BLU9931 is the first selective small molecule inhibitor of FGFR4.

FGFR1:591 nM, FGFR4:3 nM, FGFR3:150 nM, FGFR2:493 nM

FGFR1-4 Biochemical Assays: FGFR kinase inhibition assays are performed at KM for ATP. Picomolar to low nanomolar concentrations of FGFR proteins are incubated in 1× Kinase Reaction Buffer (KRB) with 1 μM of CSKtide and 50 to 250 of μM ATP at 25°C for 90 minutes in the presence or absence of a dosed concentration series of inhibitor. All reactions are terminated by the addition of Stop buffer, and plates are read on a Caliper EZReader2. IC50 values are fit with a four-parameter log[Inhibitor] versus response model with floating Hill Slope.

Established and PDX-derived HCC cell lines are seeded in 96-well plates in respective growth media, allowed to attach overnight, and treated with a dilution series of test compounds for two cell-doubling times. Cell viability is determined by CellTiter-Glo, and results represented as background-subtracted relative light units normalized to a DMSO-treated control. Relative EC50 values are determined at 50% inhibition between the top and bottom plateau of the dose–response curve.(Only for Reference)