Sotuletinib (formerly BLZ945; BLZ-945) is a novel, potent, selective, orally bioactive, and brain-penetrant CSF-1R (colony stimulating factor 1 receptor) inhibitor with potential antitumor activity. It exhibits 1000-fold higher selectivity against its closest receptor tyrosine kinase homologs and inhibits CSF-1R with an IC50 of 1 nM. Glioma-bearing mice demonstrate high in vivo antitumor efficaciousness of BLZ945. Sotuletinib was designated as an orphan drug by the US FDA in August 2022 in order to treat patients suffering from Amyotrophic Lateral Sclerosis (ALS), a progressive neurological disorder that affects nerve cells in the brain and spinal cord and results in loss of motor control.