The disposition and metabolism of zibotentan (ZD4054): an oral-specific endothelin A receptor antagonist in mice, rats and dogs.

Zibotentan (ZD4054) is an oral-specific endothelin A receptor antagonist in development for the treatment of castration-resistant prostate cancer. In a number of preclinical studies, the disposition and metabolism of zibotentan were investigated in mice, rats and dogs. Following oral and intravenous administration, zibotentan was slowly absorbed (maximal concentration at approximately 4 h) and rapidly excreted, with the majority being eliminated by 48 h. The main route of elimination was via the urine in dogs and female rats, but via the faeces in male rats and mice of both sexes. Zibotentan was moderately bound to plasma proteins of all species examined (55-95%), and widely distributed throughout all tissues with the highest concentrations seen in the organs of excretion. Zibotentan was moderately metabolised. Zibotentan was well absorbed, moderately bound to plasma proteins, widely distributed and excreted predominantly via the urine.

Evaluation of the use of UPLC-TOFMS with simultaneous [14C]-radioflow detection for drug metabolite profiling: application to propranolol metabolites in rat urine.

The non-selective beta-adrenergic receptor antagonist propranolol [1-(isopropylamino)-3-(1-naphthoxy)-2-propanol] is metabolised extensively in vivo. Enumerating and identifying the many metabolites that result from multiple biotransformations provides a considerable analytical challenge, greatly aided by efficient chromatography coupled to sensitive mass spectrometric detection. Here the use of the newly introduced high-resolution technique of "ultra performance liquid chromatography" (UPLC) linked to quadrupole time-of-flight mass spectrometry (TOFMS) with simultaneous [(14)C]-radioflow detection was applied to rapid metabolite profiling. [14C]-propranolol, dosed intraperitoneally to rat at 25 mg kg(-1) and 200 microCi kg(-1) was used as a model compound for this evaluation. Some 14 metabolites were detected in the urine by this technique including a number of conjugated metabolites such as sulphates, several isobaric glucuronides and two novel di-glucuronides.

Metabolic disposition of gefitinib, an epidermal growth factor receptor tyrosine kinase inhibitor, in rat, dog and man.

Following oral administration of [14C]-gefitinib to albino and pigmented rats, radioactivity was widely and rapidly distributed, with the highest levels being found in liver, kidney, lung and gastrointestinal tract, but with only low levels penetrating the brain. Levels of radioactivity persisted in melanin-containing tissues (pigmented eye and skin). Binding to plasma proteins was high (86-94%) across the range of species examined and was 91% in human plasma. Substantial binding occurred to both human serum albumin and alpha-1 acid glycoprotein. Following oral and intravenous administration of [14C]-gefitinib, excretion of radioactivity by rat, dog and human occurred predominantly via the bile into faeces, with < 7% of the dose being eliminated in urine. In all three species, gefitinib was cleared primarily by metabolism. In rat, morpholine ring oxidation was the major route of metabolism, leading to the formation of M537194 and M608236 as the main biliary metabolites. Morpholine ring oxidation, together with production of M523595 by O-demethylation of the quinazoline moiety, were the predominant pathways in dog, with oxidative defluorination also occurring to a lesser degree. Pathways in healthy human volunteers were similar to dog, with O-demethylation and morpholine ring oxidation representing the major routes of metabolism.