Pharmacological disposition of 1,4-dihydroxy-5-8-bis[[2 [(2-hydroxyethyl)amino]ethyl]amino]-9,10-anthracenedione dihydrochloride in the dog

Toxicity, outcome, and management of anthracycline overdoses in 16 dogs

Background

Despite multiple reports of chemotherapy overdoses (ODs) in human and veterinary medicine, anthracycline ODs have been described infrequently.

Hypothesis/Objectives

Describe toxicities, treatments, and overall outcome after anthracycline OD in dogs.

Animals

Twelve mitoxantrone (MTX) and 4 doxorubicin (DOX) ODs were evaluated.

Methods

Multicenter retrospective analysis. The American College of Veterinary Internal Medicine oncology and internal medicine listservs were solicited for cases in which a chemotherapy OD occurred.

Results

Sixteen anthracycline cases were collected. Anthracycline ODs occurred because of an error in chemotherapy preparation (n = 9), or dose miscalculation (n = 7). The overall median OD was 1.9× (range, 1.4‐10×) the prescribed amount. Most ODs were identified immediately after drug administration (n = 11), and the majority of patients were hospitalized on supportive care (n = 11) for an average of 8 days (range, 3‐34 days). Adverse events after the OD included neutropenia (94%), thrombocytopenia (88%), anemia (63%), diarrhea (63%), anorexia (56%), vomiting (38%), lethargy (31%), and nausea (25%). Two patients did not survive the OD. High grade neutropenia was common and did not appear to be mitigated by the administration of filgrastim.

Conclusions and Clinical Importance

All patients received supportive care after identifying the OD and death was uncommon. Further evaluation is needed to determine ideal therapeutic guidelines anthracycline OD.

A physiologically based pharmacokinetic model of mitoxantrone in mice and scale-up to humans: a semi-mechanistic model incorporating DNA and protein binding

We conducted a pharmacokinetic (PK) study of mitoxantrone (Novantrone®), a clinically well-established anticancer agent, in mice and developed a mechanism-based PBPK (physiologically based pharmacokinetic) model to describe its disposition. Mitoxantrone concentrations in plasma and six organs (lung, heart, liver, kidney, spleen, and brain) were determined after a 5 mg/kg i.v. dose. We evaluated three different PBPK models in order to characterize our experimental data: model 1 containing Kp values, model 2 incorporating a deep binding compartment, and model 3 incorporating binding of mitoxantrone to DNA and protein. Among the three models, only model 3 with DNA and protein binding captured all the experimental data well. The estimated binding affinity for DNA (K (DNA)) and protein (K (macro)) were 0.0013 and 1.44 μM, respectively. Predicted plasma and tissue AUC values differed from observed values by <19 %, except for heart (60 %). Model 3 was further used to simulate plasma mitoxantrone concentrations in humans for a 12-mg/m(2) dose, using human physiological parameters. The simulated results generally agreed with the observed time course of mitoxantrone plasma concentrations in patients after a standard dose of 12 mg/m(2). In summary, we reported for the first time a mechanism-based PBPK model of mitoxantrone incorporating macromolecule binding which may have clinical applicability in optimizing clinical therapy. Since mitoxantrone is a substrate of the efflux transporters ABCG2 and ABCB1, the incorporation of efflux transporters may also be necessary to characterize the data obtained in low-dose studies.

