High affinity and selective ALK and ROS1 inhibitor (Ki values are <0.02, <0.07 and 0.7 nM for ROS1, wild-type ALK and ALK-L1196M, respectively). Exhibits >100-fold selectivity for ROS1 over a panel of 204 other kinases. Inhibits proliferation of BaF3 cells containing crizotinib -resistant ROS1 mutation in vitro. Inhibits tumor growth in relevant mouse models. Orally available and brain penetrant. Purity 98%. MW (observed): 406.41