Determination of the antileukemic drug mitoguazone and seven other closely related bis(amidinohydrazones) in human blood serum by high-performance liquid chromatography

A reversed-phase (C18) HPLC method with diode-array detection was developed for the separation and determination of methylglyoxal bis(amidinohydrazone) (mitoguazone) and seven closely related aliphatic analogs thereof, namely the bis(amidinohydrazones) of glyoxal, dimethylglyoxal, ethylmethylglyoxal, methylpropylglyoxal, butylmethylglyoxal, diethylglyoxal and dipropylglyoxal. The mobile phase consisted of a non-linear binary gradient of methanol and 0.03 M aqueous sodium acetate buffer (pH 4.3). Good separation of the eight congeners was achieved. On increasing the methanol content of the eluent, the bis(amidinohydrazones) eluted in the order of increasing number of carbon atoms in the side-chains. The method was also applied to the quantitative analysis of the compounds in aqueous solution and, combined with ultrafiltration, for the separation of the eight congeners in spiked human blood serum. A separate simplified method for the quantitative determination of each of the compounds in spiked human blood serum samples was also developed. The methods developed made for the first time possible the simultaneous HPLC analysis of more than one bis(amidinohydrazones). The results obtained indicate that the bis(amidinohydrazones) studied obviously have a distinct tendency to form ion associates with acetate ions and probably also other carboxylate ions in aqueous solution. This aspect may be of biochemical significance, especially concerning the intracellular binding of the compounds. Each one of the compounds studied invariably gave rise to one peak only, this result supporting the theory that the conventional synthesis of each of the compounds gives rise to one geometrical isomer only. This result is completely in agreement with the results of previous proton and carbon NMR spectroscopic as well as X-ray diffraction studies.

High-performance liquid chromatographic method for guanylhydrazone compounds

A high-performance liquid chromatographic method has been developed for a series of aromatic guanylhydrazones that have demonstrated therapeutic potential as anti-inflammatory agents. The compounds were separated using octadecyl or diisopropyloctyl reversed-phase columns, with an acetonitrile gradient in water containing heptane sulfonate, tetramethylammonium chloride, and phosphoric acid. The method was used to reliably quantify levels of analyte as low as 785 ng/ml, and the detector response was linear to at least 50 micrograms/ml using a 100 microliters injection volume. The assay system was used to determine the basic pharmacokinetics of a lead compound, CNI-1493, from serum concentrations following a single intravenous injection in rats.

[Kinetics of the transformation of dihydroambazone into ambazone]

The oxidation of dihydroambazone (1) by oxygen is dependent on the pH-values of the solutions used. This transformation can be inhibited and excluded, respectively, by ascorbic acid using defined concentrations. The oxidation product ambazone (2) was determined spectroscopically at different pH-values. The rate of transformation in serum depends on the temperature and can also be inhibited with ascorbic acid.

Chemical-analytical characterization of dihydroambazone

Important properties of p-(thiosemicarbazido)diamino-methylen-hydrazino benzene (1; dihydroambazone) are described. The transformation of this compound into 1,4-benzoquinone guanylhydrazone thiosemicarbazone (2; ambazone) dependent on different aqueous buffer systems was investigated. The spectroscopic behaviour of the transformation product allows us to determine the content of the compound in aqueous solutions, whereas the determination in serum is much more difficult. Furthermore, TLC experiments and oxidation methods are described.

Rapid analysis for methylglyoxal bis(guanylhydrazone) by reversed-phase ion-pair liquid chromatography

We describe a "high-performance" reversed-phase ion-pair liquid-chromatographic procedure for measuring methylglyoxal bis(guanylhydrazone) (MGBG) in plasma, urine, and bone-marrow leukocytes. Specimens of plasma and bone-marrow leukocytes are deproteinized with perchloric acid, then neutralized with KOH. Urinary MGBG is isolated by liquid-solid extraction in a C18 Sep-Pak. The chromatographic system consists of a 45 X 4.6 mm (i.d.) octadecylsilyl (C18, 5-microns particle) column and a mobile phase consisting of methanol/sodium acetate buffer (200 mmol/L, pH 4.5), 2/3, by vol. The acetate buffer also contains 20 mmol of 1-octanesulfonate and 40 mg of sodium azide per liter. The column effluent is monitored at 283 nm. At a flow rate of 3.0 mL/min, MGBG is eluted in 1.67 min. The detection limit is 20 nmol/L, and peak height varies linearly with concentration from 0.02 to 40 mumol/L. Analytical recovery exceeds 99%. Within-day CVs ranged from 0.9% to 2.9%, between-day CVs from 4.2% to 6.2%.

