Liposomal lurtotecan (NX211): determination of total drug levels in human plasma and urine by reversed-phase high-performance liquid chromatography

Randomized Trial of Two Intravenous Schedules of the Topoisomerase I Inhibitor Liposomal Lurtotecan in Women With Relapsed Epithelial Ovarian Cancer: A Trial of the National Cancer Institute of Canada Clinical Trials Group

Purpose

Liposomal lurtotecan (OSI-211) is a liposomal formulation of the water-soluble topoisomerase I inhibitor lurtotecan (GI147211), which demonstrated superior levels of activity compared with topotecan in preclinical models. We studied two schedules of OSI-211 in a randomized design in relapsed ovarian cancer to identify the more promising of the two schedules for further study.

Patients and Methods

Eligible patients had measurable epithelial ovarian, fallopian, or primary peritoneal cancer that was recurrent after one or two prior regimens of chemotherapy. Patients were randomly assigned to receive either arm A (OSI-211 1.8 mg/m2/d administered by 30-minute intravenous infusion on days 1, 2, and 3 every 3 weeks) or arm B (OSI-211 2.4 mg/m2/d administered by 30-minute intravenous infusion on days 1 and 8 every 3 weeks). The primary outcome measure was objective response, which was confirmed by independent radiologic review, and a pick the winner statistical design was used to identify the schedule most likely to be superior.

Results

Eighty-one patients were randomized between October 2000 and September 2001. The hematologic toxic effects were greater on arm A than on arm B (grade 4 neutropenia, 51% v 22%, respectively), as was febrile neutropenia (26% v 2.4%, respectively). Of the 80 eligible patients, eight patients (10%) had objective responses; six responders (15.4%; 95% CI, 6% to 30%) were in arm A and two responders (4.9%; 95% CI, 1% to 17%) were in arm B.

Conclusion

The OSI-211 daily for 3 days intravenous schedule met the statistical criteria to be declared the winner in terms of objective response. This schedule was also associated with more myelosuppression than the schedule of OSI-211 administered in arm B.

Camptothecins in clinical development

Following the realisation that DNA topoisomerase I is a useful therapeutic target to be exploited for the design of potential inhibitors, topoisomerase I inhibitors now represent an established class of effective agents. In spite of intense efforts in the field, only camptothecins have a clinical relevance. Several options in chemical manipulation of natural camptothecin have been explored to overcome the major drawbacks of the drug, which include water insolubility, lactone instability, reversibility of the drug-target interaction and drug resistance. Several analogues are currently in clinical development, including water soluble camptothecins, lipophilic camptothecins and polymer-bound camptothecins. The therapeutic advantages of novel camptothecins over the two analogues (topotecan and irinotecan) approved for clinical use remain to be defined. This article is an overview of the relevant features of the analogues that are undergoing clinical development.

Phase II study of OSI-211 (liposomal lurtotecan) in patients with metastatic or loco-regional recurrent squamous cell carcinoma of the head and neck. An EORTC New Drug Development Group study

The purpose of this study was to evaluate the activity and safety of OSI-211, the liposomal form of lurtotecan, in patients ineligible for curative surgery or radiotherapy and with metastatic/locoregional recurrent squamous cell carcinoma of the head and neck (SCCHN) and target lesions either within a previously irradiated field ("within") or outside a previously irradiated field ("outside"). OSI-211 was given intravenously over 30 min on days 1 and 8 at 2.4 mg/m2/day, repeated every 21 days (1 cycle). From July 2001 to March 2002, 32 patients from 14 institutions were enrolled in the "within" arm and 18 in the "outside" arm. In the "within" arm, two patients were ineligible because their tumour site was not allowed in the protocol (nasopharynx, skin) and two other patients never started treatment. Of the 46 eligible patients who started treatment, there was one objective response (response rate: 2.2% (95% Confidence Interval (CI): [0-11.5%]). Twelve patients in the "within" arm and 6 in the "outside" arm had stable disease, with a median duration of 18 weeks, 95% CI (12.7-25.7). The median time to progression was 6 weeks (95%CI: [5.9-12.7] weeks). Haematological toxicity was moderate in both arms. The most common haematological toxicity was grade 1-2 anaemia in 79% of patients. Non-haematological toxicity was mild in both arms. The most common grade 3-4 non-haematological toxicity was infection in 8.5% of patients. OSI-211 administered on d1 and d8, every 3 weeks, is well tolerated, but shows only minimal activity in locally advanced/metastatic SCCHN.

