Topoisomerase I Inhibitors: An Overview of the Camptothecin Analogs

Immunoconjugates as an Efficient Platform for Drug Delivery: A Resurgence of Natural Products in Targeted Antitumor Therapy

The present review provides a detailed and comprehensive discussion on antibody-drug conjugates (ADCs) as an evolving new modality in the current therapeutic landscape of malignant diseases. The principle concepts of targeted delivery of highly toxic agents forsaken as stand-alone drugs are examined in detail, along with the biochemical and technological tools for their successful implementation. An extensive analysis of ADCs' major components is conducted in parallel with their function and impact on the stability, efficacy, safety, and resistance profiles of the immunoconjugates. The scope of the article covers the major classes of currently validated natural compounds used as payloads, with an emphasis on their structural and mechanistic features, natural origin, and distribution. Future perspectives in ADCs' design are thoroughly explored, addressing their inherent or emerging challenges and limitations. The survey also provides a comprehensive overview of the molecular rationale for active tumor targeting of ADC-based platforms, exploring the cellular biology and clinical relevance of validated tumor markers used as a "homing" mechanism in both hematological and solid tumor malignancies.

The cross talk of ubiquitination and chemotherapy tolerance in colorectal cancer

Ubiquitination, a highly adaptable post-translational modification, plays a pivotal role in maintaining cellular protein homeostasis, encompassing cancer chemoresistance-associated proteins. Recent findings have indicated a potential correlation between perturbations in the ubiquitination process and the emergence of drug resistance in CRC cancer. Consequently, numerous studies have spurred the advancement of compounds specifically designed to target ubiquitinates, offering promising prospects for cancer therapy. In this review, we highlight the role of ubiquitination enzymes associated with chemoresistance to chemotherapy via the Wnt/β-catenin signaling pathway, epithelial-mesenchymal transition (EMT), and cell cycle perturbation. In addition, we summarize the application and role of small compounds that target ubiquitination enzymes for CRC treatment, along with the significance of targeting ubiquitination enzymes as potential cancer therapies.

Microbiota-Host-Irinotecan Axis: A New Insight Toward Irinotecan Chemotherapy

Irinotecan (CPT11) and its active metabolite ethyl-10-hydroxy-camptothecin (SN38) are broad-spectrum cytotoxic anticancer agents. Both cause cell death in rapidly dividing cells (e.g., cancer cells, epithelial cells, hematopoietic cells) and commensal bacteria. Therefore, CPT11 can induce a series of toxic side-effects, of which the most conspicuous is gastrointestinal toxicity (nausea, vomiting, diarrhea). Studies have shown that the gut microbiota modulates the host response to chemotherapeutic drugs. Targeting the gut microbiota influences the efficacy and toxicity of CPT11 chemotherapy through three key mechanisms: microbial ecocline, catalysis of microbial enzymes, and immunoregulation. This review summarizes and explores how the gut microbiota participates in CPT11 metabolism and mediates host immune dynamics to affect the toxicity and efficacy of CPT11 chemotherapy, thus introducing a new concept that is called "microbiota-host-irinotecan axis". Also, we emphasize the utilization of bacterial β-glucuronidase-specific inhibitor, dietary interventions, probiotics and strain-engineered interventions as emergent microbiota-targeting strategies for the purpose of improving CPT11 chemotherapy efficiency and alleviating toxicity.

Temozolomide with irinotecan versus temozolomide, irinotecan plus bevacizumab for recurrent medulloblastoma of childhood: Report of a COG randomized Phase II screening trial

BACKGROUND

Approximately 30% of children with medulloblastoma (MB) experience recurrence, which is usually incurable. This study compared the overall survival (OS) of patients receiving temozolomide (TMZ) and irinotecan with that of patients receiving TMZ, irinotecan, and bevacizumab for recurrent MB/central nervous system (CNS) primitive neuroectodermal tumor (PNET).

METHODS

Patients with relapsed/refractory MB or CNS PNET were randomly assigned to receive TMZ (150 mg/m² /day PO on days 1-5) and irinotecan (50 mg/m² /day IV on days 1-5) with or without bevacizumab (10 mg/kg IV on days 1 and 15).

