Rotational Freedom, Steric Hindrance, and Protein Dynamics Explain BLU554 Selectivity for the Hinge Cysteine of FGFR4

Exploring FGFR signaling inhibition as a promising approach in breast cancer treatment

As our grasp of cancer genomics deepens, we are steadily progressing towards the domain of precision medicine, where targeted therapy stands out as a revolutionary breakthrough in the landscape of cancer therapeutics. The fibroblast growth factor receptors (FGFR) pathway has been unveiled as a fundamental instigator in the pathophysiological mechanisms underlying breast carcinoma, paving the way for the exhilarating development of precision-targeted therapeutics. In the pursuit of exploring inhibitors that specifically target the FGFR signaling pathways, a multitude of kinase inhibitors targeting FGFR has been assiduously engineered to address the heterogeneous landscape of human malignancies. This review offers an exhaustive exploration of aberrations within the FGFR pathway and their functional implications in breast cancer. Additionally, we delve into cutting-edge therapeutic approaches for the treatment of breast cancer patients bearing FGFR alterations and the management of toxicity associated with FGFR inhibitors. Furthermore, our contemplation of the evolution of cutting-edge FGFR inhibitors foresees their potential to spearhead innovative therapeutic approaches in the ongoing combat against cancer.

Design, synthesis, and biological evaluation of selective covalent inhibitors of FGFR4

Aberrant signaling via fibroblast growth factor 19 (FGF19)/fibroblast growth factor receptor 4 (FGFR4) has been identified as a driver of tumorigenesis and the development of many solid tumors, making FGFR4 is a promising target for anticancer therapy. Herein, we designed and synthesized a series of bis-acrylamide covalent FGFR4 inhibitors and evaluated their inhibitory activity against FGFRs, FGFR4 mutants, and their antitumor activity. CXF-007, verified by mass spectrometry and crystal structures to form covalent bonds with Cys552 of FGFR4 and Cys488 of FGFR1, exhibited stronger selectivity and potent inhibitory activity for FGFR4 and FGFR4 cysteine mutants. Moreover, CXF-007 exhibited significant antitumor activity in hepatocellular carcinoma cell lines and breast cancer cell lines through sustained inhibition of the FGFR4 signaling pathway. In summary, our study highlights a novel covalent FGFR4 inhibitor, CXF-007, which has the potential to overcome drug-induced FGFR4 mutations and might provide a new strategy for future anticancer drug discovery.

Insight into the design of FGFR4 selective inhibitors in cancer therapy: Prospects and challenges

Recently, FGFR4 has become a hot target for the treatment of cancer owing to its important role in cellular physiological processes. FGFR4 has been validated to be closely related to the occurrence of cancers, such as hepatocellular carcinoma, rhabdomyosarcoma, breast cancer and colorectal cancer. Hence, the development of FGFR4 small-molecule inhibitors is essential to further understanding the functions of FGFR4 in cancer and the treatment of FGFR4-dependent diseases. Given the particular structures of FGFR1-4, the development of FGFR4 selective inhibitors presents significant challenges. The non-conserved Cys552 in the hinge region of the FGFR4 complex becomes the key to the selectivity of FGFR4 and FGFR1/2/3 inhibitors. In this review, we systematically introduce the close relationship between FGFR4 and cancer, and conduct an in-depth analysis of the developing methodology, binding mechanism, kinase selectivity, pharmacokinetic characteristics of FGFR4 selectivity inhibitors, and their application in clinical research.

Discovery of Novel 7-Azaindole Derivatives as Selective Covalent Fibroblast Growth Factor Receptor 4 Inhibitors for the Treatment of Hepatocellular Carcinoma

Fibroblast growth factor receptor 4 (FGFR4) has been identified as a potential target for the treatment of hepatocellular carcinoma (HCC) with aberrant FGFR4 signaling because of its important role in HCC progression and development. Several FGFR4 inhibitors are under clinical development. Using a 7-azaindole scaffold, we discovered a series of novel selective and covalent FGFR4 inhibitors by performing a structure-based design approach. Representative compounds 24 and 30 exhibited potent FGFR4 inhibition and high selectivity among kinases. Western blot analysis showed that compounds 24 and 30 significantly inhibited the FGF19/FGFR4 signaling pathway in HuH-7 cells and effectively suppressed the proliferation of HuH-7 HCC cells and MDA-MB-453 breast cancer cells. Moreover, compound 30 exhibited significant in vivo antitumor activity in a mouse HuH-7 xenograft model. Thus, compound 30 and the 7-azaindole scaffold can be applied to develop anticancer agents for the treatment of cancers characterized by aberrant FGFR4 signaling.

