An investigation of the cytotoxicity of the morpholino anthracycline MX2 against glioma cells in vitro.

MX2 is a novel morpholino anthracycline reported to have lower systemic toxicity than other anthracyclines. It has similar antitumour activity to adriamycin and is cytotoxic towards multi-drug resistant cells and anthracycline sensitive sublines of human and murine tumour cells. In this study MX2 showed a marked cytocidal effect compared to M2, the most cytotoxically active metabolite, and the nitrosourea, BCNU, when 30 ng/ml of each drug was added to separate flasks of C6 glioma cells grown in monolayer. The colony formation of C6 glioma cells was markedly inhibited by MX2 in a dose dependent manner. The LD50 values for MX2, M2 and BCNU were 10.5 ng/ml, 15.8 ng/ml and 465 ng/ml respectively. MX2 is likely to be bound to the main plasma protein, albumin, and can also interact with the plasma lipoproteins, particularly high density lipoprotein. The results in this study strongly support the further investigation of MX2 as a potential chemotherapeutic agent against brain tumours.

In vitro binding of MX2 (KRN8602) and epirubicin to human plasma protein.

This study compares the human plasma protein binding characteristics of MX2 and epirubicin. The binding characteristics were determined by equilibrium dialysis at various concentrations of the drugs. The binding dissociation constant (Kd), binding capacity (Bmax) and partitioning constant (Kp) were obtained by Scatchard analysis of the free and bound drugs in the dialysis compartments. Our results have demonstrated that plasma protein binds epirubicin or MX2 in an unsaturable appearance over the concentration up to 150 mumol/l. At the same concentrations, plasma protein binds more epirubicin than MX2. The nature of the interaction may consist of two classes of specific binding, and a partitioning. The binding dissociation constants were 18 and 17.5 mumol/l for the higher binding class (Kd1) and 315.8 and 316.9 mumol/l for the lower binding class (Kd2), respectively, for epirubicin and MX2. The respective maximum binding capacities (Bmax) of plasma protein for epirubicin and MX2 were significantly different, 0.045 and 0.029 mumol/g protein for the higher binding class (Bmax1), and 0.39 and 0.29 mumol/g protein for the lower binding class (Bmax2). The partitioning constants (Kp) were 21.5 x 10(-5) and 20 x 10(-5) litres/g protein for epirubicin and MX2, respectively. The results suggest that plasma protein binds epirubicin or MX2 with a similar affinity, but has less binding sites for MX2. One contributing mechanism to the difference in activity noted between epirubicin and MX2 may be changes in free drug fractions.

One-electron reduction of an anthracycline antibiotic carminomycin by a human erythrocyte redox chain.

Human erythrocyte membranes catalyse the NAD(P)H-dependent generation of the semiquinone of an adriamycin-type antibiotic carminomycin under anaerobic conditions. The maximal yield of the antibiotic radical is about 4-fold higher in the presence of NADPH than of NADH. The possible significance of the antibiotic reduction to the semiquinone by a human erythrocyte membrane redox chain for the clinical usage of these antibiotics is discussed.

[Determination of carminomycin and its basic metabolite 13-dihydrocarminomycin by a highly efficient liquid chromatographic method with a fluorescent detector]. / Opredelenie karminomitsina i ego osnovnogo metabolita 13-digidrokarminomitsina metodom vysokoéffektivnoi zhidkostnoi khromatografii s fliuorestsentnym detektorom.

Carminomycin, an antitumor antibiotic, and 13-dihydrocarminomycin, its main metabolite, were determined in the blood plasma of patients with highly efficient liquid chromatography and a fluorescent detector (lambda ex=492 nm, lambda em=538 nm). The liquid chromatograph manufactured by Spectro-Physics, model SP-8000, with Particyl Column 10/25 was used for the determination. The composition of the mobile phase of acetonitrile--0.1 M H3PO4 was 93:7 by the volume. The mobility speed was 2 ml/min. The retention time of carminomycin, rubomycin (used as the national standard) and dihydrocarminomycin was 6.8, 8 and 10.2 minutes, respectively. All three substances showed symmetrical peaks with high resolution. The early phase kinetics of carminomycin after its intravenous injection to the patients in a dose of 24 mg (18 mg/m2) is satisfactorily described by the diexponential equation. The pharmacokinetic parameters of carminomycin corresponding to the open two-compartmental system are presented. Highly efficient liquid chromatography may be used for the pharmacokinetic description of biotransformation of carminomycin and some other antibiotics of the anthracycline group.

A phase I and clinical pharmacology study of intravenously administered carminomycin in cancer patients in the United States.