RESULTS

One hundred five patients were eligible and treated on study. Median OS was 13 months in the standard arm and 19 months with the addition of bevacizumab; median event-free survival (EFS) was 6 months in the standard arm and 9 months with the addition of bevacizumab. The hazard ratio for death from the stratified relative-risk regression model is 0.63. Overall, 23 patients completed 12 courses of planned protocol therapy, 23% (12/52) in the experimental arm with bevacizumab versus 21% (11/53) in the standard arm. Toxicity profiles were comparable in both treatment arms. The estimate of the incidence of feasibility events associated with the bevacizumab arm is three of 52 (5.8%) (95% CI 1.2-16%). Events included myelosuppression, electrolyte abnormalities, diarrhea, and elevated transaminases. One intracranial hemorrhage event was observed in each arm.

CONCLUSION

The addition of bevacizumab to TMZ/irinotecan significantly reduced the risk of death in children with recurrent MB. The combination was relatively well tolerated in this heavily pretreated cohort. The three-drug regimen demonstrated a sufficient risk reduction to warrant further investigation.

Irinotecan and Gemcitabine as Second-Line Treatment in Patients with Malignant Pleural Mesothelioma following Platinum plus Pemetrexed Chemotherapy: A Retrospective Study

BACKGROUND

Cisplatin-pemetrexed combination chemotherapy is the current standard primary treatment for malignant pleural mesothelioma (MPM). It was first approved for untreated and unresectable MPM in the 2003 National Comprehensive Cancer Network (NCCN) guidelines. However, to date, standard treatments for patients with MPM who previously underwent chemotherapy, as recommended by the NCCN Malignant Pleural Mesothelioma guidelines, have been inadequate. To explore treatment options for such patients, we performed this retrospective study of patients who received irinotecan plus gemcitabine as second-line therapy for MPM.

METHODS

We investigated 62 patients diagnosed with unresectable MPM between January 2008 and October 2017 who experienced recurrence following cisplatin treatment (or carboplatin) plus pemetrexed or pemetrexed monotherapy as first-line treatment, and who underwent irinotecan plus gemcitabine combination therapy as second-line treatment. Irinotecan (60 mg/m2) and gemcitabine (800 mg/m2) were administered on days 1 and 8 every 3 weeks, including a 1-week washout period. Our endpoints were efficacy, survival period, and toxicity.

RESULTS

patients' median age was 65 years (range 50-79), and the histological MPM types were epithelioid (n = 48), sarcomatoid (n = 6), biphasic (n = 6), and desmoplastic (n = 2). One patient experienced a partial response, 40 had stable disease, and 21 had progressive disease. The disease control rate was 66.1% and the response rate 2.1%. Additionally, the median progression-free and overall survival time were 5.7 and 11.3 months, respectively. The most common adverse events were neutropenia (32.2%), loss of appetite (16.1%), nausea/diarrhea (11.3%), and thrombocytopenia/phlebitis (9.7%). Grade 3 adverse events included neutropenia (12.9%) and thrombocytopenia/phlebitis (2.1%); however, all adverse events were managed with symptomatic therapy.

CONCLUSIONS

Despite the fact that second-line irinotecan plus gemcitabine combination therapy did not produce marked tumor shrinkage, it achieved a relatively high disease control rate of >65% with an acceptable toxicity profile. Hence, the combination of irinotecan plus gemcitabine may be considered for MPM treatment, with consideration of combination with immune checkpoint inhibitors as a potential next step.

Trastuzumab Deruxtecan (DS-8201a): The Latest Research and Advances in Breast Cancer

The development of antibody-drug conjugates composed of a cytotoxic agent and a monoclonal antibody carrier offers an important alternative to classic chemotherapy strategies. Trastuzumab deruxtecan (DS-8201a) is a next-generation antibody-drug conjugate composed of a monoclonal anti-HER2 antibody and a topoisomerase I inhibitor, an exatecan derivative (DX-8951f). DS-8201a resulted in favorable outcomes in HER2-positive heavily pretreated breast cancer patients and also had a promising efficacy in patients with HER2-negative/low-expressing disease, whose options are limited. Interestingly, a recently published phase 2 trial (NCT03248492) reported 60% overall response and 97% disease control in patients with HER2-positive disease previously treated with multiple regimens, including trastuzumab emtansine. On the basis of recent clinical trials, the US Food and Drug Administration granted accelerated approval to DS-8201a in advanced or unresectable HER2-positive breast cancer pretreated with at least two HER2-targeting treatment lines. We review all preclinical and clinical data of DS-8201a regarding breast cancer.

