Schedule-dependent topoisomerase II-inhibiting drugs

Medium-dose etoposide, cyclophosphamide and total body irradiation conditioning potentiates anti-leukemia immunity in adults with acute lymphoblastic leukemia without aggravating graft-versus-host disease

Medium-dose etoposide (ETP), cyclophosphamide (CY) and total body irradiation (TBI) is a beneficial conditioning regimen for allogeneic hematopoietic cell transplantation (allo-HCT) in adults with acute lymphoblastic leukemia (ALL), especially with high-risk ALL, as compared with CY and TBI conditioning. ETP may enhance immunogenicity of leukemia-associated antigens through increased expression of major histocompatibility antigen complex class I, leading to cross-priming of T cells by dendritic cells and generating leukemia-specific cytotoxic T cells. Furthermore, ETP can eliminate activated effector T cells, sparing naïve and memory T cells, accompanied with depletion of regulatory T cells. These mechanisms are supposed to lead to inhibit immune escape of leukemia cells and enhance anti-leukemia immunity in addition to direct cytotoxicity of ETP, followed by an efficient eradication of leukemia cells. According to the findings of pharmacokinetics studies, spreading the administration of low-dose ETP may be more efficacious than non-spreading administration, to induce a potent anti-leukemia immunity without aggravating graft-versus-host disease and transplant-related toxicity. In the present review, I discuss the immunological aspects elicited by the addition of medium-dose ETP to the CY/TBI conditioning and the possible positioning of allo-HCT with this conditioning in adults with ALL, considering recent progress in non-HCT treatment including bispecific antibody-based therapy.

Perspectives on the Use of a Medium-Dose Etoposide, Cyclophosphamide, and Total Body Irradiation Conditioning Regimen in Allogeneic Hematopoietic Stem Cell Transplantation: The Japanese Experience from 1993 to Present

The outcome for adults with acute lymphoblastic leukemia (ALL) treated with chemotherapy or autologous hematopoietic stem cell transplantation (HSCT) is poor. Therefore, allogeneic HSCT (allo HSCT) for adults aged less than 50 years with ALL is performed with myeloablative conditioning (MAC) regimens. Among the several MAC regimens, a conditioning regimen of 120 mg/kg (60mg/kg for two days) cyclophosphamide (CY) and 12 gray fractionated (12 gray in six fractions for three days) total body irradiation (TBI) is commonly used, resulting in a long term survival rate of approximately 50% when transplanted at the first complete remission. The addition of 30 mg/kg (15 mg/kg for two days) etoposide (ETP) to the CY/TBI regimen revealed an excellent outcome (a long-term survival rate of approximately 80%) in adults with ALL, showing lower relapse and non-relapse mortality rates. It is preferable to perform allo HSCT with a medium-dose ETP/CY/TBI conditioning regimen at the first complete remission in high-risk ALL patients and at the second complete remission (in addition to the first complete remission) in standard-risk ALL patients. The ETP dose and administration schedule are important factors for reducing the relapse and non-relapse mortality rates, preserving a better outcome. The pharmacological study suggests that the prolonged administration of ETP at a reduced dose is a promising treatment.

Hydrolytically activated etoposide prodrugs inhibit MDR-1 function and eradicate established MDR-1 multidrug-resistant T-cell leukemia

Effective therapy of high-risk leukemia with established cytotoxic drugs may be limited by poor antitumor efficacy, systemic toxicity, and the induction of drug resistance. Here, we provide the first evidence that hydrolytically activated prodrugs may overcome these problems. For this purpose, VP16 was functionally blocked by hydrolytically cleavable carbonate linkers with unique characteristics to generate 2 novel prodrugs of VP16. First, we established a more than 3-log higher efficacy of the 2 prodrugs compared with VP16 on a panel of naturally drug-resistant tumor cell lines. Second, the prodrugs did overcome VP16-induced multidrug resistance-1 gene (MDR-1)-mediated multidrug resistance in vitro in a newly established VP16-resistant T-cell leukemia cell line MOVP-3 by functionally blocking MDR-1-mediated efflux. Third, in vivo studies showed a maximum tolerated dose of ProVP16-II (> 45mg/kg), which was at least 3-fold higher than that of VP16 (15 mg/kg). Finally, tests of ProVP16-II in a multidrug-resistant xenograft model of T-cell leukemia expressing MDR-1 indicated that only the mice treated with this prodrug revealed a complete and long-lasting regression of established, drug-resistant leukemia. In summary, the hydrolytically activated etoposide prodrugs proved effective against multidrug-resistant T-cell leukemia in vitro and in vivo and provide proof of concept for a highly promising new strategy for the treatment of MDR-1 drug-resistant malignancies.

