Differential antifungal activity of isomeric forms of nystatin.

When nystatin is placed in RPMI and other biological fluids, there is loss of pure nystatin, with the development of two distinguishable chromatographic peaks, 1 and 2. Peak 1 appears identical to commercially prepared nystatin. By nuclear magnetic resonance (NMR) and mass spectral analysis, peak 2 appears to be an isomer of peak 1. The isomers are quantitatively and fully interconvertible. Formation of peak 2 is accelerated at a pH of >7.0 and ultimately reaches a near 55:45 (peak 1/peak 2 ratio) mixture. We sought to determine the relative activities of peaks 1 and 2 against Candida spp. Peak 2 consistently showed higher MICs when it was the predominant form during the experiment. Time-kill analyses showed that peak 2 required > or =8 x the concentration of peak 1 to produce a modest and delayed killing effect, which was never of the same magnitude as that produced by peak 1. In both types of assays, the activity of peak 2 corresponded with intra-assay formation of peak 1. Both MIC measurements and time-kill analysis suggest that peak 2 has considerably less activity, if any at all, against Candida spp. Peak 2 may serve as a reservoir for peak 1.

Pharmacokinetics and distribution of a 33P-labeled anti-human immunodeficiency virus oligonucleotide (AR177) after single- and multiple-dose intravenous administration to rats.

AR177 is a 17-mer oligonucleotide that has anti-human immunodeficiency virus activity in vitro. The disposition of internally labeled 33P-AR177 was studied after the tail vein injection of single and multiple doses (0.7 mg/kg) to rats. After a single dose, the terminal half-life of AR177 in the blood and plasma was 367 and 271 hr, respectively, significantly longer than values reported for other oligonucleotides. Analysis of the AR177 tissue distribution showed that the majority of the dose was distributed to the liver (40%), bone marrow (17%) and renal cortex (15%) at 8 hr after single dosing. Analysis of the AR177 concentrations in tissues showed that the highest concentrations were achieved in the renal cortex (15.0 microg-eq/g), liver (7.4 microg-eq/g), bone marrow (3.9 microg-eq/g), mesenteric lymph node (3.0 microg-eq/g) and spleen (2.4 microg-eq/g) at 8 hr after single dosing. The half-life in these tissues was 9.6, 7.7, 36.8, 10.0 and 30.8 days, respectively. Forty-eight hours after the last of seven i.v. doses given every other day, the concentrations in tissues were as follows: renal cortex, 39.9 microg-eq/g; liver, 33.9 microg-eq/g; bone marrow, 12.7 microg-eq/g; spleen, 9.3 microg-eq/g; mesenteric lymph node, 5.1 microg-eq/g. Twenty-one days after administration of the last dose, tissue concentrations were still high, as follows: renal cortex, 18.6 microg-eq/g; liver, 6.2 microg-eq/g; bone marrow, 12.5 microg-eq/g; mesenteric lymph node, 3.9 microg-eq/g; spleen, 8.1 microg-eq/g. There was low urinary and fecal excretion (urinary excretion of 12.8% and fecal excretion of 6.0% of the total dose over 21 days) after a single dose. Gel filtration and anion-exchange high-performance liquid chromatography and electrophoretic analysis of the radioactivity in tissues indicated that >90% of the radioactivity represented intact AR177 for at least 7 days after drug dosing. These results demonstrate that AR177 has an extended plasma, blood and tissue half-life, is widely distributed and achieves high concentrations in lymphoid and nonlymphoid tissues in rats.

Single-dose hemodynamic toxicity and pharmacokinetics of a partial phosphorothioate anti-HIV oligonucleotide (AR177) after intravenous infusion to cynomolgus monkeys.

5' GTGGTGGGTGGGTGGGT-3' (AR177) is a 17-mer oligonucleotide with anti-human immunodeficiency virus (HIV) activity that is composed of a phosphodiester backbone and single phosphorothioate linkages at the 3' and 5' ends. A hemodynamic toxicity study was conducted in which cynomolgus monkeys were infused i.v. over a 10-minute period with single doses of 5, 20 or 50 mg AR177/kg or saline. Blood pressure, ECG, clinical chemistry, hematology, complement factors, coagulation parameters and the AR177 plasma concentration were determined. AR177 did not cause any mortality in this study, nor did it cause changes in blood pressure, ECG, clinical chemistry or hematology parameters at any dose. There was a minimal, dose-dependent increase in the levels of complement split product Bb and total hemolytic complement. There was a significant dose-dependent and reversible inhibition of coagulation with the 20- and 50-mg/kg doses that lasted up to several hours after infusion. The time course of the inhibition of coagulation closely matched the plasma levels of AR177. There was a no-effect plasma AR177 concentration vs. activated partial thromboplastin time of approximately 60 to 100 micrograms AR177/ml, above which there was prolongation of activated partial thromboplastin time. These data demonstrate that AR177 does not cause significant hemodynamic toxicity at the doses studied and that this drug could be administered as a rapid infusion without any acute, life-threatening effects at doses that produce plasma concentrations that have shown anti-HIV activity in vitro.

Repeat-dose toxicity and pharmacokinetics of a partial phosphorothioate anti-HIV oligonucleotide (AR177) after bolus intravenous administration to cynomolgus monkeys.

5'GTGGTGGGTGGGTGGGT-3' (AR177) is a partial phosphorothioate, 17-mer oligonucleotide that has been shown to have anti-human immunodeficiency virus (HIV) activity in vitro and to be a potent inhibitor of HIV-1 integrase. A repeat-dose toxicity and pharmacokinetic study was conducted in which cynomolgus monkeys were given bolus i.v. injections of 2.5, 10 or 40 mg AR177/kg/day every other day for a total of 12 doses. Control monkeys received saline. ECG, clinical chemistry, hematology, coagulation parameters, histopathology and the AR177 plasma concentration were evaluated. AR177 did not cause any mortality in this study, nor did it cause changes in ECG, clinical chemistry, hematology values or histology. However, there was a dose-dependent inhibition of coagulation measured by a prolongation of activated partial thromboplastin time; this inhibition was reversible with drug washout. Analysis of plasma samples by HPLC demonstrated that there was no difference between the AR177 plasma concentrations that were achieved after the 1st and 12th (last) doses of 2.5, 10 or 40 mg/kg. There was a direct relationship between the AR177 plasma concentration and activated partial thromboplastin time. These results indicate that repeated bolus i.v. administration of AR177 to cynomolgus monkeys at doses as high as 40 mg/kg was well tolerated and was not associated with the serious cardiovascular responses previously observed with other oligonucleotides administered i.v.