Cytotoxic effect of different camptothecin formulations on human colon carcinoma in vitro

Two innovative 20-S-camptothecin (CPT) formulations, previously found suitable to achieve therapeutically relevant CPT concentrations, were assessed for their in vitro cytotoxic potential as compared to an aqueous CPT solution, using the MTT assay. The formulations, cationic CPT-containing liposomes (CPT-Lip), hydroxypropyl-beta-cyclodextrin (HP-beta-CD) complexed CPT (CPT-CD) and a saturated aqueous CPT solution (CPT-Sol), were diluted in culture medium to appropriate CPT concentrations (4.7-300 ng/ml), and incubated with HT-29 and SW-480 human colon carcinoma cell lines. IC50 values were calculated after 48 and 72 h incubation for the HT-29 and SW-480 cell lines, respectively, and were found to be of the same magnitude for all formulations, with only a slight difference (CPT-Sol<CPT-CD<CPT-lip). The cells obtained apoptotic morphology after 36 h incubation with CPT-CD and were demonstrated to be active caspase-3 immuno-positive. Both formulations investigated, CPT-CD and CPT-Lip, showed significant cytotoxicity in vitro relative to CPT-Sol and warrant investigation for future therapeutic application.

Phase I and pharmacokinetic study of a low-clearance, unilamellar liposomal formulation of lurtotecan, a topoisomerase 1 inhibitor, in patients with advanced leukemia

BACKGROUND

OSI-211 is a low-clearance, unilamellar liposomal formulation of a water-soluble camptothecin analogue, lurtotecan. OSI-211 has significant activity in severe combined immunodeficient mouse models of human leukemia.

METHODS

This study was conducted to define the dose-limiting toxicities (DLT) and pharmacokinetics of OSI-211 in patients with refractory myeloid leukemias. Patients with refractory acute myeloid leukemia (AML), myelodysplastic syndrome (MDS), or chronic myelogenous leukemia in blastic phase (CML-BP) were eligible. OSI-211 was given as an intravenous infusion over 30 minutes daily for 3 days. The starting dose was 1.5 mg/m2 per day (4.5 mg/m2 per course). The dose was escalated by 50% until Grade 2 toxicity was observed and then by 30-35% until the DLT was defined. Serial plasma and urine samples were collected, and drug levels were determined by high-performance liquid chromatography with fluorescence detection.

RESULTS

Twenty patients (18 patients [90%] with AML, and 1 patient each [5%] with MDS and CML-BP) were treated. Mucositis and diarrhea were considered to be the DLTs. The maximum tolerated dose was 3.7 mg/m2 per day. Fourteen of 18 evaluable patients (78%) with AML or MDS achieved transient bone marrow aplasia. The mean systemic clearance of lurtotecan in plasma was 0.946 +/- 1.53 L/hour/m2. Urinary recovery of lurtotecan was 6.66% +/- 5.26% (range, 1.05-18.4%).

CONCLUSIONS

Liposomal encapsulation of lurtotecan altered its metabolism significantly. There was no evident correlation between exposure, as measured by plasma pharmacokinetics of lurtotecan, and clinical response or toxicities. OSI-211 merits further study in hematologic malignancies.

OSI-211, a novel liposomal topoisomerase I inhibitor, is active in SCID mouse models of human AML and ALL

