More recently, studies have identified activation of the parallel ERK5 signalling pathway as a driver of BRAFi/MEKi (Song et al., 2017) and ERK1/2i resistance (Benito-Jardón et al., 2019) in melanoma and also as a driver of adaptive resistance to ERK1/2 pathway inhibition in pancreatic ductal adenocarcinoma (PDAC) (Vaseva et al., 2018) (Figure 3). Here, MAPK3 is linked to melanoma.