Identification of a novel benzoxazolone derivative as a selective, orally active 18 kDa translocator protein (TSPO) ligand.

Optimization of the pharmacokinetic properties for a series of benzoxazolone derivatives led to the identification of 9b, which showed anxiolytic effect in a rat model. However, 9b, like known benzodiazepines, induced motor impairment. Investigation into the cause of this unexpected side effect and management of 9b off-target binding affinity led to the identification of 10d, which showed oral anxiolytic effect in the rat model with improved safety profile.