The FGF19-
fibroblast growth factor receptor (FGFR4)-βKlotho (KLB) pathway plays an important role in the regulation of
bile acid (BA) homeostasis. Aberrant activation of this pathway has been described in the development and progression of a subset of
liver cancers including
hepatocellular carcinoma, establishing FGFR4 as an attractive therapeutic target for such solid
tumors.
FGF401 is a highly selective FGFR4
kinase inhibitor being developed for
hepatocellular carcinoma, currently in phase I/II clinical studies. In preclinical studies in mice and dogs,
oral administration of
FGF401 led to induction of Cyp7a1, elevation of its peripheral marker
7alpha-hydroxy-4-cholesten-3-one, increased BA pool size, decreased serum
cholesterol and
diarrhea in dogs.
FGF401 was also associated with increases of serum
aminotransferases, primarily
alanine aminotransferase (ALT), in the absence of any observable adverse histopathological findings in the liver, or in any other organs. We hypothesized that the increase in ALT could be secondary to increased BAs and conducted an investigative study in dogs with
FGF401 and coadministration of the BA sequestrant
cholestyramine (CHO). CHO prevented and reversed FGF401-related increases in ALT in dogs in parallel to its ability to reduce BAs in the circulation. Correlation analysis showed that FGF401-mediated increases in ALT strongly correlated with increases in
taurolithocholic acid and
taurodeoxycholic acid, the major secondary BAs in dog plasma, indicating a mechanistic link between ALT elevation and changes in BA pool hydrophobicity. Thus, CHO may offer the potential to mitigate elevations in serum
aminotransferases in human subjects that are caused by targeted FGFR4 inhibition and elevated intracellular BA levels.