Phase I and pharmacologic study of oral (PEG-1000) 9-aminocamptothecin in adult patients with solid tumors

Antitumor efficacy of colon-specific HPMA copolymer/9-aminocamptothecin conjugates in mice bearing human-colon carcinoma xenografts

The antitumor activity of a colon-specific N-(2-hydroxypropyl)methacrylamide (HPMA) copolymer - 9-aminocamptothecin (9-AC) conjugate (P-9-AC) was assessed in orthotopic and subcutaneous animal (HT29 xenograft) tumor models. P-9-AC treatment of mice bearing orthotopic colon tumors, with a dose of 3 mg/kg of 9-AC equivalent every other day for 6 weeks, resulted in regression of tumors in 9 of 10 mice. A lower dose of P-9-AC (1.25 mg/kg of 9-AC equivalent) every other day for 8 weeks inhibited subcutaneous tumor growth in all mice. No liver metastases were observed. Colon-specific release of 9-AC from polymer conjugates enhanced antitumor activity and minimized the systemic toxicity.

Biodistribution and pharmacokinetics of colon-specific HPMA copolymer--9-aminocamptothecin conjugate in mice

A water soluble N-(2-hydroxypropyl)methacrylamide (HPMA) copolymer-9-aminocamptothecin (9-AC) conjugate was designed for oral colon-specific drug delivery in the treatment of colon cancer. Comparative studies between the polymer conjugate and free drug have been performed to assess their biodistribution and pharmacokinetics in mice. After oral administration of equal doses of the polymer conjugate or free 9-AC, the drug concentrations in major organs at fixed time points were determined using an HPLC-fluorescence assay. Only 2+/-1% of 9-AC released from the polymer conjugate was detected in the small intestine (SI), and the mean peak concentration of free 9-AC was 45-fold higher than that from released drug. Colon-specific release of 9-AC produced high local concentrations. The mean peak concentration of released 9-AC in cecal contents, feces, cecal tissue, and colon tissue were, respectively, 3.2-fold, 3.5-fold, 2.2-fold and 1.6-fold higher than that using free 9-AC. In plasma, the high and sharp drug concentration profile from free drug was in contrast to the relatively low and flat pharmacokinetic profile obtained from drug released from the HPMA copolymer. There was no significant difference between released and free drug for the area under the concentration-time curve (AUC) and bioavailability values. As a consequence of the colon-specific release of unmodified 9-AC from the polymer conjugate, antitumor efficacy can be anticipated to be enhanced due to prolonged colon tumor exposure to higher and more localized drug concentrations.

Phase I trial of continuous infusion 9-aminocamptothecin in patients with advanced solid tumors: 21-day infusion is an active well-tolerated regimen