Use of positron emission tomography in pharmacokinetic studies to investigate therapeutic advantage in a phase I study of 120-hour intravenous infusion XR5000

PURPOSE

XR5000 (N-[2-(dimethylamino)ethyl]acridine-4-carboxamide) is a topoisomerase I and II inhibitor. Because the cytotoxicity of XR5000 increases markedly with prolonged exposure, we performed a phase I study of weekly XR5000 by 120-hour continuous infusion over 3 weeks.

PATIENTS AND METHODS

Twenty-four patients with advanced solid cancer were treated at seven dose levels (700 to 4,060 mg/m2/120 hrs) for a total of 67 cycles. Three patients underwent positron emission tomography (PET) studies at the maximum-tolerated dose (MTD) to evaluate normal tissue and tumor carbon-11 radiolabeled XR5000 ([11C]XR5000) pharmacokinetics.

RESULTS

The dose-limiting toxicity was National Cancer Institute Common Toxicity Criteria (version 1) grade 4 chest and abdominal pain affecting the single patient receiving 4,060 mg/m2/120 hours, and the MTD was 3,010 mg/m2/120 hours. Other grade 3-4 toxicities, affecting single patients at the MTD, were myelosuppression (grade 4), raised bilirubin, vomiting, and somnolence (all grade 3). There was one partial response (adenocarcinoma of unknown primary); the remainder had progressive disease. [11C]XR5000 distributed well into the three tumors studied by PET. Tumor uptake (maximum concentration or area under the concentration versus time curve [AUC]) was less than in normal tissue in which the tumors were located. Tumor exposure (AUC; mean +/- SD in m2/mL/sec) increased when [(11)C]XR5000 was administered during an infusion of XR5000 (0.242 +/- 0.4), compared with [11C]XR5000 given alone (0.209 +/- 0.04; P <.05), indicating that tumor drug exposure was not saturated [corrected].

CONCLUSION

The recommended dose for XR5000 in phase II studies is 3,010 mg/m2/120 hours. PET studies with 11C-labeled drug were feasible and demonstrated in vivo distribution into tumors. Saturation of tumor exposure was not reached at the MTD.

A phase I study of sequential intravenous topotecan and etoposide in lung cancer patients

PURPOSE

The topoisomerase I inhibitor topotecan (T) and the topoisomerase II inhibitor etoposide (E) are active drugs in lung cancer. The complementary functions of their targets may suggest benefit from the combined use of these agents but drug scheduling has been shown to play a critical role in preclinical models. To establish the optimal schedule and assess the impact of sequential administration of the combination of T and E, we conducted a dose finding study of sequential intravenous T and E in a four-weekly-schedule in relapsed lung cancer patients.

PATIENTS AND METHODS

The importance of drug sequence was assessed in consecutive patients throughout all dose levels; patients received in the first course either T followed by E (the TE group: T on days 1-3 and E on days 4-6) or E before T (the ET group: F on days 1-3 and Ton days 4-6). The sequence of Tand E was alternated in the successive courses. In this crossover design, each patient served as his own control for analysis of hematological toxicity in which TE sequence was compared to that of the ET sequence. Moreover, hematological toxicity after the first course was compared between the TE and the ET groups. The starting dose was T/E 0.75/75 mg/m2 at dose level 1and dose escalation was planned to T/E 1.00/75 mg/nm2 at dose level 2, T/E 1.00/100 mg/m2 at dose level 3, T/E 1.25/100 mg/m2 at dose level 4 and T/E 1.50/100 mg/m2 at dose level 5. Nineteen patients (small-cell lung cancer 7, non-small-cell lung cancer 11, mesothelioma 1 patient) were included.

RESULTS

The principal toxicity was myelosuppression, primarily neutropenia and thrombocytopenia. At dose level 3 several grade 4 toxicities were observed. DLT (febrile neutropenia) occurred in two patients, one in the TE and one in the ET group and precluded further dose escalation. There was no significant difference in WBC and platelet nadirs during the first course between the TE and the ET group. The influence of the sequence of administration of topotecan and etoposide was calculated by comparing the nadir values of cycles I and II for each patient. For none of the dose levels, a significant sequence-dependent effect could be detected. The MTD was reached at the doses of 100 mg/m2 topotecan and 75 mg/m2 etoposide. No objective responses were seen.

CONCLUSION

Although the combined use of topoisomerase I and II inhibitors is attractive on theoretical grounds, excessive myelosuppression prevents substantial dose escalation.

