Abstract LB-324: First isoform selective inhibitor of FGFR4 for the treatment of genomically defined patients with hepatocellular carcinoma (2014)

Abstract Hepatocellular carcinoma (HCC) is the third leading cause of cancer deaths worldwide. Chemotherapy has proven ineffective, and Sorafenib remains the only approved targeted drug with no second or third line treatment options. Sorafenib slows the growth of advanced liver cancers and helps some patients live longer - by an average of about three months. There is a pressing need for more effective therapies. FGF19 is a highly controlled hormone normally expressed in the intestine, that acts in the liver to regulate bile acid synthesis and hepatocyte proliferation via activation of FGFR4. In 7% of patients with HCC, FGF19 is contained within a focal amplification on chromosome 11q13.3. Overexpression of FGF19 in transgenic mice produces liver tumors which are sensitive to treatment with a FGFR4 tool antibody. Additionally, the growth of tumor cells in xenograft models with FGF19 amplification is dependent on FGFR4 signaling. Thus, selective inhibition of FGFR4 might represent a viable strategy for treating this genetically defined subgroup of HCC patients. Herein, we describe our efforts to identify an ultraselective small molecule inhibitor of FGFR4 which spares the other FGFR isoforms with the intent to avoid FGFR1-3 driven, dose limiting toxicities like soft tissue mineralization. Utilizing structure based drug design, we prepared a series of inhibitor templates designed to covalently modify a target cysteine residue present in FGFR4, but not the other FGFR isoforms. Optimization of one of these templates led to the identification of BLU9931, a highly potent and exquisitely selective, covalent inhibitor of FGFR4. BLU9931 persistently inhibits FGFR4 mediated signaling in cancer cells as evidenced by decreased phosphorylation of FRS2 and ERK. Importantly, BLU9931 does not block signaling driven by FGFR1. Upon oral dosing in mice, BLU9931 is well tolerated and demonstrates robust and dose dependent induction of the FGFR4 target gene CYP7a1 in Hep3B cells, a FGF19 amplified HCC xenograft model. Upon extended dosing, BLU9931 causes sustained regression of tumors, including complete responses. We then explored if HCCs with alterations other than FGF19 amplification are also dependent on FGFR4 signaling. Dosing of molecularly annotated patient derived HCC xenografts with BLU9931 suggests that selective targeting of FGFR4 represents a viable option for the treatment of an expanded population segment of genomically defined HCC patients, much larger than originally anticipated. Citation Format: Margit Hagel, Chandra Miduturu, Mike Sheets, Weifan Weng, Nooreen Rubin, Neil Bifulco, Lucian DiPietro, Joseph Kim, Natasja Brooijmans, Nicolas Stransky, Christopher Winter, Christoph Lengauer, Timothy Guzi. First isoform selective inhibitor of FGFR4 for the treatment of genomically defined patients with hepatocellular carcinoma. [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 LB-324. doi:10.1158/1538-7445.AM2014-LB-324