Synthesis, stability, biochemical and pharmacokinetic properties of a new potent and selective 4-oxo-β-lactam inhibitor of human leukocyte elastase

Abstract

The 4-oxo-β-lactams (azetidine-2,4-diones) are potent acylating agents of the human leukocyte elastase (HLE), a neutrophil serine protease that plays a key role in several inflammatory diseases. A novel 4-oxo-β-lactam containing a N-(4-(phenylsulphonylmethyl)phenyl) group, 3, was designed as a potential mechanism-based inhibitor capable of undergoing elimination of phenylsulphinate upon Ser-195 acylation. Compound 3 was found to be a potent slow-tight binding inhibitor of HLE, presenting a remarkable second-order rate constant of 1.46 × 10⁶ M⁻¹s⁻¹ and displaying selectivity over the proteinase 3 and cathepsin G. However, liberation of phenylsulphinate was not observed in the hydrolysis of 3 in both pH 7.4 phosphate buffer and human plasma. The C_max values of 1207 μg/total blood, 179 μg/g spleen and 106 μg/g lung were determined by HPLC, following a single 30 mg/kg dose of 3 given intraperitoneally to NMRI mice, suggesting that the inhibitor distributes well into tissues. Although being a powerful selective inhibitor of HLE, 4-oxo-β-lactam 3 has a limited stability, being susceptible to off-target reactions (plasma and liver enzymes).

Keywords::

• Slow-tight binding
• human leukocyte elastase
• proteinase 3
• stability
• human plasma
• biodistribution

Declarations of interest

This work was funded by Fundação para a Ciência e Tecnologia (Foundation for Science and Technology) (FCT, Portugal) through the project PTDC/QUI/64056/2006. J.M. acknowledges the FCT for the PhD grant SFRH/BD/17534/2004.