Irinotecan-Still an Important Player in Cancer Chemotherapy: A Comprehensive Overview

Irinotecan has been used in the treatment of various malignancies for many years. Still, the knowledge regarding this drug is expanding. The pharmacogenetics of the drug is the crucial component of response to irinotecan. Furthermore, new formulations of the drug are introduced in order to better deliver the drug and avoid potentially life-threatening side effects. Here, we give a comprehensive overview on irinotecan’s molecular mode of action, metabolism, pharmacogenetics, and toxicity. Moreover, this article features clinically used combinations of the drug with other anticancer agents and introduces novel formulations of drugs (e.g., liposomal formulations, dendrimers, and nanoparticles). It also outlines crucial mechanisms of tumor cells’ resistance to the active metabolite, ethyl-10-hydroxy-camptothecin (SN-38). We are sure that the article will constitute an important source of information for both new researchers in the field of irinotecan chemotherapy and professionals or clinicians who are interested in the topic.

Prediction of irinotecan toxicity in metastatic colorectal cancer patients based on machine learning models with pharmacokinetic parameters

Irinotecan (CPT-11) is a drug used against a wide variety of tumors, which can cause severe toxicity, possibly leading to the delay or suspension of the cycle, with the consequent impact on the prognosis of survival. The main goal of this work is to predict the toxicities derived from CPT-11 using artificial intelligence methods. The data for this study is conformed of 53 cycles of FOLFIRINOX, corresponding to patients with metastatic colorectal cancer. Supported by several demographic data, blood markers and pharmacokinetic parameters resulting from a non-compartmental pharmacokinetic study of CPT-11 and its metabolites (SN-38 and SN-38-G), we use machine learning techniques to predict high degrees of different toxicities (leukopenia, neutropenia and diarrhea) in new patients. We predict high degree of leukopenia with an accuracy of 76%, neutropenia with 75% and diarrhea with 91%. Among other variables, this study shows that the areas under the curve of CPT-11, SN-38 and SN-38-G play a relevant role in the prediction of the studied toxicities. The presented models allow to predict the degree of toxicity for each cycle of treatment according to the particularities of each patient.

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.

Liver toxicity in colorectal cancer patients treated with first-line FOLFIRI-containing regimen: a single institution experience

BACKGROUND

Chemotherapy-induced toxic liver injury is a relevant issue in the clinical management of patients affected with metastatic colorectal cancer (mCRC). This retrospective study evaluated patterns of liver toxicity in patients treated with FOLinic acid, Fluorouracil, IRInotecan (FOLFIRI)-based regimens.

METHODS

One hundred and fifty-six mCRC patients treated at the University Campus Bio-Medico between January 2003 and January 2013 were included in this retrospective analysis. All patients received a FOLFIRI backbone-based chemotherapy. Basal liver enzymes levels were assessed before starting the treatment and before every therapy course. R ratio and the aspartate aminotransferase/alanine aminotransferase ratio were calculated.

RESULTS

Ninety-one patients were male versus 55 female, and the median age of the population was 62 years (range: 38-83). Most patients had liver involvement at the beginning of first-line regimen (101 patients, 64.74%) and 59 patients had received a previous 5-FU based therapy in the adjuvant setting (37.82%). Aspartate aminotransferase level (167.87 vs 41.05 U/l; p < 0.001), Alanine aminotransferase level (94.48 vs 39.80 U/l; p = 0.004) and alkaline phosphatase (289.0 vs 172.44 U/l; p = 0.02) were significantly increased during the first 3 months of treatment. In the entire population, the calculated R ratio was 3.96 (95% CI: 3.25-4.51). In all three regimens, the calculated R ratio was between 2 and 5, without any statistical differences.

CONCLUSIONS

FOLFIRI-based hepatotoxicity has been indirectly defined as a mixed pattern injury in all three regimens evaluated.

