Abstract 3161: TPX-0005, an ALK/ROS1/TRK inhibitor, overcomes multiple resistance mechanisms by targeting SRC/FAK signaling
Authors: Zhai Dayong , Deng Wei , Huang John , Rogers Evan , Cui J. Jean 
Published: July 2017

Abstract
ALK, ROS1, and TRK inhibitors have achieved marked efficacy in treating cancer patients expressing abnormal ALK, ROS1 or NTRK genes. However, the initial success of these therapies is rapidly overshadowed with the development of acquired resistance. In addition, approximately 30-40% of ALK + or ROS1+ NSCLC patients fail to respond to initial crizotinib treatment, representing intrinsic resistance. Target gene amplification, acquired resistance mutations, bypass signaling, epithelial-mesenchymal transition (EMT) and metastasis are the common resistance mechanisms. None of the current ALK, ROS1 or TRK inhibitors can overcome bypass or EMT-based resistance when applied as a single agent therapy. TPX-0005 is a potent kinase inhibitor against WT and mutated ALK, ROS1 and TRK family kinases, especially the clinically significant solvent front mutations. At clinically relevant concentrations, TPX-0005 also inhibits JAK2, SRC and FAK that are important targets in modulating multiple resistance mechanisms. H2228 lung cancer cell line endogenously expresses EML4-ALK v3 and was reported to be resistant to ALK inhibitor TAE684. Upregulation of the bypass signaling kinase EGFR, EMT marker vimentin, and cancer stem-like marker CD44 was reported in H2228 cells, likely leading to intrinsic resistance to ALK inhibitors. In the anti-proliferation assay, both crizotinib and ceritinib were resistant in H2228 cells with IC50 values around 1000 nM, however, TPX-0005 was able to overcome the intrinsic resistance with an IC50 of 100 nM. In H2228 cells, TPX-0005 suppressed the phosphorylation of SRC, FAK and paxillin with IC50 values in a range of 80-100 nM, and downregulated the expression of EGFR, CD44, and vimentin with IC50 values around 100 nM. In addition, TPX-0005 inhibited the phosphorylation of the oncogenic transcription/translation factor YB-1 with an IC50 value around 100 nM in H2228 cells. YB-1 is involved in many aspects of gene expression control that lead to tumor cell growth and drug resistance, including modulation of EGFR upregulation, EMT, and cancer stemness. Therefore, it was postulated that inhibition of SRC/FAK by TPX-0005 suppressed the phosphorylation of YB-1, leading to the downregulation of EGFR, CD44 and vimentin, and eventually to anti-proliferation effect on H2228 cells. TPX-0005 demonstrated an in vitro anti-metastatic activity by inhibiting cell migration in both H2228 cells and HT1080 human fibrosarcoma cells. Taken together, the potent kinase inhibitory activities against SRC/FAK signaling provide a unique polypharmacology profile to TPX-0005 for combatting multiple resistance mechanisms simultaneously, including a broad spectrum of acquired mutations, bypass signaling, EMT, cancer stemness, and metastasis.
Citation Format: Dayong Zhai, Wei Deng, John Huang, Evan Rogers, J. Jean Cui. TPX-0005, an ALK/ROS1/TRK inhibitor, overcomes multiple resistance mechanisms by targeting SRC/FAK signaling [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 3161. doi:10.1158/1538-7445.AM2017-3161