Acyl glucuronides: the good, the bad and the ugly.
Acyl glucuronidation is the major metabolic conjugation reaction of most carboxylic acid drugs in mammals. The physiological consequences of this biotransformation have been investigated incompletely but include effects on drug metabolism, protein binding, distribution and clearance that impact upon pharmacological and toxicological outcomes. In marked contrast, the exceptional but widely disparate chemical reactivity of acyl glucuronides has attracted far greater attention. Specifically, the complex transacylation and glycation reactions with proteins have provoked much inconclusive debate over the safety of drugs metabolised to acyl glucuronides. It has been hypothesised that these covalent modifications could initiate idiosyncratic adverse drug reactions. However, despite a large body of in vitro data on the reactions of acyl glucuronides with protein, evidence for adduct formation from acyl glucuronides in vivo is limited and potentially ambiguous. The causal connection of protein adduction to adverse drug reactions remains uncertain. This review has assessed the intrinsic reactivity, metabolic stability and pharmacokinetic properties of acyl glucuronides in the context of physiological, pharmacological and toxicological perspectives. Although numerous experiments have characterised the reactions of acyl glucuronides with proteins, these might be attenuated substantially in vivo by rapid clearance of the conjugates. Consequently, to delineate a relationship between acyl glucuronide formation and toxicological phenomena, detailed pharmacokinetic analysis of systemic exposure to the acyl glucuronide should be undertaken adjacent to determining protein adduct concentrations in vivo. Further investigation is required to ascertain whether acyl glucuronide clearance is sufficient to prevent covalent modification of endogenous proteins and consequentially a potential immunological response.
Regan
Sophie L
SL
MRC Centre for Drug Safety Science, Institute of Translational Medicine, The University of Liverpool, Liverpool L69 3GE, UK. s.l.regan@liv.ac.uk
Maggs
James L
JL
Hammond
Thomas G
TG
Lambert
Craig
C
Williams
Dominic P
DP
Park
B Kevin
BK
D000215:Acylation; D000818:Animals; D001711:Biotransformation; D002264:Carboxylic Acids / Q000009:adverse effects / Q000737:chemistry / Q000378:metabolism* / Q000494:pharmacology; D064420:Drug-Related Side Effects and Adverse Reactions; D020719:Glucuronides / Q000009:adverse effects / Q000378:metabolism* / Q000493:pharmacokinetics / Q000494:pharmacology; D006801:Humans; D004364:Pharmaceutical Preparations / Q000378:metabolism*; D011485:Protein Binding; D011506:Proteins / Q000378:metabolism*
D002264:Carboxylic Acids; D020719:Glucuronides; D004364:Pharmaceutical Preparations; D011506:Proteins