Carminomycin (CMN) was administered i.v. to 44 patients with a variety of nonhematological cancers every 4 weeks at doses of 15, 20, 22.5, and 25 mg/sq m. Granulocytopenia was the dose-limiting toxicity. The median granulocyte count for previously untreated patients receiving 22.5 mg/sq m was 0.962 cells/microliters, and for previously treated patients receiving 20 mg/sq m it was 0.420 cell/microliters. Moderate to severe phlebitis was associated with drug administration in 50% of cases. Nausea, vomiting, and alopecia were mild. Three of nine patients who received a total CMN dose of greater than or equal to 100 mg/sq m (mean, 132 mg/sq m) developed unexplained decreases in radionuclide cardiac ejection fraction, with one patient developing decreased QRS amplitude and congestive heart failure at a total dose of 160 mg/sq m. CMN is rapidly metabolized to carminomycinol. The elimination half-lives of CMN and carminomycinol are 6 to 10 and 50 hr, respectively. CMN was found to be a more potent inhibitor of human granulocyte-macrophage colony-forming units than was carminomycinol. Objective partial responses were seen in two of seven previously untreated patients with non-small cell lung cancer and one of three patients with squamous cell carcinoma of the head and neck previously untreated with chemotherapy.

Plasma concentrations of carminomycin and carminomycinol in man, measured by high pressure liquid chromatography.

In 9 patients with advanced malignant disease who received carminomycin (CMM) in an i.v. bolus injection (dose 18 mg/m2), curves of plasma concentrations of CMM and carminomycinol (CMMOH), a metabolite, versus time were constructed. For determination of plasma concentrations, high pressure liquid chromatography was used. For CMM and CMMOH the median areas under the curves (AUC's) were 31 (range 4-57) X 10(-8) mol/Ql/hr (measured over 24 hr) and 100 (range 309-158) X 10(-8) mol/l/hr (measured over 48 hr) respectively. From the data an accumulation of CMMOH in patients receiving treatments separated by brief intervals ban be predicted (half-life time of plasma disappearance for CMMOH was 2 days). Clinical toxicity was lowest in those 3 patients showing the lowest AUC for both CMM and CMMOH.

Analysis of carminomycin in human serum by fluorometric high-performance liquid chromatography.

A method is given for the determination of carminomycin (CMM) and a major metabolite carminomycinol (CMMOH) in serum from cancer patients after intravenous administration of carminomycin as the free drug. CMM and CMMOH are extracted from serum with chloroform, the extract evaporated and the residue dissolved in methanol. High performance liquid chromatography analysis utilized a C18 microBondapak reversed-phase column eluted with 0.1 mol/l acetate buffer (pH 4)-acetonitrile (60:40, v/v) with fluorescence detection. The assay is linear, reproducible, and precise with a limit of detection of 2 ng/ml. Representative serum levels of CMM and CMMOH in a cancer patients are presented.

Pharmacokinetics of carminomycin in dogs and humans. Preliminary report.

Carminomycin was administered to four dogs and two human patients as a single intravenous dose. Plasma samples were obtained and assayed for carminomycin and carminomycinol by high pressure liquid chromatography with fluorescence detection. The plasma disappearance of carminomycin could be described by a three-compartment open model. Distribution was rapid and the apparent volume of distribution was greater than 100 l/m2 in both species. The terminal half-life of drug was 86 h in dogs and 20 h in humans. In both dogs and humans carminomycinol concentrations rapidly surpassed carminomycin levels, and terminal half-lives were longer than for the parent compound in the two species. Since carminomycinol has antitumor activity and host toxicity, this metabolite may play an important role in the efficacy and toxicity of carminomycin therapy.

[Acute toxicity of carminomycin administered perorally to laboratory animals]. / Izuchenie ostroi toksichnosti karminomitsina pri peroral'nom vvedenii laboratornym zhivotnym.

Rather high species sensitivity to carminomycin was found in the experiment with albino mice, rats, guinea pigs, rabbits and dogs. The highest difference in the antibiotic toxicity for various species of the laboratory animals was shown on oral administration of the drug which was due to the differences in the antibiotic absorption from the gastro-intestinal tract. On single oral administration to the dogs in toxic or lethal doses the antibiotic suppressed the blood formation up to aplasia of the bone marrow. The equitoxic doses of carminomycin on its single oral and intravenous administration differed approximately by 3 times. Carminomycin had no effect on the smooth muscles of the isolated rabbit ear vessels and cat intestine in situ. The antibiotic had an irritating effect on the rabbit eye mucosa. Carminomycin had no skin-irritating effect.