Abstract
GDC-0834, a Bruton's tyrosine kinase inhibitor investigated as a potential treatment for rheumatoid arthritis, was previously reported to be extensively metabolized by amide hydrolysis such that no measurable levels of this compound was detected in human circulation following oral administration. In vitro studies in human liver cytosol determined GDC-0834 was rapidly hydrolyzed with CLint of 0.511 mL/min/mg protein. Aldehyde oxidase (AO) and carboxylesterase (CES) were putatively identified as the enzymes responsible following cytosolic fractionation and MS-proteomics analysis of the enzymatically active fractions. Results were confirmed by a series of kinetic experiments with inhibitors of AO, CES, and xanthine oxidase (XO), which implicated AO and CES, but not XO, as mediating GDC-0834 amide hydrolysis. Further supporting the interaction between GDC-0834 and AO, GDC-0834 was shown to be a potent reversible inhibitor of six known AO substrates with IC50 values ranging from 0.86 to 1.87 μM. Additionally, in silico modelling studies suggest that GDC-0834 is capable of binding in the active site of AO with the amide bond of GDC-0834 near the molybdenum cofactor (MoCo), orientated in such a way to enable potential nucleophilic attack on the carbonyl of the amide bond by the hydroxyl of MoCo. Together, the in vitro and in silico results suggest the involvement of AO in the amide hydrolysis of GDC-0834.
- The American Society for Pharmacology and Experimental Therapeutics