Crystallography-Guided Optimizations of the Keap1–Nrf2 Inhibitors on the Solvent Exposed Region: From Symmetric to Asymmetric Naphthalenesulfonamides

Directly
inhibiting the Keap1–Nrf2 protein–protein
interaction has been investigated as a promising strategy to activate
Nrf2 for anti-inflammation. We previously reported a naphthalensulfonamide
Keap1–Nrf2 inhibitor NXPZ-2, but have not determined
the exact binding mode with Keap1. This symmetric naphthalenesulfonamide
compound has relatively low solubility. Herein, we first determined
a crystal complex (resolution: 2.3 Å) of human Keap1 Kelch domain
with NXPZ-2. Further optimizations on the solvent exposed
region obtained asymmetric naphthalenesulfonamides and three crystal
structures of Keap1 in complex with designed compounds. Among them,
the asymmetric piperazinyl-naphthalenesulfonamide 6k with
better aqueous solubility showed the best KD2 value of 0.21 μM to block the interaction. The productions
of ROS and NO and the expression of TNF-α were inhibited by 6k in the in vitro model. This compound could relieve inflammations
by significantly increasing the Nrf2 nuclear translocation in the
LPS-induced ALI model with promising pharmacokinetic properties.