Mitoxantrone: a review of its use in multiple sclerosis

Mitoxantrone (Novantrone), a synthetic anthracenedione derivative, is an antineoplastic, immunomodulatory agent. Its presumed mechanism of action in patients with multiple sclerosis (MS) is via immunomodulatory mechanisms, although these remain to be fully elucidated. Intravenous mitoxantrone treatment improved neurological disability and delayed progression of MS in patients with worsening relapsing-remitting (RR) [also termed progressive-relapsing (PR) MS] or secondary-progressive (SP) disease. In a pivotal randomised, double-blind, multicentre trial, mitoxantrone 12 mg/m(2) administered once every 3 months for 2 years provided significant improvements in neurological disability ratings, including Kurtzke Expanded Disability Status Scale (EDSS), Ambulatory Index (AI) and Standardised Neurological Status (SNS) scores, compared with placebo. The drug also significantly reduced the mean number of corticosteroid-treated relapses and prolonged the time to the first treated relapse, with the beneficial effects on disease progression supported by magnetic resonance imaging. Post hoc analyses suggest that the benefits associated with mitoxantrone treatment may be sustained for at least 12 months after cessation of treatment, mean changes from baseline at 36 months in EDSS, AI and SNS scores of 0.10, 0.61 and 0.19, respectively, in the mitoxantrone group versus 0.46, 1.13 and 3.38 with placebo. Concomitant intravenous mitoxantrone 20mg plus intravenous methylprednisolone 1g once every month for 6 months was more effective than intravenous methylprednisolone monotherapy in preventing the development of new gadolinium-enhanced lesions in patients with very active RRMS or SPMS. The drug was generally well tolerated in patients with MS. Adverse events were generally mild to moderate in severity and usually resolved upon discontinuation of treatment or with appropriate pharmacotherapy. At the recommended dosage, mitoxantrone appears to have a low potential to cause cardiotoxicity. In conclusion, intravenous mitoxantrone reduces the relapse rate and slows progression of the disease in patients with worsening RRMS, PRMS or SPMS; thus providing a new option for the management of these patients. The drug was generally well tolerated at the recommended dosage, although potential cardiotoxicity limits the total cumulative dose to 140 mg/m(2). Further studies are warranted to determine which patients with worsening RRMS, PRMS or SPMS are most likely to benefit from mitoxantrone treatment and to more fully define the long-term safety and tolerability of mitoxantrone, including the use of concomitant cardioprotectants to extend the therapeutic lifespan of the drug. Pharmacodynamic Profile. Mitoxantrone, a synthetic anthracenedione derivative, is an established cytotoxic, antineoplastic agent. Its presumed mechanism of action in multiple sclerosis (MS) is immunosuppression. In antineoplastic studies, the drug showed several immunomodulatory effects, inducing macrophage-mediated suppression of B-cell, T-helper and T-cytotoxic lymphocyte function. Currently, the pharmacodynamic properties of mitoxantrone have not been investigated to any extent in patients with MS. In one study, 6 months' treatment with intravenous mitoxantrone generally had no effect on the distribution of cytokine-positive peripheral blood monocyte cells in patients with MS. In an animal model of the disease, mitoxantrone suppressed the development and progression of both actively and passively induced acute experimental allergic encephalomyelitis (EAE). It appeared to be 10-20 times more effective than cyclophosphamide in the suppression of EAE. Moreover, mitoxantrone approximately doubled the mean time to onset of EAE versus control animals (279 vs 148 days after immunisation; p < 0.00005). In vitro, mitoxantrone 10 and 100 micro g/L inhibited myelin degradation by leucocytes and peritoneal macrophages derived from mice with acute EAE by approximately 60% and 100%. Pharmacokinetic Profile. Currently, there are no published pharmacokinetic data for intravenous mitoxantrone in pitoxantrone in patients with MS, paediatric patients or in those with renal impairment. All studies, to date, have been in patients with cancer receiving a single, approximately 30-minute intravenous infusion of mitoxantrone 5-14 mg/m(2). The drug exhibits triexponential pharmacokinetics, with a rapid initial distribution (alpha) phase, an intermediate distribution (beta) phase and a much slower elimination (gamma) phase. The mean half-life of the alpha phase appears to be 6-12 minutes and that of the beta phase 1.1-3.1 hours. Mitoxantrone has a high affinity for tissue, with a volume of distribution of up to 2248 L/m(2). Mitoxantrone persists for prolonged periods in tissues and was detectable in autopsy tissue from patients who last received the drug up to 272 days before death. At concentrations of 10-10000 ng/mL, the drug was 70-80 % bound to plasma proteins in dogs. Elimination of mitoxantrone occurs predominantly through biliary excretion and may be impaired in patients with hepatic dysfunction or third space abnormalities (e.g. ascites). The mean terminal elimination half-life of mitoxantrone ranged from 23 hours to 215 hours. Renal clearance accounts for 10 % of the total clearance of the drug. Total clearance of mitoxantrone ranged from 13 to 34.2 L/h/m(2) and renal clearance from 0.9 to 2.7 L/h/m(2). The drug appears to have a low potential for interaction with other concomitantly administered agents. Therapeutic Efficacy. Intravenous mitoxantrone (infusion of > or = 5 minutes), either as monotherapy or in combination with intravenous methylprednisolone, delayed the progression of the disease in patients with secondary-progressive (SP) or worsening relapsing-remitting (RR) MS (the latter is also termed progressive-relapsing MS) in comparative, randomised, multicentre trials. In a double-blind, monotherapy trial (Mitoxantrone In Multiple Sclerosis [MIMS] trial), mitoxantrone 12 mg/m(2) (n = 60) once every 3 months for 2 years significantly improved neurological disability relative to placebo (n = 64), as assessed by changes in mean Kurtzke Expanded Disability Status Scale (EDSS) score, mean Ambulatory Index (AI) score and mean Standardised Neurological Status (SNS) score. The drug also significantly reduced the mean number of corticosteroid-treated relapses per patient and prolonged the time to the first treated relapse. A Wei-Lachin multivariate analysis of these five efficacy variables indicated that the global difference between the two treatment groups was 0.30 (p < 0.0001). Mitroxantrone was also more effective than placebo according to secondary endpoints in this study, with fewer mitoxantrone recipients experiencing a relapse, a deterioration of > or =1 EDSS point or a confirmed deterioration in EDSS score over a 3-month period. Mitoxantrone recipients also showed less deterioration in quality-of-life ratings and had fewer hospital admissions, whereas more placebo recipients had new gadolinium-enhanced lesions at study end (the latter parameter was assessed using magnetic resonance imaging [MRI] in a subgroup of 110 patients, including 40 patients who received an exploratory 5 mg/m(2) dose). Furthermore, post hoc analyses indicated that the beneficial effects of mitoxantrone treatment on EDSS, SNS and AI scores were sustained for at least 12 months after cessation of treatment, with mean changes from baseline at 36 months in EDSS, AI and SNS scores of 0.10, 0.61 and 0.19, respectively, in the mitoxantrone group versus 0.46, 1.13 and 3.38 with placebo. Preliminary data from a cost-minimisation analysis based on results from the MIMS trial indicated that approximately half of the cost of mitoxantrone was offset by cost savings in other areas associated with the treatment of MS (direct and indirect major costs), with a total annual incremental cost for mitoxantrone of dollar 1661 per patient. Combination therapy once-monthly with intravenous mitoxantrone 20mg plus intravenous methylprednisolone 1g was more effective than intravenous methylprednisolone 1g once every month in preventing the development of gadolinium-enhanced lesions in patients with very active RRMS or SPMS (double-blind assessment using MRI scans). After 6 months, significantly more combination therapy recipients had no new gadolinium-enhanced lesions (90.5% vs 31.3% with monotherapy; p < 0.001) [primary endpoint]. There were also significant reductions in both the mean number of new enhancing lesions and the total number of gadolinium-enhanced lesions in patients receiving combination therapy versus methylprednisolone monotherapy.Tolerability. Mitoxantrone was generally well tolerated in patients with MS. Treatment-emergent adverse events occurring significantly more frequently with mitoxantrone (12 mg/m(2) once every 3 months for 2 years) than placebo were nausea, alopecia, menstrual disorders, urinary tract infection, amenorrhoea, leucopenia and elevated gamma-glutamyltranspeptidase levels. Adverse events were usually mild to moderate in severity and generally resolved with discontinuation of treatment or when treated with appropriate pharmacotherapy. Eight percent of patients discontinued treatment in the mitoxantrone 12 mg/m(2) group due to an adverse event versus 3% of placebo recipients. The incidence of drug-related acute myelogenous leukaemia was very low (0.12%) in a cohort of 802 patients with MS receiving mitoxantrone. Evidence suggests that the risk of cardiotoxicity is low in patients with MS. After 1 year of monotherapy, 3.4% of mitoxantrone recipients had a reduction in left ventricular ejection fraction (LVEF) to < or =50% compared with 0% of placebo recipients; at the end of the second year, respective incidences were 1.9% and 2.9% (total cumulative dose of mitoxantrone per patient was 96 mg/m(2) after 2 years' treatment). (ABSTRACT TRUNCATED)

