FIIN-2

FIIN-2 is an irreversible inhibitor of FGFR1–4 with IC50 values of 3.1, 4.3, 27, and 45 nM, respectively. FIIN-2 also moderately inhibited EGFR, with an IC50 of 204 nM. The Cys491 of FGFR2 is the primary labeled site for FIIN-2 binding [1].
FIIN-2 is the first class of inhibitors that can potently inhibit the proliferation of cells dependent upon the gatekeeper mutants of FGFR1 or FGFR2. The co-crystal structure of FGFR4 with FIIN-2 was reported, which unexpectedly exhibits a “DFG-out” covalent binding mode. FIIN-2 maintains the pyrimido[4,5-d] pyrimidinone core of FIIN-1 but removes the two chlorine atoms, which are crucial for FIIN-1’s potency against FGFR. FIIN-2 maintains the ability to form a covalent bond with the P-loop cysteine but alter the selectivity profile versus other kinases. Compared with FIIN-1, FIIN-2 displayed strong binding to FGFRs and exhibited good overall kinase selectivity. FIIN-2 exhibited much less affinity for EGFR, but FIIN-3 potently bound to WT EGFR and to a subset of EGFR mutants. [1]
FIIN-2 inhibited proliferation of FGFR1-4 Ba/F3 cells with EC50s in the nanomolar range and were especially potent against FGFR2, with EC50s in the 1-nM range. FIIN-2 also inhibited the FGFR2 V564M gatekeeper mutant Ba/F3 cells, with EC50s of 58 nM, whereas FIIN-1 and BGJ398 had EC50s of over 1.0 μM against this mutant. FIIN-2 showed good potency against gatekeeper mutant V564F. In contrast, FIIN-2 was fourfold less potent (EC50 of 506 nM). FIIN-2 was inactive up to a concentration of 1.8 μM against EGFR L858R. FIIN-2 showed rather poor potency against protein kinase FLT1 (FLT1). In WT FGFR2 Ba/F3 cells, FIIN-2 completely inhibited the FGFR2 autophosphorylation on mutations of Tyr656/657 and V564M at concentrations of 3 nM and 300 nM, respectively. [1]
Reference:
1.Tan L, Wang J, Tanizaki J et al. Development of covalent inhibitors that can overcome resistance to first-generation FGFR kinase inhibitors. Proc Natl Acad Sci U S A. 2014 Nov 11;111(45):E4869-77. doi: 10.1073/pnas.1403438111. Epub 2014 Oct 27.

Development of covalent inhibitors that can overcome resistance to first-generation FGFR kinase inhibitors.[Pubmed:25349422]

Proc Natl Acad Sci U S A. 2014 Nov 11;111(45):E4869-77.

The human FGF receptors (FGFRs) play critical roles in various human cancers, and several FGFR inhibitors are currently under clinical investigation. Resistance usually results from selection for mutant kinases that are impervious to the action of the drug or from up-regulation of compensatory signaling pathways. Preclinical studies have demonstrated that resistance to FGFR inhibitors can be acquired through mutations in the FGFR gatekeeper residue, as clinically observed for FGFR4 in embryonal rhabdomyosarcoma and neuroendocrine breast carcinomas. Here we report on the use of a structure-based drug design to develop two selective, next-generation covalent FGFR inhibitors, the FGFR irreversible inhibitors 2 (FIIN-2) and 3 (FIIN-3). To our knowledge, FIIN-2 and FIIN-3 are the first inhibitors that can potently inhibit the proliferation of cells dependent upon the gatekeeper mutants of FGFR1 or FGFR2, which confer resistance to first-generation clinical FGFR inhibitors such as NVP-BGJ398 and AZD4547. Because of the conformational flexibility of the reactive acrylamide substituent, FIIN-3 has the unprecedented ability to inhibit both the EGF receptor (EGFR) and FGFR covalently by targeting two distinct cysteine residues. We report the cocrystal structure of FGFR4 with FIIN-2, which unexpectedly exhibits a "DFG-out" covalent binding mode. The structural basis for dual FGFR and EGFR targeting by FIIN3 also is illustrated by crystal structures of FIIN-3 bound with FGFR4 V550L and EGFR L858R. These results have important implications for the design of covalent FGFR inhibitors that can overcome clinical resistance and provide the first example, to our knowledge, of a kinase inhibitor that covalently targets cysteines located in different positions within the ATP-binding pocket.

