Cyclophosphamide, hydroxycyclophosphamide and carboxyethyl phosphoramide mustard quantification with liquid chromatography mass spectrometry in a single run human plasma samples: A rapid and sensitive method development.

A novel method for simultaneous quantification of cyclophosphamide along with its two major metabolites namely 4-hydroxycyclophosphamide (HCy) and carboxyethyl phosphoramide mustard (CEPM) in a single sample run was demonstrated in the present study. A liquid chromatography-tandem mass spectrometry (LC-MS/MS) instrument was used for analysis. Semicarbazide was used as a stabilizing agent for HCy whereas ifosfamide, hexamethyl phosphoramide mustard and deuterated CEPM were the internal standards for quantification of Cy, HCy and CEPM respectively. Chromatographic separation was achieved by Chromsystems C18 reverse-phase column (50 mm × 4.6 mm, particle size 3.2 µm). The mobile phase was composed of eluent A (2 mM ammonium acetate in water with 2% formic acid) and eluent B (100 % acetonitrile). The flow rate was 1 ml/min. Linearity of the assay was assured in the range of 19.53 ng/ml to 10,000 ng/ml concentration in human plasma, which is adequate for pharmacokinetic studies of any dose Cy used clinically. The quality control(QC) accuracy was between 99.58% and 101.62%, 97.85% to 103.53% and 99.64% to 100.10% for Cy, HCy and CEPM respectively. Precision limits for QC samples were between 3.9% and 9.4%, 5.2% to 8.9% and 1.8% to 9.2% respectively. The analytical method was validated in ten leukaemia patients undergoing haploidentical hematopoietic cell transplantation.

Mitochondria-targeting multifunctional nanoplatform for cascade phototherapy and hypoxia-activated chemotherapy.

Despite considerable progress has been achieved in hypoxia-associated anti-tumor therapy, the efficacy of utilizing hypoxia-activated prodrugs alone is not satisfied owing to the inadequate hypoxia within the tumor regions. In this work, a mitochondrial targeted nanoplatform integrating photodynamic therapy, photothermal therapy and hypoxia-activated chemotherapy has been developed to synergistically treat cancer and maximize the therapeutic window. Polydopamine coated hollow copper sulfide nanoparticles were used as the photothermal nanoagents and thermosensitive drug carriers for loading the hypoxia-activated prodrug, TH302, in our study. Chlorin e6 (Ce6) and triphenyl phosphonium (TPP) were conjugated onto the surface of the nanoplatform. Under the action of TPP, the obtained nanoplatform preferentially accumulated in mitochondria to restore the drug activity and avoid drug resistance. Using 660 nm laser to excite Ce6 can generate ROS and simultaneously exacerbate the cellular hypoxia. While under the irradiation of 808 nm laser, the nanoplatform produced local heat which can increase the release of TH302 in tumor cells, ablate cancer cells as well as intensify the tumor hypoxia levels. The aggravated tumor hypoxia then significantly boosted the anti-tumor efficiency of TH302. Both in vitro and in vivo studies demonstrated the greatly improved anti-cancer activity compared to conventional hypoxia-associated chemotherapy. This work highlights the potential of using a combination of hypoxia-activated prodrugs plus phototherapy for synergistic cancer treatment.

An Intratumor Pharmacokinetic/Pharmacodynamic Model for the Hypoxia-Activated Prodrug Evofosfamide (TH-302): Monotherapy Activity is Not Dependent on a Bystander Effect.

