Approaches to selective fibroblast growth factor receptor 4 inhibition through targeting the ATP-pocket middle-hinge region

Abstract

A diverse range of selective FGFR4 inhibitor hit series were identified using unbiased screening approaches and by the modification of known kinase inhibitor scaffolds. In each case the origin of the selectivity was consistent with an interaction with a poorly conserved cysteine residue within the middle-hinge region of the kinase domain of FGFR4, at position 552. Targeting this region identified a non-covalent diaminopyrimidine series differentiating by size, an irreversible-covalent inhibitor in which Cys552 undergoes an SNAr reaction with a 2-chloropyridine, and a reversible-covalent inhibitor series in which Cys552 forms a hemithioacetal adduct with a 2-formyl naphthalene. In addition, the introduction of an acrylamide into a known FGFR scaffold identified a pan-FGFR inhibitor which reacted with both Cys552 and a second poorly conserved cysteine on the P-loop of FGFR4 at position 477 which is present in all four FGFR family members.

H3B-6527 Is a Potent and Selective Inhibitor of FGFR4 in FGF19-Driven Hepatocellular Carcinoma

“…Covalent inhibitors directed against a cysteine have recently been developed for other kinases such as Bruton tyrosine kinase (BTK) and EGFR and their success in the clinic has renewed the enthusiasm for covalent inhibitors in cancer therapy (46). Currently, there are three other FGFR4selective covalent compounds undergoing preclinical and clinical evaluation where the safety and efficacy as a monotherapy will be explored (47)(48)(49)(50).…”

Fibroblast Growth Factor Receptors (FGFRs): Structures and Small Molecule Inhibitors

“…A number of FGFR covalent inhibitors have been developed, and some of those agents are already in clinical trials (see Table 1 for details). Moreover, several irreversible inhibitor/FGFR structures have been revealed by crystal structures, including FGFR4/BLU9931 (PDB ID: 4XCU) [84], FGFR4/FIIN-3 (PDB ID: 4R6V) [73], FGFR4/FIIN-2 (PDB ID: 4QQ5) [85], FGFR4/CGA159527 (PDB ID: 5NUD) [86], FGFR1(Y563C)/H3B-6527 (PDB ID: 5VND) [86], and FGFR1/TAS-120 (PDB ID: 6MZW) [54].…”

2-Formylpyridyl Ureas as Highly Selective Reversible-Covalent Inhibitors of Fibroblast Growth Factor Receptor 4

“…2 More recently, FGF19 signaling through FGFR4, which also requires the presence of the coreceptor β-klotho, has been highlighted as a driver in a subset of solid tumors, in particular hepatocellular carcinoma (HCC). 3 As a result, a number of groups have sought to identify selective inhibitors of FGFR4 signaling as a way to treat these cancers while avoiding the on-target side-effects associated with FGFR1−3 inhibition 4 and, in particular, FGF23-mediated hyperphosphatemia. 5 Selective agents have the potential to not only be better tolerated than pan-FGFR inhibitors but also to enable the impact of more robust inhibition of FGFR4 to be investigated.…”

“…To explore this possibility, we, and others, have identified a poorly conserved cysteine residue within the middle-hinge region of the FGFR4 ATP binding pocket that can be targeted to gain selectivity. 4 Cys552 is situated two positions beyond the gate-keeper (GK+2) residue in FGFR4 and presents an opportunity for selectivity based upon the relatively small size of the side chain, or as a nucleophile for covalent binding. The other FGFR family members possess a tyrosine at the GK+2 position, and within the human kinome, only 12 other kinases have an equivalent sized, or smaller residue, at this position, of which only four contain a cysteine.…”

“…However, the intramolecular H-bond was also believed to be an important conformational restraint for FGFR4 activity. 4 The introduction of sp 3 -hybridized atoms into the quinoline moiety was explored as a way to reduce the molecules coplanar aromatic nature, and as a result, the efficiency of intermolecular interactions within the solid state. 11 Morphing the quinoline amide moiety to the corresponding tetrahydronaphthyridine urea (THNU) generated the analogue 6a.…”