Application of biocatalysis to drug metabolism: preparation of mammalian metabolites of a biaryl-bis-sulfonamide AMPA (alpha-amino-3-hydroxy-5-methylisoxazole-4-propionic acid) receptor potentiator using Actinoplanes missouriensis.

LY451395 (2-propanesulfonamide, N-[(2R)-2-[4'-[2-[methylsulfonyl)amino]ethyl][1,1'-biphenyl]-4-yl]propyl]-) is a potent and highly selective potentiator of the alpha-amino-3-hydroxy-5-methylisoxazole-4-propionic acid (AMPA) receptors. It is a biaryl-bis-sulfonamide and is known to be highly metabolized in preclinical species. In those metabolism studies, the metabolite structures were proposed exclusively by the analysis of mass spectrometric data. Although mass spectrometry is clearly a technique of choice for rapid identification of drug metabolites, occasionally, nuclear magnetic resonance spectroscopy is required to unambiguously assign and characterize, particularly, the regio- and stereochemistry of metabolic changes. Nuclear magnetic resonance spectroscopy, in general, is less sensitive than other detection methods and demands several micrograms of material for the analysis. To support full structure characterization of metabolites by NMR, in this study we demonstrated the application of a microbial-based surrogate biocatalytic system to produce sufficient amounts of the mammalian metabolites of LY451395. The results revealed that incubation of LY451395 with Actinoplanes missouriensis NRRL B3342 generated several metabolites that were previously detected in the in vivo metabolism studies of the preclinical species. Subsequent large-scale bioconversion resulted in the isolation of seven mammalian metabolites in milligram quantities for structural characterization by nuclear magnetic resonance spectroscopy. Furthermore, a selected group of metabolites generated from the microbial conversion served as analytical standards to monitor and quantify drug metabolites during clinical investigations.

In vivo metabolism of [14C]ruboxistaurin in dogs, mice, and rats following oral administration and the structure determination of its metabolites by liquid chromatography/mass spectrometry and NMR spectroscopy.

Ruboxistaurin (LY333531), a potent and isoform-selective protein kinase C beta inhibitor, is currently undergoing clinical trials as a therapeutic agent for the treatment of diabetic microvascular complications. The present study describes the disposition and metabolism of [14C]ruboxistaurin following administration of an oral dose to dogs, mice, and rats. The study revealed that ruboxistaurin was highly metabolized in all species. Furthermore, the results from the bile duct-cannulated study revealed that ruboxistaurin was well absorbed in rats. The primary route of excretion of ruboxistaurin and its metabolites was through feces in all species. The major metabolite detected consistently in all matrices for all species was the N-desmethyl metabolite 1, with the exception of rat bile, in which hydroxy N-desmethyl metabolite 5 was detected as the major metabolite. Other significant metabolites detected in dog plasma were 2, 3, 5, and 6 and in mouse plasma 2, 5, and 19. The structures of the metabolites were proposed by tandem mass spectrometry with the exception of 1, 2, 3, 5, and 6, which were additionally confirmed either by direct comparison with authentic standards or by nuclear magnetic resonance spectroscopy. To assist identification by nuclear magnetic resonance spectroscopy, metabolites 3 and 5 were produced via biotransformation using recombinant human CYP2D6 and, likewise, metabolite 6 and compound 4 (regioisomer of 3 which did not correlate to metabolites found in vivo) were produced using a microbe, Mortierella zonata. The unambiguous identification of metabolites enabled the proposal of clear metabolic pathways of ruboxistaurin in dogs, mice, and rats.