GSK1379725A (AU1)

GSK1379725A is an inhibitor of Brd4 and a selective BPTF ligand (Kd=2.8 μM).

From the NMR titration of GSK1379725A, the bound and unbound resonances are separated by 171 Hz, providing an upper bound for the chemical exchange rate. Assuming an association rate of 1×108 M-1 s-1 as a high end for a range of protein-small molecule interactions, (e.g., chymotrypsin: proflavin k1=1.2×108 M-1 s-1), an upper Kd of 8 μM is estimated from this experiment. For a more accurate determination with a non-fluorinated protein, ITC is used as a complementary direct binding assay using unlabeled BPTF. A Kd of 2.8 μM is obtained, consistent with our intermediate exchange resonance broadening by PrOF NMR. Although GSK1379725A has been demonstrated to be selective over Brd4, a full selectivity panel against other bromodomains will be needed. A database search using ChEMBL only showed GSK1379725A to be active in five cellular assays with an EC50 of 500 nM carried out. Additionally, no kinase activity has been reported for GSK1379725A despite the growing screening use of the PKIS library[1].

[1]. Urick AK, et al. Dual Screening of BPTF and Brd4 Using Protein-Observed Fluorine NMR Uncovers New Bromodomain Probe Molecules. ACS Chem Biol. 2015 Oct 16;10(10):2246-56.