Crizotinib (trade name Xalkori, Pfizer, is an anti-cancer drug acting as an ALK (anaplastic lymphoma kinase) and ROS1 (c-ros oncogene 1) inhibitor, approved for treatment of some non-small cell lung carcinoma (NSCLC) in the US and some other countries, and undergoing clinical trials testing its safety and efficacy in anaplastic large cell lymphoma, neuroblastoma, and other advanced solid tumors in both adults and children.
Crizotinib has an aminopyridine structure, and functions as a protein kinase inhibitor by competitive binding within the ATP-binding pocket of target kinases. About 4% of patients with non-small cell lung carcinoma have a chromosomal rearrangement that generates a fusion gene between EML4 (‘echinoderm microtubule-associated protein-like 4’) and ALK (‘anaplastic lymphoma kinase’), which results in constitutive kinase activity that contributes to carcinogenesis and seems to drive the malignant phenotype. The kinase activity of the fusion protein is inhibited by crizotinib. Patients with this gene fusion are typically younger non-smokers who do not have mutations in either the epidermal growth factor receptor gene (EGFR) or in the K-Ras gene. The number of new cases of ALK-fusion NSLC is about 9,000 per year in the U.S. and about 45,000 worldwide.