Abstract B76: In vitro screen to identify ALK mutations conferring crizotinib resistance.

Abstract

Anaplastic lymphoma kinase (ALK) is a receptor tyrosine kinase belonging to the insulin receptor superfamily. Activating mutations in ALK are oncogenic and cause 10 to 15% of neuroblastoma cases. Similarly, activating ALK fusions have been detected in several cancers, including ALCL (NPM-ALK in 70% of patients) and NSCLC (EML4-ALK in 3–7% of patients). ALK inhibitors from different compound classes and kinase selectivity profiles are currently undergoing clinical development, among which crizotinib has recently received marketing approval from the US FDA. This non-selective ALK inhibitor has provided clinical benefit to lung cancer patients, but its sustained efficacy seems to be impaired by acquired drug resistance and several publications have already described ALK secondary mutations identified in patients who progressed while on crizotinib therapy. In this study, we have used the Ba/F3 system to identify EML4-ALK mutations able to confer resistance to crizotinib. To this end, we have generated a cDNA library containing random mutations in EML4-ALK using an E. Coli strain deficient in DNA repair pathways. The library was then subcloned in a retroviral vector and used to infect Ba/F3 cells. The cells were plated in 96 well microplates at an appropriate dilution and allowed to grow in the presence of 500 nM of crizotinib. The resistant cells were cultured and EML4-ALK was sequenced. Overall, this screen identified mutations at 24 positions in the ALK kinase domain. Some of these mutations (L1152R, C1156Y, F1174L) correspond to the ones known to cause resistance in lung cancer patients treated with crizotinib. Ba/F3 cell lines stably expressing a selected number of the 24 mutations have been generated and used to evaluate the activity of in-house and reference ALK kinase modulators. This work has shown that several mutations known to activate ALK in neuroblastoma are also able to confer resistance to crizotinib. The Ba/F3 cell lines expressing EML4-ALK mutants have been useful tools to characterize the activity profile of a range of ALK kinase inhibitors and several of our in-house compounds have been identified as active against the crizotinib-allele resistant mutants. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2011 Nov 12-16; San Francisco, CA. Philadelphia (PA): AACR; Mol Cancer Ther 2011;10(11 Suppl):Abstract nr B76.