Inhibition of S-adenosylmethionine decarboxylase and diamine oxidase activities by analogues of methylglyoxal bis(guanylhydrazone) and their cellular uptake during lymphocyte activation

Several congeners of methylglyoxal bis(guanylhydrazone) were tested for their ability to inhibit eukaryotic putrescine-activated S-adenosylmethionine decarboxylase (EC 4.1.1.50) and intestinal diamine oxidase (EC 1.4.3.6). All the compounds tested, namely methylglyoxal bis(guanylhydrazone), ethylglyoxal bis(guanylhydrazone), dimethylglyoxal bis(guanylhydrazone) and the di-N"-methyl derivative of methylglyoxal bis(guanylhydrazone), were strong inhibitors of both yeast and mouse liver adenosylmethionine decarboxylase activity in vitro. The enzyme from both sources was most powerfully inhibited by ethylglyoxal bis(guanylhydrazone). All the diguanidines likewise inhibited diamine oxidase activity in vitro. The maximum intracellular concentrations of the ethyl and dimethylated analogues achieved in activated lymphocytes were only about one-fifth of that of the parent compound. However, both derivatives appeared to utilize the polyamine-carrier system, as indicated by competition experiments with spermidine.

Dialyzability of methyl-GAG

Methyl-GAG at low doses was administered to an anephric male patient with metastatic hypernephroma, who required hemodialysis. No toxicity was observed. Measurement of serum levels of methyl-GAG showed that the drug is dialyzable. Thus, when methyl-GAG is considered for patients who are anephric and are being dialyzed, full doses are allowable. In addition, dialysis should be effective in rapidly eliminating the drug in patients who develop toxic effects.

Pharmacokinetic study of methyl glyoxal-bis-guanylhydrazone (methyl-GAG)

Using a paired ion exchange high pressure liquid chromatographic assay, pharmacokinetic evaluation of methyl glyoxal bis guanylhydrazone (methyl-GAG) was performed in nine male New Zealand albino rabbits following administration of a single intravenous bolus dose of 50 mg/kg B.W (550 mg/m2 BSA). Blood samples were collected before and at intervals of 5, 10, 15, 30 min and 1, 2, 3, 4, 6, 8, 12, 18, and 24 h after administration of the drug. The analysis of experimental data indicates a three compartment open model with first order elimination from the central compartment described by the equation Cpt = A.e-alpha t + B.e-beta t + C.e-gamma t, where A, B, C, are 107.985, 4.785, and 0.763 micrograms/ml, respectively. alpha, beta, gamma, are 5.466, 0.487, and 0.030 h-1, respectively, and T1/2 alpha, beta, gamma are 7.6, 85.3 min and 23.1 h, respectively. The mean volume of distribution in the central compartment Vc was 0.44 liters (1)/kg, volume of distribution Vdarea 30.326 1/kg, and the total body clearance 0.9097 1/kg/h. The existence of a long terminal plasma half life of methyl-GAG reported previously in human studies was also confirmed in experimental animals and may explain the cumulative toxicity of this drug.

A gas chromatographic and mass spectral approach to the analysis of the anticancer drug methyl-G as the trimethylsilyl derivative

Methyl-G was analyzed by gas chromatography and mass spectrometry after trimethylsilylation. A means of quantitatively measuring methyl-G by gas chromatography of the TMS derivative is presented using the analogous derivative of methylethyl-G as an internal standard. The value of this compound as an internal standard for measurements of methyl-G is discussed based on comparisons of the mass spectral and gas chromatographic properties of their derivatives as well as their similar behavior in the ion exchange method used for partial purification. The latter procedure is discussed in some detail, and the results of applying it to biological samples of human and cell culture origin are presented.

Plasma levels and urinary excretion of methyl-GAG following iv infusion in man

The pharmacokinetics of methyl-GAG was studied after nephrectomy in five patients with renal cell carcinoma and in one patient with breast cancer. Following rapid infusion (30 minutes) of 700 mg/m2 of methyl-GAG, terminal half-life of 136-224 hours. Drug levels declined to 6%-20% of the initial plasma concentration in the first 24 hours. Approximately 40% of the dose was recovered in the urine after 2 weeks. Extensive extravascular distribution of methyl-GAG is suggested.