Tumor hypoxia contributes to resistance to anticancer therapies. Hypoxia-activated prodrugs (HAPs) selectively target hypoxic cells and their activity can extend to well-oxygenated areas of tumors via diffusion of active metabolites. This type of bystander effect has been suggested to be responsible for the single agent activity of the clinical-stage HAP evofosfamide (TH-302) but direct evidence is lacking. To dissect the contribution of bystander effects to TH-302 activity, we implemented a Green's function pharmacokinetic (PK) model to simulate the spatial distribution of O2, TH-302 and its cytotoxic metabolites, bromo-isophosphoramide mustard (Br-IPM) and its dichloro derivative isophosphoramide mustard (IPM), in two digitized tumor microvascular networks. The model was parameterized from literature and experimentally, including measurement of diffusion coefficients of TH-302 and its metabolites in multicellular layer cultures. The latter studies demonstrate that Br-IPM and IPM cannot diffuse significantly from the cells in which they are generated, although evidence was obtained for diffusion of the hydroxylamine metabolite of TH-302. The spatially resolved PK model was linked to a pharmacodynamic (PD) model that describes cell killing probability at each point in the tumor microregion as a function of Br-IPM and IPM exposure. The resulting PK/PD model accurately predicted previously reported monotherapy activity of TH-302 in H460 tumors, without invoking a bystander effect, demonstrating that the notable single agent activity of TH-302 in tumors can be accounted for by significant bioreductive activation of TH-302 even in oxic regions, driven by the high plasma concentrations achievable with this well-tolerated prodrug.

The hypoxia-activated prodrug evofosfamide in combination with multiple regimens of radiotherapy.

The promising treatment combination of ionizing radiation (IR) with a hypoxia-activated prodrug (HAP) is based on biological cooperation. Here we investigated the hypoxia-activated prodrug evofosfamide in combination with different treatment regimens of IR against lung A549- and head&neck UT-SCC-14-derived tumor xenografts. DNA damage-related endpoints and clonogenic cell survival of A549 and UT-SCC-14 carcinoma cells were probed under normoxia and hypoxia.Evofosfamide (TH-302) induced DNA-damage and a dose-dependent antiproliferative response in A549 cells on cellular pretreatment under hypoxia, and supra-additively reduced clonogenic survival in combination with IR. Concomitant treatment of A549-derived tumor xenografts with evofosfamide and fractionated irradiation induced the strongest treatment response in comparison to the corresponding neoadjuvant and adjuvant regimens. Adjuvant evofosfamide was more potent than concomitant and neoadjuvant evofosfamide when combined with a single high dose of IR. Hypoxic UT-SCC-14 cells and tumor xenografts thereof were resistant to evofosfamide alone and in combination with IR, most probably due to reduced P450 oxidoreductase expression, which might act as major predictive determinant of sensitivity to HAPs.In conclusion, evofosfamide with IR is a potent combined treatment modality against hypoxic tumors. However, the efficacy and the therapeutic outcome of this combined treatment modality is, as indicated here in preclinical tumor models, dependent on scheduling parameters and tumor type, which is most probably related to the status of respective HAP-activating oxidoreductases. Further biomarker development is necessary for the launch of successful clinical trials.

Design, synthesis and biological evaluation of quinazoline-phosphoramidate mustard conjugates as anticancer drugs.

A series of novel compounds with phosphoramide mustard functionality incorporated into the quinazoline scaffold of EGFR/HER2 inhibitors were designed and synthesized as multi-target-directed ligands against tumor cells. In vitro assays showed that tumor cell lines with high HER2 level were more sensitive to the compounds than tumor cells with low HER2 level. Compound 10d (EMB-3) was one of the most potent inhibitors with IC50 of 7.4 nM and 82 nM against EGFR and HER2, respectively. The mechanism studies were also supported by the effect of 10d-induced DNA damage in MDA-MB-468 cells. In vivo efficacy study showed that 10d could significantly inhibit H522 tumor xenograft model with a TGI of 68% at dose of 100 mg/kg (QDx28, p.o.) and no significant body weight loss was observed. MTD study indicated that compound 10d had no acute toxicity to mice at doses up to 900 mg/kg (single dose).

MR Imaging Biomarkers to Monitor Early Response to Hypoxia-Activated Prodrug TH-302 in Pancreatic Cancer Xenografts.

