Ulixertinib hydrochloride (BVD-523 hydrochloride, VRT752271 hydrochloride) is a highly selective, ATP-competitive, and reversible covalent inhibitor of ERK1/2 kinases, with an IC50 of <0.3 nM against ERK2. It also reduces A375 cell proliferation with an IC50 of 180 nM and inhibits phosphorylated ERK (pERK) and the downstream kinase RSK (pRSK) in the A375 melanoma cell line, with IC50 values of 4.1 μM and 0.14 μM, respectively.