A comparison of the benefits of mitoxantrone and other recent therapeutic approaches in multiple sclerosis

The approval by the FDA of four immunomodulators (three IFNs and glatiramer acetate) and one immunosuppressant (mitoxantrone; Novantrone) for the treatment of multiple sclerosis is definitely the most important progress in this field since the first description of the disease > 150 years ago. However, both types of immunotherapies raise specific problems. Immunomodulators benefit patients in the relapsing-remitting phase, or patients in the secondary-progressive phase showing clinical and/or radiological signs of active inflammatory processes. Their benefit is modest, but seems to persist with long-term administration, as their tolerance is acceptable. Mitoxantrone is a rescue therapy reserved to patients with an aggressive, rapidly progressive form of the disease. This immunosuppressant is effective on inflammatory processes and pathomechanisms responsible for disability progression. Unfortunately, its cardiotoxicity and potential leukaemogenicity prevent an administration beyond 2 or 3 years. Thus, there is a need to improve on the efficacy of immunomodulators and to reduce the toxicity of immunosuppressants. Combination therapies with immunomodulators and antioxidants or with neuroprotective drugs against excitotoxicity or Na + /Ca 2+ channellopathy are currently being investigated. With regard to immunosuppressants, the development of monoclonal antibodies with fully human protein sequences and the synthesis of a new molecule as effective as mitoxantrone but with a much lower toxicity (pixantrone) seem promising to halt or even to prevent disability progression.

Tumor acidity, ion trapping and chemotherapeutics. II. pH-dependent partition coefficients predict importance of ion trapping on pharmacokinetics of weakly basic chemotherapeutic agents

Ion-trapping theory predicts that alkalinization of tumor extracellular pH will enhance the anti-tumor activity of weak-base chemotherapeutics. We have previously demonstrated that chronic and acute treatment of tumor-bearing mice with sodium bicarbonate results in tumor-specific alkalinization of extracellular pH. Furthermore, bicarbonate pretreatment enhances the anti-tumor activity of doxorubicin and mitoxantrone in two different mouse tumor models. Previous work has indicated subtle, yet significant differences between the pH sensitivities of the biodistribution and anti-tumor efficacies of doxorubicin and mitoxantrone in vitro. The present study demonstrates that systemic alkalinization selectively enhances tumor uptake of radiolabeled mitoxantrone, but not doxorubicin. Results using these two drugs are quantitatively and qualitatively very different, and can be explained on the basis of differences in the octanol-water partition coefficients of their charged forms. These results suggest that inducing metabolic alkalosis in patients would have a positive effect on response to mitoxantrone therapy. However, the therapeutic index would not increase if sodium bicarbonate also caused increased retention of mitoxantrone in susceptible normal tissues in the host. The major dose-limiting organ systems for mitoxantrone are heart, liver, bone marrow, spleen and blood cells. Bicarbonate was found to have no significant effect on the distribution of mitoxantrone to any of these tissues except for spleen. However, neither spleen weights nor lymphocyte counts were adversely affected by NaHCO(3) pretreatment, indicating that this co-therapy does not enhance myelosuppression due to mitoxantrone therapy. These findings suggest that metabolic alkalosis would produce a net gain in mitoxantrone therapeutic index.