FGFR inhibitors: Effects on cancer cells, tumor microenvironment and whole-body homeostasis (Review).[Pubmed:27245147]

Int J Mol Med. 2016 Jul;38(1):3-15.

Fibroblast growth factor (FGF)2, FGF4, FGF7 and FGF20 are representative paracrine FGFs binding to heparan-sulfate proteoglycan and fibroblast growth factor receptors (FGFRs), whereas FGF19, FGF21 and FGF23 are endocrine FGFs binding to Klotho and FGFRs. FGFR1 is relatively frequently amplified and overexpressed in breast and lung cancer, and FGFR2 in gastric cancer. BCR-FGFR1, CNTRL-FGFR1, CUX1-FGFR1, FGFR1OP-FGFR1, MYO18A-FGFR1 and ZMYM2-FGFR1 fusions in myeloproliferative neoplasms are non-receptor-type FGFR kinases, whereas FGFR1-TACC1, FGFR2-AFF3, FGFR2-BICC1, FGFR2-PPHLN1, FGFR3-BAIAP2L1 and FGFR3-TACC3 fusions in solid tumors are transmembrane-type FGFRs with C-terminal alterations. AZD4547, BGJ398 (infigratinib), Debio-1347 and dovitinib are FGFR1/2/3 inhibitors; BLU9931 is a selective FGFR4 inhibitor; FIIN-2, JNJ-42756493, LY2874455 and ponatinib are pan-FGFR inhibitors. AZD4547, dovitinib and ponatinib are multi-kinase inhibitors targeting FGFRs, colony stimulating factor 1 receptor (CSF1R), vascular endothelial growth factor (VEGF)R2, and others. The tumor microenvironment consists of cancer cells and stromal/immune cells, such as cancer-associated fibroblasts (CAFs), endothelial cells, M2-type tumor-associating macrophages (M2-TAMs), myeloid-derived suppressor cells (MDSCs) and regulatory T cells. FGFR inhibitors elicit antitumor effects directly on cancer cells, as well as indirectly through the blockade of paracrine signaling. The dual inhibition of FGF and CSF1 or VEGF signaling is expected to enhance the antitumor effects through the targeting of immune evasion and angiogenesis in the tumor microenvironment. Combination therapy using tyrosine kinase inhibitors (FGFR or CSF1R inhibitors) and immune checkpoint blockers (anti-PD-1 or anti-CTLA-4 monoclonal antibodies) may be a promising choice for cancer patients. The inhibition of FGF19-FGFR4 signaling is associated with a risk of liver toxicity, whereas the activation of FGF23-FGFR4 signaling is associated with a risk of heart toxicity. Endocrine FGF signaling affects the pathophysiology of cancer patients who are prescribed FGFR inhibitors. Whole-genome sequencing is necessary for the detection of promoter/enhancer alterations of FGFR genes and rare alterations of other genes causing FGFR overexpression. To sustain the health care system in an aging society, a benefit-cost analysis should be performed with a focus on disease-free survival and the total medical cost before implementing genome-based precision medicine for cancer patients.

DFG-out mode of inhibition by an irreversible type-1 inhibitor capable of overcoming gate-keeper mutations in FGF receptors.[Pubmed:25317566]

ACS Chem Biol. 2015 Jan 16;10(1):299-309.

Drug-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.

FIIN-2 is an irreversible inhibitor of FGFR with an IC50 of 3.1, 4.3, 27, and 45 nM for FGFR1, FGFR2, FGFR3 and FGFR4, respectively.

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