IN-VITRO AND IN-VIVO BIOTRANSFORMATION OF -2,4-DI-1-PYRROLIDINYL-7H-PYRROLO[2,3-D]PYRIMIDINE (U-89843) IN THE RAT

The biotransformation of -2,4-di-1-pyrrolidinyl-7H-pyrrolo[2,3-d]pyrim idine (U-89843) has been studied in rat both in vitro and in vivo. Maj or metabolites observed by HPLC analysis of rat plasma, liver cytosol, and microsomal incubations were characterized by UV, LC/MS, and compa rison with synthetic standards, The structures of the metabolites were shown to be the C-6 hydroxymethyl (U-97924), C-6 formyl (U-97865), an d C-6 carboxyl analogs of U-89843, In the male rat, formation of U-979 24 is mediated by cytochrome P4502C11. Kinetic analysis of U-97924 for mation indicated that it was a high-affinity/high-capacity process (K- M = 4.2 +/- 0.5 mu M; V-max = 21.2 +/- 0.8 nmol/mg/min). Formation of U-97865 via enzymatic oxidation from the primary metabolite U-97924 wa s catalyzed by both the microsomal subcellular fraction in a NADPH-dep endent process (presumably via cytochrome P450) and in cytosol by NAD( +)-dependent alcohol dehydrogenase. Upon incubation with cytosolic fra ctions, U-97865 was found to undergo NAD(+)-dependent oxidation, media ted by aldehyde dehydrogenase, to the corresponding carboxylic acid. A lthough significant levels of U-89843, U-97924, and U-97865 were obser ved in vivo in rat plasma, only a minor amount of the carboxylic acid together with larger amounts of unidentified polar metabolites were ex creted in urine and feces.