GSK137647A (GSK 137647) is a selective agonist of FFA4.

HDAC-inhibitory activity: For the enzyme assay, 10 μL of [3H]acetyl-labeled histones (25,000 cpm/10 μg) are added to 90 μL of the HDAC enzyme fraction extracted from 293T cells overexpressing HDAC1 or HDAC2 in the presence of increasing concentrations of Romidepsin, and the mixture is incubated at 37 °C for 15 minutes. The enzyme reaction is linear for at least 1 hour. The reaction is stopped by the addition of 10 μL of concentrated HCl. The released [3H]acetic acid is extracted with 1 mL of ethylacetate, and 0.9 mL of the solvent layer is taken into 5 mL of aqueous counting scintillant II solution for determination of radioactivity. The IC50 values are determined from at least three independent dose-response curves.