Benzimidazole Inhibitors Induce a DFG-Out Conformation of Never in Mitosis Gene A-Related Kinase 2 (Nek2) without Binding to the Back Pocket and Reveal a Nonlinear Structure−Activity Relationship

We describe herein the structure−activity relationship (SAR) and cocrystal structures of a series of Nek2 inhibitors derived from the published polo-like kinase 1 (Plk1) inhibitor (R)-1. Our studies reveal a nonlinear SAR for Nek2 and our cocrystal structures show that compounds in this series bind to a DFG-out conformation of Nek2 without extending into the enlarged back pocket commonly found in this conformation. These observations were further investigated, and structure-based design led to Nek2 inhibitors derived from (R)-1 with more than a hundred-fold selectivity against Plk1.