This study's objectives were to determine the maximum tolerated dose (MTD) of 9-aminocamptothecin (9-AC), given as a prolonged continuous infusion (CI) for 7-21 days, when formulated in dimethylacetamide/polyethylene glycol 400 (DMA) and then later as a colloidal dispersion (CD), and to determine the steady-state pharmacokinetics of 9-AC. Patients with solid tumors refractory to standard therapy were enrolled on this study. Total dose/cycle of 9-AC/DMA was initially escalated by duration (7-21 days), while keeping the dose rate constant at 6.2 microg/m/h (1.04-3.12 mg/m/4-week cycle). Then, the dose rate was escalated from 6.2 to 21.1 microg/m/h (3.12-10.6 mg/m/4-week cycle) while keeping the infusion duration constant at 21 days. CD formulation was escalated from 14.1 to 25 microg/m/h (7.11-12.60 mg/m/4-week cycle) while keeping the infusion duration constant at 21 days and then escalated from 28.1 to 37.5 microg/m/h (9.44-12.60 mg/m/3-week cycle) while keeping the infusion duration constant at 14 days. Sixty-two patients were evaluable for toxicity; 61 received prior chemotherapy (median 3 regimens/patient). No consistent dose-limiting toxicity (DLT) was encountered with the DMA formulation until dose level 10.60 mg/m/cycle, when two patients experienced DLTs. With the 21-day CD formulation, the MTD was 12.60 mg/m/cycle with three DLTs out of five patients. When 9-AC was given on the 14-day schedule, DLT was seen at 9.44, 11.20 and 12.60 mg/m/cycle, with consistent DLT at the two highest dose levels. All DLTs for both formulations were grade 4 hematologic toxicities (neutropenia and/or thrombocytopenia), while non-hematologic toxicities were relatively mild (including gastrointestinal toxicities and fatigue). One patient with ovarian cancer had a complete response and three had partial responses (PRs). One patient each with non-Hodgkin's lymphoma and cancer of unknown primary had a PR. Pharmacokinetic studies of both formulations of 9-AC revealed a linear relationship between increasing plasma 9-AC lactone concentration and dose. The median plasma 9-AC lactone concentration for 9-AC/CD was approximately twice that achieved by 9-AC/DMA for the same dose level. Both 9-AC formulations, given as a 21-day CI, were well tolerated with dose-limiting myelosupression at the MTD. This dose intensity exceeds that of other 9-AC phase I/II schedules. The recommended phase II dose (RPTD) is 9.42 mg/m/4-week cycle, given as a 21-day infusion. The 14-day schedule of 9-AC/CD was equally myelosuppressive with the RPTD of 9.44 mg/m/3-week cycle, although two heavily pre-treated patients (one with pelvic radiotherapy) could not tolerate this dose. Objective responses were observed in six out of 57 heavily pre-treated patients, most of which had ovarian cancer.

Alternative administration of camptothecin analogues

In order to improve the therapeutic index of camptothecin (CPT) analogues, alternative administration of CPT analogues is being evaluated. Topotecan, irinotecan, rubitecan, lurtotecan and 9-aminocamptothecin have been administered orally with response rates equivalent to that seen after intravenous administration, where applicable. Oral availability and administration of some of the newer CPT analogues, including diflomotecan (BN80915) and grimatecan (ST1481), have also shown promising results. Aerosolisation of liposomal 9-nitrocamptothecin has been studied in patients with advanced malignancies involving the lung, demonstrating systemic antitumour activity. Intrathecal administration of topotecan has been studied in children with refractory neoplastic meningitis. It is well tolerated and associated with some antitumour activity. Intraperitoneal administration of topotecan as consolidation therapy in patients with ovarian cancer has shown promising results. Transdermal administration of rubitecan has been studied in mice. So far, no CPT has been approved for an alternative route of administration.

Phase I and pharmacokinetic study of XR11576, an oral topoisomerase I and II inhibitor, administered on days 1-5 of a 3-weekly cycle in patients with advanced solid tumours

XR11576 is an oral topoisomerase I and II inhibitor. The objectives of this phase I study were to assess the dose-limiting toxicities (DLTs), to determine the maximum tolerated dose (MTD) and to describe the pharmacokinetics (PKs) of XR11576 when administered orally on days 1–5 every 3 weeks to patients with advanced solid tumours. Patients were treated with escalating doses of XR11576 at doses ranging from 30 to 180 mg day⁻¹. For PK analysis, plasma sampling was performed during the first and second courses of treatment and XR11576 concentrations were assayed using a validated high-performance liquid chromatographic assay with mass spectrometric detection. In all, 21 patients received a total of 47 courses. The MTD was reached at 180 mg day⁻¹, with diarrhoea and fatigue as DLT. Nausea and vomiting, although not qualifying for DLT, was ubiquitous. Only in combination with an extensive prophylactic antiemetic regimen consisting of a combination of both dexamethasone and a 5HT3 antagonist was treatment with XR11576 at 120 mg day⁻¹ tolerable. The systemic exposure of XR11576 increased more than proportionally with increasing dose, with a large interpatient variability. No objective responses were seen; four patients experienced stable disease for periods of 12–30 weeks. In this study, the DLTs of XR11576 were diarrhoea and fatigue. The recommended dose for phase II studies of XR11576 is 120 mg administered orally, on days 1–5 every 21 days. Alternative regimens are currently being explored.