Use of body surface area to calculate chemotherapeutic drug dose in dogs: II. Limitations imposed by pharmacokinetic factors

Anticancer drug dosages that specify the maximum dose and minimum dosing interval that are tolerated in a population of dogs are commonly recommended. Because the differences between the effective and toxic doses of most cancer chemotherapeutics is slight, it is important to achieve therapeutic concentrations in tumor tissues at the same time that concentrations in nontarget tissues are minimized. In order to determine the dosage regimen that will most likely accomplish these goals, similar drug concentrations must be achieved in all patients dosed according to a specific regimen. Dosing based on body surface area (BSA) is generally used in an effort to normalize drug concentrations. This is because it is well recognized that measures of many physiologic parameters that are responsible for drug disposition, including renal function and energy expenditure, can be normalized by use of BSA. However, there is substantial evidence that drug disposition is not always proportional to BSA. Differences in distribution, metabolism, and excretion pathways may preclude dose extrapolation among species or among individuals within a species based on BSA. Moreover, genetic differences in drug metabolism are well recognized in humans and in laboratory animals, and it is likely that similar differences exist among breeds of dogs. A review of the pharmacokinetic disposition of several cancer chemotherapeutics suggests that studies are needed to determine the most effective method to achieve equivalent anticancer drug concentrations in diverse veterinary patients.

Recent advances in the pharmacological control of experimental allergic encephalomyelitis (EAE) and the implications for multiple sclerosis treatment

The autoimmune, cell-mediated condition experimental allergic encephalomyelitis (EAE) is the representative model for the inflammatory central nervous system disease MS. EAE has been extensively employed to determine the efficacy of pharmacological agents that may be of ultimate use in the treatment of MS. A wide variety of drugs has been examined for activity in EAE but, over the last decade, three groups of compounds have emerged with clear and reproducible ability to modify significantly the onset and progression of the disease. The immunosuppressants, the modulators of catecholamine activity and the antineoplastic agents have convincingly altered the course of EAE and, as a consequence, provided understanding of the mechanisms of disease expression and offered further insight into the pathogenesis of MS. The article stresses the usefulness of EAE as a model to identify prospective pharmacological treatments for MS and, in particular, considers those compounds subsequently assessed for their ability to interfere with the progression of the human disease.

Characteristics of the inhibitory effect of mitoxantrone and pirarubicin on lung metastases of colon carcinoma 26

This study was performed to evaluate the antimetastatic activity of antitumor agents against metastatic colon carcinoma 26 (Co 26Lu), and to investigate their mechanisms of action. Pirarubicin demonstrated the most striking antitumor activity in mice bearing intravenously injected Co 26Lu cells. Etoposide and mitoxantrone also showed marked antitumor activity. Pirarubicin and mitoxantrone also exerted remarkable inhibitory effect on spontaneous lung metastases from subcutaneously implanted Co 26Lu. Pirarubicin showed marked inhibition of both primary tumor growth and lung metastases. Mitoxantrone was effective in preventing lung metastases even at doses that did not exhibit an antitumor effect on the primary tumor. Moreover, mitoxantrone administered two days after intravenous injection of tumor cells obviously reduced the number of lung colonies, while simultaneous injection of the drug did not inhibit colony formation. Mitoxantrone effectively inhibited angiogenesis on the chorioallantoic membrane at doses that did not affect the growth rate of embryos. These results suggest that mitoxantrone, besides its direct antitumor effect on tumor cells, may inhibit lung metastases by inhibiting angiogenesis.