Safety, Tolerability, Pharmacokinetics, and Pharmacodynamics of an Orally Active Novel Camptothecin Analog, DRF-1042, in Refractory Cancer Patients in a Phase I Dose Escalation Study

The objective of this study was to characterize the maximum tolerated dose (MTD), dose-limiting toxicities (DLT), pharmacokinetics, and antitumor effects of DRF-1042, a novel camptothecin analog, in refractory solid tumor patients. DRF-1042 was given for 5 consecutive days for 2 weeks, repeated every 3 weeks at 1.5 to 270 mg/m(2). Adverse events were monitored following NCI-CTC. Pharmacokinetics of lactone and total forms were determined using validated high-performance liquid chromatography (HPLC) and noncompartmental methods. Efficacy was evaluated applying World Health Organization (WHO) criteria. The 1st course was used to determine DLT and MTD. Twenty-five patients received 73 courses of therapy. Myelosuppression and diarrhea were DLTs. MTD was 120 mg/m(2)/day. AUC increased approximately linearly with dose. The t(1/2) for lactone and total forms was 9.9 and 29 hours, respectively. AUCs correlated significantly with nadir leucopenia and grade 4 diarrhea. Two complete responses (CRs) and 2 partial responses (PRs) were observed. In addition, 4 stable diseases were observed. The recommended phase II dose is 80 mg/m(2)/day.

Review role of topotecan in gynaecological cancers: current indications and perspectives

BACKGROUND

Ovarian cancer is the fourth cause of death from gynaecological cancer and cervical cancer is the first in women <45 years old in developing countries. The aim of this article is to review the role of topotecan (Hycamtin), a semi-synthetic alkaloid derivative of camptothecin, in ovarian and cervical cancer in monotherapy and in combination.

METHODS

This article reviews the mechanism of action, pharmacokinetics, toxicity and efficacy of topotecan. The paper also reports the principal phases II and III studies of topotecan in advanced or recurrent ovarian and cervical cancer.

RESULTS

Topotecan (Hycamtin), currently indicated for the treatment of relapsed ovarian cancer, has demonstrated activity both in platinum-sensitive and in platinum-resistant disease. The combination cisplatin-topotecan for the treatment of advanced and recurrent cervical cancer has demonstrated a clinical benefit in terms of response rate, overall survival and progression free survival. Haematological toxicity of topotecan also is easy to manage and not cumulative, especially with the weekly scheduled recently introduced in clinical practice.

CONCLUSION

Topotecan (Hycamtin) will continue to play a role in the treatment of advanced ovarian and cervical cancer, in monotherapy or in combination with other cytotoxic agents.

Cancer chemotherapy I: hepatocellular injury

Although hepatotoxicity is a frequent concern with all medications, chemotherapeutic agents are more often implicated in causing liver damage than most other drug classes. In many instances, these reactions are considered dose related because cytotoxic therapy directed at rapidly growing cancer cells may readily impact hepatocytes even though they are dividing more slowly. Because the stakes (remission of cancer) are high, so are the risks that the oncologist and the patient are willing to assume. The dose of many chemotherapeutic agents is limited by the toxic effects on the lungs, bone marrow, kidneys, and gastrointestinal system, including the liver. An awareness of the toxic potential of each chemotherapeutic agent is necessary before initiation of new oncologic treatments.

A pharmacoproteomics study of the cancer cell line EKVX using capillary-LC/MS/MS

The chemotherapeutic agent camptothecin, 10-OH (CPT,10-OH), was shown to act synergistically with the epithelial growth factor receptor (EGFR) inhibitor (AG1478) against several transformed cell lines. To study the cellular response to these drugs, the non-small-cell lung carcinoma cell line, EKVX, was treated with these compounds either alone or in combination. We performed a proteomic analysis using capillary-HPLC coupled with electrospray ion trap mass spectrometry (capillary-LC-ESI/MS) of a tryptic digest to obtain a global protein profile of the EKVX cell line and identify changes in protein expression. The combination of AG1478 and CPT,10-OH showed synergistic cytotoxicity and also changed the expression of multiple proteins, while individual treatments showed a lesser effect on protein expression. Thus, the synergistic action of AG1478 and CPT,10-OH was reflected in altered protein profiles, showing that a proteomic analysis can serve to evaluate chemotherapeutic agents and their combinations.

A prospective study of isolated human hepatocyte function following liver resection for colorectal liver metastases: the effects of prior exposure to chemotherapy

BACKGROUND/AIMS

Chemotherapy is increasingly used prior to resection of colorectal liver metastases, yet few studies have addressed its effect on the viability and function of hepatocytes. This study evaluated the effect of pre-operative chemotherapy on human hepatocytes.

