Chiral aspects of metabolism of antiinflammatory drug flobufen in human hepatocytes

Abstract

The metabolism of the nonsteroidal antiinflammatory drug flobufen, 4-(2',4'-difluorobiphenyl-4-yl)-2-methyl-4-oxobutanoic acid, was studied in primary cultures of human hepatocytes prepared by two-step collagenase perfusion of livers from four donors. Racemic flobufen or its individual enantiomers, R-(+)- and S-(-)-flobufen were used as substrates. Aliquots of culture medium were collected during 24-h incubation. The time-dependent disappearance of flobufen enantiomers and the formation of metabolites (stereoisomers of dihydroflobufen (DHF)) in hepatocytes were measured by chiral HPLC. The reduction of flobufen in human hepatocytes was stereoselective ((+)-R-flobufen was preferentially metabolized) and stereospecific ((2R;4S)-DHF and (2S;4S)-DHF stereoisomers were mostly formed). Although the structure of flobufen is different from the profens (2-arylpropionates), flobufen undergoes chiral inversion in human hepatocytes. The inversion of R-(+)-flobufen to S-(-)-flobufen predominates. The individual DHF stereoisomers were incubated in hepatocyte cultures and their biotransformation studied. The unidirectional chiral inversion of (2S;4S)-DHF to (2R;4S)-DHF and (2R;4R)-DHF to (2S;4R)-DHF was observed. Stereoselective oxidation of the DHFs to flobufen was also detected. Thus, flobufen metabolism in primary cultures of human hepatocytes is much more complicated (via chiral inversion and DHF re-oxidation) than was presumed from a preliminary achiral point of view.

Human Carbonyl Reduction Pathways and a Strategy for Their Study In Vitro

“…The stereochemistry of ketone reduction has been reported for a number of xenobiotics (Asami et al, 1996;Benedetti et al, 1991Benedetti et al, , 1993Breyer-Pfaff and Nill, 1995;Dow and Berg, 1995;Eyles and Pond, 1992;Hermans and Thijssen, 1989;Kume et al, 2000;Lawrence et al, 1990;McMahon et al, 1965;Nagata et al, 1992;Nicklasson et al, 2002;Rush et al, 1990;Skálová et al, 2003;Takasaki and Tanaka, 1992;Vickers et al, 1993;Volosov et al, 1999;Weil et al, 1989;Wsól et al, 1998a). However, the absolute configuration has not been determined in all cases.…”

Homochiral Drug Design and Development by Racemization

“…Knadler and Hall [20] described the racemization and hydrolysis of CoA thioesters of (R)-ibuprofen and (R)-fenoprofen with rat liver microsomal and mitochondrial fractions, which supported the findings of Nakamura et al [36]. Skalova et al [37] reported chiral inversion of R-(+)-flobufen and (2S;4S)-dihydroflobufen (DHF) in human hepatocytes. The authors also reported the unidirectional chiral inversion of the enantiomers of dihydroflobufen (DHF) as (2S;4S)-DHF to (2R;4S)-DHF and from (2R;4R)-DHF to (2S;4R)-DHF in hepatocyte cultures.…”

Role of racemization in optically active drugs development

“…31 Knadler and Hall 32 reported the racemization and hydrolysis of CoA thioesters of (R)-ibuprofen and (R)-fenoprofen with rat liver microsomal and mitochondrial fraction, which supported the findings of Nakamura et al 33 in 1981. Skalova et al 34 reported chiral inversion of R-(þ)-flobufen and (2S;4S)-dihydroflobufen (DHF) in human hepatocytes. The authors also reported the unidirectional chiral inversion of the enantiomers of dihydroflobufen (DHF) as (2S;4S)-DHF to (2R;4S)-DHF and from (2R;4R)-DHF to (2S;4R)-DHF in hepatocyte cultures.…”