Comparison of the "zero crossing" method in derivative spectroscopy and ultrafiltration for the determination of free and bound fractions of mitoxantrone

In vitro mitoxantrone binding to human serum, human serum albumin (HSA, 600 microM) and alpha-1-acid glycoprotein (AAG, 15 microM) was investigated by ultrafiltration and the first-derivative spectrophotometry based on the "zero crossing" method. The binding of mitoxantrone to isolated proteins was studied at eight concentrations whose range depended on the protein used. The results showed that mitoxantrone binding to human plasma and HSA involved a saturable binding. The AAG binding involved a saturable binding followed by a non saturable process. Within the concentration range studied, the percent and binding parameters which characterize the drug-protein interaction were comparable in both methods.

In vitro evaluation of acute effects of mitoxantrone (Novantrone) in rat and guinea pig atria

Since guinea pig and rat atria have been used as models to study acute anthracycline-induced cardiotoxicity, experiments were carried out in these preparations to evaluate possible acute cardiac effects mediated by mitoxantrone (MTX). After a latency period of approximately 90 min, MTX (10(-5)-10(-4) M) promoted a concentration-related and time-dependent decrease of spontaneous rate in guinea pig atria. A similar but less intense effect after a longer latency interval was observed in rat atria. In this preparation, MTX (10(-5)-10(-4) M) incubated up to 150 min., induced a gradual competitive beta-adrenergic blocking effect on the positive chronotropic action of isoproterenol. This was characterized by a progressive decline of pD2 values without altering Emax. A similar and stronger effect was found in isolated guinea pig atria incubated under same conditions with MTX, except that 10(-4) M exposed for 150 min. was able to depress the Emax to isoproterenol by 21.2%. In addition, MTX (10(-4) M) in this model promoted a non-competitive antagonistic effect on the chronotropic action of histamine. These data are compatible with the idea that MTX could induce cardiac acute effects qualitatively similar to but of lower potency than those produced by doxorubicin in these two models. In addition, guinea pig atria seemed to display higher sensitivity to MTX compared to rat atrial preparations.

Influence of polybutylcyanoacrylate nanoparticles and liposomes on the efficacy and toxicity of the anticancer drug mitoxantrone in murine tumour models

Polybutylcyanoacrylate (PBCA) nanoparticles were prepared and loaded with mitoxantrone, a highly effective anticancer drug. The proportion of mitoxantrone bound to the particles was analysed to be about 15 per cent of the initial drug concentration with the incorporation method and about 8 per cent with the adsorption method. Selected nanoparticle formulations were tested in leukaemia- or melanoma-bearing mice after intravenous injection. Efficacy and toxicity of mitoxantrone nanoparticles were compared with a drug solution and with a mitoxantrone-liposome formulation (small unilamellar vesicles with a negative surface charge). Furthermore, influence of an additional coating surfactant, poloxamine 1508, which has been shown to change body distribution of other polymeric nanoparticles, was investigated. It was shown that PBCA nanoparticles and liposomes influenced the efficacy of mitoxantrone in cancer therapy differently: liposomes prolonged survival time in P388 leukaemia, whereas nanoparticles led to a significant tumour volume reduction at the B16 melanoma. Neither nanoparticles nor liposomes were able to reduce the toxic side-effects caused by mitoxantrone, namely leucocytopenia. A slight additional influence of the coating surfactant was observed with only one preparation.

Control of immune-mediated disease of the central nervous system requires the use of a neuroactive agent: elucidation by the action of mitoxantrone

Mitoxantrone was used as an immunosuppressive probe to elucidate a means for the control of experimental allergic encephalomyelitis (EAE) induced in Biozzi AB/H mice following injection of spinal cord homogenate emulsified in Freund's adjuvant. A single i.p. injection of 2.5 mg/kg of mitoxantrone, 1-2 days before the anticipated onset of EAE, failed to prevent the majority of animals from developing clinical disease, whereas when the compound was injected directly into the central nervous system (CNS), at this time point, significantly increased therapeutic benefit was evident, with most animals failing to develop clinical EAE. Although the clinical use of intrathecal mitoxantrone is strongly contraindicated, these data suggest that increased therapeutic benefit may be achieved in immune-mediated disease of the CNS by targeting immunosuppressive doses of suitable agents, on lymphocyte activation within the CNS. In addition, direct administration of immunosuppressive doses into the CNS may reduce potentially unwanted (side) effects in the periphery.