METHODS

Studies were carried out on isolated hepatocytes from 47 patients undergoing hepatectomy for colorectal metastases. The function of drug metabolising enzymes in hepatocytes was assessed in vitro, as well as hepatocyte integrity and culture longevity. These results were compared between patients undergoing no pre-operative chemotherapy (N = 8), 5 fluorouracil (5FU) post-bowel resection (N = 20), and neo-adjuvant 5FU alone (N = 7) or in a combination with oxaliplatin (N = 12).

RESULTS

Average cell viability at isolation determined by trypan blue dye exclusion was 71% with no significant difference between the no chemotherapy or pre-resection chemotherapy groups. There was no significant difference in LDH leakage and cellular ATP content over a 96-h time course between the patient treatment groups. The function of cytochromes P450 (CYP1A2, CYP2A6, CYP2C9, CYP2D6, CYP2E1, CYP3A4) and phase II enzymes (UDP-glucuronosyltransferase and sulphotransferase) was not adversely affected by pre-operative chemotherapy.

CONCLUSIONS

Pre-resection chemotherapy does not impair the function or culture integrity of hepatocytes isolated at the time of liver resection.

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.

Preclinical and phase I study of oxaliplatin and topotecan in combination in human cancer

BACKGROUND

DNA damage caused by platinum agents is frequently followed by induction of topoisomerase I, providing a rationale for use of platinum-based compounds with topoisomerase I inhibitors.

MATERIALS AND METHODS

We studied the effect of a sequential schedule of oxaliplatin on day I and topotecan on days 2-5, in human colon and ovarian cancer cells in vitro, in nude mice bearing human cancer xenografts and finally in cancer patients in a phase I trial.

RESULTS

We demonstrated a supra-additive effect of this combination on inhibition of colony formation and induction of apoptosis in vitro. We then demonstrated that the two agents in combination markedly inhibit tumor growth in nude mice. We translated these results into a clinical setting, conducting a phase I study in cancer patients with oxaliplatin 85 mg/m2 on day 1 and topotecan at doses escalating from 0.5 to 1.5 mg/m2 on days 2-5. Sixty cycles of treatment were administered to 18 patients affected prevalently by ovarian and colorectal cancer. Combination with topotecan 1.5 mg/m2 caused a dose-limiting toxicity. Therefore the maximum tolerated dose of topotecan was 1.25 mg/m2, at which six patients experienced a mild hematological and gastrointestinal toxicity. We also obtained evidence of clinical activity, particularly in ovarian cancer.

CONCLUSIONS

Our results provide a solid biological and clinical rationale for a phase II trial at the recommended doses of oxaliplatin 85 mg/m2 and topotecan 1.25 mg/m2, possibly in ovarian cancer patients.

Quantitative structure-antitumor activity relationships of camptothecin analogues: cluster analysis and genetic algorithm-based studies

Topoisomerase 1 (top1) inhibitors are proving useful against a range of refractory tumors, and there is considerable interest in the development of additional top1 agents. Despite crystallographic studies, the binding site and ligand properties that lead to activity are poorly understood. Here we report a unique approach to quantitative structure-activity relationship (QSAR) analysis based on the National Cancer Institute's (NCI) drug databases. In 1990, the NCI established a drug discovery program in which compounds are tested for their ability to inhibit the growth of 60 different human cancer cell lines in culture. More than 70 000 compounds have been screened, and patterns of activity against the 60 cell lines have been found to encode rich information on mechanisms of drug action and drug resistance. Here, we use hierarchical clustering to define antitumor activity patterns in a data set of 167 tested camptothecins (CPTs) in the NCI drug database. The average pairwise Pearson correlation coefficient between activity patterns for the CPT set was 0.70. Coherence between chemical structures and their activity patterns was observed. QSAR studies were carried out using the mean 50% growth inhibitory concentrations (GI(50)) for 60 cell lines as the dependent variables. Different statistical methods, including stepwise linear regression, principal component regression (PCR), partial least-squares regression (PLS), and fully cross-validated genetic function approximation (GFA) were applied to construct quantitative structure-antitumor relationship models. For our data set, the GFA method performed better in terms of correlation coefficients and cross-validation analysis. A number of molecular descriptors were identified as being correlated with antitumor activity. Included were partial atomic charges and three interatomic distances that define the relative spatial dispositions of three significant atoms (the hydroxyl hydrogen of the E-ring, the lactone carbonyl oxygen of the E-ring, and the carbonyl oxygen of the D-ring). The cross-validated r(2) for the final GFA model was 0.783, indicating a predictive QSAR model.

