 4 neutropenia and thrombocytopenia occurred in one patient at 1.4 mg/m(2)/d. Infrequent toxicities were mild nausea, vomiting, elevated liver ALT or AST, and rash. The maximum-tolerated dosage was 1.8 mg/m(2)/d; the mean (+/- standard deviation) area under the plasma concentration-time curve for topotecan lactone at this dosage was 20.9 +/- 8.4 ng/mL. h. The population mean (+/- standard error) oral bioavailability of the injectable formulation was 0.27 +/- 0.03; that of capsules was 0.36 +/- 0.06 (P =.16). Disease stabilized in nine of 19 assessable patients for 1.5 to 6 months.

CONCLUSION

Oral topotecan (1.8 mg/m(2)/d) on a qd x 5 x 2 schedule is well tolerated and warrants additional testing in pediatric patients.

Weekly topotecan in the management of lung cancer

Chemotherapy agents require a range of administration schedules, including 3-weekly, 4-weekly and daily administration. Some agents, for example gemcitabine and vinorelbine, have been developed for use in a weekly regimen. The possibility of administering other agents using a weekly schedule is being investigated. Weekly schedules offer practical benefits in terms of convenience to patients and allow drugs to be combined more easily. In addition, toxicity may be reduced. The standard 5-day schedule of topotecan has demonstrated effectiveness and patient benefits. Topotecan at this dose is generally well tolerated, with dose-limiting myelosuppression. Preclinical data supported intermittent dosing with topotecan and clinical studies with weekly dosing in ovarian cancer have indicated reduced myelosuppression compared with the 5-day regimen. Several studies in non-small cell lung cancer investigated topotecan combined with cisplatin or gemcitabine and confirmed these findings. However, further studies are needed to confirm that efficacy of topotecan (response and survival) is maintained with the altered regimen.

Alternate dosing schedules for topotecan in the treatment of recurrent ovarian cancer

Topotecan has demonstrated efficacy in the treatment of both platinum-sensitive and platinum-resistant recurrent ovarian cancer. However, the optimal dosing for topotecan has not been established. The standard dosing regimen is 1.5 mg/m(2)/day on days 1-5 of a 21-day cycle, with response rates ranging from 13%-33%. Although the resulting hematologic toxicities are reversible and noncumulative, this schedule is associated with significant myelosuppression. Ongoing clinical phase I and II trials have evaluated alternative dosing schedules such as the 21-day 24-hour continuous intravenous (c.i.v.), the 3-day i.v. bolus, the weekly 72-hour c.i.v., the weekly 24-hour c.i.v., and the weekly bolus i.v. regimens. Prolonged exposure to topotecan has been shown to increase the efficacy of topotecan, whereas shorter regimens decrease exposure to the drug and therefore decrease toxicity. Preliminary studies investigating the weekly bolus i.v. regimen have demonstrated response rates comparable with those achieved with the standard dosing regimen, with a lower frequency of severe toxicity. Although randomized, controlled comparative trials are necessary to determine relative efficacy, results from studies utilizing other alternative regimens are less encouraging, especially for lower-risk patients with platinum-sensitive ovarian cancer who are likely to tolerate higher doses of topotecan. Optimizing the dosing regimen will also increase the quality of life for the patient through increased efficacy, decreased toxicity, and increased convenience of administration. Continued investigation of the weekly i.v. bolus is needed to fully elucidate the contribution of this regimen to the current armamentarium used in the treatment of patients with relapsed ovarian cancer.

Protracted intermittent schedule of topotecan in children with refractory acute leukemia: a pediatric oncology group study

PURPOSE

To determine dose-limiting toxicity (DLT) and maximum-tolerated dose (MTD) of a protracted, intermittent schedule of daily 30-minute infusions of topotecan (TPT) for up to 12 consecutive days, every 3 weeks, in children with refractory leukemia.

PATIENTS AND METHODS

Forty-nine children were enrolled onto this phase I trial (24 with acute nonlymphoblastic leukemia [ANLL] and 25 with acute lymphoblastic leukemia [ALL]). TPT dosage was escalated from 2.0 to 5.2 mg/m(2)/d for 5 days and 2.4 mg/m(2)/d from 7 days to the same dose for 9 and 12 days in cohorts of three to six patients when no DLT was identified. TPT pharmacokinetics were studied in 33 children once or twice (first and last doses in patients who received TPT for > 7 days).

RESULTS

Seventy assessable courses of TPT were administered to 49 children who had refractory leukemia. DLTs were typhlitis, diarrhea, and mucositis, and the MTD was 2.4 mg/m(2)/d for 9 days in this group of heavily pretreated children. In 33 patients, the median TPT lactone clearance after the first dose was 19.2 L/h/m(2) (range, 9.4 to 45.9 L/h/m(2)) and did not change during the course. There were significant responses (one complete response [CR] and four partial responses [PR] in patients with ANLL and one CR and two PRs in patients with ALL), and all but one were at dosages of TPT given for at least 9 days.

CONCLUSION

The MTD was 2.4 mg/m(2)/d for 9 days. Further testing is warranted of TPT's schedule dependence in children with leukemia.