TH-302 is a hypoxia-activated prodrug known to activate selectively under the hypoxic conditions commonly found in solid tumors. It is currently being evaluated in clinical trials, including two trials in Pancreatic Ductal Adenocarcinomas (PDAC). The current study was undertaken to evaluate imaging biomarkers for prediction and response monitoring of TH-302 efficacy in xenograft models of PDAC. Dynamic contrast-enhanced (DCE) and diffusion weighted (DW) magnetic resonance imaging (MRI) were used to monitor acute effects on tumor vasculature and cellularity, respectively. Three human PDAC xenografts with known differential responses to TH-302 were imaged prior to, and at 24 h and 48 hours following a single dose of TH-302 or vehicle to determine if imaging changes presaged changes in tumor volumes. DW-MRI was performed at five b-values to generate apparent diffusion coefficient of water (ADC) maps. For DCE-MRI, a standard clinically available contrast reagent, Gd-DTPA, was used to determine blood flow into the tumor region of interest. TH-302 induced a dramatic decrease in the DCE transfer constant (Ktrans) within 48 hours after treatment in the sensitive tumors, Hs766t and Mia PaCa-2, whereas TH-302 had no effect on the perfusion behavior of resistant SU.86.86 tumors. Tumor cellularity, estimated from ADC, was significantly increased 24 and 48 hours after treatment in Hs766t, but was not observed in the Mia PaCa-2 and SU.86.86 groups. Notably, growth inhibition of Hs766t was observed immediately (day 3) following initiation of treatment, but was not observed in MiaPaCa-2 tumors until 8 days after initiation of treatment. Based on these preclinical findings, DCE-MRI measures of vascular perfusion dynamics and ADC measures of cell density are suggested as potential TH-302 response biomarkers in clinical trials.

Identification of P450 Oxidoreductase as a Major Determinant of Sensitivity to Hypoxia-Activated Prodrugs.

Hypoxia is a prevalent feature of many tumors contributing to disease progression and treatment resistance, and therefore constitutes an attractive therapeutic target. Several hypoxia-activated prodrugs (HAP) have been developed, including the phase III candidate TH-302 (evofosfamide) and the preclinical agent SN30000, which is an optimized analogue of the well-studied HAP tirapazamine. Experience with this therapeutic class highlights an urgent need to identify biomarkers of HAP sensitivity, including enzymes responsible for prodrug activation during hypoxia. Using genome-scale shRNA screens and a high-representation library enriched for oxidoreductases, we identified the flavoprotein P450 (cytochrome) oxidoreductase (POR) as the predominant determinant of sensitivity to SN30000 in three different genetic backgrounds. No other genes consistently modified SN30000 sensitivity, even within a POR-negative background. Knockdown or genetic knockout of POR reduced SN30000 reductive metabolism and clonogenic cell death and similarly reduced sensitivity to TH-302 under hypoxia. A retrospective evaluation of head and neck squamous cell carcinomas showed heterogeneous POR expression and suggested a possible relationship between human papillomavirus status and HAP sensitivity. Taken together, our study identifies POR as a potential predictive biomarker of HAP sensitivity that should be explored during the clinical development of SN30000, TH-302, and other hypoxia-directed agents.

Hypoxia-activated chemotherapeutic TH-302 enhances the effects of VEGF-A inhibition and radiation on sarcomas.

BACKGROUND: Human sarcomas with a poor response to vascular endothelial growth factor-A (VEGF-A) inhibition and radiation therapy (RT) have upregulation of hypoxia-inducible factor 1α (HIF-1α) and HIF-1α target genes. This study examines the addition of the hypoxia-activated chemotherapy TH-302 to VEGF-A inhibition and RT (a.k.a. trimodality therapy). METHODS: Trimodality therapy was examined in two xenograft models and in vitro in tumour endothelial cells and sarcoma cell lines. RESULTS: In both mouse models, VEGF-A inhibition and radiation showed greater efficacy than either therapy alone in slowing sarcoma growth. When TH-302 was added, this trimodality therapy completely blocked tumour growth with tumours remaining dormant for over 3 months after cessation of therapy. Trimodality therapy caused 2.6- to 6.2-fold more endothelial cell-specific apoptosis than bimodality therapies, and microvessel density and HIF-1α activity were reduced to 11-13% and 13-20% of control, respectively. When trimodality therapy was examined in vitro, increases in DNA damage and apoptosis were much more pronounced in tumour endothelial cells compared with that in sarcoma cells, especially under hypoxia. CONCLUSIONS: The combination of TH-302, VEGF-A inhibition, and RT is highly effective in preclinical models of sarcoma and is associated with increased DNA damage and apoptosis in endothelial cells and decreased HIF-1α activity.

