Accurate quantitative determination of affinity and binding kinetics for tight binding inhibition of xanthine oxidase

Biomed Pharmacother. 2021 Jul;139:111664. doi: 10.1016/j.biopha.2021.111664. Epub 2021 May 13.ABSTRACTThe accurate quantitative determination of affinity and binding kinetics (BK) for tight binding inhibition is extraordinary important from both the continuous optimization of compounds, particularly in developing structure-activity relationships (SAR), and the prediction of in vivo target occupancy (TO). Due to the unique properties for tight binding inhibition that the inhibitors are characterized by the ultrahigh-affinity, relatively fast association to the target enzyme combined with extremely slow dissociation of the inhibitor-enzyme binary complex, the classical steady state equilibrium methods are no longer valid. Here, we made several recommendations of how to design the optimal experiments and apply special mathematical calculation approaches to quantitatively evaluate the accurate affinity and BK as the examples of two tight binding inhibitors against the xanthine oxidase (XO), as well as compared the differences in the results calculated from the different data analytical methods and analyzed the influence of these differences on the XO engagement in human. Analysis of the results displayed that the accurate apparent dissociation constant (Ki*,app) was 0.2 ± 0.06 nM for topiroxotstat and was 0.45 ± 0.2 nM for febuxostat; that on-rate (kon) was (4.3 ± 1.1) × 106 M-1s-1 for topiroxotstat and was(133.3 ± 3.5) × 106 M-1s-1 for febuxostat, and off-rate (koff) was (...
Source: Biomedicine and pharmacotherapy = Biomedecine and pharmacotherapie - Category: Drugs & Pharmacology Authors: Source Type: research