Oral anti-pneumococcal activity and pharmacokinetic profiling of a novel peptide deformylase inhibitor.

OBJECTIVE: BB-81384, a novel peptide deformylase (PDF) inhibitor, was characterized in terms of enzyme inhibition profile, antibacterial activity, rodent pharmacokinetics and oral efficacy in murine infection models. METHODS: MICs were determined by standard NCCLS broth microdilution. Selectivity of metalloenzyme inhibition was determined with a limited panel of enzymes via standard biochemical assays. Profiling of the pharmacokinetics and select tissue disposition in mice was determined and compared with that of the macrolide, azithromycin. In vivo murine efficacy studies using Streptococcus pneumoniae were conducted using a peritonitis model, as well as lung and thigh burden models of infection. RESULTS: BB-81384 selectively inhibited PDF with an IC(50) approximately 10 nM and with MICs < 0.5 mg/L against most S. pneumoniae pathogens. Pharmacokinetic analysis revealed good oral bioavailability and moderate clearance and volume of distribution. BB-81384 partitioning to lung tissue was similar in terms of magnitude and kinetics to that of the plasma compartment. Single-administration oral efficacy in a mouse peritonitis model was evident with an ED(50) of 30 mg/kg. BB-81384 reduced the bacterial load by approximately 5 and 3 log units in organ-burden models of lung and thigh infection, respectively. CONCLUSION: BB-81384, a novel PDF inhibitor with good activity against S. pneumoniae in vitro, was the first compound of this class to be profiled for oral pharmacokinetics and tissue disposition and to demonstrate oral anti-pneumococcal efficacy in mice.

Analysis of 2beta-carbomethoxy-3beta-(4-fluorophenyl)-N-(3-iodo-E-allyl)nortropane in rat plasma. II. Pharmacokinetic profile in male and female Sprague-Dawley rats evaluated by capillary electrophoresis.

This paper describes a pharmacokinetic study performed in Sprague-Dawley rats after i.v. administration of a single 6-mg/kg dose of 2beta-carbomethoxy-3beta-(4-fluorophenyl)-N-(3-iodo-E-allyl)nortropane (Altropane). Plasma samples were collected from the retro-orbital sinus at times up to 3 h after drug administration, extracted by solid-phase extraction, and the drug levels determined by capillary electrophoresis (CE). Pharmacokinetic parameters were determined by a standard noncompartmental model using WinNonlin version 1.5. The maximum plasma concentrations, clearances of the drug, and areas under the curve for male and female rats were 5.74 and 7.26 microg/ml, 135.7 and 98.5 ml/kg x min, and 44.23 and 60.92 microg x min/ml, respectively. The drug was cleared very rapidly from the systemic circulation, with a terminal t(1/2) of 7 to 10 min and a mean residence time of about 11 min for both sexes. The volume of distribution was approximately 1 l/kg. No metabolites were detected when the samples were analyzed individually. However, after samples were pooled and concentrated, traces of two unknown peaks that may represent metabolites were detected in concentrates from the last two timepoints. Part I of this work [J. Chromatogr. A, 895 (2000) 87] describes validation of CE methods for the analysis of aqueous and plasma samples of Altropane, including its solid-phase extraction from rat plasma.

Contradistinction between doxorubicin and epirubicin: in-vivo metabolism, pharmacokinetics and toxicodynamics after single- and multiple-dosing in rats.