Hypoxia-activated pro-drug TH-302 exhibits potent tumor suppressive activity and cooperates with chemotherapy against osteosarcoma.

Tumor hypoxia is a major cause of treatment failure for a variety of malignancies. However, tumor hypoxia also offers treatment opportunities, exemplified by the development compounds that target hypoxic regions within tumors. TH-302 is a pro-drug created by the conjugation of 2-nitroimidazole to bromo-isophosphoramide (Br-IPM). When TH-302 is delivered to regions of hypoxia, Br-IPM, the DNA cross linking toxin, is released. In this study we assessed the cytotoxic activity of TH-302 against osteosarcoma cells in vitro and evaluated its anticancer efficacy as a single agent, and in combination with doxorubicin, in an orthotopic mouse model of human osteosarcoma (OS). In vitro, TH-302 was potently cytotoxic to osteosarcoma cells selectively under hypoxic conditions, whereas primary normal human osteoblasts were protected. Animals transplanted with OS cells directly into their tibiae and left untreated developed mixed osteolytic/osteosclerotic bone lesions and subsequently developed lung metastases. TH-302 reduced tumor burden in bone and cooperated with doxorubicin to protect bone from osteosarcoma induced bone destruction, while it also reduced lung metastases. TH-302 may therefore be an attractive therapeutic agent with strong activity as a single agent and in combination with chemotherapy against OS.

Analysis of cyclophosphamide and carboxyethylphosphoramide mustard enantiomers in human plasma and application to clinical pharmacokinetics.

This study describes for the first time a method for the sequential analysis of the enantiomers of cyclophosphamide (CY) and its metabolite carboxyethylphosphoramide mustard (CEPM) in human plasma. The CY and CEPM enantiomers were extracted from plasma using only ethyl acetate and separated on a Chiralpak(®) AD-RH column using a mixture of water:acetonitrile:ethanol (45:30:25, v/v/v) plus 0.1% trifluoroacetic acid as the mobile phase at a flow rate of 0.5mL/min. No matrix effect was observed in the analysis of the enantiomers of both analytes and the analytical method was linear in the range of 0.05-25.0µg and 250-1000ng of each enantiomer/mL plasma. The coefficients of variation and relative errors obtained for the assessment of intra- and interassay precision and accuracy were less than 15%. CY and CEPM were found to be stable in human plasma after three successive freeze/thaw cycles, during storage for 4h at room temperature, and after 24h inside the autosampler at 4°C, with deviations less than 15%. The method was applied to the study of the pharmacokinetics of CY and its metabolite CEPM in patients with multiple sclerosis (n=10) who received a CY pretransplant conditioning regimen for hematopoietic stem cell transplantation. The pharmacokinetic parameters showed plasma accumulation of the (S)-(-)-CY enantiomer (S/R ratio=1.3) and lack of enantioselective exposure to the CEPM metabolite (S/R ratio=1.0).

Involvement of a volatile metabolite during phosphoramide mustard-induced ovotoxicity.