A phase I-II trial of topotecan and gemcitabine in patients with previously treated, advanced non-small cell lung cancer (LOA-3)

The purposes of this study were to determine the maximum tolerated dose (MTD), dose-limiting toxicity (DLT), toxicity profile, and antitumor activity of topotecan (TOP) and gemcitabine (GEM) combination therapy when administered to patients with previously treated, advanced, non-small cell lung cancer. Both compounds were administered intravenously over 30 min, with TOP on days 1-5 and GEM on days 1 and 5 only. Nineteen patients were treated with 75 courses at three dose levels. The MTD was 0.75 and 400 mg/m2 for TOP and GEM, respectively, with thrombocytopenia and neutropenia as the DLTs. Partial responses were achieved in 3 of 17 patients (18%) with measurable disease. Six patients (32%) had disease stabilization for at least four courses of treatment. The median survival was 10 months from the initiation of TOP and GEM. This combination was relatively well tolerated and exhibited promising antitumor activity in patients with advanced, previously treated, non-small cell lung cancer.

Hepatotoxicity of chemotherapy

After assessment of tumor histology, the next important factor to consider in the selection of a chemotherapy regime is organ function. Patients who are to receive chemotherapy require careful assessment of liver function prior to treatment to determine which drugs may not be appropriate, and which drug doses should be modified. Following therapy abnormalities of liver function tests may be due to the therapy rather than to progressive disease, and this distinction is of critical importance. Furthermore, not all abnormalities in liver function are due to the tumor or its treatment, and other processes, such as hepatitis, must be kept in mind. This article reviews the hepatic toxicity of chemotherapeutic agents, and suggests dose modifications based upon liver function abnormalities. Emphasis is placed on agents known to be hepatotoxic, and those agents with hepatic metabolism.

Selective drug resistant human osteosarcoma cell lines

Chemotherapy in combination with surgery has been shown to be effective for the control of osteosarcoma. Development of resistance to chemotherapeutic agents is a recurring clinical problem. To investigate this phenomena, human osteosarcoma cells, TE-85, were exposed to increasing doses of Taxol or Taxotere during a 9-month period. Highly resistant subclones (TE-85TXL; TE-85TXR, respectively) were developed. Chemosensitivities are presented for TE-85 cell line and these new lines to Taxol, Taxotere, doxorubicin, cisplatin, and topotecan. Drug concentrations that inhibited cell growth by 50% compared with untreated cells were determined. The TE-85TXL cells showed resistance greater than 1,000-fold to Taxol and Taxotere and 60-fold to doxorubicin. The TE-85TXR cells showed resistance greater than 1,000-fold to Taxol, 800-fold to Taxotere, and 90-fold to doxorubicin. There was little cross resistance to topotecan and enhanced sensitivity to cisplatin. The role of P-170 glycoprotein in Taxol and Taxotere resistance was explored. Coincubation with verapamil, to block the actions of P-170 glycoprotein, partly reversed resistance to Taxol, Taxotere, and doxorubicin in both cell lines. Anti-P-170 glycoprotein antibodies revealed positive staining in TE-85TXL and TE-85TXR cell lines. Flow cytometry revealed reduced accumulation of doxorubicin in resistant cells. These data indicate that a human osteosarcoma cell line will develop resistance to Taxol and Taxotere, which is mediated in part by the P-170 glycoprotein.

A phase II study of 9-aminocamptothecin in patients with refractory breast cancer

We evaluated 9-aminocamptothecin (9-AC) in patients with metastatic or locally recurrent breast cancer who were no longer responsive to standard therapy. Patients were treated with 9-AC with a 72-hr continuous infusion given at a dose of 45 micrograms/m2/hr every 2 weeks. Granulocyte colony-stimulating factor 5 micrograms/kg was given subcutaneously for 7-10 days after completion of the treatment. Eighteen patients were treated, with all patients assessable for toxicity and 15 patients assessable for response. There were two partial responses seen in the 15 patients lasting 3.5 and 5 months, respectively. The major toxicity seen was myelosuppression, with 12 patients having grade 3 or greater granulocytopenia with four episodes of significant infectious complications. In addition, significant thrombocytopenia was seen in 14 patients. The other complications commonly seen were nausea and vomiting and alopecia. 9-AC given as a 3-day continuous infusion has limited activity in previously treated metastatic and locally recurrent breast cancer.

