PF-06463922 is a potent and selective ALK/ROS1 inhibitor with IC50 values ranging from 0.19-0.53 nM for the kinase activity of ROS1 fusion enzymes [1].

The receptor tyrosine kinase c-ros oncogene1 (ROS1) is a receptor with a kinase domain that is related to the anaplastic lymphoma kinase/lymphocyte-specific protein tyrosine kinase (ALK/LTK) and insulin receptor (INSR) RTK families [1].

Via cellular ROS1 autophosphorylation in the recombinant enzyme assay, PF-06463922 showed a 30-fold improved potency against ROS1, compared with crizotinib, ceritinib, alectinib and foretinib (XL-880). Engineered NIH 3T3 cells were expressing oncogenic human ROS1 fusions. In these cells, PF-06463922 was more potent than foretinib and crizotinib by >10 folds, more potent than alectinib and ceritinib by >100 folds against cellular ROS1 autophosphorylation [1].

Oncogenic gene fusions involving the 3' region of ROS1 kinase had been found in various human cancers [2]. Mice bearing CD74-ROS1, CD74-ROS1G2032R and FIG-ROS1(S) s.c. Tumors (250 mm3) were used. Treatments with PF-06463992 at various doses were applied consecutively for 7 or 9 d. At dosages of 0.2 to 1 mg/kg/d, PF-06463922 significantly inhibited the growth of both established FIGROS1(S) and CD74-ROS1 tumors compared with vehicle control. At 2-6 mg/kg/d, PF-06463922 significantly made tumor volumes regress (58–85%, P < 0.0001). In animals bearing NIH 3T3-CD74-ROS1G2032R tumors, treatment with PF-06463922 at 1.0, 3.0, and 10 mg/kg/d significantly inhibited tumor growth by 28%, 44% and 90%, respectively. At 30 mg/kg/d, PF-06463922 made tumor regress by 12%, compared with vehicle [1].