BW-534U87

1. The urinary metabolites of the anti-convulsant compound 4-amino-1-(2,6-difluorobenzyl)-1H-1,2,3-triazolo[4,5-c]-pyridine hydrochloride (GI265080) obtained following a single oral dose to man have been detected and quantified relative to each other using 19F-NMR spectroscopy. 2. The human urinary metabolites of GI265080 were isolated using semipreparative HPLC and unequivocally characterized using 1H-NMR spectroscopy, two-dimensional heteronuclear NMR spectroscopy and mass spectrometry. The assignments of the N-(5)-oxide and the N-(5)-O-glucuronide metabolites of GI265080 were further confirmed by independent synthesis. The urinary metabolites obtained following single oral doses to dog and rat have also been isolated and characterized. 3. The human urinary metabolites of GI265080 comprise the N-(5)-oxide, the quaternary N+-(5)-glucuronide, the 7-hydroxy glucuronide and a glucuronide conjugate of the N-(5)-oxide. The N-(5)-O-glucuronide conjugate is a novel species in human metabolism and is a significant route of elimination of GI265080 in man. 4. The urinary metabolites of the potential anti-convulsant GW273293 (6-amino-3-(2,3,5-trichlorophenyl)pyrazin-2-ylamine) obtained following a single oral dose to man have also been isolated and characterized. The formation of a novel N-O-glucuronide was also observed and was shown to constitute a significant route of elimination of GW273293 in man.

The cellular and molecular actions of BW534U87 were studied using intracellular and extracellular recordings from the CA1 region of rat hippocampal slices and whole‐cell voltage‐clamp recordings of recombinant human brain type IIA Na+ channels expressed in Chinese hamster ovary (CHO) cells.Normal excitatory and inhibitory postsynaptic potentials evoked in hippocampal slices were unaffected by BW534U87 or the adenosine deaminase inhibitor EHNA. However, epileptiform activity was depressed by BW534U87 (50 μM) and this inhibition was reversed by the adenosine receptor antagonist 8‐phenyl theophylline (8‐PT, 30 μM). EHNA (10 μM) mimicked the effects of BW534U87. Furthermore, BW534U87 enhanced the inhibitory effects of exogenous adenosine on evoked synaptic potentials. BW534U87 (50 μM) also voltage‐ and use‐dependently inhibited action potentials elicited by current injection, independent of the adenosine system, since it was not affected by 8‐PT.In CHO cells expressing the recombinant human brain Na+ channel, BW534U87 produced a concentration‐ and voltage‐dependent inhibition of Na+ currents with a half‐maximal inhibitory concentration of 10 μM at a Vh of −60 mV. Use‐dependent inhibition was evident at high‐frequencies (20×20 ms pulse train at 10 Hz).In conclusion, BW534U87 blocks hippocampal epileptiform activity by a dual mechanism. The first action is similar to that produced by EHNA and is dependent on endogenous adenosine probably by inhibition of adenosine deaminase. Secondly, BW534U87 directly inhibits voltage‐gated Na+ channels in a voltage‐ and frequency‐dependent manner. Both actions of BW534U87 are activity‐dependent and may synergistically contribute to its overall anticonvulsant effects in animal models of epilepsy.British Journal of Pharmacology (1999) 128, 1011–1020; doi:10.1038/sj.bjp.0702881