Abstract Introduction: Hepatocellular carcinoma (HCC) is the sixth most prevalent cancer and the second most frequent cause of cancer-related death, however, treatment options are very limited. In recent studies, aberrant signaling through FGFR4 and its ligand, FGF19 have been identified as the oncogenic driver in a subset of HCCs and reported to be associated with poor prognosis. About 30% of HCC patients have altered FGF19/FGFR4 pathway signaling, therefore, the treatment with FGFR4 inhibitor may produce benefit. Materials and Method: Using the structure-based design, we have generated a novel, potent and selective FGFR4 inhibitor, HM81422 with irreversible-covalent binding mode, and evaluated its anti-tumor activity in a variety of HCC cell lines, HCC cell line xenografts and orthotopic grafts. Results: Biochemical selectivity assays demonstrated that HM81422 is highly selective towards FGFR4 compared to other FGFR isotypes as well as a panel of several kinases. The treatment of HM81422 to FGF19 amplified and overexpressed HCC cell lines led to suppression of FGF19/FGFR4 signaling pathway and concomitant reduction in cell viability in dose-dependent manner. Oral administration of HM81422 to mice bearing FGF19 altered HCC cells showed dose-dependent pharmacokinetics, pharmacodynamic modulation of FGFR4 signaling and antitumor efficacy in xenograft models. And HM81422 demonstrated inhibition of tumor growth in an orthotopic liver xenograft model of FGF19 altered HCC in nude mice. Conclusion: In conclusion, the treatment of HCC patients with a potent and selective FGFR4 inhibitor, HM81422, can be an attractive approach targeting approximately 30% of HCC patients by inhibiting altered FGF19-mediated signaling cascade. Further preclinical studies with HM81422 will be performed and reported soon. Citation Format: JaeHo Lee, Hyunjeong Kang, Kyounghwa Koo, Youngeun Ha, Sun Young Lim, Joo-Yun Byun, Hyunkyung Yu, Taehun Song, Moonsub Lee, Seung Hyun Jung, Taewoo Kim, Hyojeong Bang, Eunyoung Kim, Jahoon Kang, Ho Jeong Lee, YoungHoon Kim, YoungGil Ahn, KweeHyun Suh, Sun-Jin Kim. A novel, potent and selective FGFR4 inhibitor, HM81422 in hepatocellular carcinoma with FGFR4-driven pathway activation [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 4780.