Abstract 2647: Merestinib (LY2801653), targeting several oncokinases including NTRK1/2/3, shows potent anti-tumor effect in colorectal cell line- and patient-derived xenograft (PDX) model bearing TPM3-NTRK1 fusion

In cancer, the formation of chimeric gene fusions by genomic rearrangement causes aberrant receptor tyrosine kinase activation resulting in sustained oncogenic signaling driving tumorigenesis. Neurotrophic tyrosine receptor kinase 1 (NTRK1), the cognate receptor for nerve growth factor (NGF), has been reported in 7 tumor types as a NTRK1 kinase domain fused with several reported partners including the 5’ coiled-coil domain of the tropomysin TPM3 gene. The resultant NTRK1 fusion protein is present in about 1.5% of colorectal cancer (CRC), 3% of lung and 12% of papillary thyroid cancers. In addition, gene fusions involving NTRK2 and NTRK3 are present in about 19 different tumor types. Thus pharmacologically targeting NTRK kinase in cancers bearing NTRK fusions may provide treatment options to patients who otherwise might be resistant to standard oncolytic regimens. Merestinib (LY2801653) is an orally bioavailable small molecule inhibitor of several oncokinases, including MET, AXL, ROS1 and MKNK1/2. Merestinib and its two primary metabolites, M1 (LSN2800870) and M2 (LSN2887652) were shown in scanMaxSM kinase binding assays to inhibit all three NTRKs with an IC50 ranging from 15-320 nM, and in the cell-based PathHunter® NTRK1 assay with an IC50 ranging from 12-92 nM. Merestinib, M1 and M2 were evaluated in vitro in TPM3-NTRK1 fusion bearing CRC cells (KM-12). Merestinib, M1 and M2 reduced p-NTRK1 levels, cell proliferation (IC50 of 11 nM, 18 nM and 100 nM respectively) and anchorage independent growth (IC50 of 45 nM, 79 nM and 206 nM respectively). Crizotinib previously reported (Nat Med. 2013;19:1469-72) to have moderate activity against NTRK1, was used to treat a patient with NTRK1 fusion resulted with transient response. Crizotinib was shown here to also reduce p-NTRK1 levels, cell proliferation (IC50 = 88nM) and anchorage independent growth (IC50 = 276nM) in vitro in KM-12 cells. Merestinib treatment at 24 mg/kg once daily arrested tumor growth (T/C = 4%) in KM-12 xenograft tumor bearing mice. Crizotinib administered at 25 mg/kg twice daily in this same model did not result in tumor growth arrest (T/C = 39.5%). Merestinib treatment at 24 mg/kg once daily led to tumor regression in a CRC PDX xenograft model (EL1989) bearing the TPM3-NTRK1 fusion. Crizotinib treatment at 25 mg/kg twice daily in this model did not show tumor regression. Further pre-clinical studies of Merestinib inhibition of NTRK2 and NTRK3 gene fusion are ongoing. These data support the clinical evaluation of Merestinib in patients with tumors harboring NTRK fusion. Merestinib is currently being studied clinically in advanced cancers (NCT01285037). Citation Format: Bruce W. Konicek, Steve M. Bray, Andrew R. Capen, John N. Calley, Kelly M. Credille, Philip J. Ebert, Gary Heady, Bharvin K. Patel, Victoria L. Peek, Jennifer R. Stephens, Suzane L. Um, Melinda D. Willard, Isabella H. Wulur, Yi Zeng, Richard A. Walgren, Sau-Chi Betty Yan. Merestinib (LY2801653), targeting several oncokinases including NTRK1/2/3, shows potent anti-tumor effect in colorectal cell line- and patient-derived xenograft (PDX) model bearing TPM3-NTRK1 fusion. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 2647.