OSI-211 (liposomal lurtotecan), was evaluated using several different dose schedules (1mg/kg, d1-5, 1.75 mg/kg d1, 3, 5 and 6 mg/kg d1, 8) in severe combined immunodeficient (SCID) mouse models of acute myelogenous leukemia (AML) and acute lymphocytic leukemia (ALL) with early treatment (ET, days 6-8) or late treatment (LT, days 15-19), examining early and advanced disease, respectively. Due to the aggressive nature of the Molt-4 model, the ET and LT were accelerated to day 3 or 4 and day 8 post-implant, respectively. For each model, 2 x 10(7) (KBM-3B) or 1 x 10(7) (Molt-4, HL-60 and CEM) leukemia cells were injected intravenously into the tail vein. Each control and test group consisted of eight animals. All three schedules (1mg/kg qd1-5, 1.75 mg/kg d1, 3, 5 and 6 mg/kg d1, 8) increased the life span of OSI-211 treated animals in each model, with a tendency toward improved efficacy with the 6 mg/kg d1, 8 schedule. As a result, the activity of the 6 mg/kg d1, 8 schedule is detailed for each model. ET significantly (P<0.005) increased survival in the KBM-3B model with 86% long-term survivors (LTS). Using PRC analysis, human beta-globin gene sequences in one or several tissues were amplified in all but 3 LTS, suggesting minimal residual disease in 26 of the 29 LTS. LT also significantly (P<0.005) improved average life span in the KBM-3B model, with an average ILS=196+/-11% and one LTS. Treatment of HL-60 leukemia animals significantly (P<0.005) increased life span, with an ILS=213+/-9% and two LTS for ET, and with an ILS=219+/-4% and no LTS for LT. Treatment of Molt-4 animals, the most aggressive leukemia model tested, significantly (P<0.005) increased life span, with an average ILS=181+/-3% and no LTS for ET and an average ILS=172+/-1% with no LTS for LT. In the CEM model, ET resulted in a significantly (P<0.005) improved ILS=244+/-24% with one LTS. In comparison to OSI-211, treatment with DaunoXome, the liposomal formulation of daunorubicin, a drug with clinical efficacy in AML and ALL, had no effect on survival in the KBM-3B, nor Molt-4 A4 leukemia models when administered at its maximum or near maximum tolerated doses of 3mg/kg d1, 8. These data demonstrate that OSI-211 has potent antileukemia activity in preclinical SCID mouse AML and ALL leukemia models, supporting the clinical investigation of OSI-211 for hematological malignancies.

Phase I and pharmacologic study of liposomal lurtotecan, NX 211: urinary excretion predicts hematologic toxicity

PURPOSE

To determine the maximum-tolerated and recommended dose, toxicity profile, and pharmacokinetics of the liposomal topoisomerase I inhibitor lurtotecan (NX 211) administered as a 30-minute intravenous infusion once every 3 weeks in cancer patients.

PATIENTS AND METHODS

NX 211 was administered by peripheral infusion. Dose escalation decisions were based on all toxicities during the first cycle as well as pharmacokinetic parameters. Serial plasma, whole blood, and urine samples were collected for up to 96 hours after the end of infusion, and drug levels were determined by high-performance liquid chromatography.

RESULTS

Twenty-nine patients (16 women; median age, 56 years; range, 39 to 74 years) received 77 courses of NX 211 at dose levels of 0.4 (n = 3), 0.8 (n = 6), 1.6 (n = 3), 3.2 (n = 6), 3.8 (n = 6), and 4.3 mg/m(2) (n = 5). Neutropenia and thrombocytopenia were the dose-limiting toxicities and were not cumulative. Other toxicities were mild to moderate. Nine patients had stable disease while undergoing treatment. The systemic clearance of lurtotecan in plasma and whole blood was 0.82 +/- 0.78 L/h/m(2) and 1.15 +/- 0.96 L/h/m(2), respectively. Urinary recovery (Fu) of lurtotecan was 10.1% +/- 4.05% (range, 4.9% to 18.9%). In contrast to systemic exposure measures, the dose excreted in urine (ie, dose x Fu) was significantly related to the percent decrease in neutrophil and platelet counts at nadir (P <.00001).

CONCLUSION

The dose-limiting toxicities of NX 211 are neutropenia and thrombocytopenia. The recommended dose for phase II studies is 3.8 mg/m(2) once every 3 weeks. Pharmacologic data suggest a relationship between exposure to lurtotecan and NX 211-induced clinical effects.