The finite ovarian follicle reserve can be negatively impacted by exposure to chemicals including the anti-neoplastic agent, cyclophosphamide (CPA). CPA requires bioactivation to phosphoramide mustard (PM) to elicit its therapeutic effects however; in addition to being the tumor-targeting metabolite, PM is also ovotoxic. In addition, PM can break down to a cytotoxic, volatile metabolite, chloroethylaziridine (CEZ). The aim of this study was initially to characterize PM-induced ovotoxicity in growing follicles. Using PND4 Fisher 344 rats, ovaries were cultured for 4 days before being exposed once to PM (10 or 30 µM). Following eight additional days in culture, relative to control (1% DMSO), PM had no impact on primordial, small primary or large primary follicle number, but both PM concentrations induced secondary follicle depletion (P<0.05). Interestingly, a reduction in follicle number in the control-treated ovaries was observed. Thus, the involvement of a volatile, cytotoxic PM metabolite (VC) in PM-induced ovotoxicity was explored in cultured rat ovaries, with control ovaries physically separated from PM-treated ovaries during culture. Direct PM (60 µM) exposure destroyed all stage follicles after 4 days (P<0.05). VC from nearby wells depleted primordial follicles after 4 days (P<0.05), temporarily reduced secondary follicle number after 2 days, and did not impact other stage follicles at any other time point. VC was determined to spontaneously liberate from PM, which could contribute to degradation of PM during storage. Taken together, this study demonstrates that PM and VC are ovotoxicants, with different follicular targets, and that the VC may be a major player during PM-induced ovotoxicity observed in cancer survivors.

Pharmacokinetics of TH-302: a hypoxically activated prodrug of bromo-isophosphoramide mustard in mice, rats, dogs and monkeys.

PURPOSE: To characterize the pharmacokinetics of the prodrug, TH-302, and its active metabolite, bromo-IPM (Br-IPM), in nonclinical species. METHODS: TH-302 was administered in single oral, intraperitoneal and intravenous bolus doses to mice, rats, dogs and monkeys as well as in acute and chronic safety studies in rats and dogs as a 30-min intravenous infusion given once a week for 3 weeks. Assessments were made using liquid chromatography-tandem mass spectrometry. RESULTS: TH-302 was extensively distributed with high systemic clearance exceeding hepatic plasma flow in all species studied, resulting in half-lives ranging between 8 min (mice) and over 4 h (rats). In rats, TH-302 exhibited linear kinetics following intravenous administration and good oral bioavailability. In acute and chronic safety studies, there was no accumulation of TH-302 following once weekly dosing for 3 weeks in the rat and dog. Br-IPM plasma concentrations were a small fraction of the TH-302 plasma concentrations with significantly smaller percentages present in dogs than in rats. Allometric scaling predicted that the systemic clearance and steady-state volume of distribution in humans would be 38.8 l/h/m(2) and 34.3 l/m(2), respectively, resulting in a terminal elimination half-life of about 36 min. These values were similar to those observed in patients with solid tumors (27.1 l/h/m(2), 23.5 l/m(2) and 47 min). CONCLUSIONS: TH-302 exhibited good safety, efficacy and pharmacokinetic properties in nonclinical species, translating into favorable properties in humans.

Metabolism, pharmacokinetics and excretion of a novel hypoxia activated cytotoxic prodrug, TH-302, in rats.

The metabolism, pharmacokinetics and excretion of a hypoxically activating prodrug developed for the treatment of cancer, TH-302, were studied in rats following intravenous administration of 50 mg/kg [(14)C]-TH-302. The pharmacokinetics of TH-302 was characterized by a short half-life of 12.3 min, a high clearance of 2.29 L/h/kg and a volume of distribution of 0.627 L/kg. In intact and bile duct-cannulated rats, TH-302 was extensively metabolized with total recovery in excreta of 68.1% and 85.8%, respectively, with equal amounts excreted through urine and bile. Quantitative whole body autoradiography showed rapid distribution of [(14)C]-TH-302 associated radioactivity with the highest concentrations in the kidney and small intestinal content, suggesting significant biliary excretion and/or gut secretion. TH-302 was metabolized via (i) hydrolysis to form 2-bromoethyl amine RM3 (7.5%); (ii) monoglutathione conjugation and subsequently to the mercapturic acid RM13 (7.5%); and (iii) diglutathione conjugation followed by hydrolysis to form the dicysteine conjugate RM5 (6.5%). A large percentage (19.7%) of the dose in the excreta was associated with unidentified polar metabolites RM1 and RM2. TH-302 was the predominant circulating component in plasma and the two major metabolites in plasma were the cysteine conjugate RM8 and mercapturic acid RM13.