Mitoxantrone. A review of its pharmacodynamic and pharmacokinetic properties, and therapeutic potential in the chemotherapy of cancer

Mitoxantrone is a dihydroxyanthracenedione derivative which as intravenous mono- and combination therapy has demonstrated therapeutic efficacy similar to that of standard induction and salvage treatment regimens in advanced breast cancer, non-Hodgkin's lymphoma, acute nonlymphoblastic leukaemia and chronic myelogenous leukaemia in blast crisis; it appears to be an effective alternative to the anthracycline component of standard treatment regimens in these indications. Mitoxantrone is also effective as a component of predominantly palliative treatment regimens for hepatic and advanced ovarian carcinoma. Limited studies suggest useful therapeutic activity in multiple myeloma and acute lymphoblastic leukaemia. Regional therapy of malignant effusions, hepatic and ovarian carcinomas has also been very effective, with a reduction in systemic adverse effects. Mitoxantrone inhibits DNA synthesis by intercalating DNA, inducing DNA strand breaks, and causing DNA aggregation and compaction, and delays cell cycle progression, particularly in late S phase. In vitro antitumour activity is concentration- and exposure time-proportional, and synergy with other antineoplastic drugs has been demonstrated in murine tumour models. Leucopenia may be dose-limiting in patients with solid tumours, whereas stomatitis may be dose-limiting in patients with leukaemia. Other adverse effects are usually of mild or moderate severity although cardiac effects, particularly congestive heart failure, may be of concern, especially in patients with a history of anthracycline therapy, mediastinal irradiation or cardiovascular disease. Mitoxantrone displays an improved tolerability profile compared with doxorubicin and other anthracyclines, although myelosuppression may occur more frequently. Thus, mitoxantrone is an effective and better tolerated alternative to the anthracyclines in most haematological malignancies, in breast cancer and in advanced hepatic or ovarian carcinoma. Further studies may consolidate its role in the treatment of these and other malignancies.

Evaluation of incorporation characteristics of mitoxantrone into unilamellar liposomes and analysis of their pharmacokinetic properties, acute toxicity, and antitumor efficacy

Mitoxantrone (MTO) was incorporated into small unilamellar liposomes by formation of a complex between the anticancer drug and negatively charged lipids. The complex was formed at a 2:1 molar ratio between the lipids and MTO, with phosphatidic acid (PA) being the strongest complex-forming lipid. Weaker complexes and lower incorporation rates of MTO resulted when liposomes containing dicetylphosphate, phosphatidyl inositol, phosphatidyl serine, phosphatidyl glycerol, oleic acid, and tridecylphosphate were used. Thus, all further experiments were performed with PA-MTO liposomes that contained 0.1-3 mg MTO/ml and had mean vesicle sizes of 40-150 nm, depending on the drug concentration and the method of liposome preparation. In vitro incubations of free and liposomal MTO with human plasma showed that the drug is slowly transferred from the liposome membranes to the plasma proteins. For liposomal MTO a transfer rate of 48% was determined, whereas 75.8% of free MTO was bound to the plasma proteins. The organ distribution of the two preparations in mice showed that higher and longer-lasting concentrations of liposomal MTO were found in the liver and spleen. The terminal elimination halflives in the liver were 77 h for liposomal MTO and 14.4 h for free MTO. In the blood, slightly higher concentrations were detected for liposomal MTO, which also had slower biphasic elimination kinetics as compared with the free drug. Drug distribution in the heart was not significantly different from that in the kidneys. The LD25 of PA-MTO liposomes in mice was 19.6 mg/kg and that of free MTO was 7.7 mg/kg. The antitumor effects of PA-MTO liposomes were evaluated in murine L1210 leukemia, in various xenografted human tumors, and in methylnitrosourea-induced rat mammary carcinoma. Generally, the liposomal application form was more effective and less toxic than the free drug. The cytostatic effects were dependent on the tumor model, the application schedule, and the drug concentration. At doses that were toxic when free MTO was used, the liposomal preparation produced strong antitumor effects in some cases. In summary, the incorporation of MTO into liposomes changes the drug's plasma-binding properties, alters its organ distribution, reduces its acute toxicity, and increases its cytostatic efficiency in various tumor models. The liposomal PA-MTO complex represents a new application form of MTO that has advantageous properties.

