Exploring the NCS-382 Scaffold for CaMKII alpha Modulation: Synthesis, Biochemical Pharmacology, and Biophysical Characterization of Ph-HTBA as a Novel High-Affinity Brain-Penetrant Stabilizer of the CaMKII alpha Hub Domain

Ca2+/calmodulin-dependent protein kinase II alpha (CaMKII alpha) is a brain-relevant kinase and an emerging drug target for ischemic stroke and neurodegenerative disorders. Despite reported CaMKII alpha inhibitors, their usefulness is limited by low subtype selectivity and brain permeability. (E)-2-(5-Hydroxy-5,7,8,9-tetrahydro-6H-benzo[7]annulen-6-ylidene)acetic acid (NCS-382) is structurally related to the proposed neuromodulator, gamma-hydroxybutyric acid, and is a brain-penetrating high nanomolar-affinity ligand selective for the CaMKII alpha hub domain. Herein, we report the first series of NCS-382 analogs displaying improved affinity and preserved brain permeability. Specifically, we present Ph-HTBA (1i) with enhanced mid-nanomolar affinity for the CaMKII alpha binding site and a marked hub thermal stabilization effect along with a distinct CaMKII alpha Trp403 flip upon binding. Moreover, Ph-HTBA has good cellular permeability and low microsomal clearance and shows brain permeability after systemic administration to mice, signified by a high Kp, uu value (0.85). Altogether, our study highlights Ph-HTBA as a promising candidate for CaMKII alpha-associated pharmacological interventions and future clinical development.