In vitro activity: PD173074 is an ATP-competitive inhibitor of FGFR1 with Ki of ~40 nM. PD173074 is also an effective inhibitor of VEGFR2. Compared to FGFR1, PD173074 weakly inhibits the activities of Src, InsR, EGFR, PDGFR, MEK, and PKC with 1000-fold or greater IC50 values. PD173074 inhibits autophosphorylation of FGFR1 and VEGFR2 in a dose-dependent manner with IC50 of 1-5 nM and 100-200 nM, respectively. PD173074 inhibits FGF-2 promotion of granule neuron survival in a dose-dependent manner with IC50 of 12 nM, exhibiting 1,000-fold greater potency than that of SU 5402. PD173074 specifically inhibits FGF-2-mediated effects on proliferation, differentiation, and MAPK activation in oligodendrocyte (OL) lineage cells. PD173074 is active against the WT receptor and FGFR3 mutations in multiple myeloma (MM) cell lines. PD173074 also potently inhibits autophosphorylation of FGFR3 in a dose-dependent manner with IC50 of ~5 nM. PD173074 treatment potently reduces viability of FGFR3-expressing KMS11 and KMS18 cells with IC50 of<20 nM. Inhibition of aFGF-stimulated MM cell growth by PD173074 is highly correlated with the expression of FGFR3. PD173074 treatment completely abolishes NIH 3T3 transformation mediated by Y373C FGFR3 but not by Ras V12, demonstrating that PD173074 specifically targets FGFR3-mediated cell transformation and lacks nonspecific cytotoxic effect. PD173074 also induces functional maturation of KMS11 and KMS18 cells.

Kinase Assay: Assays using the full-length FGFR-1 kinase are performed in a total volume of 100 μL containing 25 mM HEPES buffer (pH 7.4), 150 mM NaCl, 10 mM MnCl2, 0.2 mM sodium orthovanadate, 750 μg/mL concentration of a random copolymer of glutamic acid and tyrosine (4:1), various concentrations of PD173074 and 60 to 75 ng of enzyme. The reaction is initiated by the addition of [γ-32P]ATP (5 μM ATP containing 0.4 μCi of [γ-32P]ATP per incubation), and samples are incubated at 25°C for 10 minutes. The reaction is terminated by the addition of 30% trichloroacetic acid and the precipitation of material onto glass-fiber filter mats. Filters are washed three times with 15% trichloroacetic acid, and the incorporation of [32P] into the glutamate tyrosine polymer substrate is determined by counting the radioactivity retained on the filters in a Wallac 1250 betaplate reader. Nonspecific activity is defined as radioactivity retained on the filters following incubation of samples without enzyme. Specific activity is determined as total activity (enzyme plus buffer) minus nonspecific activity. The concentration of PD173074 that inhibits FGFR-1 enzymatic activity by 50% (IC50) is determined graphically.

Cell Assay: PD 173074 dose-dependently inhibited autophosphorylation of FGFR1, with an IC50 value in the range of 1 ~ 5 nM. In addition, PD 173074 inhibited autophosphorylation of VEGFR2 with an IC50 value of 100 ~ 200 nM. Cells (KMS11 and KMS18) are incubated with increasing concentrations of PD173074 in the presence of aFGF/heparin for 48 hours. The percentage of viable cells is determined by MTT.

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