Effect of a high-fat meal on the relative bioavailability of H3B-6527, a novel FGFR4 inhibitor, in healthy volunteers

Discovery of novel FGFR4 inhibitors through a build-up fragment strategy

Hepatocellular carcinoma (HCC) is a leading cause of cancer-related death. FGFR4 has been implicated in HCC progression, making it a promising therapeutic target. We introduce an approach for identifying novel FGFR4 inhibitors by sequentially adding fragments to a common warhead unit. This strategy resulted in the discovery of a potent inhibitor, 4c, with an IC50 of 33 nM and high selectivity among members of the FGFR family. Although further optimisation is required, our approach demonstrated the potential for discovering potent FGFR4 inhibitors for HCC treatment, and provides a useful method for obtaining hit compounds from small fragments.

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

Aberration in FGFR4 signaling drives carcinogenesis and progression in a subset of hepatocellular carcinoma (HCC) patients, thereby making FGFR4 an attractive molecular target for this disease. Selective FGFR4 inhibition can be achieved through covalently targeting a poorly conserved cysteine residue in the FGFR4 kinase domain. We report mass spectrometry assays and cocrystal structures of FGFR4 in covalent complex with the clinical candidate BLU554 and with a series of four structurally related inhibitors that define the inherent reactivity and selectivity profile of these molecules. We further reveal the structure of FGFR1 with one of our inhibitors and show that off-target covalent binding can occur through an alternative conformation that supports targeting of a cysteine conserved in all members of the FGFR family. Collectively, we propose that rotational freedom, steric hindrance, and protein dynamics explain the exceptional selectivity profile of BLU554 for targeting FGFR4.

Correlation of the in vitro biotransformation of H3B-6527 in dog and human hepatocytes with the in vivo metabolic profile of 14C-H3B-6527 in a dog mass balance study

1. H3B-6527 is an orally available covalent small molecule inhibitor of FGFR4 undergoing evaluation in adults with hepatocellular carcinoma. Absorption, metabolism, transport and elimination of H3B-6527 were investigated in vitro and in a ¹⁴C-H3B-6527 beagle dog mass balance study.2. Following intravenous dosing in dogs, unchanged ¹⁴C-H3B-6527 represents only 1.6% of the total dose in excreta. The low amount of radioactivity in the dog urine (4.9% of the administered dose), suggests that renal elimination is a minor pathway of clearance for H3B-6527. A majority of the radioactivity was observed in the feces up to 5 days after dose administration, suggesting that drug-related material was secreted in the bile, and that H3B-6527 clearance was mostly driven by metabolism.3. In vitro, H3B-6527 is a substrate of GSTs, CYP3A and P-glycoprotein.4. The major pathways of metabolism were similar in human and dog hepatocytes, and occurred via glutathione (GSH) conjugations and sequential hydrolysis, N-deethylation and hydroxylation.5. The metabolic profile of H3B-6527 was qualitatively similar in dog hepatocytes and plasma/excreta.