Recent progress in the development of small molecule Nrf2 modulators: a patent review (2012-2016).

INTRODUCTION: The NF-E2-related factor-2 (Nrf2) is a critical transcription factor that regulates the expression of many phase II and antioxidant genes to maintain the homeostasis. It has many biological functions and plays a central role in the cellular defensive machinery. The abnormal regulation of Nrf2 is closely associated with multiple diseases. Areas covered: This article first discusses the molecular regulatory mechanism of Nrf2-antioxidant response element (ARE) signaling. Then patents and publications about Nrf2 activators and inhibitors from 2012-2016 are reviewed. Several case studies are emphasized to introduce the molecular design strategy, especially on Keap1-Nrf2 protein-protein interaction (PPI) inhibitor. Expert opinion: Firstly, new chemotypes of Nrf2 modulators can be designed in a combination of the progress of both covalent modifiers and target selective Keap1-Nrf2 interaction inhibitors. The aim is to balance the activity and toxicity of Nrf2 modulators. Secondly, considering many known Nrf2 activators, such as DMF and SFN, are electrophilic entities with very small molecular weight, we need to update the concept of how to recognize a drug candidate. Finally, per the mechanism of the Nrf2 modulator, compounds with the most active Nrf2 inductivity maybe not the best choice for the design of an ideal chemopreventive agent.