Abstract 2954A: A potent and selective TRK inhibitor ONO-5390556, shows potent antitumor activity against both TRK-rearranged cancers and the resistant mutants

Purpose: TRKA/NTRK1, TRKB/NTRK2 and TRKC/NTRK3 belong to the neurotrophic tyrosine kinase receptor family and signals from TRK receptors play a role in neuronal survival and differentiation through activation of MAPK and AKT downstream pathways. Recently, oncogenic rearrangements of TRKA, B and C gene were identified in a variety of cancers, including lung adenocarcinoma, colorectal cancer, glioblastoma and acute myeloid leukemia. These genomic rearrangements resulted in sustained cancer cell proliferation. Recent studies indicate that targeting TRK by Entrectinib, pan-TRK, ALK and ROS1 inhibitor, may be effective in the treatment of cancers with TRK rearrangements. However, patients treated with Entrectinib showed resistance early due to NTRK1 harboring acquired mutations, G595R and G667C. ONO-5390556 is a selective pan-TRK inhibitor and shows highly potent anti-tumor activity against TRK rearranged cancers. We evaluated the anti-tumor activity of ONO-5390556 against NTRK1 rearranged cancer cells with harboring mutated G595R and G667C. Methods: The anti-tumor activity of ONO-5390556 was evaluated in subcutaneous xenograft tumor models of KM12, human colorectal cancer cell lines expressing TPM3-TRKA. ONO-5390556 was administered orally with doses ranging between 0.2 and 2 mg/kg once a day for 14 days. In vitro cytotoxic activity, cell viability was evaluated by WST-8 in TPM3-TRKA positive cells harboring mutated G595R and G667C. Phosphorylated proteins were detected by Western blotting. Results: In KM12 xenograft model, treatment with ONO-5390556 at doses of 0.2, 0.6, 2 mg/kg once a day resulted in a dose-dependent inhibition of tumor growth with Tumor Growth Inhibition (TGI) of 44.4, 86.6 and 95.4%, respectively. Both G595R and G667C mutations conferred resistance to Entrectinib, but were sensitive to ONO-5390556 with an IC50 of 2.7 and 0.2 nmol/L, respectively. Interestingly, the inhibitory activity of ONO-5390556 sustained in these mutations compared with wild type (IC50 of 0.4 nmol/L). ONO-5390556 strongly inhibited phosphorylation of the TRKA mutated. Additionally, Erk phosphorylation remained strongly inhibited in KM12 cells harboring mutated G595R. Conclusion: The oncogenic TRK fusion proteins are attractive therapeutic targets but two mutations acquired resistance has been found in the clinic. ONO-5390556 is a highly potent and selective pan-TRK inhibitor with evidence of an excellent anti-tumor activity not only in cancer cells harboring the TRKA