Tumor lysis syndrome and acute renal failure after treatment of non-small-cell lung carcinoma with combination irinotecan and cisplatin

Tumor lysis syndrome, characterized by multiple metabolic abnormalities resulting from abrupt tumor cell death and release of intracellular constituents and metabolites, is most commonly associated with the treatment of highly chemotherapy-sensitive lymphoid and leukemic neoplasms. The authors report a case of tumor lysis syndrome accompanied by acute renal failure that occurred in a patient with stage IV non-small-cell lung cancer who was treated with topoisomerase I inhibitor, irinotecan, and cisplatin. Consistent with the rapid tumor lysis, an objective, marked, early clinical response was observed. Attention to adequate hydration, electrolytes, and renal function should be given to outpatients with non-small-cell lung cancer who receive newer chemotherapeutic agents that have greater efficacy toward this group of tumors.

Topoisomerase I interactive drugs in children with cancer

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

Cerebrospinal fluid pharmacokinetics and penetration of continuous infusion topotecan in children with central nervous system tumors

The purpose of this study was to describe the cerebrospinal fluid (CSF) penetration of topotecan in humans, to generate a pharmacokinetic model to simultaneously describe topotecan lactone and total concentrations in the plasma and CSF, and to characterize the CSF and plasma pharmacokinetics of topotecan administered as a continuous infusion (CI). Plasma and CSF samples were collected from 17 patients receiving 5.5 or 7.5 mg/m2 per day as a 24-h CI (5 patients, 7 courses), or 0.5 to 1.25 mg/m2 per day as a 72-h CI (12 patients, 12 courses). CSF samples were obtained from either a ventricular reservoir (VR) or a lumbar puncture (LP). Topotecan lactone and total (lactone plus hydroxy acid) concentrations were determined by HPLC and fluorescence detection. Using MAP-Bayesian modelling, a three-compartment model was fitted simultaneously to topotecan lactone and total concentrations in the plasma and CSF. The penetration of topotecan into the CSF was determined from the ratio of the CSF to the plasma area under the concentration-time curve. The median CSF ventricular lactone concentrations, obtained prior to the end of infusion (EOI), were 0.86, 1.4, 0.73, 5.3, and 4.6 ng/ml for patients receiving 0.5, 1.0, 1.25, 5.5, and 7.5 mg/m2 per day, respectively. EOI CSF lumbar lactone concentrations measured in three patients were 0.44, 1.1, and 1.7 ng/ml for topotecan doses of 1.0, 5.5, and 7.5 mg/m2 per day, respectively. In two patients receiving 1.25 mg/m2 per day, EOI CSF concentrations were obtained simultaneously from a VR and LP; the lumbar lactone concentrations were 30% and 49% lower than the ventricular concentrations. During a 24-h and a 72-h CI, the median CSF penetration of topotecan lactone was 0.29 (range 0.10 to 0.59) and 0.42 (range 0.11 to 0.86), respectively. A three-compartment model adequately described topotecan lactone and total concentrations in the plasma and CSF. Topotecan was therefore found to significantly penetrate into the CSF in humans. The pharmacokinetic model presented may be useful in the design of clinical studies of topotecan to treat CNS tumors.

Topoisomerase I and II activity in human breast, cervix, lung and colon cancer

The identification of human DNA topoisomerases as cellular targets for active anti-cancer drugs has stimulated further interest in topoisomerase function in tumour biology. Topoisomerase I and II catalytic activity is detectable in many normal and malignant tissues. However, little is known about the expression of topoisomerases in most human solid tumours. The present study evaluated topoisomerase I and II activity in biopsy samples from 86 patients with breast, lung, cervix or colon cancers. Significant intra- and inter-tumour variation in topoisomerase expression was observed. Topoisomerase I activity was relatively high in cervix and colon tumours in comparison to lung and breast cancers. Topoisomerase II activity was high in cervix, colon and lung cancers relative to breast cancer. Topoisomerase I and II activity co-segregated in individual colon tumour samples, but no correlation was observed in cervix, lung or breast tumours. The large heterogeneity in both topoisomerase I and II activity within a tumour type suggests a mechanism for variable response to topoisomerase-directed therapy. The differences in activity between tumour groups suggest that the potential efficacy of inhibitors of topoisomerase I in colon and cervical tumours may be greater than in lung and breast tumours. Future in vivo evaluation is required to establish the clinical relevance of the observed heterogeneity in topoisomerase activity.