Identification of metabolites of [14C]zonampanel, an a-amino-3-hydroxy-5-methylisoxazole-4-propionate receptor antagonist, following intravenous infusion in healthy volunteers.

This study determined the pharmacokinetics, metabolism and excretion of an a-amino-3-hydroxy-5-methylisoxazole-4-propionate receptor antagonist zonampanel monohydrate (YM872) after intravenous infusion of [14C]YM872 at 1 mg kg-1 h-1 for 2 h to four healthy male volunteers. Mean pharmacokinetic parameters of unchanged YM872 were 0.78 h for terminal half-life, 25.9 l h-1 for total clearance, 22.9 l h-1 for renal clearance, and 15.6 l for volume of distribution at steady-state. Urinary excretion of radioactivity accounted for 94.9% of the dose, and faecal excretion for only 0.5% of the dose. Measurement of YM872 concentrations by a high-performance liquid chromatography (HPLC)-ultraviolet method and radiometric HPLC metabolite profiling revealed that almost all of [14C]YM872 was excreted unchanged in the urine and that unchanged [14C]YM872 was the major circulating [14C] component in the plasma. Two minor metabolites, H1 and H2, detected in the urine and identified as the same chemical structures as those of the rat urinary metabolites, have a hydroxyamino group and an amino group, respectively, which were probably formed by reduction of the nitro group of YM872. These results show that virtually all of the administered YM872 remains unchanged, with urinary excretion representing the major elimination pathway. The high renal clearance implies tubular secretion of this drug.

Anguinomycins C and D, new antitumor antibiotics with selective cytotoxicity against transformed cells.

The retinoblastoma protein (pRB) is inactivated during the development of a wide variety of human cancers. In the course of our screening for antitumor antibiotics by using pRB-inactivated cells, an actinomycete strain was found to produce two active substances, which were elucidated to be new members of the leptomycin-anguinomycin family by NMR spectral analysis and were designated anguinomycins C and D. The anguinomycins induced growth arrest against normal cells and induced cell death against transformed cells, in which pRB was inactivated by viral oncoproteins such as human papillomavirus E7, adenovirus E1A and simian virus 40 large T antigen.