Topoisomerase I Inhibitors in the Treatment of Gastrointestinal Cancer: From Intravenous to Oral Administration

This article reviews the current status of the topoisomerase I (top I) inhibitors in the treatment of gastrointestinal (GI) malignancies. We focus on oral drug administration, the mode of administration that is generally preferred by patients with cancer. However, the great majority of the studies have been performed with intravenous (I.V.) administration. The most extensively investigated GI malignancy in phase I/II studies is colorectal cancer (CRC), for which I.V. irinotecan is currently approved in the United States and Europe. We discuss the activity and efficacy of irinotecan as a single agent in CRC and in combination regimens. Also, results obtained with monotherapy and in combination treatment in other GI malignancies such as esophageal, gastric, and pancreatic cancer are discussed. Few phase I studies have been performed with oral irinotecan and its clinical activity has not yet been fully determined. Several top I inhibitors are discussed, including topotecan, 9-aminocamptothecin, rubitecan, exatecan, and lurtotecan. None of these agents, given orally or intravenously, have shown activity in CRC similar to that of I.V. irinotecan. However, several agents show promising results in other GI malignancies, eg, rubitecan and exatecan in pancreatic cancer. A complicating factor in the oral administration of the top I inhibitors is the often encountered low and variable oral bioavailability. This can partly be explained by the high affinity for the drug efflux pumps BCRP (ABCG2) and P-glycoprotein, which are highly expressed in the epithelial apical membrane of the GI tract. A novel approach to improve the oral bioavailability of the top I inhibitors by temporary blockade of the drug transporter BCRP is described.

Nitro and amino substitution within the A-ring of 5H-8,9-dimethoxy-5-(2-N,N-dimethylaminoethyl)dibenzo[c,h][1,6]naphthyridin-6-ones: influence on topoisomerase I-targeting activity and cytotoxicity

Recently, 5H-8,9-dimethoxy-5-(2-N,N-dimethylaminoethyl)-2,3-methylenedioxydibenzo[c,h][1,6]naphthyridin-6-one, 1, was identified as a TOP1-targeting agent with pronounced antitumor activity. In the present study, the effect on activity of substituting a single nitro or amino group in the A-ring in lieu of the methylenedioxy moiety of 1 was evaluated. The presence of either a nitro or amino substituent at the 4-position had a pronounced adverse affect on both TOP1-targeting activity and cytotoxicity. To a lesser extent, derivatives with a nitro or amino substituent at the 1-position were also less active than 1. Replacement of the methylenedioxy moiety of 1 with either a nitro or amino substituent at either the 2- and 3-position did result in analogues with potent TOP1-targeting activity and cytotoxicity.

Oral topotecan for refractory and relapsed neuroblastoma: a retrospective analysis

PURPOSE

Among patients with multiply relapsed neuroblastoma refractory to conventional chemotherapy, oral topotecan has often been used for palliation. Although toxicity was generally thought to be mild, the efficacy of such an approach remains unproven.

METHODS

The authors retrospectively analyzed patients with multiply relapsed or refractory neuroblastoma who were treated with oral topotecan for palliation. Each course was generally 1 mg/m2/d in two divided doses, for 21 consecutive days, repeated after a 1-week rest in patients without symptoms of progressive disease. Disease status was assessed by radiographic studies, urine catecholamine levels, and multiple bone marrow aspirations and biopsies.

RESULTS

Twenty patients between the ages of 3 and 34 (median 13 years) received 1 (n = 7), 2 (n = 3), 3 (n = 4), 4 (n = 2), 6 (n = 2), and 12 courses (n = 2). Prior treatments included multiple cycles of high-dose alkylator-based chemotherapy (n = 20), high-dose intravenous topotecan (n = 8), myeloablative chemotherapy or radioimmunotherapy (n = 10), or experimental biologic agents (n = 16). Anti-neuroblastoma effects were seen in five patients lasting 6 to 12 months; two additional patients remained stable for 4 months. Thirteen patients had progressive disease (11 after one or two cycles). Toxicity included diarrhea (n = 12) requiring a dose adjustment in three patients and discontinuation of the drug in a fourth, and myelosuppression (n = 11) requiring transfusion and/or granulocyte-colony stimulating factor support.