Camptothecins

Camptothecin analogues and derivatives appear to exert their antitumour activity by binding to topoisomerase I and have shown significant activity against a broad range of tumours. In general, camptothecins are not substrates for either the multidrug-resistance P-glycoprotein or the multidrug-resistance-associated protein (MRP). Because of manageable toxicity and encouraging activity against solid tumours, camptothecins offer promise in the clinical management of human tumours. This review illustrates the proposed mechanism(s) of action of camptothecins and presents a concise overview of current camptothecin therapy, including irinotecan and topotecan, and novel analogues undergoing clinical trails, such as exatecan (DX-8951f), IDEC-132 (9-aminocamptothecin), rubitecan (9-nitrocamptothecin), lurtotecan (GI-147211C), and the recently developed homocamptothecins diflomotecan (BN-80915) and BN-80927.

Separation methods for camptothecin and related compounds

This paper reviews working procedures for the analytical determination of camptothecin and analogues. We give an overview of aspects such as the chemistry, structure-activity relationships, stability and mechanism of action of these antitumor compounds. The main body of the review describes separation techniques. Sample treatment and factors influencing high-performance liquid chromatography development are delineated. Published high-performance liquid chromatographic methods are summarized to demonstrate the variability and versatility of separation techniques and a critical evaluation of separation efficiency, detection sensitivity and specificity of these methods is reported.

Antitumor drugs possessing topoisomerase I inhibition: applicable separation methods

Separation methods for antitumor drugs capable of topoisomerase I inhibition were reviewed in this study. Camptothecin (CPT) its related analogues seemed to be promising anticancer drugs that exhibit topoisomerase I inhibition. This group of compounds contain a closed alpha-hydroxy-delta-lactone ring (lactone form) that can undergo reversible hydrolysis to form the open-ring form (carboxylate form). In vitro pharmacological study showed that the antitumor activity of the lactone form was higher than that of the carboxylate form. Thus a quantitative method to separate these two forms is important to evaluate the pharmacokinetics and pharmacodynamics of these compounds. Nevertheless, current separation methods are complicated by the pH-dependent instability of the lactone moiety. High-performance liquid chromatography (HPLC) coupled with fluorometric detection has been widely used for the quantitation of the drug as the intact lactone form or as the total lactone carboxylate forms in biological matrices. In this report we reviewed current applicable chromatographic techniques for further bioanalytical studies of CPT derivatives including sample preparations, HPLC columns, mobile phases and additives.

Quantitation of camptothecin and related compounds

Camptothecin and congeners represent a clinically very useful class of anticancer agents. Proper identification and quantitation of the original compounds and their metabolites in biological fluids is fundamental to assess drug metabolism and distribution in animals and in man. In this paper we will review the recent literature available on the methods used for separation and quantitative determination of the camptothecin family of drugs. Complications arise from the fact that they are chemically labile, and the pharmacologically active lactone structure can undergo ring opening at physiological conditions. In addition, a number of metabolic changes usually occur, producing a variety of active or inactive metabolites. Hence, the conditions of extraction, pre-treatment and quantitative analysis are to be carefully calibrated in order to provide meaningful results.

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.

Determination of camptothecin analogs in biological matrices by high-performance liquid chromatography

Several analogs of the topoisomerase I inhibitor camptothecin (CPT) have been introduced in clinical practice in the last decade. All CPT analogs are sensitive to a pH-dependent reversible conversion between a pharmacologically active lactone form and its inactive, lactone ring-opened, carboxylate form. The reversible conversion is also dependent on the, sometimes species-dependent, protein binding properties of the two forms, resulting in different lactone to carboxylate plasma ratios for the various analogs. Pharmacokinetic analysis of the CPT analogs is helpful in understanding the pharmacodynamic outcome of drug treatment, in clinical as well preclinical studies. Measurement of these analogs is habitually complicated by the chemical instability of the lactone moiety and necessitates a rapid centrifugation of the blood sample, preferably at the bedside of the patient, to collect the plasma supernatant. Since the lactone forms of these drugs are able to diffuse across cell membranes, including those of the red blood cells, rapid collection and processing is even necessary in the case where only the total concentrations of the CPT analogs are to be measured. Sample pretreatment procedures of the CPT analogs topotecan, irinotecan, 9-aminocamptothecin and lurtotecan are summarized and discussed in this review.