Abstract 3715: Discovery of novel targets for effective combination drug therapy in ALK+ NSCLC patient derived models of acquired resistance
Authors: Crystal Adam S. , Engelman Jeffrey A. , Benes Cyril H. , Gomez-Caraballo Maria G. , Frias Rosa , Lockerman Elizabeth , Shaw Alice T. 
Published: May 2015

Abstract
Non-small cell lung cancer (NSCLC) is the leading cause of cancer death worldwide. The EML4-ALK translocation is present in 4% of NSCLC cases and responses to the ALK inhibitor crizotinib in these cases are dramatic. However, the impact of crizotinib on patient survival is limited by the eventual development of acquired resistance. In addition to secondary mutations in the primary target (such as ALK L1196M), acquired resistance develops when a bypass track develops and renders ALK signaling redundant.
Based on the concept of the bypass track, we developed a straightforward pharmacologic platform to identify combination therapeutic strategies capable of overcoming acquired resistance. In this approach the GI50 of 78 test compounds is tested in the presence or absence of a fixed concentration of ALK inhibitor (either crizotinib or the second generation ALK inhibitor LDK378). Those drugs which are more potent in the presence of ALK inhibitor are considered hits. We applied this approach to 15 cell line models of acquired resistance to ALK inhibitors. Critically, this panel of models included 9 models derived directly from ALK+ patients who had progressed on an ALK inhibitor.
Multiple model specific effective combinations were identified including the previously identified effective combination of crizotinib and EGFR inhibitor. One patient derived model of acquired resistance to LDK378 was profoundly sensitive to LDK378 is the presence of MAPK pathway inhibitors. In this model the combination is required to effectively inhibit downstream signaling, promote apoptosis and cause cell death.
Of particular interest, the combination of Src and ALK inhibition was effective in a six of nine patient derived models of acquired resistance to single agent ALK inhibitors (this effect was specific for ALK+ lines and not seen in parallel studies done with EGFR models of acquired resistance). The Src inhibitor sarcatinib restored sensitivity to patient derived ALK+ cell lines with acquired resistance to crizotinib. The combination promotes apoptosis and is effective both in vitro and in vivo. Finally, crizotinib results in robust upregulation of Src signaling demonstrating the adaptive response these models undergo to survive in the absence of ALK mediated proliferation.
Thus, we have developed a novel approach to rapidly discover effective and novel drug combinations in patient derived cell lines of acquired resistance to ALK inhibition. The combination of ALK inhibition and Src inhibition is an attractive therapeutic strategy for clinical translation.
Citation Format: Adam S. Crystal, Jeffrey A. Engelman, Cyril H. Benes, Maria G. Gomez-Caraballo, Rosa Frias, Elizabeth Lockerman, Alice T. Shaw. Discovery of novel targets for effective combination drug therapy in ALK+ NSCLC patient derived models of acquired resistance. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 3715. doi:10.1158/1538-7445.AM2014-3715