Anticancer activity of stabilized palifosfamide in vivo: schedule effects, oral bioavailability, and enhanced activity with docetaxel and doxorubicin.

Palifosfamide, the DNA-alkylating metabolite of ifosfamide (IFOS), has been synthesized as a stabilized tris or lysine salt and found to have preclinical and clinical antitumor activity. Stabilized palifosfamide overcomes limitations of IFOS because of patient-to-patient variability in response resulting from variable prodrug activation, resistance and toxicities of metabolic byproducts, acrolein and chloroacetaldehyde. Palifosfamide represents an effective alternative to IFOS and other DNA-alkylating prodrugs. The antitumor activities of stabilized palifosfamide were investigated in vivo. Dose response, route and schedule of administration, and interaction with docetaxel or doxorubicin were investigated in NCr-nu/nu mice bearing established orthotopic mammary MX-1 tumor xenografts. Oral activity was investigated in P388-1 leukemia in CD2F1 mice. Oral and intraperitoneal bioavailabilities were compared in Sprague-Dawley rats. Stabilized palifosfamide administered by optimized regimens suppressed MX-1 tumor growth (P<0.05) by greater than 80% with 17% complete antitumor responses and up to three-fold increase in time to three tumor doublings over controls. Median survival in the P388-1 (P<0.001) model was increased by 9 days over controls. Oral bioavailability in rats was 48-73% of parenteral administration, and antitumor activity in mice was equivalent by both routes. Treatment with palifosfamide-tris combined with docetaxel or doxorubicin at optimal regimens resulted in complete tumor regression in 62-75% of mice. These studies support investigation of stabilized palifosfamide in human cancers by parenteral or oral administration as a single agent and in combination with other approved drugs. The potential for clinical translation of the cooperative interaction of palifosfamide-tris with doxorubicin by intravenous administration is supported by results from a recent randomized Phase-II study in unresectable or metastatic soft-tissue sarcoma.

A phase I study of the safety and pharmacokinetics of the hypoxia-activated prodrug TH-302 in combination with doxorubicin in patients with advanced soft tissue sarcoma.

PURPOSE: The purpose of this study was to determine the dose-limiting toxicities (DLT), maximum tolerated dose (MTD), safety, pharmacokinetics and preliminary activity of TH-302, a hypoxia-activated prodrug, in combination with doxorubicin in patients with advanced soft tissue sarcoma. PATIENTS AND METHODS: TH-302 was administered intravenously on days 1 and 8 and doxorubicin 75 mg/m² on day 1 (2 h after TH-302) of every 3-week cycle. TH-302 starting dose was 240 mg/m² with a classic 3 + 3 dose escalation. Pharmacokinetics were assessed on days 1 and 8 of cycle 1. Tumor assessments were performed after every second cycle. RESULTS: Sixteen patients enrolled. Prophylactic growth factor support was added due to grade 4 neutropenia. The MTD was 300 mg/m². DLTs at 340 mg/m² were neutropenia-associated infection and grade 4 thrombocytopenia. Common adverse events included fatigue, nausea and skin rash. There was no evidence of pharmacokinetic interaction between TH-302 and doxorubicin. Five of 15 (33%) evaluable patients had a partial response by RECIST (Response Evaluation Criteria in Solid Tumors) criteria. CONCLUSIONS: The hematologic toxicity of doxorubicin is increased when combined with TH-302. This can be mitigated by prophylactic growth factor support. Toxicities were manageable and there was evidence of antitumor activity.

