Design of spiro-heterocyclic substituted diaminonaphthalene Keap1-Nrf2 protein-protein interaction inhibitors as novel anti-depressant agents

Oxidative stress, inflammation and the Keap1-Nrf2 pathway are validated to be related to depression. Theoretically, modulating Keap1 and Nrf2 protein-protein interaction (PPI) should be an effective method to activate Nrf2 for the treatment of major depressive disorders. We previously reported NXPZ-2, a 1,4-diaminonaphthalene, as a Keap1-Nrf2 PPI inhibitor that exhibited promising effects in an Alzheimer's disease (AD) mouse model. However, its pharmacokinetic properties were limited. Herein, we, for the first time, developed a series of heterocyclic substituted diaminonaphthalenes by an “Escape from Flatland” strategy to improve sp³ hybridized carbons. These compounds exhibited strong binding affinity for Keap1. A crystallographic analysis revealed the high-resolution (1.44 Å) binding of CD-10 with the Keap1 protein, elucidating the complexity of CD-10's binding mechanism. In an LPS-stimulated BV2 cell model, CD-10 demonstrated the best anti-oxidative stress and anti-inflammatory potential. Furthermore, CD-10's ability to penetrate the blood-brain barrier has been significantly improved. In a chronic unpredictable mild stress (CUMS) mouse model, treatment with CD-10 effectively alleviated anxiety and depressive behaviors and restored serum neurotransmitter levels by promoting Nrf2 nuclear translocation. Overall, our findings validate that the Keap1-Nrf2 PPI inhibitor holds promise as a preclinical candidate for the treatment of depression.