In vitro activity: In cells, SGC707 binds to PRMT3 and reduces PRMT3-dependent H4R3me2a. SGC707 also stabilizes PRMT3 in both HEK293 and A549 cells with EC50 values of 1.3 μM and 1.6 μM, respectively.

Kinase Assay: A radioactivity-based assay is optimized and used to determine the inhibition of PRMT3 in vitro. In a scintillation proximity assay (SPA), tritiated S-adenosylmethionine (3H-SAM) served as a methyl donor to methylate biotinylated histone peptide substrate. After completion of the reaction, the reaction mixture is transferred to the wells of a streptavidin / scintillant-coated microplate. The Biotinylated peptides binding to streptavidin coated resin, brings the incorporated 3H-methyl and the scintillant to close proximity. The amount of methylated peptide is quantified by tracing the radioactivity (counts per minute) as measured by the TopCount NXT(TM) Microplate Scintillation and Luminescence Counter. Due to the very acidic nature of the 3H-SAM solution, non-tritiated (cold) SAM is used to supplement the reactions. The C-terminally biotinylated peptide composed of the first 24 amino acids residues of histone H4 (H4 1-24) is used as substrate. The typical assay mixture contained 0.01% Tween-20, 5 mM DTT, 20 nM PRMT3, 0.3 μM B-H4 1-24 and 28 μM (5 μM3H-SAM plus 23 μM cold SAM) SAM in 20 mM Tris-HCl (pH 7.5) and a final volume of 20 μL. The IC50 values are determined at Km concentrations of both substrates by titration of the compound in the reaction mixture in a range between 2000-0.2 nM.

Cell Assay: Cells (LnCap, U2O s, HFF, MCF-7, and MDA-MB-231 cells) are seeded in 96-well plates and treated with different concentrations of SGC707 for 72 h. Cell viability is determined using Alamar blue 0.01 mg/mL in the media. Resazurin reduction is monitored with 544 nm excitation, measuring fluorescence at 590 nm.

Angew Chem Int Ed Engl. 2015 Apr 20;54(17):5166-70; Epigenomics. 2015;7(8):1327-38.