Quantitation of methylglyoxal bis(guanylhydrazone) in blood plasma and leukemia cells of patients receiving the drug

Methylglyoxal bis(guanylhydrazone), a cytostatic compound which apparently interferes with the metabolism and/or functions of the natural polyamines (spermidine and spermine), was effectively taken up by cultured human lymphocytic leukemia cells, rapidly resulting in the formation of a concentration gradient of up to 1,000-fold across the cell membrane in cells grown in the presence of micromolar concentrations of the drug. For an anti-proliferative effect on the leukemia cells, an intracellular concentration of more than 0.5 mM was required. The uptake of methylglyoxal bis(guanylhydrazone) was critically dependent on the growth rate of the leukemia cells. Low intracellular concentrations of the drug were present in cells growing slowly, whereas in rapidly dividing cells the intracellular concentration of the drug approached 5mM. When given as repeated intravenous infusions to two leukemic children, methylglyoxal bis(guanylhydrazone) exhibited sharp and transient peaks of plasma concentration, the drug having an apparent half-life in plasma of only 1-2 h. However, as in cultured cells, the drug was rapidly concentrated in the leukemia cells, reaching concentrations that were distinctly anti-proliferative. In contrast to the rapid disappearance of methylglyoxal bis(guanylhydrazone) from plasma, the circulation leukemia cells retained the drug for a period of several days with only minimal decrease in the initial concentrations. Methylglyoxal bis(guanylhydrazone) was given to the patients for 1 to 2 months as intravenous infusions, the timing of which was determined by regular assays of the drug concentrations in the leukemia cells. In agreement with the results obtained with the cultured cells, and intracellular concentration of about 0.5 to 1mM was apparently required for growth-inhibitory action to occur. Regular determination of the cellular drug concentrations indicated that methylglyoxal bis(quanylhydrazone) could be given as weekly infusions. This treatment schedule represents much lower dosing of the drug than the earlier daily regimens which were commonly associated with unacceptable toxicity.

Determination of methylglyoxal-bis(guanylhydrazone) in body fluids by ion-pair chromatography

Methylglyoxal-bis(guanylhydrazone), Methyl-G, is a potent antineoplastic agent currently undergoing Phase l clinical trials. Serum, ascitic and pleural fluids, and urine are deproteinized with methanol, supernatant is evaporated, residue is redissolved in the eluent, lipids are removed with carbon tetrachloride, and an aliquot of the aqueous layer injected into the chromatograph. Ethylglyoxal-bis(guanylhydrazone) (Ethyl-G) is the internal standard. The mobile phase is a mixture of an aqueous buffer (containing 0.004 M heptane and pentane sulfonic acid, 90%:10%, buffered to pH 3.5) and methanol (68%:32%). The ion-pair complex is retained on a micro Bondapak C18 column, eluted with a flow of 2.0 mL/min. Absorbance is measured at 280 nm. Detectability: 30 ng/mL (0.11 micro M) in serum, ascitic and pleural fluids, 300 ng/mL (1.1 micro M) in urine. Calibration curves (peak height ratios of Methyl-G/Ethyl-G plotted against known drug concentrations) were linear in the 0.1-30 microg/mL range. Correlation coefficinets were 0.999; coefficients of variation for reproducibility were less than 5%. Residual blood levels of Methyl-G persist for several days. Methyl-G was found to pass into ascitic fluid.

High-performance liquid chromatographic assay for methylglyoxal bis(guanylhydrazone) (methyl GAG) in plasma and urine

A clinically useful analytical method is described for monitoring both plasma and urine levels of methylglyoxal bis(guanylhydrazone) administered in the clinical management of certain neoplasms. The drug is initially separated from the biological matrix by retention on a small (2 cm) column packed with weak cation-exchange resin. The analyte is subsequently eluted quantitatively from the column with hydrochloric acid, and then separated and quantitated by paired ion high-performance liquid chromatography on an RP-18 column. The drug is detected to levels of 50 ng/ml of biological fluid by monitoring the column effluent spectrophotometrically at 280 nm. Absorbance was linearly related to drug concentration over the range 50 ng-50 microgram/ml of plasma or urine, and measurements could be made with a precision of +/- 4% over this range.