[AR-L 115 BS, comparison of human metabolite pattern and biotransformation with other species]

Following oral administration of 14C labelled 2-[(2-methoxy-4-methylsulfinyl)phenyl]-1H-imidazo[4,5-b]pyridine (AR-L 115 BS) to the rat, rabbit, dog, rhesus monkey, baboon and man the metabolic pattern in plasma and urine was compared and human urinary metabolites were isolated. None of the animal species investigated shows a metabolic pattern identical to that of man. The plasma of rat, dog and rabbit shows wide variation of metabolites with high amounts of two unpolar metabolites of AR-L 115 BS (sulfoxide), namely M0/2 identical with AR-L 114 BS (sulfone with regard to AR-L 115 BS) and M0/1 identical with AR-L 113 BS (sulfide). In comparison to man the urines of the animals show higher amounts of the sulfone (AR-L 114 BS) and the sulfide (AR-L 113 BS). A main pathway of the metabolism of the pyrido-imidazole of the AR-L 115 BS-type is the oxidative pyridine-ring cleavage leading to N-acetylated 5-aminoimidazoles. Further metabolites are characterised by a hydroxyl group in the 6-position of the pyrido-imidazole moiety. Besides the oxidation of tthe sulfoxide function to the sulfone we could also observe the thioether (sulfide) not only of the parent compound itself but also of some of the metabolites in the series of the AR-L 115 BS-biotransformation. The identification of the human urinary metabolites, was carried out by means of TLC, HPLC, UV-, MS- and NMR-spectroscopy.