Phase 1 study of the safety, tolerability, and pharmacokinetics of TH-302, a hypoxia-activated prodrug, in patients with advanced solid malignancies.

PURPOSE: The objectives of this phase 1, first-in-human study were to determine the dose-limiting toxicities (DLT), maximum tolerated dose (MTD), safety, pharmacokinetics, and preliminary activity of the hypoxia-activated prodrug TH-302 in patients with advanced solid tumors. EXPERIMENTAL DESIGN: TH-302 was administered intravenously over 30 to 60 minutes in two regimens: three times weekly dosing followed by 1 week off (arm A) and every 3-week dosing (arm B). RESULTS: Fifty-seven patients enrolled (arm A: N = 37 and arm B: N = 20). The TH-302 dose was escalated from 7.5 to 670 mg/m(2) in arm A and from 670 to 940 mg/m(2) in arm B. The most common adverse events were nausea, skin rash, fatigue, and vomiting. Hematologic toxicity was mild and limited. Grade 3 skin and mucosal toxicities were dose limiting at 670 mg/m(2) in arm A; the MTD was 575 mg/m(2). In arm B, grade 3 fatigue and grade 3 vaginitis/proctitis were dose limiting at 940 mg/m(2); the MTD was 670 mg/m(2). Plasma concentrations of TH-302 and the active metabolite Br-IPM (brominated version of isophosphoramide mustard) increased proportionally with dose. Two partial responses were noted in patients with metastatic small cell lung cancer (SCLC) and melanoma in arm A at 480 and 670 mg/m(2). Stable disease was observed in arms A and B in 18 and 9 patients, respectively. CONCLUSIONS: The MTD of TH-302 was 575 mg/m(2) weekly and 670 mg/m(2) every 3 weeks. Skin and mucosal toxicities were DLTs. On the basis of responses in metastatic melanoma and SCLC, further investigations in these indications were initiated.

Glufosfamide as a new oxazaphosphorine anticancer agent.

Glufosfamide (ß-D-glucose-isophosphoramide mustard, D-19575) belongs to the oxazaphosphorine class. Glufosfamide is a novel glucose conjugate of ifosfamide in which isophosphoramide mustard, the alkylating metabolite of ifosfamide, is glycosidically linked to the ß-D-glucose molecule. Glufosfamide represents an attractive new agent for cancer therapy. Its mode of action on normal and pathological cells is still under experimental and clinical investigations. An assessment of the anticancer potential of glufosfamide is of key importance in therapy. The researchers reviewed the current knowledge available on glufosfamide tested in the preclinical studies/clinical trials, based on a collection of the original papers and conference abstracts published and relevant articles searched in the SCOPUS and MEDLINE database and websites.

Phase I clinical and pharmacokinetic study of the glucose-conjugated cytotoxic agent D-19575 (glufosfamide) in patients with solid tumors.

PURPOSE: D-19575 (glufosfamide: ß-D-glucosylisophosphoramide mustard) is an alkylating agent in which isophosphoramide mustard, the cytotoxic metabolite of ifosfamide, is covalently linked to ß-D-glucose. We have performed a phase I study to determine the safety profile, pharmacokinetics, and antitumor activity of D-19575 in Japanese patients with advanced solid tumors METHODS: Patients were treated with escalating doses of D-19575 administered by a two-step (fast-slow) intravenous infusion over 6 h every 3 weeks. Thirteen patients received 43 treatment cycles (median 3; range 1-11) at D-19575 doses of 3,200, 4,500, or 6,000 mg/m(2). RESULTS: Hematologic toxicities and other side effects were generally mild. The maximum tolerated dose of D-19575 was 6,000 mg/m(2), at which two patients experienced dose-limiting toxicities (hypophosphatemia, hypokalemia, and metabolic acidosis each of grade 3). Pharmacokinetic analysis revealed a linear relation between the area under the concentration-versus-time curve (AUC) and dose. The AUC values for isophosphoramide mustard were substantially greater than those achieved by bolus administration or continuous infusion of ifosfamide in conventional therapy. One patient with gallbladder cancer previously treated with cisplatin and gemcitabine achieved a partial response lasting for >5 months, and eight patients achieved disease stabilization. CONCLUSIONS: Our results show that D-19575 can be safely administered by infusion over 6 h at 4,500 mg/m(2) every 3 weeks. The safety profile and potential antitumor activity of D-19575 show that phase II studies of this drug are warranted.