6-Amino-2,4,5-trimethylpyridin-3-ol and 2-amino-4,6-dimethylpyrimidin-5-ol derivatives as selective fibroblast growth factor receptor 4 inhibitors: design, synthesis, molecular docking, and anti-hepatocellular carcinoma efficacy evaluation

A novel series of aminotrimethylpyridinol and aminodimethylpyrimidinol derivatives were designed and synthesised for FGFR4 inhibitors. Structure-activity relationship on the FGFR4 inhibitory activity of the new compounds was clearly elucidated by an intensive molecular docking study. Anti-cancer activity of the compounds was evaluated using hepatocellular carcinoma (HCC) cell lines and a chick chorioallantoic membrane (CAM) tumour model. Compound 6O showed FGFR4 inhibitory activity over FGFR1 - 3. Compared to the positive control BLU9931, compound 6O exhibited at least 8 times higher FGFR4 selectivity. Strong anti-proliferative activity of compound 6O was observed against Hep3B, an HCC cell line which was a much more sensitive cell line to BLU9931. In vivo anti-tumour activity of compound 6O against Hep3B-xenografted CAM tumour model was almost similar to BLU9931. Overall, compound 6O, a novel derivative of aminodimethylpyrimidinol, was a selective FGFR4 kinase inhibitor blocking HCC tumour growth.

Structure-based design of a dual-warhead covalent inhibitor of FGFR4

The fibroblast growth factor 19 (FGF19)/fibroblast growth factor receptor 4 (FGFR4) signaling pathways play critical roles in a variety of cancers, such as hepatocellular carcinoma (HCC). FGFR4 is recognized as a promising target to treat HCC. Currently, all FGFR covalent inhibitors target one of the two cysteines (Cys477 and Cys552). Here, we designed and synthesized a dual-warhead covalent FGFR4 inhibitor, CXF-009, targeting Cys477 and Cys552 of FGFR4. We report the cocrystal structure of FGFR4 with CXF-009, which exhibits a dual-warhead covalent binding mode. CXF-009 exhibited stronger selectivity for FGFR4 than FGFR1-3 and other kinases. CXF-009 can also potently inhibit the single cystine mutants, FGFR4(C477A) and FGFR4(C552A), of FGFR4. In summary, our study provides a dual-warhead covalent FGFR4 inhibitor that can covalently target two cysteines of FGFR4. CXF-009, to our knowledge, is the first reported inhibitor that forms dual-warhead covalent bonds with two cysteine residues in FGFR4. CXF-009 also has the potential to overcome drug induced resistant FGFR4 mutations and might serve as a lead compound for future anticancer drug discovery.

Design, Synthesis, and Biological Evaluation of 2-Formyl Tetrahydronaphthyridine Urea Derivatives as New Selective Covalently Reversible FGFR4 Inhibitors

Aberrant FGF19/FGFR4 signaling is an oncogenic driver force for the development of human hepatocellular carcinoma (HCC). A series of 2-formyl tetrahydronaphthyridine urea derivatives were designed and synthesized as new covalently reversible inhibitors of FGFR4. The representative compound 9ka exhibited an IC₅₀ value of 5.4 nM against FGFR4 and demonstrated extraordinary kinome selectivity. Compound 9ka also exhibited good oral pharmacokinetic properties with an AUC_(0-t) value of 38 950.06 h·ng/mL, a T_1/2 value of 3.06 h, and an oral bioavailability of 50.97%, at an oral dose of 25 mg/kg in Sprague-Dawley (SD) rats. Furthermore, compound 9ka induced significant tumor regressions in a xenograft mouse model of Hep3B2.1-7 HCC cell line without an obvious sign of toxicity upon 30 mg/kg oral administration. Compound 9ka may serve as a promising lead compound for further anticancer drug development.

Discovery of Cysteine-targeting Covalent Protein Kinase Inhibitors

Small molecule covalent kinase inhibitors (CKIs) have entered a new era in drug discovery, which have the advantage for sustained target inhibition and high selectivity. An increased understanding of binding kinetics of CKIs and discovery of additional irreversible and reversible-covalent cysteine-targeted warheads has inspired the development of this area. Herein, we summarize the major medicinal chemistry strategies employed in the discovery of these representative CKIs, which are categorized by the location of the target cysteine within seven main regions of the kinase: the front region, the glycine rich loop (P-loop), the hinge region, the DFG region, the activation loop (A-loop), the catalytic loop (C-loop), and the remote loop. The emphasis is placed on the design and optimization strategies of CKIs that are generated by addition of a warhead to a reversible lead/inhibitor scaffold. In addition, we address the challenges facing this area of drug discovery.

