Thermodynamic profiling of inhibitors of Nrf2:Keap1 interactions.

Keap1 binds to the transcription factor Nrf2 and negatively modulates the expression of genes involved in cellular protection against oxidative stress. Small molecules have been discovered to inhibit the Nrf2:Keap1 interactions and act as antagonists of Keap1. The affinities of these small molecules are not very high and need further improvement in follow up hit-to-lead programs. In addition to the affinity parameters Ki, Kd, and IC50 thermodynamic parameters provide useful information for the selection and optimization of these hit molecules at the early stage of the lead discovery process. In this letter a tracer displacement assay was used to determine the thermodynamic signature of some of the known inhibitors of the Nrf2:Keap1 interaction. An optimized assay protocol is presented, which can be applied to other small molecules in hit-to-lead programs in a medium throughput manner.