Synthesis of reversed hydroxamic acids of indomethacin: dual inhibitors of cyclooxygenase and 5-lipoxygenase

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.

1-Toluene-sulfonyl-3-[(3'-hydroxy-5'-substituted)-gamma-butyrolactone]-indoles: synthesis, COX-2 inhibition and anti-cancer activities

Indoles carrying a cyclic ester (gamma-butyrolactone) at C-3 position have been synthesized by the allylation of 3-indoleglyoxylate followed by iodocyclisation and the nucleophilic replacement of the iodo-group. Screening of these molecules for COX-2 inhibition and anti-cancer activities has identified compounds 10 and 11 as highly potent and selective for COX-2 as well as showing remarkable anti-cancer activities (better than that of indomethacin).

Nonsteroidal anti-inflammatory drugs as scaffolds for the design of 5-lipoxygenase inhibitors

Representative nonsteroidal anti-inflammatory drug (NSAID) cyclooxygenase inhibitors such as ibuprofen, naproxen, and indomethacin were used as orally bioavailable scaffolds to design selective 5-lipoxygenase (5-LO) inhibitors. Replacement of the NSAID carboxylic acid group with a N-hydroxyurea group provided congeners with selective 5-LO inhibitory activity.

Amino hydroxamic acids as potent inhibitors of leukotriene A4 hydrolase

Leukotriene A4 hydrolase is a zinc-containing enzyme which catalyzes the hydrolysis of LTA4 to LTB4, a proinflammatory mediator. The enzyme also exhibits an aminopeptidase activity. Due to its biological importance, it is of considerable interest to develop selective inhibitors of this enzyme. The design and synthesis of a number of potent beta-amino hydroxylamine and amino hydroxamic acid inhibitors are described here. It was found that having a free amine was essential for high activity. Hydroxylamines were found to be about an order of magnitude less potent than their analogous hydroxamic acids. Our investigation of amino hydroxamic acids as inhibitors of leukotriene A4 hydrolase has led to the development of hydroxamates 16 and 17, which are among the most potent inhibitors found to date. These, compounds were found to be competitive inhibitors with Ki values of 1.6 nM and 3.4 nM respectively, against the peptidase activity. Inhibitor 16 has an IC50 value of < or = 0.15 microM against the epoxide hydrolase activity and is also potent against the production of LTB4 by isolated polymorphonuclear leukocytes (PMNL) activated with ionophore A23187 (IC50 approximately 0.3 microM).