Tulathromycin is a novel member of the triamilide class of antibiotics that was developed as a safe and effective single-dose treatment of bovine and porcine respiratory disease. An accurate and precise analytical method was developed for the extraction and measurement of tulathromycin in livestock plasma and lung homogenates. Analytes were solid-phase extracted onto a weak cation exchanger after aqueous dilution of samples and addition of heptadeutero-tulathromycin as an internal standard. Following HPLC with a narrow bore C8 column, quantitative detection of tulathromycin was accomplished by monitoring the transition of a doubly charged precursor ion to a singly charged product ion by tandem mass spectrometry using a triple quadrupole mass spectrometer. Procedures were validated for a dynamic range of 0.1 to 25 ng on column. Observed accuracies were between 90 and 110% of nominal and precision (RSD) varying 7% or less. Response and stability experiments showed that deuterated tulathromycin did not parallel the chemical behavior of tulathromycin. Applicability of the method to livestock studies was tested with plasma and lung samples from cattle and swine dosed with tulathromycin at multiple doses. The results demonstrated that the analytical method performed well in a range of sample concentrations spanning over 3 orders of magnitude and provided dose-exposure relationships for cattle and swine.

Anidulafungin is a novel semisynthetic echinocandin with potent activity against Candida (including azoleresistant isolates) and Aspergillus spp. and is used for serious systemic fungal infections. The purpose of these studies was to characterize the clearance mechanism and potential for drug interactions of anidulafungin. Experiments included in vitro degradation of anidulafungin in buffer and human plasma, a bioassay for antifungal activity, in vitro human cytochrome P450 inhibition studies, in vitro incubation with rat and human hepatocytes, and mass balance studies in rats and humans. Clearance of anidulafungin appeared to be primarily due to slow chemical degradation, with no evidence of hepatic-mediated metabolism (phase 1 or 2). Under physiological conditions, further degradation of the primary degradant appears to take place. The primary degradation product does not retain antifungal activity. Anidulafungin was not an inhibitor of cytochrome P450 enzymes commonly involved in drug metabolism. Mass balance studies showed that anidulafungin was eliminated in the feces predominantly as degradation products, with only a small fraction (10%) eliminated as unchanged drug; fecal elimination likely occurred via biliary excretion. Only negligible renal involvement in the drug's elimination was observed. In conclusion, the primary biotransformation of anidulafungin is mediated by slow chemical degradation, with no evidence for hepatic enzymatic metabolism or renal elimination.The echinocandins are a relatively new class of parenterally administered antifungal agents that have been developed for the treatment of serious systemic fungal infections. Members of this class include caspofungin, micafungin, and anidulafungin; the latter is a novel semisynthetic echinocandin with potent in vitro and in vivo activities against Candida spp. and Aspergillus spp., the major causes of deep-seated mycoses (4,5,24). Anidulafungin is approved in the United States and Europe for the treatment of candidemia in nonneutropenic patients and other forms of invasive Candida infections (11,25). Anidulafungin ( Fig. 1) has distinct pharmacokinetic characteristics, activity against azole-resistant Candida spp., and a favorable safety profile, all of which support its use for systemic fungal infections (26).Echinocandins mediate their antifungal activity by noncompetitive inhibition of (1,3)-␤-D-glucan synthase, a fungus-specific enzyme essential for the synthesis of cell wall glucan (5). While this mode of action is common to all members of the class, there appear to be some differences among echinocandins with respect to their pharmacokinetic properties, including drug disposition (3,5,26). Some of these differences may have implications for the concomitant use of these agents with other drugs and for their use in special patient populations, particularly those under intensive care.To this end, the studies described here were designed to characterize the clearance mechanism and disposition of anidulafungin in rats and humans, as well as to...

1,2-Dibromo-[1,2-14C]ethane was bound irreversibly to DNA when glutathione S-transferase or rat liver cytosolic components were added to incubations of calf thymus DNA and glutathione at 37 degrees C. There was no DNA binding of 1,2-dibromoethane when glutathione was absent or in incubations of DNA with microsomal proteins with or without NADPH, thus supporting the proposal that the major route of DNA binding by 1,2-dibromoethane occurs via conjugation to glutathione. In vitro binding of 1,2-dibromoethane occurred most effectively when the YaYc (or 'B') isozyme of glutathione S-transferase was included in incubations of DNA with 1,2-dibromoethane and glutathione. Other dihaloalkanes were incubated with DNA in the presence of glutathione S-transferase and [35S]glutathione. Of these, only 1,2-dibromo-3-chloropropane and tris-(2,3-dibromopropyl)-phosphate led to significant DNA binding of [35S]glutathione. 1,2-Dibromo-3-chloro-[1,3-14C]propane was bound to DNA when glutathione and glutathione S-transferase were present. However, even higher 1,2-dibromo-3-chloropropane binding to DNA occurred when cytosol or microsomes were included in incubations without glutathione. When glutathione was added to incubations containing cytosol and 1,2-dibromo-3-chloropropane, total DNA binding was decreased. Thus, the actual amount of DNA binding by dihaloethanes in vivo may be the result of a complicated balance among the opposing roles of glutathione conjugation in detoxicating and activating processes.

Methionine aminopeptidase 2 (MetAP2) inhibition is a promising approach to treating diabetes, obesity, and associated metabolic disorders. Beloranib, a MetAP2 inhibitor previously investigated for treatment of Prader-Willi syndrome, was associated with venous thrombotic adverse events likely resulting from drug effects on vascular endothelial cells (ECs). Here, we report the pharmacological characterization of ZGN-1061, a novel MetAP2 inhibitor being investigated for treatment of diabetes and obesity. Four weeks of subcutaneous administration of ZGN-1061 to diet-induced obese (DIO) insulin-resistant mice produced a 25% reduction in body weight, primarily due to reduced fat mass, that was comparable to beloranib. ZGN-1061 also produced improvements in metabolic parameters, including plasma glucose and insulin, and, in HepG2 cells, initiated gene changes similar to beloranib that support observed in vivo pharmacodynamics. In vitro studies in ECs demonstrated that ZGN-1061 effects on EC proliferation and coagulation proteins were greatly attenuated, or absent, relative to beloranib, due to lower intracellular drug concentrations, shorter half-life of inhibitor-bound MetAP2 complex, and reduced cellular enzyme inhibition. In dogs, ZGN-1061 was more rapidly absorbed and cleared, with a shorter half-life than beloranib. Unlike beloranib, ZGN-1061 did not increase coagulation markers in dogs, and ZGN-1061 had a greatly improved safety profile in rats relative to beloranib. In conclusion, ZGN-1061 and beloranib demonstrated similar efficacy in a mouse model of obesity, while ZGN-1061 had a markedly improved safety profile in multiple in vitro and in vivo models. The lower duration of exposure characteristic of ZGN-1061 is expected to provide a meaningfully enhanced clinical safety profile.