CONCLUSIONS

Oral topotecan therapy has antitumor activity in a small percentage of patients with relapsed or refractory neuroblastoma. Toxicities, including diarrhea and myelosuppression, may necessitate a dose adjustment in this patient population. Low-dose oral topotecan may have utility in the treatment of neuroblastoma.

The camptothecins

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

Oral chemotherapy in colorectal cancer treatment: review of the literature

Recent advances in anticancer treatment have focused on the development of oral anticancer agents with the intention of improving the patients' quality of life as well as providing therapeutic alternatives to intravenous chemotherapy. Until agents such as oxaliplatin and irinotecan became available, the treatment of colorectal cancer, one the most common cancers diagnosed in industralized countries, was mainly based on 5-fluorouracil modulation. The overwhelming majority of these new drugs are pyrimidine analogues intended to replace intravenous treatment or to make the therapy more acceptable to the patients. In this article, the use of oral chemotherapy, alone or in combination with radiotherapy, in colorectal cancer is reviewed and updated. The rationale for using oral compounds is discussed and newer agents, such as oral camptothecin analogues and antiangiogenic agents, are presented with the results of their clinical and preclinical developments.

Role of body surface area in dosing of investigational anticancer agents in adults, 1991-2001

The prescribed dose of anticancer agents is most commonly calculated using body surface area as the only independent variable, and it has been shown that this approach still results in large interpatient variability in drug exposure. Here, we retrospectively assessed the pharmacokinetics of 33 investigational agents tested in phase I trials from 1991 through 2001, as a function of body surface area in 1650 adult cancer patients. Twelve of the drugs were administered orally, 19 were administered intravenously, and two were administered by both routes. Body surface area-based dosing was statistically significantly associated with a reduction in interpatient variability in drug clearance for only five of the 33 agents: docosahexaenoic acid (DHA)-paclitaxel, 5-fluorouracil/eniluracil, paclitaxel, temozolomide, and troxacitabine. These results do not support the use of body surface area in dose calculations and suggest that alternate dosing strategies should be evaluated. We conclude that body surface area should not be used to determine starting doses of investigational agents in future phase I studies.

Synthesis and characterization of a catalytic antibody-HPMA copolymer-Conjugate as a tool for tumor selective prodrug activation

Selective chemotherapy remains a key issue for successful treatment in cancer therapy. The use of targeting approaches like the enhanced permeability and retention (EPR) effect of macromolecules, is consequently needed. Here, we report the preparation of a novel catalytic antibody-polymer conjugate for selective prodrug activation. HPMA copolymer was conjugated to catalytic antibody 38C2 through an amide bond formation between epsilon-amino group of lysine residue from the antibody molecule and a p-nitrophenyl ester of the polymer. The conjugate was purified over a size exclusion column using FPLC. In the isolated fraction, one or two molecules of polymer were conjugated to one molecule of antibody based on gel analysis. The resulting conjugate retained most of its catalytic activity (75-81%) in comparison to the free antibody. The activity was monitored with a fluorogenic substrate and a prodrug activation assay using HPLC. Furthermore, the conjugate was evaluated in vitro for its ability to activate an etoposide prodrug using two different cancer cell lines. Cells growth inhibition using the prodrug and the conjugate was almost identical to inhibition by the free antibody and the prodrug. For the first time, a catalytic antibody was conjugated to a passive targeting moiety while retaining its catalytic ability to activate a prodrug. The conjugate described in this work can be used for selective activation of prodrug in the PDEPT (polymer directed enzyme prodrug therapy) approach by replacing the enzyme component with catalytic antibody 38C2.

Phase II trial of 9-aminocamptothecin as a 72-h infusion in cutaneous T-cell lymphoma

PURPOSE

To evaluate the role of 9-aminocamptothecin (9-AC), a synthetic camptothecin analog, in advanced cutaneous T-cell lymphoma (CTCL).

METHODS

Eligible patients had stage IIB-IV CTCL. 9-AC was infused over 72 h at a dose of 1,100 microg/m2 per day (approximately 46 microg/m2/h) every 2 weeks, with granulocyte-colony stimulating factor (G-CSF) support.