There is compelling in-vitro evidence that the evaluation of doxorubicin or epirubicin pharmacokinetics based solely on plasma concentration may not fully elucidate the differences between the two drugs. Both compounds bind to erythrocytes and their different binding to haemoglobin may influence their disposition in the body. The purpose of the present study was to compare the pharmacokinetics and metabolism of doxorubicin and epirubicin based on the plasma concentration, amount associated with blood cells and simultaneous monitoring of biliary and urinary elimination of unchanged drug and metabolites after single- and multiple-dose injections. The level of sarcoplasmic reticulum Ca2+ATPase in the heart was also measured as a biomarker of cardiotoxicity. Male Sprague-Dawley rats were treated in a parallel design with doxorubicin or epirubicin on a multiple-dosing basis (4 mg kg(-1) per week) or as a single dose injection (20 mg kg(-1)). Blood, urine and bile samples were collected periodically after each dose in the multiple-dosing regimen and the single dose injection, and at the end of each experiment the hearts were removed. The concentrations of each drug in plasma, blood cells, bile and urine samples were determined, and by simultaneous curve-fitting of plasma and bile data according to compartmental analysis, the pharmacokinetic parameters and constants were estimated. The concentration of drug associated with blood cells was analysed according to non-compartmental analysis. The bile and urine samples provided the in-vivo metabolic data. The level of Ca2+ATPase in the heart, determined by Western blotting, was used as the toxicodynamic parameterto correlate with the kinetic data. Multiple-dosing regimens reduced the total plasma clearance and increased the area under the plasma concentration-time curve of both drugs. Also, the area under the curve of doxorubicin associated with blood cells increased with the weekly doses, and the related mean residence time (MRT) and apparent volume of distribution (Vdss) were steadily reduced. In contrast to doxorubicin, the MRT and Vdss of epirubicin increased significantly. Metabolic data indicated significant differences in the level of alcohol and aglycones metabolites. Doxorubicinol and doxorubicin aglycones were significantly greater than epirubicinol and epirubicin aglycone, whereas epirubicinol aglycone was greater than doxorubicinol aglycone. The area under the blood cells concentration-time curve correlated linearly with the changes in Ca2+ATPase net intensity. The results of this study demonstrate the importance of the kinetics of epirubicin and doxorubicin associated with blood cells. Linear correlation between the reduction of net intensity of the biomarker with the area under the curve of doxorubicin associated with blood cells confirms that the differences between the two compounds are related to their interaction with blood cells. This observation together with the observed differences in metabolism may underline a significant role for blood cells in distribution and metabolism of doxorubicin and epirubicin.

Contradistinction between doxorubicin and epirubicin: in-vitro interaction with blood components.

The molecular structure and anti-tumour activity of doxorubicin and epirubicin are similar. However, the incidence of their cardiotoxicity occurs at different cumulative dose concentrations. The purpose of this study was to investigate the in-vitro interaction of these two drugs with different blood components, namely intact erythrocytes, haemoglobin and erythrocyte ghosts. Plasma protein binding was also evaluated. The intended goal was to identify the most relevant samples among total blood, plasma or blood cells for pharmacokinetic analysis. The methodology involved the incubation of each of the blood components (the intact erythrocytes, erythrocyte ghosts, haemoglobin and plasma proteins) at physiological pH and temperature with different concentrations of each drug, followed by measurement by HPLC and fluorometry at excitation and emission wavelengths of 480 and 580 nm, respectively. The results indicated that the binding of doxorubicin and epirubicin to plasma proteins, erythrocyte ghosts and intact erythrocytes was essentially the same. However, the binding of both compounds to intact erythrocytes was significantly different from erythrocyte ghosts, which indicates that haemoglobin plays an important role in the binding to and uptake by erythrocytes. The isotherms of binding to haemoglobin revealed that the maximum binding of doxorubicin was approximately 0.42 microg mg(-1) haemoglobin; for epirubicin this value was ten times greater than for doxorubicin. The Scatchard plot of binding of both drugs to haemoglobin exhibited two distinct binding sites for each drug. The constant of association of high affinity and low capacity binding sites was significantly greater for epirubicin, whereas the constant of association of low affinity and high capacity binding sites was significantly higher for doxorubicin. The number of high affinity binding sites per mg of haemoglobin was estimated to be 0.072 for doxorubcin and 0.030 for epirubicin. The number of low affinity binding sites was significantly greater for epirubicin (1.963) than for doxorubicin (0.305). Since the combined number of binding sites for epirubicin was more than doxorubicin, and the total uptake by erythrocytes remained the same for both drugs, it was concluded that epirubicin, being a more lipophilic compound, may diffuse more freely into the cells. Therefore, it binds more to haemoglobin, whereas doxorubicin remains more adsorbed on the surface of the cells due to its self-association property. It was concluded that the interaction of both drugs with erythrocytes, although it appears to be similar, is significantly different due to the interaction with haemoglobin. The difference in this interaction is expected to influence the disposition of both drugs in-vivo.