Real-time dose adjustment of cyclophosphamide in a preparative regimen for hematopoietic cell transplant: a Bayesian pharmacokinetic approach.

PURPOSE: Dose-related toxicity of cyclophosphamide may be reduced and therapeutic efficacy may be improved by pharmacokinetic sampling and dose adjustment to achieve a target area under the curve (AUC) for two of its metabolites, hydroxycyclophosphamide (HCY) and carboxyethylphosphoramide mustard (CEPM). To facilitate real-time dose adjustment, we developed open-source code within the statistical software R that incorporates individual data into a population pharmacokinetic model. EXPERIMENTAL DESIGN: Dosage prediction performance was compared to that obtained with nonlinear mixed-effects modeling using NONMEM in 20 cancer patients receiving cyclophosphamide. Bayesian estimation of individual pharmacokinetic parameters was accomplished from limited (i.e., five samples over 0-16 hours) sampling of plasma HCY and CEPM after the initial cyclophosphamide dose. Conditional on individual pharmacokinetics, simulations of the AUC of both HCY and CEPM were provided for a range of second doses (i.e., 0-100 mg/kg cyclophosphamide). RESULTS: The results compared favorably with NONMEM and returned accurate predictions for AUCs of HCY and CEPM with comparable mean absolute prediction error and root mean square prediction error. With our method, the mean absolute prediction error and root mean square prediction error of AUC CEPM were 11.0% and 12.8% and AUC HCY were 31.7% and 44.8%, respectively. CONCLUSIONS: We developed dose adjustment software that potentially can be used to adjust cyclophosphamide dosing in a clinical setting, thus expanding the opportunity for pharmacokinetic individualization of cyclophosphamide. The software is simple to use (requiring no programming experience), reads individual patient data directly from an Excel spreadsheet, and runs in less than 5 minutes on a desktop PC.

Pharmacokinetics of N-2-chloroethylaziridine, a volatile cytotoxic metabolite of cyclophosphamide, in the rat.

OBJECTIVES: The objectives of this study were to characterize pharmacokinetics of N-2-chloroethylaziridine (CEA) in the rat model and assess the in vivo fraction of total clearance of phosphoramide mustard (PM) that furnished CEA to circulation. METHODS: The disposition of CEA was investigated following separate intravenous (iv) administrations of PM, synthetic CEA, and their combination to the Sprague-Dawley rats. In addition, in rats receiving prodrug cyclophosphamide (CP), plasma concentrations of CP and its metabolites, 4-hydroxycyclophosphamide (HOCP), PM, and CEA, were simultaneously quantified using GC/MS and stable isotope dilution techniques. RESULTS: Following iv administration of synthetic CEA, concentrations of CEA declined biexponentially with the mean terminal half-life and total body clearance of 47.5 min and 167 ml/min/kg, respectively. Urinary excretion of unchanged CEA was 0.164% of the administered dose. CEA was found to be the major circulating metabolite after iv administration of precursor PM to rats. The fraction of total clearance of PM that furnished CEA to circulation was estimated to be 100%, indicating virtually complete availability of the metabolite to circulation once formed. In rats administered with CP, PM exhibited the highest plasma and urinary concentrations compared to HOCP and CEA. CONCLUSIONS: For the first time, CEA was demonstrated to be an important in vivo metabolite of CP in the present study. In light of the poor permeability and in vivo stability of PM, the ultimate DNA alkylator, the findings obtained in this study suggested that CEA may contribute significantly to the overall antitumor activity of prodrug CP.