Suppression of demyelination by mitoxantrone

The mode of action of the immunosuppressant mitoxantrone was examined in murine models of demyelinating disease. The drug has been shown to block antigen induced proliferative activity and to inhibit myelin degradation by leucocytes from paralysed mice. Mitoxantrone blocked myelin breakdown by macrophages although phagocytosis was not affected. Further evidence was obtained to indicate that mitoxantrone acts therapeutically in reducing, or at high dose, preventing signs of EAE developing in mice immunized with spinal cord homogenate and Freund's complete adjuvant. Mitoxantrone also significantly inhibited the incidence of relapse when treatment was initiated during the post-acute remission period.

Direct determination of mitoxantrone and its mono- and dicarboxylic metabolites in plasma and urine by high-performance liquid chromatography

The simultaneous isolation and determination of mitoxantrone (Novantrone) and its two known metabolites (the mono- and dicarboxylic metabolites) were carried out using a high-performance liquid chromatographic (HPLC) system equipped with an automatic pre-column-switching system that permits drug analysis by direct injection of biological samples. Plasma or urine samples were injected directly on to an enrichment pre-column flushed with methanol-water (5:95, v/v) as the mobile phase. The maximum amount of endogenous water-soluble components was removed from biological samples within 9 min. Drugs specifically adsorbed on the pre-column were back-flushed on to an analytical column (Nucleosil C18, 250 X 4.6 mm I.D.) with 1.6 M ammonium formate buffer (pH 4.0) (2.5% formic acid) containing 20% acetonitrile. Detection was effected at 655 nm. Chromatographic analysis was performed within 12 min. The detection limit of the method was about 4 ng/ml for urine and 10 ng/ml for plasma samples. The precision ranged from 3 to 11% depending on the amount of compound studied. This technique was applied to the monitoring of mitoxantrone in plasma and to the quantification of the unchanged compound and its two metabolites in urine from patients receiving 14 mg/m2 of mitoxantrone by intravenous infusion for 10 min.

Pharmacokinetics of mitoxantrone in humans following single-agent infusion or intra-arterial injection therapy or combined-agent infusion therapy

This study describes the pharmacokinetics of mitoxantrone determined by a sensitive and specific HPLC-method. The time-concentration curves of i.v.-treated patients (15 mg/m2 over 30 min) correspond to a three-compartment model with a T1/2 alpha of 12 min, a T1/2 beta of 93 min, and a slow elimination phase of 36 h. The central compartment volume was 26.22 and the distribution volume, 1381.9. The mean urinary excretion was 4.9% of the total dose. The pharmacokinetic parameters were also defined in five patients who were treated with combination chemotherapy (mitoxantrone 12 mg/m2, methotrexate 30 mg/m2 and vincristine 2 mg). These results were not different from those with the single-drug treatment, except for the volume of the central compartment, which was significantly decreased. The peak levels after hepatic arterial infusion of mitoxantrone were three times lower than those after the identical dose given i.v. to the same patient. Pleural fluid sampling showed a six-fold increase compared with the plasma level (12 ng/ml versus 2 ng/ml). A multiple linear regression analysis of the data revealed correlations between the pharmacokinetic results and some of the baseline parameters. It is possible to predict changes in the kinetic behaviour of mitoxantrone on the basis of these relations but on the other hand toxicity is less predictable from the baseline parameters or from the pharmacokinetic results.