To assess whether covalent targeting of ERK by BI-78D3 can overcome acquired resistance of BRAF inhibitor-resistant cells, we used two previously reported melanoma cell lines exhibiting sensitivity (451 Lu-S and MEL 1617-S) and acquired resistance (451 Lu-R and MEL 1617-R) to SB-590885, as well as other BRAF inhibitors, such as PLX472015. Here, MAPK1 is linked to melanoma.