Way to Enforce Selectivity via Steric Hindrance: Improvement of Am(III)/Eu(III) Solvent Extraction by Loaded Diphosphonic Acid Esters

Hybrid donor extractants are a promising class of compounds for the separation of trivalent actinides and lanthanides. Here, we investigated a series of sterically loaded diphosphonate ligands based on bipyridine (BiPy-PO-iPr and BiPy-PO-cHex) and phenanthroline (Phen-PO-iPr and Phen-PO-cHex). We studied their complex formation with nitrates of trivalent f-elements in solvent extraction systems (Am and Eu) and homogeneous acetonitrile solutions (Nd, Eu, and Lu). Phenanthroline extractants demonstrated the highest efficiency and selectivity [SF(Am/Eu) up to 14] toward Am(III) extraction from nitric acid solutions among all of the studied diphosphonates of N-heterocycles. The binding constants established by UV-vis titration also indicated stronger binding of sterically impaired diphosphonates compared to the primary substituted diphosphonates. NMR titration and slope analysis during solvent extraction showed the formation of 2:1 complexes at high concentrations (>10^-3 mol/L) for phenanthroline-based ligands. According to UV-vis titrations at low concentrations (10^-5-10^-6 mol/L), the phenanthroline-based ligands formed 1:1 complexes. Bipyridine-based ligands formed 1:1 complexes regardless of the ligand concentration. Luminescence titrations revealed that the quantum yields of the complexes with Eu(III) were 81 ± 8% (BiPy-PO-iPr) and 93 ± 9% (Phen-PO-iPr). Single crystals of the structures [Lu(μ²,κ⁴-(iPrO)₂P(O)Phen(O)₂(OiPr))(NO₃)₂]₂ and Eu(Phen-PO-iPr)(NO₃)₃ were obtained by chemical synthesis with the Phen-PO-iPr ligand. X-ray diffraction studies revealed a closer contact of the f-element with the aromatic N atoms in the case of sterically loaded P═O ligands compared with sterically deficient ligands. Density functional theory calculations allowed us to rationalize the observed selectivity trends in terms of the bond length, Mayer bond order, and preorganization energy.

Selective FGFR/FGF pathway inhibitors: inhibition strategies, clinical activities, resistance mutations, and future directions

Introduction: Fibroblast growth factor receptor (FGFR)/fibroblast growth factor (FGF) is a pathway characterized by recurring alterations in cancer. Its dysregulations enhance cancer cell proliferation, survival, migration and invasion, as well as angiogenesis and immune evasion.Areas covered: FGFR/FGF selective inhibitors belong to a broad class of drugs with some being approved for specific indications and others under investigation in ongoing phase I and II clinical trials. In this review, all available clinical data from trials on selective FGFR/FGF inhibitors as well as described resistance mutations and mechanisms are presented. FGFR/FGF pathway inhibitors are classified according to the mechanism they employ to dampen/suppress signaling and to the preferred FGFR binding mode when X-ray crystal structure is available.Expert opinion: Data presented suggests the general actionability of FGFR1,2,3 mutations and fusions across histologies, whereas FGFR1,2,3 amplifications alone are poor predictors of response to tyrosine kinase inhibitors. Overexpression on immunohistochemistry (IHC) of FGF19, the stimulatory ligand of FGFR4, can predict response to FGFR selective inhibitors in hepatocellular carcinoma. Whereas IHC overexpression of FGFR1,2,3 is not sufficient to predict benefit from FGFR inhibitors across solid tumors. FGFR1,2,3 mRNA overexpression can predict response even in absence of structural alteration. Data on resistance mutations suggests the need for new inhibitors to overcome gatekeeper mutations.

Discovery and Optimization of a Novel 2H-Pyrazolo[3,4-d]pyrimidine Derivative as a Potent Irreversible Pan-Fibroblast Growth Factor Receptor Inhibitor

Fibroblast growth factor receptors (FGFRs) have become promising therapeutic targets in various types of cancers. In fact, several selective irreversible inhibitors capable of covalently reacting with the conserved cysteine of FGFRs are currently being evaluated in clinical trials. In this article, we optimized and discovered a novel lead compound 36 with remarkable inhibitory effects against FGFR (1-3), which is a derivative of 2H-pyrazolo[3,4-d]pyrimidine. The irreversible binding to FGFRs was characterized by LC-MS. This compound has been shown to exhibit significant anti-proliferation effects against NCI-H1581 and SNU-16 cancer cell lines both in vitro and in vivo. Compound 36 has also demonstrated a low toxicity profile and adequate pharmacokinetic properties and is currently under validation as a potential drug candidate.