RESULTS

Twelve patients received a total of 30 cycles of 9-AC. Nine patients had stage IV disease, 5 patients had circulating Sezary cells, and 2 patients had evidence of tranformation to a large cell lymphoma. Most of the patients were heavily pretreated: 10 had received prior chemotherapy (83%), 5 of whom had received 2 or more prior regimens, including a patient who had received high-dose chemotherapy, and 7 had previously received total-skin electron beam therapy. The study was prematurely terminated due to substantial toxicity. Six patients (50%) developed an indwelling central venous catheter-related infection, 5 during a period of neutropenia. Three patients died due to sepsis 4-8 weeks after their last 9-AC treatment. Two of these patients had a previous history of bacterial sepsis. Four patients (33%) developed grade IV thrombocytopenia. Two partial responses were observed (response rate 17%), but the duration of response was brief, 4-8 weeks.

CONCLUSION

9-AC at this schedule and route of administration had activity but resulted in an unacceptable rate of complicated neutropenia and septic deaths in heavily pretreated patients with advanced CTCL who are susceptible to catheter-related infections.

Intraperitoneal topoisomerase-I inhibitors. Preliminary findings with 9-aminocamptothecin

The i.p. administration of topoisomerase I (Topo I) inhibitors has a pharmacologic advantage over intravenous application, including preservation of the biologically active lactone form. In our ongoing study, patients have received 9-amino-20(S)-camptothecin (9-AC) i.p. on days 1, 3, 5, 8, 10, and 12, repeated every 4 weeks. The daily dose has been escalated to level IV of 1.5 mg/m2 (9.0 mg/m2 per course), median of 3 cycles, range 1-4, with a reversible Grade 3 neutropenia in one patient. Responses included one CR (resolution of a pleural effusion), two patients without progressive disease (PD), two not evaluable, and two patients too early for evaluation. The area under the curve (AUC)i.p./AUCpl ratio (pharmacologic advantage) ranged from 7.6 to 16.5 on average, and, using nonlinear modeling, the pharmacologic decay data were fit to one- or two-compartmental models. Overall, a 9-AC i.p. application is well tolerated and anticipated to be an active regimen against i.p. malignancies, particularly those known to be sensitive to systemic Topo-I inhibitors.

The clinical development of 9-aminocamptothecin

9-Aminocamptothecin (9-AC) is a topoisomerase I-targeting agent first synthesized by Wani and Wall in 1986. Because of its potent in vitro effects and promising preclinical activity in colorectal cancer animal models, it was designated a high-priority compound for further drug development by the NCI. In 1993, 9-AC first entered clinical trials as a 72-hour intravenous (i.v.) infusion. Predictable myelosuppression was the major dose-limiting toxicity, and pharmacokinetic studies showed a relatively short plasma half-life and unstable lactone ring. Unfortunately, phase II studies using this schedule showed minimal or no activity in tumors such as colorectal and lung cancer. Modest activity was observed in ovarian cancer and in refractory lymphomas. Efforts to improve systemic drug exposure by utilizing alternative schedules of administration of 9-AC such as prolonged, continuous intravenous infusions have also been tested. However, phase II studies of 120-hour weekly infusions of 9-AC have not shown improved activity against solid tumors such as colorectal cancer. More recently, a daily times 5 days i.v. administration schedule has been tested. Currently, further development of intravenously administered 9-AC for the treatment of colorectal cancer is not promising. Thus, topotecan and irinotecan remain the only two successfully developed topoisomerase I-targeting drugs in the United States. This experience with 9-AC raises important questions regarding how to best select new topoisomerase I-targeting drugs for future clinical development.

