Huang, ZhifengLi, XiaokunTan, LiWang, HuiyanLiu, YangBlais, StevenDeng, JingjingNeubert, Thomas A.Gray, NathanaelMohammadi, Moosa2015-11-032014Huang, Zhifeng, Li Tan, Huiyan Wang, Yang Liu, Steven Blais, Jingjing Deng, Thomas A. Neubert, Nathanael S. Gray, Xiaokun Li, and Moosa Mohammadi. 2014. “DFG-out Mode of Inhibition by an Irreversible Type-1 Inhibitor Capable of Overcoming Gate-Keeper Mutations in FGF Receptors.” ACS Chemical Biology 10 (1): 299-309. doi:10.1021/cb500674s. http://dx.doi.org/10.1021/cb500674s.1554-8929http://nrs.harvard.edu/urn-3:HUL.InstRepos:23474078Drug-resistance acquisition through kinase gate-keeper mutations is a major hurdle in the clinic. Here, we determined the first crystal structures of the human FGFR4 kinase domain (FGFR4K) alone and complexed with ponatinib, a promiscuous type-2 (DFG-out) kinase inhibitor, and an oncogenic FGFR4K harboring the V550L gate-keeper mutation bound to FIIN-2, a new type-1 irreversible inhibitor. Remarkably, like ponatinib, FIIN-2 also binds in the DFG-out mode despite lacking a functional group necessary to occupy the pocket vacated upon the DFG-out flip. Structural analysis reveals that the covalent bond between FIIN-2 and a cysteine, uniquely present in the glycine-rich loop of FGFR kinases, facilitates the DFG-out conformation, which together with the internal flexibility of FIIN-2 enables FIIN-2 to avoid the steric clash with the gate-keeper mutation that causes the ponatinib resistance. The structural data provide a blueprint for the development of next generation anticancer inhibitors through combining the salient inhibitory mechanisms of ponatinib and FIIN-2.en-USArticlesJournal Article2015-11-0310.1021/cb500674s