Discovery of a Potent Degrader for Fibroblast Growth Factor Receptor 1/2

Aberrant activation of FGFR signaling occurs in many cancers, and ATP-competitive FGFR inhibitors have received regulatory approval. Despite demonstrating clinical efficacy, these inhibitors exhibit dose-limiting toxicity, potentially due to a lack of selectivity amongst the FGFR family and are poorly tolerated. Here, we report the discovery and characterization of DGY-09-192, a bivalent degrader that couples the pan-FGFR inhibitor BGJ398 to a CRL2^VHL E3 ligase recruiting ligand, which preferentially induces FGFR1&2 degradation while largely sparing FGFR3&4. DGY-09-192 exhibited two-digit nanomolar DC₅₀ s for both wildtype FGFR2 and several FGFR2-fusions, resulting in degradation-dependent antiproliferative activity in representative gastric cancer and cholangiocarcinoma cells. Importantly, DGY-09-192 induced degradation of a clinically relevant FGFR2 fusion protein in a xenograft model. Taken together, we demonstrate that DGY-09-192 has potential as a prototype FGFR degrader.

Advances of Fibroblast Growth Factor/Receptor Signaling Pathway in Hepatocellular Carcinoma and its Pharmacotherapeutic Targets

Hepatocellular carcinoma (HCC) is a type of primary liver cancer with poor prognosis, and its incidence and mortality rate are increasing worldwide. It is refractory to conventional chemotherapy and radiotherapy owing to its high tumor heterogeneity. Accumulated genetic alterations and aberrant cell signaling pathway have been characterized in HCC. The fibroblast growth factor (FGF) family and their receptors (FGFRs) are involved in diverse biological activities, including embryonic development, proliferation, differentiation, survival, angiogenesis, and migration, etc. Data mining results of The Cancer Genome Atlas demonstrate high levels of FGF and/or FGFR expression in HCC tumors compared with normal tissues. Moreover, substantial evidence indicates that the FGF/FGFR signaling axis plays an important role in various mechanisms that contribute to HCC development. At present, several inhibitors targeting FGF/FGFR, such as multikinase inhibitors, specific FGFR4 inhibitors, and FGF ligand traps, exhibit antitumor activity in preclinical or early development phases in HCC. In this review, we summarize the research progress regarding the molecular implications of FGF/FGFR-mediated signaling and the development of FGFR-targeted therapeutics in hepatocarcinogenesis.

Investigation of Covalent Warheads in the Design of 2-Aminopyrimidine-based FGFR4 Inhibitors

Covalent kinase inhibitors are rapidly emerging as a class of therapeutics with clinical benefits. Herein we report a series of selective 2-aminopyrimidine-based fibroblast growth factor receptor 4 (FGFR4) inhibitors exploring different types of cysteine-targeting warheads. The structure-activity relationship study revealed that the chemically tuned warheads α-fluoro acrylamide, vinylsulfonamide, and acetaldehyde amine were suitable as covalent warheads for the design of selective FGFR4 inhibitors. Compounds 6a, 6h, and 6i selectively suppressed FGFR4 enzymatic activity with IC₅₀ values of 53 ± 18, 45 ± 11, and 16 ± 4 nM, respectively, while sparing FGFR1/2/3. X-ray crystal structure and MALDI-TOF studies demonstrated that compound 6h bearing the α-fluoro acrylamide binds to FGFR4 with an irreversible binding mode, whereas compound 6i with an acetaldehyde amine binds to FGFR4 with a reversible covalent mode. 6h and 6i might provide some fundamental structural information for the rational design of new selective FGFR4 inhibitors.

Design, synthesis, and biological evaluation of indazole derivatives as selective and potent FGFR4 inhibitors for the treatment of FGF19-driven hepatocellular cancer

Fibroblast growth factor receptor 4 (FGFR4) is a member of the fibroblast growth factor receptor family, which is closely related to the occurrence and development of hepatocellular carcinoma (HCC). In this article, a series of indazole derivatives were designed and synthesized by using computer-aided drug design (CADD) and structure-based design strategies, and then they were evaluated for their inhibition of FGFR4 kinase and antitumor activity. F-30 was subtly selective for FGFR4 compared to FGFR1; it affected cell growth and migration by inhibiting FGFR4 pathways in HCC cell lines in a dose-dependent manner.

Discovery of Roblitinib (FGF401) as a Reversible-Covalent Inhibitor of the Kinase Activity of Fibroblast Growth Factor Receptor 4

FGF19 signaling through the FGFR4/β-klotho receptor complex has been shown to be a key driver of growth and survival in a subset of hepatocellular carcinomas, making selective FGFR4 inhibition an attractive treatment opportunity. A kinome-wide sequence alignment highlighted a poorly conserved cysteine residue within the FGFR4 ATP-binding site at position 552, two positions beyond the gate-keeper residue. Several strategies for targeting this cysteine to identify FGFR4 selective inhibitor starting points are summarized which made use of both rational and unbiased screening approaches. The optimization of a 2-formylquinoline amide hit series is described in which the aldehyde makes a hemithioacetal reversible-covalent interaction with cysteine 552. Key challenges addressed during the optimization are improving the FGFR4 potency, metabolic stability, and solubility leading ultimately to the highly selective first-in-class clinical candidate roblitinib.