Modulation of camptothecin analogs in the treatment of cancer: a review

The topoisomerase I inhibitors reviewed in this paper are all semisynthetic analogs of camptothecin (CPT). Modulation of this intranuclear enzyme translates clinically in to antitumor activity against a broad spectrum of tumors and is therefore the subject of numerous investigations. We present preclinical and clinical data on CPT analogs that are already being used in clinical practice [i.e. topotecan and irinotecan (CPT-11)] or are currently in clinical development (e.g. 9-aminocamptothecin, 9-nitrocamptotecin, lurtotecan, DX 8951f and BN 80915), as well as drugs that are still only developed in a preclinical setting (silatecans, polymer-bound derivates). A variety of different strategies is being used to modulate the systemic delivery of this class of agents, frequently in order to increase antitumor activity and/or reduce experienced side effects. Three principal approaches are discussed, including: (i) pharmaceutical modulation of formulation vehicles, structural alterations and the search for more water-soluble prodrugs, (ii) modulation of routes of administration and considerations on infusion duration, and (iii) both pharmacodynamic and pharmacokinetic biomodulation.

Oral topoisomerase 1 inhibitors in adult patients: present and future

The renewed interest in topoisomerase 1 inhibitors, based on new insights on the mechanism of action and the development of semi-synthetic derivates of camptothecin with a more favourable toxicity profile, has led to extensive preclinical and clinical research. Significant levels of anti-tumor activity in human tumor xenografts were seen especially with prolonged duration of exposure. Since oral drug delivery is a more convenient method for prolonged drug administration, and preferred by patients, further development of oral formulations seems attractive. Common concerns in the development of oral formulations are their sometimes low oral bioavailability and the frequently large intra- and interpatient variation in systemic exposure. Efforts to improve absorption and minimize intestinal metabolism/efflux of the oral chemotherapeutic agent using new formulas might lead to better bioavailability. Pharmacokinetic and pharmacodynamic evaluations have enabled guidance in recommendations of schedules. Given the interpatient variation in exposure it is interesting to note that flat dosing of topotecan resulted in the same systemic exposure compared with the more complex dosing per body surface area. In order to diminish the interpatient variation in exposure to 9-AC a limited sampling model for oral 9-AC was developed, enabling prediction of the systemic exposure for 9-AC and optimizing treatment for any given patient. Drug sequencing plays a key role in the combination topotecan/cisplatin and might be important for combination with other classes of drugs. Therefore, forthcoming phase 1 trials on combination therapy with oral topoisomerase 1 inhibitors should include studies on sequence dependence and pharmacokinetic analyses to evaluate any mutual interaction.

Phase I and pharmacokinetic study of a daily times 5 short intravenous infusion schedule of 9-aminocamptothecin in a colloidal dispersion formulation in patients with advanced solid tumors

PURPOSE

To determine the maximum-tolerated dose (MTD), dose-limiting toxicities (DLT), and pharmacokinetics of 9-aminocamptothecin (9-AC) in a colloidal dispersion (CD) formulation administered as a 30-minute intravenous (IV) infusion over 5 consecutive days every 3 weeks.

PATIENTS AND METHODS

Patients with solid tumors refractory to standard therapy were entered onto the study. The starting dose was 0.4 mg/m(2)/d. The MTD was assessed on the first cycle and was defined as the dose at which > or = two of three patients or > or = two of six patients experience DLT. Pharmacokinetic measurements were performed on days 1 and 5 of the first cycle and on day 4 of subsequent cycles using high-performance liquid chromatography.

RESULTS

Thirty-one patients received 104+ treatment courses at seven dose levels. The DLT was hematologic. At a dose of 1.3 mg/m(2)/d, three of six patients experienced grade 3 thrombocytopenia. Grade 4 neutropenia that lasted less than 7 days was observed in four patients. At a dose of 1.1 mg/m(2)/d, four of nine patients had grade 4 neutropenia of brief duration, which was not dose limiting. Nonhematologic toxicities were relatively mild and included nausea/vomiting, diarrhea, obstipation, mucositis, fatigue, and alopecia. Maximal plasma concentrations and area under the concentration-time curve (AUC) increased linearly with dose, but interpatient variation was wide. Lactone concentrations exceeded 10 nmol/L, the threshold for activity in preclinical tumor models, at all dose levels. Sigmoidal E(max) models could be fit to the relationship between AUC and the degree of hematologic toxicity. A partial response was observed in small-cell lung cancer.

CONCLUSION

9-AC CD administered as a 30-minute IV infusion daily times 5 every three weeks is safe and feasible. The recommended phase II dose is 1. 1 mg/m(2)/d.