Simulation tool for schedule-dependent etoposide exposure based on pharmacokinetic findings published in the literature

It is the aim of this study to establish a simulation tool for etoposide (Eto) which can be used to interpret drug monitoring data in clinical practice and to design new schedules for future protocols. As schedule dependency was observed for Eto, knowledge of concentration-time profiles is important. Pharmacokinetic data from children after low-dose i.v. administration of Eto together with data reported in the literature were used to construct the simulation tool. Validation was performed by independently reproducing various published data. Dose linearity of AUC was shown over the whole dose range of 20-2000 mg/m2 reported in the literature and fits the predictions by the simulation tool. There was no difference in clearance between children and adults. Close agreement was found between predicted and reported concentration-time profiles after various administration schedules. However, subgroups with significantly altered pharmacokinetics of Eto, such as patients with renal impairment or concurrent cisplatin chemotherapy, were excluded from the comparisons. In these patients values predicted for a 'regular' patient might be used as a base for possible dose modifications. In summary, a pharmacokinetic model of high predictive value is presented which allows simulations of Eto concentration-time profiles for low- as well as high-dose conditions and various infusion times.

Etoposide and idarubicin in a modified CHOP-like regimen (VICED) for aggressive non-Hodgkin's lymphomas

The superiority of intensive versus standard chemotherapy for aggressive (I: intermediate; H: high grade) NHL is still debated; increased antitumor activity may be counterbalanced by increased toxicity. We have designed a first-line five-drug regimen (vincristine, idarubicin, cyclophosphamide, etoposide and deflazacort), with the aim of potentiating the CHOP protocol without losing tolerability and ease of administration. Seventy-one patients (33% aged > or = 65) entered the study. CR was obtained in 66.7% of patients (I: 74%; H: 56%), PR in 19.7%: overall response rate was 86.4%. Six patients were resistant, two died during treatment. With a median follow up of two years, relapse has occurred in 14 patients (8 I, 6 H). At 3 years, overall survival was projected to be 62.5% (I 73.5%; H 31.4%), disease free survival 66% (I 71%, H 56.3%). No organ toxicity occurred. Myelosuppression was moderate, with a nadir on the 14th day. Febrile episodes occurred in 16% of courses, dose delay in 19% of courses; dose reduction in 3% of patients. No patient required hospitalization. G-CSF was only occasionally used. This regimen has shown a potent antitumor effect with an excellent tolerance, even in elderly patients.

Etoposide combined with interferon alfa-2b: novel exploitation of established etoposide pharmacokinetics and pharmacodynamics

PURPOSE

To construct an efficient pilot study design to determine whether interferon alfa-2b modifies the pharmacokinetics and pharmacodynamics of continuous-infusion etoposide.

PATIENTS AND METHODS

A two-stage randomized 2 X 2 factorial design was used to evaluate interferon alfa-2b at two doses (2 or 10 MU/m2/day SQ for 3 days) and two schedules (interferon alfa-2b administered before or concurrent with 72-hour continuous-infusion etoposide). Etoposide was administered at 75, 100, or 125 mg/m2/day. In lieu of comparing the experimental arms to an etoposide-alone control arm to determine effect of interferon alfa-2b dose and schedule, a novel analytic approach was used. The effect of interferon alfa-2b on etoposide-induced leukopenia was assessed indirectly by comparison of the observed white blood cell (WBC) nadir to the nadir predicted from an established pharmacodynamic model for single agent etoposide.

RESULTS

Based on 29 patients, dose-normalized 24-hour total and estimated free etoposide concentrations did not differ with interferon alfa-2b dose or schedule. Patients treated with interferon alfa-2b before etoposide had, on average a WBC nadir 545 +/- 225 cells microliter lower than that predicted by a pharmacodynamic model for etoposide alone. An optimal nonlinear model for leukopenia was defined by interferon alfa-2b schedule in addition to 24-hour etoposide concentration.

CONCLUSION

A novel study design and statistical analysis provided an efficient preliminary evaluation of the combination of interferon alfa-2b with etoposide in a modest number of patients. Exploitation of a previously validated pharmacodynamic model allowed evaluation of interferon alfa-2b effect and eliminated the need for an etoposide-alone control arm. The pharmacokinetics of continuous-infusion etoposide at doses from 75 to 125 mg/m2/day appear to be unchanged by interferon alfa-2b at the doses and schedules tested and the combination appears to be feasible. We hypothesize that leukopenia may be enhanced when interferon alfa-2b is administered before etoposide, especially at a higher dose of interferon alfa-2b.