PLX5622 hemifumarate is a highly selective brain penetrant and orally active CSF1R inhibitor with an IC 50 of 0.016 uM and Ki of 5.9 nM. PLX5622 hemifumarate allows for extended and specific microglial elimination, preceding and during pathology development. In vivo, PLX5622 hemifumarate demonstrates desirable PK properties in varies animals (1) (2).