In vitro activity: The kinase most highly inhibited by LDN-214117 is ALK2 (IC50, 24 nM), followed by TNIK, RIPK2, and ABL1. LDN-214117 demonstrates selective inhibition of ALK2 and ALK1 in preference to ALK3 kinase activity. LDN-214117 exhibits relatively selective inhibition of BMP6 versus BMP2 or BMP4. In a cell-based assay, LDN-214117 exhibits a selective inhibition on BMP6 with IC50 of approximately 100 nM, and 164-fold selectivity for BMP6 versus TGF-β1.

Kinase Assay: Purified recombinant ALK2 proteins, ATP, ATP[γ-32P], and dephosphorylated casein at final concentrations of 2.5 nM, 6 μM, 0.05 μCi/μL , and 0.5 mg/mL, respectively, are aliquoted in kinase buffer containing 0.2% BSA supplemented with 10 mM MnCl2 into 96-microwell plates, in combination with inhibitor compounds diluted at varying concentrations (0.01 nM to 100 μM). Positive control samples lacking inhibitor compounds, and negative controls lacking recombinant kinase, are also measured. The mixture is reacted at RT for 45 min, quenched with a final concentration of 2% phosphoric acid. The reaction mixture is transferred to 96-well P81 phosphocellulose filter plates and bound for 5 min. The plates are washed 20 times with 150 μL of 1% phosphoric acid solution per well by vacuum manifold. Plates are dried at RT for 1 h, sealed, and assayed with Microscint 20 scintillation fluid using a Spectramax L luminometer. Data is normalized to positive controls at 100% enzyme activity, with negative controls being subtracted as background.

Cell Assay: Cells are seeded at 25000 cells per well in 96-well plates and incubated for 2 h at 37℃ and 5% CO2. Compounds of LDN-214117 or DMSO are diluted in DMEM and added at final compound concentrations of 1, 10, and 100 μM. Cells are incubated for 4 and 24 h, after which the media is discarded. Cells are lysed by adding 30 μL of passive lysis buffer and shaken at RT for 15 min. Cell viability is determined by quantifying the ATP present in each well by adding 10 μL of Cell Titer Glo per well and measuring the light output by Spectramax L luminometer. Data is normalized to 100% viability for cells receiving only DMSO.

J Med Chem. 2014 Oct 9;57(19):7900-15.