Topoisomerase I inhibition with topotecan: pharmacologic and clinical issues

Topoisomerase I (topo-I) inhibitors are a new class of anticancer agents with a mechanism of action aimed at interrupting DNA replication in cancer cells, the result of which is cell death. Most, if not all, topo-I inhibitors are derivatives of the plant extract camptothecin. Topotecan is a derivative of camptothecin which has been structurally modified to increase water solubility. The pharmacokinetic profile of topotecan is usually characterised by a two-compartment model and is linear in the dose range of 0.5 - 3.5 mg/m(2). Current clinical trials suggest antitumour activity against a variety of human tumour types, including ovarian cancer, non-small cell lung cancer (NSCLC) and non-lymphocytic haematologic malignancies. The main dose-limiting toxicity (DLT) is non-cumulative myelosuppression. Non-haematologic toxicities are usually mild. Based on several Phase I studies, the recommended Phase II dose was 1.5 mg/m(2)/day iv. for 5 days. Current Phase I and Phase II trials are evaluating the combination of topotecan with other chemotherapeutic agents to increase the therapeutic benefits of topotecan. The DLT in these trials is mainly myelosuppression.

Efficacy and toxicity profile of oral topotecan in a panel of human tumour xenografts

On the basis of their mechanism of action (cell killing during DNA replication) and the potential reversibility of the drug effects, protracted therapy with camptothecins is reported to provide optimal antitumour effects. Furthermore, oral administration may be a useful modality for optimisation of treatment. The aim of this study was to compare the therapeutic profile of topotecan given orally or intravenously in human tumours xenografted into athymic nude mice. The drug topotecan was given according to an intermittent (every fourth day, four times) or daily (qdx5/weeklyx5-10 weeks; only orally) schedule. Tumour growth inhibition and persistence of drug effects were assessed and compared with untreated mice. In a panel of seven tumour xenografts, oral topotecan was at least as effective on three and significantly more effective on four tumours. Using the intermittent schedule, the maximum tolerated dose (MTD) was comparable for the two routes (15 mg/kg), but the toxicity profile suggested a better tolerability in terms of lethal effects after oral administration. The daily oral treatment of low drug doses allowed a higher cumulative dose to be delivered with improved antitumour efficacy (2/10 cured in a large cell lung cancer) and no evidence of toxicity. In spite of the low bioavailability of oral topotecan (23.5%), the persistent plasma levels of the drug suggest that the time of exposure to the drug is more critical than the plasma concentrations for antitumour efficacy. This interpretation is consistent with the increased efficacy of prolonged daily treatment with low-dose levels. The results may have implications for the future design of clinical studies.

New oral chemotherapeutic agents for lung cancer

Anticancer treatment has recently shifted to include a broad range of antineoplastic therapies. Old agents are continuously being re-evaluated, and new mechanisms of treatment are rapidly being explored and developed. At the same time, the patient's perceived quality of life, adverse effects of therapy, time demands, and healthcare costs have become paramount in the treatment process. Lung cancer is the most common cause of cancer death in the USA, and because many of the patients are older or debilitated, these issues become all the more important. The oral administration of anticancer therapy offers both quality-of-life and healthcare cost advantages. Oral forms of 3 new cytotoxic agents and 2 novel oral therapies are discussed. Vinorelbine, a vinca alkaloid, has well documented activity in non-small cell lung cancer. Myelosuppression is dose limiting; neurotoxicity is rare. Satraplatin (JM-216), an oral platinum derivative, shows activity in lung cancer with a favourable adverse effect profile, with no neurotoxicity or nephrotoxicity. The oral topoisomerase I inhibitor topotecan may be ideal for obtaining long term low plasma drug concentrations, which appears to maximise efficacy. LGD-1069 is a retinoid X receptor agonist that modulates cell proliferation, and BAY-129566, a matrix metalloproteinase inhibitor, appears to interrupt both the processes of angiogenesis and metastasis. LGD-1069 and BAY-129566 are nontraditional anticancer agents which may be used in conjunction with chemotherapy, other modalities, or in prevention. These 5 agents will be discussed with particular reference to recent developments in the treatment of lung cancer.

Animal models for studying the action of topoisomerase I targeted drugs

Almost 30 years after the unsuccessful clinical evaluation of camptothecin sodium, there has been a revival in interest in this class of agent that poisons topoisomerase I. Currently there are four camptothecin analogues in clinical trials each at different levels of advancement. Clinical data suggest that patterns of antitumor activity and toxicity profiles differ between analogues. In preclinical models antitumor activity appears to be highly schedule-dependent. Here we review rodent and human tumor models used in evaluation of efficacy, and models used to predict toxicities of these compounds. The major limitation of rodent models is that the mouse tolerates significantly greater systemic exposure to each camptothecin analogue than do patients. This leads to a false overprediction of potential clinical activity. However, responses of human tumor xenografts in mice are highly predictive of responses of clinical cancer when camptothecins are administered at dose levels achieving similar systemic exposure in mice. Development of assays that identify analogues that maintain therapeutic activity in mice, but have less species differential toxicity, particularly to the hematopoietic system, may provide an early screen to select compounds having greater clinical utility.

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.

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.

Camptothecin and its analogs. An overview of their potential in cancer therapeutics

From the outset of their clinical testing the camptothecins have shown antitumor activity against gastrointestinal cancer. With the definition of mechanism of action and introduction of several analogs their antitumor activity spectrum has expanded to include ovarian, cervical, small-cell and non-small cell lung cancers and malignant lymphomas, among others. The wide range of trials in these disease areas have been reviewed for CPT-11, topotecan, and 9-aminocamptothecin. A therapeutic role is anticipated for these and other camptothecins in these disease sites. Issues in guiding treatment indications and clinical development include: 1) pharmacokinetics and scheduling relevant to each of the drugs, with the oral route emerging as a practical way for testing prolonged exposure; 2) dose-intensification with cytokines, and its relevance in maintaining effective doses particularly in combination with other myelosuppressive drugs; and 3) pharmacodynamic determinants of response-an area of research that is particularly attractive because topoisomerase I is the target for camptothecins.

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.